TWI437267B - A projection optical system, an exposure apparatus, and a device manufacturing method - Google Patents

Description

Projection optical system, exposure apparatus and device manufacturing method

The present invention relates to a projection optical system, an exposure apparatus, and a device manufacturing method.

Devices such as semiconductor devices or flat panel displays (FPDs) are manufactured through photolithography. The photolithography project includes an exposure project that projects a pattern of a master, called a mask or a reticle, onto a substrate such as a glass plate or wafer coated with a sensitizer called photolithography. The substrate is exposed. In the manufacture of FPD, an exposure apparatus having a projection optical system including a mirror is generally used. When the substrate is exposed by using such an exposure device, a multi-dimensional development is performed on the substrate, or expansion or contraction occurs due to the use of the original plate a plurality of times, and a magnification error occurs.

A projection optical system that exposes an exposed object of a large screen such as a glass substrate is disclosed in Japanese Laid-Open Patent Publication No. Hei 8-306618. Japanese Patent Publication No. Hei 8-306618 discloses a projection optical system having a first plane mirror, a concave mirror, a convex mirror, a concave mirror, and a second plane mirror in order from the object surface side, and the object plane and the first plane. A parallel flat plate is disposed between the mirrors and between the second planar mirror and the image plane. However, in Japanese Laid-Open Patent Publication No. Hei 8-306618, the parallel flat plate is described as "optical thin body". A projection optical system is formed as shown in the drawings in Japanese Laid-Open Patent Publication No. Hei 8-306618, in which a so-called double telecentric optical system is formed in which light rays are passed from the object plane through the upper parallel plate and through the lower parallel plate to the image plane. The chief rays in the light are parallel. Moreover, since a magnification error is generated in each exposure process, a detection system that detects a magnification error in a specific pattern is disclosed; and the parallel plate is bent in a direction orthogonal to the scanning direction according to the detection result. And the mechanism that produces linear magnification changes.

In general, when a magnification error is generated, it is often enlarged or reduced in both the scanning direction and its orthogonal direction. In such a case, when the same magnification change occurs in the scanning direction and the orthogonal direction, the magnification change is hereinafter referred to as "isotropic magnification change". As an optical system capable of generating such an isotropic magnification change, an optical system in which a plano-convex lens and a plano-concave lens are combined is disclosed in Japanese Laid-Open Patent Publication No. Sho 62-35620. That is, for a plano-convex lens and a plano-concave lens having substantially equal radii of curvature, the convex surface and the concave surface are placed in parallel with each other with a slight air gap therebetween, and are disposed at positions where the parallel flat plates are placed in the aforementioned projection optical system. At this time, the isotropic magnification change can be generated by slightly increasing or decreasing the interval between the convex surface and the concave surface. Further, even when a magnification change of about 10 ppm is generated by this method, astigmatism hardly occurs.

However, it is known that if a curved parallel flat plate is disposed in the optical path of the projection optical system, the magnification can be corrected, but astigmatism is newly generated. For example, in the case where the lower parallel flat plate is used for the magnification correction in the scanning direction, the upper surface convex portion and the lower surface are curved in the scanning direction for the magnification, and the holding plane is provided in the orthogonal direction. The deformation of the state. At this time, although the refractive power in the direction orthogonal to the scanning direction does not change, a negative refractive power is generated in the scanning direction. Therefore, the imaging position of the line image in the scanning direction (hereinafter referred to as the V line) is imaged farther from the optical system than the line image (hereinafter referred to as the H line) in the orthogonal direction of the scanning as it is, that is, the lower side image. According to the calculation by the inventors, when 10 ppm (in the case of 1.00001 times) is amplified in the scanning direction, the astigmatism of the HV line is about 5 μm (H line is below). In the case where the upper parallel plate is used for the magnification correction in the direction orthogonal to the scanning direction, in the case where the upper parallel plate is used for magnification correction in the scanning direction, it is positive in the scanning direction, as described in Japanese Laid-Open Patent Publication No. Hei 8-306618. In the direction of intersection, a curvature that is recessed upward is imparted. At this time, if the object side is viewed from the imaging system side, the refractive power in the scanning direction does not change, but a positive refractive power is generated in a direction orthogonal to the scanning direction, and a magnification is generated in a direction orthogonal to the scanning direction. The line is reduced and the V line is imaged on the side closer to the imaging system than the H line. If the ray tracing is re-imaged from the object side to the image side in this direction, the magnification which is the lateral aberration is reversed, and the magnification in the direction orthogonal to the scanning direction is enlarged, and the longitudinal direction is enlarged. The imaging position of the aberration is preserved, and the H line is imaged at a position farther from the optical system than the V line, that is, the lower side image. In short, if the magnification in the direction orthogonal to the scanning direction is enlarged by the upper parallel plate, the astigmatism of the H line is generated. Similarly, if the magnification of the scanning direction is amplified by the lower parallel plate, H is generated. The astigmatism of the line below.

Although it is not described in Japanese Laid-Open Patent Publication No. Hei 8-306618, it is conceivable that the bending directions caused by the mechanism for generating the magnification are orthogonal at the two parallel flat plates, and for example, the upper parallel plate is used for scanning. The magnification correction in the direction in which the directions are orthogonal, and the lower parallel plate is used for the magnification correction in the scanning direction. In this way, the magnification error can be more precisely aligned in both directions, so that high-precision pattern position alignment can be achieved. However, it has been found that if two parallel flat plates are used to simultaneously increase the scanning direction and the magnification in the orthogonal direction, it is known that the astigmatism of the two is mutually reinforcing. Further, in the case where the two parallel plates are used to reduce the magnification in both directions, although the direction in which the astigmatism is generated is reversed, the astigmatism generated by the upper and lower parallel plates is also enhanced. Conversely, when the scanning direction is enlarged in one of the directions orthogonal to the scanning direction and the other direction is reduced, the direction in which the astigmatism is generated is reversed, and the astigmatism is eliminated.

On the other hand, the optical system capable of generating the change in the isotropic magnification described in Japanese Laid-Open Patent Publication No. Sho 62-35620 can only correct the magnification in an isotropic manner. However, the magnification change that actually occurs and is expected to be corrected is not uniform in the scanning direction and the direction orthogonal to the scanning direction. Therefore, the method of correcting the magnification using the optical system cannot be put to practical use.

An object of the present invention is to provide a projection optical system capable of suppressing generation of astigmatism and independently correcting magnification in two directions orthogonal to each other.

The present invention relates to a projection optical system in which a first plane mirror, a first concave mirror, a convex mirror, a second concave mirror, and a second plane mirror are arranged in this order from the object surface side on the optical path from the object plane to the image plane, and the object plane and The optical path between the first plane mirrors is parallel to the optical path between the second plane mirror and the image plane, and the projection optical system includes a first optical system disposed on an optical path between the object plane and the first plane mirror. Correcting the magnification of the projection optical system in the second direction orthogonal to the first direction of the optical path; and the second optical system is disposed on the optical path between the second planar mirror and the image plane, and correcting the first a magnification of the projection optical system in a third direction orthogonal to the second direction; and a third optical system disposed between the object surface and the optical path between the first planar mirror or the second planar mirror and the image plane The optical path between the second optical direction and the third direction corrects the magnification of the projection optical system at the same magnification; and a control unit in which the projection optical system is used The amount of correction for the magnification in the second direction and the third direction is A and B, respectively, and the correction amount of the third optical system to the magnification in the second direction and the third direction of the projection optical system is set. When C is set, the control unit controls the first optical system, the second optical system, and the third optical system such that the correction amount C is between the correction amount A and the correction amount B. The correction amount of the magnification in the second direction in the first optical system is (AC), and the correction amount of the magnification in the third direction in the second optical system is (BC).

Further features of the present invention will become apparent from the following description and claims.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(Example 1)

The exposure apparatus of the first embodiment will be described with reference to Fig. 1 . The exposure apparatus of the first embodiment includes an illumination system IL, a projection optical system PO, and a master drive mechanism (not shown) that scans a reticle (original) 9 disposed on the object plane OP of the projection optical system PO. And a substrate driving mechanism (not shown) that scans the substrate 19 disposed on the image plane IP of the projection optical system PO. The illumination system IL may include a light source LS, a first condensing lens 3, a fly-eye lens 4, a second condensing lens 5, a slit defining member 6, an imaging optical system 7, and a plane mirror 8. The light source LS may include a mercury lamp 1 and an elliptical mirror 2. The slit defining member 6 defines the illumination range of the original plate 9, that is, the cross-sectional shape of the slit-shaped light that illuminates the original plate 9. The imaging optical system 7 is configured to image the slit defined by the slit defining member 6 on the object surface. The plane mirror 8 bends the optical path in the illumination system IL. The projection optical system PO projects the pattern of the original plate 9 disposed on the object surface OP onto the substrate 19 disposed on the image plane IP, thereby exposing the substrate 19. The projection optical system PO can be configured as one of an equal magnification imaging optical system, an enlarged imaging optical system, and a reduced imaging optical system. However, the projection optical system PO is preferably configured as an equal-magnification optical system. On the object side and the image plane side, the chief ray is parallel, that is, both sides of the object plane and the image plane have double telecentricity.

The projection optical system PO has a first plane mirror 13 , a first concave mirror 14 , a convex mirror 15 , a second concave mirror 16 , and a second plane mirror 17 which are arranged in this order from the object surface side on the optical path from the object plane OP to the image plane IP. The optical path between the object plane OP and the first plane mirror 13 is parallel to the optical path between the second plane mirror 17 and the image plane IP. The plane including the mirror surface of the first plane mirror 13 and the plane including the mirror surface of the second plane mirror 17 are at an angle of 90 degrees to each other. The first plane mirror 13 and the second plane mirror 17 can be integrally formed. The first concave mirror 14 and the second concave mirror 16 can be integrally formed. The projection optical system PO has a parallel flat plate 10 disposed on the optical path between the object plane OP and the first plane mirror 13. The parallel flat plate 10 constitutes a first optical system, and the first optical system is corrected in a second direction (y direction) orthogonal to the first direction (Z direction) of the optical path between the object plane OP and the first plane mirror 13 . The magnification of the projection optical system. The projection optical system PO also has a parallel flat plate 18 disposed on the optical path between the second plane mirror 17 and the image plane. The parallel flat plate 18 constitutes a second optical system that corrects the magnification of the projection optical system in the third direction (x direction) orthogonal to the first direction (Z direction) and the second direction (y direction). The two parallel flat plates 10 and 18 have a mechanism (not shown) for bending the parallel flat plates 10 and 18, so that the parallel flat plate 10 can perform magnification correction in the y direction, and the parallel flat plate 18 can perform magnification correction in the x direction. The y direction may be a scanning direction, and the x direction may be a direction orthogonal to the scanning direction. The direction in which the two parallel plates 10, 18 are bent may be opposite to each other.

The projection optical system PO also has a plano-convex lens 11 and a flat concave lens 12 on the optical path between the object plane and the first plane mirror 13, and the plano-convex lens 11 and the plano-concave lens 12 separate the convex spherical surface having a substantially equal radius of curvature from the concave spherical surface 5~ The air gap of about 20 mm is opposed in parallel. The plano-convex lens 11 and the plano-concave lens 12 have a mechanism (not shown) that slightly changes the interval in the Z direction in the drawing, so that the isotropic magnification correction of the projection optical system can be performed. The plano-convex lens 11 and the plano-concave lens 12 constitute a third optical system that corrects the magnification of the projection optical system at the same magnification in the first direction and the second direction. The thickness and the interval of each of the plano-convex lens 11 and the plano-concave lens 12 are arbitrary as long as they do not cause self-weight deformation when held in a space and can constitute the space holding mechanism and the vertical drive mechanism. When the plano-convex lens 11 and the plano-concave lens 12 are synthetic quartz having a refractive index of 1.475, if the convex surface of the plano-convex lens 11 and the concave surface of the concave lens 12 have a radius of curvature of about 47,000 mm, and the plano-convex lens 11 is spaced from the plano-concave lens 12, When moving 1mm, the magnification can vary by about 10ppm. However, it is necessary to slightly change the radius of curvature of the convex surface of the plano-convex lens 11 and the concave surface of the concave lens 12 so that the size of the image of the plano-convex lens 11 and the plano-concave lens 12 which are placed at the reference height position is completely different from that of the two lenses. the same. The first optical system (parallel flat plate 10), the second optical system (parallel flat plate 18), and the third optical system (the plano-convex lens 11 and the plano-concave lens 12) are controlled by the control unit C. In addition, the convex and concave surfaces of the plano-convex lens 11 and the plano-concave lens 12 may be opposite to each other.

In the following, when the first and second optical systems that correct the magnification in one direction in the x and y directions are combined with the third optical system that is an isotropically corrected magnification to correct the magnification of the projection optical system PO, The reason why the astigmatism accompanying the magnification correction is 0 is obtained. Now, the correction amount of the magnification in the y direction and the x direction of the projection optical system is set to A (ppm) and B (ppm), respectively, and the third optical system that corrects the magnification isotropically corrected for the y direction and the x direction. The correction amount of the magnification on the upper side is set to C (ppm). When the correction amount C of the third optical system for the magnification in the y direction and the x direction is (A+B)/2, the correction amount of the magnification in the y direction by the first optical system 10 is {A-(A). +B)/2}=(AB)/2. The correction amount of the magnification in the x direction by the second optical system 18 is {B-(A+B)/2}=(B-A)/2. That is, the correction amounts of the magnifications of the first optical system 10 and the second optical system 18 are the result of positive and negative inversion. As previously mentioned, if the directions of enlargement and reduction of the two parallel plates 10, 18 are reversed, the astigmatism generated by the two parallel plates 10, 18 cancel each other out. Further, the third optical system in which the plano-convex lens 11 and the plano-concave lens 12 are combined with the isotropic correction magnification does not generate astigmatism. Therefore, the magnification of the projection optical system can be independently corrected in the y direction and the x direction (the scanning direction and its orthogonal direction) without generating astigmatism.

In the above example, the correction amount C of the magnification of the third optical system is (A+B)/2, and astigmatism does not occur. However, when the correction amount C of the magnification of the third optical system is the amount between the correction amount A in the y direction and the correction amount B in the x direction, a certain amount of astigmatism is generated, but generation of astigmatism can be suppressed. And independently control the magnification in the x and y directions. In this case, the correction amount (A-C) of the first optical system 10 and the correction amount (B-C) of the second optical system 18 are necessarily opposite to each other. Therefore, the astigmatism generated by the correction of the magnification by the first optical system 10 and the astigmatism due to the correction of the magnification by the second optical system 18 cancel each other, so that generation of astigmatism can be suppressed.

(Example 2)

The exposure apparatus of the second embodiment will be described with reference to Fig. 2 . Although the illumination system IL is omitted in FIG. 2, the second embodiment actually has the illumination system IL as in the first embodiment. In the first embodiment, the parallel flat plates 10 and 18 which are deformable in the first direction (Z direction) are used as the first optical system and the second optical system. In the second embodiment, as the first optical system and the second optical system, a cylindrical lens system having a plurality of cylindrical lenses and capable of changing the interval between the plurality of cylindrical lenses in the first direction is used. Further, in the first embodiment, as the third optical system, an optical system having the plano-convex lens 11 and the plano-concave lens 12 and capable of changing the interval between the plano-convex lens 11 and the plano-concave lens 12 in the first direction (Z direction) is used. In the second embodiment, as the third optical system, a plano-concave lens (or plano-convex lens) 12' having a concave spherical surface (or a convex spherical surface) and a plane and capable of being driven in the first direction (Z direction) is used.

In Embodiment 2, the magnification in the x direction or the y direction is corrected by changing the interval between the cylindrical lenses 21 and 22 (or 23 and 24). A cylindrical lens system that corrects the magnification in the x direction is composed of a cylindrical lens 21 and a cylindrical lens 22. The cylindrical lens 21 has a concave cylindrical surface whose upper surface is a flat surface and whose lower surface has a curvature in the x direction, and has an air gap of about 5 to 20 mm from the upper surface of the cylindrical lens 22. The upper surface of the cylindrical lens 22 is a convex cylindrical surface having a curvature in the x direction, and the lower surface is a convex spherical surface, and has a 5~ between the upper surface of the plano-concave lens 12' having a concave spherical surface on the upper surface and a flat surface on the lower surface. Air separation of 20mm. The magnification in the x direction is corrected with respect to the cylindrical lens 22 by driving (up and down moving) the cylindrical lens 21 in the Z direction. The magnification is corrected isotropically in the x direction and the y direction by driving (up and down) the plano-concave lens 12' in the Z direction.

In the second embodiment, in order to correct the magnification in the y direction as the scanning direction, a cylindrical lens system in which the cylindrical lens 23 and the cylindrical lens 24 are combined is used instead of the parallel flat plate. The cylindrical lens 23 has a flat surface on the upper surface, a concave cylindrical surface having a curvature in the scanning direction on the lower surface, and an air gap of about 5 to 20 mm from the upper surface of the cylindrical lens 24. The cylindrical lens 24 has a convex cylindrical surface having a curvature in the scanning direction on the upper surface, and has a flat surface on the lower surface. By moving the cylindrical lens 23 up and down, the magnification in the y direction can be corrected. The thickness and the interval of each of the cylindrical lenses 21, 22, 23, and 24 are arbitrary as long as they do not cause self-weight deformation when held in a space, and can constitute the space holding mechanism and the vertical drive mechanism. In the case where the cylinder is synthetic quartz having a refractive index of 1.475, if the radius of curvature is about 47,000 mm, the movement of 1 mm can change the magnification by about 10 ppm. However, it is necessary to slightly change the cylindrical surface and the spherical surface so that the size of the image of the three lenses that have passed through the reference height position is exactly the same as that of the three lenses. In addition, the convex and concave surfaces of the cylindrical surface and the convex and concave surfaces of the spherical surface may be opposite to each other.

In the second embodiment, since a lens group having a thickness thicker than that of the first embodiment is disposed in the optical path, axial chromatic aberration occurs. Therefore, in order to correct the axial chromatic aberration, the lens 15' is additionally disposed before the convex mirror 15. In order to correct the y direction as the scanning direction or the magnification in the x direction as the orthogonal direction, a bendable parallel plate is used in Embodiment 1, and a driveable cylindrical lens system is used in Embodiment 2. However, if the parallel flat plate and the cylindrical lens system are disposed apart on the object side and the image side, a parallel plate for correcting one of the magnification of the scanning direction and the magnification orthogonal to the scanning direction may be used and used for Correct the other cylindrical lens system for use in combination. In addition, although the examples of the equal-magnification imaging optical system are disclosed in the first embodiment and the second embodiment, it is apparent that the imaging magnification is evenly equal, as long as the object plane side and the image plane side become telecentric optical systems. The same effect can also be obtained. In addition, if it is not double telecentric, uneven coma aberration or the like is generated in the exposure region due to correction by the parallel plate or cylindrical lens system. However, in Embodiments 1 and 2, since the double telecentric optical system is used as the projection optical system, only a uniform spherical image is slightly generated in the exposure region by the correction of the parallel flat plate or the cylindrical lens system. difference.

The exposure apparatus of the present invention can be used in the manufacture of a semiconductor device or an FPD device. The device manufacturing method may include a process of exposing a substrate coated with a photosensitive agent using the above-described exposure device, and a process of developing a substrate on which the exposure is performed. Further, the above device manufacturing method may include other well-known processes (oxidation, film formation, vapor deposition, doping, planarization, etching, photolithographic stripping, dicing, bonding, encapsulation, etc.).

While the invention has been described with respect to the exemplary embodiments, it is understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be construed in the broadest scope and

1. . . Mercury lamp

2. . . Elliptical mirror

3. . . First concentrating lens

4. . . Compound eye lens

5. . . Second concentrating lens

6. . . Slit specification member

7. . . Imaging optics

8. . . Plane mirror

9. . . Buchhol

10. . . Parallel plate

11. . . Plano-convex lens

12. . . Flat concave lens

12’. . . Plano-concave lens

13. . . First plane mirror

14. . . First concave mirror

15. . . Convex mirror

15’. . . lens

16. . . 2nd concave mirror

17. . . 2nd plane mirror

18. . . Parallel plate

19. . . Substrate

twenty one. . . Cylindrical lens

twenty two. . . Cylindrical lens

twenty three. . . Cylindrical lens

twenty four. . . Cylindrical lens

C. . . Control department

OP. . . Object

IP. . . Image plane

PO. . . Projection optical system

LS. . . light source

IL. . . Lighting system

X. . . Third direction

Y. . . Second direction

Z. . . First direction

Fig. 1 is a view schematically showing the configuration of an exposure apparatus of a first embodiment.

Fig. 2 is a view schematically showing the configuration of an exposure apparatus of a second embodiment.

1. . . Mercury lamp

2. . . Elliptical mirror

3. . . First concentrating lens

4. . . Fly eye lens

5. . . Second concentrating lens

6. . . Gap specifying member

7. . . Imagery optical system

8. . . Plane mirror

9. . . Marking

10. . . Parallel plate

11. . . Plano-convex lens

12. . . Flat concave lens

13. . . First plane mirror

14. . . First concave mirror

15. . . Convex mirror

16. . . 2nd concave mirror

17. . . 2nd plane mirror

18. . . Parallel plate

19. . . Substrate

C. . . Control department

OP. . . Object surface

IP. . . Image plane

PO. . . Projection optics

LS. . . light source

IL. . . Lighting system

X. . . Third direction

Y. . . Second direction

Z. . . First direction

Claims (7)

A projection optical system in which a first mirror, a first concave mirror, a convex mirror, a second concave mirror, and a second mirror are disposed in order from the object surface to the image plane, the object surface and the first surface The optical path between the mirrors is parallel to the optical path between the second mirror and the image plane, and the projection optical system includes a first optical system and light disposed between the object surface and the first mirror Correcting the magnification of the projection optical system in the second direction orthogonal to the first direction of the optical path; and the second optical system is disposed on the optical path between the second mirror and the image plane, and correcting the above a magnification of the projection optical system in a third direction orthogonal to the first direction and the second direction; and a third optical system, an optical path disposed between the object surface and the first mirror, or the second mirror and the image The optical path between the surfaces corrects the magnification of the projection optical system at the same magnification in the second direction and the third direction; and the control unit sets the second direction and the third direction of the projection optical system Repair on the magnification When the third optical system sets the correction amount of the magnification in the second direction and the third direction of the projection optical system to C, the control unit controls the first optical system. In the second optical system and the third optical system, the correction amount C is an amount between the correction amount A and the correction amount B, and the first optical system is provided. The correction amount of the magnification in the second direction is (A-C), and the correction amount of the magnification in the third direction by the second optical system is (B-C). The projection optical system according to claim 1, wherein the object surface and the image surface have telecentricity. The projection optical system according to claim 1, wherein the first optical system and the second optical system include a parallel flat plate that can be bent in the first direction, and a plurality of cylindrical lenses that can be changed. a cylindrical lens system in which the plurality of cylindrical lenses are spaced apart in the first direction, at least one of the two; the third optical system includes a plano-convex lens and a flat concave lens and is capable of changing the aforementioned plano-convex lens and the aforementioned plano-concave lens The optical system of the interval in the first direction. The projection optical system according to claim 1, wherein the first optical system and the second optical system include a parallel flat plate that can be bent in the first direction, and a plurality of cylindrical lenses that can be changed. a cylindrical lens system in which the plurality of cylindrical lenses are spaced apart in the first direction, at least one of the two; the third optical system includes a plano-convex lens or a plano-concave lens and is capable of being driven in the first direction Lens. The projection optical system according to the first aspect of the invention, wherein the control unit controls the first optical system, the second optical system, and the third optical system such that the correction amount C is (A+B) /2, and the aforementioned first optical system is in the aforementioned second direction The correction amount of the magnification is (A - B) / 2, and the correction amount (B - A) / 2 of the magnification in the third direction by the second optical system is made. An exposure apparatus according to any one of claims 1 to 5, wherein a pattern of a mask disposed on the object surface is projected onto the image plane. The substrate is exposed to the substrate. A method for manufacturing a device, which is a method for manufacturing a semiconductor device or a flat panel display, comprising: a project of exposing a substrate using an exposure device as described in claim 6; and performing the foregoing exposure The substrate is developed by the project.