WO2003001271A1

WO2003001271A1 - Optical system and exposure system provided with the optical system

Info

Publication number: WO2003001271A1
Application number: PCT/JP2002/006131
Authority: WO
Inventors: Naomasa Shiraishi; Yasuhiro Omura
Original assignee: Nikon Corporation
Priority date: 2001-06-20
Filing date: 2002-06-19
Publication date: 2003-01-03
Also published as: TW558749B; JPWO2003001271A1

Abstract

An optical system capable of ensuring a good optical performance without substantially being affected by double refraction even when a double-refractive crystal material such as fluorite is used. The system comprises a first lens group (105, 106) composed of a plurality of crystal lenses each having an optical axis (AX100) agreeing with a crystal axis [111], and a second lens group (109, 110) composed of a plurality of crystal lenses each having the optical axis agreeing with a crystal axis [100]. The first lens group has a first A lens group and a first B lens group that are in a positional relation in which one is relatively rotated from the other through a first angle, and the second lens group has a second A lens group and a second B lens group that are in a positional relation in which one is relatively rotated from the other through a second angle.

Description

Description: Optical system and exposure apparatus provided with the optical system

Technical field

The present invention relates to an optical system and an exposure apparatus having the optical system, and more particularly to a projection optical system suitable for an exposure apparatus used when a microdepth such as a semiconductor element or a liquid crystal display element is manufactured by a photolithography process. It is. Background art

When forming micropatterns of electronic devices (microdevices) such as semiconductor integrated circuits and liquid crystal displays, the pattern of the photomask (also called a reticle) drawn by enlarging the pattern to be formed by about 4 to 5 times is projected. A method of reducing and projecting on a photosensitive substrate (substrate to be exposed) such as a wafer using an exposure apparatus is used. In this type of projection exposure apparatus, the exposure wavelength keeps shifting toward shorter wavelengths in order to cope with miniaturization of semiconductor integrated circuits.

At present, the exposure wavelength of the KrF excimer laser is 248 nm, but the shorter wavelength of the ArF excimer laser is 193 nm. Furthermore, the A r ₂ laser having a wavelength of 1 5 7 nm of F _2, single The one or wavelength 1 2 6 nm, the projection exposure equipment that uses the light source for supplying light in a wavelength band so-called vacuum ultraviolet region Suggestions have been made. In addition, since high resolution can be achieved by increasing the numerical aperture (NA) of the projection optical system, not only development of a shorter exposure wavelength but also development of a projection optical system with a larger numerical aperture Has also been made.

Optical materials (lens materials) with good transmittance and uniformity for exposure light in the ultraviolet region having such a short wavelength are limited. Synthetic silica glass can be used as a lens material in a projection optical system that uses an ArF excimer laser as a light source, but chromatic aberration cannot be sufficiently corrected with one type of lens material. For this purpose, calcium fluoride crystals (fluorite) are used. Meanwhile, projecting as a light source an F ₂ laser In shadow optics, the usable lens materials are effectively limited to calcium fluoride crystals (fluorite).

Recently, it has been reported that birefringence occurs even in such cubic calcium fluoride crystals (fluorite) for ultraviolet rays having such a short wavelength. In an ultra-high-precision optical system such as a projection optical system used in the manufacture of electronic devices, the aberration caused by the birefringence of the lens material is fatal, and the effect of the birefringence is substantially avoided. It is indispensable to adopt the lens configuration and lens design that have been adopted. Disclosure of the invention

The present invention has been made in view of the above-described problems. For example, even when a birefringent crystal material such as fluorite is used, good optical performance is obtained without being substantially affected by birefringence. It is an object of the present invention to provide an optical system that can be secured and an exposure apparatus including the optical system.

In addition, the present invention provides a microphone port that can manufacture a high-performance micro device according to a high-resolution exposure technique using an exposure apparatus equipped with an optical system having good optical performance using a crystalline material. It is intended to provide a device manufacturing method.

In order to solve the above problems, according to a first aspect of the present invention, an optical system including a plurality of optical elements formed of crystals belonging to a cubic system,

A first element group including a plurality of optical elements set so that an optical axis of the optical system and a crystal axis [111] or a crystal axis optically equivalent to the crystal axis; A second element group composed of a plurality of optical elements set so that the optical axis and the crystal axis [100] or the crystal axis and the optical axis equivalent to the crystal axis substantially coincide with each other; The first element group includes a first A element group and a first B element group having a positional relationship relatively rotated by a first angle about the optical axis,

The second element group includes a second A element group and a second B element group having a positional relationship relatively rotated by a second angle about the optical axis,

An optical axis of the light flux forming an angle within a predetermined range with respect to the optical axis in the first A element group; The optical path length L 1 A in the element is substantially equal to the optical path length L 1 B in the optical element in the first B element group,

The optical path length L 2 A in the optical element of the second A element group and the optical path length L 2 B of the optical element in the second B element group of the light beam forming the angle in the predetermined range with respect to the optical axis are different. Almost equal,

The optical path length LI (= L1A + L1B) in the optical element in the first element group of the light beam forming the angle in the predetermined range with respect to the optical axis and the optical path in the optical element in the second element group An optical system is provided, wherein an optical path length L 2 (= L 2 A + L 2 B) is set according to a predetermined magnification.

According to a preferred aspect of the first invention, the optical path length L1 in the optical element in the first element group is set to about 1.5 times the optical path length L2 in the optical element in the second element group. I have. In this case, the difference between 1.5 times the optical path length L2 in the optical element in the second element group and the optical path length L1 in the optical element in the first element group is the wavelength of the light beam as λ ( when a nm), it is preferably set within the soil ^{^{1. 0 X 10_ 6 Χ λ 3}} (cm).

According to a preferred aspect of the first invention, the difference between the optical path length L 1 A in the optical element in the first A element group and the optical path length L 1 B in the optical element in the first B element group is when the wavelength of the light beam and lambda (nm), is set to ^{± 0. 5 Χ 1 0_ 6} Χλ 3 (cm) within. Further, the difference between the optical path length L 2 A in the optical element in the second A element group and the optical path length L 2 B in the optical element in the second B element group is such that the wavelength of the light flux is λ (nm). when a, ± 0. it is preferably set within ^{^{5X 10- 6 Χλ 3 (cm)}} . Further, the angle in the predetermined range is larger than an angle corresponding to 0.6 times the image side numerical aperture of the optical system and smaller than an angle corresponding to 0.9 times the image side numerical aperture. preferable.

Further, according to a preferred aspect of the first invention, the first A element group and the first B element group are arranged close to each other along the optical axis, and the second A element group and the first The 2B element group is arranged close to each other along the optical axis. Further, the first element group and the second element group are arranged close to each other along the optical axis. Is preferred. Further, at least one of the first A element group, the first B element group, the second A element group, and the second B element group is close to each other along the optical axis. It is preferable that it is constituted by a plurality of optical elements arranged. Further, it is preferable that a plurality of sets of the first element group and the second element group are provided.

According to a second aspect of the present invention, in an optical system including a plurality of optical elements formed of crystals belonging to a cubic system,

A third element group composed of a plurality of optical elements set so that the optical axis of the optical system and the crystal axis [110] or the crystal axis that is optically equivalent to the crystal axis substantially coincide with each other; With a fourth element group,

The third element group includes a third A element group and a third B element group having a positional relationship relatively rotated by a third angle about the optical axis,

The fourth element group includes a fourth A element group and a fourth B element group having a positional relationship relatively rotated by a fourth angle about the optical axis,

The third element group and the fourth element group have a positional relationship of being rotated by a fifth angle about the optical axis, and

The optical path length L 3 A in the optical element of the third A element group and the optical path length L 3 B of the optical element in the third B element group of the light beam forming an angle within a predetermined range with respect to the optical axis are substantially equal to each other. Equal,

An optical path length L 4 A in the optical element of the fourth A element group and a light path length L 4 B of the optical element in the fourth B element group of the light beam forming the angle within the predetermined range with respect to the optical axis are different. Almost equal,

The optical path length L 3 (= L 3 A + L 3 B) in the optical element in the third element group of the light beam forming the angle in the predetermined range with respect to the optical axis and the optical element in the fourth element group An optical path length L 4 (= L 4 A + L 4 B) is set according to a predetermined magnification.

According to a preferred aspect of the second invention, the optical path length 3 in the optical element in the third element group is set to be substantially equal to the optical path length L4 in the optical element in the fourth element group. Have been. In this case, the difference between the optical path length L3 in the optical element in the third element group and the optical path length L4 in the optical element in the fourth element group is when the wavelength of the light beam is λ (ηm). it is preferably set within ^{^{± 1. 0 X 10- 6 Χλ 3}} (cm).

According to a preferred aspect of the second invention, the difference between the optical path length L 3 A in the optical element in the third A element group and the optical path length L 3 B in the optical element in the third B element group is when the wavelength of the light beam with λ (nm), ± 0. is set within ^{^{5X 10- 6 Χλ 3 (cm)}} . Further, the difference between the optical path length L 4 A in the optical element in the fourth A element group and the optical path length L 4 B in the optical element in the fourth B element group is such that the wavelength of the light flux is λ (nm). when a, ± 0. it is preferable to set within ^{^{5 X 10- 6 Χλ 3 (cm}} ).

Further, according to a preferred aspect of the second invention, the optical device further includes a fifth element group including a plurality of optical elements set so that the optical axis and the crystal axis [100] substantially coincide with each other. The five element group includes a fifth A element group and a fifth B element group having a positional relationship relatively rotated by a sixth angle about the optical axis, and the predetermined element is defined with respect to the optical axis. The optical path length L5A in the optical element of the fifth A element group of the light flux forming the angle of the range is substantially equal to the optical path length L5B in the optical element of the fifth B element group, and On the other hand, the optical path length L 3 (= L 3 A + L 3 B) in the optical element of the third element group and the optical path length L 4 of the optical element in the fourth element group of the light beam forming the predetermined range of angles (= L4A + L4B) and the total optical path length L 34 (= L 3 + L 4) and the optical path length L 5 (= L 5A + L 5B) in the optical element in the fifth element group are predetermined.It is set according to the magnification.

In this case, the total optical path length L34 in the optical element in the third element group and the fourth element group is set to be about four times the optical path length L5 in the optical element in the fifth element group. Is preferred. In this case, the difference between about four times the optical path length L5 in the optical element in the fifth element group and the total optical path length L34 in the optical element in the third element group and the fourth element group is different. when the wavelength of the light beam and lambda (nm), it is preferably set within the soil ^{^{2. 7 X 10- 6 Χλ 3 (}} cm). further, The difference between the optical path length L5A in the optical element in the fifth A element group and the optical path length L5B in the optical element in the fifth B element group is such that the wavelength of the light flux is λ (nm). when it is preferably set within ± 0. 5 X 1 0 one ^{6 Χ λ} ³ (cm).

According to a preferred aspect of the second invention, the angle in the predetermined range is larger than an angle corresponding to 0.6 times the image-side numerical aperture of the optical system and 0.9 times the image-side numerical aperture. Smaller than the angle corresponding to. Further, the third A element group and the third B element group are arranged close to each other along the optical axis, and the fourth A element group and the fourth B element group are arranged along the optical axis. It is preferable that they are arranged close to each other. Further, it is preferable that the third element group and the fourth element group are arranged close to each other along the optical axis. Further, at least one of the third A element group, the third B element group, the fourth A element group, and the fourth B element group is arranged close to each other along the optical axis. It is preferable that the optical element be composed of a plurality of optical elements. It is preferable that a plurality of sets of the third element group and the fourth element group are provided. Further, it is preferable that the fifth A element group and the fifth B element group are arranged close to each other along the optical axis.

According to a third aspect of the present invention, in an optical system including a plurality of optical elements formed of crystals belonging to a cubic system,

A sixth element group composed of a plurality of optical elements each set so that the optical axis of the optical system and the crystal axis [110] or the crystal axis that is optically equivalent to the crystal axis are substantially the same. A seventh element group, an eighth element group, and a ninth element group,

The seventh element group has a positional relationship rotated by a seventh angle in a predetermined direction about the optical axis with respect to the sixth element group,

The eighth element group has a positional relationship rotated by the seventh angle in the predetermined direction about the optical axis with respect to the seventh element group,

The ninth element group has a positional relationship rotated by the seventh angle in the predetermined direction about the optical axis with respect to the eighth element group,

An optical path length L6 of an optical element in the sixth element group of a light beam that forms an angle within a predetermined range with respect to the optical axis; and a light path length L6 that forms an angle within the predetermined range with respect to the optical axis. An optical path length L 7 in the optical element in the seven element group, an optical path length L 8 in the optical element in the eighth element group of a light beam forming an angle in the predetermined range with respect to the optical axis, and The optical path length L9 in the optical element in the ninth element group of the luminous flux forming the angle in the predetermined range is substantially equal to each other.

According to a preferred aspect of the third invention, an optical path length L 6 in the optical element in the sixth element group, an optical path length L 7 in the optical element in the seventh element group, and an optical element in the eighth element group When the difference between two optical path lengths arbitrarily selected from the medium optical path length L 8 and the optical path length L 9 in the optical element in the ninth element group is λ (η m), , ± 0.5 Χ 10_ ⁶ Χλ ³ (cm).

According to a preferred aspect of the third invention, the optical axis is constituted by a plurality of optical elements set so that the optical axis and the crystal axis [100] or the crystal axis which is optically equivalent to the crystal axis substantially coincide with each other. The tenth element group further includes a 10A element group and a 10B element group having a positional relationship relatively rotated by an eighth angle about the optical axis. The optical path length L 1 OA in the optical element of the first OA element group and the optical path length L 10 B of the optical element in the 10B element group of the light beam forming the angle in the predetermined range with respect to the optical axis. Is approximately equal to In this case, the difference between the optical path length L 1 OA in the optical element in the 10th A element group and the optical path length L 10 B in the optical element in the 10B element group makes the wavelength of the light flux λ (nm ) and the time, ± 0. it is preferable to set within ^{^{5 X 10- 6 Χλ 3 (cm}} ).

Further, according to a preferred aspect of the third invention, the optical path length L 6 in the optical element in the sixth element group, the optical path length L 7 in the optical element in the seventh element group, and the optical element in the eighth element group The total optical path length L 69 (= L 6 + L 7 + L 8 + L 9) of the medium optical path length L 8 and the optical path length L 9 in the optical element in the ninth element group, and in the tenth element group The optical path length L 10 (= L 10 A + L 10 B) in the optical element is set according to a predetermined magnification. In this case, the total optical path length L69 in the optical elements in the sixth to ninth element groups is set to be about four times the optical path length L10 in the optical elements in the tenth element group. Is preferred. In this case, the optical path length L10 in the optical element in the tenth element group is about four times as large as the sixth element group. Difference between the total Wako path length L 29 in the optical element in optimum the ninth element group, when the wavelength of the light beam with λ (nm), ± 2. 7 X 10- 6 Χλ 3 (cm) set within It is preferable that it is done. Furthermore, it is preferable that at least one of the sixth to ninth element groups and the tenth element group has a plurality of sets.

Further, according to a preferred aspect of the third invention, a first element group including a plurality of optical elements set so that an optical axis of the optical system and a crystal axis [111] substantially coincide with each other. Further comprising: a first 1A element group and a 1 1B element group having a positional relationship rotated relative to each other by a ninth angle about the optical axis. The optical path length L11A in the optical element of the first 1A element group and the optical path length L11 in the optical element of the 11B element group of the light beam forming the angle within the predetermined range with respect to the optical axis. B is almost equal. In this case, the difference between the optical path length L11A in the optical element in the first 1A element group and the optical path length L11B in the optical element in the first 1B element group is the wavelength of the light beam. when e and (nm), it is preferably set to ^{± 0. 5 X 10- 6 Χλ} 3 (cm) within. Further, it is preferable to have a plurality of sets of the first element group.

Further, according to a preferred aspect of the third invention, the total optical path length L 69 in the optical element in the sixth element group to the ninth element group is three times the optical path length in the optical element in the eleventh element group. The sum of L11 and eight times (= 3XL69 + 8XL11) is set to be about 12 times the optical path length L10 in the optical element in the tenth element group. In this case, the total optical path length L 69 (cm) in the optical element in the sixth element group to the ninth element group, the optical path length L 10 (cm) in the optical element in the tenth element group, When the wavelength of the luminous flux is λ (nm) between the optical path length L 11 (cm) in the optical element in the 1 element group, I 3 XL 69—12XL 10 + 8 XL 1 1 ≤ it is preferred to 8. 0 X 10- ⁶ Χ λ ³ conditions are satisfied. Preferably, the angle in the predetermined range is larger than an angle corresponding to 0.6 times the image-side numerical aperture of the optical system and smaller than an angle corresponding to 0.9 times the image-side numerical aperture. New

According to a preferred embodiment of the first to third inventions, the crystal is formed of calcium fluoride. It is a crystal. Preferably, the crystal is a barium fluoride crystal. Further, it is preferable to further include at least one concave reflecting mirror. Further, it is preferable that the optimally aberration correction with respect to A r F excimer one The one optimally or are aberration correction with respect to the oscillation wavelength, or F ₂ lasing wavelengths.

According to a fourth aspect of the present invention, there is provided an illumination system for illuminating a mask, and an optical system according to the first to third aspects for forming an image of a pattern formed on the mask on a photosensitive substrate. An exposure apparatus is provided.

In the fifth invention of the present invention, an exposure step of exposing the pattern of the mask to the photosensitive substrate using the exposure apparatus of the fourth invention, and a development step of developing the photosensitive substrate exposed in the exposure step The present invention provides a method for manufacturing a micro device characterized by including: BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view schematically showing a configuration of an exposure apparatus having a projection optical system according to each embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a projection optical system according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating the crystal axis orientation of fluorite.

FIG. 4A and FIG. 4B are diagrams illustrating an optical path in a fluorite lens in the projection optical system according to the first embodiment.

5A and 5B are diagrams illustrating birefringence when the optical axis of the fluorite lens is aligned with the crystal axis [111].

6A and 6B are diagrams illustrating birefringence when the optical axis of the fluorite lens is aligned with the crystal axis [100].

FIG. 7A and FIG. 7B are diagrams illustrating a configuration and an optical path of a first lens group and a second lens group in a projection optical system according to a modified example of the first embodiment.

FIG. 8 is a diagram schematically showing a configuration of a projection optical system according to a second embodiment of the present invention. FIGS. 9A and 9B are diagrams illustrating an optical path in a fluorite lens in the projection optical system according to the second embodiment.

FIGS. 10A to 10D are diagrams illustrating birefringence when the optical axis of the fluorite lens is aligned with the crystal axis [110].

FIG. 11 is a diagram schematically showing a configuration of a projection optical system according to a fourth embodiment of the present invention.

FIG. 12A and FIG. 12B are diagrams illustrating an optical path in a fluorite lens in a projection optical system according to the fourth embodiment.

FIG. 13 is a flowchart of a method for obtaining a semiconductor device as a micro device.

FIG. 14 is a flow chart of a method for obtaining a liquid crystal display element as a micro device. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a view schematically showing a configuration of an exposure apparatus having a projection optical system according to each embodiment of the present invention. In each embodiment of the present invention, the present invention is applied to a projection optical system mounted on an exposure apparatus. Referring to FIG. 1, an exposure apparatus according to each embodiment includes a light source 1 such as an ArF excimer laser or _two lasers. The light beam supplied from the light source 1 is guided to the illumination optical system 3 via the light transmission system 2. The illumination optical system 3 includes the bent mirrors 3a and 3b shown in the figure and an optical integrator (illustration equalizing element) not shown in the drawing, and illuminates the reticle (mask) 101 with almost uniform illuminance. .

Reticle 101 is held by reticle holder 4 by, for example, vacuum suction, and is configured to be movable by the action of reticle stage 5. The light beam transmitted through the reticle 101 is condensed through the projection optical system 300 to form a projected image of the pattern on the reticle 101 on a photosensitive substrate such as a semiconductor wafer 102. . The wafer 102 is also held by the wafer holder 7 by, for example, vacuum suction, and It is configured to be movable by the action of page 8. In this way, by performing the batch exposure while moving the wafer 102 in steps, the pattern projection image of the reticle 101 can be sequentially transferred to each exposure area of the wafer 102.

Further, by performing scanning exposure (scan exposure) while relatively moving the reticle 101 and the wafer 102 with respect to the projection optical system 300, the reticle 101 is placed on each exposure area of the wafer 102. Can be sequentially transferred. When exposing a circuit pattern to an actual electronic device, it is necessary to accurately align the pattern in the next step on the pattern formed in the previous step and expose it. An alignment microscope 10 for accurately detecting the position of the position detection mark on 102 is mounted.

When an F ₂ laser or an Ar F excimer laser (or an Ar ₂ laser with a wavelength of 126 ηm) is used as the light source 1, the light transmission system 2, the illumination optical system 3, and the projection optical system 300 The light path is purged with an inert gas such as, for example, nitrogen. In particular, when an F ₂ laser is used, the reticle 101, the reticle holder 4 and the reticle stage 5 are isolated from the outside atmosphere by the casing 6, and the internal space of the casing 6 is also inert gas. Has been purged. Similarly, the wafer 102, the wafer holder 7, and the wafer stage 8 are isolated from the outside atmosphere by a casing 9, and the internal space of the casing 9 is also purged with an inert gas. FIG. 2 is a diagram schematically showing a configuration of a projection optical system according to the first embodiment of the present invention. In the first embodiment, the present invention is applied to a refractive projection optical system in which aberration correction is optimized for an ArF laser having a wavelength λ (nm) of 193 nm. In the projection optical system 100 of the first embodiment (corresponding to the projection optical system 300 of FIG. 1), a light beam emitted from one point on the reticle 101 is moved along the optical axis AX100. Through a lens 103-110 arranged in one direction, to a point on a semiconductor wafer 102 as a photosensitive substrate. Thus, a projected image of the pattern drawn on the reticle 101 is formed on the wafer 102.

In the first embodiment, among the lenses 103 to 110, lenses 105, 106, 109 and 110 are formed of calcium fluoride crystals (fluorite), and the other lenses Is made of synthetic quartz glass. FIG. 3 is a diagram illustrating the crystal axis orientation of fluorite. Referring to FIG. 3, the crystal axis of fluorite is defined based on a cubic XYZ coordinate system. That is, a crystal axis [100] is defined along the + X axis, a crystal axis [010] is defined along the + Y axis, and a crystal axis [00 1] is defined along the + Z axis. In the XZ plane, the crystal axis [101] is at 45 ° to the crystal axis [100] and the crystal axis [001], and is the direction at 45 ° to the crystal axis [100] and the crystal axis [010] in the XY plane. The crystal axis [110] is defined in the YZ plane, and the crystal axis [011] is defined in a direction at 45 ° to the crystal axis [010] and the crystal axis [001] in the YZ plane. Furthermore, the crystal axis [1 1 1] is defined in a direction that forms an equal acute angle to the + X axis, the + Y axis, and the + Z axis. Although FIG. 3 shows only the crystal axes in the space defined by the + X axis, the + Y axis, and the + Z axis, the crystal axes are similarly defined in other spaces.

In fluorite, the crystal axis [1 1 1] shown by the solid line in Fig. 3 and the equivalent crystal axes [1 1 1 1], [1-1 1], and [11-1] not shown in the figure are duplicated. Refraction is almost zero (minimum). Similarly, the birefringence is almost zero (minimum) at the crystal axes [100], [010], and [001] indicated by the solid lines in Fig. 3. On the other hand, the crystal axis indicated by the broken line in FIG.

[1 10], [101], [01 1] and equivalent crystal axes not shown [― 11

For [0], [-101], [0 1-1], the birefringence is the largest.

As described above, birefringence (difference in refractive index between two light beams having orthogonal polarization planes) does not occur for light traveling in the directions of the crystal axes [100] and [11 1] of the fluorite crystal. Therefore, the crystal axis of the fluorite lens (optical element) [1 11] or [1 11

00] and the optical axis AX100 of the projection optical system 100 (and, consequently, the optical axis of the fluorite lens), the birefringence does not occur for the imaging light traveling parallel to the optical axis AX100. become. Conversely, the amount of birefringence is greatest for imaging light traveling along the crystal axis [01 1].

In the present invention, when it is necessary to strictly define the relative crystal axis orientation, for example, a plurality of crystal axes optically equivalent to the crystal axis [01 1] are represented by [01 1], [0- 1 1], [110], etc. are written (listed) by changing the code and array position. But However, if it is not necessary to define the relative crystallographic axis orientation strictly, the notation of the crystallographic axis [01 1] can be expressed as [01 1], [0—11], [1 1 0], etc. A plurality of optically equivalent crystal axes are collectively expressed.

By the way, to improve the resolution of the projection optical system 100, the image side NA (image side numerical aperture) which is the sine of the maximum incident angle 0100 (see FIG. 2) of the light beam on the wafer 102 is set to, for example, about 0.85. Need to be expanded. Therefore, it is impossible to set all the traveling directions of the light beams passing through the projection optical system 100 (and, consequently, the traveling directions of the light beams passing through the lenses 103 to 110) to be parallel to the optical axis AX100. FIG. 4A and FIG. 4B are diagrams illustrating an optical path in a fluorite lens in the projection optical system according to the first embodiment.

Focusing on the fluorite lenses 105, 106, 109, and 110, as shown in FIGS. 4A and 4B, a light beam incident on the wafer 102 at a maximum incident angle of 0100 (a light beam corresponding to the image-side NA). The optical paths (1056, 106 e, 109 e, 110 e) of the fluorite lenses 105, 106, 109, 110 for 100 e are not parallel to the optical axis AX100. Also, for a light beam 100m whose incident angle on the wafer 102 is about 60% to 90% of the maximum incident angle 0100 (that is, a light flux corresponding to about 60% to 90% of the image side NA), the fluorite lens 105, The optical paths of 106, 109 and 110 (105m, 106m, 109m, 110m) are not parallel to the optical axis AX100. As a result, these luminous fluxes that are not parallel to the crystal axis [1 11] will cause wavefront aberrations (hereinafter referred to as “birefringence effects”) caused by the birefringence of the fluorite crystal. .

5A and 5B are diagrams illustrating birefringence when the optical axis of the fluorite lens is aligned with the crystal axis [111]. Referring to FIG. 5A, the optical axis of fluorite lens 109 (and thus optical axis AX 100) is set to coincide with the crystal axis [111]. Here, the crystal axis [11 1] is directed upward (+ z direction) perpendicular to the plane of FIG. 5A, and each arrow indicates the direction of the other crystal axis. At this time, the crystal axes [1-110] and [1-10] are arranged in opposite directions in a plane perpendicular to the optical axis AX100. On the other hand, it can be obtained by rotating the directional vector, which forms about 35 ° with the optical axis AX 100 in the + z direction, about the optical axis AX 100. On the side surface of the cone, three crystal axes [01 1], [1 10], and [101] are arranged at an angular interval of 120 ° about the optical axis AX100 as the center of rotation.

As described above, these crystal axes [01 1], [1 10], and [10 1] are the crystal axes at which the amount of birefringence becomes maximum for light in the traveling direction. Here, the refractive index of light having a plane of polarization along the radial direction of the circle around the optical axis AX100 (hereinafter referred to as “R-polarized light”) and the refractive index of the circle around the optical axis AX100 The birefringence value is defined as the difference from the refractive index of light having a plane of polarization along the circumferential direction (hereinafter referred to as “6> polarized light”). Referring to FIG. 5A, in the fluorite lens 109 having the crystal axis [1 1 1] as the optical axis, three crystal axes [01 1], [1 10], [101] separated by an angle of 120 ° are provided. ], Rotational anisotropy occurs in which the birefringence value fluctuates at a period of 120 ° in the circumferential direction (rotational direction).

On the other hand, referring to FIG. 5B, the optical axis of the fluorite lens 110 (and thus the optical axis AX 100) is also set to coincide with the crystal axis [1 11]. However, the orientation of the crystal axis [—110] in the plane perpendicular to the optical axis AX100 is rotated by 0106 = 60 ° about the z axis compared to the case of the fluorite lens 109 in FIG. 5A. I have. In other words, the fluorite lens 109 in FIG. 5A and the fluorite lens 110 in FIG. 5B are both set so that the optical axis AX 100 and the crystal axis [11 1] coincide. It has a positional relationship that is relatively rotated by 60 ° about the optical axis AX100.

Referring to FIG. 5B, in the fluorite lens 110, the rotational anisotropy of the birefringence value still has a period of 120 °, but the position of the maximum value and the minimum value is the optical axis AX100. Will rotate by 60 ° around the center. Thus, by combining two fluorite lenses of equal thickness, both of which have the crystal axis [1 1 1] as the optical axis and whose crystal orientation is relatively rotated by 60 ° about the optical axis, The crystal lens has the same amount of birefringence (difference in refractive index between R-polarized light and zero-polarized light) at the azimuth centered on the optical axis because the rotational anisotropy of the 120 ° cycle of each crystal lens is canceled out. It has been clarified by the present inventors that a lens group is formed.

However, this configuration does not eliminate the influence of birefringence. As mentioned above, This is because the difference in the refractive index between the R-polarized light and the S-polarized light becomes almost uniform with respect to the azimuth around the optical axis, and the difference in the refractive index itself remains. According to the analysis of the present inventor, the crystal axis [111] is set as the optical axis and the other crystal axes (such as the crystal axis [-110] perpendicular to the optical axis AX111) are relatively 60 °. ° It has been found that the two rotating fluorite lenses of approximately equal thickness have a higher refractive index for R-polarized light (nR l 11) than a refractive index for 0-polarized light (Π 01 11 1). .

Therefore, in the first embodiment, in order to remove the residual birefringence almost uniformly with respect to the azimuth centered on the optical axis, a lens pair having the crystal axis [111] as the optical axis (109, 110) In addition, a pair of lenses (105, 106) whose optical axis is the crystal axis [100] is used. 6A and 6B are diagrams illustrating birefringence when the optical axis of the fluorite lens is aligned with the crystal axis [100]. Referring to FIG. 6A, the optical axis of the fluorite lens 105 (and thus the optical axis AX 100) is set to coincide with the crystal axis [100]. Here, the crystal axis [100] is oriented vertically upward (+ z direction) with respect to the plane of FIG. 6, and each arrow indicates the direction of the other crystal axis.

At this time, the crystal axes [001] and [00-1] are arranged in opposite directions in a plane perpendicular to the optical axis AX100. Also, the crystal axes [010] and [0_10] are also arranged in opposite directions so as to be orthogonal to the crystal axes [001] and [00-1]. On the other hand, on the side of the cone obtained by rotating a direction vector that forms an angle of about 45 ° with the optical axis AX 100 in the + z direction around the optical axis AX 100,

The four crystal axes [1 10], [10 1], [1-10], and [10-1] are arranged at 90 ° angular intervals about the optical axis AX 100 as the center of rotation.

As described above, these crystal axes [110], [101], [1-10], [10-1] are the crystal axes at which the amount of birefringence becomes maximum for light in the traveling direction. Referring to FIG. 6A, in the fluorite lens 105 having the crystal axis [100] as the optical axis, four crystal axes [1 10], [101], [1- According to [10] and [10-1], rotational anisotropy occurs in which the birefringence value fluctuates in the circumferential direction (rotation direction) with a period of 90 °. On the other hand, referring to FIG. 6B, the optical axis of fluorite lens 106 (and thus optical axis AX 100) is also set to coincide with the crystal axis [100]. However, the orientation of the crystal axis [001] in the plane perpendicular to the optical axis AX100 is rotated around the z-axis by 01 10 = 45 ° compared to the case of the fluorite lens 105 in Fig. 6A. You. In other words, the fluorite lens 105 in FIG. 6A and the fluorite lens 106 in FIG. 6B are both set so that the optical axis AX100 and the crystal axis [100] coincide, but the optical axis AX It has a relative position of 45 ° relative to 100.

Referring to FIG. 6B, in the fluorite lens 106, the rotational anisotropy of the birefringence value still has a period of 90 °, but the position of the maximum value and the minimum value is the position of the optical axis AX 1 It will rotate 45 ° around 00. Thus, by combining two fluorite lenses of equal thickness, both of which have the crystal axis [100] as the optical axis and whose crystal orientation is relatively rotated by 45 ° about the optical axis, A lens that has approximately the same amount of birefringence (difference in refractive index between R-polarized light and zero-polarized light) at an azimuth around the optical axis because the 90 ° -period rotational anisotropy of the crystal lens is canceled out. It was revealed by the present inventors that groups were formed.

Also in this case, the above configuration does not eliminate the influence of birefringence. As described above, the difference in the refractive index between the R-polarized light and the 0-polarized light is only approximately uniform with respect to the azimuth around the optical axis, and the difference in the refractive index itself remains. According to the analysis by the inventor of the present invention, two sheets whose crystal axis [100] is the optical axis and other crystal axes (such as the crystal axis [001] perpendicular to the optical axis AX100) are relatively rotated by 45 °. It was found that the refractive index (nRlOO) for R-polarized light was lower than that for に -polarized light (n01OO) for a fluorite lens with a thickness almost equal to the above.

That is, the birefringence code of the lens pair (109, 1 10) with the crystal axis [1 1 1] as the optical axis and the lens pair (105, 106) with the crystal axis [100] as the optical axis is Reverse. Therefore, by combining a lens pair (109, 110) with the crystal axis [111] as the optical axis and a lens pair (105, 106) with the crystal axis [100] as the optical axis, birefringence is obtained. Can be removed to some extent. When At this time, the birefringence of the lens pair (105, 106) with the crystal axis [100] as the optical axis, that is, (nR100-ηθ100), and the lens pair (111) with the crystal axis [11 1] as the optical axis The birefringence in (109, 110), that is, (nR lll—n S lll), is different from each other. Therefore, based on this birefringence, the optical path length of the lens pair (105, 106) with the crystal axis [100] as the optical axis and the lens pair (109, 109) with the crystal axis [1 1 1] as the optical axis By setting the optical path length to 1), the effect of birefringence can be almost completely eliminated. Specifically, the crystal axis

The birefringence of the lens pair (105, 106) with [100] as the optical axis, that is, (n R l O O-η θ Ι Ο Ο) is the lens pair with the crystal axis [1 1 1] as the optical axis ( The amount of birefringence at 109, 110), that is, (nR 1 1 1—n 6 1 1 1), is about 1.5 times larger. Therefore, the optical path length of the lens pair (109, 1 10) with the crystal axis [111] as the optical axis is approximately 1.1, which is about the optical path length of the lens pair (105, 106) with the crystal axis [100] as the optical axis. You can set it to 5 times. By doing so, it is possible to almost completely eliminate the effect of birefringence.

In the first embodiment, the above relationship is applied to the projection optical system 100 shown in FIG. That is, of the fluorite lenses 105, 106, 109, and 110, the thickness of the fluorite lenses 105 and 106 is set to be smaller than the thickness of the fluorite lenses 109 and 110. And the optical axes of the fluorite lenses 105 and 106 together

The optical axes of the fluorite lenses 109 and 110 are both aligned with the fluorite crystal axis [1 1 1]. The fluorite lenses 109 and 110 are set so that the crystal axis [-110] in the plane perpendicular to the optical axis has a positional relationship of being rotated by 60 ° relative to the optical axis as the center of rotation. The fluorite lenses 105 and 106 are set such that the crystal axis [001] in a plane perpendicular to the optical axis has a positional relationship rotated by 45 ° relative to the optical axis as the center of rotation.

Then, the luminous flux corresponding to 60 to 90% of the image side NA (maximum NA) (that is, the luminous flux forming an angle corresponding to 0.6 to 0.9 times the image side NA with respect to the optical axis AX100) 1 for 00m, set as the difference between the optical path length 106m of optical path length 105m and the fluorite lens 106 in the fluorite lens 105 is within ^{^{± 0. 5X 106 Χλ 3 (}} cm) are doing. Similarly, the difference between the optical path length 1 10 m of the optical path length 109m and the fluorite lens 110 in the fluorite lens 109 is ^{± 0. 5 Χ 10_ 6 Χλ} 3 (cm) is set up to be within. Furthermore, 1.5 times the total optical path length (105m + 106m) of the second lens group (105, 106) with the crystal axis [100] as the optical axis, and the crystal axis [111] as the optical axis Sagado 1. is set to be ^{^{0 X 10 _ 6 Χλ 3 (}} cm) within the sum of the optical path length of the first lens unit (109, 110) (109m + 1 1 Om) to.

Thus, the first lens group (109, 110) having the crystal axis [111] as the optical axis and the second lens group (105, 106) having the crystal axis [100] as the optical axis. Among them, the birefringence is made uniform with respect to the azimuth around the optical axis AX100. In addition, the first lens group (109, 110) with the crystal axis [111] as the optical axis and the second lens group (105, 106) with the crystal axis [100] as the optical axis are combined. However, the birefringence that has been made uniform with respect to the azimuth around the optical axis AX100 is offset each other, and as a result, the influence of the birefringence can be almost completely eliminated.

In the first embodiment, the first lens group (109, 110) having the crystal axis [111] as the optical axis and the second lens group (105, 106) having the crystal axis [100] as the optical axis. ) Are each composed of a pair of fluorite lenses. However, at least one of the first lens group having the crystal axis [111] as the optical axis and the second lens group having the crystal axis [100] as the optical axis is composed of three or more fluorite lenses. Examples are also possible. FIGS. 7A and 7B are diagrams illustrating the configuration and optical paths of a first lens group and a second lens group in a projection optical system according to a modification of the first embodiment. Hereinafter, a modified example of the first embodiment will be described with reference to FIGS. 7A and 7B.

Referring to FIG. 7A, a second lens group having the crystal axis [100] as an optical axis includes a second A lens group including a pair of fluorite lenses 105a and 105b and one fluorite lens 106. and a second B lens group consisting of a. Here, the fluorite lenses 105a and 105b are such that the orientation of the crystal axis [001] in the plane perpendicular to the optical axis is It is the same. In the fluorite lens 106a, the direction of the crystal axis [001] in the plane perpendicular to the optical axis is rotated by 45 ° relative to the fluorite lenses 105a and 105b. . In the second lens group of the modified example, the sum of the optical path lengths (105 am + 105 bm) in the second A lens group and the second B lens for 10 lm of the luminous flux corresponding to 60 to 90% of the image side NA by suppressing the difference between the optical path length in the group (106 am) within ^{^{± 0. 5 X 106 Χλ 3 (}} cm), is substantially constant birefringence regardless of the azimuth angle from the optical axis AX 101 be able to.

On the other hand, referring to FIG. 7B, the first lens group having the crystal axis [111] as the optical axis is composed of a first A lens group including a pair of fluorite lenses 109a and 109b, and one fluorescent lens. A first B lens group consisting of a stone lens 110a. Here, the directions of the crystal axes [-110] of the fluorite lenses 109a and 109b in a plane perpendicular to the optical axis are the same. In the fluorite lens 110a, the orientation of the crystal axis [110] in the plane perpendicular to the optical axis is rotated by 60 ° relative to the fluorite lenses 109a and 109b. ing. In the first lens group of the modified example, the sum of the optical path lengths in the first A lens group (1 09 am + 109 bm) and the first B lens group for 102 m of the luminous flux corresponding to 60% to 90% of the image side NA by suppressing the difference between the optical path length (1 10 am) within Judges ^{^{0. 5 X 10- 6 Χλ 3 (}} cm) in, to a substantially constant birefringence regardless of the azimuth angle from the optical axis AX10 1 be able to.

Furthermore, 1.5 times the total optical path length (10 5 am + 106 am + 105 bm) of the second lens group with the crystal axis [100] as the optical axis, and the crystal axis [1 1 1] as the optical axis that by setting the difference within ^{^{± 1. 0 Χ 10- 6 Χλ 3}} (cm) of the sum of the optical path length (109 am + 109 bm + 110 am) in the first lens group, from the optical axis AX 10 1 Birefringence, which is almost constant with respect to azimuth, can be canceled out, and the effect of birefringence can be almost completely eliminated.

In the above-described modified example, each of the first B lens group and the second B lens group includes one fluorite lens. However, the present invention is not limited to this. Like the first A lens group and the second A lens group, each of the first B lens group and the second B lens group may include a plurality of fluorite lenses. it can. in this case, Needless to say, the sum of the optical path lengths in the first B lens group and the sum of the optical path lengths in the second B lens group are also the sum of the optical path lengths in the plurality of fluorite lenses.

In the above-described modified example, in the second A lens group, a pair of fluorite lenses 105a and 105b are disposed relatively close to each other along the optical path of the image forming light beam. In the first A lens group, a pair of fluorite lenses 109 a and 109 b are arranged close to each other along the optical path of the image forming light beam. However, in general, each of the first A lens group, the first B lens group, the second A lens group, and the second B lens group is limited to a configuration in which a plurality of fluorite lenses are arranged close to each other. It is not something to be done.

For example, between the fluorite lenses in each lens group, a quartz lens made of quartz glass or a crystal lens formed of a crystalline material but having the other crystal axis as the optical axis (hereinafter, these are not considered) Lens)), the effect of the present invention is exhibited. However, when the non-considered lenses arranged in each lens group have relatively large power (refractive power), each lens group (1 A, 1 B, 2 In A, 2B), the angle between the exposure light beam and the optical axis greatly differs, and the effect of eliminating birefringence according to the present invention may be reduced. For this reason, in each of the first A lens group, the first B lens group, the second A lens group, and the second B lens group, a plurality of fluorite lenses are located close to each other along the optical path of the imaging light beam. It is desirable to be arranged.

Similarly, the first A lens group and the first B lens group constitute a first lens group, and the birefringence is eliminated by the interaction between the first A lens group and the first B lens group. It is desirable that no lens having a large power be arranged. It is further desirable that the first A lens group and the first B lens group are arranged close to each other along the optical path of the image forming light beam. This is the same between the second A lens group and the second B lens group that constitute the second lens group.

Although there is no problem in the projection optical system according to the first embodiment, depending on the design type of the projection optical system, when a lens having a large power is disposed between the first lens group and the second lens group. However, the birefringence canceling effect between the first lens group and the second lens group may be weakened. In such a projection optical system, the first lens It is desirable not to place a lens having a large power between the lens group and the second lens group. It is further desirable that the first lens group and the second lens group are arranged close to each other along the optical path of the image forming light beam. In the above embodiment, the image forming light flux in each lens formed of a crystal such as fluorite is a light flux converging toward a photosensitive substrate (substrate to be exposed) 102 such as a wafer. And In this case, in a lens pair (first lens group) having the fluorite crystal axis [11 1] as the optical axis, the crystal orientation of both lenses is set to the crystal axis [1 1 1] as the optical axis. As described in the above embodiment, it is preferable to rotate the image by 60 degrees from the center. However, the luminous flux of a specific lens changes so as to diverge toward the photosensitive substrate 102 due to the presence of a lens having a large power between two or more lenses that form a pair. In some cases, the birefringence produced by this lens will have a different rotational anisotropy than the birefringence produced by other lenses.

In other words, in the case of a divergent light beam, the angle with respect to the optical axis (crystal axis [111]) is opposite to that of the convergent light beam. Referring to FIG. 5A, the angle formed by the convergent light beam with the optical axis AX100 is positive, and when the light beam is incident on the optical axis AX in FIG. 5A from the right side, the divergent light beam becomes the optical axis AX100. The angle formed becomes negative, and the light enters from the left side with respect to the optical axis AX in FIG. 5A. At this time, the birefringence effect of the divergent light beam is the same as the effect when the convergent light beam is incident on the lens rotated 60 degrees around the optical axis (crystal axis [1 1 1]) shown in Fig. 5B. become. Therefore, in the first lens group with the crystal axis [111] as the optical axis, the imaging light flux passing through the inside of the first lens group is converged on one side and diverged on the other side. It is not necessary to rotate them by degrees, and it is better for the same crystal axis to point in the same direction in a plane perpendicular to the optical axis. On the other hand, in the lens pair (the second lens group) with the crystal axis [100] of the fluorite crystal as the optical axis, as shown in FIGS. 6A and 6B, both the convergent light beam and the divergent light beam are birefringent Since the effect of is the same, it is still better to rotate the lens pair 45 degrees around the optical axis for a lens pair in which the imaged light beam passing through it converges on the one hand and diverges on the other.

FIG. 8 is a diagram schematically showing a configuration of a projection optical system according to a second embodiment of the present invention. It is. In the second embodiment, the present invention is applied to the wavelength lambda (nm) is 1 5 7 nm of F ₂ with respect to laser aberration correction optimized catadioptric projection optical system. In the projection optical system 200 (corresponding to the projection optical system 300 in FIG. 1) of the second embodiment, one point on the reticle 201 (corresponding to the reticle 101 in FIG. 1) is emitted. The reflected light is deflected by a reflecting prism 203 serving as an optical path changing means, and then passed through lenses 205 and 206 arranged along an optical axis AX200b to form a concave reflecting mirror 2. It is incident on 04. The light beam reflected by the concave reflecting mirror 204 is deflected again by the reflecting prism 203 through the lenses 206 and 205. The light beam deflected by the reflecting prism 203 is transferred to the wafer 202 (the wafer 102 in FIG. 1) through lenses 207 to 212 arranged along the optical axis AX200a. Focus on one point above. Thus, a projected image of the pattern drawn on the reticle 201 is formed on the wafer 202. In the second embodiment, all the lenses 205 to 212 are formed of calcium fluoride crystals (fluorite).

In the projection optical system 200 of the second embodiment, the lens group that causes the birefringence of fluorite significantly has an optical axis AX 200 a or AX This lens group forms a large angle with respect to 200 b. Referring to FIG. 8, it can be seen that the fluorite lenses 205 and 206 located near the concave reflecting mirror 204 and the fluorite lenses 210 and 2 located near the wafer 202. In 1 1 and 2 12, the traveling direction of the imaging light flux forms a large angle with respect to the optical axis AX200a or AX200b. Since which lens causes the remarkable effect of birefringence fluctuates depending on the lens design, the lens that causes the remarkable effect of birefringence is not always the above-mentioned lens.

In particular, in the catadioptric projection optical system 200, the imaging luminous flux is transmitted twice back and forth through the fluorite lenses 205 and 206 arranged near the concave reflecting mirror 204. The effect of the birefringence of the fluorite lenses 205 and 206 will be doubled. Therefore, in the second embodiment, in the first lens group including the fluorite lenses 205 and 206, the crystal axis [111] is set to the optical axis AX200b (hence, the fluorite lens 2). 05 and 206 optical axes). And the fluorite lenses 205 and 206 The crystal axis [1-110] in the plane perpendicular to the optical axis is arranged to rotate relative to the optical axis by 60 °. Therefore, the fluorite lens 205 constitutes the first A lens group, and the fluorite lens 206 constitutes the first B lens group.

On the other hand, in the second lens group including the fluorite lenses 210, 211, and 212, the crystal axis [100] coincides with the optical axis AX200a. Here, of the three fluorite lenses 210 to 212, the thickest fluorite lens 210 constitutes the second A lens group, and the other two fluorite lenses 211 and 212 constitute the second B lens group. Is composed. That is, the fluorite lens 210 and the fluorite lenses 211 and 212 are arranged such that the crystal axis [001] in a plane perpendicular to the optical axis rotates relatively 90 ° about the optical axis. Is placed.

FIGS. 9A and 9B are diagrams illustrating an optical path in a fluorite lens in the projection optical system according to the second embodiment. 9A and 9B, a light beam (a light beam corresponding to the image-side NA) incident on the wafer 202 at the maximum incident angle 0200 (see FIG. 8) is indicated by reference numeral 200e. In the second embodiment, the sum of the optical path lengths in the first A lens group (205 am + 205 bm) and the optical path lengths in the first B lens group for 200 m of light flux equivalent to 60% to 90% of the image side NA are described. the sum (206 am + 206 bm) is set to be within Sagado ^{^{0. 5 X 10- 6 Χλ 3 (}} cm) of the. The sum of the optical path length in the 2nd A lens group (210 m) and the optical path length in the 2nd B lens group (211 m + 212 m) for a light flux of 20 Om corresponding to 60% to 90% of the image side NA the difference is set ± 0. so within ^{^{5 X 10 _ 6 Χλ 3 (}} cm) of the. Then, for a light flux of 20 Om corresponding to 60% to 90% of the NA on the image side, the sum of the optical path lengths in the first lens group with the crystal axis [1 1 1] as the optical axis (205 am + 205 bm + 206 am + 206 and bm), 1. ± difference between 5-fold 1. 0 X 10- ⁶ Χλ ³ of the sum of the optical path length of the second lens unit to the crystal axis [100] to the optical axis (21 Om + 21 lm + 212m ) (cm). Thus, in the second embodiment, as in the first embodiment, the effect of birefringence can be almost completely eliminated by the combination of the first lens group and the second lens group.

By the way, in the second embodiment described above, all the lenses 205 to 212 are formed of fluorite. Therefore, birefringence also occurs in the fluorite lenses 207 to 209 other than the first lens group (205, 206) and the second lens group (210, 211, 212). However, the fluorite lenses 207 to 209 form a relatively small angle with respect to the optical axis in the traveling direction of the imaging light beam. Therefore, by making the optical axis of the fluorite lenses 207 to 209 coincide with the crystal axis [111] or [100], the amount of birefringence generated in each of the fluorite lenses 207 to 209 can be reduced. As a result, the influence of birefringence by the fluorite lenses 207 to 209 can be reduced. However, if the effects of birefringence by the fluorite lenses 207 to 209 cannot be ignored, the first lens group and the fluorite lenses 207 to 209 (actually, four or more lenses are required) are used. What is necessary is just to constitute the second lens group, and apply the present invention to the first lens group and the second lens group. That is, in the first lens group, the optical axis coincides with the crystal axis [111], and in the second lens group, the optical axis coincides with the crystal axis [100]. Then, the first A lens group and the first B lens group that constitute the first lens group are set so that the crystal axis directions have a predetermined angular relationship around the optical axis, and the second lens group is formed. The second A lens group and the second B lens group are set such that the crystal axis directions have a predetermined angular relationship about the optical axis. Furthermore, by setting the optical path length in each lens group (1A, IB, 2A, 2B) to satisfy a predetermined relationship for the luminous flux equivalent to 60 to 90% of the image side NA, the birefringence The effect can be corrected with higher accuracy.

In the first and second embodiments, the allowable value for the difference between the sum of the optical path lengths in the first A lens group and the sum of the optical path lengths in the first B lens group, and the second A lens group the allowable value for the difference between the sum of the optical path length of the sum of the optical path length and the second 2 B lens group of the inner, is set to ^{± 0. 5 X 10- 6 Χλ} 3 (cm). A specific numerical value of this allowable value is ± 3.6 (cm) in the case of an ArF laser light source having a wavelength λ of 193 (nm), that is, in the case of the first embodiment. Moreover, the ± 1. 9 (cm) in the case where the F ₂ laser light source or second embodiment of the wavelength λ is 1 57 (nm). On the other hand, the allowable value for the difference between the sum of the optical path length of 1. 5 times a first lens group of the sum of the optical path length in the second lens group, the ^{^{± 1. 0 Χ 10- 6 Χλ 3}} (cm) You have set. A specific numerical value of the allowable value is ± 7.2 (cm) in the case of an ArF laser light source having a wavelength λ of 193 (nm), that is, in the case of the first embodiment. Moreover, the ± 3. 8 (cm) in the case where the F ₂ laser primary light source or second embodiment of the wavelength input is 157 (nm). As described above, the factor of the cube of the wavelength λ in the equation that expresses the allowable value of the optical path length difference is that in the case of birefringence that depends on the traveling direction of light in the crystal material, the amount of change in the refractive index, the amount of deviation of the wavefront of the imaging light beam (unit length) generated in proportion to the λ_ ^2, since this is the wavefront aberration (phase) is an amount which adversely affects the imaging properties in proportion to ^lambda-3 It is.

The standard of the optical path length difference is that the imaging characteristic is assumed to be a pattern with a fineness of about k1 factor = 0.35 (line width = k1 幅 λ / ΝΑ: λ is the exposure wavelength). This is an allowable value that does not have a significant effect, and it goes without saying that a stricter standard is required when the pattern size to be exposed is smaller. Here, the optical path length refers to the optical path length (geometric length) in the crystal material itself, and is not a value multiplied by the refractive index or a value divided by the refractive index.

In the first and second embodiments described above, the light flux corresponding to 60 to 90% of the image side ΝΑ (maximum ΝΑ), that is, 0.6 to 0.9 times the image side に対してに対して with respect to the optical axis. Regarding the luminous flux having an angle corresponding to 9 times, the difference in the total optical path length in the crystal lens in each lens group (1A, 1B, 2A, 2B) and the difference between the first and second lens groups The problem is the difference of the total optical path length in the crystal lens in the above. This is because the luminous flux within 70% of the image-side NA is equivalent to about 50% of the entire imaging luminous flux, so the effect of eliminating birefringence is maximized for the luminous flux equivalent to about 70% of the image-side NA. This is because birefringence can be eliminated with the best balance for the entire image forming light beam.

However, depending on the type of aberration caused by birefringence and the type of pattern to be exposed by the projection optical system, the aberration of the light beam closer to the image side NA may have a greater effect on the imaging characteristics. . Therefore, for the luminous flux whose coordination spreads slightly to the maximum NA side around 70% of the image side NA, that is, the luminous flux equivalent to 60 to 90% of the image side NA, the effect of eliminating birefringence should be maximized. It is desirable to set to Further, in the first and second embodiments, the description of the present invention is simplified. In order to obtain good imaging performance, the effective illumination area on reticle 101 (201) is focused on only the luminous flux emitted from one point on reticle 101 (201). It is needless to say that the above relationship of the present invention should be satisfied with respect to the image forming light flux reaching the effective exposure area on the wafer 102 (202) from all points in the above.

As a third embodiment of the present invention, there is a method of eliminating the influence of birefringence by combining lens groups having the crystal axis [110] as the optical axis. FIGS. 108 to 10D are views for explaining birefringence when the optical axis of the fluorite lens is matched with the crystal axis [1 10]. For example, when the third embodiment is applied to the projection optical system of the first embodiment shown in FIG. 2, as shown in FIGS. 1OA and 10B, the optical axes of the fluorite lenses 105 and 106 are changed. Are set to coincide with the crystal axes [1 10]. The fluorite lenses 105 and 106 are arranged such that the crystal axis [001] existing in a plane perpendicular to the optical axis AX 102 rotates relatively 90 ° about the optical axis. In other words, the direction of the crystal axis [001] of the fluorite lens 106 is rotated around the z axis by 0106 = 90 ° with respect to the fluorite lens 105. Thus, the fluorite lens 105 constitutes the third A lens group, the fluorite lens 106 constitutes the third B lens group, and the fluorite lenses 105 and 106 constitute the third lens group.

The combination using the crystal axis [1 10] as the optical axis is more birefringent (R polarized light and R) than the combination using the crystal axis [1 1 1] as the optical axis or the combination using the crystal axis [100] as the optical axis. (Difference in refractive index from 0-polarized light) can be reduced. However, in the combination with the crystal axis [1 10] as the optical axis, the birefringence with respect to the azimuth centered on the optical axis is poor in uniformity, and nonuniformity of 90 ° cycle remains.

Therefore, in the third embodiment, as shown in FIGS. 10C and 10D, the optical axes of the fluorite lenses 109 and 110 are both set so as to coincide with the crystal axis [1 10]. Then, the fluorite lenses 109 and 110 are arranged such that the crystal axis [00 1] existing in a plane perpendicular to the optical axis AX 102 is relatively rotated by 90 ° about the optical axis. Furthermore, the relative positions of the fluorite lenses 105 and 106 and the fluorite lenses 109 and 110 are relatively rotated by 45 ° about the optical axis AX102. Set to have.

That is, based on the fluorite lens 105, the orientation of the crystal axis [00 1] of the fluorite lens 106 is rotated around the z-axis by 0106 = 90 °, and the orientation of the fluorite lens 109 is the orientation of the crystal axis [001]. Is rotated about 0109 = 45 ° around the one z-axis, and the direction of the crystal axis [001] of the fluorite lens 110 is rotated about one z axis by 0 1 10 = 135 °. Thus, the fluorite lens 109 constitutes a fourth A lens group, the fluorite lens 110 constitutes a fourth B lens group, and the fluorite lenses 109 and 110 constitute a fourth lens group.

As described above, in the third embodiment, a pair of lens pairs having a non-uniformity of 90 ° cycle, that is, the third lens group and the fourth lens group are relatively rotated by 45 ° and arranged, so that 90 ° Periodic non-uniformities are almost completely canceled. In addition, as described above, since the residual birefringence of the lens pair arranged by rotating the crystal axis [1 10] relative to the optical axis by 90 ° is small, the 90 ° rotating pair must be further rotated by 45 °. Thereby, a sufficient effect of removing birefringence can be obtained.

In the third embodiment, the third lens group and the fourth lens group forming the 90 ° rotation pair are not limited to the configuration including two fluorite lenses, but include three or more fluorescent lenses. Each can also be constituted by a stone lens. Further, for the light flux corresponding to 60% ~ 90% of the image-side NA, a difference of ± between the optical path length of the third optical path length of the A lens group and the third B lens group ^{^{0. 5 X 10- 6 Χλ 3}} (cm ) and sets within, it is desirable to set the difference between the optical path length of the fourth optical path length of the a lens group and the 4B lens group ^{± 0. 5 X 10- 6 Χλ} 3 (cm) within. Furthermore, for a beam equivalent to 60 to 90% of the NA on the image side, the difference between the sum of the optical path lengths in the third lens group and the sum of the optical path lengths in the second lens group is expressed as Sat 1.0 X 10_ It is desirable to set within ⁶ Χλ ³ (cm).

In the third embodiment described above, two fluorite lenses (lens 105 and lens 105) belonging to the third lens group disposed close to each other among the lenses having the crystal axis [1 10] as the optical axis 106), and the two fluorite lenses (lens 109 and lens 110) belonging to the fourth lens group located close to each other, The crystal axes [001] existing in the vertical plane are arranged so as to rotate by 90 ° about the optical axis. Further, the third lens group and the fourth lens group are arranged so as to rotate relatively by 90 ° about the optical axis. However, in the lens group having the crystal axis [110] as the optical axis, that is, in the [110] lens group, the relationship between the rotation angles of the respective lenses around the optical axis is not limited to this.

That is, for the four lenses of the fluorite lens 105, the fluorite lens 106, the fluorite lens 109, and the fluorite lens 110, the crystal axes existing in the plane perpendicular to the optical axis [ By determining the relationship between the rotation angles of the lenses so that [01] is separated by 45 ° about the optical axis, a birefringence removing effect equivalent to that of the third embodiment can be obtained. In this case, of the four fluorite lenses, the second lens has a positional relationship in which the second lens is rotated by 45 ° in a predetermined direction about the optical axis with respect to the first lens. Have a positional relationship rotated by 45 ° in the same predetermined direction about the optical axis with respect to the third lens, and the third lens is the same predetermined with respect to the fourth lens about the optical axis. Has a positional relationship rotated by 45 ° in the direction of.

Further, as described above, each of the fluorite lens 105, the fluorite lens 106, the fluorite lens 109, and the fluorite lens 110 may be composed of a plurality of fluorite lenses. This is the same as the other embodiments. In this case, each of the at least four fluorite lenses is oriented in a predetermined direction in which the crystal axis [001] existing in a plane perpendicular to the optical axis is separated by 45 ° from the optical axis. It is classified into four matching lens groups, namely, any one of the sixth lens group, the seventh lens group, the eighth lens group, and the ninth lens group, and rotated by a predetermined angle about the optical axis. Be placed.

Then, for example, for a light flux equivalent to 60 to 90% of the NA on the image side, the sum L 6 of the optical path lengths in the sixth lens group, the sum L 7 of the optical path lengths in the seventh lens group, and the sum L 7 in the eighth lens group The total sum L8 of the optical path lengths and the total sum L9 of the optical path lengths in the ninth lens group are set to be substantially equal to each other. Specifically, the sum L 6 of the optical path lengths in the sixth lens group, the sum L 7 of the optical path lengths in the seventh lens group, the sum L 7 of the optical path lengths in the eighth lens group, and the sum L 8 in the ninth lens group Difference between the sum of the optical path lengths arbitrarily selected and the sum of the optical path lengths L 9 There set ^{± 0. 5 X 10- 6 X} λ 3 (cm) so that within. Thus, similarly to the third embodiment, the influence of birefringence can be reduced.

As described above, in the [110] lens group, which is arranged with the crystal axis [1 10] as the optical axis and relatively rotated about the optical axis, the crystal axis [11 1] is rotated relative to the optical axis by 60 °. The effect of birefringence can be reduced to a lesser extent than with the [100] lens group in which the [111] lens group and the crystal axis [100] are rotated relative to each other by 45 ° about the optical axis. [1 10] In the birefringence remaining in the lens group, the refractive index (nR 1 10) for the R-polarized light may be higher than the refractive index (n 0 1 10) for the S-polarized light. The analysis was made clear by the present inventor.

That is, the sign of the birefringence remaining in the [1 10] lens group is the same as the sign of the birefringence remaining in the [1 11] lens group, and the sign of the birefringence remaining in the [100] lens group is the opposite sign. . Therefore, by using the [1 10] lens group and the [100] lens group in combination, it is possible to offset the effects of birefringence. further,

By using a combination of the [1 10] lens group and the [100] lens group and the [1 1 1] lens group, it becomes possible to cancel the effect of birefringence.

More specifically, [1 10] the difference between the refractive index nR 110 and the refractive index n 0 1 10 for the R polarized light in the lens group, and the refractive index nR 1 for the R polarized light in the [1 00] lens group The difference between the refractive index n 0 100 for 00 and 0 polarized light,

[1 11] It is found that the relationship shown in the following expression (1) holds between the difference between the refractive index nR 11 1 for R polarized light and the refractive index n 01 11 for polarized light in the lens group. Analysis revealed that

(nRHO-n ^ 110): (nR100-n ^ 100): (nRlll-n 0111) = 3:-12: 8 (1) In the above formula (1), the refractive index nR 100 and the refractive index n Focusing on the difference between 0100 and the difference between the refractive index nR 111 and the refractive index n 0111, the following relationship (2) is obtained. Equation (2) indicates that the birefringence of the lens layer (105, 106) with the crystal axis [100] as the optical axis, that is, (nR 100—n 0 100) is the light intensity of the crystal axis [1 1 1]. The birefringence amount at the lens pair (109, 1 10) as the axis, that is, about 1.5 times the value of (nR 1 1 1 _n 01 1 1) ”. Consistent with the description in

(nRlOO-n0100): (nRlll-n0111) =-12: 8 (2)

Therefore, in an optical system including a plurality of lenses (optical elements) formed of crystals belonging to the cubic system, for example, for a light beam equivalent to 60 to 90% of the image side NA,

[1 10] Sum of optical path lengths L 1 10 in lens group, [100] Sum of optical path lengths in lens group L 100, and [1 11] Sum of optical path lengths in lens group L 1 1 1 In the meantime, when the relationship shown in the following equation (3) holds, the effect of birefringence can be minimized.

3 XL 1 10- 12 XL 100 + 8XL 1 1 1 = 0 (3)

However, as described above, the lens groups ([110] lens group, [100] lens group, and [1 11] lens group) each having the crystal axis as the optical axis have a desired rotation angle relationship and a desired optical path length. It is needless to say that the lens group has the following relationship. In practice, it is difficult to set strictly 0 the value of the left-hand side of equation (3), the left side value ± 8 of formula ^{(3). 0X 10- 6 Χλ} 3 (cm) to be within By setting, it becomes possible to substantially avoid the influence of birefringence. The allowable value on the left-hand side of this equation (3) is also an allowable value on the premise of exposing a pattern having a fineness of about 0.15 to the kl factor, similar to the aforementioned allowable value. Therefore, when exposing a finer pattern, it is necessary to set a stricter tolerance, and when exposing a non-fine pattern, it is needless to say that a smaller tolerance is sufficient.

Equation (3) does not necessarily specify only the relationship between the optical path lengths when all the [1 10] lens groups, the [100] lens groups, and the [1 1 1] lens groups are included. . For example, to reduce the effect of birefringence in an optical system that includes only the [1 1 0] lens group and the [1 100] lens group without including the [1 1 1] lens group, the following method is used. The relationship shown in the following equation (4) should be established between the sum L 1 10 of the optical path lengths in the lens group and the sum 100 of the optical path lengths in the [100] lens group.

3 XL 1 10-12 XL 100 = 0 (4)

Similarly, to reduce the effects of birefringence in an optical system that includes only the [1 1 1] lens group and the [100] lens group without including the [1 10] lens group, [1 1 1] The relationship shown in the following expression (5) may be established between the sum L 1 11 of the optical path lengths in the lens group and the sum L 100 of the optical path lengths in the [1 00] lens group.

1 2 XL 1 00-8 XL 1 1 1 = 0 (5)

Also in these equations (4) and (5), it is difficult to set the value on the left-hand side exactly to 0, but both the value on the left-hand side of equation (4) and the value on the left-hand side of equation (5) are ± 8. by setting ^{^{0 X 10- 6 Χλ 3 (cm}} ) to be within, it is possible to substantially avoid the influence of birefringence. Based on this tolerance, Equation (5) is

Equation (6) can be transformed, and equation (6) can be transformed as shown in equation (7).

I 12 XL 1 00-8 XL 1 1 1 I≤8. 0 X 1 0 _6 Χλ 3 (6)

I 1. 5 XL 1 00 -L 1 1 1 I≤ 1. 0 X 1 0- 6 Χλ 3 (7)

Similarly, based on this allowable value, equation (4) can be transformed as shown in equation (8), and equation (8) can be further transformed as shown in equation (9).

I 3 XL 1 1 0-1 2 XL 1 00 | ≤ 8.0 X 10 0 ¹⁶ X λ ³ (8)

| L 1 1 0 -4XL 1 00 |. ≤2 7 X 1 0- 6 Χ λ 3 (9)

Here, equation (7) is expressed as “1.5 of the sum of the optical path lengths (105 m + 106 m) in the second lens group (105, 106) with the crystal axis [100] as the optical axis. The difference between the magnification and the sum of the optical path lengths (109 m + 110 m) in the first lens group (109, 110) with the crystal axis [1 1 1] as the optical axis is ± 1.0 X It is consistent with the description in the first embodiment to the effect that 1 0- ⁶ Χλ ³ to (cm) set to be within ". Equation (9) is

[1 1 0] sum L 1 1 0 of the optical path length in the lens group, the difference between four times the [1 00] the sum of the optical path length in the lens group L 1 00, ± 2. 7 X 10- 6 If it is within Χλ ³ (cm), it means that good imaging characteristics can be obtained.

Note that, depending on the design of the optical system, there may be many lenses whose crystal axis [1 110] should be coincident with the optical axis. In that case, the lens whose crystal axis [1 110] should be coincident with the optical axis is divided into the above four lens groups (the sixth to ninth lens groups), and the optical axis is set between the lens groups. By rotating each lens around the optical axis so that the crystal axes [00 1] existing in the vertical plane are separated by 45 ° about the optical axis, Good.

Alternatively, the lens whose crystal axis [1 10] should be coincident with the optical axis can be divided into eight lens groups. That is, two sets of the above four lens groups (sixth lens group to ninth lens group) are provided, and in each of the four lens groups, a crystal axis [001] existing in a plane perpendicular to the optical axis is set. Rotate each lens about the optical axis so that it is 45 ° apart from the optical axis. In this case, since the rotational anisotropy of the birefringence is minimized in each of the four lens groups, the distance between the first four lens groups and the second four lens groups is reduced. There is no particular restriction on the relationship between the crystal directions (the direction of the crystal axis [00 1] existing in a plane perpendicular to the optical axis).

The division into such lens groups is not limited to the above-described four or eight groups, and [1 10] a division in which four lens groups forming a lens group are provided in an arbitrary number of sets, ie, four Any division into lens groups of integer multiples of (4, 8, 12, ···) is sufficient. In this case, in each set of [1 10] lens groups, each lens is arranged such that the crystal axis [001] existing in a plane perpendicular to the optical axis is separated by 45 ° about the optical axis. Rotate around the optical axis. Then, for example, for a light flux corresponding to 60% to 90% of the image side NA, the sum of the optical path lengths in each lens group in which the crystal axis [001] points in the same direction may be set to be substantially equal to each other. Furthermore, since the sum L 110 of the optical path lengths in the plurality of [1 10] lens groups satisfies the above relational expressions (3), (4), and (5), the adverse effect of birefringence is substantially eliminated. .

In addition, there is a possibility that there are a large number of lenses whose crystal axis [100] should be coincident with the optical axis. In this case, it is possible to form only a plurality of [100] lens groups. Again, within each set of [100] lens groups, the rotational relationship in the crystal axis direction for each lens is set to 45 °, but between different sets of [100] lens groups, There are no particular restrictions on the relationship. When the sum L100 of the optical path lengths in the plurality of [100] lens groups satisfies the above relational expressions (3), (4), and (5), the adverse effect of birefringence is substantially eliminated.

Furthermore, even when there are a large number of lenses whose crystal axes [1 1 1] should be coincident with the optical axis, similarly, a plurality of [1 1 1] lens groups can be formed. in this case Also, within each set of [111] lens groups, the rotation relationship in the crystal axis direction for each lens is set to 60 °, but between different sets of [1 11] lens groups, the relationship in the crystal axis direction is There are no particular restrictions. When the sum L 111 of the optical path lengths in the plural [11 1] lens groups satisfies the above relational expressions (3), (4) and (5), the adverse effect of birefringence is substantially reduced. Disappears.

FIG. 11 is a diagram schematically showing a configuration of a projection optical system according to a fourth embodiment of the present invention. In the fourth embodiment, like the second embodiment, the wavelength lambda (nm) 157 'aberration correction for F ₂ laser nm is the present invention is applied to an optimized catadioptric projection optical system ing. In the projection optical system 300 according to the fourth embodiment, a light beam emitted from one point on a reticle 301 (corresponding to the reticle 101 in FIG. 1) is deflected by a reflecting prism 303 serving as an optical path changing means, The light enters the concave reflecting mirror 304 via lenses 305 and 306 arranged along the axis AX 300b.

The light beam reflected by the concave reflecting mirror 304 is deflected again by the reflecting prism 303 via the lenses 306 and 305. The light beam deflected by the reflection prism 303 is condensed at one point on the wafer 302 (corresponding to the wafer 102 in FIG. 1) via the lenses 307 to 314 arranged along the optical axis AX 300a. . Thus, a projected image of the pattern drawn on the reticle 301 is formed on the wafer 302. In the fourth embodiment, all lenses are formed of calcium fluoride crystals (fluorite).

More specifically, in the fourth embodiment, in the fluorite lenses 305 and 306, the crystal axis [110] matches the optical axis AX 300b. Also, fluorite lens 31

In 1 and 312, the crystal axis [1 10] is aligned with the optical axis AX 300a. Further, in the fluorite lenses 313 and 314, the crystal axis [100] is aligned with the optical axis AX 300a. In other words, fluorite lens 305, 306, 31

1 and 3 12 constitute the [1 1 0] lens group, and the fluorite lenses 3 13 and 3 14

[100] The lens group is constituted.

FIG. 12A and FIG. 12B are diagrams illustrating an optical path in a fluorite lens in a projection optical system according to the fourth embodiment. In Figures 12A and 12B, A light beam (a light beam corresponding to the image-side NA) incident on the upper surface 302 at the maximum incident angle 0300 (see FIG. 11) is indicated by reference numeral 300 e. The luminous flux corresponding to 60 to 90% of the NA on the image side is indicated by reference numeral 300 m. Referring to FIG. 12A, in the fluorite lenses 305 and 306, the imaging light beam passes through the lens twice in a reciprocating manner. Therefore, for a beam flux of 30 Om corresponding to 60% to 90% of the NA on the image side, the optical path length in the fluorite lens 305 is (305 am + 305 bm), and the optical path length in the fluorite lens 306 is (306 am + 306 bm).

On the other hand, referring to FIG. 12B, for a light flux of 300 m corresponding to 60% to 90% of the NA on the image side, the optical path length in the fluorite lens 311 is 31 lm, and the optical path length in the fluorite lens 312 is 312 m, the optical path length in the fluorite lens 313 is 313 m, and the optical path length in the fluorite lens 314 is 314 m. In the fourth embodiment, each of the optical path lengths (305 am + 305 bm, 306 am + 306 bm, 31 1 m, 312 m) in the fluorite lens 305, 306, 31 1, 3 12 having the crystal axis [1 10] as the optical axis ) is ± 0. to be approximately equal in the range of ^{^{5 X 10- 6 Χλ 3 (cm}} ), have set a thickness of each lens.

In other words, of the two optical path lengths arbitrarily selected from the respective optical path lengths (305 am + 305 bm, 306 am + 306 bm, 31 1m, 312m) in the fluorite lenses 305, 306, 311, 312 difference so that within ^{^{± 0. 5 X 10- 6 Χλ 3}} (cm), have set a thickness of each lens. In the fluorite lenses 305, 306, 311, and 312, the crystal axis [100] existing in a plane perpendicular to each optical axis (AX 300a, AX 300b) is 45 ° centered on the optical axis. The relationship between the rotation angles of the lenses is set so that they are separated.

Further, the fluorite lens 313 and 314 to the crystal axis [100] to the optical axis is also the respective optical path lengths (313m, 314m) is ± 0. 5 X 10 - becomes substantially equal in the range of ^{6 Χλ} ³ (cm) In this way, the thickness of each lens is set. In other words, as the difference between the optical path length 314m in the optical path length 313m and fluorite lens 314 in the fluorite lens 313 is within the soil ^{^{0. 5 X 10- 6 Χλ 3 (}} cm), the thickness of each lens Is set. And with the fluorite lenses 3 13 and 314, the optical axis AX 300a The crystal axis [001] existing in the vertical plane is set to have a relative rotation of 45 °.

Thus, in the fourth embodiment, the [1 10] lens group composed of four lenses having the crystal axis [1 10] as the optical axis, and the two lenses having the crystal axis [100] as the optical axis. [100] The effect of birefringence is canceled between the lens group and the lens group, so that good imaging characteristics can be obtained. [1 10] The sum of the optical path lengths of the fluorite lenses 305, 306, 311, and 312 in the lens group (305 am + 305 bm + 306 am + 306 bm + 3 1 lm + 312 m = L 1 10) 100] By setting the sum of the optical path lengths (313m + 314m = L100) of each of the fluorite lenses 313 and 314 in the lens group to satisfy the above relational expression (8) or (9), The killing effect can be maximized, and the effect of birefringence can be minimized.

In other words, the absolute value of (3 XL 1 10-12 XL 100) between [1 10] the sum of the optical path lengths in the lens group L 110 and the [100] the sum of the optical path lengths in the lens group L 100 There ^{^{8. 0 X 10- 6 Χλ 3 (}} cm) to be less than the value, or the absolute value of ^{^{2. 7 X 10- 6 Χλ 3 (}} cm) below the (L 1 1 0- 4 XL 100 ) By setting such a value, the above-described offset effect can be maximized, and the influence of birefringence can be minimized. In the fourth embodiment as well, the other fluorite lenses (lenses 307 to 310) can be further set to a combination that eliminates birefringence to further exert the effect of eliminating birefringence.

In each of the above embodiments, the [1 1 1] lens group whose optical axis is coincident with the crystal axis [11 1] is set at 60 ° around the optical axis between a plurality of lenses to eliminate birefringence. It is rotated and placed. However, in the [1 1 1] lens group, the crystal orientation is rotationally symmetric about the optical axis three times (symmetrical with a period of 120 °), so that the above 60 ° rotation is 60 + 120 = It goes without saying that a rotation of 180 ° or 60 + 240 = 300 ° may be used.

Similarly, in the [100] lens group whose optical axis coincides with the crystal axis [100], the lens rotation angle for eliminating birefringence is set to 45 ° around the optical axis. However However, in the [100] lens group, the crystal orientation is rotationally symmetric about the optical axis four times (rotational symmetry with a period of 90 °), so the 45 ° rotation is 45 + 90 = 135 ° , 45 + 180 = 225. Needless to say, a rotation of 45 + 270 = 315 ° is also acceptable.

In each of the above embodiments, calcium fluoride crystal (fluorite) is used as the birefringent optical material. However, the present invention is not limited to this, and other uniaxial crystals, for example, barium fluoride may be used. crystal (B aF _2), lithium fluoride crystals (L i F), fluoride kana thorium crystals (NaF), strontium fluoride crystal (S r F _2), fluoride base Lili © beam crystals (B e F ₂₎ For example, other crystal materials that are transparent to ultraviolet light can be used. Of these, barium fluoride crystals have already been developed for large crystal materials exceeding 200 mm in diameter, and are promising as lens materials. In this case, it is preferable that the crystal axis orientation of barium fluoride (BaF ₂ ) is also determined according to the present invention. Further, in each of the above-described embodiments, the present invention is applied to the projection optical system. However, the present invention is not limited to this, and may be applied to an illumination optical system that illuminates a reticle (mask). .

In the exposure apparatus of each of the above-described embodiments, the reticle (mask) is illuminated by the illumination device (illumination step), and the transfer pattern formed on the mask is exposed on the photosensitive substrate using the projection optical system. By doing so, a micro device (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Hereinafter, a flowchart of FIG. 13 shows an example of a technique for obtaining a semiconductor device as a microdevice by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of each embodiment. I will explain.

First, in step 301 of FIG. 13, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the wafer of the lot. Then, in step 303, using the exposure apparatus of each embodiment, an image of the pattern on the mask is sequentially exposed and transferred to each shot area on the one lot of wafers via the projection optical system. Then, in step 304, after developing the photoresist on the one lot of wafer, In step 305, a circuit pattern corresponding to the pattern on the mask is formed in each shot area on each wafer by performing etching on the one lot of wafers using the resist pattern as a mask.

Thereafter, a device such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer and the like. According to the above-described semiconductor device manufacturing method, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput. In steps 301 to 305, a metal is vapor-deposited on the wafer, a resist is applied on the metal film, and the respective steps of exposure, development, and etching are performed. Prior to forming a silicon oxide film on the wafer in advance, it is needless to say that a resist may be applied on the silicon oxide film, and each step of exposure, development, etching and the like may be performed.

Further, in the exposure apparatus of each embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate). Hereinafter, an example of the technique at this time will be described with reference to the flowchart of FIG. In FIG. 14, in a pattern forming step 401, a so-called optical liquider is used in which a mask pattern is transferred and exposed to a photosensitive substrate (a glass substrate coated with a resist, etc.) using the exposure apparatus of each embodiment. The fuel process is performed. By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate is subjected to various steps such as an imaging step, an etching step, and a resist stripping step, so that a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming step 402. .

Next, in the color filter-forming step 402, a large number of sets of three dots corresponding to R (Red), G (Green), and B (BI ue) are arranged in a matrix form. Forms a color filter in which a set of three stripe filters of R, G, and B are arranged in a plurality of horizontal scanning line directions. Then, after the color filter forming step 402, a cell assembling step 403 is performed. In the cell assembling step 403, the substrate having the predetermined pattern obtained in the pattern forming step 401, and A liquid crystal panel (liquid crystal cell) is assembled using the color filters obtained in step 402 and the color filter forming step 402. In the cell assembling step 403, for example, a liquid crystal is interposed between the substrate having the predetermined pattern obtained in the pattern forming step 401 and the color filter obtained in the color filter forming step 402. To produce a liquid crystal panel (liquid crystal cell).

Then, in a module assembling step 404, components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display element, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput.

In each of the above-described embodiments, the present invention is applied to the projection optical system mounted on the exposure apparatus. However, the present invention is not limited to this. The present invention can also be applied to other general optical systems including a system, for example, an optical system for measuring aberration. Further, in the embodiments described above, but using a 1 9 3 nm F ₂ laser primary light source for supplying wavelength light A r F excimer laser light source or 1 5 7 nm supplying wavelength light, limited to Instead, for example, an Ar laser light source that supplies light with a wavelength of 126 nm can be used. Industrial applicability

As described above, the present invention realizes an optical system having good optical performance without being substantially affected by birefringence even when a birefringent crystal material such as fluorite is used. be able to. Therefore, by incorporating the optical system of the present invention into an exposure apparatus, it is possible to manufacture a good microphone port device by performing high-precision projection exposure through a high-resolution projection optical system.

Claims

The scope of the claims

1. In an optical system including a plurality of optical elements formed of crystals belonging to the cubic system, the optical axis of the optical system and the crystal axis [111] or a crystal axis optically equivalent to the crystal axis are A first element group composed of a plurality of optical elements set so as to substantially coincide with each other, and the optical axis and the crystal axis [100] or a crystal axis optically equivalent to the crystal axis substantially coincide with each other. A second element group composed of a plurality of optical elements set as described above, wherein the first element group has a positional relationship relatively rotated by a first angle about the optical axis. An element group and a first B element group,

The optical path length in the optical element of the first A element group of the light beam forming an angle within a predetermined range with respect to the optical axis is substantially equal to the optical path length in the optical element of the first B element group. On the other hand, the optical path length in the optical element of the second A element group of the light beam forming the angle in the predetermined range is substantially equal to the optical path length in the optical element of the second B element group.

According to a predetermined magnification, an optical path length in the optical element of the first element group and an optical path length in the optical element of the second element group of the light beam forming the angle within the predetermined range with respect to the optical axis are set. An optical system characterized by being set.

2. In the optical system according to claim 1,

An optical system, wherein an optical path length in an optical element in the first element group is set to about 1.5 times an optical path length in an optical element in the second element group.

3. In the optical system according to claim 2,

When the difference between 1.5 times the optical path length in the optical element in the second element group and the optical path length in the optical element in the first element group is that the wavelength of the light flux is λ (nm), Sat 1.0 X 10—An optical system characterized by being set within ⁶ Χ λ ³ (cm).

4. The optical system according to any one of claims 1 to 3, wherein the optical path length in the optical element in the first A element group and the optical path length in the optical element in the first B element group are different. the difference between the optical path length, when the wavelength of the light beam with λ (nm), ± 0. 5 X 10- 6 Χλ 3 (cm) optical system, characterized in that it is set within.

5. The optical system according to claim 1, wherein the optical path length in the optical element in the second A element group and the optical path length in the optical element in the second B element group are different from each other. the difference between the optical path length, when the wavelength of the light beam with λ (nm), ± 0. 5 X 10- 6 Χλ 3 (cm) optical system, characterized in that it is set within.

6. The optical system according to any one of claims 1 to 5, wherein the angle in the predetermined range is greater than an angle corresponding to 0.6 times an image-side numerical aperture of the optical system. An optical system characterized in that the angle is large and smaller than an angle corresponding to 0.9 times the image-side numerical aperture.

7. In the optical system according to any one of claims 1 to 6, the first A element group, the first B element group, the second A element group, and the second B element group. An optical system, wherein each of the element groups has at least one optical element.

8. In an optical system including a plurality of optical elements formed of crystals belonging to the cubic system, the optical axis of the optical system and the crystal axis [110 ° or a crystal axis optically equivalent to the crystal axis are substantially equal to each other. A third element group and a fourth element group each composed of a plurality of optical elements set to match,

The fourth element group is a position relatively rotated by a fourth angle about the optical axis. A fourth A element group and a fourth B element group having a relationship,

The optical path length in the optical element in the third A element group of the light beam forming an angle within a predetermined range with respect to the optical axis is substantially equal to the optical path length in the optical element in the third B element group, and is equal to the optical axis. On the other hand, the optical path length in the optical element of the fourth A element group of the light flux forming the angle in the predetermined range is substantially equal to the optical path length in the optical element of the fourth B element group.

An optical path length in the optical element of the third element group and an optical path length in the optical element of the fourth element group of a light beam forming the angle within the predetermined range with respect to the optical axis are set according to a predetermined magnification. An optical system characterized by:

9. In the optical system according to claim 8,

An optical system, wherein an optical path length in an optical element in the third element group is set substantially equal to an optical path length in an optical element in the fourth element group.

10. The optical system according to claim 9, wherein

The difference between the optical path length in the optical element in the third element group and the optical path length in the optical element in the fourth element group is ± 1.0 X 1 when the wavelength of the light beam is λ (nm). An optical system characterized by being set within a range of 0 to ¹⁶ Χλ ³ (cm).

1 1. The optical system according to any one of claims 8 to 10, wherein the optical path length in the optical element in the third A element group and the optical path length in the optical element in the third B element group are different. the difference between the optical path length of, when the wavelength of the light beam with λ (nm), ± 0. 5 Χ 10_ 6 Χλ 3 optical system characterized in that it is set within (cm).

1 2. The optical system according to any one of claims 8 to 11, wherein the optical path length in the optical element in the fourth A element group and the light path in the fourth B element group are different. The difference between the optical path length in the academic elements, when the wavelength of the light beam with λ (nra), ± 0. 5 X 10- 6 Χλ 3 optical system characterized in that it is set within (cm) .

13. The optical system according to any one of claims 8 to 12, wherein the optical axis substantially coincides with a crystal axis [100] or a crystal axis optically equivalent to the crystal axis. A fifth element group composed of a plurality of optical elements set as follows,

The fifth element group includes a fifth A element group and a fifth B element group having a positional relationship relatively rotated by a sixth angle about the optical axis,

An optical path length in the optical element of the fifth A element group of a light beam forming an angle within the predetermined range with respect to the optical axis is substantially equal to an optical path length in the optical element of the fifth B element group;

A sum of an optical path length of an optical element in the third element group and an optical path length of an optical element in the fourth element group of a light beam forming the angle within the predetermined range with respect to the optical axis; An optical system, wherein an optical path length in an optical element in a group is set according to a predetermined magnification.

14. In the optical system according to claim 13,

The sum of the optical path lengths in the optical elements in the third element group and the fourth element group is set to be about four times the optical path length in the optical elements in the fifth element group. system.

15. The optical system according to claim 14, wherein

The difference between about four times the optical path length in the optical element in the fifth element group and the sum of the optical path lengths in the optical elements in the third element group and the fourth element group indicates that the wavelength of the light flux is λ (nm ) and the time, ± 2. 7 X 10 one ⁶ X ^λ ³ (cm) optical system, characterized in that you have set within.

16. In the optical system according to any one of claims 13 to 15,

The difference between the optical path length in the optical element in the fifth A element group and the optical path length in the optical element in the fifth B element group is ± 0.5 when the wavelength of the light beam is λ (nm). X 10 — An optical system characterized by being set within ⁶ 6λ ³ (cm).

17. In the optical system according to any one of claims 13 to 16,

Each of the third A element group, the third B element group, the fourth A element group, the fourth B element group, the fifth A element group, and the fifth B element group has at least one optical element. An optical system comprising an element.

18. The optical system according to any one of claims 8 to 17, wherein the angle in the predetermined range is greater than an angle corresponding to 0.6 times the image-side numerical aperture of the optical system. An optical system characterized in that the angle is large and smaller than an angle corresponding to 0.9 times the image-side numerical aperture.

19. In the optical system according to any one of claims 13 to 18,

An optical system, wherein the fifth A element group and the fifth B element group are arranged close to each other along the optical axis.

20. In an optical system including a plurality of optical elements formed of crystals belonging to the cubic system,

A sixth element group and a sixth element group each composed of a plurality of optical elements set such that the optical axis of the optical system and the crystal axis [1 10] or the crystal axis optically equivalent to the crystal axis substantially coincide with each other. 7 element group, 8 element group and 9 element group,

The seventh element group has a predetermined direction around the optical axis with respect to the sixth element group. Has a positional relationship rotated by the seventh angle,

The eighth element group has a positional relationship rotated by the seventh angle in the predetermined direction about the optical axis with respect to the #th element group,

An optical path length in the optical element of the sixth element group of a light beam forming an angle within a predetermined range with respect to the optical axis; and a seventh element group of the light beam forming an angle of the predetermined range with respect to the optical axis. An optical path length in the optical element in the optical element, an optical path length in the optical element in the eighth element group of a light beam forming an angle in the predetermined range with respect to the optical axis, and an angle in the predetermined range with respect to the optical axis. An optical system, wherein the optical path lengths of the light beams in the ninth element group in the optical elements are substantially equal to each other.

21. In the optical system according to claim 20,

The optical path length in the optical element in the sixth element group, the optical path length in the optical element in the seventh element group, the optical path length in the optical element in the eighth element group, and the optical path length in the ninth element group the difference between the two optical path lengths which are selected arbitrarily from the optical path length in the device is, when the example the wavelength of the light beam (nm), ± 0. 5 X 1 0- 6 Χ λ 3 (cm) within An optical system characterized by being set.

22. In the optical system according to claim 20 or 21,

A first element group including a plurality of optical elements set such that the optical axis and the crystal axis [100] or the crystal axis and the optical axis which is optically equivalent to each other substantially coincide with each other;

The first element group includes a first OA element group and a first element group having a positional relationship relatively rotated by an eighth angle about the optical axis, and

The optical path length in the optical element of the first 10A element group and the optical path length in the optical element of the first 10B element group of the light beam forming the angle within the predetermined range with respect to the optical axis are substantially the same. An optical system characterized by being equal.

23. The optical system according to claim 22, wherein

The difference between the optical path length in the optical element in the first OA element group and the optical path length in the optical element in the 10B element group is ± 0 when the wavelength of the light beam is λ (nm). 5 X 10- ⁶ Χλ ³ optical system characterized in that it is set within (cm).

24. The optical system according to claim 22 or 23,

The optical path length in the optical element in the sixth element group, the optical path length in the optical element in the seventh element group, the optical path length in the optical element in the eighth element group, and the optical path length in the ninth element group An optical system characterized in that the sum of the optical path length of the optical element and the optical path length in the optical element in the tenth element group is set according to a predetermined magnification.

25. The optical system according to claim 24,

An optical system wherein the sum of the optical path lengths in the optical elements in the sixth to ninth element groups is set to be about four times the optical path length in the optical elements in the tenth element group. .

26. The optical system according to claim 25, wherein

The difference between about four times the optical path length in the optical element in the tenth element group and the sum of the optical path lengths in the optical elements in the sixth to ninth element groups indicates that the wavelength of the light flux is λ (nm ) is and ^{the, ± 2. 7 X 10- 6} Χλ 3 (cm) optical system, characterized in that you have set within.

27. In the optical system according to any one of claims 20 to 26,

A first element group composed of a plurality of optical elements set so that the optical axis of the optical system and the crystal axis [111] or the crystal axis that is optically equivalent to the crystal axis substantially coincide with each other. Prepared, The eleventh element group includes an eleventh element group and an eleventh element group having a positional relationship relatively rotated by a ninth angle about the optical axis,

The optical path length of the light beam forming the angle within the predetermined range with respect to the optical axis in the optical element in the first 11A element group is substantially equal to the optical path length in the optical element in the 11B element group. An optical system characterized by the above.

28. The optical system according to claim 27, wherein

The difference between the optical path length in the optical element in the first 1A element group and the optical path length in the optical element in the first 1B element group is: ±, where λ (nm) is the wavelength of the light flux. optical system characterized in that it is set within ^{^{0. 5 X 10- 6 Χλ 3 (}} cm).

29. The optical system according to claim 27 or 28,

The total sum of three times the sum of the optical path lengths in the optical elements in the sixth to ninth element groups and eight times the optical path length in the optical elements in the eleventh element group is the tenth element group. An optical system, wherein the optical path length is set to about 12 times the optical path length in the optical element in the group.

30. The optical system according to claim 29,

The sum of the optical path lengths in the optical elements in the sixth to ninth element groups is L 69 (cm), and the optical path length in the optical elements in the tenth element group is L 10 (cm). When the optical path length in the optical element in the 11 element group is L 11 (cm) and the wavelength of the light beam is λ (nm),

I 3 XL 69- 12 XL 10 + 8 XL 1 1 | ≤ 8. 0X 10 - 6 Χλ 3

An optical system characterized by satisfying the following conditions:

31. The optical system according to any one of claims 20 to 30,

The angle in the predetermined range is an angle corresponding to 0.6 times the image-side numerical aperture of the optical system. An optical system characterized in that the angle is larger than an angle corresponding to 0.9 times the image-side numerical aperture.

32. In the optical system according to any one of claims 20 to 31,

An optical system, wherein each of the sixth to tenth element groups has at least one optical element.

33. The optical system according to any one of claims 1 to 32, wherein the crystal is a calcium fluoride crystal or a barium fluoride crystal.

3 4. An illumination system for illuminating the mask,

The optical system according to any one of claims 1 to 33 for forming an image of a pattern formed on the mask on a photosensitive substrate. Exposure equipment.

35. An exposure step of exposing the pattern of the mask to the photosensitive substrate using the exposure apparatus according to claim 34,

A developing step of developing the photosensitive substrate exposed in the exposing step.