WO2003040785A1

WO2003040785A1 - Optical element, method of manufacturing the optical element, optical system, exposure device, and method of manufacturing micro device

Info

Publication number: WO2003040785A1
Application number: PCT/JP2002/011478
Authority: WO
Inventors: Yuichi Shibazaki
Original assignee: Nikon Corporation
Priority date: 2001-11-07
Filing date: 2002-11-01
Publication date: 2003-05-15
Also published as: JPWO2003040785A1; TW577108B

Abstract

An optical element capable of eliminating the effect of rotationally symmetrical double refraction remaining in an optical system using a double refractive crystal material such as fluorine, comprising a light transmitting member (1) and an annular member (2) having a thermal expansion coefficient different from that of the light transmitting member and disposed on the outer peripheral side of the light transmitting member, the annular member (2) further comprising an inner ring (2a) fixed to the light transmitting member (2) and an outer ring (2b) connected to the inner ring through connection members (2c) having a flexibility in the radial direction thereof, wherein the light transmitting member is fixed to the annular member in the environment of a specified temperature different from the actual use temperature of the light transmitting member.

Description

Description Optical element, method for manufacturing the same, optical system, exposure apparatus, and method for manufacturing microdevice

Technical field

The present invention relates to an optical element, a method for manufacturing the same, an optical system, an exposure apparatus, and a method for manufacturing a micro device, and particularly to an exposure apparatus used when manufacturing a micro device such as a semiconductor element or a liquid crystal display element in a photolithography process. The present invention relates to a projection optical system suitable for the present invention. Background art

Conventionally, the pattern of a reticle as a mask is used as a substrate via a projection optical system in the photolithographic process for manufacturing semiconductor devices, imaging devices (such as CCDs), liquid crystal display devices, or thin-film magnetic heads. A projection exposure apparatus is used to transfer the image onto each exposure area (each shot area) of a wafer (or glass plate, etc.). In recent years, with the increase in the degree of integration of semiconductor devices and the like, the resolving power (resolution) required of the projection optical system has been increasing more and more, and the wavelength of the exposure light used has tended to become shorter and shorter. . There is already an exposure apparatus that uses the A r F excimer laser one is entering a mass-production system, use of F ₂ laser one also that have been entering a port in the field of view is the next generation exposure apparatus. Such short wavelength region of the light source for supplying light, especially in Ru exposure apparatus using F ₂ laser primary light source, from the viewpoint of transmittance secured, firefly light transmitting member constituting the projection optical system (lens or the like) Using stones is inevitable.

By the way, it is known that, unlike quartz glass, etc., fluorite is a crystal belonging to the cubic system and generates a considerable amount of birefringence for incident light. In this case, by controlling the crystal orientation of each fluorite lens, it is possible to negate the effects of birefringence with each other and thus suppress the effect of birefringence. However, even if such management measures are taken, birefringence that is rotationally symmetric with respect to the optical axis remains. Disclosure of the invention

The present invention has been made in view of the above-described problems, and is an optical element capable of canceling out the influence of rotationally symmetric birefringence remaining in an optical system using a birefringent crystal material such as fluorite. And a method for producing the same.

In addition, the present invention includes an optical element capable of canceling the influence of rotationally symmetric birefringence, and can maintain good optical performance even when a birefringent crystal material such as fluorite is used, for example. It is an object to provide an optical system.

Further, the present invention provides an exposure apparatus which has an optical system having good optical performance even when a birefringent crystal material such as fluorite is used, and is capable of performing high-resolution and high-precision exposure. The purpose is to provide.

Further, the present invention provides a microdevice manufacturing method capable of manufacturing a high-performance microdevice according to a high-resolution exposure technique using an exposure apparatus capable of performing high-resolution and high-precision exposure. The purpose is to:

In order to solve the above problems, in a first invention of the present invention, a light transmitting member,

An annular member having a coefficient of thermal expansion different from the coefficient of thermal expansion of the light transmitting member, and being disposed on the outer periphery of the light transmitting member;

A stress generating member that is disposed between the light transmitting member and the annular member and that generates stress on the light transmitting member due to a difference between a coefficient of thermal expansion of the light transmitting member and a coefficient of thermal expansion of the annular member; An optical element characterized by comprising:

According to a preferred aspect of the first invention, the stress generating member fixes the outer periphery of the light transmitting member and the inner periphery of the annular member in an environment at a predetermined temperature different from the actual use temperature of the light transmitting member. . In addition, the annular member includes an inner ring fixed to the light transmitting member via the stress generating member, and a connecting member having flexibility in a radial direction of the inner ring. It is preferable to have a connected outer ring. In this case, the stress generating member is an adhesive for fixing an outer periphery of the light transmitting member and an inner periphery of the annular member, and the inner ring has an outer periphery of the light transmitting member and an inner periphery of the annular member. Through hole for injecting adhesive between Is preferably formed.

According to a preferred aspect of the first invention, a holding portion projecting outward from an outer peripheral surface of the outer ring with respect to a center of the outer ring is formed on an outer periphery of the outer ring. . Further, it is preferable that the connecting member has a plurality of flexible members extending so as to circumscribe the inner ring. Further, it is preferable that the inner ring, the outer ring, and the plurality of flexible members are integrally formed. Further, it is preferable that the light transmitting member is a crystal optical member formed of a crystal belonging to a cubic system.

According to a second aspect of the present invention, in the manufacturing method for manufacturing an optical element,

A light transmitting member, and a positioning step of positioning the annular member having a thermal expansion coefficient different from the coefficient of thermal expansion of the light transmitting member and arranged on the outer periphery of the light transmitting member at predetermined positions,

A holding step for holding the light transmitting member and the annular member positioned at the predetermined position in an environment at a predetermined temperature different from an actual use temperature of the light transmitting member; and And a fixing step of fixing the outer periphery of the light transmitting member and the inner periphery of the annular member held in a temperature environment.

According to a preferred aspect of the second invention, in the positioning step, the light transmitting member and the annular member are respectively floated and positioned using an air bearing. Preferably, in the fixing step, when the predetermined temperature is higher than the actual use temperature, an internal stress related to tension is generated in the light transmitting member. Further, in the fixing step, when the predetermined temperature is lower than the actual use temperature, it is preferable that an internal stress relating to compression is generated in the light transmitting member.

According to a third aspect of the present invention, there is provided an optical system including a crystal optical member formed of a crystal belonging to a cubic system and the optical element of the first aspect.

According to a fourth aspect of the present invention, there is provided an illumination optical system for illuminating a mask,

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

In the sixth invention of the present invention, an exposure step of exposing the photosensitive substrate to a device pattern of the mask using the exposure apparatus of the fourth invention or the fifth invention,

And a developing step of developing the photosensitive substrate exposed in the exposing step. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram schematically showing a configuration of an exposure apparatus equipped with a projection optical system incorporating an optical element according to an embodiment of the present invention.

FIG. 2A is a diagram schematically showing a configuration of the optical element according to the present embodiment, and is a plan view.

FIG. 2B is a diagram schematically showing the configuration of the optical element according to the present embodiment, and shows a cross-sectional view along line A_A in FIG. 2A.

FIG. 3 is a view showing a state in which the light transmitting member and the inner ring are fixed to each other with an adhesive in the present embodiment.

FIG. 4A and FIG. 4B are views for explaining a method of manufacturing the optical element of the present embodiment.

FIG. 5 is a perspective view schematically showing an entire configuration of a mounting member for holding the optical element of the present embodiment and mounting the optical element on a lens barrel of a projection optical system.

FIG. 6 is a top view of the mounting member of FIG.

FIG. 7 is a sectional view taken along line BB of FIG.

FIG. 8 is a flowchart of a method for obtaining a semiconductor device as a micro device.

FIG. 9 is a flowchart of a method for obtaining a liquid crystal display element as a micro device. BEST MODE FOR CARRYING OUT THE INVENTION

200 At the 2nd International Symposium on 157nm Lithography held on May 15, 2001, John H. Burnett, NIST of the United States, found that fluorite has intrinsic birefringence. Was confirmed both experimentally and theoretically. According to this statement, the birefringence of fluorite is approximately the same in the crystal axis [1 1 1] direction (and its equivalent crystal axis) and in the crystal axis [100] direction (and its equivalent crystal axis). It is zero, but has a substantially non-zero value in the other directions.

Burnett et al. In the above-mentioned publication disclosed a technique for reducing the effects of fluorite birefringence. In the method of Burnett et al., The optical axis of a pair of fluorite lenses is aligned with the crystal axis [1 1 1], and the pair of fluorite lenses are relatively rotated about the optical axis by about 60 degrees. Then, due to the action of the pair lens with the crystal axis [1 1 1], a birefringent region in which the refractive index for circumferentially polarized light is smaller than that for radially polarized light remains (in other words, rotationally symmetric with respect to the optical axis). Birefringence remains), but the effect of birefringence can be considerably reduced.

On the other hand, for example, in the specification and drawings of Japanese Patent Application No. 2001-206935, the present applicant discloses that the optical axis and the crystal axis [100] (or the crystal axis [100]) of a pair of fluorite lenses And a method in which a pair of fluorite lenses are relatively rotated about the optical axis by about 45 degrees. In the method of the present applicant, birefringence that is rotationally symmetric with respect to the optical axis will remain to some extent due to the action of the pair lens of the crystal axis [100], but the effect of the birefringence can be considerably reduced. .

As described above, for example, in an exposure apparatus using the F ₂ laser beam as the exposure light, so that the projection optical system using a number of fluorite lens. In this case, the influence of the birefringence of fluorite is considerably improved by using a paired lens with a crystal axis [1 1 1] according to the method of Burnett et al. And a paired lens with a crystal axis [100] according to the method of the present applicant. Can be reduced. However, even if the crystal orientation of each fluorite lens is managed as described above, the effect of rotationally symmetric birefringence with respect to the optical axis remains. become.

By the way, when an internal stress that is rotationally symmetric with respect to the optical axis is generated in a light transmitting member (a lens, a plane parallel plate, etc.), birefringence that is rotationally symmetric with respect to the optical axis is generated with respect to light passing through the light transmitting member. appear. Therefore, the influence of the rotationally symmetric birefringence remaining after managing the crystal orientation of each fluorite lens is considered to be the rotationally symmetric birefringence generated by the rotationally symmetric internal stress (the sign of the opposite birefringence is opposite to that of the remaining birefringence). By canceling out due to the influence of birefringence having substantially the same size, an optical system having good optical performance can be realized.

Japanese Patent Application Laid-Open Publication No. 2000-331927 discloses that a metal belt (a correction member) is provided around a parallel flat plate (correction member) in order to correct the influence of birefringence inherent in a crystal material. A technique is disclosed in which a stress adjusting means is attached and a belt is tightened via screws to generate an internal stress in a parallel plane plate in an inward direction. However, in the prior art disclosed in this publication, the friction between the parallel flat plate and the belt, the manufacturing error or processing accuracy of the outer peripheral surface of the parallel flat plate, or the manufacturing error or processing of the inner peripheral surface of the belt. Due to accuracy and other factors, it is impossible to generate internal stress in a parallel flat plate that is rotationally symmetric and uniform with respect to the optical axis. Further, in the prior art, internal stress cannot be generated in the outward direction in the plane parallel plate.

An optical element according to a typical aspect of the present invention includes a light transmitting member and an annular member disposed around the light transmitting member. Here, the coefficient of thermal expansion of the light transmitting member is set to be different from the coefficient of thermal expansion of the annular member. The light transmitting member and the annular member are fixed to each other while being held in an environment at a predetermined temperature different from the actual use temperature.

Therefore, when the light transmitting member and the annular member fixed to each other return to the actual use temperature, the light transmitting member has an optical axis due to the difference between the thermal expansion coefficient of the light transmitting member and the thermal expansion coefficient of the annular member. A substantially rotationally symmetric internal stress is generated. Here, the direction of the generated rotationally symmetric internal stress depends on the magnitude relationship between the coefficient of thermal expansion of the light transmitting member and the coefficient of thermal expansion of the annular member and the relationship between the predetermined temperature for fixing and the actual use temperature. I do. The magnitude of the rotationally symmetric internal stress depends on the temperature difference between the predetermined fixing temperature and the actual operating temperature. Dependent.

Thus, in the optical element of the present invention, by appropriately setting the magnitude relationship of the coefficient of thermal expansion, the magnitude relationship of the temperature, and the temperature difference, the optical element is substantially rotationally symmetric with respect to the optical axis and has a desired direction and a desired size. The internal stress having the light transmission member can be generated. As a result, the effect of rotationally symmetric birefringence remaining in an optical system using a birefringent crystal material such as fluorite can be canceled.

Therefore, by incorporating the optical element of the present invention, which can cancel the influence of rotationally symmetric birefringence, into an optical system, good optical performance can be ensured even when a birefringent crystal material such as fluorite is used. can do. In addition, by mounting the optical system of the present invention having good optical performance even when a birefringent crystal material such as fluorite is used in an exposure apparatus, high-resolution and high-precision exposure can be performed. Can be. Furthermore, a high-performance micro device can be manufactured according to a high-resolution exposure technique by using the exposure apparatus of the present invention capable of performing high-resolution and high-precision exposure. An embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a diagram schematically showing a configuration of an exposure apparatus equipped with a projection optical system incorporating an optical element according to an embodiment of the present invention. In FIG. 1, the Z-axis is parallel to the reference optical axis AX of the projection optical system PL, the Y-axis is parallel to the plane of FIG. 1 in the plane perpendicular to the reference optical axis AX, and the Z-axis is the reference optical axis AX. The X axis is set perpendicular to the plane of Fig. 1 in a vertical plane.

The exposure apparatus shown in FIG. 1 as a light source LS for supplying illumination light in the ultraviolet region, for example, includes an F ₂ laser light source (wavelength 1 5 7 nm). The light emitted from the light source LS illuminates a reticle (mask) R on which a predetermined pattern is formed via an illumination optical system IL. The optical path between the light source LS and the illumination optical system IL is sealed by a casing (not shown), and the space from the light source LS to the optical member closest to the reticle in the illumination optical system IL is exposed. It has been replaced with an inert gas such as helium gas or nitrogen, which is a gas with a low light absorption rate, or is kept almost in a vacuum state.

Reticle R is placed on reticle stage RS via reticle holder RH. It is held parallel to the XY plane. The pattern to be transferred is formed on the reticle R. For example, a rectangular pattern having a long side along the X direction and a short side along the Y direction in the entire pattern area by the illumination optical system IL. The area is illuminated. The reticle stage RS can be moved two-dimensionally along the reticle plane (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are determined by an interferometer RIF using a reticle moving mirror RM. It is configured to be measured and position controlled.

Light from the pattern formed on the reticle R forms a reticle pattern image on the wafer W as a photosensitive substrate via the projection optical system PL. The wafer W is held in parallel with the XY plane on the wafer stage WS via a wafer table (wafer holder) WT. Then, on the wafer W, a rectangular exposure area having a long side along the X direction and a short side along the Y direction so as to optically correspond to the rectangular illumination area on the reticle R. A pattern image is formed on the substrate. The wafer stage WS can be moved two-dimensionally along the wafer surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are determined by an interferometer WIF using a wafer moving mirror WM. It is configured to be measured and position controlled.

In the exposure apparatus shown in the figure, the inside of the projection optical system PL is interposed between the optical member arranged closest to the reticle and the optical member arranged closest to the wafer among the optical members constituting the projection optical system PL. The gas inside the projection optical system PL is replaced by an inert gas such as helium gas or nitrogen, or is maintained in a substantially vacuum state.

Further, a reticle R and a reticle stage RS are disposed in a narrow optical path between the illumination optical system IL and the projection optical system PL, but a casing (not shown) that hermetically surrounds the reticle R and the reticle stage RS. ) Is filled with an inert gas such as nitrogen or helium gas, or is kept almost in a vacuum state. Note that a configuration may be adopted in which an inert gas is locally supplied only to an optical path portion between the illumination optical system IL and the projection optical system PL without providing a casing.

The narrow optical path between the projection optical system PL and the wafer W includes the wafer W and the wafer W. A housing WS etc. is placed, but an inert gas such as nitrogen or helium gas is filled in a casing (not shown) that encloses the wafer W and the wafer stage WS etc. It is kept in a vacuum state. Note that a configuration in which an inert gas is locally supplied only to the optical path portion between the projection optical system PL and the wafer W without providing casing is also possible. Thus, an atmosphere in which the exposure light is hardly absorbed is formed over the entire optical path from the light source LS to the wafer W.

As described above, the illumination area on the reticle R and the exposure area on the wafer W (that is, the effective exposure area) defined by the projection optical system PL are rectangular with short sides along the Y direction. Therefore, while controlling the position of reticle R and wafer W using a drive system and an interferometer (RIF, WIF), etc., the reticle stage along the short side direction of the rectangular exposure area and illumination area, that is, along the Y direction. By moving (running) the RS and the wafer stage WS and, consequently, the reticle R and the wafer W synchronously, the wafer W has a width equal to the long side of the exposure area and the wafer W The reticle pan is scanned and exposed to an area having a length corresponding to the scanning amount (moving amount).

In this embodiment, since one F ₂ laser beam is used as the exposure light, the projection optical system PL includes a large number of fluorite lenses, but the paired lens with the crystal axis [1 1 1] and the crystal axis [1 [0 0], the effect of the birefringence of fluorite is significantly reduced. However, even if the crystal orientation of each fluorite lens is appropriately controlled, birefringence that is rotationally symmetric with respect to the optical axis will remain.By incorporating the optical element according to the present invention into the projection optical system PL, Excellent imaging performance is achieved by offsetting the effects of the remaining rotationally symmetric birefringence by the effects of rotationally symmetric birefringence generated by the internal stress of the optical element.

FIG. 2A is a diagram schematically showing a configuration of the optical element according to the present embodiment, and is a plan view. FIG. 2B shows a cross-sectional view along the line AA in FIG. 2A. With reference to 2 A view and a 2 B diagram, the optical element of this embodiment includes a light transmissive member 1 having the property of transmitting F ₂ laser light, the light transmitting member 1 And an annular member 2 disposed on the outer periphery of the ring. The shape of the light transmitting member 1 is not limited to a biconcave shape as shown, but may be, for example, a meniscus shape, a biconvex shape, or a parallel plane shape. The optical material forming the light transmitting member 1 is not limited to fluorite, but may be other suitable crystalline materials or quartz glass depending on the wavelength of light.

The annular member 2 includes an inner ring 2a fixed to the light transmitting member 1 and an outer ring connected to the inner ring 2a via a radially flexible connecting member of the inner ring 2a. Ring 2b. Here, the connecting member has three plate-shaped flexible members 2c extending so as to circumscribe the inner ring 2a. The flexible member 2c has both ends connected to the outer ring 2b, and a central portion connected to the inner ring 2a. Further, on the outer periphery of the outer ring 2b, a holding portion 2d protruding outward from the outer peripheral surface of the outer ring 2b is formed with respect to the center of the outer ring 2b. The inner ring 2a, the outer ring 2b, and the three flexible members 2c are integrally formed of a suitable material such as aluminum or an alloy thereof, stainless steel, titanium, or brass. Is formed.

In the present embodiment, the coefficient of thermal expansion of the light transmitting member 1 and the coefficient of thermal expansion of the inner ring 2a (and the coefficient of thermal expansion of the annular member 2) are set to be different. The light transmitting member 1 and the inner ring 2a (and, consequently, the annular member 2) are held in an environment at a predetermined temperature (for example, a high temperature or a low temperature relative to the normal temperature) different from the actual use temperature (for example, the normal temperature) of the optical element. In this state, they are fixed to each other by, for example, an epoxy adhesive. Preferably, the adhesive is made of a material that suppresses the generation of organic substances and moisture that absorb exposure light.

FIG. 3 is a view showing a state in which the light transmitting member and the inner ring are fixed to each other with an adhesive in the present embodiment. In this embodiment, as shown in FIG. 3, a through hole 3 for injecting an adhesive is provided between the outer periphery of the light transmitting member 1 and the inner periphery of the annular member 2 (therefore, the inner periphery of the inner ring 2a). 1 are formed at a predetermined pitch (that is, at equal angular intervals) along the circumferential direction of the inner ring 2a. Therefore, By injecting the adhesive through each through hole 31, the light transmitting member 1 and the annular member 2 can be evenly fixed in the circumferential direction.

Thus, in the present embodiment, when the light transmitting member 1 and the annular member 2 fixed to each other return to the actual use temperature, the difference between the thermal expansion coefficient of the light transmitting member 1 and the thermal expansion coefficient of the annular member 2 causes A substantially rotationally symmetric internal stress is generated in the light transmitting member 1 with respect to the optical axis AX. Specifically, when the light transmitting member 1 is formed of fluorite and the annular member 2 is formed of titanium, stainless steel, or brass, the thermal expansion coefficient of the light transmitting member 1 is higher than that of the annular member 2. The rate increases. In this case, if the light-transmitting member 1 is fixed at a temperature higher than the actual use temperature, an internal stress (tensile stress) in the outward direction occurs in the light-transmitting member 1. Generates internal stress (compression stress) in the inward direction.

Conversely, when the light transmitting member 1 is formed of quartz glass and the annular member 2 is formed of titanium / stainless steel or brass, the thermal expansion coefficient of the annular member 2 is larger than that of the light transmitting member 1. growing. In this case, if it is fixed at a temperature higher than the actual use temperature, an internal stress is generated in the light transmitting member 1 in the inward direction. Stress occurs. As described above, the adhesive is disposed between the light transmitting member 1 and the annular member 2, and due to the difference between the coefficient of thermal expansion of the light transmitting member 1 and the coefficient of thermal expansion of the annular member 2, the adhesive is applied to the light transmitting member 1. On the other hand, it constitutes a stress generating member that generates internal stress.

In the present embodiment, even when the actual use temperature of the optical element fluctuates to some extent, the fluctuation of the internal stress generated in the light transmitting member 1 does not become too large, and thus the fluctuation of the optical characteristics of the projection optical system PL becomes too large. In order to avoid this, the circumferential rigidity (the product of the cross-sectional area and the elastic modulus) of the inner ring 2a must be kept small. As a result, the inner ring 2a has a very thin annular plate shape, and it is preferable to provide a holding portion (projection) to be gripped when holding the optical element on the outer periphery of the inner ring 2a. Absent.

Therefore, in the present embodiment, a structure for connecting the inner ring 2a and the outer ring 2b via a connecting member 2c having flexibility in the radial direction of the inner ring 2a. Is adopted. In this case, even if the outer ring 2b returns to the actual use temperature due to the action of the connecting member 2c having flexibility in the radial direction, the contraction or expansion of the outer ring 2b causes the inner ring 2a (therefore, the light transmitting member). 1) is not substantially affected. Therefore, it is not necessary to keep the cross-sectional area of the outer ring 2b small, and as a result, it is possible to form the holding portion 2d on the outer periphery of the outer ring 2b.

FIG. 4A and FIG. 4B are diagrams illustrating the method for manufacturing the optical element of the present embodiment. In the manufacturing method (assembly method) of the present embodiment, as shown in FIG. 4A, an air bearing having a support surface 41 a having a complementary surface shape to one optical surface 1 a of the light transmitting member 1 is used. Using the unit 41, the light transmitting member 1 is floated and positioned. Further, the annular member 2 is lifted using an air bearing unit 42 having a supporting surface 42a having a complementary surface shape with respect to one side surface 2ba of the outer ring 2b constituting the annular member 2. Position. Thus, by the action of the air bearing, the optical axis AX of the light transmitting member 1 and the center axis of the annular member 2 are aligned so that the light transmitting member 1 and the annular member 2 are aligned along the optical axis AX. The light transmitting member 1 and the annular member 2 are positioned at predetermined positions in a non-contact manner.

Next, the light transmitting member 1 and the annular member 2 positioned at predetermined positions are held in an environment at a predetermined temperature (for example, higher or lower than normal temperature) different from the actual use temperature. Then, the outer periphery of the light transmitting member 1 and the inner periphery of the annular member 2 positioned at a predetermined position and held in an environment of a predetermined temperature are bonded through a through hole 31 formed in the inner ring 2a. It is fixed by injecting the agent. Thus, as shown in FIG. 4B, when the light transmitting member 1 and the annular member 2 fixed to each other return to the actual use temperature, the thermal expansion coefficients of the light transmitting member 1 and the annular member 2 are reduced. Due to this difference, an internal stress that is substantially rotationally symmetric about the optical axis AX is generated in the light transmitting member 1. FIG. 5 is a perspective view schematically showing an entire configuration of a mounting member for holding the optical element of the present embodiment and mounting the optical element on a lens barrel of a projection optical system. FIG. 6 is a top view of the mounting member of FIG. FIG. 7 is a cross-sectional view taken along line BB in FIG. Referring to FIGS. 5 to 7, the optical element of this embodiment (light transmitting member) 1 and the annular member 2) are held by a mounting member 50 and mounted on a lens barrel (not shown) of the projection optical system PL.

The attachment member 50 has a generally ring-shaped body 51. The optical element (1, 2) of the present embodiment includes three spring groups arranged at a predetermined pitch (specifically, at equal angular intervals of 120 degrees) along the circumferential direction of the main body 51. It is attached to the attachment member 50 by the action of the solids 52a to 52c. Specifically, small seats (not shown) are provided at the positions of the three spring assemblies 52a to 52c, and formed on the outer ring 2b of the optical element on these three seats. The holder 2d is placed. At this time, the outer ring 2b and thus the optical element are prevented from being excessively restrained by the planar contact between the seat and the holding portion 2d.

The seat has a structure that allows the optical element to expand in the radial direction (horizontal direction), but has a predetermined rigidity in both the vertical and tangential directions, and has a high mounting rigidity with respect to the optical element. Have maintained. The spring assemblies 52a to 52c directly and mechanically tighten the holding portion 2d of the optical element onto the seat, and a moment that may be generated due to a difference between the tightening force and the force of the seat. Are all removed. By mechanically tightening the optical element (1, 2) without the use of adhesives, the problems inherent in the use of adhesives, such as degassing and destruction during decomposition, are avoided.

By providing a flexible tightening mechanism for the spring assemblies 52a to 52c, tightening is possible even if there are some mechanical errors and dimensional errors that can occur within the range of mechanical tolerances. The force is applied substantially evenly and constantly. This type of tightening mechanism includes a spring assembly

Mounted at the position of 52a to 52c to prevent excessive restraint due to the difference in extension of the optical element (1, 2). For more detailed configuration and operation of the mounting member 50, refer to the specification and drawings of Japanese Patent Application No. 2000-210209 filed by the present applicant. .

As described above, in the present embodiment, the light transmitting member 1 and the annular member 2 having different coefficients of thermal expansion are held in a high or low temperature environment different from the actual use temperature. They are fixed to each other. Therefore, when the light transmitting member 1 and the annular member 2 fixed to each other return to the actual use temperature, the thermal expansion coefficient of the light transmitting member 1 is reduced. Due to the difference between the thermal expansion coefficient of the annular member 2 and the thermal expansion coefficient, a substantially rotationally symmetric stress is generated in the light transmitting member 1 with respect to the optical axis AX.

Thus, in the optical element of the present embodiment, an internal stress that is substantially rotationally symmetric with respect to the optical axis AX can be generated in the light transmitting member 2, so that the rotationally symmetric birefringence remaining in the projection optical system PL using fluorite is used. Can negate the effects of Therefore, in the projection optical system PL incorporating the optical element of the present embodiment capable of canceling the influence of the rotationally symmetric birefringence, a good imaging performance (optical performance) is secured even when fluorite is used. be able to. An exposure apparatus equipped with a projection optical system PL that has good optical performance even when fluorite is used can perform high-resolution and high-precision exposure.

In the above-described embodiment, a calcium fluoride crystal (fluorite) is used as the birefringent optical material. However, the present invention is not limited to this, and other uniaxial crystals, for example, a barium fluoride crystal (fluorite) may be used. B aF ₂ ), lithium fluoride crystal (L i F), sodium fluoride crystal (NaF), strontium fluoride crystal (S r F ₂ ), beryllium fluoride crystal (B e F ₂ ), etc. On the other hand, other transparent crystal materials can be used. Of these, barium fluoride crystals have already been developed for large crystal materials with diameters exceeding 20 Omm and are promising as lens materials. In this case, it is preferable that the crystal axis orientation of the barium fluoride (BaF ₂ ) or the like is also determined according to the present invention. Further, in the above-described embodiment, the light transmitting member 1 and the annular member 2 are fixed to each other with an adhesive. However, the present invention is not limited to this. And the annular member 2 can be fixed. Further, in the above-described embodiment, the adhesive is injected through the plurality of through holes 31 provided at equal angular intervals in the inner ring 2a, but the number, shape, and arrangement of the through holes 31 Various modifications are possible. Further, an adhesive can be injected between the light transmitting member 1 and the annular member 2 without using the through hole 31.

In the above-described embodiment, the inner ring 2a, the outer ring 2b, and the three flexible members 2c are integrally formed of a metal material. However, without being limited to this, the inner ring 2a, the outer ring 2b, and the three flexible members 2c can also be formed separately. Also, a flexible member Various modifications are possible for the number and shape of 2 c and the material for forming the annular member 2.

By the way, in the above embodiment, the optical surface may be slightly deformed under the influence of the internal stress generated in the light transmitting member 1. Therefore, it is preferable to correct the optical surface by measuring the surface shape of the optical surface if necessary after manufacturing the optical element of the present embodiment, and performing polishing based on the measurement result.

In the exposure apparatus according to the above-described embodiment, the reticle (mask) is illuminated by the illumination device (illumination step), and the transfer pattern formed on the mask is exposed on the photosensitive substrate using the projection optical system (exposure step). Thus, microdevices (semiconductor devices, imaging devices, liquid crystal display devices, thin-film magnetic heads, etc.) can be manufactured. The flowchart of FIG. 8 shows an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of the present embodiment. It will be described with reference to FIG.

First, in step 301 of FIG. 8, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the one lot of wafers. Then, in step 303, using the exposure apparatus of the present embodiment, the pattern image on the mask is sequentially exposed and transferred to each shot area on the one-port wafer via the projection optical system. Is done. Then, in step 304, after the photoresist on the one lot of wafers is developed, in step 305, etching is performed on the one lot of wafers using the resist pattern as a mask. As a result, a circuit pattern corresponding to the pattern on the mask 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. According to the above-described semiconductor device manufacturing method, a semiconductor device having an extremely fine circuit pattern can be obtained with good throughput. In steps 301 to 305, a metal is vapor-deposited on the wafer, a resist is applied on the metal film, and the respective steps of exposure, development, and etching are performed. Prior to forming a silicon oxide film on the wafer, It goes without saying that a resist may be applied on the silicon oxide film of the first step, and each step of exposure, development, etching and the like may be performed.

In the exposure apparatus of the present embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate). Hereinafter, an example of the technique at this time will be described with reference to the flowchart in FIG. In FIG. 9, in a pattern forming step 401, a so-called photolithography step is performed in which a mask pattern is transferred and exposed to a photosensitive substrate (eg, a glass substrate coated with a resist) using the exposure apparatus of the present embodiment. Is executed. By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate is subjected to various processes such as a developing process, an etching process, a resist stripping process, etc., whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming process 402. I do. Next, in the color filter forming process 402, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix, or R, A color filter in which a set of three stripe filters of G and B are arranged in the horizontal scanning line direction is formed. Then, after the color filter forming step 402, a cell assembling step 403 is performed. In the cell assembling step 403, the liquid crystal is formed using the substrate having the predetermined pattern obtained in the pattern forming step 401, the color filter obtained in the color filter forming step 402, and the like. Assemble the panel (liquid crystal cell). In the cell assembling step 403, for example, the substrate having the predetermined pattern obtained in the pattern forming step 401 and the color filter set obtained in the color filter forming step 402 are formed. Liquid crystal is injected between them to manufacture liquid crystal panels (liquid crystal cells).

Then, in a module assembling step 404, components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display element, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput. In the above embodiment, the present invention is applied to the projection optical system mounted on the exposure apparatus. However, the present invention is not limited to this, and the illumination optical system mounted on the exposure apparatus, The present invention can be applied to a general optical system. Further, in the above-described embodiment, the F ₂ laser and one light source that supplies the light of the wavelength of 157 nm are used. However, the present invention is not limited to this. For example, the light of the wavelength of 193 nm is supplied. the wavelength of a r F excimer laser primary light source and 1 2 6 nm may be used as a r ₂ laser light source for supplying. Industrial applicability

As described above, according to the present invention, the light transmitting member and the annular member set so as to have different coefficients of thermal expansion are fixed to each other in a state where they are held in an environment of a predetermined temperature different from the actual use temperature. Therefore, when the light transmitting member and the annular member fixed to each other return to the actual use temperature, the difference between the coefficient of thermal expansion of the light transmitting member and the coefficient of thermal expansion of the annular member causes the light transmitting member to have a different shape. A substantially rotationally symmetric stress is generated with respect to the optical axis. As a result, in the optical element of the present invention, the influence of rotationally symmetric birefringence remaining in an optical system using a birefringent crystal material such as fluorite can be canceled.

Therefore, in an optical system incorporating the optical element of the present invention, which can cancel the influence of rotationally symmetric birefringence, good optical performance is ensured even when a birefringent crystal material such as fluorite is used. be able to. In addition, an exposure apparatus equipped with the optical system of the present invention, which has good optical performance even when a birefringent crystal material such as fluorite is used, can perform high-resolution and high-precision exposure. Furthermore, using the exposure apparatus of the present invention capable of performing high-resolution and high-precision exposure, a high-performance microdevice can be manufactured according to a high-resolution exposure technique.

Claims

The scope of the claims

1. Light transmitting member,

A stress generating member that is disposed between the light transmitting member and the annular member and that generates stress on the light transmitting member due to a difference between a coefficient of thermal expansion of the light transmitting member and a coefficient of thermal expansion of the annular member; An optical element comprising:

2. The optical element according to claim 1,

The optical element, wherein the stress generating member fixes an outer periphery of the light transmitting member and an inner periphery of the annular member in an environment at a predetermined temperature different from an actual use temperature of the light transmitting member.

3. The optical element according to claim 1 or 2,

The annular member includes: an inner ring fixed to the light transmitting member via the stress generating member; and a connecting member having flexibility in a radial direction of the inner ring. An optical element comprising: an outer ring connected to the optical element.

4. The optical element according to claim 3,

The stress generating member is an adhesive for fixing an outer periphery of the light transmitting member and an inner periphery of the annular member,

An optical element, wherein the inner ring has a through-hole for injecting an adhesive between an outer periphery of the light transmitting member and an inner periphery of the annular member.

5. The optical element according to claim 3 or 4, wherein

The outer periphery of the outer ring is arranged with respect to the center of the outer ring. —An optical element characterized in that a holding portion protruding outward from the outer peripheral surface of the ring is formed.

6. The optical element according to any one of claims 3 to 5, wherein the connecting member has a plurality of flexible members extending so as to circumscribe the inner ring. Characteristic optical element.

7. The optical element according to claim 6, wherein

The optical element, wherein the inner ring, the outer ring, and the plurality of flexible members are integrally formed.

8. The optical element according to any one of claims 1 to 7, wherein the light transmitting member is a crystal optical member formed of a crystal belonging to a cubic system. Optical element.

9. In a manufacturing method for manufacturing an optical element,

A light transmitting member, and a positioning step of positioning the annular member having a thermal expansion coefficient different from that of the light transmitting member at a predetermined position, the annular member being disposed on the outer periphery of the light transmitting member.

A holding step for holding the light transmitting member and the annular member positioned at the predetermined position in an environment at a predetermined temperature different from an actual use temperature of the light transmitting member; and A fixing step of fixing an outer periphery of the light transmitting member and an inner periphery of the annular member held in a temperature environment.

10. The method according to claim 9, wherein

The manufacturing method, wherein in the positioning step, the light transmitting member and the annular member are respectively floated and positioned using an air bearing.

11. The method according to claim 9, wherein:

The manufacturing method according to claim 1, wherein in the fixing step, when the predetermined temperature is higher than the actual use temperature, an internal stress related to tension is generated in the light transmitting member.

12. The method according to claim 9, wherein

The manufacturing method according to claim 1, wherein, in the fixing step, when the predetermined temperature is lower than the actual use temperature, an internal stress related to compression is generated in the light transmitting member.

13. An optical system comprising: a crystal optical member formed of a crystal belonging to a cubic system; and the optical element according to any one of claims 1 to 8.

1 4. An illumination optical system for illuminating the mask,

An exposure apparatus comprising: the optical system according to claim 13 for forming an image of a pattern formed on the mask on a photosensitive substrate.

15. An optical system according to claim 13 for illuminating a mask, and a projection optical system for forming an image of a pattern formed on the mask on a photosensitive substrate. An exposure apparatus.

16. An exposure step of exposing the photosensitive substrate to a device pattern of the mask using the exposure apparatus according to claim 14 or 15,

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