JP2003241099A - Catadioptric projection optical system, and projection exposure method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use a luminous flux separation optical system smaller in size than the conventional polarizing beam splitter and to secure an optical path leading to an image surface from a concave reflection mirror to be long. <P>SOLUTION: Luminous flux from an object surface 1 is made incident on the polarizing beam splitter 6 through a 1st converging group G<SB>1</SB>, the luminous flux reflected by the splitter 6 is reflected by the concave reflection mirror M<SB>2</SB>and forms the image of a pattern on the surface 1 inside the reflection mirror 2. After the luminous flux from the image of the pattern is transmitted through the splitter 6, it forms the image of the pattern on the image surface 5 through a 3rd converging group G<SB>3</SB>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system for equal-magnification or reduction projection of a projection exposure apparatus such as a stepper used when manufacturing a semiconductor device or a liquid crystal display device in a photolithography process. The present invention relates to a catadioptric projection optical system suitable for application, and particularly, by using a catoptric system as an element of an optical system, a catadioptric projection of 1/4 to 1/5 times having a resolution of a submicron unit in an ultraviolet wavelength range Regarding optics.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device, a liquid crystal display device or the like by a photolithography process, a pattern image of a reticle (or a photomask or the like) is reduced to, for example, about 1/4 to 1/5 through a projection optical system. Then, a projection exposure apparatus for exposing a wafer (or a glass plate or the like) coated with a photoresist or the like is used. As a projection exposure apparatus, conventionally, a batch exposure method such as a stepper has been mainly used.

Recently, as the degree of integration of semiconductor elements and the like has further improved, the resolving power required for a projection optical system used in a projection exposure apparatus has also increased. In order to meet this demand, it is necessary to shorten the wavelength of the illumination light for exposure (exposure wavelength) or increase the numerical aperture NA of the projection optical system. However, as the exposure wavelength becomes shorter, the optical glass that can be used practically is limited due to absorption of illumination light. Especially, when the exposure wavelength is 300 nm or less, the only practical glass materials are synthetic quartz and fluorite.

Since the Abbe numbers of the two are not far enough from each other to correct chromatic aberration, it is extremely difficult to correct chromatic aberration if the projection optical system is composed of only the refracting optical system when the exposure wavelength is 300 nm or less. Becomes Further, fluorite has a poor refractive index change due to temperature change, so-called temperature characteristics,
Also, because it has many problems in lens polishing,
It cannot be used for many parts. Therefore, it is extremely difficult to construct a projection optical system having a required resolving power with only a refracting system.

On the other hand, it has been attempted to configure the projection optical system with only the reflection system, but in this case, the projection optical system becomes large and it is necessary to make the reflecting surface aspheric. However, it is extremely difficult to manufacture a large, highly accurate aspherical surface. Therefore, various techniques have been proposed for constructing a reduction projection optical system by a so-called catadioptric optical system in which a reflective system and a refractive system made of optical glass that withstands the exposure wavelength used are combined. As an example thereof, there is a reduction projection exposure apparatus having a beam splitter made of a cubic prism and having a catadioptric projection optical system that collectively projects an image of a reticle by using a light beam in the vicinity of an axis. 6
No. 6510, Japanese Patent Laid-Open No. 3-282527, US Pat. No. 5,089,913, or Japanese Patent Laid-Open No. 5-7.
It is disclosed in Japanese Patent No. 2478.

FIG. 10 shows such a conventional catadioptric projection optical system. In FIG. 10, the pattern of the object plane 1 is illuminated by illumination light from an illumination optical system (not shown). Then, the light beam from the pattern on the object plane 1 enters the cubic polarization beam splitter (PBS) 2 through the first convergence group G ₁ having the focal length f ₁ and is reflected by the beam splitter surface 2 a of the polarization beam splitter 2. The generated S-polarized component is incident on the concave reflecting mirror M ₂ as circularly polarized light via the quarter-wave plate 3. The light flux reflected by the concave reflecting mirror M ₂ returns to the quarter-wave plate 3 as the opposite circularly polarized light, and 1
The light flux that has passed through the quarter-wave plate 3 and becomes P-polarized light passes through the polarization beam splitter 2 and then has the third focal length f ₃ .
An image of the pattern on the object plane 1 is formed on the image plane 5 via the convergence group G ₃ . In this case, the polarization beam splitter 2,
The quarter-wave plate 3 and the concave reflecting mirror M ₂ constitute the second convergent group G ₂ having the focal length f ₂ . In addition, the concave reflecting mirror M ₂
In order to prevent flare from occurring due to repeated reflection of the light flux between the image plane 5 and the image plane 5, the polarization beam splitter 2
And the quarter-wave plate 3 are used to block the unnecessary reflected light by utilizing the fluctuation of the polarization angle of the unnecessary reflected light.

[0007]

[SUMMARY OF THE INVENTION A conventional catadioptric projection optical system as described above, by using the polarization beam splitter 2, the reflected light beam incident on the concave reflecting mirror M ₂ and its concave reflecting mirror M ₂ It was separated from the luminous flux. However, conventionally, since the light flux reflected by the concave reflecting mirror M ₂ directly forms an image of the pattern on the object plane 1 on the image surface 5, the concave reflecting mirror M ₂ causes the polarization beam splitter 2 to move.
The diameter of the light beam going to was large, and the polarization beam splitter 2 was large.

Therefore, the image forming characteristics are deteriorated due to non-uniformity of the reflectance distribution on the beam splitter surface 2a in the polarization beam splitter 2, phase change of illumination light, absorption of illumination light in the beam splitter, and the like. There was an inconvenience. Further, since the cube-shaped prism forming the polarization beam splitter 2 is large, it is very difficult to manufacture a glass material for the beam splitter and maintain the uniformity of its optical characteristics.

Further, conventionally, as one method for increasing the depth of focus and increasing the resolution, there has been proposed a phase shift method for shifting the phase of a predetermined portion in a reticle pattern from other portions (Japanese Patent Publication No. 62-62-62). 50811).
In order to further enhance the effect of this phase shift method, it is desirable to make the coherence factor (σ value), which is the ratio of the numerical aperture of the illumination optical system and the numerical aperture of the imaging optical system, variable.
As described above, in order to make the σ value variable, it is necessary to install a variable aperture stop in the illumination optical system or the projection optical system (or both). However, the catadioptric projection optical system using the conventional polarization beam splitter 2 is required. However, there is an inconvenience that it is difficult to change the σ value or the variable range is narrow because an effective diaphragm installation portion cannot be taken anywhere.

Further, in the conventional catadioptric projection optical system, since the optical path of the illumination light reflected by the concave reflecting mirror M ₂ to the wafer (image surface 5) cannot be taken long due to the relation of the reduction magnification, this optical path is not provided. There is a disadvantage in that the number of refracting lenses to be arranged cannot be increased and it is difficult to obtain sufficient imaging performance. Therefore, there is a disadvantage that the distance between the end surface of the refraction lens on the wafer side and the wafer, that is, the working distance (working distance) cannot be long.

Recently, apart from the projection exposure apparatus of the batch exposure system, a slit scan system or a step-and-scan system in which a reticle and a wafer are relatively scanned with respect to a projection optical system to perform exposure. The scanning exposure method of is also used. However, even when these methods are used, the conventional catadioptric projection optical system still has the above-mentioned problems.

In view of the above point, the present invention can use a light beam splitting optical system which is smaller than the conventional polarization beam splitter,
Another object of the present invention is to provide a catadioptric projection optical system that has a long optical path from the concave reflecting mirror to the image plane and has excellent imaging performance. It is another object of the present invention to provide a catadioptric projection optical system having a space in which an aperture stop can be arranged after miniaturizing a light beam splitting optical system such as a polarization beam splitter.

A further object of the present invention is to provide a catadioptric projection optical system which can be applied to a scanning exposure type projection exposure apparatus while using a small light beam separation optical system.
Another object of the present invention is to provide a projection exposure method and apparatus using those catadioptric projection optical systems.

[0014]

The invention according to claim 1 of the present application (hereinafter, "first catadioptric projection optical system according to the present invention")
Say ) Forms an intermediate image (6) of the pattern of the first surface in an optical system that projects the image of the pattern of the first surface (1) onto the second surface (5) as shown in FIG. 1, for example. It has a first imaging optical system (G ₁ , G ₂ ) and a second imaging optical system (G ₃ ) for forming an image of an intermediate image on the second surface thereof.

The first image forming optical system includes a first group (G ₁ ) having a positive refracting power, which contains a refracting lens component and converges a light beam from the pattern on the first surface, and the light of the first group. A prism type beam splitter (6) for separating a part of the light beam from the first group by a beam splitter surface (6a) arranged obliquely to the axis, and a light beam separated by this prism type beam splitter A prism type beam splitter (6) including a concave reflecting mirror (M ₂ )
It is composed of a second group (G ₂ ) having a positive refractive power that forms an intermediate image (7) of the pattern in the vicinity, and a part of the light flux converged by the second group (G ₂ ) is a prism. The beam is split by the beam splitter (6) and guided to the second imaging optical system (G ₃ ).

In this case, the intermediate image (7) of the pattern
Formed inside the prismatic beam splitter (7)
It is desirable to be done. In addition, as shown in FIG.
Reflector (M₂) And the second surface (5)
Beam splitter to prevent flare
A polarization beam splitter is used as (6) and
Optical beam splitter and concave reflector (M ₂) And 1
It is desirable to dispose a quarter wave plate (3).

Further, it is desirable that at least the image plane (5) side is telecentric. Next, another invention (hereinafter, referred to as a “second catadioptric projection optical system according to the present invention”) described in the embodiments of the present specification, for example, as shown in FIG. ) Pattern image on the second surface (1
1) A first imaging optical system (G ₁ , G ₂ ) for forming an intermediate image of the pattern on the first surface of the optical system projecting onto the first optical system
And a second imaging optical system (G ₃ ) for forming an image of the intermediate image on the second surface thereof.

The first imaging optical system includes a first group (G ₁ ) having a positive refracting power, which contains a refracting lens component and converges a light beam from the pattern on the first surface, and the light of the first group. A partial mirror (8) for separating a part of the light beam from the first group by a reflecting surface arranged obliquely to the axis, and a concave reflecting mirror (M ₂ ) for reflecting the light beam separated by this partial mirror.
And a second group (G ₂ ) of positive refractive power that forms an intermediate image of the pattern near the reflecting surface of the partial mirror (8), and a part of the light flux converged by the second group is , And is guided by the partial mirror (8) to the second imaging optical system (G ₃ ).

In this case, since the light beam reflected by the partial mirror (8) is used, it is desirable that the image forming range is slit-shaped or arc-shaped. That is, this second catadioptric projection optical system is suitable for a scanning exposure type projection exposure apparatus. In this case, since the partial mirror (8) is used and the influence of repeated reflection is small, it is not necessary to use the quarter wave plate.

In these cases, the Petzval sums of the first group (G ₁ ), the second group (G ₂ ), and the second imaging optical system (G ₃ ) are p ₁ , p ₂ , and p ₃ , respectively. Then, it is desirable to satisfy the following conditions. p ₁ + p ₃ > 0 (1) p ₂ <0 (2) | p ₁ + p ₂ + p ₃ | <0.1 (3) Furthermore, the primary image formation from the pattern on the first surface to the intermediate image The second magnification from the intermediate image to the image on the second surface is β ₁₂
When the magnification of the next image formation is β ₃ and the magnification from the first surface to the second surface is β, it is desirable to satisfy the following conditions.

0.1 ≦ | β ₁₂ | ≦ 0.5 (4) 0.25 ≦ | β ₃ | ≦ 2 (5) 0.1 ≦ | β | ≦ 0.5 (6) Next, the present invention The first projection exposure apparatus according to the above is a projection exposure apparatus that projects an image of a pattern of a reticle on a wafer based on light from the pattern of the reticle, and includes the catadioptric projection optical system of the present invention. A second projection exposure apparatus according to the present invention is a scanning exposure type projection exposure apparatus that performs exposure while scanning a reticle and a wafer, and is provided with the catadioptric projection optical system of the present invention, and the reticle When the projection magnification on the wafer is β and the scanning speed of the reticle is V _R , the wafer is scanned at the speed β · V _R. The first projection exposure method according to the present invention is a projection exposure method for projecting an image of a pattern on a wafer based on light from a pattern of a reticle, and the pattern is formed using the catadioptric projection optical system of the present invention. Is projected onto the wafer. A second projection exposure method according to the present invention is a scanning exposure type projection exposure method in which exposure is performed while scanning a reticle and a wafer.
When an image of the pattern of the reticle is projected onto the wafer using the catadioptric projection optical system of the present invention, the projection magnification from the reticle to the wafer is β, and the scanning speed of the reticle is V _R , The wafer is scanned at a speed β · V _R.

[0022]

The first catadioptric projection optical system according to the present invention is suitable for a projection exposure apparatus of a batch exposure type. In this case, the light beam and concave reflecting mirror incident on the concave reflecting mirror (M ₂₎ (M ₂₎
The beam from and the prism type beam splitter (6)
And the beam splitter (6) is disposed in the vicinity of the portion where the light flux from the concave reflecting mirror (M ₂ ) is once condensed and imaged, and thus the prism type beam splitter ( 6) can be miniaturized.

Further, since the image is once formed between the concave reflecting mirror (M ₂ ) and the image surface (5), the second image forming optical system (G
_An aperture stop (4) can be placed inside ₃ ). Therefore,
The coherence factor (σ value) can be easily adjusted. In this regard, since the second imaging optical system (G ₃ ) is re-imaging after the primary imaging, the lens from the tip of the second imaging optical system (G ₃ ) is moved to the image plane (5). It is possible to secure a sufficiently long working distance (working distance).

Particularly, in the projection exposure apparatus of the batch exposure system,
Since the beam splitter (6) to be used is arranged near the primary image plane, the beam splitter (6) can be made as small as possible. Next, since the second catadioptric projection optical system of the present invention uses the partial mirror (8) as shown in FIG. 6, the good image range on the image plane (11) is slit-shaped or It has an arc shape and is suitable for a scanning exposure type projection exposure apparatus. In this case, since the image is formed once near the partial mirror (8), the partial mirror (8) may be small, and the characteristics of the reflective film of the partial mirror (8) are stable.

In the partial mirror (8), the optical path can be separated by giving a slight angle of view. That is, since a large angle of view is not required for optical path separation, it is possible to have a margin in image forming performance. In this regard, typical catadioptric projection optics have a maximum of about 20 due to optical path separation.
Although an angle of view of not less than ° is required, the angle of view of the light beam incident on the partial mirror (8) is about 10 °, and it is not necessary to make an aberration correction.

A so-called ring-field optical system is known as a projection optical system for the scanning exposure system, and this ring-field optical system is configured to illuminate only the off-axis ring zone. However, in the ring-field optical system, it is difficult to increase the numerical aperture by using the off-axis light beam, and since the optical member has an asymmetric structure with respect to the optical axis, it is possible to process, inspect, and adjust the optical member. It is difficult, and there is an inconvenience that it is difficult to obtain and maintain accuracy. On the other hand, in the case of the present invention, since the angle of view is not set large,
The structure is such that there is little vignetting of the light flux.

Further, since the first image-forming optical system (G ₁ , G ₂ ) and the second image-forming optical system (G ₃ ) are independent structures, it is easy to process, inspect and adjust the optical members. Therefore, it is easy to obtain accuracy and maintain accuracy, and it has excellent imaging characteristics that enable a high numerical aperture. Next, in the first catadioptric projection optical system or the second catadioptric projection optical system, in order to further improve the performance of the optical system, first, the Petzval sum of the entire optical system must be near zero. For this reason,
It is desirable to satisfy the conditional expressions (1) to (3).

By satisfying the conditional expressions (1) to (3), the curvature of the image plane during the optical performance is prevented and the flatness of the image plane is improved. If the upper limit of conditional expression (3) is deviated (p ₁ + p ₂ + p ₃ ≧ 0.1), the image surface is concavely curved toward the object side, and if the lower limit of conditional expression (3) is exceeded, (p ₁ +
p ₂ + p ₃ ≦ −0.1), the image plane is convexly curved toward the object side, and the imaging performance is significantly deteriorated.

Conditional expression (4) is used for the primary imaging magnification β ₁₂ , the secondary imaging magnification β ₃ , and the overall imaging magnification β.
By satisfying (6) to (6), the optical system can be configured without difficulty. If the lower limits of the conditional expressions (4) to (6) are not satisfied, the reduction ratio is too high and it becomes difficult to expose a wide range. Further, if the upper limit is exceeded, the enlargement magnification becomes too large, and when it is applied to the projection exposure apparatus, it is against the original intended use of reduced projection.

At this time, since the conditional expression (4) is satisfied, most of the reduction magnification of the entire optical system is occupied by the first imaging optical system (G ₁ ). Therefore, especially the beam splitter (6) or the partial mirror (8) can be miniaturized. Further, when the positions of the beam splitter (6) of FIG. 1 or the partial mirror 8 of FIG. 6 as the light beam separating means and the positions of the entrance pupil and the exit pupil of the optical system are made to substantially coincide with each other, the change in the object height is suppressed. Since the occluded portion on the pupil does not change, the image forming performance does not change over the entire image plane.

Further, in such an exposure optical system, at least the image plane side is telecentric so that the magnification does not change with respect to the variation in the optical axis direction of the image plane on which the wafer or the like is positioned. Is desirable.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the catadioptric projection optical system according to the present invention will be described below with reference to the drawings. In this example, the present invention is applied to a projection optical system of a projection exposure apparatus that projects an image of a reticle pattern onto a wafer coated with a photoresist at a predetermined magnification.

In the following embodiments, the lens arrangement is shown in FIG.
As shown in FIG. In the developed optical path diagram, the reflecting surface is shown as a transmitting surface, and the optical elements are arranged in the order in which the light from the reticle 10 passes. Further, for the reflecting surface (eg, r ₁₄ ) of the concave reflecting mirror, a virtual plane surface (eg, r ₁₅ ) is used. Then, in order to represent the shape and the interval of the lens, for example, as shown in FIG.
The pattern surface of 0 is the 0th surface, and the surface through which the light emitted from the reticle 10 passes until it reaches the wafer 11 is sequentially defined as the i-th surface (i = 1, 2, ...) And the radius of curvature of the i-th surface. The sign of r _i is positive when it is convex with respect to the reticle 10 in the expanded optical path diagram. Further, the surface distance between the i-th surface and the (i + 1) th surface is d _i . Further, as a glass material, SiO ₂ represents quartz glass. Reference wavelength of quartz glass (193
(nm) is as follows. Quartz glass: 1.56100

[First Embodiment] In the first embodiment, the magnification is 1.
It is a projection optical system suitable for a batch exposure type projection exposure apparatus (stepper or the like) at / 4 times. The first embodiment is also an embodiment corresponding to the optical system of FIG. FIG. 2 is a development optical path diagram of the projection optical system of the first embodiment. As shown in FIG. 2, the light from the pattern on the reticle 10 causes the first converging group G ₁ composed of four refracting lenses. After that, the beam splitter surface (r
₁₀ ) is reflected. This reflected light passes through a quarter-wave plate (not shown), and then the negative meniscus lens L ₂₀ and the concave reflecting mirror M.
Reaches the second converging group G ₂ consisting of _2, light is a quarter wavelength plate, reflected by the second converging group G ₂ via (not shown), forms an intermediate image of the pattern into the polarization beam splitter 6A To do.

Then, the light from this intermediate image, that is, the light flux transmitted through the polarization beam splitter 6A, is reflected by the refraction lens 1.
A second intermediate image of the pattern is formed on the surface of the wafer 11 through the third convergent group G ₃ consisting of four sheets. In this case, the aperture stop 4 is arranged between the Fourier transform surface in the third convergent group G ₃ , that is, between the positive meniscus lens L ₃₆ and the concave lens L ₃₇ .

As shown in FIG. 2, the first convergence group G₁ 
The convex surface toward the reticle 10 in order from the reticle 10 side.
Positive meniscus lens L₁₁, With the convex surface facing the reticle 10.
Negative negative meniscus lens L₁₂, Biconvex lens (hereinafter, simply
"Convex lens") L₁₃And a biconcave lens (hereinafter, simply
"Concave lens" L₁₄2nd convergence group G
₂Is a negative meniscus lens with a concave surface facing the reticle 10.
L₂₀And concave reflector M₂Consists of. Furthermore, the third convergence group G
₃Is a positive meniscus lens with a concave surface facing the reticle 10.
L₃₁, Convex lens L₃₂, With the reticle 10 facing the concave side
Varnish lens L ₃₃, Convex lens L₃₄, Convex lens L₃₅,
Positive meniscus lens L with convex surface facing the chicle 10₃₆, Concave
Lens L₃₇, Convex lens L₃₈, Convex lens L₃₉, Reticle 1
Negative meniscus lens L with concave surface facing 0_3A, Convex lens L
_3B, Negative meniscus lens L with convex surface facing reticle 10
_3C, A positive meniscus lens L with a convex surface facing the reticle 10.
_3D, And a negative meniscus lens with its convex surface facing the reticle 10.
Z L_3EIt is composed of

The magnification of the entire system is 1/4 (reduction), the numerical aperture NA on the wafer 11 side (image side) is 0.4, and the object height is 3.
It is 0 mm. Although the refraction lens uses one type of optical glass made of fused silica, axial and lateral chromatic aberrations are corrected for a wavelength width of 1 nm at a wavelength of 193 nm of the ultraviolet excimer laser light. Also,
It is an optical system with excellent imaging performance in which spherical aberration, coma aberration, astigmatism, and distortion are well corrected to near aberration-free states, and the optical system of FIG. Even if it is used, good imaging performance can be maintained.

The radius of curvature r _i in the first embodiment of FIG.
The surface spacing d _i and the glass material are shown in Table 1 below. In the table below, the fifteenth surface is a virtual surface for expressing the concave reflecting mirror in a developed optical path diagram.

[0039]

[Table 1]

3A to 3C are longitudinal aberration diagrams of the first embodiment, FIG. 3D is a lateral chromatic aberration diagram of the first embodiment, and FIG. 3E is a diagram of the first embodiment. The lateral-aberration figure is shown. In these aberration charts, symbols J, P and Q indicate characteristics when the used wavelength is changed within a predetermined range with respect to the reference wavelength. From these aberration diagrams, it can be seen that in this example, although the numerical aperture is as large as 0.4, various aberrations are well corrected in the wide image circle region. Also, chromatic aberration is well corrected.

[Second Embodiment] In the second embodiment, the magnification is 1.
It is a projection optical system suitable for a scanning exposure type projection exposure apparatus of / 4 times. The second embodiment is also a modification of the optical system shown in FIG. FIG. 4A is a developed optical path diagram of the projection optical system of the second embodiment, and FIG. 4B shows an illumination area on the reticle 10. As shown in FIG. 4B, the arcuate illumination area 12 on the reticle 10 is illuminated by an illumination optical system (not shown). Then, in FIG.
Light from the pattern in the illumination area 12 on the reticle 10 passes through the first converging group G ₁ including four refracting lenses,
The light is transmitted through the transmission part of the joint surface of the cubic partial reflection beam splitter 6B. This partially reflective beam splitter 6
A reflective film 6 having a reflectance of almost 100% around the bonding surface of B
Ba is formed, and the portion other than the reflective film 6Ba is a transmissive surface having a transmittance of almost 100%.

This reflected light reaches the second converging group G ₂ including the negative meniscus lens L ₂₀ and the concave reflecting mirror M ₂ , and the second converging group G ₂ is formed.
The light reflected by the converging group G ₂ forms an intermediate image of the pattern in the illumination area 12 in the vicinity of the reflective film 6Ba in the partially reflective beam splitter 6B. Then, the light from this intermediate image is reflected by the reflection film 6Ba, passes through the third convergence group G ₃ consisting of 14 refracting lenses, and forms the second intermediate image of the pattern on the surface of the wafer 11. When the projection magnification from the reticle 10 to the wafer 11 is β, the reticle 12 is scanned upward at a predetermined speed V _R in synchronization with the upward scanning of the wafer 11 at a speed β · V _R. Exposure is performed by the exposure method.

As shown in FIG. 4A, the first convergent group G ₁ includes, in order from the reticle 10 side, a convex lens L ₁₁ , a concave lens L ₁₂ , a positive meniscus lens L ₁₃ having a concave surface facing the reticle 10 and a concave lens. L ₁₄ composed of the second convergent group G
Reference numeral ₂ is composed of a negative meniscus lens L ₂₀ having a concave surface facing the reticle 10 and a concave reflecting mirror M ₂ . Furthermore, the third convergence group G
Reference numeral ₃ denotes a positive meniscus lens L ₃₁ having a concave surface facing the reticle 10, a convex lens L ₃₂ , a positive meniscus lens L ₃₃ having a concave surface facing the reticle 10, a convex lens L ₃₄ , a convex lens L ₃₅ , and a positive meniscus having a convex surface facing the reticle 10. Lens L ₃₆ , concave lens L ₃₇ , positive meniscus lens L ₃₈ with concave surface facing reticle 10, convex lens L ₃₉ , negative meniscus lens L _3A with concave surface facing reticle 10, convex lens L _3B , reticle 1
Negative meniscus lens L _3C with convex surface facing 0, reticle 1
The positive meniscus lens L _3D has a convex surface facing 0, and the negative meniscus lens L _3E has a convex surface facing the reticle 10.

The magnification of the entire system is 1/4 (reduction), the numerical aperture NA on the wafer 11 side (image side) is 0.5, and the object height is 2.
It is 2 mm. It is also possible to use the one-shot exposure method. Although the refraction lens uses one type of optical glass made of fused silica, the axial and lateral chromatic aberrations are corrected with respect to the wavelength width of 1 nm at the wavelength of 193 nm of the ultraviolet excimer laser light. . Further, the optical system has excellent imaging performance in which spherical aberration, coma aberration, astigmatism, and distortion are well corrected to a state close to no aberration.

Table 2 below shows the radius of curvature r _i , the surface distance d _i and the glass material in the second embodiment of FIG. 4 (a). In the table below, the 14th surface is a virtual surface for expressing the concave reflecting mirror in a developed optical path diagram.

[0046]

[Table 2]

5 (a) to 5 (c) are longitudinal aberration diagrams of the second embodiment, FIG. 5 (d) is a lateral chromatic aberration diagram of the second embodiment, and FIG. 5 (e) is the second embodiment. The lateral-aberration figure is shown. From these aberration diagrams, it can be seen that in this example, although the numerical aperture is as large as 0.5, the various aberrations are well corrected in the wide image circle region. Also, chromatic aberration is well corrected.

[Third Embodiment] The third embodiment has a magnification of 1
It is a projection optical system suitable for a scanning exposure type projection exposure apparatus of / 4 times. The third embodiment is also an embodiment of an optical system using a partial mirror. FIG. 6A is a developed optical path diagram of the projection optical system of the third embodiment, and FIG. 6B is a reticle 10 thereof.
The upper illuminated area is shown. As shown in FIG. 6B, the arcuate illumination area 12 on the reticle 10 is illuminated by an illumination optical system (not shown). Then, in FIG. 6A, the light from the pattern in the illumination area 12 on the reticle 10 passes through the side surface of the partial mirror 8 via the first converging group G ₁ composed of four refracting lenses.

This passing light reaches the second converging group G ₂ composed of the negative meniscus lens L ₂₀ and the concave reflecting mirror M ₂ , and the second converging group G ₂ is formed.
The light reflected by the convergence group G ₂ forms an intermediate image of the pattern in the illumination area 12 in the vicinity of the partial mirror 8. Then, after the light from this intermediate image is reflected by the partial mirror 8, the second intermediate image of the pattern is formed on the surface of the wafer 11 through the third convergence group G _{3 including} 14 refracting lenses. . Further, the aperture stop 4 is arranged between the Fourier transform surface in the third convergent group G ₃ , that is, between the convex lens L ₃₄ and the convex lens L ₃₅ . In this case, assuming that the projection magnification from the reticle 10 to the wafer 11 is β, the wafer 11 is moved upward by a speed β · in synchronization with the upward scanning of the reticle 12 at a predetermined speed V _R.
By scanning at V _R , exposure is performed by the scanning exposure method.

As shown in FIG. 6A, the first convergent group G ₁ includes, in order from the reticle 10 side, a positive meniscus lens L ₁₁ having a convex surface facing the reticle 10 and a negative meniscus lens having a convex surface facing the reticle 10. The second convergent group G ₂ is composed of a lens L ₁₂ , a convex lens L ₁₃ and a concave lens L _14, and a negative meniscus lens L ₂₀ having a concave surface facing the reticle 10 and a concave reflecting mirror M ₂ . Further, the third convergent group G ₃ includes a negative meniscus lens L ₃₁ having a concave surface facing the reticle 10, a positive meniscus lens L ₃₂ having a concave surface facing the reticle 10, a positive meniscus lens L ₃₃ having a concave surface facing the reticle 10, and a convex lens. L ₃₄ , a convex lens L ₃₅ , a positive meniscus lens L _{36 with} a convex surface facing the reticle 10, a concave lens L ₃₇ , a positive meniscus lens L ₃₈ with a concave surface facing the reticle 10, a convex lens L ₃₉ , and a negative meniscus lens with a concave surface facing the reticle 10. A lens L _3A , a convex lens L _3B , a negative meniscus lens L _3C having a convex surface facing the reticle 10, a positive meniscus lens L _3D having a convex surface facing the reticle 10, and a negative meniscus lens L _3E having a convex surface facing the reticle 10. ing.

The magnification of the entire system is 1/4 (reduction), the numerical aperture NA on the wafer 11 side (image side) is 0.4, and the object height is 2.
It is 6 mm. It is also possible to use the one-shot exposure method. Although the refraction lens uses one type of optical glass made of fused silica, the axial and lateral chromatic aberrations are corrected with respect to the wavelength width of 1 nm at the wavelength of 193 nm of the ultraviolet excimer laser light. . In addition, spherical aberration, coma aberration, astigmatism, and distortion are also excellently corrected to a nearly aberration-free state, and have an excellent imaging performance. Even if it is used, the good imaging performance can be maintained.

Table 3 below shows the radius of curvature r _i , the surface distance d _i, and the glass material in the third embodiment of FIG. 6 (a). In the table below, the 14th surface is a virtual surface for expressing the concave reflecting mirror in a developed optical path diagram.

[0053]

[Table 3]

7 (a) to 7 (c) are longitudinal aberration diagrams of the third embodiment, FIG. 7 (d) is a lateral chromatic aberration diagram of the third embodiment, and FIG. 7 (e) is the third embodiment. The lateral-aberration figure is shown. From these aberration diagrams, it can be seen that in this example, although the numerical aperture is as large as 0.4, various aberrations are well corrected in the wide image circle region. Also, chromatic aberration is well corrected.

[Fourth Embodiment] In the fourth embodiment, the magnification is 1.
It is a projection optical system suitable for a batch exposure type projection exposure apparatus (stepper or the like) at / 4 times. The fourth embodiment is also an embodiment in which the optical system of FIG. 1 is modified. FIG. 8 is a development optical path diagram of the projection optical system of the fourth embodiment. As shown in FIG. 8, the light from the pattern on the reticle 10 causes the first converging group G ₁ composed of four refracting lenses. After that, the beam splitter surface 6 of the rectangular parallelepiped polarization beam splitter 6C
It is incident on Ca. Polarization beam splitter 6 of this embodiment
C is a rectangular parallelepiped, and the incident surface (r ₉ ) of the illumination light is wider than the projected image of the beam splitter surface 6Ca by the area 13. As a result, the polarization beam splitter 6C of FIG. 8 can be made thinner than the polarization beam splitter 6A of FIG.

The light beam that has passed through the beam splitter surface 6Ca passes through a quarter-wave plate (not shown) and then comes to a second convergent group G composed of a negative meniscus lens L ₂₀ and a concave reflecting mirror M _2.
2 , the light reflected by the second convergent group G ₂ passes through a quarter-wave plate (not shown), is reflected by the beam splitter surface 6Ca in the polarization beam splitter 6A, and then is reflected by the polarization beam splitter 6A. An intermediate image of the pattern is formed at a close position.

Then, the light flux from this intermediate image is refracted
3rd convergent group G consisting of 14 sheets₃Through the wafer 11
A second intermediate image of the pattern is formed on the surface of the. This place
If the third convergence group G₃Fourier transform plane in, i.e. positive menis
Caslens L₃₈And convex lens L ₃₉Aperture stop 4 is placed between
It is placed. Further, as shown in FIG. 8, the first convergence group G
₁ The convex surface toward the reticle 10 in order from the reticle 10 side.
Key positive meniscus lens L₁₁, Concave lens L₁₂,convex lens
L₁₃And concave lens L₁₄2nd convergence group G
₂Is a negative meniscus lens with a concave surface facing the reticle 10.
L₂₀And concave reflector M₂Consists of. Furthermore, the third convergence group G
₃Is a positive meniscus lens with a concave surface facing the reticle 10.
L₃₁, Convex lens L₃₂, A negative lens with a concave surface facing the reticle 10.
Varnish lens L₃₃, Convex lens L₃₄, Convex lens L₃₅,
Positive meniscus lens L with convex surface facing the chicle 10₃₆, Concave
Lens L₃₇, Positive meniscus with concave surface on reticle 10
Lens L₃₈, Convex lens L₃₉, Face the concave surface to the reticle 10.
Negative negative meniscus lens L_3A, Convex lens L_3B, Reticle 1
Negative meniscus lens L with convex surface facing 0_3C, Reticle 1
Positive meniscus lens L with convex surface facing 0 _3D, And retik
Negative meniscus lens L with the convex surface facing the lens 10_3EConsists of
Has been done.

The magnification of the entire system is 1/4 (reduction), the numerical aperture NA on the wafer 11 side (image side) is 0.6, and the object height is 2.
It is 0 mm. Although the refraction lens uses one type of optical glass made of fused silica, axial and lateral chromatic aberrations are corrected for a wavelength width of 1 nm at a wavelength of 193 nm of the ultraviolet excimer laser light. Also,
It is an optical system with excellent imaging performance in which spherical aberration, coma aberration, astigmatism, and distortion are well corrected to near aberration-free states, and the optical system of FIG. Even if it is used, good imaging performance can be maintained.

The radius of curvature r _i in the fourth embodiment of FIG.
The surface spacing d _i and the glass material are shown in Table 4 below. In the table below, the 14th surface is a virtual surface for expressing the concave reflecting mirror in a developed optical path diagram.

[0060]

[Table 4]

9 (a) to 9 (c) are longitudinal aberration diagrams of the fourth embodiment, FIG. 9 (d) is a lateral chromatic aberration diagram of the fourth embodiment, and FIG. 9 (e) is the fourth embodiment. The lateral-aberration figure is shown. From these aberration diagrams, it can be seen that in this example, although the numerical aperture is as large as 0.6, various aberrations are well corrected in the wide image circle region. Also, chromatic aberration is well corrected.

Next, in the present invention, the conditional expressions (1) to (6) are
Although it is said that it is desirable to satisfy,
Correspondence between each of the embodiments and their conditional expressions will be described.
First, the concave reflecting mirror M in each of the above-described embodiments.₂Half the curvature of
Diameter r, i-th convergent group G_iFocal length f of (i = 1 to 3)_i, Bae
Tsval sum p_i, Apparent refractive index n_i, Imaging magnification
β _i, First convergence group G₁And the second convergence group G₂Double the synthetic system with
Rate β₁₂, 3rd convergent group G₃Imaging magnification β of₃, Petz of the whole system
The Barr sum p and the magnification β of the whole system are as shown in Table 5 to Table 8.
ing. However, the whole system is G_TExpressed by, the whole system G_TCorresponds to
Ru Petzval sum p _iAnd imaging magnification β_iThat's the column
3 shows the Petzval sum and the imaging magnification of the entire system.

[0063]

[Table 5]

[0064]

[Table 6]

[0065]

[Table 7]

[0066]

[Table 8]

Further, based on Tables 5 to 8, in each embodiment, (p ₁ + p ₃ ), p ₂ , | p ₁ + p ₂ + p
Table 9 below shows the values of ₃ |, | β ₁₂ |, | β ₃ |, and | β |.

[0068]

[Table 9]

From this table, it can be seen that the conditions of the conditional expressions (1) to (6) are satisfied in each of the above-described embodiments. Although quartz is used as the glass material forming the refractive optical system in each of the above-described embodiments, optical glass such as fluorite may be used. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention.

[0070]

According to the invention of claim 1 of the present application (the first catadioptric projection optical system of the invention), a concave reflecting mirror and a second reflecting mirror are provided.
Since the image is formed once with the surface (image surface), there is an advantage that a small prism type beam splitter can be used and the optical path from the concave reflecting mirror to the image surface can be long.
Therefore, the deterioration of the imaging characteristics due to the non-uniformity of the characteristics on the semi-transmissive surface of the beam splitter can be reduced, and the working distance can be increased.

Further, unlike the ring-field optical system which projects only the annular zone by using the off-axis light beam, there is an advantage that the batch exposure method can be adopted with a high numerical aperture. Further, since an aperture stop can be placed in the second imaging optical system, there is an advantage that the σ value which is a coherence factor can be freely controlled. Further, in the conventional catadioptric optical system, the optical axis is decentered, so that the adjustment work is difficult, and it is difficult to realize the imaging performance as designed. However,
In the catadioptric projection optical system according to the present invention, if the first image forming optical system and the second image forming optical system can be adjusted independently, and then the two image forming optical systems are arranged with their optical axes substantially vertical. Since it is good, it is easy to adjust the eccentricity and the like.

Since the image forming magnification of the first image forming optical system can be freely selected, an excellent optical performance state can be realized. In this case, there is an advantage that the beam splitter can be further downsized by forming an intermediate image inside the prism type beam splitter. Next, the second aspect of the present invention
According to the catadioptric projection optical system of, since the image is once formed between the concave reflecting mirror and the second surface (image surface), it is possible to use a small partial mirror, and from the concave reflecting mirror to the image surface. There is an advantage that the optical path of can be taken long. Further, when a partial mirror is used, a good image forming range is, for example, an arc shape or a slit shape decentered from the optical axis, and such an image forming range is suitable for a scanning exposure type projection exposure apparatus. .

Next, when the conditional expressions (1) to (3) are satisfied, the Petzval sum of the entire optical system easily becomes almost 0 and the projected image plane becomes substantially flat. Further, by satisfying the conditional expressions (4) and (5), it becomes possible to easily construct an optical system without overcommitting the magnification distribution.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a basic configuration of a catadioptric projection optical system according to the present invention.

FIG. 2 is a developed optical path diagram of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 3 is an aberration diagram of the first example.

FIG. 4 is a developed optical path diagram of a projection optical system of a second example.

FIG. 5 is an aberration diagram of the second example.

FIG. 6 is a developed optical path diagram of a projection optical system of a third example.

FIG. 7 is an aberration diagram for the third example.

FIG. 8 is a developed optical path diagram of a projection optical system of a fourth example.

FIG. 9 is an aberration diagram of the fourth example.

FIG. 10 is a schematic diagram showing a configuration of a conventional catadioptric projection optical system.

[Explanation of symbols]

1 Object Plane 2 Image Plane 3 1/4 Wave Plate 4 Aperture Stopper 10 Reticle 11 Wafer G ₁ First Convergence Group G ₂ Second Convergence Group G ₃ Third Convergence Group M ₂ Concave Reflecting Mirror 6, 6A, 6C Polarizing Beam Splitter 6B Partial reflection beam splitter 8 Partial mirror

Claims (10)

[Claims] 1. An optical system for projecting an image of a pattern on a first surface onto a second surface, wherein a first imaging optical system that forms an intermediate image of the pattern on the first surface, and an image of the intermediate image are formed. A second imaging optical system formed on the second surface, wherein the first imaging optical system includes a refraction lens component.
A first group having a positive refracting power that converges a light beam from a surface pattern; and a part of the light beam from the first group is separated by a beam splitter surface obliquely arranged with respect to the optical axis of the first group. A prism type beam splitter; and a second group having a positive refracting power that includes a concave reflecting mirror that reflects the light beam separated by the prism type beam splitter and forms an intermediate image of the pattern near the prism type beam splitter. A part of the light flux converged by the second group is separated by the prism type beam splitter and guided to the second imaging optical system. 2. The catadioptric projection optical system according to claim 1, wherein an intermediate image of the pattern is formed inside the prism type beam splitter. 3. The first group, the second group, and the second imaging optics
P for each individual Petzval sum of the system₁ , P₂ And p
₃ And when p₁ + P₃ > 0, p₂ <0, and | p₁ + P₂ Ten p₃ ｜
<0.1 From the pattern on the first surface while satisfying the condition
The magnification to the intermediate image is β ₁₂And from the intermediate image to the
Β to the image on the two surfaces₃ And when 0.1 <| β₁₂| <0.5, and 0.25 <| β₃ ｜ ＜
Two The reflection according to claim 1, which satisfies the condition of
Refractive projection optics. 4. The catadioptric projection optical system according to claim 1, wherein the second imaging optical system has an aperture stop for adjusting a coherence factor. 5. The first image forming optical system and the second image forming optical system are independent structures.
9. The catadioptric projection optical system according to any one of items 1. 6. The catadioptric projection optical system according to claim 1, wherein the catadioptric projection optical system is telecentric at least on the image plane side. 7. A projection exposure apparatus for projecting an image of the pattern on a wafer based on light from a pattern of a reticle, comprising the catadioptric projection optical system according to claim 1. A characteristic projection exposure apparatus. 8. The projection exposure apparatus is a scanning exposure type projection exposure apparatus that performs exposure while scanning the reticle and the wafer, wherein the projection magnification from the reticle to the wafer is β, and the reticle is scanned. 8. The projection exposure apparatus according to claim 7, wherein when the speed is V _R , the wafer is scanned at a speed β · V _R. 9. A projection exposure method for projecting an image of the pattern on a wafer based on light from a pattern of a reticle, wherein the catadioptric projection optical system according to claim 1 is used. A projection exposure method, which comprises projecting an image of a pattern onto the wafer. 10. Scanning the reticle and the wafer
While exposing, project from the reticle to the wafer
The magnification is β and the scanning speed of the reticle is V _R And
The speed of the wafer is β · V._R Characterized by scanning with
The projection exposure method according to claim 9.