Aligner

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an exposure apparatus, and more particularly to a projection exposure apparatus using a reflection / refraction type optical system as a projection optical system using an ultraviolet source as a light source.

【0002】

[Conventional technology]

An exposure device that exposes a pattern on a mask onto a wafer is desired to have a higher resolution, and for this purpose, an exposure device using a short wavelength light source, for example, a KrF excimer laser having a wavelength of 248 nm is developed. It has become. And ArF excimer laser with wavelength 193nm and F with wavelength 157nm₂Lasers are further shortening the wavelength.

【0003】

As the projection optical system, a refraction optical system or a reflection refraction type optical system is generally used. However, since the types of glass that can be used with a short wavelength light source are limited, it tends to be difficult to correct chromatic aberration. On the other hand, the catadioptric system is effective in removing chromatic aberration, which is a great advantage. There are several types of reflection-refractive optical systems. A type using a cube-type beam splitter is disclosed, for example, in JP-A-6-300973. Further, a type that forms an intermediate image is disclosed in, for example, Japanese Patent Application Laid-Open No. 10-10431.

【0004】

As shown in FIG. 6, the reflection / refraction reduction optical system disclosed in Japanese Patent Application Laid-Open No. 6-300973 is a reflection / refraction reduction optical system used for manufacturing photography of a semiconductor having a high number of openings, and has a reticle surface 100. The light rays from are sequentially passed through the first lens group, the deflector 20, the second lens group, the beam splitter cube 30, and the quarter wavelength plate 32, and are reflected by the concave mirror 34. Then, the reflected light passes through the beam splitter cube 30 again, passes through the third lens group, and is converged on the wafer surface 50. In order to further reduce higher-order aberrations, the concave mirror 34 is aspherical.

【0005】

Further, as shown in FIG. 7, the "catadioptric system" disclosed in Japanese Patent Application Laid-Open No. 10-10431 has a sufficiently large numerical aperture and working distance on the image side, and has a quarter-micron unit resolution in the ultraviolet region. It is a small catadioptric system having a catadioptric system, and after the light from the object surface is reflected by the concave reflector CM of the first imaging optical system S1, an intermediate image is formed in the optical path of the first imaging optical system S1. Form. This intermediate image is imaged on the wafer surface by the second imaging optical system S2 via the first optical path changing member M1. By setting the imaging magnification of the first imaging optical system S1 between 0.75 and 0.95, the optical path deflection by the first optical path deflecting member M1 is possible, and the numerical aperture NA on the image side of the optical system is increased. There is. Furthermore, the value of L1 / LM is set between 0.13 and 00.35 (the axial distance between the intersection of the optical axis of the first imaging optical system S1 and the optical axis of the second imaging optical system S2 and the object surface L1: By setting the axial distance between the object surface and the concave mirror CM (LM)), the working distance on the image side of the optical system is secured, and coma and distortion are satisfactorily corrected.

【0006】

Further, FIG. 8 shows a known reflection / refraction type projection optical system (Example 1 of Japanese Patent Application Laid-Open No. 10-20195), in which the lens in the vicinity of the concave mirror in the reciprocating optical path is oriented in the optical axis direction. I'm moving to.

【0007】

[Problems to be Solved by the Invention]

However, ArF excimer laser and F₂In the case of a laser, the absorption of light by the glass becomes larger than before, and therefore the amount of thermal aberration generated during exposure becomes larger than before.

【0008】

Aberrations also change due to changes in atmospheric pressure and lighting conditions.

【0009】

In order to correct these, the lens near the object surface may be moved, but if the moving distance is increased because it is necessary to increase the change in aberration with respect to the lens movement, the mechanical position of the lens to be moved is increased. The accuracy is poor and therefore the aberration of interest cannot be reduced.

【0010】

When NA (number of openings) is small, the residual amount of symmetric aberration such as spherical aberration, astigmatism, and curvature of field after correcting the magnification and distortion is small, but for example, spherical aberration and non-spherical aberration. Since the residual amount of symmetric aberration such as point aberration and curvature of field increases in proportion to the 4th and 2nd power of NA in the wave surface aberration display, it is a non-negligible amount in the case of high NA. In the future, NA will increase as semiconductor devices become finer, so reducing the symmetry aberration that increases with the power of NA is one of the most important issues.

【0011】

Therefore, an object of the present invention is to provide an optical system and an exposure apparatus capable of reducing symmetry aberration.

【0012】

[Means for solving problems]

The invention of claim 1 is characterized in that the symmetry aberration of the optical system is adjusted by moving an optical element that contributes to the aberration in the reciprocating optical path portion of the reflection / refraction type projection optical system.

【0013】

The invention of claim 2 corrects at least one of spherical aberration, astigmatism, and curvature of field aberration by moving the lens of the reciprocating optical path portion of the reflection-refraction type projection optical system in the optical axis direction. It is characterized by that.

【0014】

The invention of claim 3 is characterized in that at least one of spherical aberration, astigmatism, and curvature of field aberration generated by thermal, atmospheric pressure, or illumination conditions is corrected.

【0015】

The invention of claim 4 is characterized in that a light ray incident on the lens is reflected by an aperture diaphragm or a mirror at a position equivalent to the aperture diaphragm, and is again incident on the lens.

【0016】

The invention of claim 5 is characterized in that the mirror is a concave mirror.

【0017】

The invention of claim 6 is characterized in that the mirror is a convex mirror.

【0018】

The invention of claim 7 is characterized in that an ArF laser is used as a light source.

【0019】

The invention of claim 8 uses F as a light source.₂It is characterized by using a laser.

【0020】

The invention of claim 9 is characterized in that coma and distortion, which are asymmetric aberrations of the optical system, are corrected by moving an optical element that contributes to lens aberrations provided in a one-way optical path portion.

【0021】

The invention of claim 10 is a device manufacturing method using the above-mentioned exposure apparatus, which is characterized in that a wafer is exposed with a device pattern and the exposed wafer is developed.

【0022】

BEST MODE FOR CARRYING OUT THE INVENTION

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

【0023】

[Embodiment 1] FIG. 1 is an optical path diagram of a reflection / refraction type reduction projection optical system having an image plane side NA of 0.65 or more and provided with a beam splitter, which is used in the exposure apparatus of the present invention. 1 is a mask, 2 is a wafer, LG1 to LG3 are 1st to 3rd lens groups, MR1 is a concave mirror, and BS is a cube-type beam splitter. The exposure apparatus of the present invention is used in a process of manufacturing various devices such as semiconductor chips such as LSIs, liquid crystal panels, CCDs, and magnetic heads, and the wafers are exposed by this apparatus to develop the exposed wafers. Become.

【0024】

The first lens group LG1 and the third lens group LG3 are lens groups through which light rays pass only once, and the second lens group LG2 is a lens group through which light rays pass twice (because they reciprocate).

【0025】

In addition, 3 is a lens that can move in the optical axis direction in the second lens group LG2, 4 is a drive device for moving the lens 3 in the optical axis direction, and 5 controls the device 4 to move the lens 3. A control device for control, 6 is an aberration measuring device.

【0026】

The light beam emitted from the mask 1 passes through the first lens group LG1, passes through the beam splitter BS, passes through the second lens group LG2, and then reaches the concave mirror MR1 and is reflected.

【0027】

The light rays reflected by the concave mirror MR1 pass through the second lens group LG2 again, then enter the beam splitter BS, are reflected and emit out in a 90-degree direction, pass through the third lens group LG3, and then on the wafer 2. Converges to and forms an image.

【0028】

When the exposure is started, a part of the exposure light is absorbed by the lens material or the mirror material, and the temperature of the lens material or the mirror material rises. Due to this temperature rise, the lens material or the mirror material expands, and the surface shape and the surface spacing are minute but changed. Further, in the lens material, the refractive index distribution changes as the absolute value of the refractive index changes. Although the focus position changes due to these changes, some aberrations also occur, so that the image performance is slightly deteriorated even if the focus is adjusted as it is.

【0029】

In addition, even if the atmospheric pressure changes or the lighting conditions change, aberrations occur and the image performance changes.

【0030】

Therefore, the control device 5 determines the drive amount corresponding to the movement amount of the lens 3 from the exposure amount, the exposure time, and other exposure conditions, and operates the drive device 4. As a result, the lens 3 moves in the optical axis direction by a predetermined amount, and the generated symmetry aberration is corrected. The control device 5 can not only perform such open-loop control, but also perform closed-loop control in which the lens 3 is moved so as to obtain aberration information from a known aberration measuring device 6 and correct the aberration. Is.

【0031】

By moving the lens 3 in this way, the symmetry aberration can be effectively corrected.

【0032】

FIG. 2 is a diagram for explaining the state of occurrence of aberration in the vicinity of the concave mirror MR1 in FIG. For the sake of simplicity, the optical path is expanded and displayed with the concave mirror MR1.

【0033】

The actual light beam passes through the lens 3, is reflected by the concave mirror MR1, and then travels in the opposite direction and passes through the lens 3 again. Proceeding to the right, the mirror MR1 is displayed so as to pass through the lens 3'that is symmetrical to the lens 3. 7 is the marginal ray and 8 is the main ray.

【0034】

Concave-face mirror MR1 is in a position equivalent to the aperture stop position (including an optically conjugate position).

【0035】

Since the lens 3,3'is symmetric with respect to the aperture stop, the asymmetric aberrations such as coma and distortion that occur in the lens 3,3' are summed up with different signs and are canceled by each other. It becomes a small amount.

【0036】

On the other hand, symmetric aberrations such as spherical aberration, astigmatism, and curvature of field are summed up with the same code as those generated by lenses 3, 3', so when only one lens is used (light rays pass only once) Case) will be larger than. When the concave mirror MR1 and the lens 3,3'are in close proximity, it is about twice as large as when only one lens is used.

【0037】

After all, the only aberration that occurs largely in the lens 3,3'is the symmetric aberration, and the asymmetric aberration is small.

【0038】

Therefore, even when the distance between the lens 3, 3'and the concave mirror MR1 is changed (symmetrically), the only aberration that changes significantly is the symmetric aberration, and there is almost no change in the asymmetric aberration.

【0039】

In this way, by moving the lens portion near the concave mirror through which the light beam passes twice, it is possible to significantly change only the symmetry aberration without affecting the asymmetry aberration.

【0040】

Therefore, the symmetry aberration can be effectively corrected by moving an optical element such as a lens 3 that contributes to this aberration in the optical axis direction, for example.

【0041】

[Embodiment 2] FIG. 3 is an optical path diagram of a reflection / refraction type reduced projection optical system having an image plane side NA of 0.65 or more, which is provided with a bending mirror instead of a beam splitter. 1 is a mask, 2 is a wafer, LG1 to LG3 are 1st to 3rd lens groups, MR1 is a concave mirror, and MR2 is a folding mirror.

【0042】

The first lens group LG1 and the third lens group LG3 are lens groups through which light rays pass only once, and the second lens group LG2 is a lens group through which light rays pass twice (because they reciprocate).

【0043】

In addition, 3 is a lens that can move in the optical axis direction in the second lens group LG2, 4 is a drive device for moving the lens 3, and 5 is for controlling the device 4 to control the movement of the lens 3. It is a control device.

【0044】

The light beam emitted from the mask 1 passes through the first lens group LG1, passes through the second lens group LG2, and then reaches the concave mirror MR1 and is reflected.

【0045】

The light rays reflected by the concave mirror MR1 pass through the second lens group LG2 again and then form an intermediate image, but are reflected by the bending mirror MR2 placed near the intermediate image and change the direction by 90 degrees, and the third lens group After passing through LG3, it converges on wafer 2 to form an image.

【0046】

In this case as well, when the exposure is started, a part of the exposure light is absorbed by the lens material or the mirror material, and the temperature of the lens material or the mirror material rises, which causes some aberration due to heat. Even if these are combined, the image performance will be slightly deteriorated.

【0047】

In addition, the image performance changes even if the atmospheric pressure changes or the lighting conditions change.

【0048】

Therefore, the control device 5 determines the drive amount from the exposure amount, the exposure time, the lighting condition, other exposure conditions, the atmospheric pressure, and the like, and operates the drive device 4. As a result, the lens 3, which is an optical element contributing to the symmetry aberration, moves in the optical axis direction by a predetermined amount, and the generated symmetry aberration is corrected. The control device 5 can not only perform such open-loop control, but also perform closed-loop control in which the lens 3 is moved so as to obtain aberration information from an aberration measuring device (not shown) and correct the aberration. Is.

【0049】

For the same reason as in the first embodiment, only the symmetric aberration can be efficiently corrected without being affected by the asymmetric aberration.

【0050】

[Embodiment 3] FIG. 4 is an optical path diagram of another type of 1x reflection / refraction projection optical system without a beam splitter. 1 is a mask, 2 is a wafer, LG1 to LG3 are 1st to 3rd lens groups, MR1 is a concave mirror, and MR3 is a convex mirror.

【0051】

The first lens group LG1 and the third lens group LG3 are lens groups through which light rays pass only once, and the second lens group LG2 is a lens group through which light rays pass twice (because they reciprocate).

【0052】

In addition, 3 is a lens that can move in the optical axis direction in the second lens group LG2, 4 is a drive device for moving the lens 3, and 5 is for controlling the device 4 to control the movement of the lens 3. It is a control device.

【0053】

In this embodiment, the second lens group LG2 is only the lens 3. Further, the lens groups LG1 and LG3 may include a parallel flat plate, and may be composed of only the parallel flat plate.

【0054】

In the figure, the light beam emitted from the mask 1 passes through the first lens group LG1 and is reflected by the concave mirror MR1, passes through the lens 3 constituting the second lens group LG2, and then is reflected by the convex mirror MR3. After passing through the lens 3 again, the light beam is reflected by the concave mirror MR1, passes through the lens group LG3, and converges on the wafer 2 to form an image.

【0055】

In this case as well, the control device 5 determines the drive amount from the exposure conditions such as the exposure amount, the exposure time, and the illumination condition, the atmospheric pressure, and the like, and operates the drive device 4. As a result, the lens 3, which is an optical element that contributes to the aberration, moves in the optical axis direction by a predetermined amount, and the generated symmetric aberration is corrected. The control device 5 can not only perform such open-loop control, but also perform closed-loop control in which the lens 3 is moved so as to obtain aberration information from an aberration measuring device (not shown) and correct the aberration. Is. For the same reason as in the first embodiment, only the symmetry aberration can be efficiently corrected.

【0056】

The case where the present invention is applied to three types of projection optical systems has been described above, but the present invention can be similarly applied to other types of reflection / refraction type optical systems.

【0057】

Further, for the sake of simplicity of explanation, the movement of one lens has been described, but a plurality of lenses in the reciprocating optical path portion may be moved.

【0058】

When it is desired to correct both symmetry aberration and asymmetry aberration, a lens through which light passes twice (an optical element that contributes to the aberration) is used for correction of symmetry aberration. Selects a lens (an optical element that contributes to aberration) through which light passes once, and by moving each lens, both symmetric aberration and asymmetric aberration can be efficiently corrected.

【0059】

This will be described in the next embodiment.

【0060】

[Embodiment 4] FIG. 5 is an optical path diagram of an optical system in which a means for correcting asymmetric aberration is further added to the optical system of FIG. 9 is a lens that can move in the optical axis direction in the first lens group LG1, and 10 is a driving device for moving the lens 9. Further, the control device 5 can control both the drive devices 4 and 10.

【0061】

In this embodiment, symmetric aberrations (spherical aberrations, astigmatisms, curvature of field) and asymmetric aberrations (coma aberrations, distortions) are the aberrations that occur due to temperature rise due to exposure, changes in pressure pressure, changes in lighting conditions, and the like. Both are corrected.

【0062】

When aberration occurs due to these causes, the asymmetric aberration is first corrected by moving the lens 9 in the first lens group LG1 in the optical axis direction.

【0063】

When the NA of the optical system is large, the symmetry aberration changes slightly due to the movement of the lens 9. Next, by moving the lens 3 in the second lens group LG2 in the optical axis direction, the symmetry aberration can be corrected with almost no change in the asymmetry aberration. By the above procedure, in this embodiment, both asymmetric aberration and symmetric aberration are corrected. The technology for correcting both of these aberrations can also be applied to the optical systems of a few mobile phones.

【0064】

In the above description, the procedure of correcting the asymmetric aberration first and then correcting the symmetry aberration has been described, but the correction may be performed in the reverse order, and the asymmetry aberration may be corrected. And the correction of the symmetry aberration may be repeated alternately to improve the accuracy of the correction.

【0065】

Next, an example of applying the reflection / refraction type projection optical system of the present invention to the conventional example shown in FIG. 8 will be shown. FIG. 8 shows a known reflection / refraction type projection optical system (Example 1 of JP-A-10-20195), in which the lens near the concave mirror in the reciprocating optical path is moved in the optical axis direction. The amount of change in aberration when the lens is used will be described.

【0066】

Table 1 shows the amount of aberration when two concave lenses (indicated by LM) in the reciprocating optical path next to the concave mirror MR1 are simultaneously moved in the optical axis direction (in the direction of the concave mirror) by 1 μm.

【0067】

[table 1]

<img file="JP2001237165A_D0001.tif" />In the case of this example, the spherical aberration changes significantly, so the lens system LM is used to adjust the spherical aberration. At the same time, coma (asymmetrical component of wave surface aberration) and misalignment of the imaging point (due to changes in magnification and distortion) also change slightly.

【0068】

Therefore, when the present invention is applied to this embodiment, not only the lens system LM in the illustrated reciprocating optical path but also some lenses in the one-way optical path are simultaneously moved in the optical axis direction to change the magnification. Distortion and coma will be corrected.

【0069】

According to each of the above-described embodiments, by moving the lens of the reciprocating optical path portion through which light passes twice in the optical axis direction and using a method of correcting the symmetry aberration, the lens of the one-way optical path portion can be moved. Since the change in symmetry aberration is larger than that, the range of correctable aberration can be increased, and when correcting the same amount of aberration, it is possible to correct with a smaller stroke and in a faster time. It has the effect of being able to do it.

【0070】

Further, it is possible to change only the symmetric aberration without changing the asymmetric aberration, which has an effect that the aberration can be easily controlled.

【0071】

Further, since the effect of the present invention becomes large when the absorption by the glass material or the mirror is large, the ArF laser or F₂The effect is great in optical systems that use a laser as a light source.

【0072】

Further, when the NA is as large as 0.65 or more, the change in aberration due to changes in heat, atmospheric pressure, and lighting conditions becomes large, so that the effect of the present invention is large in an optical system having a large NA.

【0073】

[Effect of the invention]

As described above, according to the present invention, the symmetry aberration of the optical system can be effectively adjusted and corrected.

[Simple explanation of drawings]

[Figure 1]

Optical path diagram of the reflection / refraction type optical system used in the exposure apparatus of the present invention [Figure 2]

An optical path diagram explaining the aberration of the catadioptric system [Fig. 3]

Optical path diagram of catadioptric system with folding mirror [Fig. 4]

Optical path diagram of another type of catadioptric system without a beam splitter [Fig. 5]

Optical path diagram of a catadioptric system with means for correcting asymmetric aberrations [Fig. 6]

Optical path diagram of a conventional catadioptric system with a beam splitter [Fig. 7]

Optical path diagram of a conventional catadioptric system that forms an intermediate image [Fig. 8]

Optical path diagram of the catadioptric system disclosed in Japanese Patent Application Laid-Open No. 10-20195 [Explanation of symbols]

1 mask 2 wafer 3,9 Lens that can move in the optical axis direction 4,10 Drive device for moving the lens 5 Control device for controlling lens movement 6 Aberration measuring device LG1 1st lens group LG2 2nd lens group LG3 3rd lens group MR1 concave mirror MR2 folding mirror MR3 convex mirror BS cube type beam splitter