JPH1010431A - Catoptric system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact catadioptric system having a large numerical aperture on an image side and resolution in quarter micron unit in an ultraviolet wavelength region by providing a 1st image-formation optical system forming an intermediate image, a 2nd image-formation optical system forming a reduced image and a 1st optical path deflecting member deflecting light and satisfying a specified condition. SOLUTION: The 1st image-formation optical system S1 has reducing image- formation magnification, and the burden of refractive power on the 2nd image- formation optical system S2 is reduced. As a result, the numerical aperture on the image side of the optical system is made larger, and the optical system S2 is prevented from getting large and complicated. Namely, this catadioptric system has the resolution in quarter micron unit in the ultraviolet wavelength region despite of the compact optical system having the large numerical aperture on the image side. Furthermore, it satisfies the conditions 0.75<|β1|<0.95 and 0.13<L1/LM<0.35. Provided that β1 is the image-formation magnification of the optical system S1, L1 is a distance between the optical axis intersection of the optical systems S1 and S2 and an object surface, and LM is an axial distance between the object surface and a concave reflection mirror CM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catadioptric reduction optical system having a reflecting surface and a refracting surface. The present invention relates to a catadioptric optical system suitable for an optical system and having a resolution of a quarter micron unit in an ultraviolet wavelength region.

[0002]

2. Description of the Related Art In a photolithography process for manufacturing a semiconductor device or the like, a wafer (or glass) on which a photomask or a reticle (hereinafter referred to as a "mask") is coated with a photoresist or the like via a projection optical system. Projection exposure apparatus for transferring onto a plate or the like is used. In this type of projection exposure apparatus, as the degree of integration of semiconductor elements and the like increases, the resolving power required for a projection optical system has further increased. In order to satisfy the requirement regarding the resolving power, it is necessary to shorten the wavelength of the illumination light and increase the image-side numerical aperture (NA) of the projection optical system. However, if the wavelength of the illumination light is shortened, light absorption occurs, and the types of optical materials that can be used practically are limited. For example, in the case of light having a wavelength of 300 nm or less, the only practically usable optical materials are quartz and fluorite.

By the way, the Abbe number of quartz and the Abbe number of fluorite are not sufficiently different from each other to correct chromatic aberration. Therefore, for example, in the case of light having a wavelength of 300 nm or less, it is difficult to correct various aberrations such as chromatic aberration if the projection optical system is constituted only by a refractive system made of quartz or fluorite. On the other hand, chromatic aberration does not occur in the reflection system.
Therefore, as a projection optical system of a projection exposure apparatus, various catadioptric systems in which a reflection system and a refraction system are combined have been proposed. A type in which an intermediate image is formed only once in the optical path of an optical system is disclosed in JP-A-63-16 / 1988.
No. 3319, Japanese Patent Publication No. 7-111512, Japanese Patent Publication No. 5-25170, USP-4,799,966.
There is known a catadioptric optical system disclosed in Japanese Patent Application Laid-Open Publication No. HEI 10-125702.

[0004]

Generally, in a catadioptric optical system for forming an object image based on a light beam including a light ray from an on-axis object point, a beam splitter having a transmission / reflection surface for deflecting an optical path is used. There is a need. However,
In a catadioptric optical system using a beam splitter, internal reflection occurs due to reflected light from a wafer positioned on the image plane, or internal reflection at a refraction surface of an optical system arranged closer to the image side than the beam splitter. It is easy to generate stray light which causes flare and uneven illumination on the transmission / reflection surface of the beam splitter or the like. To increase the numerical aperture on the image side of the optical system, a large beam splitter is required, and an increase in exposure time due to a loss of light amount in the beam splitter causes a decrease in throughput in a semiconductor manufacturing process. It should be noted that JP-A-6-30097
As disclosed in Japanese Unexamined Patent Publication No. 3 (1993) -301 and the like, a polarizing beam splitter can be employed as a beam splitter in order to avoid a light amount loss. However, it is extremely difficult to manufacture a large polarizing beam splitter according to the numerical aperture, and the non-uniformity, angular characteristics, light absorption, phase change, etc. of the transmission / reflection film cause deterioration of the imaging characteristics.

On the other hand, in a catadioptric optical system that forms an object image without using a light ray from an on-axis object point, that is, a ring field optical system, a plane reflecting mirror is arranged near an intermediate image formed to form a beam splitter. Can be used to realize optical path deflection (optical path division). For example, in a step-and-scan type projection exposure apparatus using a ring field optical system as a projection optical system, a mask and a wafer are simultaneously moved relative to the projection optical system, so that a mask pattern is formed in each shot area of the wafer. Is exposed by scanning. If an intermediate image is formed a plurality of times in the ring field optical system, the optical path length of the optical system becomes longer.
Further, when a plurality of concave reflecting mirrors are used in the ring field optical system applied to the projection exposure apparatus, it is necessary to largely separate the exposure region from the optical axis for the optical path deflection, and it is inevitable that the optical system becomes larger. From the above, a ring field optical system having one concave reflecting mirror and forming an intermediate image only once is desirable. Of the above publications and specifications, Japanese Patent Publication No. 7-111
No. 512 and US Pat. No. 4,779,966 disclose a ring field optical system having one concave reflecting mirror and forming an intermediate image only once.

First, in the catadioptric optical system disclosed in US Pat. No. 4,779,966, a concave reflecting mirror is arranged on the reduction side closer to the image plane than the position where the intermediate image is formed. However, since the numerical aperture on the reduction side is larger than that on the object plane side, it is difficult to deflect the optical path on the reduction side, and it is not possible to secure a large numerical aperture NA on the image side of the optical system. as a result,
Sufficient resolution cannot be secured, and enlargement of the concave reflecting mirror is inevitable. On the other hand, in Japanese Patent Publication No. Hei 7-111512, a first imaging optical system for forming an intermediate image is configured to be completely symmetrical, including a concave reflecting mirror. The intermediate image formed via the first imaging optical system is a 1: 1 image of the object plane. In this manner, the configuration for forming the same-magnification intermediate image of the object plane reduces the occurrence of aberration in the first imaging optical system. As a result, the magnification of the entire catadioptric optical system is borne solely by the second imaging optical system, and the burden of the magnification on the second imaging optical system becomes too heavy.
In particular, when a large numerical aperture NA is required for the optical system, the size and complexity of the second imaging optical system cannot be avoided. Further, since the intermediate image is formed near the object plane, a sufficient working distance (working distance) cannot be secured on the object side unless an optical path deflecting member such as a polarizing beam splitter is used.

The present invention has been made in view of the above problems, and has a small catadioptric optical system having a sufficiently large numerical aperture and working distance on the image side and having a resolution of a quarter micron unit in the ultraviolet wavelength region. The purpose is to provide.

[0008]

According to the present invention, there is provided a first image forming optical system for forming an intermediate image of an object surface based on light from the object surface.
A second imaging optical system S2 for forming a reduced image of the object surface based on light from the intermediate image, and the first imaging optical system arranged near a position where the intermediate image is formed System S
A first optical path deflecting member M1 for deflecting the light passing through the first optical path toward the second imaging optical system S2, wherein the first imaging optical system S1 has a concave reflecting mirror CM, After the light from the surface is reflected by the concave reflecting mirror CM, the first
The intermediate image is formed in the optical path of the imaging optical system S1, and the first optical path deflecting member M1 has a plane reflecting mirror disposed in the optical path of the first imaging optical system S1; The imaging magnification of the imaging optical system S1 is β1, and 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 plane. Is L1, and the axial distance between the object plane and the concave reflecting mirror CM is LM. The condition of 0.75 <| β1 | <0.95 0.13 <L1 / LM <0.35 Catadioptric optical system characterized by satisfying the following.

According to a preferred aspect of the present invention, the first
The imaging optical system S1 includes, in order from the object side, a first lens group G1.
, A second lens group G2, and the concave reflecting mirror CM, and light from the object surface is reflected by the concave reflecting mirror CM via the first lens group G1 and the second lens group G2. After that, the intermediate image is formed in the optical path between the first lens group G1 and the second lens group G2. In this case, the second lens group G2 preferably includes at least two refractive elements having different negative refractive powers and at least two refractive elements having different positive refractive powers. It is preferable that the first lens group G1 includes at least three refractive elements having different refractive powers.

According to a preferred aspect of the present invention, the second imaging optical system S2 includes, in order from the object side, a third lens group G3 having a positive refracting power as a whole, and a third lens group G3. Optical path deflecting member M for deflecting light passing through
2 and a fourth lens group G4 having a positive refractive power as a whole
And the light from the intermediate image is transmitted through the third lens group G
3. A reduced image of the object plane is formed via the second optical path deflecting member M2 and the fourth lens group G4. Further, it is preferable that the refractive element constituting the catadioptric optical system is formed of at least one of optical materials of quartz and fluorite. Further, the second lens group G
2 has at least one positive lens made of fluorite, the total refractive power of the positive lens made of fluorite in the second lens group G2 is φc, and the refractive power of the concave reflecting mirror CM is φm.
In this case, it is preferable to satisfy the following condition: 0.5 <| φc / φm | <1.6.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, since the first imaging optical system S1 has a reduced imaging magnification, the burden of refractive power on the second imaging optical system S2 is reduced. As a result, the numerical aperture NA on the image side of the optical system can be increased, and the size and complexity of the second imaging optical system S2 can be avoided. In other words, the catadioptric optical system of the present invention has a resolution of a quarter-micron unit in the ultraviolet wavelength region, despite being a small optical system having a sufficiently large numerical aperture on the image side.

Hereinafter, the conditional expressions of the present invention will be described. In the present invention, the following conditional expressions (1) and (2) are satisfied. 0.75 <| β1 | <0.95 (1) 0.13 <L1 / LM <0.35 (2) where β1: the imaging magnification of the first imaging optical system S1 L1: the first imaging Optical axis of optical system S1 and second imaging optical system S2
Axial distance between the intersection with the optical axis of the object and the object plane (geometric distance along the optical axis) LM: On-axis distance between the object plane and the concave reflecting mirror CM

Conditional expression (1) defines an appropriate range for the imaging magnification of the first imaging optical system S1. When the value goes below the lower limit of conditional expression (1), the numerical aperture NA on the intermediate image side becomes too large, so that it becomes difficult to deflect the optical path by the first optical path deflecting member M1. On the other hand, when the value exceeds the upper limit value of the conditional expression (1), the imaging magnification β1 of the first imaging optical system S1 approaches unity, and the burden of the refracting power on the second imaging optical system S2 increases. Therefore, the numerical aperture NA on the image side of the optical system cannot be increased, and the size and complexity of the second imaging optical system S2 cannot be avoided. It is more preferable to set the lower limit of conditional expression (1) to 0.8 and the upper limit to 0.9.

Conditional expression (2) defines an appropriate positional relationship between the second imaging optical system S2 and the object plane. If the lower limit of conditional expression (2) is not reached, a sufficient working distance cannot be secured on the image side. as a result,
It becomes impossible to apply the catadioptric optical system of the present invention to a step-and-scan projection exposure apparatus. On the other hand, when the value exceeds the upper limit of conditional expression (2), it becomes difficult to satisfactorily correct coma and distortion. It is more preferable to set the lower limit of conditional expression (2) to 0.19 and the upper limit to 0.3.

The first imaging optical system S1 has, in order from the object side, a first lens group G1, a second lens group G2, and a concave reflecting mirror CM. After being reflected by the concave reflecting mirror CM via the first lens group G1 and the second lens group G2, the first lens group G1 and the second lens group G2
It is preferable to form an intermediate image in the optical path between the intermediate image and the intermediate image. In this case, it is easy to perform the optical path deflection by disposing the first optical path deflecting member M1 near the position where the intermediate image is formed, and it is also possible to avoid an increase in the size of the optical system.

The second lens group G2 has at least two lenses.
It is preferable to have two refractive elements having different negative refractive powers and at least two refractive elements having different positive refractive powers. Refractive elements such as negative lenses
Correction of coma, spherical aberration, curvature of field and the like is indispensable. On the other hand, a refracting element such as a positive lens is required to secure a large numerical aperture NA and a large exposure area without increasing the size of the optical system. Furthermore, in order to compensate the aberration of the second imaging optical system S2 and reduce the burden of aberration correction on the second imaging optical system S2, at least two negative lenses having different negative refracting powers are provided. And two positive lenses having different negative refractive powers.

The first lens group G1 has at least three lenses.
It is preferred to have two refractive elements having different refractive powers. Recently, as the resolution of an optical system is required to be improved, strict specifications (specs) are also required for correction of distortion and correction of field curvature. In order to achieve such strict specifications, it is necessary to adjust the aberration of the optical system at the time of manufacturing. Generally, it is effective to use a lens arranged near an object plane as an aberration adjusting lens of an optical system. In particular, in the present invention, since the light from the object plane reciprocates in the optical path in the second lens group G2,
It is not appropriate to use the second lens group G2 as a lens for aberration adjustment.

Therefore, the first lens group G1 is composed of at least three refracting elements having different refractive powers, and the first lens group G1 is used as an aberration adjusting lens. Can be adjusted. Further, by configuring the first lens group G1 with at least three refractive elements having different refractive powers, it is possible to secure a large working distance on the object side, and a step-and-scan type projection exposure apparatus is used. The catadioptric optical system according to the present invention can be applied to the above.

The second imaging optical system S2 includes, in order from the object side, a third lens group G3 having a positive refractive power, a second optical path deflecting member M2, and a fourth lens group G4 having a positive refractive power. Then, light from the intermediate image is transmitted to the third lens group G3 and the second optical path deflecting member M.
It is preferable to form a reduced image of the object plane via the second and fourth lens groups G4. Here, the third lens group G3
Plays the role of a field lens. The second optical path deflecting member M2 plays a role of keeping the object plane and the image plane parallel by cooperation with the first optical path deflecting member M1. Further, the fourth lens group G4 plays an important role mainly for correcting spherical aberration and coma aberration and for securing a large numerical aperture NA on the image side of the optical system.

The so-called coherence factor (σ value) can be adjusted by providing a variable stop (an aperture stop having a variable opening diameter) in the optical path of the fourth lens group G4. For example, Japanese Patent Publication No. Sho 62-50811 proposes a phase shift method for shifting the phase of a predetermined portion in a mask pattern from the phase of another portion as a method for increasing the depth of focus and improving the resolving power. In the present invention, since the coherence factor (σ value) can be adjusted, there is an advantage that the effect of the phase shift method can be further improved.

Further, it is preferable that the refractive element constituting the catadioptric optical system of the present invention is formed of at least one of an optical material of quartz and fluorite. That is, the lens constituting the optical system may be made of either quartz or fluorite, or may be made of quartz and fluorite, so that light in the ultraviolet wavelength range of 300 nm or less can be used as illumination light. it can.

In the present invention, the second lens group G
2 has at least one positive lens made of fluorite, and preferably satisfies the following conditional expression (3). 0.5 <| φc / φm | <1.6 (3) where φc is the total refractive power of the positive lens made of fluorite in the second lens group G2 φm is the refractive power of the concave reflecting mirror CM

Since the second lens group G2 has at least one positive lens made of fluorite, the concave reflecting mirror CM
It is also possible to correct chromatic aberration of a light beam incident on the optical system and to satisfactorily correct chromatic aberration of the entire optical system. Conditional expression (3) defines an appropriate range for the ratio of the total refractive power of the positive lens made of fluorite in the second lens group G2 to the refractive power of the concave reflecting mirror CM. If the upper limit and the lower limit of the conditional expression (3) are not satisfied, it becomes difficult to satisfactorily correct odd-order chromatic aberration with respect to the image height.

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The catadioptric optical system according to each embodiment of the present invention includes a first imaging optical system S1 for forming an intermediate image of the object plane based on light from the object plane, and an object based on light from the intermediate image. A second imaging optical system S2 for forming a reduced image of the surface, and a first imaging optical system S2 arranged near a position where an intermediate image is formed.
A first optical path deflecting member M1 for deflecting the light passing through the imaging optical system S1 toward the second imaging optical system S2.

The first optical path deflecting member M1 has a plane reflecting mirror disposed in the optical path of the first imaging optical system S1.
Further, the first imaging optical system S1 includes, in order from the object side, a first lens group G1, a second lens group G2, and a concave reflecting mirror CM. The light from the object surface is transmitted to the first lens group G
After being reflected by the concave reflecting mirror CM via the first and second lens groups G2, an intermediate image is formed in the optical path between the first lens group G1 and the second lens group G2. Further, the second imaging optical system S2 includes, in order from the object side, a third lens group G3 having a positive refractive power, a second optical path deflecting member M2, and a fourth lens group G4 having a positive refractive power. And the light from the intermediate image is the third
A reduced image of the object plane is formed via the lens group G3, the second optical path deflecting member M2, and the fourth lens group G4.

[First Embodiment] FIG. 1 is a diagram schematically showing a lens configuration of a catadioptric optical system according to a first embodiment of the present invention. In FIG. 1, the first lens group G1 of the first imaging optical system S1 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconvex lens, a biconcave lens, and a positive lens having a convex surface facing the object side. It is composed of a meniscus lens. Also, the second lens group G2 of the first imaging optical system S1
Are, in order from the object side, a biconvex lens, a negative meniscus lens with a concave surface facing the object side, a biconvex lens, a negative meniscus lens with a convex surface facing the object side, a biconcave lens, a biconvex lens, and a positive meniscus with a convex surface facing the object side Lens, biconvex lens,
It comprises a negative meniscus lens having a concave surface facing the object side, a biconcave lens, and a concave reflecting mirror CM. In addition,
In the optical path between the first lens group G1 and the second lens group G2, it functions as a plane-parallel plate for the light from the first lens group G1, and is flat for the light from the second lens group G2. A first optical path deflecting member M1 functioning as a reflecting mirror is provided.

On the other hand, the third lens group G3 of the second imaging optical system S2 includes, in order from the object side, a biconvex lens and a negative meniscus lens having a convex surface facing the object side.
The fourth lens group G4 of the second imaging optical system S2 has, in order from the object side, a positive meniscus lens having a convex surface facing the object side, a biconvex lens, an aperture stop AS, a biconvex lens, and a convex surface facing the object side. It comprises a positive meniscus lens, a biconcave lens, a positive meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, and a biconvex lens. Note that the third lens group G3 and the fourth lens group G4
A second optical path deflecting member M2 formed of a plane reflecting mirror is provided in the optical path between the first optical path deflecting member and the second optical path deflecting member M2.

Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1), β is the reduction magnification of the entire optical system, NAi is the numerical aperture on the image side, and d0 is the object surface and the most object side surface of the optical system (the most object side surface of the first lens group G1). ) Respectively. The surface number indicates the order of the surfaces from the object side along the direction in which light rays travel from the object surface to the image surface, r indicates the radius of curvature of each surface, and d indicates the on-axis interval of each surface. . The sign of the radius of curvature r of each surface is positive when the convex surface faces the object side between the object surface and the concave reflecting mirror CM, and the first optical path deflecting member M
The case where the convex surface faces the first optical path deflecting member M1 (object side) between the first and second optical path deflecting members M2 is positive, and the convex surface on the image side between the second optical path deflecting member M2 and the image surface is positive. It is positive when turning. The sign of the surface distance d is negative in the optical path from the concave reflecting mirror CM to the first optical path deflecting member M1, is negative in the optical path from the second optical path deflecting member M2 to the image plane, and is negative in other optical paths. Positive. Further, in Table (1), n is a reference wavelength λ = 193.4 nm (A
It shows the refractive index with respect to the wavelength of the rF excimer laser. In the first embodiment, quartz (n = 1.
56019) and fluorite (n = 1.50138).

[0029]

Table 1 β = -0.25 NAi = 0.6 d0 = 49.998 Face number r dn 1 369.115 18.000 1.56019 2 245.893 0.500 3 227.674 33.705 1.50138 4 -373.082 18.803 5 -324.258 20.532 1.56019 6 332.817 1.674 7 340.581 20.389 1.56019 8 604.750 27.395 9 ∞ 35.000 1.56019 (First optical path deflecting member M1: Transmission surface) 10 ∞ 16.943 11 391.176 30.000 1.50138 12 -982.727 6.592 13 -417.793 20.000 1.56019 14 -1216.731 261.353 15 478.547 40.000 1.50138 16 -908.632 11.323 17 32 20.000 1.56019 18 208.331 48.917 19 -196.257 20.000 1.56019 20 1370.871 0.500 21 430.209 42.793 1.50138 22 -366.694 61.625 23 247.465 25.000 1.56019 24 286.274 68.753 25 508.228 40.000 1.56019 26 -930.828 27.931 27 -313.824 25.000 1.57 30 1335.454 32.821 31 -360.416 -32.821 (Concave reflector CM) 32 1335.454 -25.000 1.56019 33 -276.064 -19.454 34 -1017.267 -25.000 1.56019 35 -313.824 -27.931 36 -930.828 -40.000 1.56019 37 508.228 -68.7 53 38 286.274 -25.000 1.56019 39 247.465 -61.625 40 -366.694 -42.793 1.50138 41 430.209 -0.500 42 1370.871 -20.000 1.56019 43 -196.257 -48.917 44 208.331 -20.000 1.56019 45 325.213 -11.323 46 -908.632 -40.47 1.50138 47 478.5 -1216.731 -20.000 1.56019 49 -417.793 -6.592 50 -982.727 -30.000 1.50138 51 391.176 -1.943 52 ∞ 236.637 (First optical path deflecting member M1: Reflective surface) 53 471.443 36.090 1.50138 54 -1089.261 3.979 55 306.858 20.000 1.56019 56 247.195 150.000 57 ∞ -162.806 (second optical path deflection member M2) 58 -812.165 -25.000 1.56019 59 -2628.418 -290.508 60 -1094.809 -30.000 1.56019 61 1598.936 -30.114 62 ∞ -81.437 (Aperture stop AS) 63 -266.544 -45.218 1.50138 64 2115.935- 0.550 65 -213.134 -30.096 1.56019 66 -642.205 -15.142 67 1328.716 -30.000 1.56019 68 -654.044 -1.236 69 -210.004 -45.167 1.56019 70 -304.557 -19.703 71 -166.497 -45.000 1.56019 72 -72.336 -6.218 73 -71.786 -66.262 1.56019 74 2042.086 -17.000 (Conditional value) β1 = −0. 77207 L1 = 241 LM = 1070 φc = 0.005850 φm = 0.005549 (1) | β1 | = 0.877207 (2) L1 / LM = 0.225 (3) | φc / φm | = 1.054228

FIG. 2 is a lateral aberration diagram of the first embodiment.
(A) is a lateral aberration diagram at the maximum image height Y = 18.6, and (b) is a lateral aberration diagram at the intermediate image height Y = 5.0. In each lateral aberration diagram, the solid line represents the reference wavelength λ = 1.
The aberration curve with respect to 93.4 nm is shown.
The aberration curve for 193.0 nm is shown.
The aberration curve for 93.2 nm is shown,
The aberration curve for 193.6 nm is shown.
9A and 9B respectively show aberration curves for 93.8 nm.
Referring to the lateral aberration diagrams in FIG. 2, it can be seen that in the first example, aberrations are favorably corrected even though a large numerical aperture and a large working distance are secured on the image side of the optical system. In particular, it can be seen that chromatic aberration is excellently corrected at 193.4 ± 0.4 nm, and that excellent image forming performance is obtained.

[Second Embodiment] FIG. 3 is a diagram schematically showing a lens configuration of a catadioptric optical system according to a second embodiment of the present invention. In FIG. 3, the first lens group G1 of the first imaging optical system S1 includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconvex lens, a biconcave lens, and a positive lens having a convex surface facing the object side. It is composed of a meniscus lens. Also, the second lens group G2 of the first imaging optical system S1
Are, in order from the object side, a biconvex lens, a negative meniscus lens with a concave surface facing the object side, a biconvex lens, a negative meniscus lens with a convex surface facing the object side, a biconcave lens, a biconvex lens, and a positive meniscus with a convex surface facing the object side Lens, biconvex lens,
Negative meniscus lens with concave surface facing object side, negative meniscus lens with concave surface facing object side, and concave reflector CM
It is composed of In the optical path between the first lens group G1 and the second lens group G2, the second lens group G1 functions as a plane parallel plate to the light from the first lens group G1.
A first optical path deflecting member M1 functioning as a plane reflecting mirror with respect to the light from the light source 2 is provided.

On the other hand, the third lens group G3 of the second imaging optical system S2 includes, in order from the object side, a biconvex lens and a negative meniscus lens having a convex surface facing the object side.
The fourth lens group G4 of the second imaging optical system S2 includes, in order from the object side, a positive meniscus lens having a convex surface facing the object side, a positive meniscus lens having a concave surface facing the object side, an aperture stop AS, and a biconvex lens. A positive meniscus lens having a convex surface facing the object side, a biconcave lens, a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, and a biconvex lens. The third
In the optical path between the lens group G3 and the fourth lens group G4,
A second optical path deflecting member M2 composed of a plane reflecting mirror is provided.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), β is the reduction magnification of the entire optical system, NAi is the numerical aperture on the image side, and d0 is the object surface and the most object side surface of the optical system (the most object side surface of the first lens group G1). ) Respectively. The surface number indicates the order of the surfaces from the object side along the direction in which light rays travel from the object surface to the image surface, r indicates the radius of curvature of each surface, and d indicates the on-axis interval of each surface. . The sign of the radius of curvature r of each surface is positive when the convex surface faces the object side between the object surface and the concave reflecting mirror CM, and the first optical path deflecting member M
The case where the convex surface faces the first optical path deflecting member M1 (object side) between the first and second optical path deflecting members M2 is positive, and the convex surface on the image side between the second optical path deflecting member M2 and the image surface is positive. It is positive when turning. The sign of the surface distance d is negative in the optical path from the concave reflecting mirror CM to the first optical path deflecting member M1, is negative in the optical path from the second optical path deflecting member M2 to the image plane, and is negative in other optical paths. Positive. Further, in Table (2), n is a reference wavelength λ = 193.4 nm (A
It shows the refractive index with respect to the wavelength of the rF excimer laser. In the first embodiment, quartz (n = 1.
56019) and fluorite (n = 1.50138).

In the second embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis from the vertex is y, and the displacement (sag amount) in the optical axis direction from the vertex at the height y is S (y). When the reference radius of curvature (the radius of curvature of the vertex) is r, the cone coefficient is κ, and the n-th order aspherical surface coefficient is Cn, the following equation (a) is given.

[Number 1] ^{S (y) = (y 2} / r) / [1+ {1- (1 + κ) · y 2 / r 2} 1/2 ] ^{_{+ C 4 · y 4 + C}} 6 · y 6 + C 8 · y 8 ^{_{+ C 10 · y 10 + C}} 12 · y 12 (a)

[0035]

Table 2 β = −0.25 NAi = 0.6 d0 = 45.000 Face number r dn 1 281.775 18.000 1.56019 2 195.859 1.598 3 196.715 40.418 1.50138 4 -480.361 14.536 5 -548.718 20.000 1.56019 6 204.428 5.448 7 203.274 20.000 1.56019 8 401.273 25.000 9 ∞ 35.000 1.56019 (1st optical path deflecting member M1: transmission surface) 10 ∞ 15.500 11 303.555 30.000 1.50138 12 -1740.057 5.924 13 -425.354 20.000 1.56019 14 -2761.815 171.793 15 300.937 40.000 1.50138 16 -2581.928 1.849 178.864 20.000 1.56019 18 177.975 57.224 19 -175.888 20.000 1.56019 20 764.840 0.500 21 342.881 36.406 1.50138 22 -329.279 48.341 23 270.936 25.000 1.56019 24 328.277 66.732 25 778.307 40.000 1.56019 26 -518.576 15.753 27 -223.579 25.000 1.560 30 -1514.955 17.542 31 -332.936 -17.542 (Concave reflector CM: aspheric surface) 32 -1514.955 -25.000 1.56019 33 -229.025 -42.435 34 -658.513 -25.000 1.56019 35 -223.579 -15.753 36 -518.576 -40.000 1.56019 37 77 8.307 -66.732 38 328.277 -25.000 1.56019 39 270.936 -48.341 40 -329.279 -36.406 1.50138 41 342.881 -0.500 42 764.840 -20.000 1.56019 43 -175.888 -57.224 44 177.975 -20.000 1.56019 45 288.864 -1.849 46 -2581.928 -40.000 1.138 47. 171.793 48 -2761.815 -20.000 1.56019 49 -425.354 -5.924 50 -1740.057 -30.000 1.50138 51 303.555 -0.500 52 ∞ 233.000 (First optical path deflecting member M1: Reflective surface) 53 415.207 31.117 1.50138 54 -631.341 0.500 55 306.049 20.000 1.56019 56 218.635 150.000 57 ∞ -165.240 (2nd optical path deflection member M2) 58 -711.482 -25.000 1.56019 59 -2123.013 -302.795 60 3482.765 -30.000 1.56019 61 654.764 -15.000 62 ∞ -59.904 (Aperture stop AS) 63 -230.331 -70.000 1.50138 (Non Spherical) 64 1603.607 -0.500 65 -204.918 -28.538 1.56019 66 -602.518 -14.615 67 1240.449 -30.000 1.56019 68 -510.567 -0.500 69 -308.492 -70.000 1.56019 70 -714.386 -0.500 71 -170.397 -45.000 1.56019 72 -62.983 -4.156 73 -63.147 -62.343 1.56019 74 766.887 -17.000 (Aspheric data Data) κ C ₄ C ₆ 31 faces ^{0.0000 0.815186 × 10 -9 0.106110 × 10} -13 C 8 C 10 C 12 0.216157 × 10 -18 -0.473987 × 10 -23 0.490366 × 10 -27 κ C 4 C 6 63 faces 0.0000 ^{0.371510 × 10 -8 0.507303 × 10 -13} C 8 C 10 C 12 0.416256 × 10 -18 0.261764 × 10 -22 -0.397276 × 10 -27 ( condition corresponding values) β1 = -0.854038 L1 = 240 LM = 950 φc = 0.006712 φm = 0.006006 (1) | β1 | = 0.54038 (2) L1 / LM = 0.253 (3) | φc / φm | = 1.117626

FIG. 4 is a lateral aberration diagram of the second embodiment.
(A) is a lateral aberration diagram at the maximum image height Y = 18.6, and (b) is a lateral aberration diagram at the intermediate image height Y = 5.0. In each lateral aberration diagram, the solid line represents the reference wavelength λ = 1.
The aberration curve with respect to 93.4 nm is shown.
The aberration curve for 193.0 nm is shown.
The aberration curve for 93.2 nm is shown,
The aberration curve for 193.6 nm is shown.
9A and 9B respectively show aberration curves for 93.8 nm.
Referring to the lateral aberration diagrams in FIG. 4, it can be seen that in the second embodiment, aberrations are favorably corrected even though a large numerical aperture and a large working distance are secured on the image side of the optical system. In particular, it can be seen that chromatic aberration is excellently corrected at 193.4 ± 0.4 nm, and that excellent image forming performance is obtained.

[0037]

As described above, according to the present invention, it is possible to realize a small catadioptric optical system having a sufficiently large numerical aperture and working distance on the image side and having a resolution of a quarter-micron unit in the ultraviolet wavelength region. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a lens configuration of a catadioptric optical system according to a first example of the present invention.

FIGS. 2A and 2B are lateral aberration diagrams of the first embodiment, wherein FIG. 2A is a lateral aberration diagram at a maximum image height Y = 18.6, and FIG. 2B is a lateral aberration diagram at an intermediate image height Y = 5.0. FIG.

FIG. 3 is a diagram schematically showing a lens configuration of a catadioptric optical system according to a second embodiment of the present invention.

4A and 4B are lateral aberration diagrams of the second embodiment, in which FIG. 4A is a lateral aberration diagram at a maximum image height Y = 18.6, and FIG. 4B is a lateral aberration diagram at an intermediate image height Y = 5.0. FIG.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group S1 first imaging optical system S2 second imaging optical system M1 first optical path deflecting member M2 second optical path deflecting member AS aperture stop CM Concave reflector

Claims (7)

[Claims] A first imaging optical system for forming an intermediate image of the object surface based on light from the object surface; and a reduced image of the object surface based on light from the intermediate image. And a second imaging optical system S2 for deflecting light passing through the first imaging optical system S1 near the position where the intermediate image is formed toward the second imaging optical system S2. The first imaging optical system S1 has a concave reflecting mirror CM, and the light from the object surface is reflected by the concave reflecting mirror CM, The intermediate image is formed in the optical path of one imaging optical system S1, and the first optical path deflecting member M1 is provided in the first imaging optical system S1.
, An imaging magnification of the first imaging optical system S1 is β1, and an optical axis of the first imaging optical system S1 and the second imaging optical system S2 are provided. The on-axis distance between the intersection with the optical axis and the object plane is L1,
The on-axis distance between the object plane and the concave reflecting mirror CM is L
A catadioptric system characterized by satisfying the following condition: M: 0.75 <| β1 | <0.95 0.13 <L1 / LM <0.35 2. The first imaging optical system S1 includes a first lens group G1, a second lens group G2, and the concave reflecting mirror CM in order from the object side, and the light from the object plane is provided. Is reflected by the concave reflecting mirror CM through the first lens group G1 and the second lens group G2, and then is placed in an optical path between the first lens group G1 and the second lens group G2. The catadioptric optical system according to claim 1, wherein an intermediate image is formed. 3. The second lens group G2 has at least two lenses.
3. The catadioptric optical system according to claim 2, comprising: two refractive elements having different negative refractive powers; and at least two refractive elements having different positive refractive powers. 4. The first lens group G1 has at least three lenses.
4. The catadioptric optical system according to claim 2, comprising two refractive elements having different refractive powers. 5. The second imaging optical system S2 includes a third lens group G3 having a positive refractive power as a whole in order from the object side.
A second optical path deflecting member M2 for deflecting the light passing through the third lens group G3, and a fourth lens group G4 having a positive refractive power as a whole. The reduced image of the object plane is formed via the third lens group G3, the second optical path deflecting member M2, and the fourth lens group G4. The catadioptric optical system according to the above item. 6. The refracting element constituting the catadioptric optical system is made of at least one of an optical material of quartz and fluorite.
The catadioptric optical system according to any one of the above. 7. The second lens group G2 has at least one positive lens made of fluorite, the sum of refractive power of the positive lenses made of fluorite in the second lens group G2 is φc, and the concave surface is The refractive power of the reflector CM is φ
7. The catadioptric optical system according to claim 2, wherein, when m is satisfied, the following condition is satisfied: 0.5 <| φc / φm | <1.6.