JPH1184249A - Exposure device and exposure method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure device provided with a reduction stepper optical system, constituted so that a luminous flux on an axis may be preferably used in a cata-dioptric system, hardly causing the deterioration of resolution and capable of arranging a diaphragm. SOLUTION: A reticle 1 is illuminated from an illumination optical system and a reduced pattern image on the reticle 1 is transferred onto a wafer 5 through a projection optical system. The projection optical system is provided with a 1st lens group G1 with a negative refractive power and for enlarging the luminous flux from the reticle 1, a half mirror 2 as a separating means for reflecting the luminous flux from the 1st lens group G1 , a concave reflection mirror 4 for converging the luminous flux from the half mirror 2 and returning the flux to the half mirror 2, a 3rd lens group G3 with a positive refractive power and for converging the luminous flux which is transmitted through the half mirror 3 after being returned to the half mirror 2 on the wafer 5 and the diaphragm which is arranged between the half mirror 2 and the wafer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method for manufacturing, for example, a semiconductor device, and more particularly, to a catadioptric reduction projection optical system for reducing and projecting a pattern which is larger than a pattern of an actual device. The present invention relates to an exposure apparatus provided.

[0002]

2. Description of the Related Art Semiconductor integrated circuits are becoming finer and finer, and an exposure apparatus for printing the pattern is required to have a higher resolution. In order to satisfy this requirement, it is necessary to shorten the wavelength of the light source and increase the numerical aperture (NA) of the optical system. However, as the wavelength becomes shorter, glass materials that can be used practically for light absorption are limited. When the wavelength is 300 nm or less, only synthetic quartz and fluorite (calcium fluoride) can be practically used. Fluorite has a poor temperature characteristic and cannot be used in large quantities. Therefore, it is extremely difficult to make a projection lens using only a refraction system. Further, it is difficult to make a projection optical system having a large numerical aperture only with a reflection system due to the difficulty of correcting aberrations.

Therefore, various techniques have been proposed for forming a projection optical system by combining a reflection system and a refraction system. One example is a ring field optical system as disclosed in JP-A-63-163319. In this optical system, an off-axis light beam is used so that incident light and reflected light do not interfere with each other, and only the off-axis orbicular zone is exposed.

Further, as another example, a projection exposure apparatus including a catadioptric system for projecting an image of a reticle (mask) collectively with an on-axis light beam by disposing a beam splitter in a projection optical system has been proposed. Tokiko Sho 51-271
No. 16 and JP-A-2-66510.

FIG. 5 schematically shows an optical system disclosed in Japanese Patent Application Laid-Open No. 2-66510. In FIG. 5, a light beam from a reticle 21 on which a pattern to be reduced and transferred is drawn is a lens group 2 having a positive refractive power.
The light is converted into a substantially parallel light beam by 2 and irradiates a prism type beam splitter (beam splitter cube) 23. The joining surface 23a of the beam splitter 23
Are transmitted through the correction lens group 24 having a negative refractive power.
And is reflected by the concave reflecting mirror 25. The light beam reflected by the concave reflecting mirror 25 passes through the correction lens group 24 again, is reflected by the joint surface 23a of the beam splitter 23, and is then focused on the wafer 27 by the lens group 26 having a positive refractive power. A reduced image of the reticle pattern is formed on the wafer 27. There is also disclosed an example in which a half mirror made of a plane parallel plate is used instead of the prism type beam splitter 23.

[0006]

However, there is an inconvenience that it is difficult to increase the numerical aperture in the ring field optical system in the prior art. Further, in the configuration disclosed in Japanese Patent Publication No. 51-27116, the magnification of the whole system is the same, and as a next-generation semiconductor manufacturing exposure apparatus requiring a higher resolution, it is completely usable. is not.

Further, in the projection optical system disclosed in Japanese Patent Application Laid-Open No. 2-66510, in the optical system shown in FIG. 5, the stop is located at a position overlapping with the beam splitter 23 or the half mirror. There was an inconvenience that could not be placed. As a result, the resolving power deteriorates, the unevenness of the light amount cannot be corrected, and the telecentricity of the wafer 27 cannot be ensured, which is not practical as a semiconductor exposure apparatus.

In view of the above, the present invention provides an exposure apparatus having a configuration in which a catadioptric system preferably uses an on-axis light beam, and which has a reduction projection optical system in which a resolving power is not deteriorated and a stop can be arranged. The purpose is to: Still another object of the present invention is to provide an exposure method using such an exposure apparatus.

[0009]

According to an exposure apparatus of the present invention, as shown in FIG. 1, for example, an illumination optical system for illuminating a reticle (1) disposed on a first surface and a reduced image of a pattern of the reticle are formed. A projection optical system for transferring to a wafer (5) disposed on the second surface, wherein the projection optical system is disposed in an optical path between the first surface and the second surface. The first lens group G ₁ and the first lens group G ₁
And it is disposed in an optical path between the second surface, and separation means for transmitting or reflecting the light beam from the first lens group G ₁ (2), between the separating means and its second surface A concave reflecting mirror (4) arranged in the optical path for returning the light beam from the separating means (2) to the separating means again; and an optical path arranged between the concave reflecting mirror and the second surface. Focusing the light from the concave reflecting mirror (4) via the separating means (2) to form a reduced image of the pattern of the reticle (1) on the first surface on the wafer (5) on the second surface. a positive third lens group G ₃ to be formed, the separating means (2) and the aperture (6) disposed between the second surface, and has a.

In this case, the first lens group G is provided in the optical path between the separating means (2) and the concave reflecting mirror (4).
It is preferred _that the _first and second lens group G ₂ for expanding the light beam through the separating means (2) is arranged. Also,
It is preferred that the light beam directed from the separation means (2) to the third lens group G ₃ is substantially parallel beam.

Further, the diaphragm (6) is arranged between the separating means and (2) and its third lens group G ₃ as an example. Further, the diaphragm (6) may be disposed on the third in the lens group G ₃ as another example. In addition, the projection optical system uses at least an axial light beam for the wafer (5).
It is preferable to form a reduced image of the pattern thereon.

It is preferable that a quarter-wave plate (3) is disposed in the optical path between the separating means (2) and the concave reflecting mirror (4). The quarter wave plate (3)
It is preferable to use a uniaxial crystal (for example, quartz) having a thickness of 100 μm or less. In these cases, the concave reflecting mirror (4)
Is preferably set in the range of 17 to 25 times the diameter of the exposure area (image circle) on the second surface. Further, it is preferable that the inclination of the marginal ray from the on-axis object point passing through the separating means (2) with respect to the optical axis is 0.1 degrees or less.

Further, it is preferable that the inclination of the off-axis principal ray incident on the concave reflecting mirror (4) with respect to the optical axis is 4 degrees or less. It is preferable that the illumination optical system supplies a linearly polarized light beam. Next, an exposure method according to the present invention is an exposure method using the exposure apparatus according to the present invention, wherein the reticle is placed in a state where the projection optical system is telecentric toward the wafer (5) by the stop (6). The reduced image of the pattern (1) is transferred onto the wafer (5) via the projection optical system. Thereby, even if the height of the wafer changes to a certain extent, the projection magnification does not change.

[0014]

According to the present invention, an on-axis light beam is used for exposing a wide area at a time in a configuration combining a reflection system and a refraction system. Further, since the reflection system has no chromatic aberration, most of the refractive power of the entire system is given to the concave reflecting mirror (4) to suppress the occurrence of chromatic aberration. Then, separation of the incident light and the reflected light is performed by the separation means (2).

The light beam transmitted through the separating means (2) is a substantially parallel light beam. Generally, an aperture stop is placed at a position where light emitted from an object point becomes a substantially parallel light beam. Therefore, according to the configuration of the present invention, the separating means (2) and the second
An effective stop (5) can be arranged between the surface (5).

Further, the separating means (2) and the concave reflecting mirror (4)
Negative when the second lens group G ₂ is arranged in having a refractive power, a third chromatic aberration of the lens group G ₃ having a positive refractive power by the second lens group G ₂ for extending the light beam between the The correction can be performed, and the spherical aberration of the concave reflecting mirror (4) can be corrected more favorably. Further, as described above, the second lens group G ₂ of the negative refractive power has an important role closer to parallel light a light beam transmitted through the separation means (2).

Next, the radius of curvature of the concave reflecting mirror (4) is the second radius.
1 of the diameter of the exposure area (image circle) on the surface (5)
The reason why 7 to 25 times is preferable will be described. In the concave reflecting mirror, a certain reduction magnification can be achieved by the convergence function, and the Petzval sum, astigmatism, and distortion are affected. Therefore, the first lens group G ₁ ,
It is possible to maintain good aberration balance with the refracting system consisting of the second lens group G ₂ and the third lens group G _3.
That is, when the radius of curvature of the concave reflecting mirror (4) is smaller than 17 times the diameter of the image circle of the second surface (5), it is advantageous for correcting chromatic aberration, but the Petzval sum increases in the positive direction. As a result, astigmatism and distortion also increase.

The reason is that when the radius of curvature of the concave reflecting mirror decreases and the refractive power increases, the spherical aberration caused by the concave reflecting mirror (4) increases, but the light transmitted through the separating means (2) is converted into a parallel light. in order, the refractive power of the negative second lens group G ₂ becomes large, for correction of spherical aberration becomes necessary to increase the positive refractive power of the third lens group G _3. However, since the third lens group G ₃ is disposed at a position closer to the second surface (5) as the image plane, a large refractive power than the negative refractive power of the second lens group G ₂ is for aberration correction Is required, and the Petzval sum increases remarkably. Therefore, in order to better correct various aberrations, it is desirable that the radius of curvature of the concave reflecting mirror (4) is about 17 times or more the diameter of the image circle of the reduced image.

Conversely, when the radius of curvature of the concave reflecting mirror (4) is larger than 25 times the diameter of the image circle of the reduced image, it is advantageous for correction of astigmatism and distortion. It is not practical because it becomes difficult to obtain a desired reduction magnification and chromatic aberration is insufficiently corrected.

Next, the reason why the inclination of the marginal ray (so-called land ray) from the on-axis object point passing through the separating means (2) with respect to the optical axis is preferably 0.1 degrees or less will be described. As described above, the closer the light beam transmitted through the separation means (2) is to a parallel light beam, the more the occurrence of aberration due to the separation means (2) is suppressed, and the easier it is to arrange the stop. In particular, when the maximum value of the deviation from the parallel light beam is 0.1 degrees or less, the amount of aberration is small and practical.

The reason why the inclination of the off-axis chief ray entering the concave reflecting mirror (4) with respect to the optical axis is preferably 4 degrees or less will be described. That is, if the inclination of the off-axis principal ray is not limited in this way, astigmatism and the like at the concave reflecting mirror (4) become too large. Therefore, the inclination with respect to the optical axis is limited to 4 degrees or less, thereby suppressing the occurrence of aberration caused by the concave reflecting mirror (4), thereby improving the imaging performance as a whole.

The operation and effect when the quarter-wave plate (3) is arranged between the separating means (2) and the concave reflecting mirror (4) will be described. In general, a dielectric film used as a semi-transmissive surface of the separating means has strong polarization characteristics, and a light flux (s-polarized light) polarized, for example, perpendicular to the plane of FIG. 1 on the semi-permeable surface (2a) of the separating means (2). It is assumed that a light beam (p-polarized light) that is easily reflected and polarized parallel to the paper surface of FIG. 1 is easily transmitted. In this case, the s-polarized light component reflected by the semi-transmissive surface (2a) passes through the quarter-wave plate (3) to become circularly polarized light, and the light beam of this circularly polarized light is reflected by the concave reflecting mirror (4). It becomes circularly polarized light in the opposite direction. The reflected light of the counterclockwise circularly polarized light becomes the p-polarized light by transmitting through the quarter-wave plate (3), and most of the light beam of the p-polarized light transmits through the semi-transmissive surface (2a) of the separating means (2). To the second surface (5). Therefore, the quarter wavelength plate (3) not only can reduce the loss of the light amount in the separation means (2), but also can reduce the flare since it is difficult for extra reflected light to return to the second surface (5). be able to.

Further, it is desirable to use a thin uniaxial crystal (for example, quartz) as the quarter-wave plate (3). The reason is that if the light beam transmitted through the quarter-wave plate deviates from the parallel light beam, astigmatism occurs for the extraordinary ray. This astigmatism cannot be corrected by a method in which two crystals are bonded to each other by rotating the optical axis by 90 ° with each other, as is usually done with a wavelength plate. That is, both the ordinary ray and the extraordinary ray cause astigmatism.

Assuming that the amount of astigmatism is represented by the wavefront aberration W, (n _o -n _e ) is the difference between the refractive indexes of the ordinary ray and the extraordinary ray, d is the thickness of the crystal, and θ is the fraction of the parallel ray. The wavefront aberration W is expressed by the following equation, assuming a shift, ie, a divergence (or convergence) angle of the light beam. W = (n _o -n _e) the d [theta] ^2/2 for example quarter-wave plate when configuring in crystal, (n _o
-N _e) = 0.01, divergence of the light beam a (focused) state theta = 15 to °. Assuming that the used wavelength is λ, it is preferable to maintain the wavefront aberration W at a quarter wavelength, that is, λ / 4 or less, in order to maintain sufficiently good imaging performance. For that purpose, the wavelength λ is set to, for example, 248 nm, and from the above equation, d <100 μm.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exposure apparatus according to the present invention will be described below with reference to FIGS. In this example, the present invention is applied to an exposure apparatus having a wavelength of 248 nm and a reduction ratio of 1/5 for semiconductor manufacturing. FIG. 1 shows a schematic configuration of a catadioptric reduction projection optical system used as a projection optical system of the exposure apparatus of the present embodiment.
In the figure, reference numeral 1 denotes a reticle on which a pattern for an integrated circuit is formed. A first lens group G ₁ having negative or positive refracting power and a half mirror 2 which is 45 ° inclined with respect to the optical axis as a separating means are sequentially arranged on an optical axis perpendicular to the reticle 1. Then, in the direction in which the light from the first lens group G ₁ is reflected by the semi-transparent surface 2 a of the half mirror 2,
Wave plate 3, and positioning a second lens group G ₂ and the concave reflecting mirror 4 having negative refractive power, in order to light reflected by the concave reflecting mirror 4 in a direction passing through at HanTorumen 2a of the half mirror 2, a diaphragm 6 ,
Disposing the third lens group G ₃ and the wafer 5 having a positive refractive power. Incidentally, aperture 6 can also be placed in the third lens group G _3, for example.

In this case, if the light transmitted through the half mirror 2 is slightly deviated from the parallel light, aberrations such as astigmatism occur. Therefore, when the demand for aberration is strict, first, the light beam transmitted through the half mirror 2 is made close to a parallel light beam to reduce coma aberration sufficiently. Then, between the half mirror 2 and the third lens group G ₃ , a parallel plane plate having the same thickness as the half mirror 2 is disposed at an angle of 45 ° with respect to the optical axis, and its direction is set to the direction of the half mirror 2. Rotate 90 °. Thereby, astigmatism is corrected. Also, 3
When two parallel flat plates are used, astigmatism and coma aberration can be corrected even when the light beam transmitted through the half mirror 2 deviates from the parallel light beam.

Then, the reticle 1 is illuminated by an illumination optical system (not shown), and a light beam emitted from the reticle 1 is
The light is diffused or converged by the first lens group G1 and is incident on the half mirror 2. The half mirror 2 the light beam reflected by the HanTorumen 2a through a 1/4 second lens group G ₂ wave plate 3 and the negative refractive power to be incident on the concave reflecting mirror 4. The radius of curvature of the concave reflecting mirror 4 is about 400 mm. The light beam reflected by the concave reflecting mirror 4 is incident on the half mirror 2 again through the second lens group G ₂ and the 波長 wavelength plate 3 while being converged, and transmitted through the semi-transparent surface 2 a of the half mirror 2. It focused on the wafer 5 by the third lens group G ₃ in a light flux positive refractive power. Thus, a reduced image of the pattern on the reticle 1 is formed on the wafer 5.

In this embodiment, the half mirror 2 and the third lens group G
_A stop 6 is arranged between the stop ₃ and the stop _3, and the stop 6 ensures telecentricity on the wafer 5 side.

It is efficient to use a light beam (s-polarized light) polarized perpendicularly to the plane of FIG. 1 as the illumination light.
Ordinary randomly polarized illumination light may be used. In either case, most of the s-polarized light is reflected by the semi-transmissive surface 2a due to the polarization characteristics of the half mirror 2, and this reflected light is further transmitted through the quarter wavelength plate 3 to become circularly polarized light. This circularly polarized light beam is reflected by the concave reflecting mirror 4 and becomes reversely circularly polarized light. When the reversely circularly polarized light beam passes through the quarter-wave plate 3 again, the polarization state is changed to the plane of FIG. It becomes parallel linearly polarized light. Due to the polarization characteristics of the half mirror 2, most of the light beam polarized in a direction parallel to the paper of FIG. 1 passes through the semi-transmissive surface 2a and travels toward the wafer 5. This makes the half mirror 2
, The return light to the reticle 1 is reduced, so that the effective use of the light flux and the reduction of the flare are achieved.

Further, the use of a uniaxial crystal (for example, quartz) having a small thickness as the quarter-wave plate 6 prevents occurrence of astigmatism. Specifically, assuming that quartz is used, the wavelength λ used is 248 nm, and to suppress the wavefront aberration due to the quarter-wave plate 6 to λ / 4 or less, the thickness of the quarter-wave plate 6 is set to 100 μm or less. There is a need to.

When the semi-transmissive surface 2a of the half mirror 2 is positively provided with a polarization characteristic such as a polarizing beam splitter, the reflectance and the transmittance are further improved by combination with the quarter-wave plate 6. be able to. However, even with a normal half mirror, for example, since the dielectric film has strong polarization characteristics, the reflectance and the transmittance can be improved by combination with the quarter-wave plate 3.

Hereinafter, a specific configuration example of the optical system of FIG. 1 will be described. In order to represent the shape and interval of the lens in the following embodiments, the reticle 1 is used as the first surface, and the surface through which the light emitted from the reticle 1 passes before reaching the wafer 5 is sequentially referred to as an i-th surface (i = 2). , 3, ‥‥). The sign of the radius of curvature r _i of the i-th surface is positive when the reticle 1 is convex with respect to the reticle 1 between the reticle 1 and the half mirror 2, and the concave reflection is between the concave reflecting mirror 4 and the wafer 5. The case of convex with respect to the mirror 4 is positive. The sign of the surface distance d _i between the i-th surface and the (i + 1) surface, a half mirror 2
Is negative in the region where the reflected light from the semi-transparent surface 2a passes to the concave reflecting mirror 4, and positive in other regions. As glass materials, CaF ₂ represents fluorite and SiO ₂ represents quartz glass. Reference wavelengths for use of quartz glass and fluorite (248
The refractive index for (nm) is as follows. Quartz glass: 1.85555 Fluorite: 1.46799

FIG. 2 shows a lens configuration diagram of the present embodiment.
As shown in FIG. 2, the first lens group G₁Is the side of reticle 1
Negative meniscus lens with convex surface facing reticle 1 side
Z L ₁₁, Biconvex lens L₁₂, Biconvex lens L₁₃, Biconcave lens
L₁₄And biconcave lens L_FifteenAre arranged and configured. Also book
In the example, the second lens group G_Two Indicates the convex surface facing the concave reflecting mirror 4
Negative meniscus lens L₂₀Composed of only Furthermore,
3 lens group G_Three Are biconvex lasers in order from the half mirror 2 side.
L₃₁Menisca with convex surface facing half mirror 2
SLENS L₃₂, With the convex surface facing the half mirror 2 side
Sukas lens L ₃₃, Biconcave lens L₃₄, Biconvex lens L₃₅,
Positive meniscus lens L with convex surface facing half mirror 2
₃₆Meniscus lens with convex surface facing half mirror 2
Z L₃₇Menisca with convex surface facing half mirror 2
SLENS L₃₈Are arranged and configured. However, 1 in FIG.
Since the 波長 wavelength plate 3 is thin and can be ignored, it is omitted in FIG.
Abbreviated. Radius of curvature r in the embodiment of FIG._i ,
Surface distance d_i And the glass materials are shown in Table 1 below.

[0034]

TABLE 1 i r _i d _i glass material i r _i d _i glass material 1 ∞ 160.328 21 -3775.726 8.500 2 226.290 20.000 CaF 2 22 132.037 20.000 CaF 2 3 112.740 12.000 23 386.661 80.662 4 186.919 28.000 SiO 2 24 90.751 16.727 CaF 2 5 -267.368 48.845 25 1020.086 4.600 6 203.766 30.000 SiO ₂ 26 -378.373 11.000 SiO ₂ 7 -153.468 2.000 27 51.955 0.400 8 -235.200 15.000 CaF ₂ 28 51.881 19.000 CaF ₂ 9 105.304 45.805 29 -402.490 0.200 10 -154.442 18.000 CaF ₂ 30 66.487 _{11.242 CaF 2 11 661.852 128.795 31 383.884} 1.000 12 ∞ -85.500 32 580.000 10.000 SiO 2 13 156.613 -24.000 SiO 2 33 39.378 1.600 14 303.843 -34.000 34 43.274 13.000 CaF 2 15 425.644 34.000 35 514.049 14.381 16 303.843 24.000 SiO 2 17 156.613 85.500 18 ∞ 20.000 SiO ₂ 19 ∞ 60.000 20 296.017 20.000 CaF ₂

In this embodiment, the reduction ratio is 1/5,
The numerical aperture is 0.45, and the diameter d of the effective exposure area (image circle) on the wafer 5 is 20 mm. The radius of curvature r of the concave reflecting mirror 4 is 425.664 mm, and the radius of curvature r is about 21.3 times the diameter d. Further, the maximum value of the inclination of the marginal ray (land ray) from the on-axis object point entering the concave reflecting mirror 4 with respect to the optical axis is 7.85 °, with respect to the optical axis of the off-axis principal ray entering the concave reflecting mirror 4. The maximum value of the slope is 2.41 °. Incidentally, the maximum value of the inclination of the land ray emitted from the concave reflecting mirror 4 with respect to the optical axis is 0.0
14 ゜. Furthermore, the inclination of the land ray transmitted through the half mirror 2 with respect to the optical axis is 0.001 ° or less, and in this example, the light beam transmitted through the half mirror 2 can be regarded as a substantially parallel light beam.

The wavelength used in the embodiment of FIG. 2 is 248.4.
FIG. 3 shows a longitudinal aberration diagram in the case of nm, and FIG. 4 shows a lateral aberration diagram. From these aberration diagrams, in this example, the numerical aperture is 0.
It can be seen that various aberrations are satisfactorily corrected within a wide image circle area, despite being as large as 45. Although not shown, chromatic aberration also has a wavelength λ of 248 nm to 2 nm.
It is well corrected between 49 nm.

The present invention is not limited to the above-described embodiment, but can take various configurations without departing from the spirit of the present invention.

[0038]

According to the exposure apparatus of the present invention, there is provided an advantage that the reticle pattern can be transferred onto the wafer at a high resolution because the exposure apparatus is provided with a reduced projection optical system capable of disposing a stop without deteriorating the resolution. When the first lens group and the second lens group for expanding the luminous flux via the separating means are arranged in the optical path between the separating means and the concave reflecting mirror, the second lens group is used for the second lens group. The chromatic aberration of the three lens groups can be corrected, and the spherical aberration of the concave reflecting mirror can be corrected more favorably.

When the light flux from the separation means to the third lens group is substantially a parallel light flux, an effective stop can be arranged at the position where the light flux becomes the parallel light flux. Further, the projection optical system is configured to use the on-axis light beam by the catadioptric system when forming a reduced image of the reticle pattern on the wafer using at least the on-axis light beam, so that the resolving power does not deteriorate. In addition, a reduction projection optical system capable of disposing a stop can be provided, so that a pattern with higher resolution can be transferred onto the wafer.

When the radius of curvature of the concave reflecting mirror is 17 to 25 times the diameter of the exposure area on the second surface, astigmatism and distortion can be easily corrected and a predetermined reduction magnification can be easily obtained. There are advantages. Further, when the inclination of the marginal ray from the on-axis object point passing through the separating means with respect to the optical axis is 0.1 ° or less, the coma aberration and astigmatism due to the separating means become sufficiently small. Further, when the inclination of the off-axis chief ray incident on the concave reflecting mirror with respect to the optical axis is limited to 4 ° or less, the amount of aberration such as astigmatism can be suppressed within a predetermined range, and the reflection by the separating means can be suppressed. There is an advantage that variation in transmittance and transmittance can be suppressed.

The distance between the separating means and the concave reflecting mirror is 1 /
When a four-wavelength plate is provided, the transmittance of the separating means can be increased, and flare can be reduced.
In particular, when the quarter-wave plate is formed of a uniaxial crystal having a thickness of 100 μm or less, there is an advantage that deterioration of astigmatism is negligible. Further, when the illumination optical system supplies a linearly polarized light beam, there is an advantage that illumination efficiency is good. Next, according to the exposure method of the present invention, since the wafer side is telecentric, the magnification does not change even if the height of the wafer changes to some extent, so that it is practical.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a basic configuration of a projection optical system provided in an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a lens configuration diagram showing a specific configuration of the optical system of FIG.

FIG. 3 is a longitudinal aberration diagram of the embodiment of FIG.

FIG. 4 is a lateral aberration diagram of the embodiment of FIG.

FIG. 5 is a cross-sectional view showing a basic configuration of a conventional catadioptric reduction projection optical system.

[Explanation of symbols]

1 ... reticle, G ₁ ... the first lens group, a half mirror as 2 ... separator, 3 ... 1/4-wavelength plate, G ₂ ... the second lens group, 4 ... concave reflector, G ₃ ... third lens group 5, wafer

Claims (9)

[Claims] 1. An exposure apparatus comprising: an illumination optical system that illuminates a reticle disposed on a first surface; and a projection optical system that transfers a reduced image of a pattern of the reticle onto a wafer disposed on a second surface. A first lens group disposed in an optical path between the first surface and the second surface; and a projection optical system disposed in an optical path between the first lens group and the second surface. And separating means for transmitting or reflecting the light beam from the first lens group, and disposed in an optical path between the separating means and the second surface,
A concave reflecting mirror for returning the light beam from the separating unit to the separating unit again, disposed in an optical path between the concave reflecting mirror and the second surface, and provided from the concave reflecting mirror via the separating unit. A positive third lens group that focuses light to form a reduced image of the pattern of the reticle on the first surface on the wafer on the second surface; and is disposed between the separation unit and the second surface. Aperture and
An exposure apparatus comprising: 2. The optical system according to claim 1, wherein said first lens group and a second lens group for expanding a light beam passing through said separating means are arranged in an optical path between said separating means and said concave reflecting mirror. The exposure apparatus according to claim 1, wherein 3. The exposure apparatus according to claim 1, wherein a light beam traveling from the separation unit to the third lens group is a substantially parallel light beam. 4. The apparatus according to claim 1, wherein said stop is disposed between said separating means and said third lens group.
The exposure apparatus according to claim 1. 5. The exposure apparatus according to claim 1, wherein the stop is disposed in the third lens group. 6. The exposure apparatus according to claim 1, wherein the projection optical system forms a reduced image of the pattern on the wafer using at least an on-axis light beam. . 7. An exposure apparatus according to claim 1, wherein a quarter-wave plate is disposed in an optical path between said separating means and said concave reflecting mirror. 8. The exposure apparatus according to claim 7, wherein the illumination optical system supplies a linearly polarized light beam. 9. An exposure method using the exposure apparatus according to claim 1, wherein the pattern of the reticle is set in a state where the projection optical system is telecentric toward the wafer by the stop. An exposure method, wherein the reduced image of (1) is transferred onto the wafer via the projection optical system.