JP2002118058A - Projection aligner and projection exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner that can readily reduce fluctuation in aberration generated by change in temperature due to the irradiation of exposure light. SOLUTION: Light from the pattern of a mask 3 forms a primary image I of a mask pattern via a first image-forming optical system K1. Light from the primary image I is reflected by a submirror M2 via the center opening of the main mirror M1 and a lens component L2, and the light reflected by the submirror M2 is reflected by the main mirror M1 via the lens component L2. The light reflected by the main mirror M1 forms the secondary image of the mask pattern with reduced magnification on the surface of a wafer 9 via the lens component L2 and the center opening of the submirror M2. At this time, a reflecting surface R2 of the submirror M2 is lined with a heat sink 81, having thermal conductivity larger than that of the lens component L2, thus allowing heat generated on the reflecting surface R12 that is a back- reflecting surface, having relatively large heat generation tending to allow escape to the heat sink 81 as compared with the lens component L2, and hence forming an image accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus and an exposure method for manufacturing, for example, a semiconductor device or a liquid crystal display device by a photolithography process, and more particularly, to a projection exposure system including a catadioptric optical system and a reflective optical system. The present invention relates to a projection exposure apparatus and an exposure method using the same.

[0002]

2. Description of the Related Art In a photographic process for manufacturing a semiconductor device or the like,
2. Description of the Related Art A projection exposure apparatus that exposes a pattern image of a photomask or a reticle (hereinafter collectively referred to as a “reticle”) onto a wafer (or a glass plate or the like) coated with a photoresist or the like via a projection optical system is used. ing.

[0003] The resolution required for a projection optical system used in such a projection exposure apparatus has been increasing as the degree of integration of semiconductor elements and the like has increased. In order to satisfy this requirement, it is necessary to shorten the wavelength of the illumination light and increase the numerical aperture (NA) of the projection optical system.

However, when the wavelength of the illumination light is shortened, the types of glass materials that can withstand practical use due to light absorption are limited. When the wavelength is 300 nm or less, at present, only synthetic quartz and fluorite are practically usable. Therefore, it is desired to use a reflection optical system as a means for correcting chromatic aberration.
Specifically, practical use of a 248 nm KrF laser in a refraction system is considerably advanced, but practical use in a refraction system is considerably difficult below 200 nm, and expectations for a catadioptric optical system are increasing. In particular, if it is fluorite, 100
It is known that there is a sufficient transmittance up to nm, and if it is within this range, it can be used as a refraction member.

Several types of catadioptric systems have already been proposed. N. A. The optical system of the type in which the central part is shielded (hereinafter, abbreviated as the central shielding type) uses two or more reflecting surfaces, so that all optical systems are based on one optical axis without an optical path deflecting member. Since the element can be assembled and an object on the optical axis can be imaged on the image plane, there is a merit that aberration can be corrected in a wide exposure field with a small number of optical members. Conventional techniques of this type include those disclosed in U.S. Patent Nos. 5,717,518 and 5,650,877.

Here, generally, in a projection exposure apparatus,
At the time of exposure, the projection optical system is irradiated with illumination light to absorb the illumination light (that is, the exposure light), so that, for example, an asymmetric deformation, an internal temperature distribution, or the like occurs in the optical member, and aberration fluctuation occurs ( See JP-A-9-213611).

It is considered that such aberration fluctuations are caused not only by the absorption generated inside the glass material of the projection optical system but also by the absorption generated by a thin film on the surface. In particular, in a catadioptric system, it is considered that the absorption on the reflection surface is particularly large compared to the inside of the glass material or the surface thin film, and there is a high possibility that the aberration fluctuation due to the absorption becomes a problem compared to the case of the refraction optical system. .

In a projection optical system in the extreme ultraviolet region, the use of a back mirror which causes reflection on the back surface of a refraction member is effective as in the above-mentioned US Pat. No. 5,717,518. It is necessary to use a glass material that can transmit light in this wavelength range, such as quartz, fluorite, BaF ₂ and LiF ₂ . Since these glass materials have a large dN / dT and a large coefficient of expansion, when the refraction member has a reflection surface as described above, a relatively large amount of heat generated on the reflection surface propagates into the refraction member and the glass is refracted. A relatively large temperature distribution is generated inside, and it is considered that some countermeasure for suppressing the fluctuation of aberration is required. In particular, in the case of exposure light of 200 nm or less, the development of a thin film is being carried out. In this wavelength range, the performance expected of the projection optical system itself becomes extremely high, and the light including the reflection surface is included. Aberration fluctuation due to irradiation of the optical member is a major problem.

In addition, the above-mentioned US Pat. No. 5,717,
In the projection optical system disclosed in Japanese Patent Application Publication No. 518, a light beam is considerably concentrated in a portion where a final image is formed near the reduced image plane, that is, in the last optical path in the refraction / reflection member. Such a light beam causes a non-uniform and large temperature distribution in the optical member, which is problematic.

Further, even in the reflecting member, for compatibility with reflection coating, may need to use a material having a large coefficient of expansion such as CaF ₂ and BSC7, much greater absorption than the case where the refractive member Aberrations caused by rate-dependent thermal expansion are problematic.

In order to avoid this, it is conceivable to separate this refraction / reflection member from the image plane. However, taking the refraction / reflection member away from the image plane takes into account that the central shielding portion needs to be as small as possible. Then, there is considerable difficulty in designing. As means for coping with aberrations caused by such non-uniform temperature distribution, for example, Japanese Unexamined Patent Application Publication No.
In this publication, attention is paid to the fact that rotationally asymmetric aberration fluctuation occurs when scanning exposure or the like is performed, and an optical unit formed of an aspheric surface is prepared in advance in response to the aberration fluctuation, and this is moved as necessary. Methods have been proposed. But,
In order to carry out such a method, it is necessary to produce a rotationally asymmetric aspheric surface corresponding to such aberration fluctuation,
A dedicated manufacturing apparatus is required, and a highly accurate eccentricity adjusting mechanism is also required to appropriately decenter the aspheric surface at the time of irradiation, so that it becomes difficult to manufacture a projection optical system.

Aberration fluctuations also occur due to a change in the temperature of the entire projection optical system. Among such aberration fluctuations, aberrations caused by deformation of the reflecting mirror are caused when the change in the light flux caused by reflection is refraction. Is about four times as large as that of the above-described catadioptric system, the influence of a temperature change tends to be a problem. Therefore, it can be said that a design in which the deformation of the reflecting mirror is considered in advance is desirable.

As a countermeasure against such a case, Japanese Patent Laid-Open No.
There is one disclosed in 144144. According to the present invention, a change in the thermal shape of a part of the lenses constituting the projection optical system is obtained, and the optical adjustment is performed by the adjusting means based on the change. However, as a practical matter, it seems to be quite difficult to measure the change in the shape of the lens during exposure without adversely affecting the exposure.

In view of the above problems, it is an object of the present invention to provide a projection exposure apparatus capable of easily reducing aberration fluctuations caused by a temperature change due to irradiation of a catadioptric optical system or the like with exposure light. .

[0015]

In order to solve the above-mentioned problems, a first projection exposure apparatus of the present invention converts an image on a first surface to a second image.
A projection exposure apparatus including a catadioptric optical system that forms an image on a surface, wherein the catadioptric optical system has a member including a reflective surface and includes a material having a higher thermal conductivity than the member including the reflective surface. And a heat transfer member disposed in contact with the member including the reflection surface. In a preferred aspect of the above-described device, the heat transfer member is in contact with an outside of an effective reflection area of the reflection surface of the member including the reflection surface, for example, a back surface of the reflection surface.

In this case, the heat transfer member including a material having a higher thermal conductivity than the member including the reflection surface is disposed in contact with the member including the reflection surface outside the effective reflection area of the reflection surface. The heat generated on the reflection surface due to the incidence of the exposure light can be easily dissipated outside the member including the reflection surface. Therefore, heat can be prevented from accumulating inside the member including the reflection surface, and high-precision exposure with reduced aberration variation can be performed.

Further, in order not to apply a mechanical load such as a pressure generated when the heat transfer member comes into direct contact with the reflective optical member having the reflective surface or the refractive optical member including the reflective surface, the optical member is prevented from being subjected to the mechanical load. 30 mm from the optical member at a position opposite to the direction in which light is reflected on the reflection surface of the optical member.
A heat transfer member having a large thermal conductivity disposed along the optical member may be provided at a position within the optical member, and at least a part of an interval between the optical member and the heat transfer member may be filled with a predetermined gas.

In this case, since the distance between the optical member and the heat transfer member is considerably small across the gas, the heat on the reflection surface can be radiated to the heat transfer member without receiving much thermal resistance of the gas. Therefore, accumulation of heat inside the optical member can be prevented, and high-precision exposure with reduced aberration fluctuations can be performed. The distance between the optical member and the heat transfer member is 30 mm.
Is exceeded, the heat does not conduct more than the heat capacity of the gas, so that heat cannot be effectively conducted to the heat transfer member.

In a preferred aspect of the above-mentioned apparatus, the apparatus further comprises a forced cooling means connected to the heat transfer member.

In this case, since the heat transfer member can be cooled by the forced cooling means, the heat radiation effect can be enhanced and the temperature rise of the member including the reflection surface can be more effectively suppressed.

In a preferred aspect of the above-mentioned apparatus, the catadioptric optical system has first and second reflecting surfaces disposed so as to face each other as the reflecting surface, and the first and second reflecting surfaces are: A central portion has first and second light transmitting portions capable of transmitting at least a part of a light beam, and at least one of the first and second reflecting surfaces is included in a member including the reflecting surface. .

In this case, the exposure light emitted from the first surface is
The light enters the first reflecting surface via the second light transmitting portion, is reflected on the first reflecting surface, is further reflected on the second reflecting surface, and is guided to the second surface via the first light transmitting portion. At this time, since at least one of the first and second reflection surfaces is included in the member including the reflection surface, the reflection occurred on one of the first and second reflection surfaces as a result of the back surface reflection by the member including the reflection surface. The heat can be quickly radiated to the outside of the member including the reflection surface by the heat transfer member.

According to a second aspect of the present invention, there is provided a projection exposure apparatus including a catadioptric optical system for forming an image on a first surface on a second surface, wherein the catadioptric optical system comprises a catadioptric optical system. First and second reflecting surfaces arranged as
A refraction member disposed between the reflection surfaces, wherein at least one surface of the refraction member is either uncoated or has three or less coats. And

In this case, in the refraction member disposed between the first and second reflection surfaces, the exposure light passes multiple times between the first and second reflection surfaces. At this time, at least one surface of the refraction member disposed between the first and second reflection surfaces is either uncoated or has three or less coats. Absorption at the transmission surface of the refraction member can be minimized.
Thereby, heat accumulation in the refraction member can be prevented, and high-precision exposure with reduced aberration fluctuations can be performed.

In a preferred aspect of the above-mentioned apparatus, at least one of the first and second reflecting surfaces has a positive power, and the first and second reflecting surfaces have at least a part of a light beam at a central portion. A light-shielding plate having first and second light-transmitting portions capable of transmitting light, and absorbing a light beam incident on the catadioptric optical system in a part of a space between the first and second light-transmitting portions; Having.

In this case, the exposure light emitted from the first surface is
The light enters the first reflecting surface via the second light transmitting portion, is reflected on the first reflecting surface, is further reflected on the second reflecting surface, and is guided to the second surface via the first light transmitting portion. At this time, a part of the space between the first and second light transmitting portions is provided with a light-shielding plate for absorbing the light flux incident on the catadioptric system, so that the first and second light-transmitting portions can be effectively utilized while effectively utilizing the exposure light. It is possible to suppress the occurrence of flare caused by the reflected light generated on the transmission surface of the refraction member disposed between the two reflection surfaces.

A third projection exposure apparatus according to the present invention is a projection exposure apparatus including a catadioptric optical system for forming an image on a first surface on a second surface, wherein the catadioptric optical system comprises a first catadioptric optical system. And at least one of the first and second reflecting surfaces has a positive power, and the first and second reflecting surfaces are capable of transmitting at least a part of a light flux to a central portion. A first and a second light transmitting portion, each of which is possible, wherein at least one of the first and second reflecting surfaces is formed on an end surface of the transmitting member, and a reflecting surface formed on an end surface of the transmitting member. When the effective diameter at the time of incidence is φ1 and the absorptance is S1 and the effective diameter at the time of incidence at the transmission surface in contact with the reflection surface formed on the end face of the transmission member is φ2 and the absorption ratio is S2, φ2 ² <3S1 / (φ1 ² −φ2 ² ) (1)

In this case, the exposure light emitted from the first surface is
The light enters the first reflecting surface via the second light transmitting portion, is reflected on the first reflecting surface, is further reflected on the second reflecting surface, and is guided to the second surface via the first light transmitting portion. At this time, since the above-mentioned conditional expression (1) is satisfied on the first reflecting surface or the second reflecting surface, absorption of the exposure light between the reflecting surface and the transmitting surface, that is, the calorific value is balanced to some extent. Therefore, it is possible to prevent the transmission member from being locally heated and to cause non-uniform aberration fluctuation, thereby enabling high-precision exposure.

A fourth projection exposure apparatus according to the present invention is a projection exposure apparatus including a projection optical system for forming an image on a first surface on a second surface, wherein the projection optical system includes at least one projection optical system. A reflecting mirror, and a coefficient of thermal expansion (d
When L / L) / dT is α, the expansion coefficient β of at least one of the materials forming the reflecting mirror satisfies the condition of α / 3 <β <3α, α ≠ β (2) Features.

In this case, since the expansion coefficient β of at least one of the materials forming the reflecting mirror satisfies the conditional expression (2), it is possible to make the expansion coefficient of the reflecting mirror substantially equal to that of the lens barrel. In other words, even if the focal length changes due to the heat generated by the reflecting mirror, the size of the lens barrel changes in accordance with the change, so that the change in the imaging state of the projection optical system can be suppressed,
High-precision exposure becomes possible.

Further, according to the projection exposure method of the present invention, the first
A projection exposure method using the projection exposure apparatus according to any one of (1) to (4), wherein a step of generating illumination light and a step of illuminating with the illumination light by disposing a mask on which the predetermined pattern is formed on the first surface; Projecting an image of the predetermined pattern of the mask disposed on the first surface onto a photosensitive substrate disposed on the second surface, using the catadioptric system.

In this case, since the first to fourth projection exposure apparatuses are used, variation in aberration of the projection optical system and variation in the state of image formation can be suppressed, and high-precision exposure can be performed. Also,
A fifth projection exposure apparatus according to the present invention is a projection exposure apparatus including a projection optical system that forms an image on a first surface on a second surface,
The projection optical system has a reflective optical member having a reflective surface or a refractive optical member including a reflective surface, and is located at a position opposite to a direction in which light is reflected by the reflective surface and is 30 mm from the optical member. And a heat transfer member disposed along the optical member at a position within a predetermined distance, wherein at least a portion between the heat transfer member and the reflection surface is filled with a predetermined gas. In this case, heat generated in the optical member including the reflective surface can be released to the heat transfer member via a predetermined gas, and as a result, thermal deformation of the optical member including the reflective surface can be reduced. Preferably, the predetermined gas includes a helium gas. Further, the projection exposure method of the present invention is the projection exposure method using the fifth projection exposure apparatus, wherein a step of generating illumination light and a mask having a predetermined pattern formed on the first surface. Disposing and illuminating with the illumination light, and using the projection optical system, the image of the predetermined pattern of the mask disposed on the first surface onto a photosensitive substrate disposed on the second surface. Projecting. In this case, since the fifth projection exposure apparatus is used, variation in aberration of the projection optical system and variation in imaging performance can be suppressed, and high-precision exposure can be performed.

[0033]

(First Embodiment) FIG. 1 schematically shows the entire configuration of a projection exposure apparatus according to a first embodiment of the present invention. In FIG. 1, the Z axis is parallel to the optical axis AX of the projection optical system 8 constituting the projection optical system, the X axis is parallel to the paper of FIG. 1 in a plane perpendicular to the optical axis AX, and the Z axis is perpendicular to the paper. Is set to the Y axis.

The illustrated projection exposure apparatus is provided with, for example, an F ₂ laser (oscillation center wavelength 157.6 nm) as a light source for supplying illumination light in the ultraviolet region. The light emitted from the light source 1 uniformly illuminates the mask 3 on which a predetermined pattern is formed, via the illumination optical system 2.

In the optical path from the light source 1 to the illumination optical system 2, one or a plurality of bending mirrors for deflecting the optical path are arranged as required. When the light source 1 and the projection exposure apparatus main body are separate bodies, the F
And automatic tracking unit for directing the orientation of the _second laser beam always to the projection exposure apparatus main body, shaping optical system for shaping the light flux cross-sectional shape of the F ₂ laser beam into a predetermined size and shape from the light source 1, the light quantity adjustment section An optical system is arranged. The illumination optical system 2 includes, for example, a fly-eye lens or an internal reflection type integrator to form a surface light source having a predetermined size and shape, and an optical integrator for defining the size and shape of an illumination area on the mask 3. It has an optical system such as a field stop and a field stop imaging optical system that projects an image of the field stop onto a mask. Further, a light source 1 and an illumination optical system 2
Is sealed by a casing (not shown), and a space from the light source 1 to the optical member closest to the mask in the illumination optical system 2 includes helium gas, which is a gas having a low absorption rate of exposure light, or helium gas. It has been replaced with an inert gas such as nitrogen.

The mask 3 is held on a mask stage 5 via a mask holder 4 in parallel with the XY plane. A pattern to be transferred is formed on the mask 3 and has a rectangular shape (slit shape) having a long side along the Y direction and a short side along the X direction in the entire pattern area.
Are illuminated.

The mask stage 5 can be moved two-dimensionally along the mask surface (ie, XY plane) by the action of a drive system (not shown), and its position coordinate is an interferometer using a mask moving mirror 6. 7 and is configured to be position-controlled.

The light from the pattern formed on the mask 3 forms a mask pattern image on a wafer 9 as a photosensitive substrate via a catadioptric projection optical system 8. The wafer 9 is placed on a wafer stage 11 via a wafer holder 10.
Above, it is held parallel to the XY plane. And
In order to optically correspond to a rectangular illumination area on the mask 3, the wafer 9 has a long side along the Y direction and X
A pattern image is formed in a rectangular exposure area having a short side along the direction.

The wafer stage 11 can be moved two-dimensionally along the wafer surface (ie, the XY plane) by the action of a drive system (not shown), and its position coordinates are determined by an interferometer 13 using a wafer moving mirror 12. And the position is controlled.

In the illustrated projection exposure apparatus, the projection optical system 8 is arranged between the optical member arranged closest to the mask and the optical member arranged closest to the wafer among the optical members constituting the projection optical system 8. The inside of the projection optical system 8 is replaced with an inert gas such as helium gas or nitrogen.

Further, a mask 3 and a mask stage 5 are disposed in a narrow optical path between the illumination optical system 2 and the projection optical system 8. (Not shown) is filled with an inert gas such as nitrogen or helium gas.

Further, on the optical path immediately below the projection optical system 8,
The wafer 9 and the wafer stage 11 are arranged. An inside of a casing (not shown) that hermetically surrounds the wafer 9 and the wafer stage 11 is filled with an inert gas such as nitrogen or helium gas.

As described above, an atmosphere in which the exposure light is hardly absorbed is formed over the entire optical path from the light source 1 to the wafer 9.

As described above, the visual field area (illumination area) on the mask 3 and the projection area (exposure area) on the wafer 9 defined by the projection optical system 8 have a rectangular shape having a short side along the X direction. It is. Therefore, while controlling the position of the mask 3 and the wafer 9 using the drive system and the interferometers (7, 13), the mask stage 5 is arranged along the short side direction of the rectangular exposure area and the illumination area, that is, in the X direction.
And the wafer stage 11, and thus the mask 3 and the wafer 9 are synchronously moved (scanned), so that the wafer 9 has a width equal to the long side of the exposure area and the wafer 9.
The mask pattern is scanned and exposed to a region having a length corresponding to the scanning amount (moving amount) of the mask pattern.

FIG. 2 is a view for explaining the structure of the projection optical system 8 incorporated in the projection exposure apparatus of FIG. The projection optical system 8 forms a primary image (intermediate image) of the pattern of the mask 3.
A first image forming optical system K1 for forming an image I and a second image forming system for forming a secondary image of a mask pattern on a wafer 9 as a photosensitive substrate at a reduced magnification based on light from the primary image I. A heat radiating plate 8 serving as a heat transfer member for preventing an increase in temperature of the image optical system K2 and the back surface reflecting mirror constituting the second image forming optical system K2.
And 1.

The first image forming optical system K1 includes, in order from the mask side, a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. ing.

Here, the first lens group G1 includes, in order from the mask side, a positive meniscus lens L11 having an aspherical convex surface facing the mask side and a positive meniscus lens L12 having an aspherical convex surface facing the mask side. And a positive meniscus lens L13 having an aspherical concave surface facing the wafer side.

The second lens group G2 includes, in order from the mask side, a biconcave lens L21 having an aspherical surface on the mask side and a biconvex lens L22 having an aspherical surface on the mask side. , A positive meniscus lens L23 having an aspherical convex surface facing the wafer side, and a positive meniscus lens L24 having an aspherical concave surface facing the wafer side.

The second imaging optical system K2 includes, in order from the mask side, a primary mirror M1 having a surface reflection surface R1 with a concave surface facing the wafer side and having an opening AP which is a light transmitting portion at the center.
A lens component L2, which is a refraction member, and an opening AP, which is provided on the lens surface on the wafer side and which is a light transmitting portion in the center.
And a secondary mirror M2 having a reflecting surface R2 having That is, according to another viewpoint, the sub-mirror M2 and the lens component L2 constitute a back surface reflection mirror, and the lens component L2 constitutes a refraction portion (refraction member) of the back surface reflection mirror.

Here, the lens component L2 constituting the refraction portion of the back reflector (M2, L2) is formed in a negative meniscus lens shape with the aspherical concave surface facing the mask side. The reflection surface R2 of the secondary mirror M2 is formed in a shape with the concave surface facing the mask side.

Note that all the optical elements (G1, G2, M1, M2) constituting the projection optical system 8 are arranged along a single optical axis AX. The primary mirror M1 is arranged near the position where the primary image I is formed, and the secondary mirror M2 is arranged close to the wafer 9.

In the present embodiment, all refractive optical members (lens components) constituting the projection optical system 8 are fluorite (C).
aF ₂ crystal). In addition, the back reflector (M
2, L2) is formed by applying an aluminum film to the back surface of the fluorite. The oscillation center wavelength of the F ₂ laser light as the exposure light is 157.6 nm.

The heat radiating plate 81 is a circular aluminum plate having an opening 81a formed at the center, and is attached so as to line the reflecting surface R2. That is, the heat sink 81 is
The back reflectors (M2, L2) are supported from the lower side of the wafer 9 in the lens barrel.
b and the reflection surface R2 have the same curvature, and the aluminum film formed on the back surface of the lens component L2 is in close contact with the support surface 81b. Thereby, the inside of the back reflector (M2, L2),
In particular, heat generated at the reflection surface R2 is transmitted through the aluminum film to the heat radiating plate 8.
1, the temperature of only the back reflector (M2, L2) rises compared to the surroundings, and the temperature distribution is formed inside the back reflector (M2, L2) easily. Can be prevented. The opening 81a is provided so as not to cover the opening AP of the reflection surface R2.

Here, the thermal conductivity of the heat sink 81 will be described. Since the lens component L2 constituting the back reflector is made of fluorite, its thermal conductivity is 10.3 Wm ^-1 K ^-1 . The heat conductivity of the aluminum heat sink 81 is 23
6 Wm ^-1 K ^-1 . The absorption due to backside reflection is about 10%, which is greater than the absorption due to transmission, which is about 1%. However, as described above, the heat conductivity of the heat radiating plate 81 is 10% higher than that of the lens component L2. Most of the heat generated by the back reflection of the lens component L2 is
It is transmitted to 1 and diverged.

The material of the radiating plate 81 to be backed may be any material having a higher thermal conductivity than the material of the lens component L2 (in this case, fluorite), and most metals satisfy this condition.

Further, in the main mirror M1 which is a reflecting mirror constituting the second imaging optical system K2, in order to prevent a temperature rise due to heat generated on the reflecting surface R1, a back reflecting mirror (M
2, L2), a heat transfer member may be attached to the primary mirror M1 so as to be lined from the mask 3 side in the same manner as the attachment of the heat sink 81 to L2).

As is clear from the above description, in the present embodiment, light from the pattern of the mask 3 is transmitted through the first imaging optical system K1 to the primary image (intermediate image) I of the mask pattern.
To form Light from the primary image I is reflected by the secondary mirror M2 via the central opening AP of the primary mirror M1 and the lens component L2, and light reflected by the secondary mirror M2 is reflected by the primary mirror M1 via the lens component L2. Is done. The light reflected by the primary mirror M1 forms a secondary image of the mask pattern on the surface of the wafer 9 at a reduced magnification through the lens component L2 and the central opening AP of the secondary mirror M2. At this time, the reflecting surface R2 of the secondary mirror M2 is
Since the heat radiating plate 81 having a higher thermal conductivity than that of the lens component L2, the heat generated on the reflecting surface R2, which is a rear reflecting surface that generates a relatively large amount of heat, is more likely to escape to the radiating plate 81 than the lens component L2. Therefore, thermal deformation and the like of the lens component L2 are reduced, and high-precision imaging can be performed. (Second Embodiment) Hereinafter, a projection exposure apparatus according to a second embodiment of the present invention will be described. The exposure apparatus of the present embodiment has a first
Since this is a modification of the projection exposure apparatus of the embodiment, the same portions are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 3 is a view for explaining the structure of the projection optical system 8 incorporated in the projection exposure apparatus of the second embodiment. Optical elements L11 to L11 to constitute the projection optical system 8
Although L13, L21 to L24, L2, M1, and M2 are the same as those in the first embodiment, a cooler 82 is further provided on the back surface of the heat radiating plate 81 which is in close contact with the back surface of the sub-mirror M2.

FIG. 4 is an enlarged view showing the periphery of the secondary mirror M2. As is clear from the figure, the heat radiating plate 81 lining the reflecting surface R2 is thinner than in the first embodiment, and a disc-shaped cooler 82 is attached to the back surface thereof. The cooler 82 is composed of a number of cooling elements such as a Peltier element, and cools the heat sink 81 from the back side. Since the cooler 82 has a built-in temperature monitor, even if the radiator plate 81 is heated, it can be quickly cooled to a desired temperature.

Also in the projection optical system of this embodiment, since the reflecting surface R2 of the sub-mirror M2 is lined with the heat radiating plate 81 having a higher thermal conductivity than the lens component L2, the reflecting surface of the back surface reflecting relatively large amount of heat is generated. The heat generated in R2 is easier to escape to the heat radiating plate 81 than the lens component L2. At this time, since the heat radiating plate 81 is always cooled to a constant temperature by the cooler 82, the temperature change of the lens component L2 is further reduced, and more accurate image formation becomes possible. (Third Embodiment) Hereinafter, a projection exposure apparatus according to a third embodiment of the present invention will be described. The exposure apparatus of the present embodiment also has the first
9 is a modification example of the projection exposure apparatus of the embodiment.

FIG. 5 is a view for explaining the structure of the projection optical system 8 incorporated in the projection exposure apparatus of the third embodiment. Optical elements L11 to L11 to constitute the projection optical system 8
L13, L21 to L24, M1, and M2 themselves are the same as those in the first embodiment, but a lens component L constituting a back reflector is provided.
Only the MgF ₂ single-layer coat is applied to the refraction surface RSa of the second mask 3 and the refraction surface RSb of the opening AP of the wafer 9. Furthermore, both refraction surfaces RSa, RS
In order to prevent the occurrence of flare due to unintended reflected light generated at b, a light shielding plate 8 is provided between the openings AP.
3 are arranged. The light shielding plate 83 is positioned and fixed with respect to the primary mirror M1 and the secondary mirror M2 by a linear support member extending from the lens barrel (not shown).

In this embodiment, as is apparent from the figure, the exposure light passes through the lens component L2 three times. In particular, when the light is transmitted through the refraction surface RSb on the wafer 9 side, the luminous flux is restricted. If it is assumed that the refraction surfaces RSa and RSb, which are the transmission surfaces of the front and back surfaces of the lens component L2, are provided with an anti-reflection coat having a large absorptance,
The absorption of the refraction surface RSa by the anti-reflection coat is three times that in the case of a single pass, and the refraction surface RSb generates heat at a relatively high surface density.

In order to prevent this, in the present embodiment, the two refraction surfaces RSa, RSb of the lens component L2, which is a refraction member, are used.
By applying only a single-layer coat of MgF _{2 to} the surface, absorption at both refraction surfaces RSa and RSb is minimized. However, if a single layer coating is applied to both refraction surfaces RSa and RSb, the amount of flare generated is slightly increased due to unintended reflected light. Therefore, a light-shielding plate 83 is arranged between the primary mirror M1 and the secondary mirror M2 to reduce flare. Avoid concentration. Such a light shielding plate 8
Reference numeral 3 also functions as a center shielding member required on the optical axis to block exposure light that travels straight without being reflected by the primary mirror M1 and the secondary mirror M2. (Fourth Embodiment) Hereinafter, a projection exposure apparatus according to a fourth embodiment of the present invention will be described. The exposure apparatus of the present embodiment also has the first
9 is a modification example of the projection exposure apparatus of the embodiment.

FIG. 6 is a view for explaining the structure of a projection optical system 8 incorporated in the projection exposure apparatus of the fourth embodiment. The projection optical system 8 includes a refraction-type first imaging optical system K1 for forming an intermediate image of the mask 3 and a final image of the mask 3 on the wafer 9 at a reduction magnification based on light from the intermediate image. A catadioptric second imaging optical system K2 to be formed and a lens barrel 85 for positioning and holding the first and second imaging optical systems K1 and K2 are provided. Then, the first imaging optical system K1
Are, in order from the mask 3 side, a first lens group G1 having a positive refractive power.
, An aperture stop S, and a second lens group G2 having a positive refractive power. The second imaging optical system K2 has a surface reflection surface R1 having a concave surface facing the wafer 9 side in order from the mask 3 side. A main mirror M1 having an opening AP in the center, a lens component L2 as a refraction member, and a sub-mirror provided on a lens surface of the wafer 9 side and having a reflection surface R2 having an opening AP in the center. M
And 2. Note that the sub-mirror M2 and the lens component L2 constitute a back surface reflecting mirror.

In the projection optical system shown in FIG. 6, the first lens group G1 includes, in order from the mask side, a positive meniscus lens L11 having an aspherical concave surface facing the mask side, and an aspherical convex surface facing the mask side. Positive meniscus lens L12 and negative meniscus lens L with an aspherical concave surface facing the mask side
13 and a positive meniscus lens L14 with the aspherical convex surface facing the mask side.

The second lens group G2 includes, in order from the mask side, a negative meniscus lens L21 having an aspherical concave surface facing the mask side, and a positive meniscus lens L22 having an aspherical concave surface facing the mask side. And a biconvex lens L23 having an aspherical surface on the mask side and a biconvex lens L24 having an aspherical surface on the wafer side.

Further, the lens component L2 constituting the refraction portion of the back reflector (M2, L2) is formed in a biconcave lens shape with the aspherical concave surface facing the mask side. Also,
The reflection surface R2 of the secondary mirror M2 is formed in a shape with the convex surface facing the mask side.

Here, each lens L11-L13, L21-L24
Is formed of fluorite as in the first to third embodiments. The lens component L2 is also made of fluorite. Further, the primary mirror M1 is made of titanium,
Is made of stainless steel.

Table 1 below shows values of specifications of the projection optical system of the projection exposure apparatus according to the fourth embodiment. In Table 1, λ represents the center wavelength of the exposure light, β represents the projection magnification, NA represents the image-side numerical aperture, and φ represents the diameter of the image circle on the wafer. The surface number indicates the order of the surface from the mask side along the direction in which light rays travel from the mask surface, which is the object surface, to the wafer surface, which is the image surface, and r indicates the radius of curvature of each surface (in the case of an aspheric surface, Indicates the radius of curvature of the vertex: mm), d indicates the on-axis interval of each surface, that is, the surface interval (mm), and n indicates the refractive index with respect to the center wavelength.

The sign of the surface distance d changes every time it is reflected. Therefore, the sign of the surface distance d is negative in the optical path from the back surface reflecting surface R2 to the front surface reflecting surface R1, and positive in other optical paths. And
Regardless of the incident direction of the light beam, the radius of curvature of the convex surface toward the mask side is positive, and the radius of curvature of the concave surface is negative.

The height of the aspheric surface in the direction perpendicular to the optical axis is defined as y, and the distance (sag amount) along the optical axis from the tangent plane at the vertex of the aspheric surface to a position on the aspheric surface at height y. )
Is z, the vertex radius of curvature is r, the cone coefficient is κ,
When the n-th order aspherical coefficient is C _n , the following equation (a)
It is represented by

Z = (y ² / r) / [1+ ｛1− (1 + κ) · y ² / r ² ｝ ^1/2 ] + C ₄ .y ⁴ + C ₆ .y ⁶ + C ₈ .y ⁸ + C ₁₀ .y _{^{10 + C 12 · y 12 +}} C 14 · y 14 ... (a) Note that the lens surface formed in an aspherical shape is provided with mark * on the right side of the surface number.

[0073]

[Table 1] (Main specifications) λ = 157.6 nm β = 0.2500 NA = 0.75 φ = 26.4 mm (optical member specifications) Surface number r dn (mask surface) 90.0000 1 * -1040.1889 16.8787 1.5600000 (Lens L11) 2 -284.5252 441.0860 3 * 248.9993 31.6042 1.5600000 (Lens L12) 4 1868.1161 86.0264 5 * -256.4757 15.0000 1.5600000 (Lens L13) 6 -1079.5886 1.0001 7 * 160.4237 39.0505 1.5600000 (Lens L14) 8 1268.4783 3.7000 9 ∞ 70.0471 (Aperture stop S) 10 * -129.2757 15.0000 1.5600000 (Lens L21) 11 -277.5549 78.6066 12 * -1494.7189 45.0000 1.5600000 (Lens L22) 13 -238.2212 91.8347 14 * 365.9254 18.9298 1.5600000 (Lens L23) 15 -701.6534 129.1513 16 4243.7172 16.9695 1.5600000 (Lens L24) 17 * -216.4772 290.1728 18 * -2125.3388 59.9425 1.5600000 (Lens component L2) 19 5996.9618 -59.9425 1.5600000 (Back reflection surface R2) 20 * -2125.3388 -230.3293 21 350.1412 230.3293 1.5600000 (Surface) Reflecting surface R1) 22 * -2125.3388 59.9425 1.5600000 (lens component L2) 23 5,996.9618 10.0000 (wafer surface) (Aspherical Data) r kappa C ₄ 1 surface _{^{-1040.1889 0.00000 8.50114 × 10 -9 C 6}} C 8 C 10 9.40854 × 10 ^-14 3.85092 × 10 ^-18 -5.46679 × 10 ^-22 C ₁₂ C ₁₄ 0.00000 0.0000 0 r κ C ₄ 3 248.9993 0.00000 -1.42904 × 10 ^-10 C ₆ C ₈ C ₁₀ 6.60616 × 10 ^-14 3.65786 × 10 ^{-18 _{-1.09842 × 10 -22 C 12 C 14}} 4.97484 × 10 -27 0.00000 r κ C 4 5 faces _{^{-256.4757 0.00000 5.80903 × 10 -9 C 6}} C 8 C 10 1.21604 × 10 -13 1.20391 × 10 -17 1.45440 × 10 - ²² C ₁₂ C ₁₄ 6.87071 × 10 ^-27 0.00000 rκC ₄ 7 side 160.4237 0.00000 -6.83384 × 10 ^-9 C ₆ C ₈ C ₁₀ 5.93636 × 10 ^-13 6.46685 × 10 ^-18 5.93586 × 10 ^-22 C ₁₂ C ₁₄ ^{9.08641 × 10 -26 0.00000 r κ C} 4 10 faces _{^{-129.2757 0.00000 -1.19158 × 10 -8 C 6}} C 8 C 10 5.20234 × 10 -12 1.68410 × 10 -16 6.16591 × 10 -21 C 12 C 14 -3.28458 × 10 ^-25 0.00000 r ^κ C ₄ 12 faces -1494.7189 0.00000 3.04547 × 10 ^-8 C _{6 ^{8 C 10 -2.21766 × 10 -12 1.10527}} × 10 -16 -3.25713 × 10 -21 C 12 C 14 1.29445 × 10 -25 0.00000 r κ C 4 14 faces _{^{365.9254 0.00000 -3.76800 × 10 -8 C 6}} C 8 C 10 1.05958 × 10 ^-13 -2.08225 × 10 ^-17 1.53887 × 10 ^-21 C ₁₂ C ₁₄ -1.62147 × 10 ^-25 0.00000 r κ C ₄ 17 side -216.4772 0.00000 1.07160 × 10 ^-8 C ₆ C ₈ C ₁₀ -1.20868 × 10 ^-13 -2.81385 × 10 ^-18 2.81683 × 10 ^-21 C ₁₂ C ₁₄ 0.00000 0.00000 r κ C ₄ 18 planes -2125.3388 91.723346 5.77862 × 10 ^-10 20 planes C ₆ C ₈ C ₁₀ 22 planes -2.56941 × 10 ^-14 1.81191 × 10 ^-18 -4.17947 × 10 ^-23 C ₁₂ C ₁₄ 1.10317 × 10 ^-27 -1.11337 × 10 ^-32 Below, means for avoiding non-uniform temperature distribution occurring in the lens component L2 will be described. In the rear-surface reflecting mirror composed of the lens component L2 and the sub-mirror M2, there are a transmitted light beam and a reflected light beam, the transmitted light beam passes through the inner optical axis portion with the opening AP as a boundary, and the reflected light beam passes through the opening AP. Pass outside as In this case, if the surface density of the transmitted light is significantly higher than the surface density of the reflected light, only the temperature near the optical axis at which the transmitted light is absorbed rises, and the refractive index becomes uneven, which is not preferable.
In order to prevent this, the surface density of the transmitted light on the transmission surface may be set so as not to be significantly higher than the surface density of the reflected light on the reflection surface.

Here, the effective radius of the lens component L2 when entering the reflecting surface R2 is φ1, the absorptance is S1, and the effective radius when entering the transmitting surface corresponding to the opening AP is φ
2, and the absorption rate S2. Further, immediately before the reflection, the lens component L
The total amount of energy incident on the 2 and E1, when the incident plane is assumed to be substantially circular, surface density DR of the heat generated on the reflecting surface R2 is, DR = E1 × S1 / π and (φ1 ² -φ2 ²⁾ Become. The surface density DT of heat generated transmission surface corresponding to the opening AP is the total amount of energy incident on the immediately preceding transmission lens component L2 becomes DT = E2 × S2 / πφ2 ² as E2. Here, although there is a slight difference due to absorption in the middle, it can be considered that E1 ≒ E2. Therefore, the surface density DT of heat generation in the transmission surface corresponding to the opening AP is equal to the reflection surface R.
Conditions that do not significantly larger than the surface density DR of heat generation in the 2 as ^{DT <3DR, S2 / φ2 2} <3S1 / (φ1 2 -φ2 2) if (1) the relationship is satisfied, the reflecting surface R2 and the opening The average heat value of the surface of the AP and that of the transmission surface is substantially the same, and it is possible to prevent the lens component L2 from having an uneven temperature distribution.

In the optical system of the above embodiment, the effective radius φ1 of the reflecting surface R2 is 125 mm, and the effective radius φ2 of the opening AP is 2 mm.
6 mm. The absorptance S1 at the time of reflection is 10%, and the absorptance at the time of transmission is 1%. Therefore, 3 related to the reflection surface
^{S1 / (φ1 2 -φ2 2)} = 1/49830 , and the become S2 / φ2 ² = 1/67600 relates to a transmission surface, satisfy the relationship (1).

Next, a description will be given of a means for reducing the influence of a temperature rise that occurs in the entire projection optical system 8 including the lens component L2 and the like on the image forming state.

When the temperature of the entire projection optical system 8 changes,
If all the elements constituting the projection optical system 8 expand or contract at the same ratio, the imaging characteristics of the projection optical system 8 do not change even if the imaging position shifts. Specifically, when the coefficient of thermal expansion (dL / L) / dT of the lens barrel 85 in which the projection optical system 8 is assembled is α, at least one or all of the optical elements, in particular, the material forming the reflecting mirror If the expansion coefficient β satisfies α / 3 <β <3α, α ≒ β (2), it is considered that aberration fluctuation due to temperature change becomes relatively small.

In general, when the temperature of the entire projection optical system changes, the effect that the lens barrel itself holding the refracting member expands, the effect that the refractive index changes due to the temperature change of the refracting member, and the effect that the refracting member expands and the shape thereof expands May be affected.
Therefore, in the refractive optical system, these elements are combined to generate aberration. However, in the catadioptric optical system as in the present embodiment, the reflection surface often determines the magnification. In such an optical system, the influence of the refraction member is smaller than that of the reflection surface, and the influence of the temperature change is largely determined by the reflection surface and the lens barrel. In such a case, if the expansion rates of the lens barrel material and the reflecting mirror material are close to each other, the projection optical system will only expand to the whole even if the temperature changes as a whole,
If only the object position and the image position are adjusted, almost no aberration occurs. However, since the lens barrel material itself is desirably strong, the material is limited.

From the above considerations, the expansion rate of the material forming the primary mirror M1 (preferably the primary mirror M1 and the lens component L2) is set so that the expansion rate of the material forming the lens barrel 85 is satisfied so as to satisfy the above conditional expression (2). If the material is selected so as to be close to the ratio, the variation in aberration due to temperature is reduced. If the above condition (2) is not satisfied, the difference in expansion coefficient between the reflecting member and the lens barrel member is greatly different, so that a larger aberration is generated with a change in temperature.

More preferably, if the expansion coefficient β of the material forming the reflecting mirror satisfies the condition of α / 2 <β <2, α ≒ β (3), temperature fluctuation is further reduced, which is preferable.

In the optical system of the above embodiment, the lens barrel 85 is made of stainless steel and has a linear expansion coefficient of 14.7 pp.
m / K. On the other hand, the primary mirror M1 is made of titanium,
An aluminum film is deposited for reflection. Here, the linear expansion coefficient of titanium is 8.6 ppm / K, and the above conditional expression (2)
Meets. Accordingly, even when the temperature of the entire projection optical system 8 changes, the generated aberration fluctuation can be reduced. The lens component L2 constituting the back reflector is fluorite, and has a linear expansion coefficient of 19 ppm / K).
This also satisfies conditional expression (2), but in the projection optical system 8 of this embodiment, since the magnification is mostly determined by the primary mirror M1, the effect of the temperature change of the lens component L2 is compared with that of the primary mirror M1. And small

The projection exposure apparatuses of the first to fourth embodiments can be manufactured by the following method.

First, an illumination optical system 2 for illuminating a pattern on the mask 3 with illumination light having a center wavelength shorter than 180 nm is prepared. Specifically, for example, the center wavelength is prepared an illumination optical system 2 for illuminating a mask pattern using an F ₂ laser light 157.6 nm. At this time, the illumination optical system 2 is configured to supply illumination light having a spectrum width within a predetermined full width at half maximum.

Next, a projection optical system 8 for preparing an image of the pattern on the mask on the photosensitive surface on the photosensitive substrate is prepared. Preparing the projection optical system 8 includes preparing a plurality of refractive optical elements and reflecting mirrors and assembling the plurality of refractive optical elements and the like. And
By electrically, mechanically, or optically connecting the illumination optical system 2 and the projection optical system 8 to achieve the above-described functions, the projection exposure apparatus according to each embodiment can be manufactured.

[0085] In the embodiments described above, the use of the fluorite i.e. CaF ₂ (calcium fluoride) as the material of refractive optical members constituting the projection optical system, in addition to the CaF _2, Alternatively, instead of CaF ₂ , a crystal material of fluoride such as barium fluoride, lithium fluoride, and magnesium fluoride, or quartz doped with fluorine may be used. However, it is preferable that the projection optical system be composed of a single type of optical material if the band width of illumination light for illuminating the mask can be sufficiently reduced. Furthermore, considering the ease of manufacturing and the manufacturing cost of the projection optical system, it is preferable that the projection optical system be composed of only CaF ₂ . The material of the refractive optical member can be selected in consideration of the coefficient of linear expansion.

Further, in each of the above-described embodiments, the F ₂ laser is used as the light source 1 and the spectrum width is narrowed by the band narrowing device. Alternatively, a YAG laser having an oscillation spectrum at 157 nm is used. May be used. In addition, a single-wavelength laser beam in the infrared or visible region oscillated from a DFB semiconductor laser or a fiber laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and ytterbium) to form a nonlinear optical crystal. Alternatively, a harmonic converted to ultraviolet light may be used. As the single wavelength oscillation laser, for example, an ytterbium-doped fiber laser is used.

As described above, when using a harmonic from a laser light source, the harmonic itself has a sufficiently narrowed spectrum width (for example, about 0.01 pm).
It can be used in place of the light source 1 of each of the above embodiments.

According to the present invention, after the mask pattern image is collectively transferred to one shot area on the wafer, the wafer is sequentially and two-dimensionally moved in a plane orthogonal to the optical axis of the projection optical system 8. Or a step-and-repeat method (batch exposure method) in which the process of collectively transferring the mask pattern image to the next shot area is performed, or the mask and the wafer are transferred to the projection optical system 8 when exposing each shot area of the wafer. On the other hand, the present invention can be applied to both a step-and-scan method (scanning exposure method) in which synchronous scanning is performed with the projection magnification β as a speed ratio. In the step-and-scan method, it is only necessary to obtain good imaging characteristics in a slit-shaped (elongated rectangular) exposure area, so that the projection optical system 8 can be wider on the wafer without increasing the size. Exposure can be performed on the shot area.

Next, an example of the operation when forming a predetermined circuit pattern on a wafer by the step-and-scan method using the projection exposure apparatus of the first to fourth embodiments will be described with reference to the flowchart of FIG. I will explain. First, in step S1 of FIG. 7, a metal film is deposited on one lot of wafers. In step S2, a photoresist is applied to the metal film on the wafer 9 of the lot. Thereafter, in step S3, using the projection exposure apparatus of FIG. 1 including the projection optical system 8 of the first to fourth embodiments, the image of the pattern on the reticle 3 Exposure transfer is sequentially performed on each shot area on the wafer 9 of the lot. Then, in step S4,
After the development of the photoresist on the one lot wafer 9 is performed, in step S5, etching is performed on the one lot wafer 9 using the resist pattern as a mask, thereby forming a circuit corresponding to the pattern on the reticle R. A pattern is formed in each shot area on each wafer. Thereafter, a device such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer and the like.

In each of the above embodiments, the present invention is applied to a projection exposure apparatus used for manufacturing a semiconductor device. However, not only an exposure apparatus used for manufacturing a semiconductor element, but also an exposure apparatus used for manufacturing a display including a liquid crystal display element and the like, an exposure apparatus for transferring a device pattern onto a glass plate, and a device used for manufacturing a thin film magnetic head The present invention can also be applied to an exposure apparatus that transfers a pattern onto a ceramic wafer, an exposure apparatus used for manufacturing an image pickup device (such as a CCD), and the like. Further, the present invention can be applied to an exposure apparatus that transfers a circuit pattern onto a glass substrate, a silicon wafer, or the like in order to manufacture a reticle or a mask. (Fifth Embodiment) Hereinafter, a projection exposure apparatus according to a fifth embodiment of the present invention will be described.

FIG. 8 schematically shows a projection exposure apparatus according to the fifth embodiment. This projection exposure apparatus uses radiation light (EUV light) in the soft X-ray region as exposure light, and uses a reflection optical system having only a reflection surface as a projection optical system.

In FIG. 8, an illumination system 40 including an EUV light source for supplying, for example, 13 nm radiation, a reticle stage system 50 for holding the reticle R, and an image of the reticle R are placed in a clean room on the floor F. A projection exposure apparatus having a projection optical system 60 for projecting a reduced image thereon and a wafer stage system 70 for holding a wafer W is provided.

To support this projection exposure apparatus, a floor F
The columns 30A and 30B and the column 31 are fixed on the upper side. The upper part of both columns 30A and 30B is a ceiling plate 30C.
Are linked by The illumination system 40 is supported by the column 31. The ceiling plate 30C connected to the upper portions of the columns 30A and 30B supports a reticle stage base (not shown), and the reticle stage system 50 is mounted on the reticle stage base so that the reticle stage system 50 can move in the X direction in the drawing. Is placed.

The support plate 32 connected to the lower portion of the center between the columns 30A and 30B has an opening at the center.
The projection optical system 60 is supported in an opening of the support plate 32 via a flange 61 a provided on a lens barrel 61 of the projection optical system 60.

The wafer surface plate 71 on which the wafer stage system 70 is mounted is connected to the support plate 32 via arms 72A and 72B. The wafer stage system 70 is also movable along the X direction in the figure.

The projection optical system 60 has four mirrors M51 to M54 arranged along the optical axis AX, and these mirrors M51 to M54 are mirror holding members 62A to 62D.
Respectively. And each mirror M51-
In order to position the M54 in the direction of the optical axis AX, spacers 63A to 63E for determining the intervals between the mirror holding members 62A to 62D are provided. Inside the lens barrel 61, mirror holding members 62A to 62D and spacers 63A to 63E are alternately stacked.

The overall operation of the projection exposure apparatus will be described. EUV light from the illumination system 40 is incident on a reticle R scanned by the reticle stage system 50. The reflected light from the reticle R enters the projection optical system 60, enters the wafer W via mirrors M51 to M54, and
Is projected on the wafer W. At this time, the wafer stage system 70 is also scanned in synchronization with the scanning of the reticle R, and scanning exposure becomes possible.

In this embodiment, each of the mirrors M51 to M
Numeral 54 is made of, for example, beryllium,
1. Mirror holding members 62A to 62D and spacer 63
A to 63E are formed of, for example, brass.

The reticle R is indirectly positioned in the optical axis AX direction by supporting the reticle stage system 50, and the optical axis of the wafer W is indirectly supported by supporting the wafer stage system 70. Columns 30A, 30B, ceiling plate 30 for positioning in the AX direction
C, the support plate 32, and the arms 72A and 72B are formed of, for example, stainless steel.

Here, the linear expansion coefficient of beryllium, which is the material of the mirrors M51 to M54, is 11.3 ppm / K. The linear expansion coefficient of brass, which is a material of members such as the lens barrel 61 for positioning the mirrors M51 to M54 in the optical axis AX direction, is 17.5 ppm / K. Further, the linear expansion coefficient of stainless steel, which is a material of members such as the columns 30A and 30B for positioning the reticle R and the wafer W in the optical axis AX direction, is 14.7 ppm / K.

That is, although the materials of the mirrors M51 to M54 are different from the materials of the lens barrel 61 and the like, they satisfy the conditional expressions (2) and (3) described in the fourth embodiment. The accompanying aberration fluctuation can be reduced.

The columns 30A and 30B for positioning the reticle R and the wafer W also satisfy the conditional expressions (2) and (3). This makes it possible to easily reduce aberration fluctuations due to temperature changes without moving the object-image distance by the reticle stage system 50 or the wafer stage system 70.

In the above description, the materials of the mirrors M51 to M54, the material of the lens barrel 61 and the like, and the materials of the columns 30A and 30B and the like all satisfy the conditional expressions (2) and (3). However, the materials of the mirrors M51 to M54 and the materials of the members such as the lens barrel 61 for positioning the mirrors M51 to M54 in the optical axis AX direction do not satisfy the conditional expressions (2) and (3). It can also be. In this case, a temperature sensor for detecting temperature fluctuations of the mirrors M51 to M54 is provided in the projection optical system 60, and at least one of the reticle stage system 50 and the wafer stage system 70 is driven based on output data of the temperature sensor,
The distance between the object and the image is changed to a distance that can reduce the variation in aberration. Also with this configuration, it is possible to reduce aberration fluctuation due to temperature change.

(Sixth Embodiment) FIG. 9 shows a back mirror (M2, L2) of a projection optical system of a projection exposure apparatus according to a sixth embodiment.
It is the figure which expanded the periphery of. In the sixth embodiment, a heat transfer member H is arranged along the shape of the back mirror (M2, L2) at a distance of 3 mm from the reflection surface of the back mirror (M2, L2). The curvature of the heat transfer member H and the back mirror (M2, L
It is not necessary that the curvature of the reflecting surface in 2) completely match, and the distance between the back mirror (M2, L2) and the heat transfer member H is 30 on the entire surface.
mm. The back mirror (M2, L2) is formed of fluorite since the exposure light of 157 nm is used in this embodiment. The heat transfer member H is preferably made of a material having good thermal conductivity, for example, brass, an aluminum alloy, a titanium alloy, or the like. In the present embodiment, brass is used. The heat transfer member H is further connected to a member having a high thermal conductivity and a large heat capacity, such as a body (not shown), so that the temperature of the heat transfer member itself does not increase. In addition, the back mirror (M2, L
The space between 2) and the heat transfer member H is preferably filled with a gas having good heat conductivity, for example, helium (He).

(Seventh Embodiment) FIG. 10 is an enlarged view of the periphery of a reflecting mirror M1 of a projection optical system of a projection exposure apparatus according to a seventh embodiment. In the seventh embodiment, a heat transfer member H is arranged on the back side of the reflecting mirror M1 at a distance of 5 mm substantially along the shape of the reflecting mirror M1. Note that the curvature of the heat transfer member H and the curvature of the reflection surface of the back mirror M1 do not need to completely match, and it is sufficient that the distance between the reflection mirror M1 and the heat transfer member H be within 30 mm over the entire surface. The exposure light of this embodiment has a wavelength of 157 nm, and BK7 is used as a material of the reflecting mirror because of its compatibility with the reflecting film. As the heat transfer member H, a member having good heat conductivity is preferable, and in the present embodiment, stainless steel is used. The heat transfer member H is further connected to a not-shown forced cooling means, for example, a water-cooled cooler or the like, so that the temperature of the heat transfer member itself does not rise. The space between the back mirror M1 and the heat transfer member H is filled with high-purity nitrogen.

(Eighth Embodiment) FIG. 11 shows an eighth embodiment of the present invention.
1 is an overall schematic diagram of a projection exposure apparatus according to an embodiment.
The eighth embodiment is a modification of the first embodiment. In FIG. 11, a projection optical system is a catadioptric first catadioptric type that forms an intermediate image of a pattern on a reticle R as a projection original plate.
It has an imaging optical system K1 and a refraction-type second imaging optical system K2 for re-imaging an image of an intermediate image by the first imaging optical system K1 on a wafer W as a work.

In the optical path between the reticle R and the first imaging optical system K1, a reflecting mirror M1 for bending the optical path for deflecting the optical path by 90 ° is arranged. In the optical path between K1 and the second imaging optical system K2, that is, in the vicinity of the intermediate image, an optical path bending reflecting mirror M2 for deflecting the optical path by 90 ° is arranged. These reflecting mirrors M1 and M2 are provided on the optical path bending member 91.

The first imaging optical system K1 has an optical axis Ax2.
Lens components and concave mirror CM arranged along
And forms an intermediate image at approximately the same magnification or slightly reduced magnification. The second imaging optical system K2 has an optical axis Ax2
A plurality of lens components and a variable aperture stop AS for controlling a coherence factor, which are arranged along an optical axis Ax3 orthogonal to the optical axis Ax3. An image of the image, ie, a secondary image, is formed.

The optical axis Ax2 of the first imaging optical system K1 is bent by 90 ° by the optical path bending reflecting mirror M1 to define the optical axis Ax1 between the reticle R and the reflecting mirror M1. In the present embodiment, the optical axis Ax1 and the optical axis Ax3 are parallel to each other, but do not coincide with each other.

In the projection optical system of the eighth embodiment, one or more lens components may be arranged along the optical axis Ax1. Further, the optical axis Ax1 and the optical axis Ax3 may be arranged so as to coincide with each other. Also, the optical axis Ax1
And the optical axis Ax2 may be an angle different from 90 °, preferably an angle obtained by rotating the concave reflecting mirror CM counterclockwise. At this time, it is preferable to set the bending angle of the optical axis at the reflecting mirror M2 so that the reticle R and the wafer W are parallel.

In the eighth embodiment, the heat radiating plate 92 is attached to the back side of the concave mirror CM,
The reflecting mirrors M1 and M2 are mounted thereon. The heat generated by the concave mirror CM and the reflecting mirrors M1 and M2 can be released through the heat radiating member 91 and the heat radiating plate 92. Accordingly, thermal deformation of the concave mirror CM and the reflecting mirrors M1 and M2 is reduced, and high-precision exposure can be performed.

(Ninth Embodiment) FIG. 12 shows a ninth embodiment of the present invention.
1 is an overall schematic diagram of a projection exposure apparatus according to an embodiment.
The ninth embodiment is a modification of the first embodiment.

In FIG. 12, a projection optical system includes a catadioptric first imaging optical system K1 for forming an intermediate image of a pattern on a reticle R as a projection original plate, and a first imaging optical system K1.
And a refraction-type second imaging optical system K2 for re-imaging the image of the intermediate image on the wafer W as a work. Here, in an optical path between the first imaging optical system K1 and the second imaging optical system, an optical path bending member (reflecting mirror) having an optical path bending reflecting surface for deflecting the optical path by 90 °. ) M
1 and an optical path bending member (reflecting mirror) M2 provided with an optical path bending reflecting surface for deflecting the optical path by 90 °.

The first image forming optical system K1 has a plurality of lens components and a concave mirror CM arranged along the optical axis Ax1, and converts the intermediate image of the reticle R into a first image at approximately the same magnification or slightly reduced magnification. It is formed near the reflecting mirror 1 as an optical path bending mirror. The second imaging optical system has a plurality of lens components arranged along the optical axis Ax3, and forms an image of the intermediate image (secondary image) on the wafer W based on light from the intermediate image. It is formed at a reduced magnification. Here, since the reflecting mirror M1 and the reflecting mirror M2 are arranged at an angle so as to be orthogonal to each other, the optical axes Ax1 and Ax3 of the first and second imaging optical systems K1 and K2 are parallel to each other, and the reticle R and the reticle R are parallel to each other. The wafers W are also parallel to each other.

In the ninth embodiment, one or more lens components may be arranged along the optical axis Ax2 in the optical path between the reflecting mirrors M1 and M2 for bending the optical path.

In the ninth embodiment, the heat radiating plate 92 is attached to each of the reflecting mirrors M1 and M2, and the heat generated by the reflecting mirrors M1 and M2 can be released through the heat radiating plate 92. . Thereby, the reflecting mirrors M1, M
2 reduces thermal deformation and the like, and enables highly accurate exposure.

(Tenth Embodiment) FIG. 13 is an overall schematic view of a projection exposure apparatus according to a tenth embodiment of the present invention. The tenth embodiment is a modification of the sixth embodiment.

In FIG. 13, a projection optical system includes a refraction-type first imaging optical system K1 for forming an intermediate image of a pattern on a reticle R as a projection original plate, and an intermediate image formed by the first imaging optical system K1. A catadioptric second for re-imaging an image (secondary image)
A third type of refraction type that re-images a secondary image formed by the imaging optical system K2 and the second imaging optical system K2 on a wafer W as a workpiece.
And an imaging optical system K3. Here, in the optical path between the first imaging optical system K1 and the second imaging optical system K2, an optical path bending reflecting mirror M1 for deflecting the optical path by 90 ° is disposed. In the optical path between the second imaging optical system K2 and the third imaging optical system K3, there is disposed an optical path bending reflecting mirror M2 for deflecting the optical path by 90 °.

Here, 30 minutes from the back surfaces of the reflecting mirrors M1 and M2.
The heat dissipating member 91 is arranged at a position within mm, and the space between the reflecting mirrors M1 and M2 and the heat dissipating member 91 is
Helium gas is flowing at a predetermined flow rate and flow rate.

The first image forming optical system K1 has an optical axis Ax1.
, And forms an intermediate image at a reduction ratio of about 1 / 1.5 to 1/3. The second imaging optical system K2 has one or a plurality of lens components and a concave mirror CM arranged along the optical axis Ax2. An image (secondary image) of the image is formed.

Here, a heat radiating plate 92 is disposed at a position within 30 mm from the back surface of the concave mirror CM, and a space between the reflecting mirror CM and the heat radiating plate 92 is provided with a helium gas having a predetermined flow rate and flow rate. And shed.

The third image forming optical system K3 has an optical axis Ax
3 has a plurality of lens components arranged along,
At a reduction ratio of about 1 / 1.5 to 1/3, the first
And forming a secondary image (tertiary image) on the wafer W by the second imaging optical systems K1 and K2.

In the tenth embodiment, the optical axis Ax1 and the optical axis A
x3 coincides with each other, but the optical axis Ax1 and the optical axis Ax
3 may be parallel and disagree with each other, and the optical axis Ax2 may not be orthogonal to the optical axis Ax1 or Ax3.

In the tenth embodiment, the reflecting mirror M1,
Space between M2 and heat radiating member 91 and concave mirror CM and heat radiating plate 9
2 is filled with helium gas as a gas having good thermal conductivity, the heat generated by the reflecting mirrors M1 and M2 and the concave mirror CM is transmitted to the heat radiating member 91 and the heat radiating plate 92 via the helium gas. It is possible to escape. Thus, thermal deformation and the like of the reflecting mirrors M1 and M2 and the concave mirror CM are reduced, and highly accurate exposure can be performed.

In the eighth to tenth embodiments, the cooler 82 of the second embodiment may be attached to the heat radiating member 91 and the heat radiating plate 92.

[0126]

As is clear from the above description, according to the first projection exposure apparatus of the present invention, the heat transfer member including a material having a higher thermal conductivity than the member including the reflection surface is provided with the heat transfer member. Since the member including the reflection surface is disposed in contact with the outside of the effective reflection region of the reflection surface, heat generated on the reflection surface by the incidence of the exposure light can be easily radiated to the outside of the member including the reflection surface. Therefore, heat can be prevented from accumulating inside the member including the reflection surface, and high-precision exposure with reduced aberration variation can be performed.

According to the second projection exposure apparatus, in the refraction member disposed between the first and second reflection surfaces, the exposure light passes multiple times between the first and second reflection surfaces. I do.
At this time, at least one surface of the refraction member disposed between the first and second reflection surfaces is not coated,
Alternatively, since the coating is provided with three or less layers, absorption on the transmission surface of the refraction member can be minimized. Thereby, heat accumulation in the refraction member can be prevented, and high-precision exposure with reduced aberration fluctuations can be performed.

Further, according to the third projection exposure apparatus, the first
Exposure light emitted from the surface is incident on the first reflection surface via the second light transmission portion, is reflected on the first reflection surface, is further reflected on the second reflection surface, passes through the first light transmission portion, and passes through the first light transmission portion. It is led to two sides. At this time, since the above-mentioned conditional expression (1) is satisfied on the first reflecting surface or the second reflecting surface, absorption of the exposure light between the reflecting surface and the transmitting surface, that is, the calorific value is balanced to some extent. Therefore, it is possible to prevent the transmission member from being locally heated and to cause non-uniform aberration fluctuation, thereby enabling high-precision exposure.

Further, according to the fourth projection exposure apparatus, since the expansion coefficient β of at least one of the materials forming the reflecting mirror satisfies the conditional expression (2), the expansion coefficient of the reflecting mirror and the lens barrel is large. Can be substantially matched. In other words, even if the focal length changes due to the heat generated by the reflecting mirror, the size of the lens barrel changes accordingly, so that the fluctuation of the imaging state of the projection optical system can be suppressed, and high-precision exposure is possible. Becomes

Further, according to the projection exposure method of the present invention, since the first to fourth projection exposure apparatuses are used, fluctuations in aberrations of the projection optical system and fluctuations in the image formation state can be suppressed, and high-precision exposure can be performed. Becomes possible. Further, according to the fifth projection exposure apparatus, since the heat generated in the optical member including the reflection surface can be released to the heat transfer member via the predetermined gas, the heat of the optical member including the reflection surface can be reduced. Deformation can be reduced, and high-precision exposure can be performed. Further, according to the projection exposure method of the present invention, since the fifth projection exposure apparatus is used, variation in aberration of the projection optical system and variation in the image formation state can be suppressed, and high-precision exposure can be performed.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an overall configuration of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 shows a projection optical system of the projection exposure apparatus according to the first embodiment.

FIG. 3 shows a projection optical system of a projection exposure apparatus according to a second embodiment.

FIG. 4 is a diagram illustrating a main part of the projection optical system of FIG. 3;

FIG. 5 shows a projection optical system of a projection exposure apparatus according to a third embodiment.

FIG. 6 shows a projection optical system of a projection exposure apparatus according to a fourth embodiment.

FIG. 7 is a flowchart illustrating an example of an operation when a predetermined circuit pattern is formed using the projection exposure apparatus according to the first to fourth embodiments.

FIG. 8 shows a projection optical system of a projection exposure apparatus according to a fifth embodiment.

FIG. 9 is a diagram showing a main part of a projection optical system of a projection exposure apparatus according to a sixth embodiment.

FIG. 10 is a diagram showing a main part of a projection optical system of a projection exposure apparatus according to a seventh embodiment.

FIG. 11 is an overall schematic view of a projection exposure apparatus according to an eighth embodiment.

FIG. 12 is an overall schematic diagram of a projection exposure apparatus according to a ninth embodiment.

FIG. 13 is an overall schematic diagram of a projection exposure apparatus according to a tenth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Illumination optical system 3 Mask 8 Projection optical system 9 Wafer 61 Barrel 62A-62D Mirror holding member 81 Heat radiator 82 Cooler 83 Shielding plate 85 Barrel H Heat transfer member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 17/08 H01L 21/30 515D G03F 7/22 G02B 7/18 Z H01L 21/30 517

Claims (11)

[Claims] 1. A projection exposure apparatus including a catadioptric optical system that forms an image on a first surface on a second surface, wherein the catadioptric optical system has a member including a reflective surface, and the reflective surface A projection exposure apparatus comprising: a heat transfer member that includes a material having a higher thermal conductivity than a member that includes: and a heat transfer member that is disposed in contact with the member that includes the reflection surface. 2. The projection exposure apparatus according to claim 1, wherein the heat transfer member is in contact with a member including the reflection surface outside an effective reflection area of the reflection surface. 3. The projection exposure apparatus according to claim 1, further comprising forced cooling means connected to said heat transfer member. 4. The projection exposure apparatus according to claim 1, wherein the member including the reflection surface is a member including a refraction surface. 5. The catadioptric optical system has first and second reflecting surfaces which are disposed opposite to each other as the reflecting surface, and the first and second reflecting surfaces have at least one luminous flux at a central portion. A first and a second light transmitting portion capable of partially transmitting the light, respectively, and at least one of the first and second reflecting surfaces is included in a member including the reflecting surface. The projection exposure apparatus according to any one of claims 1 to 4. 6. A projection exposure apparatus provided with a catadioptric optical system for forming an image on a first surface on a second surface, wherein the catadioptric optical system is arranged so as to oppose first and second reflections. And a refraction member disposed between the first and second reflection surfaces. At least one surface of the refraction member is uncoated or has three or less coats. A projection exposure apparatus characterized in that the projection exposure apparatus is one of: 7. At least one of the first and second reflecting surfaces has a positive power, and the first and second reflecting surfaces are:
A central portion has first and second light transmitting portions each capable of transmitting at least a part of a light beam, and a part of a space between the first and second light transmitting portions is provided to the catadioptric system. 7. The projection exposure apparatus according to claim 6, further comprising a light shielding plate for absorbing the incident light beam. 8. A projection exposure apparatus comprising a catadioptric optical system for forming an image on a first surface on a second surface, wherein the catadioptric optical system has first and second reflecting surfaces, and 1
And at least one of the second reflecting surface has a positive power,
The first and second reflecting surfaces have first and second light transmitting portions each capable of transmitting at least a part of a light flux at a central portion, and at least one of the first and second reflecting surfaces is provided. , Formed on the end face of the transmission member, the effective diameter when incident on the reflection surface formed on the end face of the transmission member is φ1, the absorptance is S1, the reflection surface formed on the end face of the transmission member, the effective diameter .phi.2 when to be incident on the transmission surface in contact, when the absorption rate ^{S2, S2 / φ2 2 <3S1} / (φ1 2 -φ2 2) satisfy the conditions projection exposure apparatus according to claim of. 9. A projection exposure apparatus including a projection optical system that forms an image of a first surface on a second surface, wherein the projection optical system has at least one reflecting mirror, When the thermal expansion coefficient (dL / L) / dT of the lens barrel is α, the expansion coefficient β of at least one of the materials forming the reflecting mirror is α / 3 <β <3α, α ≠ β. A projection exposure apparatus characterized by satisfying the following. 10. A projection exposure method using the projection exposure apparatus according to any one of claims 1 to 9, wherein: a step of generating illumination light; Arranging on the surface and illuminating with the illumination light; and using the catadioptric system, the image of the predetermined pattern of the mask arranged on the first surface is arranged on the second surface. Projecting onto a photosensitive substrate. 11. A projection exposure apparatus including a projection optical system for forming an image on a first surface on a second surface, wherein the projection optical system is a reflective optical member having a reflective surface or a refraction including a reflective surface. A heat transfer member disposed along the optical member at a position opposite to the direction in which light is reflected on the reflection surface and within 30 mm from the optical member. A projection exposure apparatus, wherein at least a part between the heat transfer member and the reflection surface is filled with a predetermined gas.