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Exposure apparatus having catadioptric projection optical system |
| RE39024 |
Exposure apparatus having catadioptric projection optical system
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| Patent Drawings: | |
| Inventor: |
Takahashi |
| Date Issued: |
March 21, 2006 |
| Application: |
09/665,184 |
| Filed: |
September 15, 2000 |
| Inventors: |
Takahashi; Tomowaki (Yokohama, JP)
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| Assignee: |
Nikon Corporation (Tokyo, JP) |
| Primary Examiner: |
Lester; Evelyn A. |
| Assistant Examiner: |
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| Attorney Or Agent: |
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| U.S. Class: |
250/203.7; 250/548; 355/53; 356/399; 356/400; 359/364; 359/434; 359/631; 359/651; 359/726; 359/732; 359/738; 359/800 |
| Field Of Search: |
359/364; 359/434; 359/629; 359/631; 359/636; 359/638; 359/649; 359/650; 359/651; 359/726; 359/727; 359/732; 359/738; 359/800; 355/67; 355/53; 356/399; 356/400; 250/203.7; 250/548 |
| International Class: |
G02B 3/00; G02B 17/00 |
| U.S Patent Documents: |
3504961; 3737215; 3897138; 3909115; 3955883; 4080048; 4386828; 4497015; 4592625; 4666273; 4685777; 4701035; 4770477; 4779966; 4812028; 4851978; 4953960; 4974919; 5052763; 5089913; 5194893; 5212593; 5220454; 5241423; 5251070; 5253110; 5260832; 5323263; 5333035; 5365051; 5402267; 5406415; 5414551; 5448408; 5506684; 5515207; 5534970; 5537260; 5583696; 5591958; 5592329; 5636066; 5668673; 5689377; 5691802; 5694241; 5706137; 5742436; 5805334; 5808805; 5861997; 5999333; 6392822 |
| Foreign Patent Documents: |
19726058; 0712019; 0717299; 0736789; 0770895; 0243950; 47-35017; 58-04112; 58-078115; 61-156737; 63-118115; 63-163319; 2-66510; 3-282527; 4-42208; 4-157412; 4-234722; 5-72478; 5-173065; 05-173065; 6-313845; 07140384; 07140385; 93/04391 |
| Other References: |
US 5,379,091, 1/1995, Tanitsu et al. (withdrawn) cited by examiner.
U.S. Pat. No. 5,379,091, issued Jan. 1995, now withdrawn from publication. cited by examiner.
U.S. Pat. No. 5,379,091 issued on Jan. 1995 to Tanitsu et al., now withdrawn. cited by examiner.
Japanese Publication No. 64-019317 (Jan. 1989) (Abstract only). cited by other.
Japanese Publication No. 55-012902 (Jan. 29, 1980)(Abstract Only). cited by other.
U.S. Appl. No. 09/659,376, filed Sep. 8, 2000, Toshihiro Sasaya, et al., Nikon Corporation, Japan. cited by other.
U.S. Appl. No. 09/766,486, filed Jan. 19, 2001, Tomowaki Takahashi, Nikon Corporation, Japan. cited by other.
U.S. Appl. No. 09/764,157, filed Jan. 19, 2001, Tomowaki Takahashi, Nikon Corporation, Japan. cited by other.
U.S. Appl. No. 09/709,518, filed Nov. 13, 2000, Hitoshi Matsuzawa, et al., Nikon Corporation, Japan. cited by other.
U.S. Appl. No. 09/659,375, filed Sep. 8, 2000, Tomowaki Takahashi, Nikon Corporation, Japan. cited by other.
U.S. Appl. No. 08/212,639, Takahashi, filed Mar. 10, 1994. cited by examin- er.
U.S. Appl. No. 08/299,305, Ota et al., filed Sep. 1, 1994. cited by examin- er.
U.S. Appl. No. 08/255,927, Nakashima et al., filed Jun. 7, 1994. cited by examiner.
U.S. Appl. No. 08/260,398, Nishi et al., filed Jun. 14, 1994. cited by exa- miner. |
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| Abstract: |
To use a beam splitting optical system smaller than the conventional beam splitters and to set a longer optical path between a concave, reflective mirror and an image plant. A light beam from an object surface travels through a first converging group to enter a beam splitter, and a light beam reflected by the beam splitter is reflected by a concave, reflective mirror to form an image of patterns on the object surface inside the concave, reflective mirror. A light beam from the image of the patterns passes through the beam splitter and thereafter forms an image of the patterns through a third converging group on an image plane. |
| Claim: |
What is claimed is:
1. A catadioptric projection optical system for projecting an image of a pattern of a first surface onto a second surface, said catadioptric projection optical systemcomprising: a first image-forming optical system for forming an intermediate image of the pattern of said first surface, said first image-forming optical system including: a first group with a positive refractive power, comprising a refractive lenscomponent, for converging a light beam from the pattern of said first surface; a second group with a positive refractive power, comprising a concave, reflective mirror for reflecting a light beam from said first group, for forming said intermediateimage of the pattern of said first surface; and a beam splitting optical system for changing a traveling direction of one of a light beam from said first group and a reflected light beam from said concave, reflective mirror; and a second image-formingoptical system for forming an image of said intermediate image on said second surface.
2. A catadioptric projection optical system according to claim 1, wherein said beam splitting optical system is defined as a beam splitter of which a beam splitter surface is arranged obliquely to an optical axis of said first group, said beamsplitter disposed on the optical axis of said first group and provided on the optical path between said concave, reflective mirror and said second image-forming optical system.
3. A eatadioptric projection optical system according to claim 1, wherein said beam splitting optical system is defined as a partial mirror of which a first reflective surface is arranged obliquely to an optical axis of said first group, saidpartial mirror provided between said first group and said second group so as to avoid being disposed on the optical axis of said first group, and wherein the light beam converged by said second group is guided to said second image-forming optical systemby a second reflective surface of said partial mirror, said second reflective surface being opposite to said first reflective surface of said partial mirror.
4. A catadioptric projection optical system according to claim 2, wherein said beam splitter is a prism-type shaped.
5. A catadioptric projection optical system according to claim 4, wherein said beam splitter is one of a polarizing beam splitter and a partially-reflective beam splitter.
6. A catadioptric projection optical system for projecting an image of a pattern of a first surface onto a second surface, comprising: a first image-forming optical system for forming an intermediate image of the pattern of said first surface,and a second image-forming optical system for forming an image of said intermediate image on said second surface, wherein said first image-forming optical system includes: a first group with a positive refractive power, comprising a refractive lenscomponent, for converging a light beam from the pattern of said first surface; a beam sputter for separating a part of a light beam from said first group by a beam-splitter surface arranged obliquely to an optical axis of said first group, said beamsplitter disposed on the optical axis of said first group; and a second group with a positive refractive power, comprising a concave, reflective mirror for reflecting the light beam separated by said beam splitter, for forming said intermediate image ofthe pattern between the concave, reflective mirror and the second image-forming optical system, said beam splitter provided between said concave, reflective mirror and said second image-forming optical system.
7. A catadioptric projection optical system according to claim 6, wherein said beam splitter is a prism-type shaped, and said intermediate image of the pattern of said first surface is formed inside said beam splitter.
8. A catadioptric projection optical system according to claim 6, wherein the following conditions are satisfied: p.sub.1+p.sub.3>0, p.sub.2<0, and |p.sub.1+p.sub.2+p.sub.3|<0.1, where p.sub.1, p.sub.2, and p.sub.3 are individualPetzval's sums of said first group, second group, and second image-forming optical system; and wherein the following conditions are satisfied: 0.1<|.beta..sub.12|<0.5 and 0.25<|.beta..sub.3|<2, where .beta..sub.12 is a magnification of fromthe pattern on said first surface to said intermediate image and .beta..sub.3 is a magnification of from said intermediate image to said image on the second surface.
9. A catadioptric projection optical system according to claim 7, wherein said beam splitter is one of a polarizing beam splitter and a partially-reflective beam splitter.
10. A catadioptric projection optical system for projecting an image of a pattern of a first surface onto a second surface, comprising a first image-forming optical system for forming an intermediate image of the pattern of said first surface,and a second image-forming optical system for forming an image of said intermediate image on said second surface, wherein said first image-forming optical system includes: a first group with a positive refractive power, comprising a refractive lenscomponent, for converging a light beam from the pattern of said first surface; a partial mirror for separating a part of a light beam from said first group by a first reflective surface arranged obliquely to an optical axis of said first group, saidpartial mirror-positioned so as to avoid being disposed on the optical axis of said first group; and a second group of a positive refractive power, comprising a concave, reflective mirror for reflecting the light beam of which the part is separated bysaid first reflective surface of said partial mirror, for forming said intermediate image of the pattern between said concave, reflective mirror and said second image-forming optical system, said partial mirror provided between said first group and saidsecond group, wherein the light beam converged by said second group is guided to said second image-forming optical system by a second reflective surface of said partial mirror, said second reflective surface being opposite to said first reflectivesurface of said partial mirror.
11. A catadioptric projection optical system according to claim 10, wherein the following conditions are satisfied: p.sub.1+p.sub.3>0, p.sub.2<0, and |p.sub.1+p.sub.2+p.sub.3|<0.1, where p.sub.1, p.sub.2, and p.sub.3 are individualPetzval's sums of said first group, second group, and second image-forming optical system; and wherein the following conditions are satisfied: 0.1<|.beta..sub.12|<0.5 and 0.25<|.beta..sub.3<2, where .beta..sub.12 is a magnification of fromthe pattern on said first surface to said intermediate image and .beta..sub.3 is a magnification of from said intermediate image to said image on the second surface.
12. An exposure apparatus comprising: a stage allowing a photosensitive substrate to be held on a main surface thereof, an illumination optical system for emitting exposure light of a predetermined wavelength and transferring a predeterminedpattern of a mask onto said substrate; and a catadioptric projection optical system provided between a surface on which the mask is disposed and said substrate, for projecting an image of the pattern of said mask onto said substrate, said catadioptricprojection optical system including: a first image-forming optical system for forming an intermediate image of the pattern of said mask, said first image-forming optical system having: a first group with a positive refractive power, comprising arefractive lens component, for converging a light beam from the pattern of said mask; a second group with a positive refractive power, comprising a concave, reflective mirror for reflecting a light beam from said first group, for forming saidintermediate image of the pattern of said mask; and a beam splitting optical system for changing a traveling direction of one of a light beam from said first group and a reflected light from said concave, reflective mirror; and a second image-formingoptical system for forming an image of said intermediate image on said substrate.
13. An exposure apparatus according to claim 12, wherein said beam splitting optical system is defined as a beam splitter of which a beam splitter surface is arranged obliquely to an optical axis of said first group, said beam splitter disposedon the optical axis of said first group and provided on the optical path between said concave, reflective mirror and said second image-forming optical system.
14. An exposure apparatus according to claim 12, wherein said beam splitting optical system is defined as a partial mirror of which a first reflective surface is arranged obliquely to an optical axis of said first group, said partial mirrorprovided between said first group and said second group so as to avoid being disposed on the optical axis of said first group, and wherein the light beam converged by said second group is guided to said second image-forming optical system by a secondreflective surface of said partial mirror, said second reflective surface being opposite to said first reflective surface of said partial mirror.
15. An exposure apparatus according to claim 13, wherein said beam splitter is a prism-type shaped.
16. An exposure apparatus according to claim 15, wherein said beam splitter is one of a polarizing beam splitter and a partially-reflective beam splitter.
17. An exposure apparatus comprising: a stage allowing a photosensitive substrate to be held on a main surface thereof; an illumination optical system for emitting exposure light of a predetermined wavelength and transferring a predeterminedpattern of a mask onto the substrate; and a catadioptric projection optical system provided between a surface on which said mask is disposed and said substrate, for projecting an image of the pattern of said mask onto said substrate, comprising a firstimage-forming optical system for forming an intermediate image of the pattern of said mask, and a second image-forming optical system for forming an image of said intermediate image on said substrate, wherein said first image-forming optical systemincludes, a first group with a positive refractive power, comprising a refractive lens component, for converging a light beam from the pattern of said mask; a beam splitter for separating a part alight beam from said first group by a beam-splittersurface arranged obliquely to an optical axis of said first group, said beam splitter disposed on the optical axis of said first group; and a second group with a positive refractive power, comprising a concave, reflective mirror for reflecting the lightbeam separated by said beam splitter, for forming said intermediate image of the pattern between the concave, reflective mirror and the second image-forming optical system, said beam sputter provided between said concave, reflective mirror and saidsecond image-forming optical system.
18. An exposure apparatus according to claim 17, wherein said beam splitter is a prism-type shaped, and said intermediate image of the pattern of said first surface is formed inside said beam splitter.
19. An exposure apparatus according to claim 17, wherein the following conditions are satisfied: p.sub.1+p.sub.2>0, p.sub.2<0, and |p.sub.1+p.sub.2+p.sub.3|<0.1, where p.sub.1, p.sub.2, and p.sub.3 are individual Petzval's sums of saidfirst group, second group, and second image-forming optical system; and wherein the following conditions are satisfied: 0.1<|.beta..sub.12|<0.5 and 0.25<|.beta..sub.3|<2, where .beta..sub.12 is a magnification of from the pattern on saidfirst surface to said intermediate image and .beta..sub.3 is a magnification of from said intermediate image to said image on the second surface.
20. An exposure apparatus according to claim 18, wherein said beam sputter is one of a polarizing beam splitter and a partially-reflective beam splitter.
21. An exposure apparatus comprising: a stage allowing a photosensitive substrate to be held on a main surface thereof; an illumination optical system for emitting exposure light of a predetermined wavelength and transferring a predeterminedpattern of a mask onto the substrate; and a catadioptric projection optical system provided between a surface on which said mask is disposed and said substrate, for projecting an image of the pattern of said mask onto said substrate, comprising a firstimage-forming optical system for forming an intermediate image of the pattern of said mask, and a second image-forming optical system for forming an image of said intermediate image on said substrate, wherein said first image-forming optical systemincludes: a first group with a positive refractive power, comprising a refractive lens component, for converging a light beam from the pattern of said mask; a partial mirror for separating a part of a light beam from said first group by a firstreflective surface arranged obliquely to an optical axis of said first group, said partial mirror positioned so as to avoid being disposed on the optical axis of said first group; and a second group of a positive refractive power, comprising a concave,reflective mirror for reflecting the light beam of which the part is separated by said first reflective surface of said partial mirror, for forming said intermediate image of the pattern between said concave, reflective mirror and said secondimage-forming optical system, said partial mirror provided between said first group and said second group, wherein the light beam converged by said second group is guided to said second image-forming optical system by a second reflective surface of saidpartial mirror, said second reflective surface being opposite to said first reflective surface of said partial mirror.
22. An exposure apparatus according to claim 21, wherein the following conditions are satisfied: p.sub.1+p.sub.3>0, p.sub.2<0, and |p.sub.1+p.sub.2+p.sub.3|<0.1, where P.sub.1, p.sub.2, and p.sub.3 are individual Petzval's sums of saidfirst group, second group, and second image-forming optical system; and wherein the following conditions are satisfied: 0.1<|.beta..sub.12|<0.5 and 0.25<|.beta..sub.2|<2, where .beta..sub.12 is a magnification of from the pattern on saidfirst surface to said intermediate image and .beta..sub.3 is a magnification of from said intermediate image to said image on the second surface.
23. A catadioptric projection optical system for projecting an image of a pattern of a first surface onto a second surface, said catadioptric projection optical system comprising: a first image-forming optical system, ; a second image-formingoptical system, ;and a partial mirror, wherein said first image-forming optical system includes: a first group with a positive refractive power, said first group comprising a refractive lens component; and a second group with a negative positiverefractive power, said second group comprising a concave, reflective mirror, said second image-forming optical system comprises a dioptric imaging system which includes a refractive lens component and an aperture stop, light from said first surfacepasses through in order said first group, said second group, said partial mirror, and said second image-forming optical system and thereafter said light reaches said second surface, said partial mirror is positioned so as to avoid disposing on an opticalpath of light that travels from said first group to said second group and is disposed on an optical path of light that travels from said second group to said second image-forming optical system, and an intermediate image of said pattern of said firstsurface is formed at a predetermined position of said optical path of light that travels from said second group to said second image-forming optical system, and the dioptric imaging system of said second image-forming optical system extends from theintermediate image of said pattern to a second image formed by said second image-forming optical system at said second surface.
24. A catadioptric projection optical system according to claim 23, wherein the following conditions are satisfied: p.sub.1+p.sub.3>0, p.sub.2<0, and |p.sub.1+p.sub.2+p.sub.3|<0.1, where P.sub.1, p.sub.2, and p.sub.3 are individualPetzval's sums of said first group, second group, and second image-forming optical system; and wherein the following conditions are satisfied: 0.1<|.beta..sub.12|<0.5 and 0.25<|.beta..sub.3|<2, where .beta..sub.12 is a magnification of fromthe pattern on said first surface to said intermediate image and .beta..sub.3 is a magnification of from said intermediate image to said image on the second surface.
25. A fabricating device method comprising: preparing a mask with a predetermined pattern; illuminating said mask with exposure light having a predetermined wavelength; and projecting a secondary image of said pattern onto a photosensitivesubstrate through a catadioptric optical system according to claim 1.
26. A catadioptric imaging optical system used in a projection exposure apparatus that transfers a pattern on a mask onto a substrate, comprising: a first imaging optical sub-system arranged in an optical path between the mask and thesubstrate, said first imaging optical sub-system comprising a first group with a lens, and a second group with a concave mirror, wherein said first imaging optical sub-system forms an intermediate image of the pattern; a second imaging opticalsub-system arranged in an optical path between said first imaging optical sub-system and the substrate, wherein said second imaging optical sub-system forms an image of the intermediate image on the substrate and comprises a dioptric imaging system whichextends from the intermediate image to the image of the intermediate image; and an optical path deflecting member arranged between said first group and said second group of said first imaging optical sub-system, wherein said optical path deflectingmember changes a direction of either a light beam from said first group or a light beam reflected by the concave mirror.
27. A catadioptric imaging optical system according to claim 26, wherein said second imaging sub-system comprises an optical axis along a straight line.
28. A catadioptric imaging optical system according to claim 27, wherein said first group has an optical axis, and wherein said optical path deflecting member comprises a beam splitter surface that is inclined with respect to the optical axisof said first group.
29. A catadioptric imaging optical system according to claim 28, wherein said optical path deflecting member comprises a prism-type beam splitter.
30. A catadioptric imaging optical system according to claim 27, wherein said first group has an optical axis, wherein said optical path deflecting member comprises a reflection member that is arranged at a region not including the optical axisof said first group, and wherein the reflection member comprises a reflection surface inclined with respect to the optical axis of said first group.
31. A catadioptric imaging optical system according to claim 27, wherein said first group has a positive refractive power and said second group has a positive power.
32. A catadioptric imaging optical system according to claim 26, wherein the following conditions are satisfied: p.sub.1+p.sub.3>0, |p.sub.1+p.sub.2+p.sub.3|<0.2, 0.1<|.beta..sub.12|0.5, and 0.25<|.beta..sub.3|<2, where p.sub.1,p.sub.2 and p.sub.3 are individual Petzval's sums of said first group, said second group, and said second imaging optical system, .beta..sub.12 is a magnification of an optical system positioned in an optical path from the mask to the intermediate image,and .beta..sub.3 is a magnification of an optical system positioned in an optical path from the intermediate image to the substrate.
33. A projection exposure apparatus that transfers a pattern on a mask onto a substrate, comprising: a catadioptric imaging optical system according to claim 26, wherein said catadioptric imaging optical system forms an exposure region at aposition out of an optical axis of said second imaging sub-system.
34. A projection exposure apparatus according to claim 31, wherein the reticle and the substrate are scanned at different speeds corresponding to the magnification of said catadioptric imaging optical system.
35. A method of imaging a pattern on a mask onto a substrate, comprising: guiding a light from the mask to a first group, wherein the first group comprises a lens; guiding the light from the first group to a second group, wherein the secondgroup comprises a concave mirror; forming an intermediate image of the pattern based on the light from the second group; guiding the light from the intermediate image to a dioptric imaging sub-system; forming an image of the intermediate image on thesubstrate based on the light from the dioptric imaging sub-system, the dioptric imaging sub-system extending from the intermediate image to the formed image of the intermediate image; and changing a direction of either the light beam from the firstgroup or the light beam reflected by the concave mirror, in a space between the first group and the second group.
36. A catadioptric imaging optical system used in a projection exposure apparatus that transfers a pattern on a mask onto a substrate, comprising: a first imaging optical sub-system arranged in an optical path between the mask and thesubstrate, said first imaging optical sub-system comprising a first group with a lens, and a second group with a concave mirror, wherein said first imaging optical sub-system forms an intermediate image of the pattern; a second imaging opticalsub-system arranged in an optical path between said first imaging optical sub-system and the substrate, wherein said second imaging optical sub-system forms an image of the intermediate image on the substrate; and an optical path deflecting memberarranged between said first group and said second group of said first imaging optical sub-system, wherein said optical path deflecting member changes a direction of either a light beam from said first group or a light beam reflected by the concavemirror, wherein the following conditions are satisfied: p.sub.1+p.sub.3>0, |p.sub.1+p.sub.2+p.sub.3<0.2, 0.1<|.beta..sub.12|<0.5, and 0.25<|.beta..sub.3|<2, where p.sub.1, p.sub.2 and p.sub.3 are individual Petzval's sums of said firstgroup, said second group, and said second imaging optical system, .beta..sub.12 is a magnification of an optical system positioned in an optical path from the mask to the intermediate image, and .beta..sub.3 is a magnification of an optical systempositioned in an optical path from the intermediate image to the substrate.
37. A catadioptric imaging optical system used in a projection exposure apparatus that transfers a pattern on a mask onto a substrate, comprising: a first imaging optical sub-system arranged in an optical path between the mask and thesubstrate, said first imaging optical sub-system comprising a first group with a lens, and a second group with a concave mirror, wherein said first imaging optical sub-system forms an intermediate image of the pattern: a second imaging optical sub-systemarranged in an optical path between said first imaging optical sub-system and the substrate, wherein said second imaging optical sub-system forms an image of the intermediate image on the substrate; and an optical path deflecting member arranged betweensaid first group and said second group of said first imaging optical sub-system, wherein said optical path deflecting member changes a direction of either a light beam from said first group or a light beam reflected by the concave mirror, wherein saidsecond imaging sub-system comprises an optical axis along a straight line said first group has a positive refractive power and said second group has a positive power, and the reticle and the substrate are scanned at different speeds corresponding to themagnification of said catadioptric imaging optical system.L |
| Description: |
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catadioptric projection optical system suitable for applications to projection optical systems for 1.1 or demagnifying projection in projection exposure apparatus such as steppers used in fabricating, forexample, semiconductor devices or liquid crystal display devices, etc., by photolithography process. More particularly, the invention relates to a catadioptric projection optical system of a magnification of 1/4 to 1/5 with a resolution of submicronorder in the ultraviolet wavelength region, using a reflecting system as an element in the optical system.
2. Related Background Art
In fabricating semiconductor devices or liquid crystal display devices, etc by photolithography process, the projection exposure apparatus is used for demagnifying through a projection optical system a pattern image on a reticle (or photomask,etc.) for example at a ratio of about 1/4 to 1/5 to effect exposure of the image on a wafer (or glass plate, etc.) coated with a photoresist or the like.
The projection exposure apparatus with a catadioptric projection optical system is disclosed, for example, in Japanese Laid-open Patent Application No. 2-66510, Japanese Laid-open Patent Application No. 3-282527, U.S. Pat. (USP) No. 5,089,913,Japanese Laid-open Patent Application No. 5-72478, or U.S. Pat. No. 5,052,763, No. 4,779,966, No. 4,65,77, No 4,701,035.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an exposure apparatus having a catadioptric projection optical system which can use a beam splitting optical system smaller than the conventional polarizing beam splitter and which is excellent inimage-forming performance, permitting a sufficiently long optical path of from the concave, reflective mirror to the image plane. Therefore, the catadioptric projection optical system has a space permitting an aperture stop to be set therein, based on asize reduction of the beam splitting optical system such as a polarizing beam splitter. The catadioptric projection optical system can be applied to the projection exposure apparatus of the scanning exposure method, based on use of a compact beamsplitting optical system. Besides the projection exposure apparatus of the one-shot exposure method, the catadioptric projection optical system can be also applier to recent apparatus employing a scanning exposure method such as the slit scan method orthe step-and-scan method, etc. for effecting exposure while relatively scanning the reticle and the wafer to the projection optical system.
To achieve the above object, as shown in FIG. 1, an exposure apparatus of the present invention comprises at least a wafer stage 3 allowing a photosensitive substrate W to be held on a main surface thereof, an illumination optical system 1 foremitting exposure light of a predetermined wavelength and transferring a predetermined pattern of a mask (reticle R) onto the substrate W, a catadioptric projection optical system 5 provided between a first surface P1 on which the mask R is disposed anda second surface P2 to which a surface of the substrate W is corresponded, for projecting an image of the pattern of the mask R onto the substrate W. The illumination optical system 1 includes an alignment optical system 110 for adjusting a relativepositions between the mask R and the wafer W, and the mask R is disposed on a reticle stage 2 which is movable in parallel with respect to the main surface of the wafer stage 3. The catadioptric projection optical system has a space permitting anaperture stop 6 to be set therein. The sensitive substrate W comprises a wafer 8 such as a silicon wafer or a glass plate, etc., and a photosensitive material 7 such as a photoresist or the like coating a surface of the wafer 8.
In particular, as shown in FIGS. 2, 17, and 31, the catadioptric projection optical system comprises a first image-forming optical system (G.sub.1(f.sub.1), G.sub.2(f.sub.2)) for forming an intermediate image 11 of the pattern of the mask R, anda second image-forming optical system (G.sub.3(f.sub.3)) for forming an image of the intermediate image 11 on the substrate reticle. The first image-forming optical system has a first group G.sub.1(f.sub.1) with a positive refractive power, comprising arefractive lens component, for converging a light beam from the pattern of the mask R, a second group G.sub.2(f.sub.2) with a positive refractive power, comprising a concave, reflective mirror M.sub.2 for reflecting a light beam from the first groupG.sub.1(f.sub.1), for forming the intermediate image 11 of the pattern of the mask R, and a beam splitting optical system 10PBS (including 10A, 10B, and 10C) or 12 as a beam splitting optical system for changing a traveling direction of one of a lightbeam from the first group G.sub.1(f.sub.1) and a reflected light from the concave, reflective mirror M.sub.2, and thereby a part of the light beam converged by the second group G.sub.2(f.sub.2) is guided to the second image-forming optical systemG.sub.3(f.sub.3). The parameter f.sub.1 means as a focus length of the first group G.sub.1 in the first image-forming optical system, the parameter f.sub.2 means as a focus length of the second group G.sub.2 in the first image-forming optical system,and the parameter f.sub.3 means as a focus length of a lens group G.sub.3 in the second image-forming optical system.
The catadioptric projection optical system in FIG. 2 is an optical system for projecting an image of a pattern of a first surface P1 onto a second surface P2, which has a first image-forming optical system (G.sub.1, G.sub.2) for forming anintermediate image 11 of the pattern of the first surface P1 and a second image-forming optical system (G.sub.3) for forming an image of the intermediate image 11 on the second surface P2.
The first image-forming optical system comprises a first group G.sub.1(f.sub.1) of a positive refractive power, comprising a refractive lens component, for converging a light beam from the pattern of the first surface P1, a prism type beamsplitter 10PBS for separating a part of a light beam from the first group by a beam splitter surface 10PBSa arranged obliquely to the optical axis AX1 of the first group, and a second group G.sub.2(f.sub.2) with a positive refractive power, comprising aconcave, reflective mirror M.sub.2 for reflecting the light beam separated by the prism type beam splitter 10PBS, for forming the intermediate image 11 of the pattern near the prism type beam splitter 10PBS, in which a part of the light beam converged bythe second group G.sub.2(f.sub.2) is separated by the prism type beam splitter 10PBS to be guided to the second image-forming optical system G.sub.3(f.sub.3). The prism type beam splitter is disposed on the optical axis AX1 of the first groupG.sub.1(f.sub.1) and provided between the concave, reflective mirror M.sub.2 and the second image-forming optical system.
In this case, it is desirable that the intermediate image 11 of the pattern be formed inside the prism type beam sputter 10PBS. Also, as shown in FIG. 2, it is desired that in order to prevent generation of flare due to repetitive reflectionsbetween the concave, reflective mirror M.sub.2 and the second surface P2, a polarizing beam sputter be used as the beam splitter 10PBS and a quarter wave plate 9 be placed between the polarizing beam splitter and the concave, reflective mirror M.sub.2. Further, it is desired that the optical system be telecentric at least on the image plane P2 side.
Next, the catadioptric projection optical system in FIG. 17 is an optical system for projecting an image of a pattern P10 on a first surface P1 onto a second surface P2 which has a first image-forming optical system (G.sub.1(f.sub.1),G.sub.2(f.sub.2)) for forming an intermediate image 11 of the pattern P10 of the first surface P1, and a second image-forming optical system (G.sub.3(f.sub.3)) for forming an image of the intermediate image 11 on the second surface P2.
The first image-forming optical system comprises a first group G.sub.1(f.sub.1) of a positive refractive power, comprising a refractive lens component, for converging a light beam from the pattern P10 of the first surface P1, a partial mirror 12for separating a part of the light beam from the first group by a first reflective surface 12a arranged obliquely to the optical axis AX1 of the first group, and a second group G.sub.2(f.sub.2) of a positive refractive power, comprising a concave,reflective mirror M.sub.2 for reflecting the light beam of which the part is separated by the partial mirror 12, for forming the intermediate image 11 of the pattern P10 near the partial mirror 12, in which a part of the light beam converged by thesecond group is guided to the second image-forming optical system G.sub.3(f.sub.3). The partial mirror 12 is positioned so as to avoid being disposed on the optical axis AX1 of the first group and provided between the first group and the second group. The partial mirror 12 further has a second reflective surface for guiding the reflected light beam from the concave, reflective mirror M.sub.2 to the second image-forming optical system, the second reflective surface 12b being opposite to the firstreflective surface 12a.
In this case, because the light beam reflected by a second surface 12b of the partial mirror 12 is used, it is desired that an image-forming range be slit or arcuate. Namely, the catadioptric projection optical system in FIG. 17 is suitable forapplications to the projection exposure apparatus of the scanning exposure method. In this case, because the use of the partial mirror 12 includes little influence of repetitive reflections, the quarter wave plate can be obviated.
In these arrangements, the following conditions should be preferably satisfied when individual Petzval sums of the first group G.sub.1(f.sub.1), the second group G.sub.2(f.sub.2), and the second image-forming optical system G.sub.3(f.sub.3) arep.sub.1, p.sub.2, p.sub.3 respectively. p.sub.1+p.sub.3>0 (1) p.sub.2<0 (2) |p.sub.1+p.sub.2+p.sub.3|<0.1 (3)
Further, the following conditions should be preferably satisfied when a magnification of primary image formation of from the pattern on the first surface P1 to the intermediate image is .beta..sub.12, a magnification of secondary image formationof from the intermediate image to the image on the second surface P2 is .beta..sub.3, and a magnification of from the first surface to the second surface is .beta.. 0 1.ltoreq.|.beta..sub.12|.ltoreq.0.5 (4) 0.25.ltoreq.|.beta..sub.3|.ltoreq.2 (5) 01.ltoreq.|.beta.|.ltoreq.0.5 (6)
The catadioptric projection optical system in FIG. 2 is suitably applicable to the projection exposure apparatus of the one-shot exposure method. In this case, because the prism type beam splitter 10PBS is used to separate the light beam comingfrom the concave, reflective mirror M.sub.2 from the light beam going to the concave, reflective mirror M.sub.2 and because the beam splitter 10PBS is located near the portion where the light beam from the concave, reflective mirror M.sub.2 is onceconverged to be focused, the prism type beam splitter 10PBS can be constructed in a reduced scale. In other words, in the catadioptric projection optical system, since an intermediate image 11 of the pattern of the first surface P1 is formed between theconcave, reflective mirror M.sub.2 and the second image-forming optical system, the diameter of the light beam traveling from the concave, reflective mirror M.sub.2 to the beam splitter 10PBS will become small.
Also, because the image is once formed between the concave, reflective mirror M.sub.2 and the image plane P2, an aperture stop 6 can be placed in the second image-forming optical system G.sub.3(f.sub.3). Accordingly, a coherence factor (.sigma. value) can be readily controlled. With regard to this, because after the primary image formation, the secondary image formation is made by the second image-forming optical system G.sub.3(f.sub.3), the working distance between a fore end lens in thesecond image-forming optical system G.sub.3(f.sub.3) and the image plane P2 can be secured sufficiently long. In particular, because the projection exposure apparatus of the one-shot exposure method employs the beam splitter 10PBS located near the planeof primary image formation, the beam splitter 10PBS can be made as small as possible.
Next, because the catadioptric projection optical system in FIG. 17 uses the partial mirror 12, a best image region on the image plane P2 is slit or arcuate, thus being suitable for applications to the projection exposure apparatus of thescanning exposure method. In this case, because the image is once formed near the partial mirror 12, the partial mirror 12 may be small in size and characteristics of a reflective film of the partial mirror 12 are stable.
Also, the optical path can be separated simply by providing the partial mirror 12 with a small angle of view. Namely, because a large angle of view is unnecessary for separation of the optical path, a sufficient margin is left in theimage-forming performance. With regard to this, ordinary catadioptric projection optical systems need a maximum angle of view of about 20.degree. or more for separation of the optical path, while an angle of view of the light beam entering the partialmirror 12 is about 10.degree., which is easy in aberration correction.
A so-called ring field optical system is known as a projection optical system for the scanning exposure method, and the ring field optical system is constructed to illuminate only an off-axis annular portion. It is, however, difficult for thering field optical system to have a large numerical aperture, because it uses an off-axis beam. Further, because optical members in that system are not symmetric with respect to the optical axis, processing, inspection, and adjustment of the opticalmembers are difficult, and accuracy control or accuracy maintenance is also difficult. In contrast with it, because the angle of view is not large in the present invention, the optical system is constructed in a structure with less eclipse of beam.
Since the first image-forming optical system (G.sub.1(f.sub.1), G.sub.2(f.sub.2)) and the second image-forming optical system G.sub.3(f.sub.3) are constructed independently of each other, the optical system is easy in processing, inspection, andadjustment of optical members, is easy in accuracy control and accuracy maintenance, and has excellent image-forming characteristics to realize a large numerical aperture.
Next, in the catadioptric projection optical system shown in FIG. 2 or 17, a Petzval sum of the entire optical system first needs to be set as close to 0, in order to further improve the performance of optical system. Therefore, conditions ofequations (1) to (3) should be preferably satisfied.
Satisfying the conditions of equations (1) to (3) prevents curvature of the image plane in the optical performance, which thus makes flatness of the image plane excellent. Above the upper limit of the condition of equation (3) (or ifp.sub.1+p.sub.2+p.sub.3.gtoreq.0.1), the image plane is curved as concave to the object plane; below the lower limit of the condition of equation (3) (or if p.sub.1+p.sub.2+p.sub.3.gtoreq.-0.1), the image plane is curved as convex to the object, therebyconsiderably degrading the image-forming performance.
When the conditions of equations (4) to (6) are satisfied as to the magnification .beta..sub.12 of primary image formation, the magnification .beta..sub.3 of secondary image formation, and the magnification .beta. of overall image formation, theoptical system can be constructed without difficulties. Below the lower limit of each condition of equation (4) to (6), the demagnifying ratio becomes excessive, which makes wide-range exposure difficult. Above the upper limit, the demagnifying ratiobecomes closer to magnifying ratios, which is against the original purpose of use for reduction projection in applications to the projection exposure apparatus.
In this case, because the condition of equation (4) is satisfied, the most part of the demagnifying ratio of the overall optical system relies on the first image-forming optical system. Accordingly, the beam splitter 10PBS or the partial mirror12 can be constructed in a small scale in particular. If the position of the beam splitter 10PBS in FIG. 2 or the partial mirror 12 in FIG. 6 as beam splitting means is made nearly coincident with the entrance pupil and the exit pupil of optical system,a shield portion of the pupil does not change against a change of object height, and therefore, no change of image-forming performance appears across the entire image plane.
Also, it is desired that such an optical system for exposure be telecentric at least on the image plane side in order to suppress a change of magnification against variations in the direction of the optical axis, of the image plane where thewafer or the like is located.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the presentinvention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art form this detailed description.
BRIEFDESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural drawing to show the basic structure of the exposure apparatus according to the present invention.
FIG. 2 is a structural drawing to show the basic structure of the catadioptric projection optical system 5 in FIG. 1.
FIG. 3 is an illustration of optical paths of a light beam traveling in the catadioptric projection optical system in FIG. 2.
FIG. 4 is an optical path development of a first embodiment of the catadioptric projection optical system in FIG. 2, the optical path comprising the optical paths OP1, OP2, OP3 shown in FIG. 3.
FIGS. 5 to 9 are aberration diagrams of the first embodiment.
FIG. 10 is an optical path development of the projection optical system in the second embodiment.
FIGS. 11 to 16 are aberration diagrams of the second embodiment.
FIG. 17 is a structural drawing to show the basic structure of the projection optical system in the third embodiment.
FIG. 18 is an optical path development of the projection optical system in the third embodiment.
FIGS. 19 to 24 are aberration diagrams of the third embodiment.
FIG. 25 is an optical path development of the projection optical system in the fourth embodiment.
FIGS. 26 to 30 are aberration diagrams of the fourth embodiment.
FIG. 31 is a structural drawing to show a structure of the catadioptric projection optical system applied to a common exposure apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various embodiments of the catadioptric projection optical system according to the present invention will be described with reference to the drawings. In the examples, the present invention is applied to the projection optical system in theprojection exposure apparatus for projecting an image of patterns of reticle onto a wafer coated with a photoresist. FIG. 1 shows a basic structure of the exposure apparatus according to the present invention. As shown in FIG. 1, an exposure apparatusof the present invention comprises at least a wafer stage 3 allowing a photosensitive substrate W to be held on a main surface 3a thereof, an illumination optical system 1 for emitting exposure light of a predetermined wavelength and transferring apredetermined pattern of a mask (reticle R) onto the substrate W, a light source 100 for supplying an exposure light to the illumination optical system 1, a catadioptric projection optical system 5 provided between a first surface P1 (object plane) onwhich the mask R is disposed and a second surface P2 (image plane) to which a surface of the substrate W is corresponded, for projecting an image of the pattern of the mask R onto the substrate W. The illumination optical system 1 includes an alignmentoptical system 110 for adjusting a relative positions between the mask R and the wafer W, and the mask R is disposed on a reticle stage 2 which is movable in parallel with respect to the main surface of the wafer stage 3. A reticle exchange system 200conveys and changes a reticle (mask R) to be set on the reticle stage 2. The reticle exchange system 200 includes a stage driver for moving the reticle stage 2 in parallel with respect to the main surface 3a of the wafer stage 3. The catadioptricprojection optical system 5 has a space permitting an aperture stop 6 to be set therein. The sensitive substrate W comprises a wafer 8 such as a silicon wafer or a glass plate, etc, and a photosensitive material 7 such as a photoresist or the likecoating a surface of the wafer 8. The wafer stage 3 is moved in parallel with respect to a object plane P1 by a stage control system 300. Further, since a main control section 400 such as a computer system controls the light source 100, the reticleexchange system 200, the stage control system 300 or the like, the exposure apparatus can perform a harmonious action as a whole.
The techniques relating to an exposure apparatus of the present invention are described, for example, in U.S. patent applications Ser. No 255,927, No. 260,398, No. 299,305, U.S. Pat. No. 4,497,015, No. 4,666,273, No. 5,194,893, No 5,253,110,No. 5,333,035, No. 5,365,051, No. 5,379,091, or the like. The reference of U.S patent application Ser. No. 255,927 teaches an illumination optical system (using a laser source) applied to a scan type exposure apparatus. The reference of U.S. patentapplication Ser. No. 260,398 teaches an illumination optical system (using a lamp source) applied to a scan type exposure apparatus. The reference of U.S. patent application Ser. No. 299,305 teaches an alignment optical system applied to a scan typeexposure apparatus. The reference of U.S. Pat. No. 4,497,015 teaches an illumination optical system (using a lamp source) applied to a scan type exposure apparatus. The reference of U.S. Pat. No. 4,666,273 teaches a step-and repeat type exposureapparatus capable of using the catadioptric projection optical system of the present invention. The reference of U.S. Pat. No. 5,194,893 teaches an illumination optical system, an illumination region, mask-side and reticle-side interferometers, afocusing optical system, alignment optical system, or the like. The reference of U.S. Pat. No. 5,253,110 teaches an illumination optical system (using a laser source) applied to a step-and-repeat type exposure apparatus. The '110 reference can beapplied to a scan type exposure apparatus. The reference of U.S. Pat. No. 5,333,035 teaches an application of an illumination optical system applied to an exposure apparatus. The reference of U.S. Pat. No. 5,365,051 teaches a auto-focusing systemapplied to an exposure apparatus. The reference of U.S. Pat. No. 5,379,091 teaches an illummation optical system (using a laser source) applied to a scan type exposure apparatus.
In each embodiment as described below, a lens arrangement is illustrated as an optical path development, for example as shown in FIG. 4. In each optical path development, a reflective surface is shown as a transmissive surface, and opticalelements are arranged in the order in which light from a reticle R passes. Also, a virtual plane of flat surface (for example r.sub.15) is used at a reflective surface of a concave, reflective mirror (for example r.sub.14). In order to indicate a shapeand separation of lens, for example as shown in FIG. 4, the pattern surface of reticle R is defined as the zeroth surface, surfaces that the light emergent from the reticle R passes in order before reaching the wafer W are defined as i-th surfaces (i=1,2, . . . ), and the sign for radii r.sub.1 of curvature of the i-th surfaces is determined as positive if a surface is convex to the reticle 10 in the optical path development. A surface separation between the i-th surface and the (i+1)-th surface isdefined as d.sub.1. SiO.sub.2 as a glass material means silica glass. A refractive index of silica glass for reference wavelength (193 nm) used is as follows.
silica glass: 1.56100
First Embodiment
The first embodiment is a projection optical system with a magnification of 1/4x, suitably applicable to the projection exposure apparatus of the one-shot exposure method (steppers etc.). This first embodiment is an embodiment corresponding tothe optical system of FIG. 2 as well. FIG. 4 is an optical path development of the projection optical system of the first embodiment. As shown in FIG. 4, light from the patterns on the reticle R travels through a first converging group G.sub.1consisting of four refractive lenses and then is reflected by a beam splitter surface (r.sub.10) in a cubic polarizing beam splitter 10A. An optical path of the light is corresponded to the optical path OP1 in FIG. 3. The reflected light passes througha quarter wave plate 9 (not shown in FIG. 4) to reach a second converging group G.sub.2 consisting of a negative meniscus lens L.sub.20 and a concave, reflective mirror M.sub.2. The light reflected by the second converging group G.sub.2 passes throughthe quarter wave plate (not shown in FIG. 4) to form an intermediate image of the patterns in the polarizing beam splitter 10A (see optical paths OP2 and OP3 in FIG. 4).
Then, light from the intermediate image, that is, a light beam having passed through the polarizing beam splitter 10A, then passes through a third converging group G.sub.3 consisting of fourteen refractive lenses to form a second intermediateimage of the patterns on the surface of wafer W. In this case, an aperture stop 6 is placed on a Fourier transform plane in the third converging group G.sub.3, i.e, between a positive meniscus lens L.sub.36 and a concave lens L.sub.37.
Also, as shown in FIG. 4, the first converging group G.sub.1 is composed of, in the order from the reticle R side, a positive meniscus lens L.sub.11 with a convex surface to the reticle R, a negative meniscus lens L.sub.12 with a convex surfaceto the reticle R, a double convex lens (hereinafter referred to simply as "convex lens") L.sub.13, and a double concave lens (hereinafter referred to simply as "concave lens") L.sub.14, and the second converging group G.sub.2 is composed of a negativemeniscus lens L.sub.20 with a concave surface to the reticle R and a concave, reflective mirror M.sub.2. Further, the third converging group G.sub.3 is composed of a positive meniscus lens L.sub.31 with a concave surface to the reticle R, a convex lendsL.sub.32, a positive meniscus lens L.sub.33 with a concave surface to the reticle R, a convex lens L.sub.34, a convex lens L.sub.35, a positive meniscus lens L.sub.36 with a convex surface to the reticle R, a concave lens L.sub.37, a convex lensL.sub.38, a convex lens L.sub.39, a negative meniscus lens L.sub.3A, with a concave surface to the reticle R, a convex lens L.sub.3B, a negative meniscus lens L.sub.3c with a convex surface to the reticle R, a positive meniscus lens L.sub.3D with aconvex surface to the reticle R, and a negative meniscus lens L.sub.3E with a convex surface to the reticle R.
A magnification of the total system is 1/4x (demagnification), a numerical aperture NA on the wafer W side (image side) is 0.4, and the object height is 30 mm.
The refractive lenses all are made of a kind of optical glass of fused quartz, which are corrected for axial and lateral chromatic aberrations for a wavelength band of 1 nm at the wavelength of 193 nm of the ultraviolet excimer laser light. Also, the optical system has excellent image-forming performance, as well corrected for spherical aberration, coma, astigmatism, and distortion up to a nearly zero aberration state, and the good image-forming performance can be retained even if theoptical system of FIG. 4 is proportionally enlarged two to three times.
Next Table 1 shows radii of curvature r.sub.1, surface separations d.sub.1, and glass materials in the first embodiment of FIG. 4. In the following table, the fifteenth surface is a virtual plane for indicating the concave, reflective mirror inthe optical path development.
TABLE-US-00001 TABLE 1 Glass Glass i r.sub.1 d.sub.1 Material i r.sub.1 d.sub.1 Material 0 -- 2.2 24 -140.60 6.0 S.sub.1O.sub.2 1 45.87 15.0 S.sub.1O.sub.2 25 -82.20 1.0 2 323.75 7.5 26 146.49 9.4 S.sub.1O.sub.2 3 4161.48 6.0 S.sub.1O.sub.2 27-114.12 32.9 4 56.56 11.7 28 84.53 6.0 S.sub.1O.sub.2 5 243.98 10.0 S.sub.1O.sub.2 29 -182.36 1.0 6 -89.98 7.3 30 48.17 6.0 S.sub.1O.sub.2 7 -50.58 6.0 S.sub.1O.sub.2 31 194.47 4.0 8 46.80 5.0 32 -48.51 5.6 S.sub.1O.sub.2 9 .infin. 30.0 S.sub.1O.sub.233 58.04 4.3 10 .infin. 52.6 34 207.40 8.2 S.sub.1O.sub.2 11 .infin. 27.0 35 -118.99 0.3 12 -76.04 6.9 S.sub.1O.sub.2 36 103.13 8.2 S.sub.1O.sub.2 13 -140.44 4.1 37 -61.92 3.7 14 -89.27 0.0 38 -38.44 6.7 S.sub.1O.sub.2 15 .infin. 4.1 39 -42.44 1.0 16140.44 6.9 S.sub.1O.sub.2 40 308.23 8.0 S.sub.1O.sub.2 17 76.04 79.6 41 -71.28 1.0 18 .infin. 30.0 S.sub.1O.sub.2 42 19.58 5.7 S.sub.1O.sub.2 19 .infin. 5.0 43 16.97 2.5 20 -41.51 6.0 S.sub.1O.sub.2 44 19.43 8.0 S.sub.1O.sub.2 21 -39.05 1.0 45 51.610.5 22 244.39 10.0 S.sub.1O.sub.2 46 108.17 3.7 S.sub.1O.sub.2 23 -64.38 1.0 47 39.10 7.0
Also, FIG. 5 to 7 show longitudinal aberration diagrams of the first embodiment, FIG. 8 shows a lateral chromatic aberration diagram of the first embodiment, and FIG. 9 shows transverse aberration diagrams of the first embodiment. In particular,FIG. 5 shows spherical aberration of the first embodiment, FIG. 6 shows astigmatism of the first embodiment, and FIG. 7 shows distortion of the first embodiment. In these aberration diagrams, symbols J, P, and Q represent respective characteristics whenthe used wavelength is changed in a selected range with respect to the reference wavelength. It is seen from these aberration, diagrams that though the numerical aperture is large, 0.4, in this example, the aberrations are well corrected in a wide imagecircle region. Further, chromatic aberration is well corrected as well.
Second Embodiment
The second embodiment is a projection optical system with a magnification of 1/4x, suitably applicable to the projection exposure apparatus of the scanning exposure method. This second embodiment is an embodiment as a modification of the opticalsystem of FIG. 2 as well. FIG. 10 is an optical path development of the projection optical system of the present embodiment, and FIG. 11 shows an illumination area on the reticle R. As shown in this FIG. 11, an arcuate illumination area P10 on thereticle R is illuminated by an illumination optical system not shown. Then, in FIG. 10, light from patterns in the illumination area P10 on the reticle R travels through a first converging group G.sub.1 consisting of four refractive lenses, and thenpasses a transmissive part of a junction surface in a cubic, partiallyrefiective, beam splitter 10B. A reflective film 10Ba with a reflectivity of approximately 100% is formed in a peripheral part of the junction surface of the partially-reflective beamsplitter 10B, and a portion other than this reflective film 10Ba is a transmissive surface with a transmittance of approximately 100%.
The reflected light reaches a second converging group G.sub.2 consisting of a negative meniscus lens L.sub.20 and a concave, reflective mirror M.sub.2, and light reflected by the second converging group G.sub.2 forms an intermediate image of thepatterns in the illumination area P10, near the reflective film 10Ba in the partially-reflective beam splitter 10B. Then light from the intermediate image is reflected by the reflective film lOBa, then passes through a third converging group G.sub.3consisting of fourteen refractive lenses, and forms a second intermediate image of the patterns on the surface of wafer W. Letting .beta. be a projection magnification of from reticle R to wafer W, the reticle area R is scanned upward at a predeterminedvelocity V.sub.R and in synchronization therewith the wafer W is scanned upward at a velocity .beta..cndot.V.sub.R, thus carrying out exposure in the scanning exposure method.
Also, as shown in FIG. 10, the first converging group G.sub.1 is composed of, in the order from the reticle R side, a convex lens L.sub.11, a concave lens L.sub.12, a positive meniscus lens L.sub.13 with a concave surface to the reticle R, and aconcave lens L.sub.14, and the second converging group G.sub.2 is composed of a negative meniscus lens L.sub.20 with a concave surface to the reticle R and a concave, reflective mirror M.sub.2. Further, the third converging group G.sub.3 is composed ofa positive meniscus lens L.sub.31, with a concave surface to the reticle R, a convex lens L.sub.32, a positive meniscus lens L.sub.33 with a concave surface to the reticle R, a convex lens L.sub.34, a convex lens L.sub.35, a positive meniscus lensL.sub.36 with a convex surface to the reticle R, a concave lens L.sub.37, a positive meniscus lens L.sub.38 with a concave surface to the reticle 10, a convex lens L.sub.39, a negative meniscus lens L.sub.3A with a concave surface to the reticle R, aconvex lends L.sub.3B, a negative meniscus lens L.sub.3C with a convex surface to the reticle R, a positive meniscus lens L.sub.3D with a convex surface to the reticle R, and a negative meniscus lens L.sub.3E with a convex surface to the reticle R.
A magnification of the total system is 1/4x (demagnification), a numerical aperture NA on the wafer W side (image side) is 0.5, and the object height is 22 mm. The optical system may be used in the one-shot exposure method.
The refractive lenses all are made of a kind of optical glass of fused quartz, which are corrected for axial and lateral chromatic aberrations for a wavelength band of 1 nm at the wavelength of 193 nm of the ultraviolet excimer laser light. Also, the optical system has excellent image-forming performance, as well corrected for spherical aberration, coma, astigmatism, and distortion up to a nearly zero aberration state.
Next Table 2 shows radii of curvature ri, surface separations d; and glass materials in the second embodiment of FIG. 10. In the following table, the fourteenth surface is a virtual plane for indicating the concave, reflective mirror in theoptical path development.
TABLE-US-00002 TABLE 2 Glass i r.sub.1 d.sub.1 Material i r.sub.1 d.sub.1 Material 0 -- 2.2 24 -75.11 1.0 1 45.63 10.0 S.sub.1O.sub.2 25 319.62 9.4 S.sub.1O.sub.2 2 -183.72 12.0 26 -119.09 32.9 3 -91.37 6.0 S.sub.1O.sub.2 27 56.25 6.0S.sub.1O.sub.2 4 47.38 11.7 28 -120.67 1.0 5 -221.10 10.0 S.sub.1O.sub.2 29 49.04 6.0 S.sub.1O.sub.2 6 -98.95 7.3 30 99.71 4.0 7 -110.83 6.0 S.sub.1O.sub.2 31 -48.50 5.6 S.sub.1O.sub.2 8 66.11 3.0 32 54.15 4.3 9 .infin. 40.0 S.sub.1O.sub.2 33 -361.488.2 S.sub.1O.sub.2 10 .infin. 77.7 34 -76.92 0.3 11 -78.96 7.2 S.sub.1O.sub.2 35 145.52 8.2 S.sub.1O.sub.2 12 -145.84 4.3 36 -71.54 3.7 13 -92.70 0.0 37 -37.19 6.7 S.sub.1O.sub.2 14 .infin. 4.3 38 -41.33 1.0 15 145.54 7.2 S.sub.1O.sub.2 39 194.05 8.0S.sub.1O.sub.2 16 78.96 77.7 40 -62.51 1.0 17 .infin. 40.0 S.sub.1O.sub.2 41 17.77 5.7 S.sub.1O.sub.2 18 .infin. 4.0 42 13.88 2.5 19 -40.58 6.0 S.sub.1O.sub.2 43 17.52 8.0 S.sub.1O.sub.2 20 -36.69 1.0 44 93.95 0.5 21 212.61 10.0 S.sub.1O.sub.2 45 98.193.7 S.sub.1O.sub.2 22 -65.47 1.0 46 31.30 7.0 23 -134.41 6.0 S.sub.1O.sub.2
Also, FIG. 12 to 14 show longitudinal aberration diagrams of the second embodiment, FIG. 15 shows a lateral chromatic aberration diagram of the second embodiment, and FIG. 16 shows transverse aberration diagrams of the second embodiment. Inparticular, FIG. 12 shows spherical aberration of the second embodiment, FIG. 13 shows astigmatism of the second embodiment, and FIG. 14 shows distortion of the second embodiment. It is seen from these aberration diagrams that although the numericalaperture is large as 0.5 in this example, the aberrations are well corrected in a wide image circle region. Further, chromatic aberration is well corrected as well.
Third Embodiment
The third embodiment is a projection optical system with a magnification of 1/4x, suitably applicable to the projection exposure apparatus of the scanning exposure method. This third embodiment is an embodiment of the optical system using apartial mirror as well. As shown in FIG. 17, the partial mirror 12 is provided between the first converging group G.sub.1 and the second converging group G.sub.2, and positioned so as to avoid being disposed on the optical axes AX1, AX2 of the firstconverging group G.sub.1 and the third converging group G.sub.3. The partial mirror 12 has a first reflective surface 12a arranged obliquely to the optical axis AX1 of the first converging group G.sub.1 and a second reflective surface 12b opposite tothe first reflective surface 12a.
FIG. 18 is an optical path development of the projection optical system of the third embodiment, and FIG. 19 shows an illumination region P10 on the reticle R. As shown in this FIG. 19, an arcuate illumination area P10 on the reticle R isilluminated by an illumination optical system 1. Then, in FIG. 18, light from patterns in the illumination area P10 on the reticle R travels through a first converging group G.sub.1 consisting of four refractive lenses and then passes beside the partialmirror 12. In other words, the first reflective surface 12a of the partial mirror 12 separates a part of the light from the first converging group G.sub.1.
This passing light reaches a second converging group G.sub.2 consisting of a negative meniscus lens L.sub.20 and a concave, reflective mirror M.sub.2, and light reflected by the second converging group G.sub.2 forms an intermediate image 11 ofthe patterns in the illumination area P10, near the partial mirror 12 (see FIG. 17). Then light from the intermediate image 11 is reflected by a second reflective surface 12b of the partial mirror 12 and thereafter passes through a third converginggroup G.sub.3 consisting of fourteen refractive lenses to form a second intermediate image of the patterns on the surface of wafer W. Also, an aperture stop 6 is placed on a Fourier transform plane in the third converging group G.sub.3, i.e., between aconvex lens L.sub.34 and a convex lens L.S. In this case, letting .beta. be a projection magnification of from reticle R to wafer W, the reticle area R is scanned upward at a predetermined velocity V.sub.R and in synchronization therewith the wafer 11is scanned upward at a velocity (.beta..cndot.V.sub.R, thus performing exposure in the scanning exposure method.
Also, as shown in FIG. 18, the first converging group G.sub.1 is composed of, in the order from the reticle R side, a positive meniscus lens L.sub.11 with a convex surface to the reticle R, a negative meniscus lens L.sub.12 with a convex surfaceto the reticle R, a convex lens L.sub.13, and a concave lens L.sub.14, and the second converging group G.sub.2 is composed of a negative meniscus lens L.sub.20 with a concave surface to the reticle R, and a concave, reflective mirror M.sub.2. Further,the third converging group G.sub.3 is composed of a negative meniscus lens L.sub.31 with a concave surface to the reticle R, a positive meniscus lens L.sub.32 with a concave surface to the reticle R, a positive meniscus lens L.sub.33 with a concavesurface to the reticle R, a convex lens L.sub.34, a convex lens L.sub.35, a positive meniscus lens L.sub.36 with a convex surface to the reticle R, a concave lens L.sub.37, a positive meniscus lens L.sub.38 with a concave surface to the reticle R, aconvex lens L.sub.39, a negative meniscus lens L.sub.3A with a concave surface to the reticle R, a convex lens L.sub.3B, a negative meniscus lens L.sub.3C with a convex surface to the reticle R, a positive meniscus lens L.sub.3D with a convex surface tothe reticle R, and a negative meniscus lens L.sub.3E with a convex surface to the reticle R.
A magnification of the total system is 1/4x (demagnification), a numerical aperture NA on the wafer 11 side (image side) is 0.4, and the object height is 26 mm. The optical system may be used in the one-shot exposure method.
The refractive lenses all are made of a kind of optical glass of fused quartz, which are corrected for axial and lateral chromatic aberrations for a wavelength band of 1 nm at the wavelength of 193 nn of the ultraviolet excimer laser light. Also, the optical system has excellent image-forming performance, as well corrected for spherical aberration, coma, astigmatism, and distortion up to a nearly zero aberration state, and the good image-forming performance can be retained even if theoptical system is proportionally enlarged two to three times.
Next Table 3 shows radii of curvature r.sub.1, surface separations d.sub.1 and glass materials in the third embodiment of FIGS. 17 and 18. In the following table, the fourteenth surface is a virtual plane for indicating the concave, reflectivemirror in the optical path development.
TABLE-US-00003 TABLE 3 Glass i r.sub.1 d.sub.1 Material i r.sub.1 d.sub.1 Material 0 0 2.2 24 140.91 9.4 S.sub.1O.sub.2 1 38.17 10.0 S.sub.1O.sub.2 25 -191.84 32.9 2 76.72 12.0 26 92.51 8.0 S.sub.1O.sub.2 3 142.94 6.0 S.sub.1O.sub.2 27 -164.051.0 4 32.99 11.7 28 58.31 7.0 S.sub.1O.sub.2 5 36.73 10.0 S.sub.1O.sub.2 29 427.83 4.0 6 -337.52 6.5 30 -43.79 4.0 S.sub.1O.sub.2 7 -51.05 6.0 S.sub.1O.sub.2 31 1615.36 3.0 8 46.99 34.6 32 -48.72 8.2 S.sub.1O.sub.2 9 .infin. 30.3 33 -43.49 0.3 10.infin. 69.6 34 165.95 8.2 S.sub.1O.sub.2 11 -87.27 8.0 S.sub.1O.sub.2 35 -82.87 3.7 12 -177.44 4.8 36 -43.10 6.7 S.sub.1O.sub.2 13 -101.17 0.0 37 -50.06 1.0 14 .infin. 4.8 38 75.16 7.0 S.sub.1O.sub.2 15 177.44 8.0 S.sub.1O.sub.2 39 -168.78 1.0 1687.27 100.0 40 21.81 7.0 S.sub.1O.sub.2 17 .infin. 14.6 41 17.17 3.0 18 -36.36 8.0 S.sub.1O.sub.2 42 21.02 8.0 S.sub.1O.sub.2 19 -40.19 1.0 43 97.85 1.0 20 -579.38 6.0 S.sub.1O.sub.2 44 17.80 3.7 S.sub.1O.sub.2 21 -39.93 1.0 45 13.10 6.9 22 -280.59 8.0S.sub.1O.sub.2 23 -108.42 1.0
Also, FIG. 20 to 22 show longitudinal aberration diagrams of the third embodiment, FIG. 23 shows a lateral chromatic aberration diagram of the third embodiment, and FIG. 24 shows transverse aberration diagrams of the third embodiment. Inparticular, FIG. 20 shows spherical aberration of the third embodiment, FIG. 21 shows astigmatism of the third embodiment, and FIG. 22 shows distortion of the third embodiment. It is seen from these aberration diagrams that although the numericalaperture is large as 0.4 in this example, the aberrations are well corrected in a wide image circle region. Further, chromatic aberration is well corrected as well.
Fourth Embodiment
The fourth embodiment is a projection optical system with a magnification of 1/4x, suitably applicable to the projection exposure apparatus of the one-shot exposure method (steppers etc.). This fourth embodiment is an embodiment as amodification of the optical system of FIG. 2 as well. FIG. 25 is an optical path development of the projection optical system of the fourth embodiment. As shown in FIG. 25, light from patterns on the reticle R travels through a first converging groupG.sub.1 consisting of four refractive lenses and then enters a beam splitter surface 10Ca in a polarizing beam splitter 10C of a rectangular parallelepiped. The polarizing beam splitter 10C in the present embodiment is of a rectangular parallelepiped,and an incident surface (r.sub.9) of the illumination light is wider by a region 13 than a projection image of the beam splitter surface 10Ca. This permits the polarizing beam splitter 10C in FIG. 25 to be constructed thinner than the polarizing beamsplitter 10A in FIG. 4.
A light beam having passed through the beam sputter surface 10Ca passes through a quarter wave plate 9 (not shown in FIG. 25) to reach a second converging group G.sub.2 consisting of a negative meniscus lens L.sub.20 and a concave, reflectivemirror M.sub.2, and light reflected by the second converging group G.sub.2 travels through the quarter wave plate 9 (not shown FIG. 25), then is reflected by the beam splitter surface 10Ca in the polarizing beam splitter 10C, and forms an intermediateimage 11 of the patterns at a position in the vicinity of the polarizing beam sputter 10C.
Then a light beam from the intermediate image 11 passes through a third converging group G.sub.3 consisting of fourteen refractive lenses to form a second intermediate image of the patterns on the surface of wafer W. In this case, an aperturestop 6 is placed on a Fourier transform plane in the third converging group G.sub.3, that is, between a positive meniscus lens Lag and a convex lens L.sub.39.
Also, as shown in FIG. 25, the first converging group G.sub.1 is composed of, in the order from the reticle R side, a positive meniscus lens L.sub.11 with a convex surface to the reticle R, a concave lens L.sub.12, a convex lens L.sub.13, and aconcave lens L.sub.14, and the second converging group G.sub.2 is composed of a negative meniscus lens Leo with a concave surface to the reticle R, and a concave, reflective mirror M.sub.2. Further, the third converging group G.sub.3 is composed of apositive meniscus lens L.sub.31 with a concave surface to the reticle R, a convex lens L.sub.32, a negative meniscus lens L.sub.33 with a concave surface to the reticle R, a convex lens L.sub.34, a convex lends L.sub.35, a positive meniscus lens L.sub.36with a convex surface to the reticle R, a concave lens L.sub.37 a positive meniscus lens L.sub.38 with a concave surface to the reticle R, a convex lens L.sub.39, a negative meniscus lens L.sub.3A with a concave surface to the reticle R, a convex lensL.sub.3B, a negative meniscus lens L.sub.3C with a convex surface to the reticle R, a positive meniscus lens L.sub.3D with a convex surface to the reticle R, and a negative meniscus lens L.sub.3E with a convex surface to the reticle R.
A magnification of the total system is 1/4x (demagnification), a numerical aperture NA on the wafer 11 side (image side) is 0.6, and the object height is 20 mm.
The refractive lenses all are made of a kind of optical glass of fused quartz, which are corrected for axial and lateral chromatic aberrations for a wavelength band of 1 nm at the wavelength of 193 nm of the ultraviolet excimer laser light. Also, the optical system has excellent image-forming performance, as well corrected for spherical aberration, coma, astigmatism, and distortion up to a nearly zero aberration state, and the good image-forming performance can be retained even if theoptical system of FIG. 25 is proportionally enlarged two to three times.
Next Table 4 shows radii of curvature r.sub.1, surface separations d.sub.1 and glass materials in the fourth embodiment of FIG. 25. In the following table, the fourteenth surface is a virtual plane for indicating the concave, reflective mirrorin the optical path development.
TABLE-US-00004 TABLE 4 Glass i r.sub.1 d.sub.1 Material i r.sub.1 d.sub.1 Material 0 0 2.2 24 -95.92 1.0 1 43.62 8.0 S.sub.1O.sub.2 25 426.51 8.4 S.sub.1O.sub.2 2 319.17 12.6 26 -155.92 32.9 3 -250.41 6.0 S.sub.1O.sub.2 27 65.87 7.0S.sub.1O.sub.2 4 42.75 11.7 28 -861.00 1.0 5 1371.37 10.0 S.sub.1O.sub.2 29 45.43 6.0 S.sub.1O.sub.2 6 -83.00 7.3 30 144.51 6.0 7 -46.47 6.0 S.sub.1O.sub.2 31 -47.72 3.6 S.sub.1O.sub.2 8 73.09 5.0 32 69.88 4.3 9 .infin. 40.0 S.sub.1O.sub.2 33 -139.826.2 S.sub.1O.sub.2 10 .infin. 60.7 34 -63.75 3.3 11 -78.96 7.2 S.sub.1O.sub.2 35 164.20 7.2 S.sub.1O.sub.2 12 -145.84 4.3 36 -61.66 3.7 13 -92.70 0.0 37 -35.40 6.7 S.sub.1O.sub.2 14 .infin. 4.3 38 -42.77 1.0 15 145.84 7.2 S.sub.1O.sub.2 39 194.25 8.0S.sub.1O.sub.2 16 78.96 60.7 40 -64.00 1.0 17 .infin. 40.0 S.sub.1O.sub.2 41 21.24 5.7 S.sub.1O.sub.2 18 .infin. 40.0 42 16.45 1.5 19 -48.19 6.0 S.sub.1O.sub.2 43 17.66 9.0 S.sub.1O.sub.2 20 -39.43 1.0 44 103.14 0.5 21 99.65 10.0 S.sub.1O.sub.2 4560.80 3.7 S.sub.1O.sub.2 22 -69.37 1.0 46 40.36 23 -82.13 6.0 S.sub.1O.sub.2
Also, FIG. 26 to 28 show longitudinal aberration diagrams of the fourth embodiment, FIG. 29 shows a lateral chromatic aberration diagram of the fourth embodiment, and FIG. 30 shows transverse aberration diagrams of the fourth embodiment. Inparticular, FIG. 26 shows spherical aberration of the fourth embodiment, FIG. 27 shows astigmatism of the fourth embodiment, and FIG. 28 shows distortion of the fourth embodiment. It is seen from these aberration diagrams that although the numericalaperture is large as 0.6 in this example, the aberrations are well corrected in a wide image circle region. Further, chromatic aberration is well corrected as well.
It is preferred that the conditions of equations (1) to (6) be satisfied in the present invention, and thus, correspondence is next described between each embodiment as described above and the conditions of equations. First, Table 5 to Table 8each show the radius of curvature r of the concave, reflective mirror M.sub.2, focal lengths f.sub.1 of the i-th converging groups G.sub.1 (i=1 to 3), Petzval sums p.sub.1, apparent refractive indices n.sub.1, image magnifications .beta..sub.1 amagnification .beta..sub.12 of a combinational system of the first converging group G.sub.1 with the second converging group G.sub.2, an image magnification .beta..sub.3 of the third converging group G.sub.3, a Petzval sum p of the total system, and amagnification .beta. of the total system in each embodiment as described above. Here, the total system is represented by G.sub.T, and blocks for Petzval sum p, and image magnification .beta..sub.1 corresponding to the total system G.sub.T indicate thePetzval sum and image magnification of the total system, respectively.
TABLE-US-00005 TABLE 5 Specifications of first embodiment r f.sub.1 p.sub.2 n.sub.1 .beta..sub.3 .beta..sub.12 G.sub.1 -- -197.278 -0.00887 0.60199 0.47913 -0.32802 G.sub.2 -89.277 56.4187 -0.02674 -0.66285 -0.68461 G.sub.3 -- -303.1767 0.03546-0.09302 -0.76215 -0.76215 G.sub.T -- -- -0.00015 -- 0.25004 0.25004
TABLE-US-00006 TABLE 6 Specifications of second embodiment r f.sub.1 p.sub.4 n.sub.1 .beta..sub.3 .beta..sub.12 G.sub.1 -- -236.848 -0.00836 0.505038 0.4993 -0.33286 G.sub.2 -92.707 58.5864 -0.02575 -0.662866 -0.66665 G.sub.3 -- -206.083 0.03442-0.140978 -0.750195 -0.750195 G.sub.T -- -- 0.00032 -- 0.20 0.24971
TABLE-US-00007 TABLE 7 Specifications of third embodiment r f.sub.1 p.sub.4 n.sub.1 .beta..sub.1 .beta..sub.3 G.sub.1 -- -313.155 -0.00749 0.426342 0.53714 -0.33331 G.sub.2 -101. 66.2825 -0.02395 -0.629935 -0.620527 175 G.sub.3 -- -696.9560.03173 -0.045219 -0.75104 -0.75104 G.sub.T -- -- 0.00029 -- 0.25033 0.25033
TABLE-US-00008 TABLE 8 Specifications of fourth embodiment r f.sub.1 p.sub.3 n.sub.1 .beta..sub.2 .beta..sub.4 G.sub.1 -- -105.504 -0.01079 0.87843 0.46888 -0.39211 G.sub.2 -92. 58.586 -0.02575 -0.66287 -0.83627 7068 G.sub.3 -- -107.983 0.03733-0.24808 -0.63959 -0.63959 G.sub.T -- -- 0.00079 -- 0.25079 0.25079
Further, based on Table 5 to Table 8, values are calculated for (P.sub.1+P.sub.3), P.sub.2, |P.sub.1+P.sub.2+P.sub.3|, |.beta..sub.12|, |.beta..sub.3|, and |.beta.| in each embodiment, and the following Table 9 shows the calculated values.
TABLE-US-00009 TABLE 9 Table of correspondence conditions Conditions embodiment 1 2 3 4 (1) p.sub.1 + p.sub.3 > 0 0.02659 0.026606 0.02424 0.02654 (2) p.sub.2 < 0 -0.02674 -0.02575 -0.02395 -0.02575 (3) |p.sub.1 + p.sub.2 + p.sub.3| <0.1 0.00015 0.00031 0.00029 0.00079 (4) 0.1 .ltoreq. |.beta..sub.12| .ltoreq. 0.5 0.32802 0.33286 0.33331 0.39231 (5) 0.25 .ltoreq. |.beta..sub.3| .ltoreq. 2 0.76215 0.7502195 0.75104 0.63959 (6) 0.1 .ltoreq. |.beta.| .ltoreq. 0.5 0.25004 0.249710.25033 0.25079
From this table, it is seen that either one of the above-described embodiments satisfies the conditions of equations (1) to (6)
The embodiments as described above employed quartz as a glass material for forming the refractive optical system, but another optical glass such as fluorite may be used.
Next, an embodiment of a common exposure apparatus using the catadioptric projection optical system 5 of the present invention. In this embodiment, as shown in FIG. 31, the first converging group G.sub.1 includes a reflector 14 changing atraveling direction of light that travels in the first converging group G.sub.1. Therefore, the optical axis AX1 of the first converting group G.sub.1 is constituted by optical axes AX1a and AX1b as shown in FIG. 31. The techniques relating to anexposure apparatus using a catadioptric projection optical system is described, for example, in Japanese Laid-Open Patent Application No. 5-72478, or the like.
Thus, the present invention is by no means limited to the above-described embodiments, but may employ a variety of constitutions within a range not departing from the essence of the present invention.
Since the catadioptric projection optical system of FIG. 2 is so arranged that the image is once formed between the concave, reflective mirror and the second plane (image plane), there are advantages that a compact prism type beam splitter can beused and that an optical path between the concave, reflective mirror and the image plane can be set long. Accordingly, deterioration may be reduced for image-forming characteristics due to nonuniformity of characteristics in the semitransparent surfaceof beam splitter, and the working distance can be extended. In other words, the catadioptric projection optical system can secure a sufficiently long optical path to the wafer (image plane P2), of the illumination light reflected by the concave,reflective mirror M.sub.2, because an intermediate image is formed between the mirror M.sub.2 and the second image-forming optical system G.sub.3. Therefore, a number of refractive lenses can be arranged in the optical path to achieve satisfactoryimage-forming performance. This also caused an effect that a distance between a wafer-side end face of refractive lens and the wafer, which is the working distance, was long enough.
Also, different from the ring field optical system for projecting only an annular part using an off-axis light beam, the optical system of the invention includes an advantage that it can employ the one-shot exposure method under a high numericalaperture.
Since an aperture stop can be placed in the second image-forming optical system, the optical system of the invention can enjoy an advantage that the a value being a coherence factor can be freely controlled.
In the case of the conventional catadioptric systems, adjustment was difficult because of eccentricity of optical axis, and thus, image-forming performance as designed was rarely able to be achieved. In contrast, the catadioptric projectionoptical system according to the present invention permits independent adjustment of the first image-forming optical system and the second image-forming optical system, and after the adjustment the two image-forming optical systems may be set with theoptical axis approximately vertical, which facilitates adjustment of eccentricity etc.
Since the image magnification by the first image-forming optical system can be freely selected, an excellent optical performance state can be realized.
In this case, an advantage of a further size reduction of the beam splitter can be attained by forming the intermediate image inside the prism type beam splitter.
Next, because the second catadioptric projection optical system of FIG. 17 is so arranged that the image is once formed between the concave, reflective mirror and the second plane (image plane), there are advantages that a compact partial mirrorcan be used and that the optical path between the concave, reflective mirror and the image plane can be set long. Further, when the partial mirror is used, the best image region is, for example, arcuate or slit as eccentric from the optical axis. Suchan image region is suitable for the projection exposure apparatus of the scanning exposure method.
Next, when the conditions of equations (1) to (3) are satisfied, the Petzval sum of the total optical system readily becomes nearly 0, so that the projection image surface becomes approximately fiat. Further, when the conditions of equations (4)and (5) are satisfied, a magnification balance becomes reasonable, and the optical system can be easily constructed.
From the invention thus described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obviousto one skilled in the art are intended to be included within the scope of the following claims. The basic Japanese Application No. 6-90837 filed on Apr. 28, 1994 is hereby incorporated by reference.
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