Exposure apparatus

The present invention is used for transferring a mask pattern onto a photosensitive substrate in a lithography process for manufacturing a device such as a semiconductor element, an image pickup device (CCD or the like), a liquid crystal display element, or a thin film magnetic head. The present invention relates to an optical element used in a projection exposure apparatus using a liquid immersion method, and an exposure apparatus using the optical element.

When manufacturing a semiconductor element or the like, an image of a reticle pattern as a mask is transferred to each shot region on a wafer (or glass plate or the like) coated with a resist as a photosensitive substrate via a projection optical system. Projection exposure equipment is used. In the past, a step-and-repeat reduction projection type exposure device (stepper) was often used as a projection exposure device, but recently, a step-and-scan method in which a reticle and a wafer are synchronously scanned for exposure. Projection exposure equipment is also attracting attention.

The resolution of the projection optical system provided in the projection exposure apparatus increases as the exposure wavelength used becomes shorter and the numerical aperture of the projection optical system becomes larger. Therefore, as the integrated circuit becomes finer, the exposure wavelength used in the projection exposure apparatus is shortened year by year, and the numerical aperture of the projection optical system is also increasing. The current mainstream exposure wavelength is 248 nm for the KrF excimer laser, but 193 nm for the shorter wavelength ArF excimer laser has also been put into practical use.

By the way, as the wavelength of the exposure light is shortened, the glass material having a transmittance that can secure a sufficient amount of light for exposure while ensuring the desired imaging performance is limited. Therefore, between the lower surface of the projection optical system and the surface of the wafer. Is filled with water or a liquid such as an organic solvent, and the wavelength of the exposure light in the liquid becomes 1 / n times that in the air (n is the refractive index of the liquid, usually about 1.2 to 1.6). A liquid immersion type projection exposure apparatus for improving the resolution has been proposed (Japanese Patent Laid-Open No. 10-303114).

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 10-303114</text></patcit></p>

<p> When this immersion type projection exposure device is configured as a step-and-repeat type projection exposure device, the tip of the projection optical system in contact with the liquid is liquid because the projection optical system and the liquid are in contact with each other. There is a problem that the desired optical performance cannot be obtained because of the possibility of erosion.</p><p> Further, when the immersion type projection exposure apparatus is configured as a step-and-scan projection exposure apparatus, exposure is performed while moving the wafer, so that the projection optical system and the projection optical system are used even while the wafer is being moved. The wafer must be filled with a liquid, and since the projection optical system and the liquid are in contact with each other, the tip of the projection optical system in contact with the liquid is eroded by the liquid, and the desired optical performance can be obtained. There was a problem that there was no.</p><p> An object of the present invention is that when the immersion method is applied, the exposure beam and the exposure beam reflected light from the wafer are irradiated to the seal provided on the peripheral portion of the side surface of the transmission optical element on the substrate side of the projection optical system. It is to prevent the deterioration of members such as seals.</p>

<p> The present invention provides the following optical elements that solve the above problems, and an exposure apparatus using the following optical elements.</p><p> &lt;1&gt; An exposure device for illuminating a mask with an exposure beam and transferring the pattern of the mask onto a substrate via a projection optical system, which is a predetermined position between the surface of the substrate and the projection optical system. In the optical element used in the exposure apparatus in which a liquid is interposed, An optical element provided with a light-shielding film on the side surface of the transmissive optical element on the substrate side of the projection optical system.</p><p> &lt;2&gt; The optical element according to &lt;1&gt;, wherein the light-shielding film is formed of a metal film or a metal oxide film.</p><p> &lt;3&gt; The metal film is formed of at least one selected from the group consisting of Au, Pt, Ag, Ni, Ta, W, Pd, Mo, Ti and Cr, and the metal oxide film is formed of the metal oxide film. ZrO₂, HfO₂, TiO₂, Ta₂O₅, SiO and Cr₂O₃The optical element according to &lt;2&gt;, which is formed by at least one selected from the group consisting of.</p><p> According to the optical element according to any one of &lt;1&gt; to &lt;3&gt;, the light-shielding film is provided on the peripheral portion of the side surface (tapered surface) of the transmissive optical element on the substrate side of the projection optical system. It is possible to prevent the sealing member from being irradiated with the exposure beam and the light reflected from the exposure beam from the wafer, and it is possible to prevent deterioration of the sealing member.</p><p> &lt;4&gt; An exposure device for illuminating a mask with an exposure beam and transferring the pattern of the mask onto a substrate via a projection optical system, which is a predetermined position between the surface of the substrate and the projection optical system. In the exposure apparatus in which a liquid is interposed, An exposure apparatus provided with a light-shielding film formed on the side surface of a transmission optical element on the substrate side of the projection optical system.</p><p> &lt;5&gt; The exposure apparatus according to &lt;4&gt;, wherein the light-shielding film is formed of a metal film or a metal oxide film.</p><p> &lt;6&gt; The metal film is formed of at least one selected from the group consisting of Au, Pt, Ag, Ni, Ta, W, Pd, Mo, Ti and Cr, and the metal oxide film is formed of the metal oxide film. ZrO₂, HfO₂, TiO₂, Ta₂O₅, SiO and Cr₂O₃The exposure apparatus according to &lt;5&gt;, which is formed by at least one selected from the group consisting of.</p><p> According to the exposure apparatus according to any one of &lt;4&gt; to &lt;6&gt;, the light-shielding film is provided on the peripheral portion of the side surface (tapered surface) of the transmissive optical element on the substrate side of the projection optical system. the seal member exposure beamAndcan be exposure beam reflected from the beauty wafer prevented from being irradiated, it is possible to prevent the deterioration of the sealing member.</p>

<figref num="1">FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus used in the first embodiment.</figref><figref num="2">FIG. 2 is a diagram showing the configuration of the optical element of the first embodiment.</figref><figref num="3">FIG. 3 is a diagram showing the positional relationship between the tip of the optical element in the projection optical system shown in FIG. 1 and the discharge nozzle and the inflow nozzle for the X direction.</figref><figref num="4">FIG. 4 is a diagram showing the positional relationship between the tip of the optical element in the projection optical system shown in FIG. 1 and the discharge nozzle and the inflow nozzle for the Y direction.</figref><figref num="5">FIG. 5 is an enlarged view of a main part showing a state of supply and recovery of liquid between the optical element and the wafer W in the projection optical system shown in FIG.</figref><figref num="6">FIG. 6 is a diagram showing the configuration of the optical element of the third embodiment.</figref><figref num="7">FIG. 7 is a diagram showing the configuration of the optical element of the sixth embodiment.</figref><figref num="8">FIG. 8 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the sixth embodiment in the ArF excimer laser.</figref><figref num="9">FIG. 9 is a diagram showing the configuration of the optical element of the seventh embodiment.</figref><figref num="10">FIG. 10 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the seventh embodiment in the ArF excimer laser.</figref><figref num="11">FIG. 11 is a diagram showing the configuration of the optical element of the eighth embodiment.</figref><figref num="12">FIG. 12 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the eighth embodiment in the ArF excimer laser.</figref><figref num="13">FIG. 13 is a diagram showing the relationship between the reflectance and the emission angle θ in the ArF excimer laser of the optical element when the film thickness of the second layer is halved in the optical element of the eighth embodiment. ..</figref><figref num="14">FIG. 14 is a diagram showing the configuration of the optical element of the ninth embodiment.</figref><figref num="15">FIG. 15 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the ninth embodiment in the ArF excimer laser.</figref><figref num="16">FIG. 16 is a diagram showing the configuration of the optical element of the tenth embodiment.</figref><figref num="17">FIG. 17 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the tenth embodiment in the ArF excimer laser.</figref><figref num="18">FIG. 18 is a diagram showing the configuration of the optical element of the eleventh embodiment.</figref><figref num="19">FIG. 19 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the eleventh embodiment in the ArF excimer laser.</figref><figref num="20">FIG. 20 is a diagram showing the configuration of the optical element of the twelfth embodiment.</figref><figref num="21">FIG. 21 is a diagram showing the relationship between the reflectance and the emission angle of the optical element of the twelfth embodiment in the ArF excimer laser.</figref><figref num="22">FIG. 22 is a diagram showing a configuration of an optical member used in the fourteenth embodiment.</figref><figref num="23">FIG. 23 is a diagram showing the angular reflection characteristics of the optical contact interface of FIG. 22.</figref><figref num="24">FIG. 24 is a diagram showing a configuration of an optical member used in the fifteenth embodiment.</figref><figref num="25">FIG. 25 is a diagram showing the configuration of the optical element used in the 16th embodiment.</figref><figref num="26">FIG. 26 is a diagram conceptually showing the first step of the manufacturing process of the optical element 4 shown in FIG. 25.</figref><figref num="27">FIG. 27 is a diagram conceptually showing the second step of the manufacturing process of the optical element 4 shown in FIG. 25.</figref><figref num="28">FIG. 28 is a diagram conceptually showing a third step of the manufacturing process of the optical element 4 shown in FIG. 25.</figref><figref num="29">FIG. 29 is a diagram conceptually showing a fourth step of the manufacturing process of the optical element 4 shown in FIG. 25.</figref><figref num="30">FIG. 30 is a diagram showing a schematic configuration of the projection exposure apparatus used in the seventeenth embodiment.</figref><figref num="31">FIG. 31 is a diagram showing the positional relationship between the tip of the optical element in the projection optical system shown in FIG. 30 and the discharge nozzle and the inflow nozzle for the X direction.</figref><figref num="32">FIG. 32 is a diagram showing the positional relationship between the tip of the optical element in the projection optical system shown in FIG. 30 and the discharge nozzle and the inflow nozzle for the Y direction.</figref><figref num="33">FIG. 33 is a diagram showing a schematic configuration of the exposure apparatus according to the thirty-third embodiment.</figref><figref num="34">FIG. 34 is a diagram showing a configuration of an optical element according to the first embodiment.</figref><figref num="35">FIG. 35 is a diagram showing how light is reflected when it is incident on fluorite.</figref><figref num="36">FIG. 36 is a diagram showing the residual reflectance of fluorite when light is incident on the fluorite substrate.</figref><figref num="37">FIG. 37 is a diagram showing the configuration of the experimental apparatus according to the first embodiment.</figref><figref num="38">FIG. 38 is a diagram showing a configuration of an optical element according to a second embodiment.</figref><figref num="39">FIG. 39 is a diagram showing the configuration of the experimental apparatus according to Comparative Example 1.</figref><figref num="40">FIG. 40 is a diagram showing the measurement results of the steps measured after the experiments of the optical elements in Comparative Example 1, Example 1 and Example 2.</figref><figref num="41">FIG. 41 is a diagram showing a configuration of a transmission optical element according to the third embodiment.</figref><figref num="42">FIG. 42 is a diagram showing the configuration of the tester according to the third embodiment.</figref><figref num="43">FIG. 43 is a diagram showing the configuration of the transmission optical element according to the fourth embodiment.</figref><figref num="44">FIG. 44 is a diagram showing a configuration of a transmission optical element according to the fifth embodiment.</figref><figref num="45">FIG. 45 is a diagram showing a configuration of an optical element according to a sixth embodiment.</figref><figref num="46">FIG. 46 is a diagram showing a configuration of an optical element according to a seventh embodiment.</figref><figref num="47">FIG. 47 is a diagram showing the configuration of Sample 1 according to Example 6.</figref><figref num="48">FIG. 48 is a diagram showing the configuration of Sample 2 according to Example 7.</figref><figref num="49">FIG. 49 is a diagram showing the configuration of Sample 3 according to Reference Example 1.</figref><figref num="50">FIG. 50 is a diagram showing the configuration of the experimental apparatus according to Examples 6 to 7 and Reference Example 1.</figref><figref num="51">FIG. 51 is a diagram showing the experimental results in Examples 6 to 7 and Reference Example 1.</figref><figref num="52">FIG. 52 is a diagram showing the state of sample 3 after the experiment.</figref><figref num="53">FIG. 53 is a diagram showing a configuration of a transmission optical element according to the eighth embodiment.</figref><figref num="54">FIG. 54 is a diagram showing a configuration of a transmission optical element according to the tenth embodiment.</figref><figref num="55">FIG. 55 is a diagram showing a configuration of a transmission optical element according to the eleventh embodiment.</figref><figref num="56">FIG. 56 is a diagram showing a configuration of a transmission optical element according to Reference Example 2.</figref><figref num="57">FIG. 57 is a diagram showing an angular reflection characteristic when light is incident on the transmission optical element according to Example 10 and Reference Example 2 from the medium.</figref>

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] Hereinafter, the projection exposure apparatus according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a step-and-repeat projection exposure apparatus according to the first embodiment. Further, in the following description, the XYZ Cartesian coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ Cartesian coordinate system. The XYZ Cartesian coordinate system is set so that the X-axis and the Y-axis are parallel to the wafer W, and the Z-axis is set in the direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set to the vertically upward direction.

As shown in FIG. 1, the projection exposure apparatus according to this embodiment includes an ArF excimer laser light source as an exposure light source, and is an illumination optical system 1 composed of an optical integrator (homogenizer), a field diaphragm, a condenser lens, and the like. It has. The exposure light (exposure beam) IL composed of ultraviolet pulsed light having a wavelength of 193 nm emitted from the light source passes through the illumination optical system 1 and illuminates the pattern provided on the reticle (mask) R. The light that has passed through the reticle R passes through a telecentric projection optical system PL on both sides (or one side on the wafer W side) to a predetermined projection magnification β (for example, on the exposure region on the wafer (board) W coated with the photoresist). , Β is 1/4, 1/5, etc.) for reduced projection exposure.

The exposure light IL is KrF excimer laser light (wavelength 248 nm), F.₂Laser light (wavelength 157 nm), i-line of a mercury lamp (wavelength 365 nm), or the like may be used.

Further, the reticle R is held on the reticle stage RST, and the reticle stage RST incorporates a mechanism for finely moving the reticle R in the X direction, the Y direction and the rotation direction. The positions of the reticle stage RST in the X, Y, and rotation directions are measured and controlled in real time by a reticle laser interferometer (not shown).

Further, the wafer W is fixed on the Z stage 9 via a wafer holder (not shown). The Z stage 9 is fixed on the XY stage 10 that moves along the XY plane substantially parallel to the image plane of the projection optical system PL, and determines the focus position (position in the Z direction) and the inclination angle of the wafer W. Control. The positions of the Z stage 9 in the X direction, the Y direction, and the rotation direction are measured and controlled in real time by the wafer laser interferometer 13 using the moving mirror 12 located on the Z stage 9. Further, the XY stage 10 is mounted on the base 11 and controls the X direction, the Y direction and the rotation direction of the wafer W.

The main control system 14 provided in this projection exposure apparatus adjusts the positions of the reticle R in the X direction, the Y direction, and the rotation direction based on the measured values measured by the reticle laser interferometer. That is, the main control system 14 transmits a control signal to the mechanism incorporated in the reticle stage RST, and finely moves the reticle stage RST to adjust the position of the reticle R.

Further, the main control system 14 adjusts the focus position (position in the Z direction) and the inclination angle of the wafer W in order to align the surface on the wafer W with the image plane of the projection optical system PL by the autofocus method and the autoleveling method. To do. That is, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the Z stage 9 by the wafer stage drive system 15 to adjust the focus position and the inclination angle of the wafer W. Further, the main control system 14 adjusts the positions of the wafer W in the X direction, the Y direction, and the rotation direction based on the measured values measured by the wafer laser interferometer 13. That is, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to adjust the positions of the wafer W in the X, Y, and rotation directions. ..

At the time of exposure, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 by the wafer stage drive system 15 to sequentially step-move each shot region on the wafer W to the exposure position. .. That is, the operation of exposing the pattern image of the reticle R on the wafer W is repeated by the step-and-repeat method.

In this projection exposure apparatus, an immersion method is applied in order to substantially shorten the exposure wavelength and improve the resolution. Here, in the immersion type projection exposure apparatus to which the immersion method is applied, at least while the pattern image of the reticle R is transferred onto the wafer W, the surface of the wafer W and the wafer W side of the projection optical system PL A predetermined liquid 7 is filled between the transparent optical element 4 and the transparent optical element 4. The projection optical system PL includes a lens barrel 3 that houses a plurality of optical elements formed of quartz or fluorite that constitute the projection optical system PL. In this projection optical system PL, the transmission optical element 4 on the wafer W side is formed of fluorite, and the surface of the transmission optical element 4 (tip portion 4A and taper surface 4B on the wafer W side (see FIG. 2)). Only configured to contact liquid 7. As a result, corrosion of the lens barrel 3 made of metal and the like are prevented.

Here, the base material of the transmission optical element 4 shown in FIG. 2 is fluorite, and the crystal orientation of the film-forming surface of the fluorite is the (111) plane. Further, magnesium fluoride (MgF) is used as a dissolution prevention film on the tip 4A of the transmission optical element 4 on the wafer W side, that is, the portion through which the exposure light is transmitted.₂) Membrane F1 and silicon dioxide (SiO)₂) Film F2 is formed by vacuum deposition method, and further silicon dioxide (SiO)₂) The film F3 is formed by a wet film forming method.

Further, on the tapered surface 4B of the transmission optical element 4, that is, the portion where the exposure light is not transmitted, a tantalum (Ta) film F5 (F4) is formed as a metal dissolution prevention film (also serving as an adhesion strengthening film) by a sputtering method. ing. Further, on the surface of the metal dissolution prevention film (dissolution prevention film) F5, silicon dioxide (SiO) is used as a metal dissolution prevention film protection film (dissolution prevention film protection film) for protecting the metal dissolution prevention film.₂) Membrane F6 is silicon dioxide (SiO)₂) The film is formed by the wet film forming method at the same time as the film F3. Here, the solubility of the metal dissolution prevention film (dissolution prevention film) F5 formed on the tapered surface 4B of the transmission optical element 4 in pure water is 2 ppt or less, and the packing density is 95% or more. Further, the average reflectance of the anti-melting films F1 to F3 formed on the tip portion 4A of the transmission optical element 4 when the emission angle of the exposure beam is 50 degrees is 2% or less.

The transmission optical element 4 shown in FIG. 2 is manufactured as follows, for example. (i) A metal anti-dissolution film formed on the tapered surface 4B of the transmissive optical element 4, that is, the portion where the exposure light does not pass, on the tip portion 4A on the wafer W side of the transmissive optical element 4, that is, the portion where the exposure light is transmitted. Attach the mask sticker so that F5 does not stick. (ii) A tantalum (Ta) film of 200 nm is formed on the tapered surface 4B of the transmission optical element 4 by a sputtering method to form a metal dissolution prevention film (also serving as an adhesion strengthening film) F5. (iii) Remove the mask sticker attached to the tip portion 4A of the transmissive optical element 4 on the wafer W side. (iv) Magnesium fluoride (MgF) was applied to the tip 4A of the transmission optical element 4 on the wafer W side using a vacuum deposition method.₂) Membrane F1 at 15 nm, silicon dioxide (SiO)₂) A film F2 is formed at 300 nm. (v) Tantal (Ta) film F5, which is a metal dissolution prevention film formed on the tapered surface 4B of the transmission optical element 4, and silicon dioxide (SiO) film formed on the tip 4A of the transmission optical element 4 on the wafer W side.₂) Silicon dioxide (SiO) on film F2 using a wet film formation method₂) Films F3 and F6 are simultaneously formed at 130 nm and heat-sintered at 160 ° C. (vi) Silicon dioxide (SiO) formed on the tantalum (Ta) film F5, which is a metal dissolution prevention film, by a wet film formation method.₂) Membrane F6 functions as a metal anti-dissolution film protective film for protecting the metal anti-dissolution film.

Further, as the liquid 7, pure water that can be easily obtained in a large amount at a semiconductor manufacturing factory or the like is used. Since pure water has an extremely low content of impurities, it can be expected to have an action of cleaning the surface of the wafer W.

FIG. 3 shows two pairs of the tip 4A and the tapered surface 4B on the wafer W side and the wafer W of the transmission optical element 4 of the projection optical system PL and the tip 4A and the taper surface 4B on the wafer W side sandwiched in the X direction. It is a figure which shows the positional relationship with the discharge nozzle and the inflow nozzle. Further, FIG. 4 shows two pairs of discharges that sandwich the tip 4A and the tapered surface 4B on the wafer W side of the transmission optical element 4 of the projection optical system PL and the tip 4A and the taper surface 4B on the wafer W side in the Y direction. It is a figure which shows the positional relationship with a nozzle and an inflow nozzle. The projection exposure apparatus according to this embodiment includes a liquid supply device 5 that controls the supply of the liquid 7 and a liquid recovery device 6 that controls the discharge of the liquid 7.

The liquid supply device 5 includes a tank for the liquid 7 (not shown), a pressurizing pump (not shown), a temperature control device (not shown), and the like. Further, as shown in FIG. 3, the liquid supply device 5 is supplied with a discharge nozzle 21a having a tip portion 4A on the wafer W side and a thin tip portion on the + X direction side of the tapered surface 4B via the supply pipe 21. A discharge nozzle 22a having a thin tip portion 4A on the wafer W side and a thin tip portion on the -X direction side of the tapered surface 4B is connected via the pipe 22. Further, as shown in FIG. 4, the liquid supply device 5 is supplied with a discharge nozzle 27a having a tip portion 4A on the wafer W side and a thin tip portion on the + Y direction side of the tapered surface 4B via the supply pipe 27. A discharge nozzle 28a having a thin tip portion 4A on the wafer W side and a thin tip portion on the -Y direction side of the tapered surface 4B is connected via the pipe 28. The liquid supply device 5 adjusts the temperature of the liquid 7 by a temperature control device, and from at least one discharge nozzle in the discharge nozzles 21a, 22a, 27a, 28a, at least in the supply pipes 21, 22, 27, 28. The temperature-controlled liquid 7 is supplied onto the wafer W via one supply pipe. The temperature of the liquid 7 is set by the temperature control device to be about the same as the temperature in the chamber in which the projection exposure device according to this embodiment is housed, for example.

The liquid recovery device 6 includes a tank for liquid 7 (not shown), a suction pump (not shown), and the like. Further, in the liquid recovery device 6, as shown in FIG. 3, inflow nozzles 23a and 23b having a wide tip portion on the -X direction side of the tapered surface 4B via the recovery pipe 23 are tapered via the recovery pipe 24. Inflow nozzles 24a and 24b having a wide tip on the + X direction side of the surface 4B are connected. The inflow nozzles 23a, 23b, 24a, and 24b are arranged so as to pass through the center of the tip portion 4A on the wafer W side and open in a fan shape with respect to an axis parallel to the X axis. Further, in the liquid recovery device 6, as shown in FIG. 4, inflow nozzles 29a and 29b having a wide tip portion on the -Y direction side of the tapered surface 4B via the recovery pipe 29 are tapered via the recovery pipe 30. Inflow nozzles 30a and 30b having a wide tip on the + Y direction side of the surface 4B are connected. The inflow nozzles 29a, 29b, 30a, and 30b are arranged in a fan shape with respect to an axis parallel to the Y axis, passing through the center of the tip portion 4A on the wafer W side.

The liquid recovery device 6 has at least one recovery pipe in the recovery pipes 23, 24, 29, 30 from at least one inflow nozzle in the inflow nozzles 23a and 23b, 24a and 24b, 29a and 29b, 30a and 30b. The liquid 7 is recovered from the wafer W through the wafer W.

Next, a method of supplying and recovering the liquid 7 will be described. In FIG. 3, when the wafer W is stepped in the direction of the arrow 25A (-X direction) shown by the solid line, the liquid supply device 5 uses the wafer W of the transmission optical element 4 via the supply pipe 21 and the discharge nozzle 21a. The liquid 7 is supplied between the tip portion 4A and the tapered surface 4B on the side and the wafer W. The liquid recovery device 6 is a liquid 7 supplied from above the wafer W via the recovery pipe 23 and the inflow nozzles 23a and 23b by the liquid supply device 5 between the tip portion 4A and the tapered surface 4B on the wafer W side and the wafer W. To collect. In this case, the liquid 7 flows on the wafer W in the direction of the arrow 25B (-X direction), and the space between the wafer W and the transmission optical element 4 is stably filled with the liquid 7.

On the other hand, in FIG. 3, when the wafer W is stepped in the direction of the arrow 26A (+ X direction) indicated by the chain line, the liquid supply device 5 uses the transmission optical element 4 via the supply pipe 22 and the discharge nozzle 22a. The liquid 7 is supplied between the tip portion 4A and the tapered surface 4B on the wafer W side and the wafer W. The liquid recovery device 6 recovers the liquid 7 supplied between the tip portion 4A and the tapered surface 4B on the wafer W side and the wafer W by the liquid supply device 5 via the recovery pipe 24 and the inflow nozzles 24a and 24b. .. In this case, the liquid 7 flows on the wafer W in the direction of arrow 26B (+ X direction), and the space between the wafer W and the transmission optical element 4 is stably filled with the liquid 7.

Further, when the wafer W is stepped in the Y direction, the liquid 7 is supplied and recovered from the Y direction. That is, in FIG. 4, when the wafer W is stepped in the direction of the arrow 31A (-Y direction) shown by the solid line, the liquid supply device 5 supplies the liquid 7 via the supply pipe 27 and the discharge nozzle 27a. To do. The liquid recovery device 6 recovers the liquid 7 supplied between the tip portion 4A and the tapered surface 4B on the wafer W side and the wafer W by the liquid supply device 5 via the recovery pipe 29 and the inflow nozzles 29a and 29b. .. In this case, the liquid 7 flows in the direction of arrow 31B (-Y direction) on the exposed region, and the space between the wafer W and the transmission optical element 4 is stably filled with the liquid 7.

Further, when the wafer W is stepped in the + Y direction, the liquid supply device 5 supplies the liquid 7 via the supply pipe 28 and the discharge nozzle 28a. The liquid recovery device 6 recovers the liquid 7 supplied between the tip portion 4A on the wafer W side and the wafer W by the liquid supply device 5 via the recovery pipe 30 and the inflow nozzles 30a and 30b. In this case, the liquid 7 flows in the + Y direction on the exposed region, and the space between the wafer W and the transmission optical element 4 is stably filled with the liquid 7.

In addition to the nozzle for supplying and collecting the liquid 7 from the X direction or the Y direction, for example, a nozzle for supplying and collecting the liquid 7 from an oblique direction may be provided.

Next, a method of controlling the supply amount and the recovery amount of the liquid 7 will be described. FIG. 5 is a diagram showing a state in which the liquid 7 is supplied and recovered between the optical element 4 constituting the projection optical system PL and the wafer W. As shown in FIG. 5, when the wafer W is moving in the direction of arrow 25A (-X direction), the liquid 7 supplied from the discharge nozzle 21a flows in the direction of arrow 25B (-X direction). It is collected by the inflow nozzles 23a and 23b. In order to keep the amount of liquid 7 filled between the optical element 4 and the wafer W constant even while the wafer W is moving, the amount of liquid 7 supplied Vi (m).³/ s) and recovery amount Vo (m)³Equal to / s). Further, the supply amount Vi and the recovery amount Vo of the liquid 7 are adjusted based on the moving speed v of the XY stage 10 (wafer W). That is, the supply amount Vi and the recovery amount Vo of the liquid 7 are calculated based on the mathematical formula 1. (Formula 1) Vi = Vo = D v d Here, D is the diameter (m) of the tip 4A of the optical element 4, v is the moving speed of the XY stage 10 (m / s), and d is the working distance of the projection optical system PL (working distance). Distance) (m). Since the speed v when stepping through the XY stage 10 is set by the main control system 14 and D and d are input in advance, the supply amount Vi and recovery amount Vo of the liquid 7 are calculated based on Equation 1. By adjusting, the liquid 7 is constantly filled between the optical element 4 and the wafer W.

The working distance d of the projection optical system PL is preferably as narrow as possible in order for the liquid 7 to stably exist between the optical element 4 and the wafer W. For example, the working distance d of the projection optical system PL is set to about 2 mm.

According to the projection exposure apparatus according to the first embodiment, since the dissolution prevention film is formed on the surface of the optical element, the dissolution of the optical element can be prevented. Therefore, since the optical element is not dissolved by the liquid filled between the tip of the projection optical system and the substrate, it is not necessary to replace the optical element frequently, and the high throughput of the exposure apparatus can be maintained. it can. Further, it is not necessary to stop the operation of the exposure apparatus in order to replace the melted optical element, and the final product can be efficiently produced. Furthermore, since the optical element is not dissolved by the liquid, the optical performance of the projection optical system can be maintained, so that the quality of the final product produced can be stabilized and the exposure can be continued in the optimum state. Can be done.

Further, according to the projection exposure apparatus according to the first embodiment, a metal dissolution prevention film that also serves as an adhesion strengthening film is formed on the tapered surface 4B of the transmission optical element 4 on the wafer W side of the projection optical system PL. Therefore, the metal dissolution prevention film can be brought into close contact with the transmission optical element 4. In addition, silicon dioxide (SiO) on the surface of the metal dissolution prevention film.₂) Since the film is formed, it is possible to prevent damage to the metal dissolution prevention film which is soft and has low scratch resistance, and it is possible to protect the metal dissolution prevention film. Therefore, it is possible to prevent the liquid 7 interposed between the surface of the wafer W and the projection optical system PL from penetrating and eroding into the transmission optical element 4, and the optical performance of the projection optical system PL can be maintained. .. Further, since the transmission optical element 4 is not dissolved by the liquid 7, the performance of the exposure apparatus can be maintained. Further, since it is not necessary to replace the transmission optical element 4 frequently, the throughput of the projection exposure apparatus can be maintained high.

Further, since the metal dissolution prevention film is formed on the tapered surface 4B of the transmission optical element 4, that is, the portion through which the exposure light IL does not pass, the metal dissolution prevention film formed on the surface of the transmission optical element 4 is exposed. The exposure can be continued in the optimum state without blocking the optical IL.

Further, the refractive index n of pure water with respect to the exposure light having a wavelength of about 200 nm is about 1.44, and the ArF excimer laser light having a wavelength of 193 nm is shortened to 1 / n, that is, 134 nm on the wafer W. High resolution can be obtained. Furthermore, since the depth of focus is magnified about n times, that is, about 1.44 times that in air, the aperture of the projection optical system PL is required if the same depth of focus as when used in air can be secured. The number can be increased further, which also improves the resolution.

Further, according to the projection exposure apparatus according to the first embodiment, since the wafer is provided with two pairs of discharge nozzles and inflow nozzles that are inverted in the X direction and the Y direction, the wafer is placed in the + X direction and -X. Even when moving in the direction, + Y direction, or -Y direction, the space between the wafer and the optical element can be stably filled with the liquid.

Further, since the liquid flows on the wafer, even if foreign matter is attached to the wafer, the foreign matter can be washed away by the liquid. Further, since the liquid is adjusted to a predetermined temperature by the liquid supply device, the temperature of the wafer surface is also constant, and it is possible to prevent a decrease in stacking accuracy due to thermal expansion of the wafer that occurs during exposure. Therefore, even when there is a time difference between alignment and exposure as in the case of EGA (enhanced global alignment) alignment, it is possible to prevent a decrease in overlay accuracy due to thermal expansion of the wafer.

Further, according to the projection exposure apparatus according to the first embodiment, since the liquid flows in the same direction as the wafer is moved, the liquid that has absorbed foreign matter and heat is transmitted directly under the surface of the transmission optical element. It can be recovered by a liquid recovery device without staying on the exposed region of.

In each of the above-described embodiments, magnesium fluoride (MgF) is used as the anti-dissolution film.₂) And silicon dioxide (SiO)₂) Was used, but instead of this, lanthanum fluoride (LaF)₃), Strontium fluoride (SrF)₂), Yttrium fluoride (YF)₃), Ruthenium Fluoride (LuF)₃), Hafnium Fluoride (HfF)₄), Neodymium Fluoride (NdF)₃), Gadolinium Fluoride (GdF)₃), Itteribium Fluoride (YbF)₃), Dysprosium Fluoride (DyF)₃), Aluminum fluoride (AlF₃), Cliolite (Na₃AlF₆), Thiorite (5NaF / 3AlF₃), Aluminum oxide (Al₂O₃), Silicon dioxide (SiO)₂), Titanium oxide (TiO₂), Magnesium oxide (MgO), Hafnium oxide (HfO)₂), Chromium oxide (Cr₂O₃), Zircon oxide (ZrO)₂), Tantalum pentoxide (Ta₂O₅) And niobium pentoxide (Nb)₂O₅) May be used as an anti-dissolution film.

Further, in each of the above-described embodiments, magnesium fluoride (MgF) is produced by a vacuum vapor deposition method.₂) And silicon dioxide (SiO)₂) Was formed on the optical element, but instead of this, the ion beam assisted vapor deposition method, the gas cluster ion beam assisted vapor deposition method, the ion plating method, the ion beam sputtering method, the magnetron sputtering method, and the bias The film may be formed by at least one film forming method among a sputtering method, an ECR sputtering method, an RF sputtering method, a thermal CVD method, a plasma CVD method and an optical CVD method.

When fluoride is formed as a dissolution prevention film for an optical element, the optimum film forming method includes a vacuum vapor deposition method, an ion beam assisted vapor deposition method, a gas cluster ion beam assisted vapor deposition method, and an ion plating method. .. However, magnesium fluoride (MgF)₂) And yttrium fluoride (YF)₃) May be formed by a sputtering method. Further, when forming an oxide as a dissolution prevention film for an optical element, all the above-mentioned film forming methods can be used.

In addition, the film-forming anti-dissolution film, especially lanthanum fluoride (LaF)₃) Is heteroepitaxially grown by forming a film on the film-forming surface when fluorite having a crystal orientation of the (111) plane is used as the base material of the optical element. In this case, the film-formed anti-dissolution film has a crystal structure that is extremely dense and has very few defects.

Further, in the projection exposure apparatus according to the first embodiment, a metal film composed of a film formed of tungsten (Ta) was used as the metal anti-dissolution film (anti-dissolution film), but gold (Au) was used. ), Platinum (Pt), Silver (Ag), Nickel (Ni), Tungsten (W), Palladium (Pd), Molybdenum (Mo), Titanium (Ti) and Chromium (Cr). A metal film composed of a film may be used.

Further, in the projection exposure apparatus according to the first embodiment, an adhesion strengthening film composed of a film formed of tantalum (Ta) was used, but it is composed of a film formed of chromium (Cr). You may use the adhesive force strengthening film.

Further, in the projection exposure apparatus according to the first embodiment, silicon dioxide (SiO).₂A metal anti-dissolution film protective film (anti-dissolution film protective film) composed of a film formed by) was used, but yttrium oxide (Y)₂O₃), Neodymium Fluoride (Nd₂F₃), Chromium oxide (Cr₂O₃), Tantalum pentoxide (Ta₂O₅), Niobium pentoxide (Nb)₂O₅), Titanium dioxide (TiO₂), Zirconium dioxide (ZrO)₂), Hafnium dioxide (HfO)₂) And lanthanum oxide (La₂O₃), A metal anti-dissolution film protective film composed of a film formed by at least one of them may be used. That is, since a metal anti-dissolution film protective film can be selected, the base material of the transmission optical element, the environment in which the transmission optical element is installed, and the liquid intervening between the surface of the base material and the projection optical system. The optimum metal anti-dissolution film protective film (anti-dissolution film protective film) can be selected based on the type and the like.

Further, in the projection exposure apparatus according to the first embodiment, silicon dioxide (SiO) which also serves as a dissolution prevention film and a metal dissolution prevention film protective film.₂) The film is formed by a wet film forming method, but it may be formed by a dry film forming method such as a sputtering method.

Further, on the tapered surface of the transmission optical element according to the first embodiment, a metal dissolution prevention film (which also serves as an adhesion strengthening film) and a metal dissolution prevention film protective film are formed. Only a metal anti-dissolution film (anti-dissolution film) may be formed. Further, the adhesion strengthening film and the metal dissolution prevention film are separated to form an adhesion reinforcement film and a metal dissolution prevention film, or an adhesion reinforcement film and a metal dissolution prevention film and a metal dissolution prevention film protective film. You may.

Further, in the projection exposure apparatus according to the first embodiment, the transmission optical element 4 on the wafer W side is formed of fluorite, and an adhesion strengthening film and a metal dissolution prevention film (a metal dissolution prevention film) are formed on the tapered surface thereof. Anti-dissolution film) and metal anti-dissolution film protective film (anti-dissolution film protective film) are formed. The transmission optical element 4 on the wafer W side is formed of quartz glass, and these films are formed on the tapered surface thereof. May be formed.

Further, in the above-described embodiment, the space between the surface of the wafer and the optical element formed by the fluorite on the wafer side of the projection optical system is filled with a liquid, but the surface of the wafer and the wafer side of the projection optical system are filled. A liquid may be interposed in a part between the optical element formed of the fluorite.

Further, in the above-described embodiment, pure water is used as the liquid 7, but the liquid is not limited to pure water, has transparency to exposure light, has a high refractive index as much as possible, and has a projection optical system or a wafer surface. It is also possible to use a photoresist that is stable to the photoresist applied to (for example, cedar oil, etc.).

[Embodiment 2] Magnesium fluoride (MgF) as a dissolution-preventing film composed of a monolayer film at the tip 4A of the optical element 4, that is, the portion in contact with the liquid 7.₂) Was formed by a vacuum vapor deposition method, and the projection exposure apparatus was configured in the same manner as in the first embodiment.

According to the projection exposure apparatus according to the second embodiment, since the dissolution prevention film formed of the monolayer film is formed on the surface of the optical element, the dissolution of the optical element can be prevented. Further, since the interface can be reduced as compared with the multilayer film, the adverse effect of the chemical reaction that may occur when the liquid invades from the interface of the protective layer as the dissolution prevention film can be suppressed as much as possible. In addition, the film can be easily formed as compared with the case where a dissolution prevention film composed of a multilayer film is formed.

Further, when the surface of the optical element is immersed in a liquid, a single-layer dissolution prevention film is formed so that the refractive index of the optical element becomes the same as or lower than the refractive index of the liquid, thereby forming a multi-layer structure. It is possible to obtain the same optical performance as the filmed optical element.

[Embodiment 3] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 was changed as shown in FIG. 6 and as follows. (i) Magnesium fluoride (MgF) composed of a monolayer film at the tip 4A of the transmission optical element 4 on the wafer W side, that is, the portion through which the exposure light is transmitted.₂) The film F1 is formed by the vacuum deposition method. (ii) A tantalum (Ta) film is formed as an adhesion strengthening film F4 on the tapered surface 4B of the transmission optical element 4, that is, a portion through which the exposure light is not transmitted, by a sputtering method. The adhesion strengthening film F4 improves the adhesion between the tapered surface 4B of the transmission optical element 4 and the metal dissolution prevention film (dissolution prevention film) F5 described later. (iii) On the surface of the adhesion strengthening film F4, a metal film composed of gold (Au) as a metal dissolution prevention film (dissolution prevention film) F5 for preventing dissolution in the liquid 7 is formed by a sputtering method. The film is formed with a thickness of 150 nm. (iv) On the surface of the metal anti-dissolution film (anti-dissolution film) F5, as the metal anti-dissolution film protective film (anti-dissolution film protective film) F6 for protecting the metal anti-dissolution film (anti-dissolution film). Silicon dioxide (SiO)₂) The film is formed by the sputtering method. Here, the solubility of the metal dissolution prevention film (dissolution prevention film) F5 formed on the tapered surface 4B of the transmission optical element 4 in pure water is 2 ppt or less, and the packing density is 95% or more.

According to the projection exposure apparatus according to the third embodiment, a metal film is formed on the surface of the adhesion strengthening film formed on the tapered surface 4B of the transmission optical element 4 on the wafer W side of the projection optical system PL. Since it is a film, the metal film can be brought into close contact with the transmission optical element 4. In addition, silicon dioxide (SiO) on the surface of the metal film₂) Since the film is formed, it is possible to prevent damage to the metal film which is soft and has low scratch resistance, and it is possible to protect the metal film. Therefore, it is possible to prevent the liquid 7 interposed between the surface of the wafer W and the projection optical system PL from penetrating and eroding into the transmission optical element 4, and the optical performance of the projection optical system PL can be maintained. .. Further, since the transmission optical element 4 is not dissolved by the liquid 7, the performance of the projection exposure apparatus can be maintained. Further, since it is not necessary to replace the transmission optical element 4 frequently, the throughput of the projection exposure apparatus can be maintained high.

[Embodiment 4] Magnesium fluoride (MgF) as a dissolution prevention film on the tip portion 4A and side surface portion (tapered portion) 4B of the optical element 4, that is, the portion in contact with the liquid 7.₂) Was formed, and the projection exposure apparatus was configured in the same manner as in the first embodiment.

According to the projection exposure apparatus according to the fourth embodiment, since the dissolution prevention film is formed on the surface of the optical element on the substrate side and the side surface of the optical element, it is possible to prevent the optical element from melting. .. Further, since a dissolution prevention film using the same material is formed on the surface of the optical element on the substrate side and the side surface of the optical element, the dissolution prevention film can be formed at one time by a simple process. A dissolution prevention film can be formed.

[Embodiment 5] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 was changed as follows. (i) Silicon dioxide (SiO) is used as the first film on the tip 4A of the transmissive optical element 4 on the wafer W side, that is, the portion through which the exposure light is transmitted.₂) The film is formed by the sputtering method, which is a dry film forming method. (ii) On the surface of the first film, silicon dioxide (SiO) as the second film₂) The film is formed by spin coating, which is a wet film forming method. (iii) The tapered surface 4B of the transmissive optical element 4, that is, the portion through which the exposure light does not pass, is polished with a grindstone of, for example, # 2000 in order to increase the roughness and surface area of the surface, and by polishing with the grindstone. Silicon dioxide (SiO) is used as an oxide dissolution prevention film on the surface-treated tapered surface 4B.₂) The film is formed by spin coating, which is a wet film forming method.

According to the projection exposure apparatus according to the fifth embodiment, silicon dioxide (SiO) is used as a first film on the tip of the transmission optical element on the wafer side of the projection optical system on the wafer W side.₂) The film is formed by the sputtering method. Further, on the surface of the first film, silicon dioxide (SiO) is used as the second film.₂) The film is formed by spin coating. Therefore, the first film can be brought into close contact with the transmission optical element formed of fluorite, and the first film can function as an adhesion strengthening layer for bringing the transmission optical element and the second film into close contact with each other. it can.

Further, since the second film is formed by a wet film forming method characterized by high homogeneity and high embedding property in pores, the second film enters the pores of the first film and becomes vacant. Therefore, it is possible to prevent the permeation and erosion of the liquid interposed between the wafer surface and the projection optical system into the transmission optical element, and the optical performance of the projection optical system can be maintained. Further, the first film and the second film are made of silicon dioxide (SiO).₂) Because it is a film, the bonding force between the first film formed by the sputtering method and the second film formed by spin coating is strengthened, and the first film and the second film are made stronger. Can be brought into close contact with. Therefore, the performance of the exposure apparatus can be maintained because the first film and the second film are not separated from the transmission optical element and the transmission optical element is not dissolved by the liquid. Further, since it is not necessary to frequently replace the transmission optical element, the throughput of the exposure apparatus can be maintained high.

Further, the tapered surface of the transmission optical element on the most wafer side of the projection optical system is polished with a grindstone of, for example, # 2000 in order to increase the roughness and surface area of the surface, and the tapered surface is coated with an oxide dissolution prevention film. As silicon dioxide (SiO)₂) The film is formed by spin coating. Since the oxide dissolution prevention film is formed by a wet film forming method characterized by high homogeneity and high embedding property in pores, it is possible to prevent the permeation and erosion of the liquid into the transmission optical element, and the projection can be performed. The optical performance of the optical system can be maintained. Therefore, since the transmission optical element is not dissolved by the liquid, the performance of the exposure apparatus can be maintained. Further, since it is not necessary to frequently replace the transmission optical element, the throughput of the exposure apparatus can be maintained high.

In the projection exposure apparatus according to the fifth embodiment, silicon dioxide is used as the first film by a dry film forming method on the tip portion 4A of the transmission optical element 4 on the wafer W side, that is, the portion through which the exposure light is transmitted. (SiO₂) Film is formed, and silicon dioxide (SiO) is used as the second film on the surface of the first film by a wet film formation method.₂) A film is formed, but silicon dioxide (SiO) is used as an oxide dissolution prevention film only by the wet film formation method on the tip 4A of the transmission optical element 4 on the wafer side.₂) A film may be formed. In this case, in order to improve the adhesion between the transmission optical element 4 and the oxide dissolution prevention film, the tip portion 4A of the transmission optical element 4 is subjected to surface treatment to the extent that the optical performance of the projection optical system PL is not deteriorated. .. That is, the surface of the tip portion 4A is polished with, for example, a # 2000 grindstone to increase the roughness and surface area of the tip portion 4A.

Further, in the projection exposure apparatus according to the fifth embodiment, silicon dioxide (SiO) is used as an oxide dissolution prevention film only on the tapered surface 4B of the transmission optical element 4, that is, the portion where the exposure light is not transmitted, by a wet film forming method only.₂) A film is formed, but silicon dioxide (SiO) is used as the first film on the tapered surface 4B by the dry film forming method.₂) Film is formed, and silicon dioxide (SiO) is used as the second film on the surface of the first film by a wet film formation method.₂) A film may be formed.

[Embodiment 6] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

That is, FIG. 7 is a diagram showing a configuration of an optical element used in the sixth embodiment of the present invention. Here, the optical element 4 is composed of an optical substrate 101 and a multilayer film 100. Fluorite was used for the optical substrate 101. Further, the multilayer film 100 is formed from the optical substrate 101 to the first layer 102 in order of lanthanum fluoride (hereinafter, LaF).₃), Magnesium fluoride on the second layer 103 (MgF₂), Aluminum oxide on the third layer 104 (hereinafter, Al₂O₃), Silicon oxide on the 4th layer 105 (hereinafter, SiO₂) Is formed into a four-layer structure. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

4th layer (SiO)₂) 105 and 3rd layer (Al₂O₃) The solubility of 104 in water is the lower limit of 1.0 × 10 of the measuring instrument.^-7Indicates g / 100 g of water. Therefore, the 4th layer (SiO)₂) 105 and 3rd layer (Al₂O₃) 104 is a substance that is insoluble in water, and the film formed by these substances has a protective function against water.

Here, the film forming method was a vacuum vapor deposition method. The film forming method is not limited to this method, and may be various sputtering methods, an ion beam assist method, or an ion plating method capable of producing a dense structure.

1st layer (LaF₃) 102, 2nd layer (MgF)₂) 103, 3rd layer (Al₂O₃) 104th and 4th layers (SiO)₂Table 1 shows the optical film thickness with the refractive index of 105 and λ as the design main wavelength.

<tables num="1"><img file="JP4771300B2_D0001.tif" /></tables>

As shown in Table 1, the refractive indexes of the first layer 102 and the third layer 104, which are the odd-numbered layers, are higher than the refractive indexes of the adjacent fluorite substrates 101, the second layer 103, and the fourth layer 105. I understand. By forming the multilayer film 100 on the optical substrate 101 in the order shown in Table 1, the multilayer film 100 as a whole can have an antireflection function.

FIG. 8 is a diagram showing the angular reflection characteristics of the optical element used in the sixth embodiment of the present invention at a wavelength of 193 nm. Here, an ArF (wavelength 193 nm) excimer laser was used. As is clear from FIG. 8, the average reflectance Ra of the S-polarized light Rs and the P-polarized light Rp due to the incident light 20 is about 0.3% or less even at the emission angle θ = 40 degrees, and the emission angle θ = 50 degrees. It is about 0.5% or less, showing very good characteristics and can be used sufficiently.

[Embodiment 7] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 9 is a diagram showing the configuration of the optical element 4 of the present invention. The optical element 4 is composed of an optical substrate 101 and a multilayer film 100. The multilayer film 100 is formed on the optical substrate 101, and the first layer 102 is lanthanum fluoride (hereinafter, LaF).₃), Magnesium fluoride on the second layer 103 (MgF₂), Aluminum oxide on the third layer 104 (hereinafter, Al₂O₃) Is formed into a three-layer structure. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

1st layer (LaF₃) 102, 2nd layer (MgF)₂) 103, 3rd layer (Al₂O₃Table 2 shows the optical film thickness with the refractive index of 104 and λ as the design main wavelength.

<tables num="2"><img file="JP4771300B2_D0002.tif" /></tables>

As shown in Table 2, LaF of the first layer 102₃The refractive index of is MgF of the adjacent optical substrate 101 and the second layer 103.₂It can be seen that it is higher than the refractive index of. By setting the refractive index in such an arrangement, the multilayer film 100 as a whole can have an antireflection function.

FIG. 10 is a diagram showing an angular reflection characteristic at a wavelength of 193 nm of the optical element used in the seventh embodiment of the present invention. Here, an ArF (wavelength 193 nm) excimer laser was used. As is clear from FIG. 10, the average reflectance Ra of the S-polarized light Rs and the P-polarized light Rp due to the incident light 20 is about 0.3% or less even at the emission angle θ = 40 degrees, and the emission angle θ = 50 degrees. It is about 0.8% or less, showing very good characteristics and can be used sufficiently.

[Embodiment 8] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 11 is a diagram showing the configuration of the optical element 4 of the present invention. The optical element 4 is composed of an optical substrate 101 and a multilayer film 100. The multilayer film 100 is formed on the optical substrate 101, and the first layer 102 is lanthanum fluoride (hereinafter, LaF).₃), Magnesium fluoride on the second layer 103 (MgF₂) Is formed into a two-layer structure. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

1st layer (LaF₃) 102, 2nd layer (MgF)₂Table 3 shows the optical film thickness with the refractive index of 103 and λ as the design main wavelength.

<tables num="3"><img file="JP4771300B2_D0003.tif" /></tables>

As shown in Table 3, the refractive index of the first layer 102 is the MgF of the adjacent optical substrate 101 and the second layer 103.₂It can be seen that it is higher than the refractive index of. By forming the multilayer film 100 on the optical substrate 101 in the order shown in Table 1, the multilayer film 100 as a whole has an antireflection function.

FIG. 12 is a diagram showing an angular reflection characteristic at a wavelength of 193 nm of the optical element used in the eighth embodiment of the present invention. Here, an ArF (wavelength 193 nm) excimer laser was used. As is clear from FIG. 12, the average reflectance Ra of the S-polarized light Rs and the P-polarized light Rp due to the incident light 20 is about 0.3% or less at the emission angle θ = 40 degrees, and at the emission angle θ = 50 degrees. Is less than about 2%, and it can be used sufficiently.

2nd layer (MgF₂) 103 has some solubility in water (literature value: 2 × 10)^-4Since g / water is 100 g), it will be eluted by long-term use, but in the eighth embodiment of the present invention, the immersion liquid is water (refractive index = 1.44), so that it is the second layer (MgF).₂) There is an advantage that the change in optical performance is relatively small even if 103 is eluted.

Figure 13 shows the second layer (MgF).₂) 103 is a diagram showing the relationship between the reflectance and the emission angle θ in the ArF (wavelength 193 nm) excimer laser of the optical element when the film thickness of 103 is halved (0.3λ). As is clear from FIG. 13, the average reflectance Ra of the S-polarized light Rs and the P-polarized light Rp due to the incident light 20 has hardly changed, and is sufficiently usable. Therefore, MgF₂By forming a film thickness of 103 to about 400 nm, it can be used for about 10 years.

In FIG. 11, the first layer (LaF)₃) 102, 2nd layer (MgF)₂) 103 was described using the two-layer multilayer film 100, but the first layer (LaF)₃) 102, 2nd layer (MgF)₂) 103 may be alternately laminated to form a multilayer film having a four-layer structure.

[Embodiment 9] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 14 is a diagram showing the configuration of the optical element 4 of the present invention. The optical element 4 has a configuration in which a multilayer film 100 is laminated on a fluorite substrate 101. This multilayer film 100 has a two-layer structure, and MgF is used as the first layer 102 from the fluorite substrate 101.₂However, SiO as the second layer 103₂Are stacked in order. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

Here the first layer (MgF₂) 102, 2nd layer (SiO₂) The refractive index of 103 and the optical film thickness and film thickness range of each layer 102 ... are as follows, where λ is the design main wavelength.

<tables num="4"><img file="JP4771300B2_D0004.tif" /></tables>

The film forming method is a vacuum vapor deposition method, but the method is not limited to this method, and various sputtering methods, ion beam assist methods, and ion plating methods capable of producing a dense structure may be used.

FIG. 15 is a diagram showing the relationship between the reflectance and the emission angle in the ArF (wavelength 193 nm) excimer laser of the optical element 4 of the ninth embodiment. As is clear from FIG. 15, the average reflectance of S-polarized light and P-polarized light is about 0.6% or less even at an emission angle of θ = 40 degrees, and is about 1% or less even at an emission angle of θ = 60 degrees. It shows good characteristics and can be used sufficiently.

As shown in Table 4 above, the first layer (MgF)₂The refractive index of) 102 is the adjacent optical substrate 101 and the second layer (SiO).₂) It can be seen that the refractive index is lower than the refractive index of 103. With such an arrangement of the refractive index, the multilayer film 100 as a whole has an antireflection function.

[Embodiment 10] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 16 is a diagram showing the configuration of the optical element 4 of the present invention. The optical element 4 has a configuration in which a multilayer film 100 is laminated on a fluorite substrate 101. In this multilayer film 100, the first layer 102 is MgF.₂, 2nd layer 103 is SiO₂Further, the second layer 103 is divided into two, and the first divided layer 103a formed by the dry film forming method and the second divided layer 103b formed by the wet film forming method are laminated in order. Has been done. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

Here, MgF of the first layer 102₂Dry film formation SiO of the first divided layer 103a₂Wet film formation SiO of the second divided layer 103b₂The refractive index, the optical film thickness of each layer 102 ..., and the film thickness range are as follows, where λ is the design main wavelength.

<tables num="5"><img file="JP4771300B2_D0005.tif" /></tables>

Here, the first layer 102 and the divided first layer 103a were carried out by a vacuum vapor deposition method, but the method is not limited to this method, and other dry methods such as various sputtering methods, ion beam assist methods, and ion plating methods are used. It may be a membrane method.

In this dry film forming method, it is known that the structure of the thin film changes depending on the conditions such as the substrate heating temperature and the film forming rate. In the case of a structure with insufficient denseness, there is a high risk that water will pass through the membrane and reach the fluorite substrate 101. Since fluorite dissolves in water, there is a high risk that the desired optical performance will be lost due to immersion in water. Vacuum-deposited SiO, which generally has a low substrate heating temperature₂Membranes are known to allow water and water vapor to pass through.

In this case, the wet filmed SiO of the second divided layer 103b₂By providing a layer, a dry film-forming SiO₂Wet film formation SiO in the voids of₂Can enter and eliminate voids, so that it is possible to prevent permeation and erosion of the predetermined immersion liquid 108 interposed between the surface of the substrate 107 and the projection optical system PL into the optical element 4, and the projection optical system PL can be prevented. Optical performance can be maintained. Therefore, when this optical element 4 is used in an immersion type projection exposure apparatus, the multilayer film 100 of the present invention does not peel off from the fluorite substrate 101, and the optical element 4 is not dissolved by the liquid. The performance of the projection exposure apparatus can be maintained. Further, since it is not necessary to replace the optical element 4 frequently, the throughput of the projection exposure apparatus can be maintained high.

Wet film formation SiO of this second divided layer 103b₂The layer is a common SiO₂Spin coating is performed with the solution. SiO₂A silica solution for sol-gel is used as the solution, and the fluorite substrate 101 is rotated at a rotation speed of 1000 to 2000 rpm for coating. The film thickness due to coating is SiO₂Since it depends on conditions such as the concentration of the solution, the 101 rotation speed of the fluorite substrate in spin coating, and the temperature and humidity, if a calibration curve for the film thickness is created in advance with the concentration as a parameter, then the desired film thickness is obtained. Can be obtained.

Here, the wet filmed SiO of the second divided layer 103b₂The film thickness of the layer is set to 0.40λ (50 nm), but the film thickness is not limited to this. However, when applying a film thickness of, for example, 1.2λ (150 nm) or more, care must be taken to generate cracks due to film stress. In addition, as a post-treatment, the wet film formation SiO of the second divided layer 103b₂After the layer was applied, annealing was performed at 160 ° C for 2 hours in the atmosphere. This is SiO₂Evaporating alcohol, which is the main solvent of the solution, and wet-forming SiO₂The purpose is to sinter the layer itself.

FIG. 17 is a diagram showing the relationship between the reflectance and the emission angle in the ArF (wavelength 193 nm) excimer laser of the optical element 4 of the tenth embodiment of the present invention. As is clear from FIG. 17, the average reflectance of S-polarized light and P-polarized light is about 0.6% or less even at an emission angle of θ = 40 degrees, and is about 1% or less even at an emission angle of θ = 60 degrees. It shows good characteristics and can be used sufficiently.

In addition, as shown in Table 5 above, the first layer (MgF)₂The refractive index of) 102 is the adjacent optical substrate 101 and the second layer (SiO).₂) It can be seen that it is lower than the refractive index of 103. With such an arrangement of the refractive index, the multilayer film 100 as a whole has an antireflection function. The second layer (SiO)₂) 103 is composed of the first divided layer 103a formed by the dry film forming method and the second divided layer 103b formed by the wet film forming method. Considered one layer.

[Embodiment 11] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 18 is a diagram showing the configuration of the optical element 4 of the present invention. The optical element 4 has a configuration in which a multilayer film 100 is laminated on a fluorite substrate 101. The multilayer film 100 has a four-layer structure, and is LaF3 as the first layer 102 and MgF as the second layer 103 from the fluorite substrate 101.₂LaF as the third layer 104₃, SiO as the 4th layer 105₂Are stacked in order. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

Here, LaF of the first layer 102₃, 2nd layer 103 MgF₂, 3rd layer 104 LaF₃, 4th layer 105 SiO₂The refractive index, the optical film thickness of each layer 102 ..., and the film thickness range are as follows, where λ is the design main wavelength.

<tables num="6"><img file="JP4771300B2_D0006.tif" /></tables>

The film forming method here is the vacuum vapor deposition method, but the method is not limited to this method, and various sputtering methods, ion beam assist methods, and ion plating methods capable of producing a dense structure may be used. ..

FIG. 19 is a diagram showing the relationship between the reflectance and the emission angle in the ArF (wavelength 193 nm) excimer laser of the optical element 4 of the eleventh embodiment of the present invention. As is clear from FIG. 19, the average reflectance of S-polarized light and P-polarized light is about 0.3% or less even at an emission angle of θ = 50 degrees, and is about 0.5% or less even at an emission angle of θ = 60 degrees. It has very good characteristics and can be used sufficiently.

In addition, as shown in Table 6 above, the first layer (LaF)₃The refractive index of) 102 is the adjacent optical substrate 101 and the second layer (MgF).₂) It can be seen that it is higher than the refractive index of 103. Also, the third layer (LaF)₃The refractive index of) 104 is the adjacent second layer (MgF2) 103 and fourth layer (SiO).₂) It can be seen that it is higher than the refractive index of 105. With such an arrangement of the refractive index, the multilayer film 100 as a whole has an antireflection function.

In the eleventh embodiment, the SiO of the fourth layer 105₂Was formed by a vacuum vapor deposition method, but it is also possible to form a film by a wet film forming method as in the second divided layer 103b described in the tenth embodiment. In this case, wet film formation SiO₂By providing a layer, the third layer (LaF) by the dry film formation method₃) Wet film formation SiO in the voids of 104₂Can enter and eliminate voids, so that it is possible to prevent permeation and erosion of the predetermined immersion liquid 108 interposed between the surface of the substrate 107 and the projection optical system PL into the optical element 4, and the projection optical system PL can be prevented. Optical performance can be maintained. Therefore, when this optical element 4 is used in an immersion type projection exposure apparatus, the multilayer film 100 of the present invention does not peel off from the fluorite substrate 101, and the optical element 4 is not dissolved by the liquid. The performance of the projection exposure apparatus can be maintained. Further, since it is not necessary to replace the optical element 4 frequently, the throughput of the projection exposure apparatus can be maintained high.

[Embodiment 12] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 20 is a diagram showing the configuration of the optical element 4 of the present invention. The optical element 4 has a configuration in which a multilayer film 100 is laminated on a fluorite substrate 101. This multilayer film 100 has a five-layer structure, and is LaF as the first layer 102 from the fluorite substrate 101.₃However, as the second layer 103, MgF₂However, LaF as the third layer 104₃, MgF as 4th layer 105₂However, SiO as the 5th layer 106₂Are stacked in order. The immersion liquid 108 is water, and the substrate 107 is resist-coated silicon.

Here, LaF of the first layer 102₃, 2nd layer 103 MgF₂, 3rd layer 104 LaF₃, MgF as 4th layer 105₂, 5th layer 106 SiO₂The refractive index, the optical film thickness of each layer 102 ..., and the film thickness range are as follows, where λ is the design main wavelength.

<tables num="7"><img file="JP4771300B2_D0007.tif" /></tables>

Here, the film forming method is a vacuum vapor deposition method, but the film forming method is not limited to this method, and various sputtering methods, ion beam assist methods, and ion plating methods capable of producing a dense structure may be used. ..

FIG. 21 is a diagram showing the relationship between the reflectance and the emission angle in the ArF (wavelength 193 nm) excimer laser of the optical element of the twelfth embodiment. As is clear from FIG. 21, the average reflectance of S-polarized light and P-polarized light is about 0.3% or less even at an emission angle of θ = 50 degrees, and is about 0.5% or less even at an emission angle of θ = 60 degrees. It shows very good characteristics and can be used sufficiently.

In addition, as shown in Table 7 above, the first layer (LaF)₃The refractive index of) 102 is the adjacent optical substrate 101 and the second layer (MgF).₂) It can be seen that it is higher than the refractive index of 103. Also, the third layer (LaF)₃The index of refraction of) 104 is the adjacent second layer (MgF).₂) 103 and 4th layer (MgF)₂) It can be seen that it is higher than the refractive index of 105. With such an arrangement of the refractive index, the multilayer film 100 as a whole has an antireflection function.

In the 12th embodiment, the SiO of the fifth layer 106₂Was formed by a vacuum vapor deposition method, but it is also possible to form a film by a wet film forming method as in the second divided layer 103b described in the tenth embodiment. In this case, wet film formation SiO₂By providing a layer, the fourth layer (MgF) by the dry film formation method₂) Wet film formation SiO in 105 voids₂Can enter and eliminate voids, so that it is possible to prevent permeation and erosion of the predetermined immersion liquid 108 interposed between the surface of the substrate 107 and the projection optical system PL into the optical element 4, and the projection optical system PL can be prevented. Optical performance can be maintained. Therefore, when this optical element 4 is used in an immersion type projection exposure apparatus, the multilayer film 100 of the present invention does not peel off from the fluorite substrate 101, and the optical element 4 is not dissolved by the liquid. The performance of the projection exposure apparatus can be maintained. Further, since it is not necessary to replace the optical element 4 frequently, the throughput of the projection exposure apparatus can be maintained high.

[Embodiment 13] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

In the thirteenth embodiment, the material of the fourth layer 105 is different from that of the twelveth embodiment. That is, in the thirteenth embodiment, Al is used as the fourth layer 105.₂O₃Is formed.

Here, LaF of the first layer 102₃, 2nd layer 103 MgF₂, 3rd layer 104 LaF₃, 4th layer 105 Al₂O₃, 5th layer 106 SiO₂The refractive index, the optical film thickness of each layer 102 ..., and the film thickness range are as follows, where λ is the design main wavelength.

<tables num="8"><img file="JP4771300B2_D0008.tif" /></tables>

Here, the film forming method is a vacuum vapor deposition method, but the film forming method is not limited to this method, and various sputtering methods, ion beam assist methods, and ion plating methods capable of producing a dense structure may be used. ..

Similar to the 12th embodiment, the average reflectance of the S-polarized light and the P-polarized light is about 0.3% or less even at the emission angle θ = 50 degrees, and the emission angle θ = 60 degrees. Is about 0.5% or less, showing very good characteristics and can be used sufficiently.

In addition, as shown in Table 8 above, the first layer (LaF)₃The refractive index of) 102 is the adjacent optical substrate 101 and the second layer (MgF).₂) It can be seen that it is higher than the refractive index of 103. Also, the third layer (LaF)₃The index of refraction of) 104 is the adjacent second layer (MgF).₂) 103 and 4th layer (Al₂O₃) It can be seen that it is higher than the refractive index of 105. With such an arrangement of the refractive index, the multilayer film 100 as a whole has an antireflection function.

In the thirteenth embodiment, the SiO of the fifth layer 106₂Was formed by a vacuum vapor deposition method, but it is also possible to form a film by a wet film forming method as in the second divided layer 103b described in the tenth embodiment. In this case, wet film formation SiO₂By providing a layer, the fourth layer (Al) by the dry film formation method₂O₃) Wet film formation SiO in 105 voids₂Can enter and eliminate voids, so that it is possible to prevent permeation and erosion of the predetermined immersion liquid 108 interposed between the surface of the substrate 107 and the projection optical system PL into the optical element 4, and the projection optical system PL can be prevented. Optical performance can be maintained. Therefore, when this optical element 4 is used in an immersion type projection exposure apparatus, the multilayer film 100 of the present invention does not peel off from the fluorite substrate 101, and the optical element 4 is not dissolved by the liquid. The performance of the projection exposure apparatus can be maintained. Further, since it is not necessary to replace the optical element 4 frequently, the throughput of the projection exposure apparatus can be maintained high.

According to the projection exposure apparatus according to the sixth to thirteenth embodiments described above, a multilayer film is formed on the surface of the optical element, and the multilayer film has a protective function of protecting the multilayer film from the liquid and the exposure beam ( Since it has an antireflection function for preventing the incident light) from being reflected, it is possible to provide a stable optical element that is not eroded by a liquid. Therefore, it is possible to provide an optical element that enables a high-performance projection exposure apparatus having a high resolution and a deep depth of focus by using the immersion method. Further, since the multilayer film has the protective function for a predetermined period of time, it can be protected from water that has been immersed for 10 years, for example. Therefore, it is possible to provide an optical element that enables a high-performance projection exposure apparatus having a high resolution and a deep focal depth by using a liquid immersion method, and to provide a stable optical element that is not eroded by a liquid for a predetermined period of time.

[Embodiment 14] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 22 is a diagram showing a configuration of an optical member used in the 14th embodiment of the present invention. The optical member 1 has a structure in which a quartz glass thin plate 102 is bonded onto an optical element 101 using fluorite. Here, the immersion liquid is water 103, and the substrate is silicon 104 coated with resist. In the bonding method, when the exposure wavelength is ultraviolet light such as an ArF laser, the bonding surfaces are made flat and optical contact is performed. Optical contact is a phenomenon in which solids are joined together by intermolecular force when flat surfaces are brought into close contact with each other. Optically, there is only a solid-solid interface.

When the surface accuracy of both interfaces of the optical contact is poor and the desired adhesion cannot be obtained, pure water that does not erode the surface of the optical element 101 may be thinly applied between the interfaces to improve the adhesion. The refractive indexes of the optical element 101 and the quartz glass sheet 102 are 1.50 and 1.55, respectively.

FIG. 23 is a diagram showing the angular reflection characteristics of the optical contact (quartz glass / fluorite) interface of FIG. 22. As is clear from FIG. 23, the average reflectance Ra of the S-deflection Rs and the P-deflection Rp due to the incident light 20 is 0.3% or less even at the emission angle θ = 60 degrees, showing good characteristics. It can be used sufficiently.

The reason why the optical element 101 itself is not made of quartz glass as the optical substrate is that the quartz glass thin plate 102 may cause compaction due to laser irradiation, which is not preferable. Further, the reason why the quartz glass thin plate 102 is used is that even if the above compaction occurs, the influence can be minimized.

According to the projection exposure apparatus according to the fourteenth embodiment described above, since the quartz glass thin plate 102 has very low solubility in water, it can be used without deterioration of performance due to erosion, and this element is immersed in liquid. By using it in the method, an immersion optical system without optical deterioration becomes possible.

[Embodiment 15] The projection exposure apparatus was configured in the same manner as in the first embodiment except that the transmission optical element 4 described below was used.

FIG. 24 is a diagram showing a configuration of an optical member used in the fifteenth embodiment of the present invention. The optical member 1 is a crystalline magnesium fluoride (hereinafter referred to as MgF) on an optical element 101 made of fluorite.₂) It is a structure in which thin plates 105 are joined. Here, the immersion liquid is water 103, and the substrate is silicon 104 coated with resist. Optical element 101 and MgF₂The thin plates 105 are filled with a liquid (interpolated solution) 106 having a small difference in refractive index. If the refractive index difference of this interpolation solution 106 is 0.2 or less with respect to each substrate, the residual reflection is small and it can be used satisfactorily.

MgF₂Has some solubility in water (literature value: 2 × 10)^-4g / water 100g), so it will elute after long-term use. If the elution progresses, the transmitted wave surface of the projection lens may be destroyed. Magnesium fluoride (MgF) not suitable for optical element 101₂) Is directly coated, the transmitted wave surface may be destroyed by elution, and in that case, the optical element 101 itself must be replaced, so that it tends to be large-scale. In particular, when the optical element 101 has a lens shape, adjustment with the optical axis of the projection lens is indispensable at the time of replacement, which is not easy. In the case of the fifteenth embodiment of the present invention, since only the thin plate can be replaced, it is possible to replace it with the influence on the imaging performance minimized.

In Embodiment 15 of the present invention, crystalline magnesium fluoride (MgF)₂) Thin plate, but magnesium fluoride (MgF)₂) May be a sintered body. Also, magnesium fluoride (MgF)₂) Coated fluorite sheet or very thin PTFE (Teflon®) sheet may be used. As the coating method in this case, not only general vacuum vapor deposition but also ion plating method and various sputtering methods are not particularly selected.

The thin plate described in the best mode for carrying out the present invention may have a shape like a parallel flat plate.

According to the projection exposure apparatus according to the fifteenth embodiment described above, the tip portion of the projection optical system is not eroded by the liquid. Therefore, since the operation of the projection exposure apparatus is not stopped in order to replace the optical member 1 eroded by water or the like, the final product can be efficiently produced. Further, since the optical member 1 of the present invention is not eroded for a predetermined period during operation of the projection exposure apparatus, the optical characteristics are stable, and the quality of the final product produced by the projection exposure apparatus equipped with the present invention. Is stable.

Although the above description has been made in accordance with the first to fifteenth embodiments, the present invention is not limited to the first to fifteenth embodiments. For example, in the fourth embodiment or the like, magnesium fluoride (MgF) is used as a dissolution prevention film on the surface and side surfaces of the optical element on the substrate side of the projection optical system on the substrate side.₂) Is formed, but hydrophilic silicon oxide (SiO) is formed on the surface of the optical element on the substrate side of the projection optical system on the substrate side.₂) May be formed to form a water-repellent anti-dissolution film composed of an alkyl ketene dimer on the side surface of the optical element on the substrate side of the projection optical system.

Here, the anti-dissolution film formed on the side surface of the optical element is an anti-dissolution film having excellent water repellency as compared with the anti-dissolution film formed on the surface of the optical element on the substrate side. The anti-dissolution film formed on the surface of the substrate side is an anti-dissolution film having excellent hydrophilic performance as compared with the anti-dissolution film formed on the side surface of the optical element. Since the dissolution prevention film formed on the side surface of the optical element is a water-repellent dissolution prevention film, the liquid adhering to the side surface of the optical element can be easily circulated to the substrate side, and the substrate side of the optical element can be easily circulated. Since the anti-dissolution film formed on the surface of the optical element is a hydrophilic anti-dissolution film, the space between the substrate side surface of the optical element and the substrate can always be filled with a liquid.

Further, in the above-described fifth embodiment and the like, silicon dioxide (SiO) is obtained by a sputtering method.₂) The first film formed by the film is formed on the transmissive optical element, but instead of this, a film may be formed by a dry film forming method such as a vacuum vapor deposition method or a CVD method.

Further, in the above-described fifth embodiment or the like, silicon dioxide (SiO) is used as the first film by a dry film forming method.₂) Film is formed, and silicon dioxide (SiO) is used as the second film by a wet film formation method.₂) Film is formed, but magnesium fluoride (MgF) is used as the first film by the dry film formation method.₂) Film is formed, and silicon dioxide (SiO) is used as the second film by a wet film formation method.₂) A film may be formed.

Further, in the above-described embodiment, the liquid fills the space between the surface of the wafer and the optical element formed by the fluorite on the wafer side of the projection optical system, but the surface of the wafer and the wafer side of the projection optical system A liquid may be interposed between the optical element formed of the fluorite.

Further, in the above-described embodiment, pure water is used as the liquid, but the liquid is not limited to pure water, and is transparent to the exposure light and has as high a refractive index as possible, and is applied to the projection optical system or the wafer surface. It is also possible to use a photoresist that is stable with respect to the photoresist (for example, cedar oil, etc.). When F2 laser light is used as the exposure light, a fluorine-based liquid such as a fluorine-based oil or a perfluorinated polyether (PFPE) that can transmit the F2 laser light may be used as the liquid.

Further, in the above-described embodiment, the optical element according to the present invention has a lens shape, but the present invention is not limited to this, and a plate-shaped substrate of fluorite is formed as a cover glass between a conventional fluorite lens and a liquid. It is also possible to form a film and use it as an optical element according to the present invention.

Further, in the above embodiments 14 to 15, a thin coat of pure water is applied to both junction interfaces as an example, but the fluorine-based solvents PFC (perfluorocarbon), HFE (hydrofluoroether), and PFPE (per) are described. Fluoropolyether) can also be applied.

Further, the number and shape of the nozzles used in the embodiment are not particularly limited, and for example, the liquid may be supplied or recovered by two pairs of nozzles on the long side of the tip portion 4A. In this case, the discharge nozzle and the inflow nozzle may be arranged side by side so that the liquid can be supplied and collected from either the + X direction or the -X direction. Good.

[Embodiment 16] As described below, the projection exposure apparatus was configured in the same manner as in the first embodiment except that the optical element in which the optical member is in optical contact via the film is used.

As shown in FIG. 1, the step-and-repeat projection exposure apparatus according to the 16th embodiment includes an illumination optical system 1 that illuminates the reticle (mask) R, a reticle stage apparatus RST that supports the reticle R, and a reticle stage apparatus RST. A wafer stage device that supports the wafer (board) W, a wafer stage drive system 15 that drives the wafer stage device to move the wafer W in three dimensions, and a pattern image formed on the reticle R are projected onto the wafer W. It includes a projection optical system PL, a liquid circulation device that supplies the liquid 7 between the projection optical system PL and the wafer W, and a main control system 14 that comprehensively controls the overall operation of the projection exposure device.

The illumination optical system 1 includes an ArF excimer laser light source which is an exposure light source, and is composed of an optical integrator (homogenizer), a field diaphragm, a condenser lens, and the like. The exposure light IL composed of ultraviolet pulsed light having a wavelength of 193 nm emitted from the light source emits the illumination optical system 1 to illuminate the pattern image provided on the reticle R. The image light that has passed through the reticle R is projected onto the exposure region on the wafer W coated with the photoresist via the projection optical system PL. The exposure light IL is KrF excimer laser light (wavelength 248 nm), F.₂Laser light (wavelength 157 nm), i-line of a mercury lamp (wavelength 365 nm), or the like may be used.

The reticle stage device RST can adjust its position and posture while holding the reticle R. That is, the reticle stage device incorporates a mechanism for finely moving the reticle R in the X and Y directions substantially perpendicular to the optical axis AX of the projection optical system PL and in the rotation direction around the optical axis AX. .. The positions of the reticle R in the X, Y, and rotation directions are measured in real time by a reticle laser interferometer (not shown) and controlled by a reticle stage drive system (not shown).

The position and orientation of the wafer stage device can be adjusted while holding the wafer W. Explaining the specific structure, the wafer W is fixed on the Z stage 9 via the wafer holder, and the Z stage 9 is Z that is substantially parallel to the focus position of the wafer W, that is, the optical axis AX. Allows adjustment of directional position and tilt angle relative to it. The Z stage 9 is fixed on the XY stage 10, and the XY stage 10 is supported on the base 11. The XY stage 10 can move the wafer holder along the XY plane substantially parallel to the image plane of the projection optical system PL, and makes it possible to change the shot region on the wafer W and the like. The positions of the Z stage 9 in the X direction, the Y direction, and the rotation direction are measured in real time by a moving mirror 12 provided on the wafer holder and a wafer laser interferometer 13 that supplies measurement light to the moving mirror 12.

The wafer stage drive system 15 operates in response to a control signal from the main control system 14, and can move the wafer W to a target position at an appropriate timing while maintaining its posture in a desired state.

The projection optical system PL includes a lens barrel 3 that houses a plurality of optical elements or optical components such as a lens formed by processing quartz or fluorite. This projection optical system PL is an imaging optical system that is telecentric on both sides or telecentric on one side on the wafer W side, and a pattern image of the reticle R is transmitted to the shot region on the wafer W via the projection optical system PL, for example, 1 /. It is reduced and projected at a predetermined projection magnification β such as 4, 1/5.

The projection optical system PL is an immersion optical system used in a state where a predetermined liquid 7 is filled between the projection optical system PL and the wafer W. That is, in this projection exposure apparatus, an immersion method is applied in order to substantially shorten the exposure wavelength and improve the resolution. In such an immersion type projection exposure apparatus, the optical element 4 exposed on the surface of the wafer W and the wafer W side of the projection optical system PL at least while the pattern image of the reticle R is transferred onto the wafer W. Liquid 7 is filled between the tip surface and the surface of the wafer. As the liquid 7, pure water, which can be easily obtained in large quantities at semiconductor manufacturing factories and the like, is used. Since pure water has an extremely low content of impurities, it can be expected to have an action of cleaning the surface of the wafer W. During exposure, only the tip of the optical element 4 on the wafer W side of the projection optical system PL is configured to come into contact with the liquid 7, so that corrosion of the lens barrel 3 made of metal is prevented. ..

FIG. 25 is a side sectional view conceptually explaining the structure of the optical element 4 projecting on the wafer W side of the projection optical system PL used in this embodiment.

As is clear from FIG. 25, in the optical element 4, the substrate material 201, which is an optical element formed of fluorite, and the optical member 202, which is a substrate material formed of synthetic quartz, are in optical contact with each other (optical). It is formed by adhering). In this projection optical system PL, only the optical member 202 on the front end side of the optical element 4 comes into contact with the liquid 7 such as pure water, and the substrate material 201 on the back side does not come into direct contact with the liquid 7. In this way, the reason why the optical member 202 covers the tip of the projection optical system PL is that the optical element 4 made of fluorite is slightly soluble in the liquid 7 such as pure water. The optical element 4 is protected by an optical member 202 made of synthetic quartz having high water resistance.

When the optical member 202 is held and fixed on the optical element 4 by using an optical contact, between the optical element 4 and the optical member 202 so that the optical member 202 does not shift or fall off with respect to the optical element 4. It is necessary to increase the joint strength of. Therefore, a thin coating film 203 made of an oxide is formed on the surface of the substrate material 201 of the optical element 4 on the side to be subjected to optical contact. On the other hand, no coating film is particularly formed on the surface of the optical member 202 on the side to be subjected to optical contact. By interposing the coating film 203 between the substrate material 201 of the optical element 4 and the optical member 202 in this way, the bonding strength between the optical element 4 and the optical member 202 is increased.

Hereinafter, the reason why the bonding strength between the optical element 4 and the optical member 202 is increased will be briefly described. As a factor that affects the joint strength of optical contacts, the surface roughness of the joint surface is known as shown in Japanese Patent Application Laid-Open No. 9-221342. However, it has recently been found that chemical factors other than surface roughness affect optical contact, and the present inventor controls such chemical factors to control the tip of the projection optical system PL. It has been found that the bonding strength between the substrate material 201 and the optical member 202 constituting the optical element 4 can be increased.

In the conventional optical contact between oxide optical materials, hydroxyl groups (-OH) are present at high densities on both surfaces to be bonded, so that they are brought into close contact with each other by hydrogen bonding or dehydration condensation. It is considered that a covalent bond occurs and a strong bond is obtained. On the other hand, in the optical element 4 of the present embodiment, the fluoride (specifically, CaF) constituting the substrate material 201 of the optical element 4₂) Has a lower hydroxyl group density than the oxide surface, so it is considered that a strong bond cannot be obtained even if the surface is brought into close contact with the optical member 202 as it is. Therefore, it was decided to introduce a sufficient amount of hydroxyl groups into the joint surface by coating the fluoride surface of the substrate material 201 with a coating film 203 made of an oxide. As a result, strong optical contact can be achieved between the substrate material 201 and the optical member 202. Specifically, silicon dioxide (SiO) is used on the substrate material 201 by using vacuum vapor deposition.₂) Is uniformly deposited on the thin coating film 203.

Further, since the coating film 203 made of silicon dioxide is vacuum-deposited on the substrate material 201 made of fluorite, it is possible to suppress the occurrence of cracks or the like in the coating film 203. That is, since there is no large difference between the coefficient of thermal expansion of fluorite and the coefficient of thermal expansion of silicon dioxide, the substrate material 201 and the like are placed at room temperature after the coating film 203 is formed on the heated substrate material 201. Even if it is cooled to the extent, it is possible to prevent cracks from occurring in the coating film 203 and residual stress strain. When a fluoride film is formed on quartz, cracks are likely to occur in the film due to the difference in thermal expansion coefficient of about one digit.

26 to 29 are views for briefly explaining the manufacturing process of the optical element 4 shown in FIG. 25. As shown in Figure 26, first fluorite (CaF)₂) Is processed to prepare a substrate material 201 which is an optical element having a predetermined optical surface OS1. Next, as shown in FIG. 27, SiO is placed on the optical surface OS1 while heating the substrate material 201.₂Layers are deposited to form a coating film 203. Thereby, the substrate material 201 on which the coating film 203 is formed can be prepared. At this time, by using vacuum vapor deposition, it is possible to form a high-density coating film 203 having good adhesion to the substrate material 201. Next, as shown in FIG. 28, synthetic quartz (SiO)₂) Is processed to prepare an optical member 202 having a predetermined optical surface OS2. Finally, as shown in FIG. 29, the substrate material 201 and the optical member 202 are laminated to form an optical contact between the surface OS3 of the coating film 203 of the substrate material 201 and the optical surface OS2 of the optical member 202. , Complete the optical element 4.

In a specific production example, fluorite (CaF) constituting the substrate material 201 of the optical element 4₂), The optical surface OS1 on the injection side was processed into a flat surface. Further, the film thickness of the coating film 203 formed by heating the substrate material 201 at the time of film formation by vacuum vapor deposition was set to about 10 nm. On the other hand, for the optical member 202, a synthetic quartz substrate was processed into a parallel flat plate having a thickness of 1 mm. After that, the optical contact surface of the substrate material 201 of the optical element 4 and the optical contact surface of the optical member 202 are bonded and joined without using an adhesive. In order to confirm the strength of the optical contact of the optical element 4 formed in this way, the following experiment was performed.

That is, in order to evaluate the transmittance of the optical element 4, the transmittance (%) at a wavelength of 193.4 nm was measured with a spectrophotometer for ultraviolet measurement. In addition, in order to evaluate the strength of the optical element 4, a tensile load test was conducted using a precision universal material tester. In the tensile load test, a tensile load is applied to separate the optical member 202 from the substrate material 201 of the optical element 4, that is, in a direction perpendicular to the optical contact surface, and the optical member 202 is peeled off. Peel off the value weighted (Kgf / cm)²). For comparison, a substrate material 201 having no coating film 203 was prepared, and a comparative sample in which the substrate material 201 and the optical member 202 were directly optically contacted was also prepared. The results are shown in Table 9 below.

<tables num="9"><img file="JP4771300B2_D0009.tif" /></tables>

As is clear from Table 9 above, the optical element 4 of this embodiment (Example: SiO)₂In (with layers), a comparative sample (comparative example: SiO) for optical contacts₂It can be seen that the peeling resistance is several times higher than that of the optical element (without layer), and the light amount loss related to the exposure light wavelength is the same and comparable.

Returning to FIG. 1, the liquid circulation device includes a liquid supply device 5 and a liquid recovery device 6. Of these, the liquid supply device 5 includes a tank for the liquid 7, a pressure pump, a temperature control device, and the like, and controls the temperature between the wafer W and the tip of the optical element 4 via the supply pipe 21 and the discharge nozzle 21a. Supply the liquid 7 in the finished state. Further, the liquid recovery device 6 includes a tank for the liquid 7, a suction pump, and the like, and recovers the liquid 7 between the wafer W and the tip of the optical element 4 via the recovery pipe 23 and the inflow nozzles 23a and 23b. .. The temperature of the liquid 7 circulated by such a liquid circulation device is set to be about the same as the temperature in the chamber in which the projection exposure device of the present embodiment is housed, for example. The refractive index n of pure water with respect to exposure light having a wavelength of about 200 nm is about 1.44, and the ArF excimer laser light having a wavelength of 193 nm is shortened to 1 / n, that is, apparently 134 nm on the wafer W. Therefore, a high resolution can be obtained.

FIG. 3 is a plan view showing the arrangement relationship of the discharge nozzle 21a and the inflow nozzles 23a and 23b of FIG. 1 in the X direction, and FIG. 4 is a plan view showing the arrangement relationship of the discharge nozzle 21a and the inflow nozzles 23a and 23b of FIG. It is a top view which shows the arrangement relation of thing about a direction.

As shown in FIG. 4, the first discharge nozzle 21a having a thin tip on the + X direction is arranged so as to sandwich the tip 4A of the optical element 4, which is the tip of the projection optical system, and -X. A second discharge nozzle 22a having a thin tip on the directional side is arranged. The first and second discharge nozzles 21a and 22a are connected to the liquid supply device 5 via the first and second supply pipes 21 and 22, respectively. Further, a pair of first inflow nozzles 23a spread at the tip on the + X direction side are arranged so as to sandwich the tip 4A of the optical element 4, and a pair of first inflow nozzles 23a spread at the tip on the -X direction side. 2 Inflow nozzle 24a is arranged. The first and second inflow nozzles 23a and 24a are connected to the liquid recovery device 6 via the first and second recovery pipes 23 and 24, respectively.

When the wafer W is stepped in the direction of the arrow 25A indicated by the solid line (-X direction), it is between the tip portion 4A of the optical element 4 and the wafer W via the first supply tube 21 and the first discharge nozzle 21a. Supply liquid 7. In synchronization with this, the liquid 7 supplied between the tip portion 4A of the optical element 4 and the wafer W is recovered via the second recovery tube 24 and the second inflow nozzle 24a. On the other hand, when the wafer W is stepped in the direction 26A (+ X direction) indicated by the dotted line, the tip portion 4A of the optical element 4 and the wafer W pass through the second supply tube 22 and the second discharge nozzle 22a. Supply liquid 7 between and. In synchronization with this, the liquid 7 supplied between the tip portion 4A of the optical element 4 and the wafer W is recovered via the first recovery tube 23 and the first inflow nozzle 23a.

As shown in FIG. 4, a third discharge nozzle 27a having a thin tip on the + Y direction is arranged so as to sandwich the tip 4A of the optical element 4, and has a thin tip on the -Y direction. The fourth discharge nozzle 28a is arranged. The third and fourth discharge nozzles 27a and 28a are connected to the liquid supply device 5 via the third and fourth supply pipes 27 and 28, respectively. Further, a pair of third inflow nozzles 29a spread at the tip on the + Y direction side are arranged so as to sandwich the tip 4A of the optical element 4, and a pair of third inflow nozzles 29a spread at the tip on the -Y direction side. 4 Inflow nozzle 30a is arranged. The third and fourth inflow nozzles 29a and 30a are connected to the liquid recovery device 6 via the third and fourth recovery pipes 29 and 30, respectively.

The step movement of the wafer W in the ± Y direction is the same as the step movement in the ± X direction, and the third and fourth supply pipes 27 and 28 are switched to correspond to the third and fourth discharge nozzles 27a and 28a. On the other hand, the liquid 7 is discharged, and the third and fourth recovery pipes 29 and 30 are switched to suck the liquid 7 in the corresponding pair of the third and fourth inflow nozzles 29a and 30a.

As described above, not only the nozzles 23a to 30a for supplying and collecting the liquid 7 from the X direction or the Y direction, but also a nozzle for supplying and collecting the liquid 7 from, for example, an oblique direction may be provided. ..

Returning to FIG. 1, the main control system 14 transmits a control signal to the drive mechanism incorporated in the reticle stage device RST, and finely moves the reticle stage to adjust the position and attitude of the reticle R. At this time, the positions of the reticle R in the X direction, the Y direction, and the rotation direction are measured by a reticle laser interferometer (not shown).

Further, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the Z stage 9 via the wafer stage drive system 15 to adjust the focus position and the inclination angle of the wafer W. Further, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 via the wafer stage drive system 15 to drive the positions of the wafer W in the X direction, the Y direction, and the rotation direction. Make adjustments. At this time, the position of the reticle R in the X direction, the Y direction, and the rotation direction is measured by the wafer laser interferometer 13.

At the time of exposure, the main control system 14 transmits a control signal to the wafer stage drive system 15 and drives the XY stage 10 via the wafer stage drive system 15 to sequentially bring each shot region on the wafer W to the exposure position. Move step by step. That is, the operation of exposing the pattern image of the reticle R on the wafer W is repeated by the step-and-repeat method.

The main control system 14 appropriately operates a liquid circulation device including the liquid supply device 5 and the liquid recovery device 6 during or before and after the exposure, and between the lower end of the projection optical system PL and the wafer W while the wafer W is moving. The supply amount and the recovery amount of the liquid 7 to be filled in the container 7 are controlled. With reference to FIG. 5, when the movement of the wafer W is in the -X direction along the arrow 25A, for example, the liquid 7 supplied from the first discharge nozzle 21a flows in the direction of the arrow 25A (-X direction). , Collected by the second inflow nozzles 23a and 23b. Here, in order to keep the amount of the liquid 7 filled between the optical element 4 and the wafer W while the wafer W is moving, the supply amount of the liquid 7 Vi (m).³/ s) and recovery amount Vo (m)³Equal to / s). Further, in order to avoid excessive circulation or insufficient circulation of the liquid 7, the total amount of the supply amount Vi and the recovery amount Vo of the liquid 7 is adjusted based on the moving speed v of the XY stage 10, that is, the wafer W. For example, the supply amount Vi and the recovery amount Vo of the liquid LQ can be calculated based on the following equation (1).

Vi = Vo = D v d ... (1) Here, D is the diameter (m) of the tip 4A of the optical element 4, v is the moving speed of the wafer W by the XY stage 10 (m / s), and d is the working distance of the projection optical system PL (working distance). (m). The main control system 14 controls the step movement of the XY stage 10, and by calculating the supply amount Vi and the recovery amount Vo of the liquid 7 based on the equation (1) corresponding to the step movement of the XY stage 10. The liquid 7 can always be filled in a stable state between the optical element 4 and the wafer W. By controlling the supply amount Vi and the recovery amount Vo of the liquid 7 in this way, the liquid 7 may unnecessarily protrude from the optical element 4, or even the optical member 202 at the tip of the optical element 4 may be immersed in the liquid 7. Can be prevented. Therefore, it is possible to prevent erosion of the optical element 4 and damage to the optical contact with the optical member 202, and it is possible to maintain the performance of the optical element 4 for a long period of time. That is, the frequency of replacement of the optical element 4 can be reduced, the throughput of the exposure process of the wafer W can be maintained high, and the final product can be efficiently produced with stable quality.

The above has been related to the case where the wafer W is moved in the ± X direction, but when the wafer W is moved in the ± Y direction, the liquid held between the optical element 4 and the wafer W is controlled by the same control. The amount of 7 can be maintained stably.

The working distance d of the projection optical system PL is preferably as narrow as possible in order for the liquid 7 to stably exist between the optical element 4 and the wafer W. For example, the working distance d of the projection optical system PL is set to about 2 mm.

As is clear from the above description, according to the projection exposure apparatus of this embodiment, the optical element 4 obtained by firmly joining the optical element 4 and the optical member 202 by an excellent optical contact and having a high transmittance 4 Since the projection optical system PL incorporating the above is used, immersion type exposure processing that can maintain high performance for a long period of time becomes possible.

Although the above description has been made in accordance with the 16th embodiment, the present invention is not limited to the 16th embodiment. For example, as the material of the substrate material 201 of the optical element 4, barium fluoride (BaF) is used instead of fluorite, although it depends on the wavelength used.₂), Magnesium fluoride (MgF)₂) Etc. can be used.

The material of the substrate material 201 of the optical element 4 is silicon dioxide (SiO), although it depends on the wavelength used.₂) Instead of aluminum oxide (Al₂O₃) Etc. can be used. The coating film 203 is not limited to a film having a single composition, and may be formed by laminating two or more types of films. In this case as well, the uppermost layer is an oxide film such as silicon dioxide. It is desirable to do.

Further, as the material of the optical member 202, sapphire or the like can be used instead of quartz, although it depends on the wavelength used. Further, silicon dioxide (SiO) on the surface of fluoride glass or the like.₂The optical member 202 can also be obtained by depositing a thin film such as).

Further, the shapes of the substrate material 201 and the optical member 202 of the optical element 4 are not limited to those of the above-described embodiment. For example, the surface of the optical element 4 and the optical member 202 for optical contact is not limited to a flat surface, and may be a curved surface having various curvatures.

Further, in the above embodiment, silicon dioxide (SiO) is placed on the substrate material 201 by a vacuum vapor deposition method.₂) Was formed, but instead of this, ion beam assisted vapor deposition method, gas cluster ion beam assisted vapor deposition method, ion plating method, ion beam sputtering method, magnetron sputtering method, bias sputtering method, ECR sputtering method, RF sputtering method , Any one of a film forming method such as a thermal CVD method, a plasma CVD method, and an optical CVD method can be used.

Further, in the above embodiment, the entire gap space between the tip portion 4A of the optical element 4 and the surface of the wafer W is filled with the liquid 7, but the liquid 7 is interposed in a part of such a gap space. You may.

Further, in the above embodiment, pure water is used as the liquid 7, but the photoresist is not limited to pure water, has transparency to exposure light, has a high refractive index as much as possible, and is applied to a projection optical system or a wafer surface. Various liquids (for example, cedar oil) that are stable against the light can be used. The exposure light is F.₂When using laser light, as liquid 7, F₂Fluorine-based liquids such as fluorine-based oils and perfluoropolyethers (PFPE) that can transmit laser light can be used.

Further, the arrangement and number of nozzles and the like in the above embodiment are examples, and the arrangement and number of nozzles can be appropriately changed according to the size and moving speed of the wafer W.

[Embodiment 17] Next, the projection exposure apparatus according to the seventeenth embodiment will be described with reference to the drawings. FIG. 30 is a front view showing the lower part of the projection optical system PLA of the step-and-scan projection exposure apparatus according to the seventeenth embodiment, the liquid supply apparatus 5, the liquid recovery apparatus 6, and the like. Further, in the following description, the XYZ Cartesian coordinate system shown in FIG. 30 is set, and the positional relationship of each member will be described with reference to this XYZ Cartesian coordinate system. The XYZ Cartesian coordinate system is set so that the X-axis and the Y-axis are parallel to the wafer W, and the Z-axis is set in the direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set to the vertically upward direction. In FIG. 30, the same configuration as the projection exposure apparatus according to this embodiment will be described with the same reference numerals as those used in the first embodiment.

In this projection exposure apparatus, the transmission optical element 32 at the lowermost end of the lens barrel 3A of the projection optical system PLA has the tip portion 32A on the wafer W side in the Y direction (non-scanning direction), leaving only the portion required for scanning exposure. It has been cut into an elongated rectangle. At the time of scanning exposure, a pattern image of a part of the reticle (not shown) is projected on the rectangular exposure area directly below the tip 32A on the wafer W side, and the reticle (not shown) is projected on the projection optical system PLA. In synchronization with the movement at velocity V in the -X direction (or + X direction), the wafer W moves in the + X direction (or -X direction) via the XY stage 10 with velocities β · V (β is the projection magnification). Move with. Then, after the exposure to one shot region is completed, the next shot region is moved to the scanning start position by the stepping of the wafer W, and the exposure to each shot region is sequentially performed by the following step-and-scan method.

In this embodiment, the same transmission optical element 4 (see FIG. 2) used in the first embodiment is used as the transmission optical element 32. That is, the base material of the transmission optical element 32 is fluorite, and the crystal orientation of the film-forming surface of the fluorite is the (111) plane. Further, magnesium fluoride (MgF) is used as a dissolution prevention film on the tip portion 32A of the transmission optical element 32 on the wafer W side, that is, the portion through which exposure light is transmitted.₂) Membrane F1 and silicon dioxide (SiO)₂) Film F2 is formed by vacuum deposition method, and further silicon dioxide (SiO)₂) The film F3 is formed by a wet film forming method.

Further, on the tapered surface 32B of the transmission optical element 32, that is, the portion where the exposure light is not transmitted, a tantalum (Ta) film F5 (F4) is formed as a metal dissolution prevention film (also serving as an adhesion strengthening film) by a sputtering method. ing. Further, on the surface of the metal dissolution prevention film (dissolution prevention film) F5, silicon dioxide (SiO) is used as a metal dissolution prevention film protection film (dissolution prevention film protection film) for protecting the metal dissolution prevention film.₂) Membrane F6 is silicon dioxide (SiO)₂) The film is formed by the wet film forming method at the same time as the film F3. Here, the solubility of the metal dissolution prevention film (dissolution prevention film) F5 formed on the tapered surface 32B of the transmission optical element 4 in pure water is 2 ppt or less, and the packing density is 95% or more. Further, the average reflectance of the anti-dissolution films F1 to F3 formed on the tip portion 32A of the transmission optical element 32 when the emission angle of the exposure beam is 50 degrees is 2% or less.

Since the immersion method is applied in the 17th embodiment as in the 1st embodiment, the liquid 7 is filled between the transmission optical element 32 and the surface of the wafer W during the scanning exposure. Pure water is used as the liquid 7. The liquid 7 is supplied and recovered by the liquid supply device 5 and the liquid recovery device 6, respectively.

FIG. 31 shows the positional relationship between the surface of the transmission optical element 32 of the projection optical system PLA (tip 32A on the wafer W side and the tapered surface 32B) and the discharge nozzle and the inflow nozzle for supplying and collecting the liquid 7 in the X direction. It is a figure which shows. As shown in FIG. 31, the liquid supply device 5 has three discharge nozzles 21a to 21c on the + X direction side of the tip portion 32A and the tapered surface 32B, which are elongated and rectangular in the Y direction via the supply pipe 21. , Three discharge nozzles 22a to 22c are connected to the -X direction side of the tip portion 32A and the tapered surface 32B. Further, in the liquid recovery device 6, as shown in FIG. 31, two inflow nozzles 23a and 23b are provided via the recovery pipe 24 on the -X direction side of the tip portion 32A and the tapered surface 32B via the recovery pipe 23. Two inflow nozzles 24a and 24b are connected to the tip portion 32A and the tapered surface 32B on the + X direction side.

When the wafer W is moved in the scanning direction (-X direction) indicated by the solid arrow to perform scanning exposure, the liquid supply device 5 is the transmission optical element 32 via the supply pipe 21 and the discharge nozzles 21a to 21c. Liquid 7 is supplied between the tip portion 32A and the tapered surface 32B and the wafer W. The liquid recovery device 6 recovers the liquid 7 supplied between the tip portion 32A and the tapered surface 32B and the wafer W by the liquid supply device 5 via the recovery pipe 23 and the inflow nozzles 23a and 23b. In this case, the liquid 7 flows on the wafer W in the X direction, and the space between the transmission optical element 32 and the wafer W is filled with the liquid 7.

Further, when the wafer W is moved in the direction indicated by the arrow of the two-dot chain line (+ X direction) for scanning exposure, the liquid supply device 5 is an optical element via the supply pipe 22 and the discharge nozzles 22a to 22c. Liquid 7 is supplied between the tip portion 32A of 32 and the wafer W. The liquid recovery device 6 recovers the liquid 7 supplied between the tip portion 32A and the wafer W by the liquid supply device 5 via the recovery pipe 24 and the inflow nozzles 24a and 24b. In this case, the liquid 7 flows on the wafer W in the + X direction, and the space between the optical element 32 and the wafer W is filled with the liquid 7.

Also, the supply amount of liquid 7 Vi (m)³/ s) and recovery amount Vo (m)³/ s) is calculated by the following formula 2. (Formula 2) Vi = Vo = DSY v d Here, DSY is the length (m) of the tip portion 32A of the optical element 32 in the X direction. Since the DSY is pre-populated, the supply of liquid 7 Vi (m) based on Equation 2.³/ s) and recovery amount Vo (m)³By calculating / s) and adjusting it, the liquid 7 is stably filled between the optical element 32 and the wafer W even during scanning exposure.

Further, when the wafer W is stepped in the Y direction, the liquid 7 is supplied and recovered from the Y direction by the same method as in the first embodiment.

FIG. 32 is a diagram showing the positional relationship between the tip portion 32A of the optical element 32 of the projection optical system PLA and the discharge nozzle and the inflow nozzle for the Y direction. As shown in FIG. 32, when the wafer W is stepped in the non-scanning direction (-Y direction) orthogonal to the scanning direction, the discharge nozzles 27a and the inflow nozzles 29a and 29b arranged in the Y direction are used. Supply and recover liquid 7. When the wafer is stepped in the + Y direction, the liquid 7 is supplied and recovered using the discharge nozzles 28a and the inflow nozzles 30a and 30b arranged in the Y direction. In this case, the supply amount of liquid 7 Vi (m)³/ s) and recovery amount Vo (m)³/ s) is calculated by the following formula 3. (Formula 3) Vi = Vo = DSX v d Here, DSX is the length (m) of the tip portion 32A of the optical element 32 in the Y direction. Similar to the first embodiment, the liquid 7 fills the space between the optical element 32 and the wafer W by adjusting the supply amount of the liquid 7 according to the moving speed v of the wafer W when the step is moved in the Y direction. carry on.

According to the projection exposure apparatus according to the 17th embodiment, the same operations and effects as those of the 1st embodiment are exhibited.

That is, first, since the dissolution prevention film is formed on the surface of the optical element, the dissolution of the optical element can be prevented. Therefore, since the optical element is not dissolved by the liquid filled between the tip of the projection optical system and the substrate, it is not necessary to replace the optical element frequently, and the high throughput of the exposure apparatus can be maintained. it can. Further, it is not necessary to stop the operation of the exposure apparatus in order to replace the melted optical element, and the final product can be efficiently produced. Furthermore, since the optical element is not dissolved by the liquid, the optical performance of the projection optical system can be maintained, so that the quality of the final product produced can be stabilized and the exposure can be continued in the optimum state. Can be done.

Further, according to the projection exposure apparatus according to the 17th embodiment, a metal dissolution prevention film that also serves as an adhesion strengthening film is formed on the tapered surface 32B of the transmission optical element 32 on the wafer W side of the projection optical system PLA. Therefore, the metal dissolution prevention film can be brought into close contact with the transmission optical element 32. In addition, silicon dioxide (SiO) on the surface of the metal dissolution prevention film.₂) Since the film is formed, it is possible to prevent damage to the metal dissolution prevention film which is soft and has low scratch resistance, and it is possible to protect the metal dissolution prevention film. Therefore, it is possible to prevent the liquid 7 interposed between the surface of the wafer W and the projection optical system PLA from penetrating and eroding into the transmission optical element 32, and the optical performance of the projection optical system PLA can be maintained. .. Further, since the transmission optical element 32 is not dissolved by the liquid 7, the performance of the exposure apparatus can be maintained. Further, since it is not necessary to replace the transmission optical element 32 frequently, the throughput of the projection exposure apparatus can be maintained high.

[Embodiments 18-31] The projection exposure apparatus of the 18th to 31st embodiments was configured in the same manner as the 17th embodiment except that the same transmission optical element 4 used in the 2nd to 15th embodiments was used as the transmission optical element 32, respectively.

According to the projection exposure apparatus of the 18th to 31st embodiments configured in this way, the same operations and effects as those of the projection exposure apparatus configured with the 2nd to 15th embodiments can be obtained.

[Embodiment 32] As described below, the projection exposure apparatus was configured in the same manner as in the 17th embodiment except that the optical element in which the optical member is in optical contact via the film is used. The projection exposure apparatus of the 32nd embodiment is obtained by partially modifying the projection exposure apparatus of the 16th embodiment so as to perform exposure by a step-and-scan method, which is common to the 16th embodiment. For, the same sign is quoted and duplicate explanation is omitted.

In the projection exposure apparatus of the 32nd embodiment shown in FIG. 30, the optical element 32 protruding from the lowermost end of the lens barrel 3A of the projection optical system PLA has a tip portion 32A leaving only a portion necessary for scanning exposure in the Y direction (non-Y direction). It is cut into an elongated rectangle in the scanning direction). At the time of scanning exposure, a pattern image of a part of the reticle is projected on the rectangular exposure area directly under the tip 32A, and the reticle (not shown) has a velocity in the -X direction (or + X direction) with respect to the projection optical system PLA. In synchronization with the movement at V, the wafer W moves in the + X direction (or -X direction) via the XY stage 10 at velocities β · V (β is the projection magnification). Then, after the exposure to one shot region is completed, the next shot region is moved to the scanning start position by the stepping of the wafer W, and the exposure to each shot region is sequentially performed by the following step-and-scan method.

Since the immersion method is applied to the embodiment 32 as in the embodiment 16, the liquid 7 such as pure water is filled between the lower surface of the optical element 32 and the surface of the wafer W during the scanning exposure. The optical element 32 is composed of a substrate material 201 made of fluorite and an optical member 202 made of quartz, as in the case of the 16th embodiment (see FIG. 25). Then, in this optical element 32, silicon dioxide (SiO) is placed on the substrate material 201 of the optical element 32.₂) Is uniformly deposited to realize a strong optical contact. As a result, the substrate material 201 made of fluorite can be protected from the liquid 7, and the durability of the optical element 32 and the projection optical system PLA can be improved.

FIG. 31 is a diagram showing the positional relationship between the discharge nozzle and the inflow nozzle for supplying and collecting the liquid directly under the projection optical system PLA. The liquid supply device 5 has three discharge nozzles 21a to 21c on the + X direction side of the tip portion 32A via the supply pipe 21, and 3 on the -X direction side of the tip portion 32A via the supply pipe 22. The two discharge nozzles 22a to 22c are connected. Further, in the liquid recovery device 6, two inflow nozzles 23a and 23b are provided on the + X direction side of the tip portion 32A via the recovery pipe 23, and 2 on the -X direction side of the tip portion 32A via the recovery pipe 24. The inflow nozzles 24a and 24b are connected.

When the wafer W is moved in the scanning direction (-X direction) indicated by the solid arrow to perform scanning exposure, the liquid supply device 5 is connected to the tip portion 32A of the optical element 32 via the supply pipe 21 and the discharge nozzles 21a to 21c. Liquid 7 is supplied between the wafer W and the wafer W. The liquid recovery device 6 recovers the liquid 7 held between the tip portion 32A and the wafer W via the recovery pipe 23 and the inflow nozzles 23a and 23b. In this case, the liquid 7 is flowing on the wafer W in the -X direction, and the space between the optical element 32 and the wafer W is always filled with the liquid 7.

Further, when the wafer W is moved in the direction indicated by the arrow of the alternate long and short dash line (+ X direction) to perform scanning exposure, the liquid supply device 5 is the tip of the optical element 32 via the supply tube 22 and the discharge nozzles 22a to 22c. Liquid 7 is supplied between the portion 32A and the wafer W. The liquid recovery device 6 recovers the liquid 7 held between the tip portion 32A and the wafer W via the recovery pipe 24 and the inflow nozzles 24a and 24b. In this case, the liquid 7 is flowing on the wafer W in the + X direction, and the space between the optical element 32 and the wafer W is always filled with the liquid 7.

The arrangement of the discharge nozzle and the inflow nozzle for circulating the liquid 7 between the optical element 32 and the wafer W when the wafer W is moved in the ± Y direction is almost the same as in the case of the 16th embodiment. ..

According to the scanning projection exposure apparatus of the 32nd embodiment, a projection optical system incorporating an optical element 32 obtained by firmly joining the optical element 32 and the optical member 202 by an excellent optical contact and having a high transmittance. Since PLA is used, immersion type exposure processing that can maintain high performance for a long period of time becomes possible.

[Embodiment 33] The exposure apparatus according to the 33rd embodiment of the present invention will be described with reference to the drawings. The exposure apparatus according to the present embodiment is an immersion exposure apparatus to which an immersion method is applied in order to substantially shorten the exposure wavelength to improve the resolution and substantially increase the depth of focus. FIG. 33 shows the first optical element LS1 and the first optical element closest to the image plane of the projection optical system PL among the optical elements formed by the plurality of fluorites constituting the projection optical system PL of the exposure apparatus according to the present embodiment. It is a figure which shows the 2nd optical element LS2 which is close to the image plane of the projection optical system PL next to the optical element LS1.

This exposure apparatus fills the space between the lower surface T1 of the first optical element LS1 closest to the image plane of the projection optical system PL and the substrate P among the plurality of optical elements constituting the projection optical system PL with the first liquid LQ1. It has a first immersion mechanism for. The substrate P is provided on the image plane side of the projection optical system PL, and the lower surface T1 of the first optical element LS1 is arranged so as to face the surface of the substrate P. The first immersion mechanism is a first liquid supply mechanism 90 that supplies the first liquid LQ1 between the lower surface T1 of the first optical element LS1 and the substrate P, and a first liquid supply mechanism 90 that is supplied by the first liquid supply mechanism 90. It is equipped with a first liquid recovery mechanism 91 that recovers the liquid LQ1.

Further, this exposure apparatus is a second for filling the space between the first optical element LS1 and the second optical element LS2, which is next to the first optical element LS1 and next to the image plane of the projection optical system PL, with the second liquid LQ2. It has an immersion mechanism. The second optical element LS2 is arranged above the first optical element LS1, and the upper surface T2 of the first optical element LS1 is arranged so as to face the lower surface T3 of the second optical element LS2. The second immersion mechanism is a second liquid supply mechanism 92 that supplies the second liquid LQ2 between the first optical element LS1 and the second optical element LS2, and a second liquid supply mechanism 92 that is supplied by the second liquid supply mechanism 92. It is equipped with a second liquid recovery mechanism 93 that recovers the liquid LQ2.

The lens barrel PK is provided with a facing surface 89 facing the peripheral region of the upper surface T2 of the first optical element LS1. A first seal member 94 is provided between the peripheral region of the upper surface T2 and the facing surface 89. The first seal member 94 is composed of, for example, an O-ring (for example, "Carletz" manufactured by DuPont Dow Inc.) or a C-ring. The first sealing member 94 prevents the second liquid LQ2 arranged on the upper surface T2 from leaking to the outside of the upper surface T2, and eventually to the outside of the lens barrel PK. Further, a second seal member 95 is provided between the side surface C2 of the second optical element LS2 and the inner side surface PKC of the lens barrel PK. The second seal member 95 is composed of, for example, a V ring. The second seal member 95 regulates the flow of moist gas generated by the second fluid LQ2 and the second fluid LQ2 above the second optical element LS2 inside the lens barrel PK.

Further, a third seal member 96 is provided between the side surface C1 of the first optical element LS1 and the inner side surface PKC of the lens barrel PK. The third seal member 96 is composed of, for example, a V ring. The third seal member 96 regulates the flow of the first fluid LQ1 and the moist gas generated by the first fluid LQ1 above the first optical element LS1 inside the lens barrel PK.

A light-shielding film F5 on which gold (Au) is formed with a film thickness of 150 nm is formed on the side surface (tapered surface) C1 of the first optical element LS1 and the side surface (tapered surface) C2 of the second optical element LS2. Therefore, exposure light and exposure from the wafer to the first seal member 94, the second seal member 95, and the third seal member 96 provided around the tapered surface of the transmission optical element on the substrate side of the projection optical system by the light-shielding film. It is possible to prevent the light reflected light from being irradiated, and it is possible to prevent the sealing member from being deteriorated.

In the 33rd embodiment described above, the side surface (tapered surface) C1 of the first optical element LS1 and the side surface (tapered surface) C2 of the second optical element LS2 are formed of a metal film using gold (Au). A light-shielding film is formed, but the light-shielding film made of a metal film is gold (Au), platinum (Pt), silver (Ag), nickel (Ni), tantalum (Ta), tungsten (W), palladium (Pd). , Molybdenum (Mo), Tungsten (Ti) and Chromium (Cr) may be composed of a film formed of at least one of them. Further, the light-shielding film may be made of a metal oxide film. In this case, the metal oxide film is zirconium dioxide (ZrO).₂), Hafnium dioxide (HfO)₂), Titanium dioxide (TiO₂), Tantalum pentoxide (Ta₂O₅), Silicon oxide (SiO) and chromium oxide (Cr)₂O₃) Consists of a film formed by at least one of them.

In the above-described embodiments 1 to 33, an exposure apparatus that locally fills the space between the projection optical system PL and the substrate P with a liquid is adopted, as disclosed in Japanese Patent Application Laid-Open No. 6-124873. An immersion exposure device that moves a stage holding a substrate to be exposed is moved in a liquid tank, or a liquid tank having a predetermined depth is formed on the stage as disclosed in Japanese Patent Application Laid-Open No. 10-303114. The present invention can also be applied to an immersion exposure apparatus that holds a substrate therein.

Further, in the present invention, as disclosed in Japanese Patent Application Laid-Open No. 10-163099, Japanese Patent Application Laid-Open No. 10-214783, Japanese Patent Application Laid-Open No. 2000-505958, etc., substrates to be processed such as wafers are placed separately. It can also be applied to a twin-stage type exposure device equipped with two stages that can move independently in the XY directions.

In addition to the above description, the above-mentioned International Publication WO2004 / 019128, International Publication WO2004 / 053950, and International Publication WO2004 / 053951, which describe the configurations applicable to the exposure apparatus of the present invention, are referred to. It is incorporated herein by reference.

<p> Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.</p><p> [Example 1] FIG. 34 is a diagram showing the configuration of the optical element 50 of the present invention. As shown in FIG. 34, on the substrate of fluorite 52 in which the crystal orientation of the film-deposited surface 52a is the (111) plane, 0.55 of silicon oxide 54 as a dissolution prevention film of fluorite 52 is used by the RF sputtering method. The optical element 50 was formed by forming a film with an optical film thickness of λ (λ = 193 nm). Here, the optical film thickness of the silicon oxide film, by shown in FIG. 35 when sea urchin, the fluorite 52 light is incident from the direction of the solid arrow 56, and is reflected in the direction of the dashed arrow 58 by fluorite 52 In order to suppress the ghost phenomenon generated by the light remaining reflected from the substrate of the fluorite 52, it is necessary to be limited. That is, FIG. 36 is a diagram showing the residual reflectance of fluorite when light is incident on the fluorite substrate. The residual reflectance of fluorite when no silicon oxide film is formed on the fluorite substrate is shown by the solid line 60 in FIG. The residual reflectance of fluorite when a silicon oxide film is formed on the fluorite substrate is shown by the broken line 62 in FIG. As shown in FIG. 36, the optical thickness of the silicon oxide film is set so that the residual reflectance of the fluorite is 0.5% or less when the incident angle at which light is incident on the fluorite is 60 °. There is.</p><p> An experiment was conducted using the optical element 50. FIG. 37 is a diagram showing a configuration of an experimental device according to this embodiment. Put pure water 66 at 70 ° C into a water tank 64 made of polyetheretherketone (PEEK), which is large enough for the volume of the optical element 50. A stir bar 68 made of Teflon (registered trademark) is put into pure water 66. As shown in FIG. 37, the optical element 50 is put into pure water 66 so that only half of it is immersed in pure water 66. A water tank 64 including an optical element 50, pure water 66, and a stirrer 68 is placed in a constant temperature bath 70 to keep the temperature constant.</p><p> Here, the water tank 64 is sufficiently large with respect to the volume of the optical element 50 in order to reduce the change in the liquid level due to the evaporation of the pure water 66. Further, the stirrer 68 is used to keep the solubility constant even when the optical element 50 is dissolved in pure water 66 to generate a buffer solution. After 3 hours have passed with the optical element 50 immersed in pure water 66, the step between the optical element 50 in the portion not immersed in pure water 66 and the optical element 50 in the portion immersed in pure water 68 has a resolution of 0.5 nm. When measured with a step measuring device, no step was generated.</p><p> [Example 2] FIG. 38 is a diagram showing the configuration of the optical element 74 of the present invention. As shown in FIG. 38, on the substrate of fluorite 76 in which the crystal orientation of the film-forming surface 76a is the (111) plane, lanthanum fluoride 78 as a dissolution prevention film of fluorite 76 is formed by using a vacuum vapor deposition method. The optical element 74 was formed by forming a film with an optical film thickness of 0.68λ (λ = 193 nm). Lanthanum Fluoride 78 on the crystal orientation (111) plane of fluorite 76 is known to grow heteroepitaxially on the (111) plane reflecting the crystal orientation of fluorite 76 (see WO 03/009015). Therefore, the formed lanthanum fluoride 78 forms a crystal structure that is very dense and has very few defects.</p><p> An experiment was conducted using the optical element 74. Since the configuration of the experimental apparatus according to this embodiment is the same as the configuration of the experimental apparatus according to the first embodiment shown in FIG. 37, the same configuration will be described with the same reference numerals as those of the first embodiment.</p><p> First, pure water 66 at 70 ° C. is put into a water tank 64 which is sufficiently large with respect to the volume of the optical element 74, and the stirrer 68 is put into the pure water 66. The optical element 74 is put into pure water 66 so that only half of it is immersed in pure water 66. A water tank 64 including an optical element 74, pure water 66, and a stirrer 68 is placed in a constant temperature bath 70 to keep the temperature constant. After 3 hours have passed with the optical element 74 immersed in pure water 66, the step between the optical element 74 in the portion not immersed in pure water 66 and the optical element 74 in the portion immersed in pure water 66 has a resolution of 0.5 nm. When measured with a step measuring device, no step was generated.</p><p> In the above-described embodiment, the vacuum vapor deposition method was used as the film forming method of the dissolution prevention film in order to prepare a dense structure of the dissolution prevention film, but the dissolution prevention film was formed by using a sputtering method or a CVD method. A film may be formed.</p><p> [Comparative example 1] An experiment was conducted on a fluorite substrate on which no anti-dissolution film was formed. FIG. 39 is a diagram showing a configuration of an experimental device according to this comparative example. In this comparative example, the fluorite substrate 72 is used instead of the optical element 50 of the first embodiment. Since the configurations of the other experimental devices according to this comparative example are the same as the configurations of the experimental devices according to the first embodiment, the same configurations will be described with the same reference numerals as those of the first embodiment.</p><p> First, pure water 66 at 70 ° C. is put into a water tank 64 which is sufficiently large with respect to the volume of the fluorite substrate 72, and the stirrer 68 is put into the pure water 66. The fluorite substrate 72 is put into pure water 66 so that only half of it is immersed in pure water 66. A water tank 64 containing a fluorite substrate 72, pure water 66, and a stirrer 68 is placed in a constant temperature bath 70 to keep the temperature constant. After 3 hours have passed with the fluorite substrate 72 immersed in pure water 66, the step difference between the fluorite substrate 72 in the portion not immersed in pure water 66 and the fluorite substrate 72 in the portion immersed in pure water 66 is resolved. It was measured with a 0.5 nm step measuring device. Since the fluorite substrate 72 in the portion immersed in pure water 66 was dissolved, a step of 50 nm was measured.</p><p> According to the optical elements according to Examples 1 and 2, the solubility in pure water can be reduced to 1/50 or less when compared with the optical elements according to Comparative Example 1. FIG. 40 is a diagram showing the measurement result of the step measured by the step measuring device after the experiment of the optical element according to Comparative Example 1, Example 1 and Example 2. As shown in FIG. 40, fluorite formed with silicon oxide or lanthanum fluoride as a dissolution prevention film does not dissolve in pure water, so that no step is generated due to dissolution. Therefore, when the optical element is mounted on the portion of the projection exposure apparatus using the immersion method that comes into contact with the liquid, the transmitted wave surface of the projection optical system of the projection exposure apparatus can be maintained.</p><p> [Example 3] FIG. 41 is a diagram showing a configuration of the transmission optical element 50 according to the third embodiment. As shown in FIG. 41, tantalum (Ta) is formed into a 10 nm film on the substrate of fluorite 52 by a sputtering method to form an adhesion strengthening film 53. The adhesion strengthening film 53 functions to improve the adhesion between the fluorite 52 and the metal film 54 formed on the surface of the adhesion strengthening film 53. Further, although the film thickness required to strengthen the adhesion is 10 nm or more, the effect as the adhesion can be obtained even at a film thickness of 3 to 5 nm.</p><p> Next, a metal film 54 composed of gold (Au) is formed on the surface of the adhesion strengthening film 53 as a dissolution protective film for preventing dissolution in water by a sputtering method at 200 nm.</p><p> Here, the density of the metal film 54 can be obtained from the critical angle of X-ray diffraction, and when the film is formed by the sputtering method, the packing density of the metal film 54 is 97% or more. The solubility of the metal film 54 in water is 1 ppt or less when a film is formed by a sputtering method.</p><p> Next, silicon dioxide (SiO) is used as a dissolution prevention film protective film on the surface of the metal film 54 to improve the mechanical strength of the metal film 54 by using a sputtering method.₂) A 50 nm film is formed on the film 55.</p><p> An experiment was conducted using the transmission optical element 50. FIG. 42 is a diagram showing the configuration of the tester 80 according to this embodiment. As shown in FIG. 42, the tester 80 includes a sample holder 81, a circulation pump 82, a heavy water supply device 83, and a buffer tank 84. One side of the sample holder 81 is open, and an O-ring 85 is provided on the open side. Adhesion strengthening film 53, metal film 54, silicon dioxide (SiO) of transmission optical element 50 on the open surface of sample holder 81₂The surface on which the film 55 is formed is sealed by the O-ring 85. The heavy water supplied from the heavy water supply device 83 by the circulation pump 82 flows into the sample holder 81 via the buffer tank 84. Here, the buffer tank 84 is installed so that the vibration of the circulation pump 82 is not transmitted to the sample holder 81. Also, pure water (H₂Heavy water (D) instead of O)₂By flowing O), it is possible to measure the amount of heavy water permeating in the depth direction from the surface of the transmissive optical element 50 after the water resistance test.</p><p> The tester 80 was set so that the moving speed of heavy water on the transmission optical element 50 was 50 cm / sec, and a water resistance test was conducted for 30 days. As a result, the film formed on the surface of the transmission optical element 50 was not peeled off, and the appearance of the transmission optical element 50 was not changed. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmission optical element 50 by the secondary ion mass spectrometry (SIMS), the heavy water did not permeate into the metal film 54.</p><p> [Example 4] FIG. 43 is a diagram showing a configuration of the transmission optical element 58 according to the fourth embodiment. As shown in FIG. 43, a metal film 60 made of gold (Au) is formed on the substrate of the fluorite 59 by a sputtering method to form a 200 nm film as a dissolution protective film for preventing dissolution in water. Here, the density of the metal film 60 can be obtained from the critical angle of X-ray diffraction, and when the film is formed by the sputtering method, the packing density of the metal film 60 is 97% or more. The solubility of the metal film 60 in water is 1 ppt or less when a film is formed by a sputtering method.</p><p> Next, silicon dioxide (SiO) is used as a dissolution prevention film protective film on the surface of the metal film 60 to improve the mechanical strength of the metal film 60 by using a sputtering method.₂) A 50 nm film is formed on the film 61.</p><p> An experiment was conducted using the transmission optical element 58. Similar to Example 3, the tester 80 shown in FIG. 42 was set so that the moving speed of heavy water on the transmission optical element 58 was 50 cm / sec, and a water resistance test was conducted for 30 days. As a result, the film formed on the surface of the transmission optical element 58 was not peeled off, and the appearance of the transmission optical element 58 was not changed. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmission optical element 58 by the secondary ion mass spectrometry (SIMS), the heavy water did not permeate into the metal film 60.</p><p> [Example 5] FIG. 44 is a diagram showing a configuration of the transmission optical element 65 according to the fifth embodiment. As shown in FIG. 44, tantalum (Ta) is formed into a 10 nm film on the substrate of fluorite 66 by a sputtering method to form an adhesion strengthening film 67. The adhesion strengthening film 67 functions to improve the adhesion between the fluorite 66 and the metal film 68 formed on the surface of the adhesion strengthening film 67. Further, although the film thickness required to strengthen the adhesion is 10 nm or more, the effect as the adhesion can be obtained even at a film thickness of 3 to 5 nm.</p><p> Next, a metal film 68 composed of gold (Au) is formed on the surface of the adhesion strengthening film 67 as a dissolution protective film for preventing dissolution in water by a sputtering method at 200 nm.</p><p> Here, the density of the metal film 67 can be obtained from the critical angle of X-ray diffraction, and when the film is formed by the sputtering method, the packing density of the metal film 67 is 97% or more. The solubility of the metal film 67 in water is 1 ppt or less when a film is formed by a sputtering method.</p><p> An experiment was conducted using the transmission optical element 65. Similar to Example 3, the tester 80 shown in FIG. 42 was set so that the moving speed of heavy water on the transmission optical element 65 was 50 cm / sec, and a water resistance test was conducted for 30 days. As a result, the film formed on the surface of the transmission optical element 65 did not peel off, and the appearance of the transmission optical element 65 did not change. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmission optical element 65 by the secondary ion mass spectrometry (SIMS), the heavy water did not permeate.</p><p> In each of the above examples, the sputtering method was used as the film forming method, but the adhesion strengthening film, the metal film, and the dissolution prevention film protective film may be formed by using the vacuum vapor deposition method or the CVD method. ..</p><p> [Example 6] FIG. 45 is a diagram showing the configuration of the optical element 50 according to this embodiment. As shown in FIG. 45, magnesium fluoride (MgF) is formed on the surface 51A of the optical member 51 at the tip of the projection optical system formed of fluorite on the substrate side and the side surface 51B of the optical member 51.₂) Is wet-deposited using a spray coat. The surface 51A of the optical member 51 on the substrate side has an optical film thickness of 0.65λ (λ = 193 nm) and magnesium fluoride (MgF).₂) Is formed into a film. Here, the wet film forming method is a film forming method in which a substance to be formed is dispersed in a certain solvent, applied to the film forming surface, and the solvent is dried and removed after the application. As the solvent used, the substance to be formed may not be condensed or precipitated and may be dispersed in the solvent in a uniform state, and alcohol, an organic solvent or the like is used.</p><p> Magnesium fluoride (MgF) by wet film formation method₂) When forming a film, it is preferable to use the following three types of reaction processes. (i) Hydrofluoric acid / magnesium acetate method 2HF + Mg (CH)₃COO)₂ MgF₂+ 2CH₃COOH (ii) Hydrofluoric acid / alkoxide method 2HF + Mg (C₂H₅O)₂ MgF₂+ 2C₂H₅OH (iii) Trifluoroacetic acid / alkoxide method 2CF₃COOH + Mg (C₂H₅O)₂ Mg (CF)₃COO)₂+ 2C₂H₅OH Mg (CF)₃COO)₂ Pyrolysis MgF₂ In these processes, after preparing the sol solution, it is preferable to perform an organothermal treatment or a hydrothermal treatment as a pretreatment. At this time, either one or both of pressurization and heat aging may be performed. See US Pat. No. 5,835,275 for details of the wet method described above. As a method for applying the sol solution to the substrate, any one or more methods selected from a spin coating method, a dipping method, a meniscus method, a spray coating method, and a printing method are used. After the sol solution is applied, it is heated to remove organic substances and form a film. The formed film needs to protect the substrate-side surface 51A and the side surface 51B of the optical member 51 made of fluorite without gaps.</p><p> The film formed by the wet film forming method has much lower mechanical durability than the general dry film forming method typified by vacuum deposition or sputtering. Therefore, it is necessary to heat-anneal in order to improve the mechanical durability. In particular, when a film is formed on an optical member composed of fluorite by a wet film formation method, there is a risk that the fluorite will crack due to surface changes or extreme cases due to surface changes from the linear expansion coefficient of fluorite if annealing is performed due to a rapid temperature rise. There is sex. In order to avoid this, it is necessary to raise the temperature at a low speed.</p><p> In this example, magnesium fluoride (MgF) is used as the anti-dissolution film.₂) Was used, but not limited to this, silicon oxide (SiO)₂It goes without saying that a wet film formation using) is sufficient.</p><p> [Example 7] FIG. 46 is a diagram showing a configuration of an optical element 53 according to this embodiment. As shown in FIG. 46, silicon oxide (SiO) having an optical film thickness of 0.65λ (λ = 193nm) is formed on the surface 54A of the optical member 54 at the tip of the projection optical system formed of fluorite on the substrate side.₂) Is formed by ion beam sputtering. Then, the alkyl ketene dimer (AKD) is applied in a solution state to the side surface 54B of the optical member 54 in a heated state. When a liquid alkyl ketene dimer is crystallized, it becomes a fractal structure that repeatedly shows a small uneven shape in the concave-convex shape, and becomes a superhydrophobic film 56 having a contact angle of 160 ° or more.</p><p> This is the contact angle when a substance with a contact angle θ has a fractal structure r times the surface area._fThen, it is understood from the fact that the following formula, which is an extension of young's formula, holds.</p><p><maths num="1"><img file="JP4771300B2_D0010.tif" /></maths></p><p> Here γ_SIs the surface tension of a solid, γ_LIs the surface tension of the liquid, γ_SLIs the interfacial tension of solid / liquid. As shown in this equation, when cosθ is positive (θ&gt; 90 °), the contact angle is larger, that is, the liquid is more repelled, and when cosθ is negative (θ &lt;90 °), the contact angle is larger. Becomes smaller, that is, more wet with liquid.</p><p> Here, an alkyl ketene dimer having a fractal structure was used for the side dissolution prevention film, but it is water repellent by a general water repellent treatment such as a silane coupling agent (1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane). The side dissolution prevention effect can also be obtained by the treatment. Further, a water repellent treatment by general electroless plating may be used.</p><p> The verification results of the optical elements according to Examples 6 and 7 are shown below.</p><p> Magnesium fluoride (MgF) as a dissolution prevention film on the bottom surface of a rectangular parallelepiped fluorite optical element as shown in Fig. 47.₂) Is wet-formed by spray coating, and magnesium fluoride (MgF) is formed on the side surface as a dissolution prevention film.₂) Is wet-formed by spray coating. The optical element 57 shown in FIG. 47 is formed with the same anti-dissolution film as the anti-dissolution film of Example 6. The optical element shown in FIG. 47 is used as sample 1.</p><p> Silicon oxide (SiO) as a dissolution prevention film on the bottom surface of a rectangular parallelepiped fluorite optical element as shown in FIG.₂) Is formed by ion beam sputtering, and an alkyl ketene dimer solution is applied to the side surface as a dissolution prevention film and dried. The optical element 58 shown in FIG. 48 is formed with the same anti-dissolution film as the anti-dissolution film of Example 7. The optical element shown in FIG. 48 is used as sample 2.</p><p> Magnesium fluoride (MgF) as a dissolution prevention film on the bottom surface of a rectangular parallelepiped fluorite optical element as shown in Fig. 49.₂) Is wet-formed by spray coating, and the side surface is not coated. The optical element 59 shown in FIG. 49 is used as sample 3 (reference example 1).</p><p> The following experiments were performed on Samples 1, 2 and 3. FIG. 50 is a diagram showing the configuration of the experimental device. Put pure water 66 at 70 ° C into a water tank 64 made of polyetheretherketone (PEEK), which is large enough for the volume of the optical elements 57,58,59. A stir bar 68 made of Teflon (registered trademark) is put into pure water 66. As shown in FIG. 50, the optical elements 57, 58, 59 are put into pure water 66 so as to be immersed in pure water 66. A water tank 64 containing optical elements 57,58,59, pure water 66, and a stirrer 68 was placed in a constant temperature bath 70 to keep the temperature constant.</p><p> Here, the water tank 64 is sufficiently large with respect to the volume of the optical elements 57,58,59 in order to reduce the change in the liquid level due to the evaporation of the pure water 66. Further, the stirrer 68 is used to keep the solubility constant even when the optical elements 57, 58, 59 are dissolved in pure water 66 to generate a buffer solution. After 3 hours have passed with the optical elements 57,58,59 immersed in pure water 66, the steps due to melting at the bottom and side surfaces of the optical elements 57,58,59 are measured with a step measuring device with a resolution of 0.5 nm. did.</p><p> As shown in FIG. 51, the optical element 57 (sample 1) and the optical element 58 (sample 2) were not dissolved at all on the bottom surface and the side surface. On the other hand, in the optical element 59 (Sample 3), the side surface was eroded by about 50 nm. In addition, although the vicinity of the center of the bottom surface of the optical element 59 (Sample 3) did not change, the dissolution prevention film on the bottom surface was partially destroyed due to the erosion of the side surface of the periphery. ..</p><p> [Example 8] FIG. 53 is a diagram showing a configuration of the transmission optical element 50 according to the eighth embodiment. As shown in FIG. 53, silicon dioxide (SiO) was used on the substrate of fluorite 52 by a sputtering method.₂) A film 54 is formed at 200 nm.</p><p> Next, silicon dioxide (SiO) formed on the substrate of fluorite 52 by the sputtering method.₂) Silicon dioxide (SiO) on the surface of the film 54 using a wet film formation method by spin coating.₂) A 50 nm film is formed on the film 56. That is, a commercially available wet film-forming sol-gel silica solution is applied at a substrate rotation speed of 1000 to 2000 rotations / minute. In addition, silicon dioxide (SiO) by the wet film formation method₂) The film thickness of the film 56 depends on the concentration and viscosity of the wet film-forming sol-gel silica solution, the number of rotations of the substrate in spin coating, the temperature and humidity, etc. Silicon dioxide (SiO) with viscosity as a parameter₂) It is necessary to prepare a calibration curve of the concentration and viscosity of the wet film-forming sol-gel silica solution with respect to the film thickness of the film 56. In addition, silicon dioxide (SiO) by a wet film formation method is used to reduce the tensile stress of the film as much as possible.₂) The film thickness of the film 56 is 50 nm, but silicon dioxide (SiO)₂) If the film thickness of the film 56 is 150 nm or more, cracks may occur in the film due to stress relaxation, so care must be taken.</p><p> Next, the alcohol that is the main solvent of the wet film-forming sol-gel silica solution is evaporated, and the wet-filmed silicon dioxide (SiO).₂) Silicon dioxide (SiO) to sinter film 56₂) The membrane 56 is annealed in the atmosphere at 160 ° C for 2 hours. Annealing is performed in the atmosphere, and the entire substrate of fluorite 52 is heated evenly, so that no breakage or surface shape change occurs.</p><p> An experiment was conducted on the transmission optical element 50 using the tester 80 shown in FIG. 42. As shown in FIG. 42, the tester 80 includes a sample holder 81, a circulation pump 82, a heavy water supply device 83, and a buffer tank 84. One side of the sample holder 81 is open, and an O-ring 85 is provided on the open side. Silicon dioxide (SiO) of the transmission optical element 50 on the open surface of the sample holder 81₂The surface on which the films 54 and 56 are formed is sealed by the O-ring 85. The heavy water supplied from the heavy water supply device 83 by the circulation pump 82 flows into the sample holder 81 via the buffer tank 84. Here, the buffer tank 84 is installed so that the vibration of the circulation pump 82 is not transmitted to the sample holder 81. Also, pure water (H₂Heavy water (D) instead of O)₂By flowing O), it is possible to measure the amount of heavy water permeating in the depth direction from the surface of the transmissive optical element 50 after the water resistance test.</p><p> The tester 80 was set so that the moving speed of heavy water on the transmission optical element 50 was 50 cm / sec, and a water resistance test was conducted for 30 days. As a result, the film formed on the surface of the transmission optical element 50 was not peeled off, and the appearance of the transmission optical element 50 was not changed. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmission optical element 50 by the secondary ion mass spectrometry (SIMS), the heavy water did not permeate.</p><p> In Example 8, the sputtering method was used as the dry film forming method, but a film for preventing dissolution of the transmission optical element may be formed by using a vacuum vapor deposition method or a CVD method.</p><p> [Example 9] Next, the transmission optical element according to the ninth embodiment will be described. Magnesium fluoride (MgF) on a heated fluorite substrate using vacuum deposition₂) A film is formed at 70 nm. Magnesium fluoride (MgF) in vacuum₂) When the film is formed, the entire fluorite substrate is uniformly heated in order to prevent damage and surface shape change due to thermal shock of the fluorite substrate having a large coefficient of thermal expansion. Further, when heating or cooling the fluorite substrate, it is necessary to heat or cool at a low speed.</p><p> Next, magnesium fluoride (MgF) formed on the substrate of fluorite by the vacuum deposition method.₂) Silicon dioxide (SiO) on the surface of the film using a wet film formation method by spin coating.₂) A film is formed at 50 nm. That is, a commercially available wet film-forming sol-gel silica solution is applied at a substrate rotation speed of 1000 to 2000 rotations / minute. In addition, silicon dioxide (SiO) by the wet film formation method₂) The film thickness depends on the concentration and viscosity of the sol-gel silica solution for wet film formation, the number of rotations of the substrate in spin coating, temperature and humidity, etc., so the concentration and viscosity of the sol-gel silica solution for wet film formation in advance. Silicon dioxide (SiO) with₂) It is necessary to prepare a calibration curve of the concentration and viscosity of the wet film-forming sol-gel silica solution with respect to the film thickness. In addition, silicon dioxide (SiO) by a wet film formation method is used to reduce the tensile stress of the film as much as possible.₂) The film thickness is 50 nm, but silicon dioxide (SiO)₂) If the film thickness is 150 nm or more, cracks may occur in the film due to stress relaxation, so care must be taken.</p><p> Next, the alcohol that is the main solvent of the wet film-forming sol-gel silica solution is evaporated, and the wet-filmed silicon dioxide (SiO).₂) Silicon dioxide (SiO) to sinter the membrane₂) The membrane is annealed in the atmosphere at 160 ° C for 2 hours. Annealing is performed in the atmosphere, and the entire fluorite substrate is heated evenly, so that no damage or surface shape change occurs.</p><p> An experiment was conducted using the transmission optical element according to Example 9. Similar to Example 8, the tester 80 shown in FIG. 42 was set so that the moving speed of heavy water on the transmissive optical element according to Example 9 was 50 cm / sec, and a water resistance test was conducted for 30 days. .. As a result, the film formed on the surface of the transmissive optical element was not peeled off, and the appearance of the transmissive optical element was not changed. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmissive optical element by secondary ion mass spectrometry (SIMS), heavy water did not permeate.</p><p> In Example 9, the vacuum vapor deposition method was used as the dry film forming method, but a film for preventing dissolution of the transmission optical element may be formed by using a sputtering method or a CVD method.</p><p> [Example 10] FIG. 54 is a diagram showing a configuration of a transmission optical element 58 having an antireflection effect at a central wavelength of 193.4 nm according to Example 10. As shown in Figure 54, heated fluorite (CaF)₂) 1st layer of lanthanum fluoride (LaF) on the substrate of 59₃) Membrane 60, second layer magnesium fluoride (MgF)₂) Membrane 61, 3rd layer lanthanum fluoride (LaF)₃) The film 62 is formed by a vacuum vapor deposition method by resistance heating. Here, next, silicon dioxide (SiO) as the first film which is a part of the fourth layer.₂) The film 63 is formed by the vacuum vapor deposition method by heating with an electron gun to an optical film thickness of 0.08, and the fluorite 59 formed from the first layer to a part of the fourth layer is taken out from the vacuum chamber. Next, silicon dioxide (SiO)₂) Silicon dioxide (SiO) as the second film, which is part of the fourth layer, using a wet film formation method by spin coating on the film 63.₂) Apply 0.04 optical film thickness to film 64. Next, wet-formed silicon dioxide (SiO)₂) Silicon dioxide (SiO) to sinter the film of film 64₂) The membrane 64 is annealed in the atmosphere at 160 ° C for 2 hours. The refractive index n for a luminous flux having a central wavelength of 193.4 nm and the optical film thickness nd for a luminous flux having a central wavelength of 193.4 nm are shown below for the substrate and oxide film constituting the transmission optical element 58. Board: CaF₂(n = 1.50) First layer: LaF₃ (n = 1.69, nd = 0.60) Second layer: MgF₂(n = 1.43, nd = 0.66) Third layer: LaF₃(n = 1.69, nd = 0.52) Fourth layer: SiO₂(n = 1.55, nd = 0.12) Medium: H₂O (n = 1.44).</p><p> An experiment was conducted using the transmission optical element 58. Similar to Example 8, the tester 80 shown in FIG. 42 was set so that the moving speed of heavy water on the transmission optical element 58 was 50 cm / sec, and a water resistance test was conducted for 30 days. As a result, the film formed on the surface of the transmission optical element 58 was not peeled off, and the appearance of the transmission optical element 58 was not changed. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmission optical element 58 by the secondary ion mass spectrometry (SIMS), the heavy water did not permeate.</p><p> [Example 11] FIG. 55 is a diagram showing the configuration of the transmission optical element 65 according to the eleventh embodiment. As shown in FIG. 55, a surface treatment is applied to the substrate of fluorite 66. That is, it is polished with a # 2000 grindstone to increase the surface roughness and surface area of the fluorite 66. Further, silicon dioxide (SiO) as a dissolution-preventing oxide film is used by a wet film formation method by spin coating on a substrate of fluorite 66 which has been surface-treated by being polished with a grindstone.₂) The film 67 is applied to a film thickness of 100 nm. Next, wet-formed silicon dioxide (SiO)₂) Silicon dioxide (SiO) to sinter the film of film 67₂) The membrane 67 is annealed in the atmosphere at 160 ° C for 2 hours.</p><p> An experiment was conducted using the transmission optical element 65. Similar to Example 8, the tester 80 shown in FIG. 42 was set so that the moving speed of heavy water on the transmission optical element 65 was 50 cm / sec, and a water resistance test was conducted for 30 days. As a result, the film formed on the surface of the transmission optical element 65 did not peel off, and the appearance of the transmission optical element 65 did not change. Further, as a result of evaluating the permeation of heavy water in the depth direction from the surface of the transmission optical element 65 by the secondary ion mass spectrometry (SIMS), the heavy water did not permeate.</p><p> [Reference example 2] FIG. 56 is a diagram showing a configuration of a transmission optical element 73 having an antireflection effect at a center wavelength of 193.4 nm according to Reference Example 2. As shown in FIG. 56, a first layer of lanthanum fluoride (LaF) was placed on a substrate of heated fluorite 74.₃) Membrane 75, second layer magnesium fluoride (MgF)₂) Membrane 76, 3rd layer lanthanum fluoride (LaF)₃) The film 77 is formed by a vacuum vapor deposition method by resistance heating. Next, the fourth layer of silicon dioxide (SiO)₂) The film 78 is formed by the vacuum vapor deposition method by heating with an electron gun.</p><p> The first layer of lanthanum fluoride (LaF) constituting the transmission optical element 73 according to Reference Example 2₃) Membrane 75, second layer magnesium fluoride (MgF)₂) Membrane 76, 3rd layer lanthanum fluoride (LaF)₃The film 77 is a first layer of lanthanum fluoride (LaF) constituting the transmission optical element 58 according to the tenth embodiment.₃) Membrane 60, second layer magnesium fluoride (MgF)₂) Membrane 61, 3rd layer lanthanum fluoride (LaF)₃) It has the same refractive index and optical film thickness as the refractive index and optical film thickness of the film 62 with respect to the luminous flux having a central wavelength of 193.4 nm. In addition, the fourth layer of silicon dioxide (SiO)₂The film 78 is made of silicon dioxide (SiO) constituting the fourth layer according to Example 10.₂) Membrane 63 and silicon dioxide (SiO)₂) It has the same refractive index and optical film thickness as the refractive index and optical film thickness of the film 64 with respect to the luminous flux having a central wavelength of 193.4 nm.</p><p> An experiment was conducted using the transmission optical element 73. Similar to Example 8, the tester 80 shown in FIG. 42 was set so that the moving speed of heavy water on the transmission optical element 73 was 50 cm / sec, and a water resistance test was conducted for 30 days. After the water resistance test, the penetration of heavy water from the surface of the transmission optical element 73 in the depth direction was evaluated by secondary ion mass spectrometry (SIMS). As a result, a fourth film was formed on the surface of the transmission optical element 73. Layer silicon dioxide (SiO)₂) Inside the membrane 77 and the third layer of lanthanum fluoride (LaF)₃) Heavy water was detected near the interface with the membrane 76.</p><p> According to the transmission optical element according to the tenth embodiment, when compared with the transmission optical element according to the reference example 2, it is possible to prevent the permeation and erosion of heavy water without changing its optical characteristics. FIG. 57 is a diagram showing an angular reflection characteristic when light is incident on the transmission optical element according to Example 10 and Reference Example 2 from a medium (pure water). The solid line 90 in FIG. 57 shows the angular reflection characteristic of the S polarization component of the light incident on the transmission optical element according to Example 10 and Reference Example 2. Further, the broken line 91 in FIG. 57 shows the angular reflection characteristic of the P polarization component of the light incident on the transmission optical element according to Example 10 and Reference Example 2. As shown in FIG. 57, the angular reflection characteristics of the S-polarized light component and the P-polarized light component of the light incident on the transmitted optical element according to Example 10 and Reference Example 2 are the same, and the transmission according to Example 10 and Reference Example 2 It shows that the optical characteristics of the optical elements are the same.</p>

According to the present invention described above, when the immersion method is applied, it is possible to obtain an optical element in which the tip portion of the projection optical system is not eroded by the liquid. Therefore, according to the present invention, it is possible to obtain an exposure apparatus in which melting of the optical element is sufficiently prevented and the optical performance of the projection optical system is maintained for a long period of time.