Light source unit, illumination optical device, exposure device, and exposure method

The present invention relates to a light source unit, an illumination optical device, an exposure device, and an exposure method. More specifically, the present invention is a light source suitable for an exposure apparatus used for manufacturing a microdevice such as a semiconductor element in a photolithography process using EUV light (extreme ultraviolet light) having a wavelength of about 5 to 50 nm. It is about the unit.

In this type of exposure apparatus, further improvement in resolving power is required as the circuit pattern to be transferred becomes finer, and light having a shorter wavelength is used as the exposure light. The term "light" as used herein means not only "light" in the narrow sense that can be seen by the eye, but also "light" in the broad sense that includes so-called infrared rays to X-rays that have a wavelength shorter than 1 mm among electromagnetic waves. To do. In recent years, as a next-generation device, an exposure device using EUV (Extreme UltraViolet) light having a wavelength of about 5 to 50 nm (hereinafter referred to as "EUVL (Extreme UltraViolet Lithography) exposure device") has been proposed.

Currently, the following three types of light sources have been proposed as light sources for supplying EUV light. (1) Light source that supplies SR (synchrotron radiation) (2) LPP (Laser Produced Plasma) light source (3) DPP (Discharge Produced Plasma) light source.

In the LPP light source (laser plasma light source), the laser light is focused on the target material (target material), and the target material is turned into plasma to obtain EUV light. On the other hand, in the DPP light source (discharge plasma light source), when a voltage is applied between the electrodes in a state where the target material exists between the electrodes, a discharge occurs between the electrodes when a certain voltage is exceeded, and the target material becomes plasma. A large current flows between the electrodes due to this discharge, and the magnetic field generated by this large current compresses the plasma itself into a minute space, and the plasma temperature rises. EUV light is emitted (radiated) from this high-temperature plasma.

<p> In a DPP light source, the plasma generation position (that is, the light emitting position) may change over time due to electrode wear caused by, for example, long-term operation. Further, in the LPP light source, when it is operated for a long time, the nozzle is deformed or consumed due to the influence of ions from plasma generated in the vicinity of the nozzle that supplies the target material. As a result, the supply path of the target material may change over time due to deformation or wear of the nozzle, and eventually the plasma generation position may change over time.</p><p> Alternatively, in the LPP light source, the focusing position of the laser light may change with time, and thus the plasma generation position may change with time. In a DPP light source or LPP light source, when the plasma generation position changes, the angular distribution (in-plane distribution) of the light intensity of the EUV light radiated from the plasma and incident on the reflector (condensing mirror) changes, and eventually from the light source unit. The angular distribution of the light intensity of the supplied EUV light changes.</p><p> In addition, when replacing worn electrodes, nozzles, or reflectors, new parts cannot be mounted accurately in their original positions, and replacement mounting errors may occur. In this case, plasma is generated at a position different from that before the replacement of the component, or the position where the EUV light is focused through the reflector, that is, the focusing position is deviated from the focusing position before the replacement of the component. As described above, when the plasma generation position or the condensing position changes, that is, when the light source position changes, the illumination conditions change, and when applied to an exposure apparatus, accurate exposure cannot be performed.</p><p> The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a light source unit capable of stably supplying EUV light having a desired light intensity angle distribution (in-plane distribution). .. Another object of the present invention is to provide a light source unit capable of stably maintaining a light emitting position (plasma generation position) and a condensing position at substantially a predetermined position. Further, the present invention uses a light source unit that stably supplies EUV light having a desired light intensity angle distribution (in-plane distribution) or a light source unit that stably maintains a light emitting position and a condensing position at substantially a predetermined position. It is an object of the present invention to provide an exposure apparatus and an exposure method capable of faithfully transferring a mask pattern onto a photosensitive substrate under desired illumination conditions.</p>

<p> In order to solve the above-mentioned problems, in the first embodiment of the present invention, a light source main body that radiates EUV light from the generated plasma by converting the target material into plasma and an EUV light radiated from the light source main body are directed in a predetermined direction. Based on the reflector for reflection, the detection system for detecting the axial symmetry of the angular distribution (in-plane distribution) of the light intensity of the EUV light incident on the reflector, and the detection result of the detection system. Provided is a light source unit including an adjustment system for adjusting the light source body so that the angular distribution (in-plane distribution) of the light intensity is substantially axially symmetric.</p><p> According to a preferred embodiment of the first embodiment, the detection system has a plurality of photodetectors arranged around the reflector. In this case, it is preferable that the detection system further includes a plurality of mirrors for reflecting only the EUV light having a predetermined wavelength among the light reaching the periphery of the reflector from the light source main body and guiding the light to each light detector. Alternatively, it is preferable that the detection system further includes a plurality of selection filters for transmitting only EUV light having a predetermined wavelength from the light reaching the periphery of the reflector from the light source main body and guiding the light to each photodetector.</p><p> According to a preferred embodiment of the first embodiment, the light source body is for irradiating a nozzle for supplying the target material and a laser beam for condensing the target material supplied from the nozzle. It has a laser irradiation system, and the adjustment system has a focusing position changing means for changing the focusing position of the laser light. Alternatively, the light source body has a nozzle for supplying the target material and a laser irradiation system for irradiating the target material supplied from the nozzle with laser light so as to concentrate the light. The adjusting system preferably has a nozzle adjusting means for adjusting the position and orientation of the nozzle and a focusing position changing means for changing the focusing position of the laser beam. In these cases, it is preferable that the condensing position changing means has a parallel flat plate that is arranged in the optical path of the laser irradiation system and can be tilted with respect to the optical axis.</p><p> According to a preferred embodiment of the first embodiment, the light source body has a pair of electrodes for plasmaizing the target material by electric discharge, and the adjusting system rotates the pair of electrodes around the discharge axis at the time of electric discharge. It has an electrode driving means for causing the electric discharge.</p><p> In the second embodiment of the present invention, a light source main body that converts the target material into plasma and radiates EUV light from the generated plasma, and reflection for reflecting the EUV light radiated from the light source main body and condensing it at a predetermined position. A detection system for detecting the axial symmetry of the light intensity angular distribution (in-plane distribution) of the UV light through the mirror and the predetermined position, and the light intensity angle based on the detection result of the detection system. Provided is a light source unit including an adjustment system for adjusting the position and orientation of the reflector so that the distribution (in-plane distribution) is substantially axially symmetric.</p><p> According to a preferred embodiment of the second embodiment, the detection system has a plurality of photodetectors arranged around an effective luminous flux of EUV light through the predetermined position. In this case, the detection system further includes a plurality of selection filters for transmitting only EUV light having a predetermined wavelength from the light reaching the periphery of the effective luminous flux from the light source main body and guiding the light to each photodetector. Alternatively, it is preferable that the detection system further includes a plurality of mirrors for reflecting only EUV light having a predetermined wavelength among the light reaching the periphery of the effective light flux from the light source main body and guiding the light to each photodetector.</p><p> According to a preferred embodiment of the second embodiment, the light source body is for irradiating a nozzle for supplying the target material and a laser beam for condensing the target material supplied from the nozzle. It has a laser irradiation system, and the adjustment system has a focusing position changing means for changing the focusing position of the laser light. Alternatively, the light source body has a nozzle for supplying the target material and a laser irradiation system for irradiating the target material supplied from the nozzle with laser light so as to concentrate the light. The adjusting system preferably has a nozzle adjusting means for adjusting the position and orientation of the nozzle and a focusing position changing means for changing the focusing position of the laser beam. In these cases, it is preferable that the condensing position changing means has a parallel flat plate that is arranged in the optical path of the laser irradiation system and can be tilted with respect to the optical axis.</p><p> According to a preferred embodiment of the second embodiment, the light source body has a pair of electrodes for plasmaizing the target material by electric discharge, and the adjusting system rotates the pair of electrodes around the discharge axis at the time of electric discharge. It has an electrode driving means for causing the electric discharge.</p><p> In the third embodiment of the present invention, a light source main body that converts the target material into plasma and radiates EUV light from the generated plasma, and a reflector for reflecting and condensing the EUV light radiated from the light source main body. A detection system for detecting the light collection position of the EUV light reflected by the reflector, and an adjustment system for adjusting the light collection position so as to be substantially a predetermined position based on the detection result of the detection system. Provided is a light source unit characterized by having and.</p><p> According to a preferred embodiment of the third embodiment, the detection system has a two-dimensional photodetector arranged at the predetermined position. Further, it is preferable that the adjusting system has a reflecting mirror adjusting means for adjusting the position and orientation of the reflecting mirror. Further, it is preferable that the adjusting system has a light emitting position changing means for changing the emitting position of EUV light from the plasma.</p><p> According to a preferred embodiment of the third embodiment, the light source body is for irradiating a nozzle for supplying the target material and a laser beam for condensing the target material supplied from the nozzle. It has a laser irradiation system, and the light emitting position changing means includes a nozzle adjusting means for adjusting the position and orientation of the nozzle and a focusing position changing means for changing the focusing position of laser light. .. In this case, it is preferable that the condensing position changing means has a parallel flat plate that is arranged in the optical path of the laser irradiation system and can be tilted with respect to the optical axis. Further, it is preferable that the condensing position changing means has a lens that is arranged in the optical path of the laser irradiation system and can move along the optical axis.</p><p> According to a preferred embodiment of the third embodiment, the light source main body has a pair of electrodes for converting the target material into plasma by electric discharge, and the light emitting position changing means changes the position of the pair of electrodes. It has a means for changing the electrode position of.</p><p> In the fourth embodiment of the present invention, the target material is turned into plasma by the discharge between the pair of electrodes, and the light source main body that radiates the EUV light from the generated plasma and the EUV light radiated from the light source main body are reflected in a predetermined direction. Based on the light source for detecting the light emitting position of the EUV light from the plasma, the detection system for detecting the light emitting position of the EUV light from the plasma, and the detection result of the detection system, the pair of electrodes so that the light emitting position is substantially set to a predetermined position. Provided is a light source unit characterized by having an adjustment system for adjusting the position of the light source.</p><p> According to a preferred embodiment of the fourth embodiment, the detection system has a plurality of two-dimensional photodetectors for detecting light from the plasma via pinholes.</p><p> The fifth aspect of the present invention is characterized by including the light source units of the first to fourth forms and a light guide optical system for guiding EUV light from the light source unit to the irradiated surface. Provide an optical device.</p><p> In the sixth embodiment of the present invention, a light source main body that converts the target material into plasma and radiates EUV light from the generated plasma, and a reflector for reflecting and condensing the EUV light radiated from the light source main body. A collimeter mirror for converting EUV light once condensed by the reflector into substantially parallel light, an optical integrator arranged between the collimeter mirror and the irradiated surface, and EUV light incident on the optical integrator. Based on the detection system for detecting the axial symmetry of the angular distribution (in-plane distribution) of the light intensity and the detection result of the detection system, the angular distribution (in-plane distribution) of the light intensity becomes almost axially symmetric. Provided is an illumination optical device including an adjustment system for adjusting so as to be.</p><p> According to a preferred embodiment of the sixth embodiment, the optical integrator has a first fly-eye mirror and a second fly-eye mirror in order from the collimator mirror side, and the detection system receives the incident of the EUV light. It has an ammeter for detecting the photoelectron current emitted from the element mirror of the first fly-eye mirror. Further, it is preferable that the adjusting system has a reflecting mirror adjusting means for adjusting the position and orientation of the reflecting mirror. Further, it is preferable that the adjusting system has a mirror adjusting means for adjusting the position and orientation of the collimator mirror.</p><p> In the seventh aspect of the present invention, the illumination optical device of the fifth or sixth form for illuminating the reflective mask on which a predetermined pattern is formed and the pattern image of the mask are formed on the photosensitive substrate. Provided is an exposure apparatus characterized by comprising a projection optical system for the purpose. In this case, it is preferable to move the mask and the photosensitive substrate relative to the projection optical system along a predetermined direction to project and expose the mask pattern onto the photosensitive substrate.</p><p> In the eighth aspect of the present invention, the illumination step of illuminating the reflective mask in which a predetermined pattern is formed by using the illumination optical device of the fifth or sixth form, and the pattern of the mask via the projection optical system. The present invention provides an exposure method including an exposure step of projecting and exposing the image onto the photosensitive substrate. In this case, in the exposure step, it is preferable to move the mask and the photosensitive substrate relative to the projection optical system along a predetermined direction to project and expose the mask pattern onto the photosensitive substrate.</p>

<p> In the present invention, the angular distribution (in-plane distribution) of the light intensity of the EUV light incident on the reflector and the EUV light once collected and emitted by the reflector may become substantially axisymmetric due to various causes. However, it can be adjusted so that the angular distribution of light intensity is substantially axisymmetric. Further, in the present invention, even if the collecting position of the EUV light reflected by the reflector and the emitting position of the EUV light from the plasma may change due to various causes, the collecting position and the emitting position are set to a predetermined position. Can be adjusted to be.</p><p> That is, in the light source unit of the present invention, EUV light having a desired light intensity angular distribution (in-plane distribution) can be stably supplied, and the light emitting position (plasma generation position) and the condensing position can be stably set to substantially predetermined positions. Can be maintained at. Therefore, in the exposure apparatus and the exposure method of the present invention, the light source unit or the light emitting position and the condensing position that stably supply the EUV light having a desired light intensity angle distribution (in-plane distribution) are stably set to substantially predetermined positions. By using the maintained light source unit, the mask pattern can be faithfully transferred onto the photosensitive substrate under the desired illumination conditions, and thus a high-precision microdevice can be manufactured with high throughput.</p>

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing an overall configuration of an exposure apparatus including a light source unit according to an embodiment of the present invention. Further, FIG. 2 is a diagram showing the positional relationship between the static exposure region formed on the wafer and the optical axis. In FIG. 1, the Z-axis is along the optical axis direction of the projection optical system, that is, the normal direction of the wafer W, which is a photosensitive substrate, and the Y-axis is in the plane of the wafer W in the direction parallel to the paper surface of FIG. The X-axis is set in the direction perpendicular to the paper surface of Fig. 1 in the W plane.

Referring to FIG. 1, the exposure apparatus of the present embodiment includes a DPP light source type light source unit 1 or an LPP light source type light source unit 2 for supplying exposure light. The exposure light supplied from the light source unit 1 or 2, for example, the EUV light (X-ray) L having a wavelength of 13.5 nm (or 11.5 nm), is a pattern to be transferred via the illumination optical system 3 and the plane reflector 4. Illuminates the reflective mask (reticle) M on which is formed. The mask M is held by a mask stage 5 that is movable along the Y direction so that its pattern plane extends along the XY plane.

The movement of the mask stage 5 is configured to be measured by the laser interferometer 6. The light from the illuminated mask M pattern forms an image of the mask pattern on the wafer W, which is a photosensitive substrate, via the reflective projection optical system PL. That is, as shown in FIG. 2, an arc-shaped exposure region (that is, a static exposure region or an effective exposure region) ER that is symmetrical with respect to the Y axis and extends in the X direction is formed on the wafer W.

With reference to FIG. 2, in the circular region (image circle) IF centered on the optical axis AX, an arc-shaped static exposure region ER is set so as to be in contact with the image circle IF. The wafer W is held by a wafer stage 7 that is two-dimensionally movable along the X and Y directions so that its exposed surface extends along the XY plane. The movement of the wafer stage 7 is configured to be measured by the laser interferometer 8 as in the mask stage 5.

In this way, scan exposure (scan exposure) is performed while moving the mask stage 5 and the wafer stage 7 along the Y direction, that is, moving the mask M and the wafer W relative to the projection optical system PL along the Y direction. As a result, the pattern of the mask M is transferred to one shot region of the wafer W. Further, by repeating the scanning exposure while moving the wafer stage 7 two-dimensionally along the X direction and the Y direction, the pattern of the mask M is sequentially transferred to each shot region of the wafer W.

FIG. 3 is a diagram schematically showing the internal configuration of the DPP light source type light source unit. Referring to FIG. 3, the DPP light source type light source unit 1 includes a light source body 11, a concave reflector 12, and a chamber 13 that houses the light source body 11 and the concave reflector 12. The light source main body 11 has a pair of electrodes 11a and 11b provided on the partition wall 13a of the chamber 13 and a power supply source 11c for applying a pulsed high voltage between the pair of electrodes 11a and 11b spaced apart from each other. Have.

In the light source main body 11, for example, between the first electrode 11a having a cylindrical shape and the second electrode 11b having a concentric cylindrical shape surrounding the first electrode 11a, from a gas supply source (not shown). Xenon (Xe) gas 11d is supplied. When a pulse high voltage from the power supply source 11c is applied between the first electrode 11a and the second electrode 11b while the xenon gas 11d as the target gas (target material) is supplied, the first electrode 11a and A discharge occurs between the second electrode 11b and the second electrode 11b. This discharge ionizes the xenon gas 11d to generate plasma, and the generated plasma is converged by electromagnetic force to form a high-temperature, high-density plasma P, and EUV light is radiated from this plasma P. As the target, for example, tin (Sn) or the like can be used.

The concave reflector 12 has a reflecting surface 12a having a concave shape (spherical shape, aspherical shape, spheroidal shape, etc.) and is attached to the partition wall 13a of the chamber 13. The concave reflector 12 is mounted on a reflector body 12b made of a metal having high workability and high thermal conductivity, such as nickel (Ni), aluminum (Al), copper (Cu), and silicon (Si). , It is formed by coating a multilayer film 12a made of Mo / Si, for example, as a reflective surface.

The multilayer film 12a has a property of selectively reflecting EUV light having a wavelength of 13.5 nm and preventing deterioration and deformation of the optical surface. On the back surface side of the concave reflector 12, a cooling mechanism 14 for cooling the concave reflector 12 whose temperature tends to rise due to radiant heat from the light source main body 11 is attached. In the cooling mechanism 14, for example, due to the action of a circulating refrigerant (water, oil, gas, etc.), the heat transferred from the reflective surface 12a of the concave reflector 12 through the reflector body 12b having high thermal conductivity is efficiently transferred to the outside. It is discharged.

The EUV light radiated from the light source body 11 is reflected by the concave reflector 12 toward the pair of electrodes (11a, 11b) and focused on the predetermined position P1 of the opening 15 formed in the partition wall 13a of the chamber 13. To do. The EUV light once condensed is guided to the outside of the chamber 13 through the opening 15 and is incident on the selection filter 16 arranged in the vicinity of the opening 15. The selection filter 16 is a thin film formed of zirconium (Zr), silicon (Si), silicon nitride (SiN), etc., which blocks visible light and ultraviolet light from the light source body 11 and has a desired wavelength of 13.5 nm. It has the property of selectively transmitting EUV light.

A vacuum exhaust device 17 such as a vacuum pump is connected to the chamber 13. Due to the action of the vacuum exhaust device 17, a substantially vacuum atmosphere is formed inside the chamber 13. Similarly, in order to suppress the attenuation of EUV light, a substantially vacuum atmosphere is formed in all the optical paths from the light source unit 1 through the illumination optical system 3 and the projection optical system PL to the wafer W. Not limited to the vacuum atmosphere, a reduced pressure atmosphere filled with an appropriate inert gas can be formed in all the optical paths. The target gas 11d supplied between the pair of electrodes (11a, 11b) is discharged to the outside of the chamber 13 by the action of the vacuum exhaust device 17 after the plasma P is generated.

The relatively small opening 15 formed in the partition wall 13a of the chamber 13 is used for differential exhaust that separates the low vacuum degree on the light source unit 1 side and the high vacuum degree on the subsequent illumination optical system 3 side in the chamber 13. Will be done. Due to this differential exhaust, even if the degree of vacuum on the light source unit 1 side is low, the degree of vacuum on the downstream side of the opening 15 is kept good. When the differential exhaust by the opening 15 is insufficient, it is effective to arrange the selection filter 16 in the vicinity of the opening 15 and use it for the differential exhaust. However, if the differential exhaust by the opening 15 is sufficient, or if the visible light and the ultraviolet light reaching the opening 15 from the light source main body 11 can be ignored, the installation of the selection filter 16 can be omitted.

In the light source unit 1 of the DPP light source type S of the present embodiment, a pulse high voltage from the power supply source 11c is applied between the first electrode 11a and the second electrode 11b while the xenon gas 11d is supplied. As a result, EUV light is radiated from the plasma P generated by the discharge between the pair of electrodes 11a and 11b. The EUV light radiated from the plasma P is incident on the concave reflecting mirror 12, and is reflected by the multilayer film reflecting surface 12a toward the pair of electrodes (11a, 11b). The EUV light of the desired wavelength (13.5 nm) selectively reflected by the multilayer film reflecting surface 12a of the concave reflecting mirror 12 is once focused on the predetermined position P1 of the opening 15, and further wavelength-selected through the selection filter 16. After that, it is incident on the illumination optical system 3 as EUV light L.

FIG. 4 is a diagram schematically showing the internal configuration of the LPP light source type light source unit. Referring to FIG. 4, the LPP light source type light source unit 2 is arranged at a predetermined position inside the vacuum container (chamber) 21, the vacuum pump (vacuum exhaust device) 22 connected to the vacuum container 21, and the vacuum container 21. The gas jet nozzle 23 and the concave reflector 24 attached to the partition wall of the vacuum vessel 21 are provided.

The inside of the vacuum vessel 21 is exhausted by the action of the vacuum pump 22, and is set to a substantially vacuum state so that the EUV light radiated from the plasma P, which will be described later, is not attenuated. Similarly, in order to suppress the attenuation of EUV light, all the optical paths from the light source unit 2 through the illumination optical system 3 and the projection optical system PL to the wafer W are set to a substantially vacuum state. The vacuum atmosphere is not limited, and a reduced pressure atmosphere filled with an appropriate inert gas can be formed in all the optical paths.

The gas jet nozzle 23 is made of, for example, stainless steel and is connected to a gas cylinder (not shown) filled with a target gas such as xenon (Xe) gas. The target gas in the gas cylinder is injected from the gas jet nozzle 23 into the inside of the vacuum vessel 21 via a pipe, a valve, or the like. The target gas 23a injected from the gas jet nozzle 23 along a predetermined path serves as a target material when generating plasma P. As the target, for example, tin (Sn) or the like can be used.

The concave reflector 24 has, for example, a spheroidal reflecting surface 24a, and is attached to the partition wall of the vacuum vessel 21. The concave reflector 24 is positioned so that its first focal position substantially coincides with a predetermined position where plasma P should be generated, and the reflecting surface 24a is located inside the vacuum vessel 21 and has a back surface (opposite to the reflecting surface 24a). Surface) is exposed to the outside atmosphere side of the vacuum vessel 21. The concave reflector 24 is formed by coating, for example, a Mo / Si multilayer film 24a as a reflecting surface on a reflecting mirror main body 24b formed of, for example, low thermal expansion glass (Zero Duer, ULE, etc.).

However, the multilayer film 24a as a reflecting surface is formed in a region excluding the central transmission region 24c on the surface of the concave reflecting mirror 24. The multilayer film 24a has a property of selectively reflecting EUV light having a wavelength of 13.5 nm and preventing deterioration and deformation of the optical surface. Specifically, for example, the uppermost layer of a multilayer film is coated with ruthenium (Ru) to reduce organic pollution and oxidation. On the back surface side of the concave reflector 24, a cooling mechanism 25 for cooling the concave reflector 24 whose temperature tends to rise due to radiant heat from the plasma P is attached. In the cooling mechanism 25, for example, due to the action of a circulating refrigerant (water, oil, gas, etc.), the heat transferred from the reflecting surface 24a of the concave reflecting mirror 24 through the reflecting mirror main body 24b is discharged to the outside.

Further, the light source unit 2 includes a laser light source 26 arranged on the back surface side of the concave reflector 24 at intervals, and a lens 27 arranged in the optical path between the laser light source 26 and the concave reflector 24. There is. For example, the laser light source 26 and the lens 27 such as the YAG laser light source are arranged along the optical axis of the concave reflector 24 and thus the optical axis of the light source unit 2. The laser light supplied from the laser light source 26 is subject to the focusing action of the lens 27, and is on the optical axis on which plasma P should be generated in the vicinity of the gas jet nozzle 23 via the central transmission region 24c of the concave reflector 24. Focuses on the position, that is, at or near the first focal point of the concave reflector 24.

In this way, the laser light source 26 and the lens 27 constitute a laser irradiation system for irradiating the laser beam so as to condense the target gas 23a supplied from the gas jet nozzle 23. The laser light supplied from the laser light source 26 is focused on the target gas 23a ejected from the gas jet nozzle 23 along a predetermined path, so that plasma P is generated at or near the focused position of the laser light. , EUV light is radiated from this plasma P. That is, the laser irradiation system (26, 27) and the gas jet nozzle 23 constitute a light source main body that turns the target gas 23a into plasma and radiates EUV light from the generated plasma P.

The target gas 23a injected from the gas jet nozzle 23 is discharged to the outside of the vacuum vessel 21 by the action of the vacuum pump 22 after the plasma P is generated. Further, the reflector body 24b is not a transparent material such as low thermal expansion glass, but has high workability and thermal conductivity such as nickel (Ni), aluminum (Al), copper (Cu), and silicon (Si). It can also be formed of high metal to increase cooling efficiency. However, in this configuration, an opening is provided in a portion corresponding to the central transmission region 24c through which the laser light from the laser light source 26 passes, and a light-transmitting optical member (for example, a window member made of quartz) is provided in this opening. Need to be installed.

Further, the light source unit 2 includes a selection filter 28 and a pinhole member 29 arranged at positions facing the concave reflector 24 inside the vacuum vessel 21. The selection filter 28 is a thin film formed of zirconium (Zr), silicon (Si), silicon nitride (SiN), etc., which blocks visible light and ultraviolet light from plasma P and EUV having a desired wavelength of 13.5 nm. It has the property of transmitting light. The selection filter 28 may be arranged on the front side of the pinhole member 29 as shown in FIG. 4, or may be arranged on the rear side of the pinhole member 29.

On the other hand, the pinhole member 29 is arranged so that the center of the pinhole 29a substantially coincides with the second focal position of the concave reflector 24, and the unwanted light scattered by the concave reflector 24 and the reflection of the concave reflector 24 are reflected. It has a function of blocking unnecessary light directly incident from the plasma P without being reflected by the surface 24a. Further, the pinhole member 29 is used for differential exhaust that separates the low vacuum degree on the upstream side of the pinhole 29a, that is, the light source unit 2 side, and the high vacuum degree on the downstream side of the pinhole 29a, that is, the illumination optical system 3 side. To. Due to this differential exhaust, even if the degree of vacuum on the light source unit 2 side is low, the degree of vacuum on the downstream side of the pinhole member 29 is kept good.

In the light source unit 2 of the LPP light source type S of the present embodiment, the laser light supplied from the laser light source 26 passes along a predetermined path from the gas jet nozzle 23 via the central transmission region 24c of the lens 27 and the concave reflector 24. Condenses on the injected target gas 23a. The target gas 23a ejected from the gas jet nozzle 23 at supersonic speed receives the energy of the focused laser light and becomes high in temperature, and generates plasma P at or near the first focal position of the concave reflector 24. EUV light is emitted (radiated) from the plasma P when the ions in the plasma P transition to the low potential state.

The EUV light radiated from the plasma P is incident on the concave reflector 24 and is reflected toward the plasma P side by the multilayer film reflecting surface 24a. The UV light of the desired wavelength (13.5 nm) selectively reflected by the multilayer film reflecting surface 24a of the concave reflecting mirror 24 is further wavelength-selected via the selection filter 28, and the position of the pinhole 29a of the pinhole member 29 or After condensing light at a predetermined position P1 in the vicinity thereof, it is incident on the illumination optical system 3 as EUV light L.

FIG. 5 is a diagram schematically showing the internal configurations of the illumination optical system and the projection optical system. Referring to FIG. 5, the EUV light L supplied from the DPP light source type light source unit 1 or the LPP light source type light source unit 2 becomes a substantially parallel luminous flux through the collimator mirror (concave reflector) 31, and a pair of fly eyes. It is incident on the optical integrator 32 consisting of mirrors 32a and 32b. As the pair of fly-eye mirrors 32a and 32b, for example, the fly-eye mirrors disclosed in Japanese Patent Application Laid-Open No. 11-312638 of the present applicant can be used. For a more detailed configuration and operation of the fly-eye mirror, the related description in the same publication can be referred to.

In this way, a substantially surface light source having a predetermined shape is formed in the vicinity of the reflection surface of the second fly-eye mirror 32b, that is, in the vicinity of the injection surface of the optical integrator 32. The light from the substantial surface light source is deflected by the plane reflector 4 and then forms an elongated arcuate illumination region on the mask M. The light from the illuminated mask M pattern forms an image of the mask pattern on the wafer W via the projection optical system PL consisting of a plurality of reflectors (exemplarily six reflectors M1 to M6 in FIG. 4). Form.

The basic configurations of the DPP light source type light source unit 1, the LPP light source type light source unit 2, and the illumination optical system 3 according to the present embodiment have been described above. Hereinafter, the characteristic configurations of the DPP light source type light source unit 1 and the LPP light source type light source unit 2 of the present embodiment will be described with reference to the first to fourth embodiments. In addition, the characteristic configuration of the illumination optical device (1,3; 2,3) of the present embodiment will be described with reference to the fifth embodiment.

[First Example]

FIG. 6 is a diagram schematically showing the configuration of a detection system that detects the axial symmetry of the angular distribution of the light intensity of EUV light incident on the concave reflector in the first embodiment. FIG. 7 is a diagram schematically showing the configuration of an adjustment system that adjusts the light source body so that the angular distribution of light intensity is substantially axisymmetric based on the detection result of the detection system of FIG. Referring to FIG. 6 (a), the detection system according to the first embodiment has four detection units 61 to 64 arranged around the concave reflector (12; 24) (63 and 64 in FIG. 6 (a)). Is not shown) and a control unit 65 to which outputs from the detection units 61 to 64 are supplied.

The four detection units 61 to 64 have the same basic configuration as each other, and are arranged at positions substantially rotationally symmetric with respect to the optical axis of, for example, a concave reflector (12; 24). As an example, as shown in FIG. 6 (b), the first detection unit 61 includes a photodetector 61a such as a photodiode and a concave reflector (12;) from the light source body (11; 23,26,27). It has a multilayer mirror 61b that reflects only EUV light of a predetermined wavelength (13.5 nm) out of the light reaching the surroundings of 24) and guides it to the photodiode 61a.

Alternatively, in another embodiment, the first detection unit 61 is of the photodiode 61a and the light source body (11; 23,26,27) to the concave reflector (12; 24), as shown in FIG. 6 (c). It has a selection filter 61c that transmits only EUV light near a predetermined wavelength (13.5 nm) among the light that reaches the surroundings and guides it to the photodiode 61a. Here, the multilayer mirror 61b has the same characteristics as the multilayer film forming the reflecting surface (12a; 24a) of the concave reflector (12:24), and the selection filter 61c is the same as the selection filter (16; 28). It has the characteristics of. Alternatively, when the reflecting surface of the concave reflecting mirror (12:24) is radially divided into a plurality of parts (a plurality of mirror substrates may be used, or a plurality of multilayer films formed on one substrate may be formed in a plurality of layers. The EUV light intensity distribution may be monitored by measuring the photoelectrons emitted from the individual reflecting surfaces or the photoelectron flow flowing through the individual reflecting surfaces (which may be divided).

In the first embodiment, the outputs from the detection units 61 to 64 are supplied to the control unit 65, respectively. The control unit 65 detects the axial symmetry of the angular distribution (in-plane distribution) of the light intensity of the EUV light incident on the concave reflector (12; 24) based on the outputs from the detection units 61 to 64. In the first embodiment, the internal configuration of each detection unit, the number and arrangement of the detection units, and the like are not limited to the configuration example of FIG. 6, and various modifications can be made.

As shown in FIG. 7A, the adjustment system of the first embodiment applied to the light source unit 2 of the LPP light source type is a focusing position for changing the focusing position P2 of the laser light from the laser light source 26. As a means of change, a parallel flat plate 67 arranged in the optical path of the laser irradiation system (26, 27) and capable of tilting with respect to the optical axis, and tilting drive of the parallel flat plate 67 in response to a command from the control unit 65 and It has a drive unit 66a for driving along the optical axis of the lens 27. In FIG. 7A, the parallel flat plate 67 is arranged between the laser light source 26 and the lens 27, but the parallel flat plate 67 can also be arranged between the lens 27 and the condensing position P2.

Further, as shown in FIG. 7B, the adjustment system of the first embodiment applied to the light source unit 2 is for adjusting the position and orientation of the gas jet nozzle 23 in response to a command from the control unit 65. It has a nozzle adjusting unit 66b. The nozzle adjusting unit 66b adjusts the position and orientation of the gas jet nozzle 23 by driving, for example, the nozzle stage 23b holding the gas jet nozzle 23 via an appropriate actuator (such as a piezo element), and eventually gas. The path of the target gas 23a injected from the jet nozzle 23 is changed. Instead of the gaseous target material, the liquid target material may be continuously jetted or supplied as droplets.

FIG. 8 is a diagram schematically showing how the angular distribution of the light intensity of the EUV light incident on the concave reflector changes when the focusing position of the laser light changes relative to the droplet-like or liquid columnar target. Is. In FIG. 8, when the laser beam L1 (indicated by the solid line in the figure) from the laser irradiation system (26, 27) is focused on the approximately center position of the target 23a supplied along the direction perpendicular to the paper surface, it is a concave surface. The angular distribution of the light intensity of the EUV light incident on the reflector 24 is substantially axially symmetric with respect to the laser light axis as shown by the solid line D1 in the figure.

However, when the laser beam L2 (indicated by the broken line in the figure) from the laser irradiation system (26, 27) is focused at a position substantially off the center of the target 23a, the EUV light incident on the concave reflector 24 The angular distribution of the light intensity of is substantially axially asymmetric with respect to the laser optical axis as shown by the broken line D2 in the figure. In other words, the axial symmetry of the light intensity angle distribution of the EUV light incident on the concave reflector 24 can be adjusted by changing the focusing position P2 of the laser light relative to the target 23a.

Therefore, in the adjustment system of the first embodiment applied to the light source unit 2, the parallel flat plate 67 is tilted and driven via the drive unit 66a that receives a command from the control unit 65, and if necessary. By driving the lens 27 in the optical axis direction, the focused position P2 of the laser light from the laser light source 26 is changed. Further, the position and orientation of the nozzle 23 are adjusted via the nozzle adjusting unit 66b that receives a command from the control unit 65, and the path of the target 23a ejected from the nozzle 23 is changed. In this way, the angular distribution of the light intensity of the EUV light incident on the concave reflector 24 can be adjusted substantially axisymmetrically by the change of the focused position P2 of the laser light and the change of the path of the target 23a. If the nozzle adjusting unit 66b controls the target position to be constant, the angle distribution can be adjusted without changing the light emitting position.

On the other hand, as shown in FIG. 7 (c), the adjustment system of the first embodiment applied to the light source unit 1 of the DPP light source type receives a command from the control unit 65 and receives a command from the control unit 65 to discharge a pair of electrodes (11a, 11b). ) Is provided as an electrode driving means for rotating the) around the discharge shaft, for example, an electrode driving unit 66c such as a motor. In this case, due to the action of the electrode drive unit 66c that receives the command from the control unit 65, the pair of electrodes (11a, 11b) rotate around the discharge axis, and eventually the light intensity distribution of the EUV light incident on the concave reflector 12. Also rotates around the axis. As a result, the angular distribution of the light intensity of the EUV light incident on the concave reflector 12 can be adjusted substantially axisymmetrically by the so-called averaging effect.

[Second Example]

FIG. 9 is a diagram schematically showing the configuration of a detection system that detects the axial symmetry of the angular distribution of the light intensity of EUV light that is once collected and emitted by the concave reflector in the second embodiment. FIG. 10 is a diagram schematically showing the configuration of an adjustment system that adjusts the position and orientation of the concave reflector so that the angular distribution of light intensity is substantially axisymmetric based on the detection result of the detection system of FIG. .. Referring to FIG. 9A, the detection system according to the second embodiment is arranged around the effective luminous flux L3 of EUV light that is once condensed and emitted at a predetermined position P1 by a concave reflector (12; 24). It is provided with four detection units 71 to 74 (73 and 74 are not shown in FIG. 9A) and a control unit 75 to which outputs from the respective detection units 71 to 74 are supplied.

The four detection units 71 to 74 have the same basic configuration as the detection units 61 to 64 of the first embodiment, and are substantially rotated with respect to the central axis of the effective luminous flux L3 of EUV light, for example, through the predetermined position P1. It is arranged in a symmetrical position. As an example, as shown in FIG. 9B, the first detection unit 71 is located around a photodetector 71a, such as a photodiode, and a light source body (11; 23,26,27) around an effective luminous flux L3. It has a selection filter 71b that transmits only EUV light of a predetermined wavelength (13.5 nm) out of the reaching light and guides it to the photodiode 71a.

Alternatively, in another aspect, the second detection unit 71 is the light reaching around the effective luminous flux L3 from the photodiode 71a and the light source body (11; 23,26,27), as shown in FIG. 9 (c). It has a multilayer mirror 71c that reflects only EUV light of a predetermined wavelength (13.5 nm) and guides it to the photodiode 71a. Here, the multilayer mirror 71c has the same characteristics as the multilayer mirror 61b of the first embodiment, and the selection filter 71b has the same characteristics as the selection filter 61c of the first embodiment. A multilayer mirror and a selection filter may be used in combination.

In the second embodiment, the outputs from the detection units 71 to 74 are supplied to the control unit 75, respectively. The control unit 75 has an angular distribution (in-plane distribution) of the light intensity of EUV light that is once condensed and emitted at a predetermined position P1 by a concave reflector (12; 24) based on the output from each detection unit 71 to 74. ) Detects the axial symmetry. In the second embodiment as well, the internal configuration of each detection unit, the number and arrangement of the detection units, and the like are not limited to the configuration example shown in FIG.

As shown in FIG. 10, the adjustment system of the second embodiment has a reflector adjustment unit 76 that adjusts the position and orientation of the concave reflector (12; 24) in response to a command from the control unit 75. The reflector adjusting unit 76 changes its position and orientation by driving the concave reflector (12; 24) via an appropriate actuator (such as a piezo element). In this way, the position and orientation of the concave reflector (12; 24) are changed by the action of the reflector adjustment unit 76 that receives the command from the control unit 75, and the EUV light that is once condensed and emitted at the predetermined position P1 is emitted. The angular distribution of can be adjusted almost axisymmetrically.

When the adjustment system of the second embodiment is applied to the light source unit 2 of the LPP light source type, the condensing position changing means (27, 66a, 67) shown in FIG. 7 (a) and the condensing position changing means (27,66a, 67) shown in FIG. It is preferable to have the nozzle adjusting means (66b) shown in FIG. 7 (b). In this case, the light is once focused at the predetermined position P1 by the cooperative action of the reflector adjusting means (76) shown in FIG. 10 with the focusing position changing means (27, 66a, 67) and the nozzle adjusting means (66b). The angular distribution of the emitted EUV light can be adjusted more accurately and quickly.

Further, when the adjustment system of the second embodiment is applied to the light source unit 1 of the DPP light source type, it is preferable to have an electrode driving means (66c) as needed. In this case, the angular distribution of the EUV light that is once condensed and emitted at the predetermined position P1 by the cooperative action of the reflector adjusting means (76) and the electrode driving means (66c) shown in FIG. 10 is more accurate and quick. Can be adjusted to.

[Third Example]

FIG. 11 is a diagram schematically showing a configuration of a detection system that detects the condensed position of EUV light reflected by the concave reflector in the third embodiment and a configuration of an adjustment system that adjusts the condensed position of EUV light. Is. When the detection system according to the third embodiment is applied to the light source unit 2 of the LPP light source type, as shown in FIG. 11A, a predetermined position where the EUV light reflected by the concave reflector 24 should be focused. It includes a two-dimensional photodetector 81 attached to the surface of the pinhole member 29 arranged on P1 on the light incident side, and a control unit 82 to which the output from the two-dimensional photodetector 81 is supplied.

The two-dimensional photodetector 81 is formed by, for example, arranging photodiodes 81a to 81d in each fan-shaped divided region obtained by dividing the surface of the pinhole member 29 on the light incident side into four parts. In this case, if the focusing position of the EUV light reflected by the concave reflector 24 is displaced from the pinhole 29a of the pinhole member 29, the output signal of at least one of the four photodiodes 81a to 81d will be output. Change.

In the third embodiment, the outputs from the four photodiodes 81a to 81d as the two-dimensional photodetector 81 are supplied to the control unit 82, respectively. The control unit 82 detects the condensed position and intensity distribution of the EUV light reflected by the concave reflector 24 based on the outputs from the photodiodes 81a to 81d. Similarly, when applied to the DPP light source type light source unit 1, four photodiodes 81a to 81d may be arranged at a predetermined position P1 where the EUV light reflected by the concave reflector 12 should be focused.

In the third embodiment, by further increasing the number of divisions of the pinhole member on the light incident surface, the EUV light focusing position and intensity distribution can be detected with higher accuracy. Further, without being limited to the configuration using a plurality of photodiodes, a plurality of divided metal plates are simply arranged in the vicinity of the condensing position, and the photoelectrons emitted from each metal plate or the flowing photoelectron flow are measured. You may. It is also possible to use a two-dimensional image sensor arranged on the light incident surface of the pinhole member, and the detection system that detects the focused position of the EUV light reflected by the concave reflector (12; 24) is shown in the figure. Various modifications are possible without being limited to the 11 configuration examples.

The adjustment system of the third embodiment has a reflector adjustment unit 76 (see FIG. 10) that adjusts the position and orientation of the concave reflector (12; 24) in response to a command from the control unit 82. The reflector adjusting unit 76 changes its position and orientation by driving the concave reflector (12; 24) via an appropriate actuator (such as a piezo element). In this way, the position and orientation of the concave reflector (12; 24) are changed by the action of the reflector adjustment unit 76 that receives the command from the control unit 82, and the EUV reflected by the concave reflector (12; 24). It can be adjusted so that the light condensing position is approximately the predetermined position P1.

Further, when the adjustment system of the third embodiment is applied to the light source unit 2 of the LPP light source type, FIG. 7A shows FIG. 7A as a means for changing the emission position of EUV light from the plasma P. It has the light source position changing means (27, 66a, 67) shown and the nozzle adjusting means (66b) shown in FIG. 7 (b). In this way, the EUV light emission position from the plasma P is changed by the action of the condensing position changing means (27,66a, 67) and the nozzle adjusting means (66b) in response to the command from the control unit 82, and the concave reflection The position where the EUV light reflected by the mirror 24 is collected can be adjusted to be approximately the predetermined position P1.

Further, when the adjustment system of the third embodiment is applied to the light source unit 1 of the DPP light source type, as shown in FIG. 11B, a pair of electrodes (11a, 11b) receives a command from the control unit 82. ) Is provided with an electrode position changing means 83 for changing the position. The electrode position changing means 83 changes its position by integrally driving a pair of electrodes (11a, 11b) via an appropriate actuator (piezo element or the like). In this way, the position of the pair of electrodes (11a, 11b) is changed by the action of the electrode position changing means 83 receiving the command from the control unit 82, and the emission position of the EUV light from the plasma P is changed, so that the concave surface is formed. The focusing position of the EUV light reflected by the reflector 12 can be adjusted to be approximately the predetermined position P1.

[Fourth Example]

FIG. 12 is a diagram schematically showing the configuration of a detection system for detecting the emission position of EUV light from plasma in the fourth embodiment. Referring to FIG. 12, the detection system according to the fourth embodiment is composed of two detection units 91 and 92 arranged around the effective luminous flux of EUV light incident on the concave reflector (12; 24) from the plasma P. It includes a control unit 93 to which outputs from the detection units 91 and 92 are supplied. The two detection units 91 and 92 have the same basic configuration as each other.

That is, each detection unit 91 (92) is a pinhole member arranged in an optical path between a two-dimensional image sensor 91a (92a) such as a two-dimensional CCD and the plasma P and the two-dimensional CCD 91a (92a). It has 91b (92b). In the fourth embodiment, the outputs from the detection units 91 and 92 are supplied to the control unit 93, respectively. The control unit 93 detects the emission position of the EUV light from the plasma P based on the outputs from the detection units 91 and 92. In the fourth embodiment as well, the internal configuration of each detection unit, the number and arrangement of the detection units, and the like are not limited to the configuration example shown in FIG. 12, and various modifications can be made.

When the adjustment system of the fourth embodiment is applied to the light source unit 1 of the DPP light source type, as shown in FIG. 11 (b), the adjustment system of the pair of electrodes (11a, 11b) receives a command from the control unit 93. It has an electrode position changing means 83 for adjusting the position. In this way, the position (for example, the X, Y, Z directions) of the pair of electrodes (11a, 11b) is changed by the action of the electrode position changing means 83 that receives the command from the control unit 93, and eventually the EUV light from the plasma P. It can be adjusted so that the light emitting position of is almost a predetermined position.

When the adjustment system of the fourth embodiment is applied to the light source unit 2 of the LPP light source type, the focusing position changing means (27, 66a, 67) shown in FIG. 7 (a) and the nozzle shown in FIG. 7 (b). It has an adjusting means (66b). In this way, the EUV light emission position from the plasma P is set to almost the predetermined position by the action of the focusing position changing means (27, 66a, 67) and the nozzle adjusting means (66b) receiving the command from the control unit 93. Can be adjusted to.

[Fifth Example]

FIG. 13 shows the configuration of the detection system that detects the axial symmetry of the angular distribution of the light intensity of the EUV light incident on the optical integrator in the fifth embodiment, and the adjustment system that adjusts the angular distribution of the light intensity substantially axially symmetric. It is a figure which shows the structure schematicly. Referring to FIG. 13 (a), the detection system according to the fifth embodiment includes an ammeter 101 connected to a plurality of element mirrors among a large number of element mirrors 32aa constituting the first fly-eye mirror 32a, and an ammeter 101 thereof. It includes a control unit 102 to which the output of the ammeter 101 is supplied.

When EUV light is incident on the element mirror 32aa, a number of photoelectrons corresponding to the intensity of the incident light are emitted from the metal surface. The ammeter 101 detects the current generated by the emission of photoelectrons from each element mirror, that is, the photoelectron current. In the fifth embodiment, the output of the ammeter 101 is supplied to the control unit 102. The control unit 102 determines the EUV light incident on the first flyeye mirror 32a and thus the EUV incident on the optical integrator 32 based on the output from the ammeter 101, that is, based on the information on the amount of photoelectron current generated by each element mirror. Detects the axial symmetry of the angular distribution of light intensity. It should be noted that the same number of ammeters 101 as the number of element mirrors to be detected may be used, or the photoelectron currents from each element mirror may be sequentially detected by one or a small number of ammeters 101 in a time division manner.

As shown in FIG. 13B, the adjustment system of the fifth embodiment has a mirror adjustment unit 103 that adjusts the position and orientation of the collimator mirror 31 in response to a command from the control unit 102. The mirror adjusting unit 103 changes its position and orientation by driving the collimator mirror 31 via an appropriate actuator (piezo element or the like). In this way, the position and orientation of the collimator mirror 31 are changed by the action of the mirror adjusting unit 103 that receives the command from the control unit 102, and the angular distribution (in-plane distribution) of the light intensity of the EUV light incident on the optical integrator 32. Can be adjusted almost axisymmetrically. Alternatively, when the illuminance distribution on the mask becomes uneven due to contamination of the optical element or the like, the axial symmetry of the angular distribution (in-plane distribution) is intentionally deteriorated by changing the position or orientation of the collimator mirror 31. It may be controlled so that the illuminance distribution on the mask becomes uniform.

Further, the adjustment system of the fifth embodiment has a reflector adjustment unit 76 (see FIG. 10) that adjusts the position and orientation of the concave reflector (12; 24) in response to a command from the control unit 102. In this case, the position and orientation of the concave reflector (12; 24) are changed by the action of the reflector adjusting unit 76 in response to the command from the control unit 102, and the light intensity of the EUV light incident on the optical integrator 32 is changed. The angular distribution can be adjusted almost axisymmetrically.

As described above, in the present embodiment, the concave surface is caused by various causes such as deformation or wear of the electrode or nozzle, replacement mounting error of the worn electrode or nozzle or concave reflector, and change in the focusing position of the laser light with respect to the target gas. Angle distribution of the light intensity of the EUV light incident on the reflector (12; 24) and the EUV light supplied from the light source unit (1; 2) while being once condensed and diverged by the concave reflector (12; 24). Even if the (in-plane distribution) is substantially axially asymmetric, the angular distribution of light intensity can be made substantially axially symmetric by applying the configuration of the first or second embodiment described above. Can be adjusted. That is, the light source unit of the present embodiment can stably supply EUV light having a desired light intensity angle distribution (in-plane distribution).

Further, in the present embodiment, the focusing position of the EUV light reflected by the concave reflector (12; 24) and the emission position of the EUV light from the plasma P may change due to various causes as described above. However, by applying the configuration of the third embodiment or the fourth embodiment described above, the condensing position and the light emitting position can be adjusted to be predetermined positions. That is, in the light source unit of the present embodiment, the light emitting position (plasma generation position) and the condensing position can be stably maintained at substantially predetermined positions.

Further, in the present embodiment, even if the angular distribution (in-plane distribution) of the light intensity of the EUV light incident on the optical integrator 32 may be substantially axisymmetric due to various causes as described above, the above-mentioned By applying the configuration of the fifth embodiment of the above, the angular distribution of the light intensity can be adjusted to be substantially axisymmetric. That is, in the illumination optical device of the present embodiment, the illuminated surface (mask M) can be stably illuminated with EUV light having a desired light intensity angle distribution (in-plane distribution).

Therefore, in the exposure apparatus of the present embodiment, the light source unit that stably supplies EUV light having a desired light intensity angle distribution (in-plane distribution), and the light emitting position and the condensing position are stably maintained at substantially predetermined positions. Using a light source unit or an illumination optical device that stably illuminates the illuminated surface with EUV light having a desired light intensity angle distribution (in-plane distribution), the desired illumination conditions (for example, uniform irradiation light amount distribution) can also be obtained. The mask pattern can be faithfully transferred onto the photosensitive substrate. In this embodiment, the configurations of the first to fifth embodiments may be applied individually, or the configurations of a plurality of examples may be appropriately combined and applied.

By the way, in the present embodiment, the reflecting surface (12a; 24a) of the concave reflector (12; 24) is directly exposed to the plasma P, and is affected by the radiant heat from the plasma P and the irradiation heat of the EUV light. It will be necessary to replace the concave reflector (12; 24). Therefore, in order to easily and accurately replace the concave reflector (12; 24), a measurement system for measuring the position (and attitude) of the reflective surface (12a; 24a) of the concave reflector (12; 24). And, it is preferable to provide a drive system for positioning the reflecting surface (12a; 24a) of the concave reflecting mirror (12; 24) at a predetermined position based on the measurement result of this measuring system.

FIG. 14 is a diagram schematically showing a configuration of a measurement system for measuring the position of the reflective surface of the concave reflector and a configuration of a drive system for positioning the reflective surface of the concave reflector at a predetermined position. The measurement system shown in FIG. 14 includes, for example, three measurement units 51 to 53 (53 is not shown) and a control unit 54 to which outputs from the respective measurement units 51 to 53 are supplied. The three measuring units 51 to 53 have the same basic configuration as each other. That is, each measurement unit 51 (52,53) has a semiconductor laser 51a (52a, 53a) for emitting measurement light toward the reflection surface (12a; 24a) of the concave reflector (12; 24) and a concave surface. It has a two-dimensional CCD 51b (52b, 53b) for detecting the position of the measurement light reflected by the reflecting surface (12a; 24a) of the reflecting mirror (12; 24).

The control unit 54 measures the position (and attitude) of the reflecting surface (12a; 24a) of the concave reflecting mirror (12; 24) based on the outputs from the measuring units 51 to 53. In this way, the drive system 55 (corresponding to the reflector adjustment unit 76 in FIG. 10) that receives the command from the control unit 54 drives the concave reflector (12; 24) via an appropriate actuator (piezo element, etc.). As a result, the reflecting surface (12a; 24a) of the concave reflecting mirror (12; 24) is positioned at a predetermined position. In FIG. 14, a laser diode (semiconductor laser) is used, but the present invention is not limited to this, and a light emitting diode (LED) and a lens or the like may be used instead of the CCD. A diode may be used. Further, the configuration of the measurement system for measuring the position of the reflecting surface (12a; 24a) of the concave reflector (12; 24) is not limited to the configuration example shown in FIG. Is.

Further, in the present embodiment, when scattered particles (debris) emitted when the EUV light from the plasma P is radiated adheres to the reflecting surface (12a; 24a) of the concave reflecting mirror (12; 24), the concave reflecting mirror (12) The reflection characteristics (optical characteristics) of 24) deteriorate, and the frequency of replacement increases. Therefore, in the present embodiment, it is preferable to provide a scattering particle removing mechanism for removing scattered particles emitted from the plasma P in the optical path between the plasma P and the concave reflector (12; 24).

FIG. 15 is a diagram schematically showing an example of a scattered particle removing mechanism applicable to the DPP light source type light source unit shown in FIG. The scattered particle removing mechanism of FIG. 15 includes a cover 18 that covers the concave reflector 12. A rotating blade 19 (scattered particle blocking member) that can rotate around the rotating shaft 19a is housed in the cover 18. The rotation shaft 19a is rotationally driven via the rotation introduction portion 19b by the action of a drive system (not shown) outside the chamber 13.

A refrigerant (for example, cooling water, fluoro, helium (He) gas, etc.) is configured to flow in the rotating shaft 19a, and the rotating blade 19 is cooled by the action of this refrigerant. Piping 18a is attached to the cover 18, and buffer gas (He, Ar, N)₂, Ne, Kr, H₂Etc.) are introduced into the cover 18 from the periphery of the concave reflector 12 via the pipe 18a.

In the scattered particle removing mechanism of FIG. 15, the scattered particles emitted from the plasma P near the pair of electrodes (11a, 11b) collide with the buffer gas molecules introduced into the chamber 13 and their kinetic energy is reduced. Float in chamber 13. Then, the scattered particles that have entered the cover 18 collide with the rotating blade 19 and adhere to the rotating blade 19. As a result, the scattered particles that have entered the cover 18 are eliminated by the rotating blades 19 and do not substantially reach the concave reflecting mirror 12, and the reflectance of the concave reflecting mirror 12 can be prevented from being lowered due to the adhesion of the scattered particles or the like. ..

In particular, since the cooling of the rotating blade 19 makes it easier for the scattered particles to adhere and accumulate, the scattered particles can be eliminated more effectively. Further, by introducing the buffer gas into the cover 18 from the vicinity of the concave reflector 12 and allowing the buffer gas to flow out from the opening of the cover 18, the action of this gas flow also causes the buffer gas to flow into the cover 18. It is more preferable because the scattered particles that have entered can be eliminated. Further, it is preferable that the rotary blade 19 is replaceable. It is preferable that the rotation speed of the rotary blade 19 is as fast as possible in order to reduce unevenness in the amount of light on the mask. For example, the number of revolutions per minute may be 10 or more. Further, if the ratio of the repetition frequencies of EUV light emission is not made an integral multiple, the positions where the blades block the luminous flux will not be the same. Alternatively, the blades may be rotated while changing the rotation speed, and it is more preferable to make the rotation speed random. In the above description, the scattered particle removal mechanism is arranged between the plasma P and the concave reflector 12, but between the pair of reflectors constituting the condensing optical system (for example, between the concave reflector and the convex reflector). In order to remove scattered particles in the optical path (between such a plurality of reflectors), a scattered particle removing mechanism as shown in FIG. 15 can also be arranged.

FIG. 16 is a diagram schematically showing an example of a scattered particle removing mechanism applicable to the LPP light source type light source unit shown in FIG. The scattered particle removing mechanism of FIG. 16 includes a cover 40 that covers the concave reflector 24. Piping 41 is attached to the cover 40, and the buffer gas (He, Ar, Kr, N)₂, Ne, H₂Etc.) are introduced into the cover 40 via the pipe 41. In the cover 40, fins 42 are provided in the optical path between the plasma P and the concave reflector 24. An opening 42a is formed in the center of the fin 42, and the laser light emitted from the laser light source 26 and passing through the concave reflector 24 reaches the position of the plasma P through the opening 42a.

In the scattered particle removing mechanism of FIG. 16, the scattered particles emitted from the plasma P collide with the buffer gas molecules introduced into the chamber 21 to reduce their kinetic energy and float in the chamber 21. Then, the scattered particles that have entered the cover 40 collide with the fin 42 (scattered particle blocking member) and adhere to the fin 42. As a result, the scattered particles that have entered the cover 40 are eliminated by the fins 42 and do not substantially reach the concave reflector 24, so that the reflectance of the concave reflector 24 can be prevented from decreasing.

By introducing buffer gas from the vicinity of the concave reflector 24 and configuring the gas to flow out from the opening of the cover 40, scattered particles that have entered the cover 40 are eliminated by the action of this gas flow. It is more preferable because it can be used. By making the cross-sectional shape of the fin 40 as shown in FIG. 16, light loss can be minimized. By cooling the fin 40, scattered particles are likely to adhere and accumulate, so that scattered particles can be eliminated more effectively. It is also preferable to rotate the fin 40 around the laser optical axis (the optical axis of EUV light) because the ability to remove scattered particles increases. Further, it is preferable that the fin 40 is replaceable.

In the above-described embodiment, the present invention is applied to the DPP light source type light source unit 1 having the basic configuration as shown in FIG. 3 and the LPP light source type light source unit 2 having the basic configuration as shown in FIG. Applying. However, the present invention is not limited to this, and the present invention can be applied to a general DPP light source type light source unit and an LPP light source type light source unit. Specifically, unlike the configuration shown in FIG. 3, for example, a configuration in which EUV light radiated from a plasma generated by a discharge between a pair of electrodes is focused using an obliquely incident mirror or a Schwarzschild optical system is used. The present invention can also be applied to a light source unit of the LPP light source type. Further, unlike the configuration shown in FIG. 4, the present invention can be applied to, for example, an LPP light source type light source unit having a configuration in which a laser beam is focused on a target without passing through a concave reflector.

In the exposure apparatus according to the above-described embodiment, the mask is illuminated by the illumination system (illumination step), and the transfer pattern formed on the mask is exposed on the photosensitive substrate by using the projection optical system (exposure step). , Microdevices (semiconductor elements, image pickup elements, liquid crystal display elements, thin film magnetic heads, etc.) can be manufactured. Hereinafter, the flowchart of FIG. 17 will be referred to as an example of a method for obtaining a semiconductor device as a microdevice by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of the present embodiment. I will explain.

First, in step 301 of FIG. 17, a metal film is vapor-deposited on one lot of wafers. In the next step 302, the photoresist is applied onto the metal film on the one lot of wafer. Then, in step 303, using the exposure apparatus of the present embodiment, the image of the pattern on the mask (reticle) is sequentially exposed and transferred to each shot region on the wafer of one lot via the projection optical system. ..

Then, in step 304, the photoresist on the one lot of wafers is developed, and then in step 305, etching is performed on the one lot of wafers using the resist pattern as a mask to obtain a pattern on the mask. Corresponding circuit patterns are formed in each shot region on each wafer. After that, a device such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer or the like. According to the above-mentioned semiconductor device manufacturing method, a semiconductor device having an extremely fine circuit pattern can be obtained with good throughput.

<figref num="1">It is a figure which shows schematic the whole structure of the exposure apparatus provided with the light source unit which concerns on embodiment of this invention.</figref><figref num="2">It is a figure which shows the positional relationship between the static exposure area formed on a wafer, and an optical axis.</figref><figref num="3">It is a figure which shows schematic the internal structure of the light source unit of a DPP light source type.</figref><figref num="4">It is a figure which shows schematic the internal structure of the light source unit of the LPP light source type.</figref><figref num="5">It is a figure which shows schematic the internal structure of an illumination optical system and a projection optical system.</figref><figref num="6">It is a figure which shows roughly the structure of the detection system which detects the axial symmetry of the angular distribution of the light intensity of EUV light incident on a concave reflector in 1st Example.</figref><figref num="7">It is a figure which shows the structure of the adjustment system which adjusts the light source body so that the angular distribution of light intensity becomes substantially axisymmetric based on the detection result of the detection system of FIG.</figref><figref num="8">It is a figure which shows typically how the angular distribution of the light intensity of EUV light incident on a concave reflector changes when the condensing position of a laser beam changes relative to a droplet-like or liquid columnar target.</figref><figref num="9">It is a figure which shows roughly the structure of the detection system which detects the axial symmetry of the angular distribution of the light intensity of EUV light which is once condensed and emitted by the concave reflector in the 2nd Example.</figref><figref num="10">FIG. 5 is a diagram schematically showing a configuration of an adjustment system that adjusts the position and orientation of a concave reflector so that the angular distribution of light intensity is substantially axisymmetric based on the detection result of the detection system of FIG.</figref><figref num="11">It is a figure which shows roughly the structure of the detection system which detects the condensing position of EUV light reflected by the concave reflector in the 3rd Example, and the structure of the adjustment system which adjusts the condensing position of EUV light.</figref><figref num="12">It is a figure which shows roughly the structure of the detection system which detects the emission position of EUV light from plasma in 4th Example.</figref><figref num="13">In the fifth embodiment, a configuration of a detection system for detecting the axial symmetry of the angular distribution of the light intensity of the EUV light incident on the optical integrator, and a configuration of an adjustment system for adjusting the angular distribution of the light intensity so as to be substantially axisymmetric. It is a figure which shows schematicly.</figref><figref num="14">It is a figure which shows typically the structure of the measurement system which measures the position of the reflection surface of a concave reflector, and the structure of the drive system which positions the reflection surface of a concave reflector at a predetermined position.</figref><figref num="15">It is a figure which shows typically an example of the scattered particle removal mechanism applicable to the light source unit of the DPP light source type shown in FIG.</figref><figref num="16">It is a figure which shows typically an example of the scattered particle removal mechanism applicable to the light source unit of the LPP light source type shown in FIG.</figref><figref num="17">It is a figure which shows the flowchart of an example of the method for obtaining a semiconductor device as a microdevice.</figref>

Code description

1 DPP light source type light source unit 2 LPP light source type light source unit 3 Illumination optics 5 Mask stage 7 Wafer stage 11 Light source body 11a, 11b Electrodes 12, 24 Concave reflector 13 Chamber 15 Opening 16, 28 Selective filter 21 Vacuum container 23 Gas Jet Nozzle 26 Laser Light Source 29 Pinhole Member 31 Collimeter Mirror 32 Optical Integrator 32a, 32b Fly Eye Mirror M Mask PL Projection Optics W Wafer