JP2000195772A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner which is well corrected for chromatic aberration against such short-wavelength light as the F2 laser light, etc., with a small number of lenses. SOLUTION: A lighting optical system 3 is constituted to supply illuminating light having a central wavelength of <=180 nm and a full width at half maximum of <=20 pm. A projection optical system 7 contains a lens component and a concave reflecting mirror which are positioned to substantially correct the chromatic aberration of the optical system 7 against illuminating light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection exposure apparatus, and more particularly to a projection exposure apparatus used for manufacturing a semiconductor device or the like in a photolithography process, which has a catadioptric projection optical system. About.

[0002]

2. Description of the Related Art In manufacturing integrated circuits such as LSIs,
Reduction projection exposure apparatuses are widely used. In a reduction projection exposure apparatus, a reduced image of a mask pattern is formed on a wafer as a photosensitive substrate via a projection optical system. In recent years, integrated circuit patterns projected and exposed on a semiconductor substrate have become increasingly finer, and there is a demand for further improving the resolution of a projection exposure apparatus.

In order to further improve the resolution of a projection exposure apparatus, it is necessary to increase the numerical aperture (NA) of the projection optical system and to shorten the exposure wavelength. However, it is difficult to increase the NA of the projection optical system beyond a predetermined value due to the configuration of the optical system. Further, when the NA of the projection optical system is increased, the usable depth of focus becomes smaller, and as a result, it becomes difficult to realize a theoretically possible resolution. Therefore, in reality, it is particularly strongly required to shorten the exposure wavelength in order to improve the resolution of the projection exposure apparatus.

Conventionally, an exposure light source has a wavelength of 248 nm.
KrF excimer laser and ArF excimer laser having a wavelength of 193 nm have been proposed and implemented. Also,
The use of a light source having a shorter wavelength of 180 nm or less is being studied, and the use of an F ₂ laser (wavelength: 157.6 nm) is considered to be particularly promising. However, refractive optical materials that can be used for these short-wavelength lights are limited. That is, substances having good transmittance for light having a wavelength of 180 nm or less include CaF ₂ (calcium fluoride), MgF ₂ (magnesium fluoride), and Li.
F (lithium fluoride) is known, of which MgF ₂ has birefringence and LiF has deliquescence.
For this reason, CaF ₂ crystal (fluorite) is only known as a practical refractive optical material for light having a wavelength of 180 nm or less.

[0005] In order to eliminate chromatic aberration caused by the wavelength width of the laser beam in a situation where only a single glass material (optical material) can be used as the refractive optical member, various types of catadioptric types are used. Reduction projection optical systems have been proposed. For example, US Pat.
Japanese Patent No. 47,678 discloses an optical system of a type utilizing a large number of reflecting surfaces. Also, U.S. Pat.
No. 53,960 discloses an optical system of a type using a beam splitter prism. Further, JP-A-10-104513 discloses an optical system of a type having a shield at the center of an opening. Further, Japanese Patent Application Laid-Open No. Hei 8-334695 discloses an optical system of a type having one concave reflecting mirror.

[0006]

However, the catadioptric projection optical system of the type described above has the following disadvantages. First, US Pat. No. 4,747,67
In the projection optical system of the type disclosed in Japanese Patent Application Laid-Open No. 8 (1996) -1995, a large number of reflecting surfaces are used. The exposure speed (throughput) decreases. Furthermore, since the usable image area on the photosensitive substrate, that is, the usable area is small, it is difficult to secure a rectangular exposure area as an area actually used for exposure.

A projection optical system of the type disclosed in US Pat. No. 4,953,960 uses a large polarizing beam splitter prism, but has a high transmittance for short wavelength light of 180 nm or less. It is difficult to manufacture a prism having the same. In addition, it is difficult to manufacture a polarization reflection film or a wavelength plate for performing polarization separation on short-wavelength light of 180 nm or less. Further, Japanese Patent Application Laid-Open
In a projection optical system of the type disclosed in Japanese Patent No. 104513, a part of an image forming light beam is blocked by a central opening of a reflecting mirror in an optical path of the image forming optical system. As a result, the fidelity of the formed image is reduced, which is disadvantageous for transferring a circuit pattern with high accuracy.

On the other hand, a projection optical system of the type disclosed in Japanese Patent Application Laid-Open No. Hei 8-334695 is a so-called off-axis optical system that uses a region off the optical axis as an optical path. For this reason, there is an inconvenience that it is relatively difficult to secure a wide image area as compared with an optical system of a type using a region including the optical axis as an optical path. On the other hand, there is an advantage that the image quality is good because there is little reduction in the amount of light and there is no shielding of the image forming light beam, and that the production of each optical member is easier than other types.

By the way, in the case of the F ₂ laser, there is no refractive optical member or reflective optical member having a small light amount loss in the oscillation wavelength band. Therefore, it is said that it is more difficult to make a large band narrowing with respect to the F ₂ laser than in the case of a KrF excimer laser or an ArF excimer laser. Further, since the intensity of the F ₂ laser in practical use is weak, by performing narrowing, the intensity of exposure light, tends to decrease and thus the exposure rate further. In other words, in the case of the F ₂ laser, the effect of the decrease in the exposure speed due to the narrowing of the band is greater than in the case of other lasers.

However, F ₂ having a wavelength of 157.6 nm
Since the natural wavelength width of the laser is considerably smaller than the natural wavelength width of the ArF excimer laser or the like, the full width at half maximum of the F ₂ laser can be reduced to about 20 pm or less by slightly narrowing the band. For example, the NovaLine TMF500 lambda Physic GmbH, a relatively simple narrowing, full width at half maximum output at 10pm is commercialized F ₂ laser of 10 W. Therefore, in a projection exposure apparatus using an F ₂ laser as an exposure light source, it is desirable to use a laser beam having this full width at half maximum to increase the exposure efficiency and to avoid complication of the laser apparatus due to the narrow band. . In this case, in the projection optical system, 10 pm to
Chromatic aberration must be removed over a wider wavelength range of about 20 pm than in the past. The F ₂ laser can be narrowed to a full width at half maximum of about 2 pm by adding a band narrowing element.

However, as described above, CaF ₂ is the only glass material that can be used in the wavelength region of 180 nm or less, but it is difficult to sufficiently remove chromatic aberration with only a single glass material. Further, in this wavelength range, since internal absorption and surface reflection occur in the lens component formed of CaF ₂ , if the number of lens components is increased, the light transmittance of the optical system is significantly reduced.

Further, for example, an F ₂ laser beam such as 18
Short-wavelength light of 0 nm or less has a high absorptivity by air (oxygen). Therefore, for example, in a projection exposure apparatus using an F ₂ laser as an exposure light source, a gas which hardly absorbs exposure light (illumination light), that is, It is necessary to replace the air in the optical system with an inert gas such as lithium.

The present invention has been made in view of the above-projection catadioptric chromatic aberration are well corrected with a small configuration of lenses with respect to short wavelength light such as F ₂ laser light An object of the present invention is to provide a projection exposure apparatus having an optical system. Another object is to provide a projection exposure apparatus which can ensure high transmission of the projection optical system by satisfactorily avoid light absorption by the air of short wavelength such as F ₂ laser light.

[0014]

According to a first aspect of the present invention, there is provided an illumination optical system for illuminating a mask on which a pattern is formed, and an illumination optical system for illuminating the mask based on light from the mask. A projection optical system having a catadioptric projection optical system for forming an image of a pattern on a photosensitive substrate, wherein the illumination optical system has a center wavelength of 180 nm or less and a full width at half maximum of 20 pm or less. The projection optical system includes a lens component and a concave reflecting mirror, wherein the lens component and the concave reflecting mirror substantially reduce chromatic aberration of the projection optical system with respect to the illumination light. And a projection exposure apparatus characterized in that the projection exposure apparatus is positioned so as to make correction.

According to a second aspect of the present invention, there is provided an illumination optical system for illuminating a mask on which a pattern is formed, and an image of the pattern is formed on a photosensitive substrate based on light from the mask. A projection exposure apparatus comprising: a catadioptric projection optical system;
m is configured to supply illumination light having a central wavelength of equal to or less than m and a full width at half maximum equal to or less than a predetermined value, wherein the projection optical system is disposed in proximity to the optical member having refractive power and the mask. The optical member having a refractive power has a light-transmitting optical member for separating the optical member from an external atmosphere, and the mask and the light-transmitting optical member along a direction parallel to an optical axis of the projection optical system. Is set to 50 mm or less. Second
According to a preferred aspect of the present invention, the light-transmitting optical member is a plane-parallel plate. The full width at half maximum of the illumination light is 2
It is preferably 0 pm or less.

Further, according to a preferred aspect of the first and second aspects of the present invention, all the lens components and the concave reflecting mirror constituting the projection optical system are arranged along a common optical axis. Further, it is preferable that the projection optical system includes only one concave reflecting mirror, a plurality of lens components, and one or a plurality of flat reflecting mirrors. Further, the full width at half maximum of the illumination light is preferably 2 pm or less. Further, the exposure area defined on the photosensitive substrate via the projection optical system is preferably rectangular.

Further, according to a preferred aspect of the first and second aspects of the present invention, the projection optical system includes a first imaging optical system for forming a primary image of the pattern based on light from the mask. A second imaging optical system for forming a secondary image of the pattern on the photosensitive substrate based on light from the primary image. In this case, when the maximum effective diameter of the lens of the first imaging optical system is h1 and the maximum effective diameter of the lens of the second imaging optical system is h2, 0.7 <h1 / h2 <1.4. It is preferable to satisfy the following condition.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, in a catadioptric optical system, axial chromatic aberration necessarily occurring in a dioptric system is canceled by chromatic aberration in the opposite direction generated by a negative lens of the catadioptric system. By canceling, the chromatic aberration can be satisfactorily corrected. Therefore, in order to satisfactorily correct the chromatic aberration, it is necessary to suppress the chromatic aberration generated in the refractive optical system or to enhance the chromatic aberration correcting effect of the negative lens of the catadioptric optical system.

According to paraxial aberration theory, the amount of generation of axial chromatic aberration is generally proportional to the power (refractive power) of the lens, and proportional to the square of the incident height of the paraxial marginal ray. Therefore, in order to enhance the chromatic aberration correction effect of the negative lens of the catadioptric system, it is only necessary to increase the power of the negative lens or increase the light flux incident on the negative lens.

However, when the power of the negative lens is increased, the radius of curvature of the lens surface becomes smaller, and the incident angle of the light beam becomes larger. As a result, high-order aberrations occur, and it becomes difficult to remove aberrations other than chromatic aberration. However, regarding the aberration when the power of the negative lens is increased, the aberration can be removed quite effectively by introducing an aspheric surface. On the other hand, when the incident light beam to the negative lens is made thicker,
Axial chromatic aberration can be removed relatively easily. However, if the light beam incident on the negative lens is made thicker, optical elements such as lenses and reflecting mirrors become larger, and it becomes difficult to manufacture the optical elements with required accuracy. Therefore, there is a limit to increasing the amount of light beam incident on the negative lens.

Next, in order to reduce the occurrence of longitudinal chromatic aberration in the refractive optical system, contrary to the case of the catadioptric system, the power of the lens is reduced or the light beam incident on the lens is not increased. It may be configured as follows. To that end, the presence of a negative lens, which would increase the light flux incident on other lenses and increase the required power of the positive lens, is disadvantageous, and the use of negative lenses in refractive optics should be modest. is there. However, in that case, it is necessary to use an aspherical surface because spherical aberration cannot be removed only with a spherical lens. The introduction of an aspherical surface also has the advantage that aberration can be suppressed with a smaller number of lenses than in a spherical system. However, even if an aspherical surface is introduced, the Petzval sum cannot be adjusted only by the positive lens, and thus the curvature of field necessarily occurs. However, the curvature of field can be canceled out by the effect of the concave reflecting mirror of the catadioptric system or the negative lens.

On the other hand, in order to avoid the absorption of light by air, the entire optical system including the mask (reticle) and the wafer must be made airtight and replaced with an inert gas such as helium which hardly absorbs light. Is preferred. However, since the mask and the wafer repeatedly move during use of the projection exposure apparatus, it is difficult to configure the entire optical system including the mask and the wafer in an airtight state. Therefore, a light-transmitting optical member is arranged near the mask and near the wafer, and other optical members having a refractive power (lens, concave reflecting mirror, convex reflecting mirror,
In order to keep the diffractive optical element (including a diffractive optical element, etc.) away from the external atmosphere, it is practical to keep the space between the optical member near the mask and the optical member near the wafer in an airtight state.

In general, in a projection optical system, a lens is arranged close to a wafer. Therefore, in the present invention, a light transmitting optical member is provided near a mask. Note that a lens or a plane-parallel plate may be used as the light-transmitting optical member. However, if a parallel flat plate that is easy to process and handle is used, the parallel flat plate can be replaced relatively easily while maintaining the performance of the optical system even when the surface becomes dirty. When the inside of the projection optical system is kept airtight, the portion to which dirt adheres is limited to the portion exposed to the outside, that is, the parallel plate on the mask side and the lens on the wafer side. In the present invention, the durability and maintainability of the projection optical system can be improved by replacing the parallel flat plate on the mask side to which dirt easily adheres.

Further, even after the assembly and rough adjustment of the projection optical system are completed, the various aberrations remaining in the projection optical system can be corrected by performing micromachining on the surface of the parallel flat plate disposed near the mask. Is possible. In particular, in the case of a reduction type projection optical system, distortion can be effectively corrected by micro-machining a parallel flat plate arranged near a mask. If necessary, a parallel flat plate can be provided near the wafer. In this case, the spherical aberration and coma aberration can be effectively corrected by micro-machining the parallel flat plate disposed near the wafer.

FIG. 1 is a conceptual diagram schematically illustrating a basic configuration of a projection optical system of a projection exposure apparatus according to the present invention. As shown in FIG. 1, the projection optical system according to the present invention includes a catadioptric optical system A at the front side (mask side) of the intermediate image I.
And a refractive optical system B on the rear (wafer side) portion. That is, an intermediate image I is formed by the first image forming optical system composed of the catadioptric optical system A based on the light from the mask R, and a second image formed by the refractive optical system B based on the light from the intermediate image I. A mask pattern image is formed on the wafer W by the optical system.

The optical axis of the projection optical system may be bent by a concave reflecting mirror or bent by a reflecting surface (not shown in FIG. 1) arranged for separating the optical path. Except for the reflective optical member and the refractive optical member, they are arranged on the optical axis. Hereinafter, in the description of the catadioptric optical system A and the dioptric optical system B, it is assumed that a reflective surface for bending the optical path is excluded. The catadioptric optical system A includes a plurality of lenses (G1, G
2) and one concave reflecting mirror (M). The optical axis of the catadioptric system A is folded back by the concave reflecting mirror M. In order to avoid interference of light rays due to turning back of the optical path in the concave reflecting mirror M, that is, in order to separate light incident on the concave reflecting mirror M and light emitted from the concave reflecting mirror M, the mask R surface as an object surface Must be removed (eccentric) from the optical axis. Also, the wafer W surface needs to be decentered from the optical axis in accordance with the eccentricity of the mask R from the optical axis.

In order to favorably suppress the occurrence of aberration,
It is preferable that the concave reflecting mirror M is disposed near a position corresponding to the aperture stop of the catadioptric optical system A, and that the optical system is substantially symmetrical and substantially equal in magnification with respect to the concave reflecting mirror M. In the catadioptric system A, a lens group G2 having a negative refractive power as a whole is disposed at a position closest to the concave reflecting mirror M. In addition, in this specification, a lens group is
This is a broad concept that includes one single lens. This negative lens group G2 satisfactorily corrects axial chromatic aberration generated in the refractive optical system B. In order to satisfactorily correct chromatic aberration over a wide band in a wide-field projection optical system, it is desirable that the negative lens group G2 uses an aspherical lens or uses a plurality of lenses.

In the optical path between the negative lens group G2 and the mask R, a positive lens group G1 having at least one positive lens as a whole (a lens group including at least one positive lens) is disposed. The positive lens group G1 has a function of giving the luminous flux from the mask R telecentricity.
It is possible to make the object side (mask side) resistant to a change in focus. In addition, we remove distortion,
The positive lens group G1 is also useful for preventing the curvature of field from being excessively generated in the intermediate image I. In the intermediate image I formed by the catadioptric optical system A, it is preferable that various aberrations other than chromatic aberration are satisfactorily corrected. However, when the number of lenses constituting the catadioptric optical system A is reduced, it is inevitable that some aberration such as field curvature remains in the intermediate image I.

On the other hand, the refractive optical system B is composed of a positive lens group G3 arranged on the mask side with the aperture stop S interposed therebetween and a positive lens group G4 arranged on the wafer side. That is, the refractive optical system B is an optical system including only a refractive optical member such as a lens without including a concave reflecting mirror. In the catadioptric optical system A, since the optical path is folded by the concave reflecting mirror, an aperture stop cannot be arranged in the optical path.
The aperture stop S of the projection optical system is arranged in the optical path of the refractive optical system B.

As described above, in order to properly suppress the occurrence of axial chromatic aberration in the refractive optical system B, it is advantageous to prevent the light beam incident on the lens from becoming too thick.
However, in this case as well, since various aberrations are generated by increasing the power of the lens, it is preferable that the effective diameter of the lens satisfies the following conditional expression (1). 0.7 <h1 / h2 <1.4 (1) Here, h1 is the maximum effective diameter of the lens of the catadioptric optical system A that is the first imaging optical system. Further, h2 is the maximum effective diameter of the lens of the refractive optical system B that is the second imaging optical system.

When the ratio falls below the lower limit of conditional expression (1), h1 /
Since the value of h2 becomes too small, it becomes difficult to remove chromatic aberration, which is not preferable. On the other hand, if the value exceeds the upper limit of conditional expression (1), the value of h1 / h2 becomes too large, and it becomes difficult to correct spherical aberration or the like in the refractive optical system B, or the optical member of the catadioptric optical system A Is too large to make it difficult to manufacture. Note that, even within the range that satisfies the conditional expression (1), it is advantageous to use an aspheric surface for aberration correction in the refractive optical system B.

As described above, in the projection optical system of the present invention shown in FIG. It is necessary to separate the luminous flux going to. As a result, as shown in FIG. 2, the area that can be used for image formation on the surface of the wafer W, that is, the usable area FR is a half of the circular area around the optical axis AX from which aberration has been removed. Become. In the present invention, the exposure region ER actually used for exposure is a rectangular region obtained by removing a boundary region near the optical axis AX from a semicircular usable region FR, for example. Correspondingly, a visual field area (illumination area) defined on the mask R via the projection optical system
Also have a rectangular shape.

In the present invention, a light-transmitting optical member P1 such as a plane-parallel plate is disposed near the mask R. Specifically, the distance between the mask R and the plane parallel plate P1 along the optical axis (or a direction parallel to the optical axis) of the projection optical system is set to 50 mm or less. If necessary,
A light-transmitting optical member P2 such as a plane-parallel plate may be arranged near the wafer W. Therefore, the mask R
Is maintained in an airtight state from the parallel plane plate P1 disposed in the vicinity of P to the parallel plane plate P2 disposed in the vicinity of the wafer W (or the lens closest to the wafer), and the helium hardly absorbs exposure light. The inside of the optical system can be filled with an inert gas such as (He) or nitrogen (N ₂ ).

That is, except for a narrow optical path between the mask R and the plane-parallel plate P1 and a narrow optical path between the wafer W and an optical member adjacent thereto, almost all of the optical path from the mask R to the wafer W is It can be filled with an inert gas such as helium, which hardly absorbs light. As a result, F
_{(2) Even when} short-wavelength light such as laser light is used, light absorption can be effectively avoided, and the transmission efficiency of the projection optical system can be improved. Here, when short-wavelength light having a wavelength of 180 nm or less, such as F ₂ laser light, is used as the exposure light, a narrow optical path between the mask R and the plane parallel plate P1 and the wafer W and an optical member adjacent thereto are used. Is filled with the inert gas. However, on these optical paths, a movable mask stage 6 and a movable wafer stage 10 are arranged, and due to the influence of scattering of dust and grease from these movable members, the cleanness of the inert gas itself is reduced. (Cleanness) is the optical path (parallel plane plate P1 to parallel plane plate P2) inside the projection optical system.
Or, there is a high possibility that the degree of cleaning is lower than the degree of cleanness of the optical path to the lens closest to the wafer. Therefore, even if the entire optical path from the mask R to the wafer W is filled with the inert gas, the optical path with low cleanliness can be made very short in the present invention. In other words, the optical path with low cleanliness can be separated. Thus, the effect of reducing the light quantity loss can be further improved.
Here, the distance along the direction parallel to the optical axis between the mask R and the plane parallel plate P1 (an optical member disposed close to the mask and having an optical power and having a refractive power from an external atmosphere) is 50 mm. When the length is longer than the above, the optical path having a low cleanliness becomes too long as described above, and the risk of an increase in light amount loss increases, which is not preferable. The distance between the mask R and the plane parallel plate P1 along the direction parallel to the optical axis is 1 unit.
If the distance is less than mm, it is very difficult to design the mask stage so as not to interfere with the plane-parallel plate P1 and the mask stage, and it is difficult to improve the accuracy of the mask stage itself, which is not preferable. Also,
When the distance between the mask R and the plane parallel plate P1 along the direction parallel to the optical axis is 5 mm or less, a design that does not interfere with the mask R and the plane parallel plate P1 while maintaining the accuracy of the mask stage is required. Is not preferred. When the distance between the mask R and the plane parallel plate P1 along the direction parallel to the optical axis is 20 mm or less, the interference between the mask R and the plane parallel plate P1 may be reduced by a small improvement of the existing mask stage. It is not preferable because it cannot be avoided. Also, as mentioned above,
The use of the plane-parallel plate improves the durability and maintainability of the projection optical system, and makes it possible to correct the residual aberration after assembling the projection optical system.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. [First Embodiment and Second Embodiment] FIG. 3 shows a first embodiment of the present invention.
FIG. 4 is a diagram schematically illustrating an overall configuration of a projection exposure apparatus according to an example and a second example. In FIG. 3, the Z-axis is set in the normal direction of the wafer surface, the X-axis is set in the wafer surface in parallel to the plane of FIG. 3, and the Y-axis is set perpendicular to the plane of FIG.
In the projection exposure apparatus shown in the figure, the light emitted in the Z direction from the F ₂ laser (oscillation center wavelength 157.6 nm) 1 is deflected in the X direction by the bending mirror 2 and then the illumination optical system 3.
The mask 4 is uniformly illuminated via. In FIG. 3,
Although only one folding mirror 2 is shown in the optical path from the light source 1 to the illumination optical system 3, in practice, when the light source 1 and the projection exposure apparatus main body are separate bodies, the F ₂
And automatic tracking unit for directing the orientation of the 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,
An optical system such as a light amount adjustment unit is provided. The illumination optical system 3 shown in FIG. 3 includes, for example, an optical integrator formed of a fly-eye lens or an internal reflection type integrator to form a surface light source of a predetermined size and shape, and a mask 4.
It has an optical system such as a field stop for defining the size and shape of the illumination area above, and a field stop imaging optical system for projecting an image of the field stop onto a mask. In the example of FIG. 3, the space between the light source 1 and the illumination optical system 3 is sealed by a casing C1. It has been replaced with an active gas. It is needless to say that the way of bending the optical path is not limited to the mode shown in FIG.

The mask 4 is held on a mask stage 6 via a mask holder 5 in parallel with the YZ plane. A pattern to be transferred is formed on the mask 4, and a rectangular pattern area having a long side along the Z direction and a short side along the Y direction in the entire pattern area is illuminated. The mask stage 6 can be moved two-dimensionally along the mask plane (that is, the YZ plane) by the action of a drive system (not shown), and its position coordinates are measured by an interferometer 12 using a mask moving mirror 11. And it is comprised so that position control may be carried out.

Light from the pattern formed on the mask 4 is transmitted through a projection optical system 7 to a wafer 8 serving as a photosensitive substrate.
A mask pattern image is formed thereon. The wafer 8 is placed on the wafer stage 10 via the wafer holder 9 in XY
It is held parallel to the plane. Then, the wafer 8 is optically corresponded to a rectangular illumination area on the mask 4.
Above, a pattern image is formed in a rectangular exposure region having a long side along the X direction and a short side along the Y direction. The wafer stage 10 can be moved two-dimensionally along the wafer surface (that is, the XY plane) by the action of a drive system (not shown).
It is configured to be measured and position-controlled by an interferometer 14 using.

In the projection exposure apparatus shown in the drawing, of the optical members constituting the projection optical system 7, the parallel plane plate P1 arranged closest to the mask and the lens L arranged closest to the wafer
r, the inside of the projection optical system 7 is kept airtight, and the gas inside the projection optical system 7 is replaced by helium gas, which is a gas having a low absorptance of exposure light. Similarly, the optical path from the light source 1 to the illumination optical system 3 is also replaced with helium gas. A mask 4 and a mask stage 6 are arranged in a narrow optical path between the illumination optical system 3 and the plane-parallel plate P1. Nitrogen or the like is provided inside a casing C2 that hermetically surrounds the mask 4 and the mask stage 6. By filling with an inert gas such as helium gas, the optical path between the illumination optical system 3 and the plane-parallel plate P1 is replaced with the inert gas. In a narrow optical path between the lens Lr and the wafer 8, the wafer 8 and the wafer stage 10 are arranged.
Is filled with an inert gas such as nitrogen or helium gas, whereby a narrow optical path between the lens Lr and the wafer 8 is replaced with the inert gas. However, since mechanically movable members (such as the mask stage 6 and the wafer stage 10) are arranged in these optical paths, it is unavoidable that the degree of gas cleanness is reduced by moving these members. In addition,
It is preferable that the robot arm for exchanging the mask and the robot arm for exchanging the wafer be housed in a casing separate from the casings C2 and C3 in order to improve the optical path cleanliness. Still, the degree of cleanliness of the gas inside the projection optical system 7 tends to be lower. As described above, the portion where the exposure light passes through the gas with low cleanliness in the optical path from the light source 1 to the wafer 8 is located in the narrow optical path between the illumination optical system 3 and the mask 4 and the mask 4 and the parallel flat plate P1. And in the narrow optical path between the lens Lr and the wafer 8.

As described above, the field of view (illumination area) on the mask 4 and the projection area (exposure area) on the wafer 8 defined by the projection optical system 7 are rectangular shapes having short sides along the Y direction. It is. Therefore, the mask 4 and the wafer 8 are formed by using a drive system and interferometers (12, 14).
Is moved synchronously (scanning) between the mask stage 6 and the wafer stage 10 and, consequently, the mask 4 and the wafer 8 along the short side direction of the rectangular exposure area and the illumination area, that is, in the Y direction. As a result, the mask pattern is scanned and exposed on the wafer 8 in a region having a width equal to the long side of the exposure region and a length corresponding to the scanning amount (movement amount) of the wafer 8. Thus, the first
In the embodiment and the second embodiment, the mask surface and the wafer surface are orthogonal to each other, but the scanning direction is set to be horizontal.

In each of the embodiments (including the third and fourth embodiments described later), fluorite (CaF ₂ crystal) is used for all the lens components and the plane parallel plate constituting the projection optical system 7. are doing. The oscillation center wavelength of the F ₂ laser light as the exposure light is 157.6 nm, and 157.6 n
In the vicinity of m, the refractive index of CaF ₂ changes at a rate of −2.4 × 10 ⁻⁶ per wavelength change of +1 pm, and changes at a rate of + 2.4 × 10 ⁻⁶ per wavelength change of −1 pm. Also,
The exposure area ER on the wafer 8 has a rectangular shape of 25 mm × 6.6 mm, and has a distance LX from the optical axis AX to the exposure area ER.
Is 4 mm (see FIG. 2). That is, the exposure area ER by the projection optical system of each embodiment is located at a position decentered from the optical axis AX.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is defined as y, and the aspheric surface extends along the optical axis from the tangent plane at the vertex of the aspheric surface to a position on the aspheric surface at the height y. Distance (sag amount) as z, vertex curvature radius as r,
Assuming that the conic coefficient is κ and the n-th order aspherical coefficient is Cn, it is represented by the following equation (a).

[Number 1] ^{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 (a) In each embodiment, the cone coefficient κ of each aspherical surface is all zero. In addition, an asterisk is attached to the right side of the surface number on the lens surface formed in an aspherical shape.

In terms of transmittance for exposure light, Li
Although F can be used, it is extremely difficult to use LiF having deliquescence for the illumination optical system 3 and the projection optical system 7. Since MgF ₂ has birefringence, it cannot be used for the projection optical system 7. However, the illumination optical system 3 may have some birefringence. _In addition to the optical member made of ₂ , an optical member made of MgF ₂ can be used.

[First Embodiment] FIG. 4 is a diagram showing a lens configuration of a projection optical system according to a first embodiment, including an optical axis connecting the concave reflecting mirror M2 and the wafer surface (image surface). It is sectional drawing along the plane perpendicular | vertical to a mask surface (object surface). Also,
FIG. 5 is a view corresponding to FIG. 4 and is a cross-sectional view along a plane that includes an optical axis connecting the concave reflecting mirror M2 and the wafer surface (image surface) and is parallel to the mask surface. However, in FIG. 5, for the sake of clarity, the reflecting mirror M1 is omitted, and the optical path from the reflecting mirror M1 to the mask R (corresponding to reference numeral 4 in FIG. 3) is developed on the paper. In the first embodiment, the center wavelength is 15
The present invention is applied to a projection optical system in which various aberrations including chromatic aberration are corrected for exposure light having a full width at half maximum of 2 pm at 7.6 nm.

In the projection optical system shown in FIG.
No. 695, the reflecting mirror disposed near the intermediate image forming position is removed, and instead, the light is reflected immediately behind (the wafer side) the parallel flat plate P1 disposed near the mask R. The separation of the optical path is ensured by arranging the mirror M1 and bending the optical axis. In the case of the projection optical system of the first embodiment, the plane parallel plate P arranged near the mask R
Except for the reflecting mirror 1 and the immediately following reflecting mirror M1, all lens components and the concave reflecting mirror M2 constituting the catadioptric optical system A and the dioptric optical system B are arranged on the same optical axis.
There is an advantage that assembly and adjustment of the optical system are easy.

The projection optical system according to the first embodiment includes a plane parallel plate P1 arranged close to a mask R, and a plane parallel plate P
And a plane reflecting mirror M1 for reflecting the light from the mask R via the light guide 1 and guiding the light to the catadioptric optical system A. The catadioptric optical system A includes, in order from the incident side of light from the mask R, a positive meniscus lens L1 having a convex surface facing the incident side, a positive meniscus lens L2 having a convex surface facing the incident side, and a convex surface facing the incident side. A negative meniscus lens L3, a negative meniscus lens L4 having a concave surface facing the incident side, and a concave reflecting mirror M2 having a concave surface facing the incident side. Therefore,
The light from the mask R passes through the plane-parallel plate P1, is reflected by the plane reflecting mirror M1, and then enters the catadioptric system A. The light that has entered the catadioptric optical system A enters the concave reflecting mirror M2 via four lens components L1 to L4. The light reflected by the concave reflecting mirror M2 has four lens components L4 to L4.
An intermediate image of the mask pattern is formed via L1.

Light from the intermediate image of the mask pattern is guided to the refractive optical system B. The refractive optical system B includes, in order from the incident side of light from the intermediate image, a positive meniscus lens L5 having a convex surface directed to the incident side, a biconvex lens L6, and a biconcave lens L7.
A positive meniscus lens L8 having a concave surface on the incident side, a positive meniscus lens L9 having a convex surface on the incident side, a positive meniscus lens L10 having a convex surface on the incident side, and a positive meniscus lens L11 having a convex surface on the incident side. And a biconvex lens L
12, a negative meniscus lens L1 having a concave surface facing the incident side
3 and a biconvex lens L14. In addition,
Positive meniscus lens L10 and positive meniscus lens L11
An aperture stop S is arranged in the optical path between the aperture stop S.

Therefore, the light incident on the refracting optical system B from the intermediate image of the mask pattern depends on the lens components L5 to L1.
4, a reduced image of the mask pattern is formed in an exposure area on the wafer W (corresponding to reference numeral 8 in FIG. 3). As described above, in the optical path from the concave reflecting mirror M2 to the biconvex lens L14, the concave reflecting mirror M2 and all lens components L1 to L14 are arranged along the common optical axis AX. In the projection optical system of the first embodiment, the plane mirror M1 is located in the optical path between the catadioptric optical system A and the dioptric optical system B and does not include the optical axes of these optical systems A and B. It is inclined at 45 ° to the optical axis. Therefore, the light beam traveling from the catadioptric system A to the dioptric system B passes through the space on the opposite side of the plane mirror M1 with respect to the optical axis.

Table 1 below summarizes the data values of the projection optical system of the first embodiment. In Table (1), λ represents the central wavelength of the exposure light, FWHM represents the full width at half maximum of the exposure light, β represents the projection magnification, and NA represents the image-side numerical aperture. The surface number indicates the order of the surface from the mask side along the direction in which the light beam travels from the mask surface, which is the object surface, to the wafer surface, which is the image surface. Is the radius of curvature of the apex), d is the on-axis interval of each surface, that is, the surface interval, and n is the refractive index for the center wavelength.

It is assumed that the sign of the surface distance d is changed each time it is reflected. Therefore, the sign of the surface distance d is negative in the optical path from the plane reflecting mirror M1 to the concave reflecting mirror M2, and positive in other optical paths. And
In the optical path where the surface distance d is positive, the radius of curvature of the convex surface toward the light incident side is positive, and the radius of curvature of the concave surface is negative. Conversely, in the optical path where the surface distance d is negative, the radius of curvature of the concave surface toward the light incident side is positive,
The radius of curvature of the convex surface is negative.

[0050]

[Table 1] (Main specifications) λ = 157.6 nm FWHM: 2 pm β = 1/4 NA = 0.65 (Optical member specifications) Surface number r dn (Mask surface) 20.000000 1 ∞ 10.000000 1.5600000 (P1) 2 ∞ 95.000000 3 ∞ -147.362588 (M1) 4 -429.08398 -30.000000 1.5600000 (L1) 5 * -745.13029 -1.333333 6 -322.16303 -40.000000 1.5600000 (L2) 7 * -1467.70271 -167.804804 8 -1453.48942 -30.000000 1.5600000 (L3) 9 * -499.97211 -270.398999 10 * 169.56369 -24.634368 1.5600000 (L4) 11 1553.82168 -29.845669 12 270.33617 29.845669 (M2) 13 1553.82168 24.634368 1.5600000 (L4) 14 * 169.56369 270.398999 15 * -499.97211 30.000000 1600000 -1467.70271 40.000000 1.5600000 (L2) 18 -322.16303 1.333333 19 * -745.13029 30.000000 1.5600000 (L1) 20 -429.08398 367.362588 21 251.44318 56.000000 1.5600000 (L5) 22 * 331.45187 0.100000 23 242.35691 64.000000 1.5600 000 (L6) 24 * -435.60082 41.312455 25 -383.72254 35.200000 1.5600000 (L7) 26 * 234.88321 351.340242 27 * -368.96810 35.200000 1.5600000 (L8) 28 -213.21187 0.100000 29 222.15200 38.214400 1.5600000 (L9) 30 * 644.25611 1.55.2000004 (L10) 32 670.73134 14.613691 33 ∞ 22.968043 (S) 34 194.20796 25.000000 1.5600000 (L11) 35 1066.41016 39.793405 36 269.58088 47.757164 1.5600000 (L12) 37 * -250.46386 1.151770 38 -252.91748 20.000000 1.5600000 (L13) 39 * 84. 1.5600000 (L14) 41 -306.38001 5.000940 (wafer surface) (aspherical data) r kappa C ₄ 5 faces -745.13029 0.00000 -0.366339 × 10 ^-8 19 surface _{C 6 C 8 C 10 0.457313 ×} 10 -13 0.205872 × 10 -16 _{^{0.184274 × 10 -21 r κ C 4}} 7 surface -1467.70271 0.00000 0.846545 × 10 ^-9 17 surface _{C 6 C 8 C 10 -0.116191 ×} 10 -12 -0.199473 × 10 -16 -0.341653 × 10 -21 r κ C 4 9 Face -499.97211 0 .00000 -0.976158 × 10 ^-8 15 side C ₆ C ₈ C ₁₀ -0.415843 × 10 ^-13 0.162351 × 10 ^-16 0.411877 × 10 ^-21 r κ C ₄ 10 side 169.56369 0.00000 -0.133118 × 10 ^-7 14 side C ₆ C ₈ C ₁₀ -0.346654 × 10 ^-12 -0.781223 × 10 ^-17 -0.342202 × 10 ^-21 r κ C ₄ 22 surface 331.45187 0.00000 0.757965 × 10 ^-8 C ₆ C ₈ C ₁₀ -0.101485 × 10 ^-12 0.496639 × 10 ^-17 0.112493 × 10 ^-22 r κ C ₄ 24 face -435.60082 0.00000 0.751565 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.347171 × 10 ^-12 -0.222 122 × 10 ^-16 0.414382 × 10 ^-21 r κ C ₄ 26 face 234.88321 _{^{0.00000 0.330921 × 10 -8 C 6 C}} 8 C 10 -0.496173 × 10 -12 0.642966 × 10 -16 -0.215905 × 10 -20 r κ C 4 27 faces _{^{-368.96810 0.00000 -0.772938 × 10 -8 C 6}} C 8 C 10 ^{-0.292091 × 10 -12 0.455626 × 10 -17} -0.159769 × 10 -21 r κ C 4 30 faces _{^{644.25611 0.00000 0.121893 × 10 -7 C 6}} C 8 C 10 -0.203227 × 10 -12 0.838252 × 10 -17 -0.132351 × 10 ^-21 r κ C ₄ 37 -250.46386 0.00000 0.100880 × 10 ^-6 C ₆ C ₈ C ₁₀ 0.464133 × 10 ^-11 -0.276297 × 10 ^{-14 0.186151 × 10 -18 r κ C} 4 39 faces _{^{-5180.17894 0.00000 -0.212613 × 10 -7 C 6}} C 8 C 10 -0.222172 × 10 -10 0.137730 × 10 -13 -0.124632 × 10 -17 r κ C 4 40 Surface 115.59157 0.00000 -0.432337 × 10 ^-7 C ₆ C ₈ C ₁₀ -0.741893 × 10 ^-11 0.488072 × 10 ^-14 0.112316 × 10 ^-17

FIG. 6 is a diagram showing spherical aberration, astigmatism, and distortion in the first embodiment. Also, FIG.
Lateral aberration (meridional coma) in the first embodiment
FIG. In each aberration diagram, NA represents the image-side numerical aperture, Y represents the image height, the solid line represents the central wavelength of 157.6 nm, the broken line represents 157.6 nm + 1.3 pm, and the one-dot chain line represents 15 minutes.
7.6 nm-1.3 pm are shown, respectively. Also,
In the aberration diagram showing astigmatism, S indicates a sagittal image plane, and M indicates a meridional image plane. As is clear from the aberration diagrams, in the first embodiment, the center wavelength is 15
It can be seen that various aberrations including chromatic aberration are well corrected for exposure light having a full width at half maximum of 2 pm at 7.6 nm.

[Second Embodiment] FIG. 8 is a diagram showing a lens configuration of a projection optical system according to a second embodiment, including an optical axis connecting the concave reflecting mirror M2 and the wafer surface (image surface). It is sectional drawing along the plane perpendicular | vertical to a mask surface (object surface). Also,
FIG. 9 is a view corresponding to FIG. 8, and is a cross-sectional view along a plane that includes an optical axis connecting the concave reflecting mirror M2 and the wafer surface (image surface) and is parallel to the mask surface. However, in FIG. 8, for clarity of the drawing, the reflecting mirror M1 is omitted, and the optical path from the reflecting mirror M1 to the mask R is developed on the paper. In the second embodiment, the center wavelength is 157.6 nm and the full width at half maximum is 10p.
The present invention is applied to a projection optical system in which various aberrations including chromatic aberration are corrected for m exposure light.

The projection optical system according to the second embodiment has a configuration similar to that of the first embodiment. However, the full width at half maximum of the exposure light is 2 pm in the first embodiment, whereas the full width at half maximum of the exposure light is 10 pm in the second embodiment. The second embodiment basically differs from the second embodiment in that it has five lens components corresponding to an increase in the full width at half maximum of the exposure light. Hereinafter, focusing on the differences from the first embodiment,
An embodiment will be described.

The projection optical system according to the second embodiment includes a plane parallel plate P1 arranged close to a mask R, and a plane parallel plate P
And a plane reflecting mirror M1 for reflecting the light from the mask R via the light guide 1 and guiding the light to the catadioptric optical system A. The catadioptric optical system A includes, in order from the incident side of the light from the mask R, a negative meniscus lens L1 having a convex surface facing the incident side, a biconvex lens L2, a negative meniscus lens L3 having a convex surface facing the incident side, Negative meniscus lens L4 with concave side facing
A negative meniscus lens L5 having a concave surface facing the incident side;
And a concave reflecting mirror M2 having a concave surface facing the incident side. Therefore, the light from the mask R is reflected by the parallel flat plate P
1 and is reflected by the plane reflecting mirror M1, and then enters the catadioptric optical system A. The light incident on the catadioptric optical system A passes through five lens components L1 to L5,
2 is incident. The light reflected by the concave reflecting mirror M2 forms an intermediate image of the mask pattern via the five lens components L5 to L1.

The light from the intermediate image of the mask pattern is guided to the refractive optical system B. The refracting optical system B includes a biconvex lens L6 and a biconvex lens L7 in order from the incident side of light from the intermediate image.
A biconcave lens L8, a biconcave lens L9, a positive meniscus lens L10 having a concave surface on the incident side, a positive meniscus lens L11 having a convex surface on the incident side, and a positive meniscus lens L12 having a convex surface on the incident side. A negative meniscus lens L13 having a convex surface facing the incident side, and a biconvex lens L14
And a biconvex lens L15. Note that an aperture stop S is arranged near the positive meniscus lens L12 in the optical path between the positive meniscus lens L12 and the negative meniscus lens L13.

Therefore, the light incident on the refracting optical system B from the intermediate image of the mask pattern is reflected by the lens components L6 to L1.
5, a reduced image of the mask pattern is formed in the exposure area on the wafer W. As described above, in the optical path from the concave reflecting mirror M2 to the biconvex lens L15, the concave reflecting mirror M2 and all lens components L1 to L
15 are arranged along the common optical axis AX.

Table 2 below summarizes the data values of the projection optical system of the second embodiment. In Table (2), λ represents the center wavelength of the exposure light, FWHM represents the full width at half maximum of the exposure light, β represents the projection magnification, and NA represents the image-side numerical aperture. The surface number indicates the order of the surface from the mask side along the direction in which the light beam travels from the mask surface, which is the object surface, to the wafer surface, which is the image surface. Is the radius of curvature of the apex), d is the on-axis interval of each surface, that is, the surface interval, and n is the refractive index for the center wavelength.

It is assumed that the sign of the surface distance d changes each time it is reflected. Therefore, the sign of the surface distance d is negative in the optical path from the plane reflecting mirror M1 to the concave reflecting mirror M2, and positive in other optical paths. And
In the optical path where the surface distance d is positive, the radius of curvature of the convex surface toward the light incident side is positive, and the radius of curvature of the concave surface is negative. Conversely, in the optical path where the surface distance d is negative, the radius of curvature of the concave surface toward the light incident side is positive,
The radius of curvature of the convex surface is negative.

[0059]

(Main specifications) λ = 157.6 nm FWHM: 10 pm β = 1/4 NA = 0.65 (optical member specifications) Surface number r dn (mask surface) 20.000000 1 ∞ 10.000000 1.5600000 (P1) 2 ∞ 95.000000 3 ∞ -149.717330 (M1) 4 -682.92265 -30.000000 1.5600000 (L1) 5 * -588.26859 -1.333333 6 -430.94316 -40.000000 1.5600000 (L2) 7 * 1484.17685 -150.777176 8 -267.06519 -30.000000 1.5600000 (L3) 9 * -264.72399 -271.803380 10 * 280.88127 -40.000000 1.5600000 (L4) 11 430.96701 -47.259520 12 * 173.49424 -24.634368 1.5600000 (L5) 13 875.59639 -23.962719 14 283.82726 23.962719 (M2) 15 875.59639 24.634368 1.5600000 (L5) 1700004. 1.5600000 (L4) 18 * 280.88127 271.803380 19 * -264.72399 30.000000 1.5600000 (L3) 20 -267.06519 150.777176 21 * 1484.17685 40.000000 1.5600000 (L2) 22 -430.94316 1.333333 23 * -588.26859 30.000000 1.56000 00 (L1) 24 -682.92265 369.717330 25 238.57662 60.000000 1.5600000 (L6) 26 * -1018.49483 0.100000 27 537.43794 60.000000 1.5600000 (L7) 28 * -1553.84088 5.862119 29 -871.09012 33.333333 1.5600000 (L8) 30 * 889.60239 20.205850 300000 L9) 32 * 370.25580 345.890970 33 * -374.83682 35.200000 1.5600000 (L10) 34 -212.27674 0.100000 35 252.25212 34.214400 1.5600000 (L11) 36 * 1101.27714 41.001563 37 158.00018 43.110144 1.5600000 (L12) 38 * 426.66235 11.75164739 411 71. 1.5600000 (L13) 41 * 129.89231 5.696443 42 111.81396 20.000000 1.5600000 (L14) 43 * -713.41458 0.684288 44 * 139.86748 53.916336 1.5600000 (L15) 45 -390.69540 5.000000 ( wafer surface) (aspherical data) r kappa C ₄ 5 faces -588.26859 0.00000 -0.231151 × 10 ^-8 23 face C ₆ C ₈ C ₁₀ -0.107657 × 10 ^-12 0.679561 × 10 ^-17 0.200076 × 10 ^-21 r κ C ₄ 7 face 1484.17 685 0.00000 0.208708 × 10 ^-8 21 face C ₆ C ₈ C ₁₀ 0.101520 × 10 ^-12 -0.936224 × 10 ^-17 -0.109080 × 10 ^-21 r κ C ₄ 9 face -264.72399 0.00000 -0.596956 × 10 ^-8 19 face C ₆ C ₈ C ₁₀ -0.804 409 × 10 ^-13 0.594035 × 10 ^-17 -0.511225 × 10 ^-22 r κ C ₄ 10 face 280.88127 0.00000 -0.270 202 × 10 ^-8 18 face C ₆ C ₈ C ₁₀ -0.165650 × 10 ^{-12 -0.319705 × 10 -17 -0.722147 × 10 -21} r κ C 4 12 faces 173.49424 0.00000 -0.896367 × 10 ^-8 16 surface _{C 6 C 8 C 10 -0.112007 ×} 10 -12 -0.376263 × 10 -18 0.205531 × 10 - ²² r ^κ C ₄ 26 faces _{^{-1018.49483 0.00000 -0.161303 × 10 -8 C 6}} C 8 C 10 -0.132885 × 10 -13 0.112230 × 10 -16 -0.279049 × 10 -21 r κ C 4 28 faces -1553.84088 0.00000 0.178392 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.484443 × 10 ^-13 -0.385332 × 10 ^-16 0.135532 × 10 ^-20 r κ C ₄ 30 889.60239 0.00000 0.252762 × 10 ^-7 C ₆ C ₈ C ₁₀ 0.592624 × 10 ^-12 0.146825 × 10 ^-16 -0.127357 × 10 ^-20 r κ C ₄ 32 planes 370.255 800 0.00000 -0.427239 × 10 ^-8 C ₆ C ₈ C ₁₀ -0. ^{252357 × 10 -12 0.611208 × 10 -16} 0.198023 × 10 -21 r κ C 4 33 faces _{^{-374.83682 0.00000 -0.713446 × 10 -8 C 6}} C 8 C 10 -0.358473 × 10 -12 0.976519 × 10 -17 -0.144877 × 10 ^-21 r κ C ₄ 36 faces _{^{1101.27714 0.00000 0.813610 × 10 -8 C 6}} C 8 C 10 -0.519537 × 10 -12 0.103493 × 10 -16 0.452136 × 10 -22 r κ C 4 38 faces 426.66235 0.00000 0.202344 × 10 ^{- _{7 C 6 C 8 C 10 0.486990}} × 10 -12 -0.709243 × 10 -17 0.198192 × 10 -21 r κ C 4 41 faces _{^{129.89231 0.00000 0.379939 × 10 -7 C 6}} C 8 C 10 0.248170 × 10 -10 0.278364 × 10 ^{-14 0.221665 × 10 -18 r κ C} 4 43 faces _{^{-713.41458 0.00000 -0.142505 × 10 -7 C 6}} C 8 C 10 -0.128262 ×
^{10 -11 0.598993 × 10 -15 0.779998 ×} 10 -19 r κ C 4 44 faces _{^{139.86748 0.00000 -0.921480 × 10 -7 C 6}} C 8 C 10 0.175784 × 10 -10 0.573035 × 10 -14 0.703403 × 10 -18

FIG. 10 shows the spherical aberration in the second embodiment,
It is a figure showing astigmatism and distortion. FIG.
FIG. 9 is a diagram showing lateral aberration (meridional coma) in the second example. In each aberration diagram, NA is the image-side numerical aperture, Y is the image height, and the solid line is the center wavelength of 157.6 nm.
, The dashed line indicates 157.6 nm + 8.6 pm, and the dashed line indicates 157.6 nm-8.6 pm. In the aberration diagrams showing astigmatism, S indicates a sagittal image plane, and M indicates a meridional image plane. As is clear from the aberration diagrams, the center wavelength is 1 in the second embodiment.
It can be seen that various aberrations including chromatic aberration are satisfactorily corrected for exposure light having a full width at half maximum of 10 pm at 57.6 nm.

[Third Embodiment and Fourth Embodiment] FIG.
FIG. 4 is a view schematically showing an overall configuration of a projection exposure apparatus according to a third embodiment and a fourth embodiment of the present invention. In FIG. 12, the Z axis is set in the normal direction of the wafer surface, the X axis is set in the wafer surface in parallel with the plane of FIG. 12, and the Y axis is set perpendicular to the plane of FIG. The third and fourth embodiments are:
It has a configuration similar to the first and second embodiments, but
The configuration of the projection optical system is basically different from the first and second embodiments. Hereinafter, the third embodiment and the fourth embodiment will be described, focusing on the differences from the first embodiment and the second embodiment.

In the illustrated projection exposure apparatus, the light emitted in the X direction from the F ₂ laser (oscillation center wavelength 157.6 nm) 1 is deflected in the Z direction by the bending mirror 2,
The mask 4 is uniformly illuminated via the illumination optical system 3. Although only one bending mirror 2 is shown in the optical path from the light source 1 to the illumination optical system 3 in FIG. 12, actually, as in the example of FIG. 3, the automatic tracking unit and the shaping optical system And an optical system such as a light amount adjustment unit. Also,
The illumination optical system 3 shown in FIG. 12 has an optical system such as an optical integrator, a field stop, and a field stop imaging optical system, as in the example of FIG. Also in the example of FIG. 12, similarly to the example of FIG. 3, the space between the light source 1 and the illumination optical system 3 is sealed with a casing C <b> 1, and from the light source 1 to the optical member closest to the mask R in the illumination optical system 3. Is replaced by an inert gas such as helium gas. It is needless to say that the bending method of the optical path is not limited to the mode shown in FIG. 12, and can be changed as appropriate in accordance with the design of the device. The mask 4 is held on a mask stage 6 via a mask holder 5 in parallel with the XY plane. A pattern to be transferred is formed on the mask 4, and a rectangular pattern area having a long side along the Y direction and a short side along the X direction in the entire pattern area is illuminated. The mask stage 6 can be moved two-dimensionally along the mask surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are measured by an interferometer 12 using a mask moving mirror 11. In addition, the position is controlled.

The light from the pattern formed on the mask 4 is transmitted through a projection optical system 7 to a wafer 8 serving as a photosensitive substrate.
A mask pattern image is formed thereon. The wafer 8 is placed on the wafer stage 10 via the wafer holder 9 in XY
It is held parallel to the plane. Then, in order to optically correspond to the rectangular illumination pattern area on the mask 4,
Also on the wafer 8, it 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 10 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 measured by an interferometer 14 using a wafer moving mirror 13. And it is comprised so that position control may be carried out.

In the projection exposure apparatus shown in the drawing, of the optical members constituting the projection optical system 7, the parallel plane plate P1 arranged closest to the mask and the lens L arranged closest to the wafer
r, the inside of the projection optical system 7 is kept airtight, and the gas inside the projection optical system 7 is replaced with helium gas as a gas having a low absorptance of exposure light. Similarly, the optical path from the light source 1 to the illumination optical system 3 is also replaced with helium gas. A mask 4 and a mask stage 6 are arranged in a narrow optical path between the illumination optical system 3 and the plane-parallel plate P1. Nitrogen or the like is provided inside a casing C2 that hermetically surrounds the mask 4 and the mask stage 6. By filling with an inert gas such as helium gas, the optical path between the illumination optical system 3 and the plane-parallel plate P1 is replaced with the inert gas. In a narrow optical path between the lens Lr and the wafer 8, the wafer 8 and the wafer stage 10 are arranged.
Is filled with an inert gas such as nitrogen or helium gas, whereby a narrow optical path between the lens Lr and the wafer 8 is replaced with the inert gas. However, since mechanically movable members (such as the mask stage 6 and the wafer stage 10) are arranged in these optical paths, it is unavoidable that the degree of gas cleanness is reduced by moving these members. In addition,
It is preferable that the robot arm for exchanging the mask and the robot arm for exchanging the wafer be housed in a casing separate from the casings C2 and C3 in order to improve the optical path cleanliness. Still, the degree of cleanliness of the gas inside the projection optical system 7 tends to be lower. As described above, the portion where the exposure light passes through the gas with low cleanliness in the optical path from the light source 1 to the wafer 8 is located in the narrow optical path between the illumination optical system 3 and the mask 4 and the mask 4 and the parallel flat plate P1. And in the narrow optical path between the lens Lr and the wafer 8.

As described above, the field of view (illumination area) on the mask 4 and the projection area (exposure area) on the wafer 8 defined by the projection optical system 7 have a rectangular shape having short sides along the X direction. It is. Therefore, the mask 4 and the wafer 8 are formed by using a drive system and interferometers (12, 14).
By performing the position control described above, the mask stage 6 and the wafer stage 10 and, consequently, the mask 4 and the wafer 8 are synchronously scanned along the short side direction of the rectangular exposure region and the illumination region, that is, in the X direction. The mask pattern is scanned and exposed on the wafer 8 in a region having a width equal to the long side of the exposure region and a length corresponding to the scanning amount of the wafer 8. As described above, in the third and fourth embodiments, the mask surface and the wafer surface are set in parallel, and the scanning direction is set to be horizontal.

[Third Embodiment] FIG. 13 is a view showing the lens arrangement of a projection optical system according to a third embodiment, in which the optical axis AX1 of the catadioptric optical system A and the optical axis AX2 of the refractive optical system B are shown. FIG. 4 is a cross-sectional view taken along a plane including: In the third embodiment, the present invention is applied to a projection optical system in which various aberrations including chromatic aberration are corrected for exposure light having a center wavelength of 157.6 nm and a full width at half maximum of 2 pm.

The projection optical system shown in FIG.
It is the same type as the optical system disclosed in Japanese Patent Publication No. 95. That is, in the projection optical system of the third embodiment, a plane reflecting mirror whose reflection surface forms an angle of 45 degrees with the optical axis AX1 of the catadioptric optical system A at a position where the light flux becomes narrow in the vicinity of the intermediate image forming position. M2 is arranged. Also, the catadioptric optical system A
Optical system B having an optical axis AX2 parallel to the optical axis AX1
Plane reflection having an angle of 45 degrees with respect to the optical axis AX2 of the refraction optical system B and having a reflection surface orthogonal to the reflection surface of the plane reflection mirror M2 in order to optically connect the light and the catadioptric optical system A. Mirror M3 is arranged.

Therefore, in the case of the projection optical system of the third embodiment, all the lenses constituting the catadioptric optical system A and the parallel plane plate P1 arranged near the mask R (corresponding to reference numeral 4 in FIG. 12). The component and the concave reflecting mirror M1 have the optical axis A
All the lens components constituting the refractive optical system B are arranged on the optical axis AX2 parallel to the optical axis AX1. When the mask 4 and the wafer 8 are horizontally supported as shown in FIG. 12, all the lens components constituting the projection optical system 7 are also horizontally supported, so that the lens components are not easily affected by gravity. There is an advantage that. In addition, since the catadioptric optical system A and the refractive optical system B are arranged along the two parallel optical axes AX1 and AX2, there is an advantage that the length of the lens barrel does not become too long.

The projection optical system according to the third embodiment has a parallel plane plate P1 arranged close to the mask R, and the light from the mask R transmitted through the parallel plane plate P1 is reflected by the catadioptric optical system A. Incident on. The catadioptric optical system A includes, in order from the incident side of light from the mask R, a biconcave lens L1, a biconvex lens L2, and a negative meniscus lens L3 having a concave surface facing the incident side.
And a concave reflecting mirror M1 having a concave surface facing the incident side. Therefore, the light from the mask R enters the catadioptric optical system A after passing through the plane-parallel plate P1.
The light incident on the catadioptric optical system A has three lens components L
The light enters the concave reflecting mirror M1 via 1 to L3. The light reflected by the concave reflecting mirror M1 forms an intermediate image of the mask pattern near the plane reflecting mirror M2 via two lens components L3 and L2.

Light from the intermediate image of the mask pattern enters the refracting optical system B via the plane reflecting mirror M2 and the plane reflecting mirror M3. The refractive optical system B includes, in order from the incident side of light from the intermediate image, a positive meniscus lens L4 having a convex surface facing the incident side, a biconvex lens L5, a positive meniscus lens L6 having a convex surface facing the incident side, and an incident side. A positive meniscus lens L7 having a convex surface facing the positive side, a positive meniscus lens L8 having a convex surface facing the incident side, and a biconvex lens L9.
The positive meniscus lens L6 and the positive meniscus lens L
An aperture stop S is disposed in the optical path between the aperture stop S and the aperture stop S.
Therefore, from the intermediate image of the mask pattern, the refractive optical system B
Incident on the wafer W form a reduced image of the mask pattern in an exposure area on the wafer W (corresponding to reference numeral 8 in FIG. 12) via the lens components L4 to L9.

Table 3 below summarizes data values of the projection optical system of the third embodiment. In Table (3), λ represents the center wavelength of the exposure light, FWHM represents the full width at half maximum of the exposure light, β represents the projection magnification, and NA represents the image-side numerical aperture. The surface number indicates the order of the surface from the mask side along the direction in which the light beam travels from the mask surface, which is the object surface, to the wafer surface, which is the image surface. Is the radius of curvature of the apex), d is the on-axis interval of each surface, that is, the surface interval, and n is the refractive index for the center wavelength.

It is assumed that the sign of the surface distance d changes each time it is reflected. Therefore, the sign of the surface distance d is negative in the optical path from the concave reflecting mirror M1 to the plane reflecting mirror M2, negative in the optical path from the plane reflecting mirror M3 to the wafer surface, and positive in the other optical paths. And
In the optical path where the surface distance d is positive, the radius of curvature of the convex surface toward the light incident side is positive, and the radius of curvature of the concave surface is negative. Conversely, in the optical path where the surface distance d is negative, the radius of curvature of the concave surface toward the light incident side is positive,
The radius of curvature of the convex surface is negative.

[0073]

[Table 3] (Main specifications) λ = 157.6 nm FWHM: 2 pm β = 1/4 NA = 0.65 (optical member specifications) Surface number r dn (mask surface) 20.000000 1 ∞ 10.000000 1.5600000 (P1) 2 ∞ 21.056466 3 * -410.25845 19.200000 1.5600000 (L1) 4 7622.04648 97.814420 5 442.05840 38.000000 1.5600000 (L2) 6 * -460.79557 637.333293 7 * -181.36058 24.000000 1.5600000 (L3) 8 -2202.35929 34.559790 9 -295.90336 -34.559 2202.35929 -24.000000 1.5600000 (L3) 11 * -181.36058 -637.333293 12 * -460.79557 -38.000000 1.5600000 (L2) 13 442.05840 -8.600000 14 ∞ 410.000000 (M2) 15 ∞ -107.846514 (M3) 16 * -271.59461 -40.000000 1.5600000 (L4) 17 -294.15246 -221.080055 18 -736.15276 -50.000000 1.5600000 (L5) 19 * 534.11318 -63.960648 20 -178.13615 -46.000000 1.5600000 (L6) 21 * -558.07630 -31.709633 22 ∞ -107.125647 (S) 23 -124.45291 -40.000000 1.5600000 ( L7) 24 * -701.01490 -2.857325 25 -187.95248 -35.000000 1.5600000 (L8) 26 -535.34602 -0.651637 27 -195.99609 -46.806762 1.5600000 (L9) 28 * 7665.52661 -6.232089 ( wafer surface) (Aspherical Data) r kappa C ₄ 3 Surface -410.25845 0.00000 -0.464328 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.289652 × 10 ^-12 0.876 203 × 10 ^-17 -0.101393 × 10 ^-21 r κ C ₄ 6 surface -460.79557 0.00000 0.655550 × 10 ^-8 12 surface C ₆ C ₈ C ₁₀ 0.750 690 × 10 ^-13 -0.375816 × 10 ^-18 -0.275978 × 10 ^-23 r κ C ₄ 7 side -181.36058 0.00000 0.947631 × 10 ^-8 11 side C ₆ C ₈ C ₁₀ 0.247890 × 10 ^-12 0.374299 × 10 ^-17 0.263940 × 10 ^-21 r κ C ₄ 16-271.59461 0.00000 0.427427 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.411417 × 10 ^-13 0.204209 × 10 ^-18 -0.710805 × 10 ^-23 r κ C ₄ 19 534.11318 0.00000 0.564196 × 10 ^-8 C ₆ C ₈ C ₁₀ -0.362399 × 10 ^-15 -0.263491 × 10 ^-17 0.420225 × 10 ^-22 r κ C ₄ 21-plane -558.07630 0.00000 -0.314496 × 10 ^-7 C ₆ C ₈ C ₁₀ 0.185759 × 10 ^-13 -0.161021 × 10 ^-17 -0.415 783 × 10 ^-21 r κ C ₄ 24 face -701.01490 0.00000 -0.337626 × 10 ^-7 C ₆ C ₈ C ₁₀ 0.160965 × 10 ^-12 -0.735 123 × 10 ^-17 0.441992 × 10 ^-21 r κ C ₄ 28 face 7665.52661 0.00000 -0.152895 × 10 ^-6 C ₆ C ₈ C ₁₀ -0.665509 × 10 ^-10 0.938735 × 10 ^-13 -0.520573 × 10 ^-16

FIG. 14 shows the spherical aberration in the third embodiment,
It is a figure showing astigmatism and distortion. FIG.
FIG. 9 is a diagram showing lateral aberration (meridional coma) in the third example. In each aberration diagram, NA is the image-side numerical aperture, Y is the image height, and the solid line is the center wavelength of 157.6 nm.
, The broken line indicates 157.6 nm + 1.3 pm, and the dashed line indicates 157.6 nm-1.3 pm, respectively. In the aberration diagrams showing astigmatism, S indicates a sagittal image plane, and M indicates a meridional image plane. As is clear from the aberration diagrams, in the third embodiment, the center wavelength is 1
It can be seen that various aberrations including chromatic aberration are satisfactorily corrected for the exposure light having a full width at half maximum of 27.6 nm at 57.6 nm.

[Fourth Embodiment] FIG. 16 is a view showing the lens arrangement of a projection optical system according to a fourth embodiment. FIG. 4 is a cross-sectional view taken along a plane including: In the fourth embodiment, the present invention is applied to a projection optical system in which various aberrations including chromatic aberration are corrected for exposure light having a center wavelength of 157.6 nm and a full width at half maximum of 10 pm.

The projection optical system of the fourth embodiment has a configuration similar to that of the third embodiment. However, while the full width at half maximum of the exposure light is 2 pm in the third embodiment, the full width at half maximum of the exposure light is 10 pm in the fourth embodiment, and in the third embodiment, the refractive optical system B has six lens components. In contrast to the above, in the fourth embodiment, 7
The difference is that it has two lens components. Hereinafter, the fourth embodiment will be described focusing on the differences from the third embodiment.

The projection optical system according to the fourth embodiment includes a parallel plane plate P1 disposed close to the mask R, and the light from the mask R transmitted through the parallel plane plate P1 is reflected by the catadioptric optical system A. Incident on. The catadioptric optical system A includes, in order from the incident side of light from the mask R, a biconcave lens L1, a biconvex lens L2, and a negative meniscus lens L3 having a concave surface facing the incident side.
And a concave reflecting mirror M1 having a concave surface facing the incident side. Therefore, the light from the mask R enters the catadioptric optical system A after passing through the plane-parallel plate P1.
The light incident on the catadioptric optical system A has three lens components L
The light enters the concave reflecting mirror M1 via 1 to L3. The light reflected by the concave reflecting mirror M1 forms an intermediate image of the mask pattern near the plane reflecting mirror M2 via two lens components L3 and L2.

The light from the intermediate image of the mask pattern enters the refracting optical system B via the plane reflecting mirror M2 and the plane reflecting mirror M3. The refractive optical system B includes, in order from the incident side of light from the intermediate image, a positive meniscus lens L4 having a convex surface facing the incident side, a biconvex lens L5, a positive meniscus lens L6 having a convex surface facing the incident side, and an incident side. A positive meniscus lens L7 having a convex surface facing the positive side, a positive meniscus lens L8 having a convex surface facing the incident side, a positive meniscus lens L9 having a convex surface facing the incident side, and a biconvex lens L10. The positive meniscus lens L6 and the positive meniscus lens L7
An aperture stop S is arranged in the optical path between the aperture stop S. Therefore, the light incident on the refractive optical system B from the intermediate image of the mask pattern forms a reduced image of the mask pattern in the exposure area on the wafer W via the lens components L4 to L10.

Table 4 below summarizes the data values of the projection optical system of the fourth embodiment. In Table (4), λ represents the central wavelength of the exposure light, FWHM represents the full width at half maximum of the exposure light, β represents the projection magnification, and NA represents the image-side numerical aperture. The surface number indicates the order of the surface from the mask side along the direction in which the light beam travels from the mask surface, which is the object surface, to the wafer surface, which is the image surface. Is the radius of curvature of the apex), d is the on-axis interval of each surface, that is, the surface interval, and n is the refractive index for the center wavelength.

It is assumed that the sign of the surface distance d changes each time it is reflected. Therefore, the sign of the surface distance d is negative in the optical path from the concave reflecting mirror M1 to the plane reflecting mirror M2, negative in the optical path from the plane reflecting mirror M3 to the wafer surface, and positive in the other optical paths. And
In the optical path where the surface distance d is positive, the radius of curvature of the convex surface toward the light incident side is positive, and the radius of curvature of the concave surface is negative. Conversely, in the optical path where the surface distance d is negative, the radius of curvature of the concave surface toward the light incident side is positive,
The radius of curvature of the convex surface is negative.

[0081]

(Main specifications) λ = 157.6 nm FWHM: 10 pm β = 1/4 NA = 0.65 (optical member specifications) Surface number r dn (mask surface) 20.000000 1 ∞ 10.000000 1.5600000 (P1) 2 ∞ 18.000000 3 * -372.48390 19.200000 1.5600000 (L1) 4 2824.40505 107.691386 5 441.56209 38.000000 1.5600000 (L2) 6 * -467.54839 632.035292 7 * -181.16467 24.000000 1.5600000 (L3) 8 -2171.42735 34.435069 9 -295.94748 -34.469 2171.42736 -24.000000 1.5600000 (L3) 11 * -181.16467 -632.035292 12 * -467.54839 -38.000000 1.5600000 (L2) 13 441.56209 -8.600000 14 ∞ 410.000000 (M2) 15 ∞ -96.164001 (M3) 16 * -248.89382 -40.000000 1.5600000 (L4) 17 -270.80367 -211.283468 18 -1633.27164 -50.000000 1.5600000 (L5) 19 * 439.76407 -84.131385 20 -187.72487 -42.000000 1.5600000 (L6) 21 * -508.63497 -38.738249 22 ∞ -19.402019 (S) 23 -312.42160 -30.000000 1.5600000 (L7) 24 -545.38881 -68.496963 25 -133.13377 -40.000000 1.5600000 (L8) 26 * -678.53406 -2.925194 27 -186.00220 -35.000000 1.5
600000 (L9) 28 -305.28790 -0.100000 29 -145.48941 -46.223734 1.5600000 (L10) 30 * 4767.12784 -6.000000 (Wafer surface) (Aspherical surface data) r κ C ₄ 3 surface -372.48390 0.00000 -0.540343 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.256808 × 10 ^-12 0.290465 × 10 ^-17 -0.427034 × 10 ^-22 r κ C ₄ 6 face -467.54839 0.00000 0.622527 × 10 ^-8 12 face C ₆ C ₈ C ₁₀ 0.649449 × 10 ^-13 -0.506658 × 10 ^-18 0.357490 × 10 ^-24 r κ C ₄ 7-181.16467 0.00000 0.943076 × 10 ^-8 11-side C ₆ C ₈ C ₁₀ 0.256514 × 10 ^-12 0.303718 × 10 ^-17 0.242059 × 10 ^-21 r κ C ₄ 16-side -248.89382 0.00000 0.609993 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.765145 × 10 ^-13 0.840211 × 10 ^-18 0.133482 × 10 ^-22 r κ C ₄ 19 side 439.76407 0.00000 0.481334 × 10 ^-8 C ₆ C ₈ C ₁₀ 0.266 384 × ^{10 -13 -0.149214 × 10 -17 0.265666 ×} 10 -22 r κ C 4 21 faces _{^{-508.63497 0.00000 -0.270625 × 10 -7 C 6}} C 8 C 10 -0.130088 × 10 -12 0.121888 × 10 -18 -0.449102 × 10 ^-21 r κ C ₄ 26-face -678.53406 0.00000 -0.463518 × 10 ^-8 C ₆ C ₈ C ₁₀ -0.381221 × 10 ^-12 0.150702 × 10 ^-16 -0.489031 × 10 ^-21 r κ C ₄ 30 4767.12784 0.00000 -0.195812 × 10 ^-6 C ₆ C ₈ C ₁₀ 0.241786 × 10 ^-10 -0.201056 × 10 ^-13 0.142658 × 10 ^-16

FIG. 17 shows the spherical aberration in the fourth embodiment,
It is a figure showing astigmatism and distortion. FIG.
FIG. 14 is a diagram showing lateral aberration (meridional coma) in the fourth example. In each aberration diagram, NA is the image-side numerical aperture, Y is the image height, and the solid line is the center wavelength of 157.6 nm.
, The dashed line indicates 157.6 nm + 8.6 pm, and the dashed line indicates 157.6 nm-8.6 pm. In the aberration diagrams showing astigmatism, S indicates a sagittal image plane, and M indicates a meridional image plane. As is clear from the aberration diagrams, in the fourth embodiment, the center wavelength is 1
It can be seen that various aberrations including chromatic aberration are satisfactorily corrected for exposure light having a full width at half maximum of 10 pm at 57.6 nm.

As described above, in the projection exposure apparatus according to each of the above-described embodiments, the catadioptric light whose chromatic aberration is well corrected for the exposure light having the center wavelength of 180 nm or less and the full width at half maximum of 20 pm or less. Since the projection optical system of this type is provided, it is possible to use an F ₂ laser with a relatively simple band narrowing as an exposure light source. With this configuration, a large exposure power can be obtained and the maintenance cost of the laser light source can be reduced, so that a projection exposure apparatus with low cost for the laser light source and high productivity can be realized.

As described above, in the case of the F ₂ laser, it is considered that the bandwidth can be narrowed down to a full width at half maximum of about ₂ pm. As shown in the above-described first and third embodiments, when the F ₂ laser having a full width at half maximum of about ₂ pm is used, and in the second and fourth embodiments using an F ₂ laser having a full width at half maximum of about 10 pm It is possible to reduce the number of lens components constituting the projection optical system. Fluorite (ie, CaF ₂ crystal) used as a glass material is expensive,
At a short wavelength of 180 nm or less, the loss of light quantity on the lens surface is so large that it cannot be ignored. Therefore, the effect of reducing the number of lenses with respect to the transmission efficiency of the projection optical system is great.

In the projection optical systems of the first and second embodiments described above, except for the plane-parallel plate and the plane reflecting mirror for separating the optical path, which are arranged near the mask, all of the projection optical systems are constituted. The lens component and the concave reflecting mirror are arranged along a common optical axis. As a result, all the lens components and the concave reflecting mirror can be incorporated into one lens barrel, so that the catadioptric optical system can be easily assembled and adjusted. In the projection optical systems according to the third and fourth embodiments, except for the plane reflecting mirror for separating the optical path, all the lens components and the concave reflecting mirror constituting the projection optical system are parallel to each other. They are arranged along an axis. As a result, a part of the lens components and the concave reflecting mirror are incorporated into the first lens barrel, and the remaining lens components are incorporated into the second lens barrel arranged in parallel with the first lens barrel. Can be. Thus, assembling and adjustment can be independently performed in each of the two lens barrels, and the mutual positional relationship between the two lens barrels is also simplified, so that the assembly and adjustment of the optical system is relatively easy. Can be done.

Further, in each of the above-described embodiments, since the exposure area is rectangular (slit shape), it is more convenient in the design and manufacture of the illumination optical system than an apparatus in which the exposure area is annular. Can be simplified. Further, in each of the above-described embodiments, by disposing the parallel plane plate close to the mask, the narrow optical path between the mask and the parallel plane plate and the narrow optical path between the wafer and the optical member close thereto are reduced. Except for the above, almost the entire optical path from the mask to the wafer can be filled with an inert gas such as helium gas having high cleanliness. As a result, even if short-wavelength light such as F ₂ laser light is used as exposure light, light absorption can be effectively avoided, and the transmission efficiency of the projection optical system can be improved. The use of the plane-parallel plate improves the durability and maintainability of the projection optical system, and makes it possible to correct the residual aberration after assembling the projection optical system.

The projection exposure apparatus according to each of the above embodiments can be manufactured by the following method. First, an illumination optical system for illuminating a pattern on a mask with illumination light having a center wavelength shorter than 180 nm is prepared. Specifically, the center wavelength is prepared an illumination optical system for illuminating the mask pattern by using a F ₂ laser light 157.6 nm. At this time, the illumination optical system is configured to supply illumination light having a spectrum width within a full width at half maximum of 20 pm. Note that a device that supplies illumination light having a spectrum width within a full width at half maximum of 2 pm may be applied. Next, a projection optical system for forming an image of the pattern on the mask on the photosensitive surface on the photosensitive substrate is prepared. Preparing the projection optics
This includes preparing a plurality of refractive optical elements and assembling the plurality of refractive optical elements. Then, by connecting these illumination optical system and projection optical system electrically, mechanically or optically so as to achieve the above-described functions, the projection exposure apparatus according to each embodiment can be manufactured.

[0088] Further, in the above embodiments, and the projection optical system in refractive optical element, the use of the CaF ₂ (calcium fluoride) as the material of this optical member, 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, if it is possible to sufficiently narrow the band of the illumination light for illuminating the mask, it is preferable that the projection optical system be made of a single type of optical material. 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 .

In each of the above embodiments, the optical path from the light source to the wafer is replaced with helium gas, but a part or all of the optical path may be replaced with nitrogen (N ₂ ) gas. Further, in each of the above-described embodiments, an F ₂ laser is used as a light source and the spectrum width is narrowed by a band narrowing device. Instead, a solid-state laser such as a YAG laser having an oscillation spectrum at 157 nm is used. Higher harmonics 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.

For example, assuming that the oscillation wavelength of the single-wavelength laser light is in the range of 1.51 to 1.59 μm, a tenth harmonic whose output wavelength is in the range of 151 to 159 nm is output. In particular, when the oscillation wavelength is in the range of 1.57 to 1.58 μm, a 10th harmonic having a generation wavelength in the range of 157 to 158 nm, that is, ultraviolet light having substantially the same wavelength as the F ₂ laser light can be obtained. Further, the oscillation wavelength is set to 1.03 to
When the wavelength is within the range of 1.12 μm, the generated wavelength is 147 to 1
A 7th harmonic within a range of 60 nm is output. In particular, if the oscillation wavelength is within a range of 1.099 to 1.106 μm, a 7th harmonic whose generation wavelength is within a range of 157 to 158 μm, that is, an F ₂ laser Ultraviolet light having substantially the same wavelength as light is obtained. Note that, as the single-wavelength oscillation laser, 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 spectral width (for example, about 0.01 pm).
It can be used in place of the light source 1 in each of the above embodiments. Now, according to the present invention, after a mask pattern image is collectively transferred to one shot area on a wafer, the wafer is successively and two-dimensionally moved in a plane orthogonal to the optical axis of the projection optical system so that the next shot A step-and-repeat method (batch exposure method) for repeating a process of collectively transferring a mask pattern image to an area, or a projection magnification β for exposing a mask and a wafer to a projection optical system when exposing each shot area of the wafer.
Can be applied to both a step-and-scan method (scanning exposure method) in which synchronous scanning is performed 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. Areas can be exposed.

In each of the embodiments described above, the reduction projection optical system is used. However, the projection optical system is not limited to the reduction system, but is not limited to the same magnification system or the enlargement system (for example, an exposure apparatus for manufacturing a liquid crystal display). May be used. Further, 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, which transfers 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. It is to be noted that the present invention is not limited to the above-described embodiment, but can take various configurations without departing from the gist of the present invention.

[0093]

As described above, according to the present invention,
Chromatic aberration with a small configuration of lenses with respect to short wavelength light such as F ₂ laser light can be realized a projection exposure apparatus having a satisfactorily corrected catadioptric projection optical system.
In other words, a relatively simple narrow-band F ₂ laser can be used as the exposure light source, and a large exposure power can be obtained. Further, since the maintenance cost of the laser light source is reduced, it is possible to realize a projection exposure apparatus having a low cost for the laser light source and high productivity.

Further, according to the present invention, by arranging a light transmitting optical member such as a plane-parallel plate close to the mask, a narrow optical path between the mask and the plane-parallel plate and the wafer and the optical path close to the wafer Substantially all of the optical path from the mask to the wafer, except for the narrow optical path between the members, can be filled with a highly clean gas such as helium gas, which hardly absorbs exposure light. As a result, even if short-wavelength light such as F ₂ laser light is used as exposure light, light absorption can be effectively avoided, and the transmission efficiency of the projection optical system can be improved. Further, by using the parallel plane plate, durability and maintainability of the projection optical system can be improved, and residual aberration can be corrected after assembling the projection optical system.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram schematically illustrating a basic configuration of a projection optical system of a projection exposure apparatus according to the present invention.

FIG. 2 is a view showing a region that can be used for image formation, that is, a usable region FR, and an exposure region ER that is actually used for exposure on the surface of a wafer W in the present invention.

FIG. 3 is a diagram schematically showing an overall configuration of a projection exposure apparatus according to a first embodiment and a second embodiment of the present invention.

FIG. 4 is a diagram showing a lens configuration of a projection optical system according to the first example, which includes an optical axis connecting the concave reflecting mirror M2 and a wafer surface (image surface) and is perpendicular to a mask surface (object surface). It is sectional drawing along a plane.

5 is a view corresponding to FIG. 4, and is a cross-sectional view along a plane that includes an optical axis connecting the concave reflecting mirror M2 and a wafer surface (image surface) and that is parallel to a mask surface.

FIG. 6 is a diagram illustrating spherical aberration, astigmatism, and distortion in the first example.

FIG. 7 is a diagram showing lateral aberration (meridional coma) in the first example.

FIG. 8 is a diagram illustrating a lens configuration of a projection optical system according to a second example, which includes an optical axis connecting the concave reflecting mirror M2 and a wafer surface (image surface) and is perpendicular to a mask surface (object surface). It is sectional drawing along a plane.

FIG. 9 is a view corresponding to FIG. 8, and is a cross-sectional view along a plane parallel to the mask surface, including the optical axis connecting the concave reflecting mirror M2 and the wafer surface (image surface).

FIG. 10 is a diagram showing spherical aberration, astigmatism, and distortion in the second example.

FIG. 11 is a diagram showing lateral aberration (meridional coma) in the second example.

FIG. 12 is a view schematically showing an overall configuration of a projection exposure apparatus according to a third embodiment and a fourth embodiment of the present invention.

FIG. 13 is a diagram illustrating a lens configuration of a projection optical system according to a third example, and is a cross-sectional view along a plane including an optical axis AX1 of the catadioptric optical system A and an optical axis AX2 of the refractive optical system B. It is.

FIG. 14 is a diagram illustrating spherical aberration, astigmatism, and distortion in the third example.

FIG. 15 is a diagram illustrating lateral aberration (meridional coma) in the third example.

FIG. 16 is a diagram illustrating a lens configuration of a projection optical system according to a fourth example, and is a cross-sectional view taken along a plane including an optical axis AX1 of the catadioptric optical system A and an optical axis AX2 of the refractive optical system B. It is.

FIG. 17 is a diagram illustrating spherical aberration, astigmatism, and distortion in the fourth example.

FIG. 18 is a diagram showing lateral aberration (meridional coma) in the fourth example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Mirror 3 Illumination optical system 4, R mask 5 Mask holder 6 Mask stage 7 Projection optical system 8, W wafer 9 Wafer holder 10 Wafer stage 11, 13 Moving mirror 12, 14 Interferometer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 515B F-term (Reference) 2H087 KA21 PA09 PA10 PA14 PA15 PA17 PB09 PB10 PB14 PB15 PB16 QA02 QA03 QA06 QA07 QA12 QA17 QA19 QA21 QA22 QA25 QA26 QA34 QA39 QA41 QA42 QA45 QA46 RA05 RA12 RA13 TA03 TA04 TA05 5F046 AA22 BA04 CA03 CA04 CA07 CB03 CB12 CB25

Claims (8)

[Claims] 1. An illumination optical system for illuminating a mask on which a pattern is formed, and a catadioptric projection optical system for forming an image of the pattern on a photosensitive substrate based on light from the mask. Wherein the illumination optical system is configured to supply illumination light having a central wavelength of 180 nm or less and a full width at half maximum of 20 pm or less, wherein the projection optical system includes a lens component and And a concave reflecting mirror, wherein the lens component and the concave reflecting mirror are positioned so as to substantially correct chromatic aberration of the projection optical system with respect to the illumination light. 2. An illumination optical system for illuminating a mask on which a pattern is formed, and a catadioptric projection optical system for forming an image of the pattern on a photosensitive substrate based on light from the mask. Wherein the illumination optical system is configured to supply illumination light having a central wavelength of 180 nm or less and a full width at half maximum of a predetermined value or less, and the projection optical system has a refractive power. An optical member having a light transmissive optical member disposed in close proximity to the mask for separating the optical member having the refractive power from an external atmosphere, and being parallel to an optical axis of the projection optical system. A projection exposure apparatus, wherein an interval between the mask and the light-transmitting optical member along a direction is set to 50 mm or less. 3. The projection exposure apparatus according to claim 2, wherein the full width at half maximum of the illumination light is 20 pm or less. 4. The projection optical system according to claim 1, wherein all the lens components and the concave reflecting mirror constituting the projection optical system are arranged along a common optical axis. Projection exposure equipment. 5. The projection optical system according to claim 1, wherein the projection optical system includes only one concave reflecting mirror, a plurality of lens components, and one or a plurality of flat reflecting mirrors.
The projection exposure apparatus according to any one of claims 1 to 4. 6. The projection exposure apparatus according to claim 1, wherein the full width at half maximum of the illumination light is 2 pm or less. 7. A projection optical system for forming a primary image of the pattern based on light from the mask.
An imaging optics, and a second for forming a secondary image of the pattern on the photosensitive substrate based on light from the primary image.
7. An imaging optical system, comprising:
The projection exposure apparatus according to claim 1. 8. When the maximum effective diameter of the lens of the first imaging optical system is h1 and the maximum effective diameter of the lens of the second imaging optical system is h2, 0.7 <h1 / h2 <1. The projection exposure apparatus according to claim 7, wherein the following condition is satisfied.