JPH08220432A - Projection optical system and exposure device provided with same - Google Patents

Abstract

PURPOSE: To independently enlarge and reduce an image on an objective surface in the longitudinal and lateral directions and to project the image employing only one set of cylindrical optical systems by making the image forming positions coincided in mutually orthogonal two directions within a second surface of the cylindrical optical systems. CONSTITUTION: When viewing the optical system along the longitudinal direction, a set of Galileo type cylindrical afocal systems is constituted of a pair of two cylindrical lenses 3a and 3b both having a generatrix along the lateral direction. Lenses 3a and 3b have negative and positive refractive powers, respectively, in the longitudinal direction. Moreover, on the objective surface Q1 side of the cylindrical afocal system, a first Kepler type afocal system is constituted of two spherical surface lenses 2a and 2b in a pair. Furthermore, on the image surface Q3 of the cylindrical afocal system, a second Kepler type afocal system is constituted of two spherical surface lenses 4a and 4b in a pair. The image forming positions in mutually orthogonal two direction within the second surface are made to concide by the cylindrical optical systems.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system and an exposure apparatus equipped with the optical system, and in particular, an image of an object plane is enlarged or reduced at different magnifications in the vertical and horizontal directions and projected on the image plane. Optical system for doing.

[0002]

2. Description of the Related Art Conventionally, as a projection optical system of this type, as shown in FIGS. 8A and 8B, there is known a projection optical system in which two sets of cylindrical afocal systems whose generating lines are orthogonal to each other are combined. Has been. Note that FIGS. 8A and 8B show the same optical system along two plane directions orthogonal to each other including the optical axis, that is, the vertical direction and the horizontal direction, respectively. As a projection optical system of this type, a relay system is often used before and after the cylindrical afocal system, and therefore, in FIGS. 8A and 8B, an object on the surface Q1 is re-formed on the surface R1. First relay system (22a, 2) that forms an image
2b) and a second relay system (24a, 24b) for re-imaging an object on the surface R2 on the surface Q3 are arranged.

As shown in FIG. 8 (a), when the optical system is viewed in the vertical direction, two cylindrical lenses 11 and 13 whose busbars are both in the horizontal direction form a pair, and a pair of Kepler-type lenses are formed. It constitutes a cylindrical afocal system. As described above, the first relay system (22a, 22b) and the second relay system (24a, 24b) are arranged before and after the cylindrical afocal system. Therefore, the light from the object plane Q1 is re-imaged on the plane R1 via the first relay system (22a, 22b).
The pair of Kepler-type cylindrical afocal systems (11, 13) conjugately couples the surfaces R1 and R2 with each other, expands the parallel light flux emitted from the surface R1 by about 3 times and is parallel to the surface R2. Is incident on. Furthermore, surface R2
The light from is re-imaged on the image plane Q3 via the second relay system (24a, 24b). As will be described later, the other two
The generatrixes of the two cylindrical lenses 12 and 14 are along the vertical direction and have no refractive power in the vertical direction. Therefore, the two cylindrical lenses 12 and 14 do not affect the refraction of light rays in the vertical direction.

On the other hand, as shown in FIG. 8 (b), when the optical system is viewed along the horizontal direction, the busbars are both aligned along the vertical direction.
The two cylindrical lenses 12 and 14 form a pair to form a pair of Kepler-type cylindrical afocal systems. Therefore, the light from the object plane Q1 is
The image is re-imaged on the surface R1 via the first relay system (22a, 22b). Then, the pair of Kepler-type cylindrical afocal systems (12, 14) connect the surfaces R1 and R2 to each other in a conjugate manner, and make the parallel light flux emitted from the surface R1 enter the surface R2 in parallel with substantially the same magnification. I am letting you. Further, the light from the surface R2 is re-imaged on the image surface Q3 via the second relay system (24a, 24b). As described above, the generatrixes of the other two cylindrical lenses 11 and 13 are along the lateral direction and have no refractive power in the lateral direction. Therefore, the two cylindrical lenses 11 and 13 do not affect the refraction of light rays in the lateral direction.

As described above, since the projection optical system shown in FIGS. 8A and 8B is constructed by combining two sets of cylindrical afocal systems whose generatrices are orthogonal to each other, the image of the object plane is vertically It is possible to project the image on the image plane by enlarging or reducing it in different magnifications in the direction and the lateral direction. It is also possible to prevent the generation of axial astigmatism by matching the vertical image forming position of the light from the object plane with the horizontal image forming position.

[0006]

As described above, in the conventional projection optical system as described above, the first cylindrical afocal system composed of at least two cylindrical lenses having the generatrix along the longitudinal direction, and the generatrix laterally. A second cylindrical afocal system including at least two cylindrical lenses along the direction. In other words, two sets of cylindrical afocal systems whose generatrix directions are orthogonal to each other are required. That is, in the conventional projection optical system, it is necessary to include at least four cylindrical lenses.

However, in general, it is more difficult to process the lens surface of a cylindrical lens than a spherical lens. Therefore, in order to reduce the cost of the optical system, it is desirable to reduce the number of cylindrical lenses as much as possible. Further, even at the time of adjustment, it is relatively easy to align the generatrix lines of the plurality of cylindrical lenses in the same direction, but it is difficult to adjust so that the generatrix lines of the plurality of cylindrical lenses are orthogonal to each other. Therefore, it is desirable that the generatrix directions of the cylindrical lenses in the optical system are all the same. The present invention has been made in view of the above problems, and it is possible to project an image of an object plane on the image plane by enlarging or reducing the image in the vertical and horizontal directions independently using only one set of cylindrical optical systems. The purpose is to provide an optical system.

[0008]

In order to solve the above-mentioned problems, in the present invention, the light flux from the first surface is condensed to form an image of the first surface on a predetermined second surface. A projection optical system for enlarging or reducing an image in at least one of two directions orthogonal to each other in the second surface relative to an image in the other direction, wherein the projection optical system comprises: A cylindrical optical system having a refractive power only in one of two mutually orthogonal directions, the cylindrical optical system having a refractive power in only one of the two mutually orthogonal directions; Optical means,
A second optical unit having a refractive power only in a direction having a refractive power of the first optical unit, and the cylindrical optical system matches image forming positions in two directions orthogonal to each other in the second plane. A projection optical system characterized by the above.

According to another aspect of the present invention, the above-mentioned projection optical system, light source means for supplying a light beam having a predetermined light beam diameter to the first surface of the projection optical system, and the projection optical system. A multi-light source forming means for forming a plurality of light source images based on a shaped light beam shaped into a predetermined light beam diameter on the second surface by a system, and light beams from the plurality of light source images are respectively condensed to form a projection original plate. A condenser optical system for illuminating
An exposure apparatus comprising: a projection exposure optical system for projecting an image of a pattern formed on the projection original onto a substrate.

[0010]

In the present invention, two directions orthogonal to each other on the image plane,
That is, a cylindrical optical system having two optical means having a refractive power in only one of the vertical direction and the horizontal direction is provided. The cylindrical optical system is configured so that the image forming positions in the two directions orthogonal to each other on the image plane coincide with each other. Thus, in the present invention, only one set of cylindrical optical system is used,
The image of the object plane can be projected vertically or horizontally independently in an enlarged or reduced manner. Furthermore, it is possible to keep the object plane and the image plane conjugate with each other in both the vertical direction and the horizontal direction, and prevent axial astigmatism from occurring.

More specifically, the projection optical system of the present invention comprises an afocal system composed of, for example, two spherical lenses and a cylindrical afocal system composed of, for example, two cylindrical lenses whose generatrices are both along the longitudinal direction. It is preferably provided. Thus, in the vertical direction, the parallel light beam from the object plane can be enlarged or reduced only by the afocal system, and in the horizontal direction, the parallel light beam from the object plane can be enlarged or reduced by the afocal system and the cylindrical afocal system. it can. In addition, the afocal system and the cylindrical afocal system are arranged along the optical axis so that the image forming positions of the light from the object plane through the afocal system and the cylindrical afocal system are aligned in the vertical direction and the horizontal direction. Relative positioning is preferred. In this way, the object plane and the image plane can be kept conjugate in both the vertical and horizontal directions.

Further, in the exposure apparatus of the present invention provided with the projection optical system of the present invention, the light source supplies a parallel light beam to the object plane of the projection optical system, and serves as a multi-light source forming means on the image plane of the projection optical system. The entrance surface of the fly-eye lens of is arranged. In this way, the parallel light flux from the light source can be shaped in accordance with the cross-sectional shape of the fly-eye lens while minimizing the light amount loss, using only one set of cylindrical optical systems. Further, since no axial astigmatism is generated on the incident surface of the fly-eye lens, the tolerance for the angular deviation of the light source becomes large. Further, since all the generatrix lines of the cylindrical lens are in the same direction, it is easy to adjust the generatrix directions.

[0013]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing the configuration of a projection optical system according to the first embodiment of the present invention, which includes a Galileo-type cylindrical afocal system. 1 (a) and (b)
Shows the same optical system along two plane directions orthogonal to each other including the optical axis, that is, in the vertical direction and the horizontal direction, respectively. The vertical direction and the horizontal direction are nothing but two directions orthogonal to each other on the image plane of the projection optical system. 3A and 3B are diagrams corresponding to FIGS. 1A and 1B and are enlarged views showing the optical paths of the cylindrical afocal system in the projection optical system of FIG.

As shown in FIG. 1 (a), when the optical system is viewed along the vertical direction, two cylindrical lenses 3a and 3b whose busbars are both along the horizontal direction form a pair, and the cylindrical optical system is More specifically, it constitutes a set of Galileo-type cylindrical afocal systems. Each of the cylindrical lenses 3a and 3b has a negative refractive power and a positive refractive power in the vertical direction. Two spherical lenses 2a and 2b form a pair on the object plane Q1 side of the cylindrical afocal system (3a, 3b) to form a first Kepler-type afocal system. Furthermore, a cylindrical afocal system (3a,
On the image plane Q3 side of 3b), two spherical lenses 4a and 4b form a pair to form a second Kepler-type afocal system.

Therefore, in the vertical direction, the object plane Q
The collimated light flux emitted from the beam No. 1 passes through the first Kepler-type afocal system (2a, 2b) to be enlarged or reduced, and then the Galileo-type cylindrical afocal system (3
a, 3b). Then, after passing through the second Keplerian afocal system (4a, 4b) to be enlarged or reduced, it reaches the image plane Q3 as a parallel light flux thicker than the parallel light flux emitted from the object plane Q1. That is,
In the vertical direction, the expansion or contraction of the parallel light flux emitted from the object plane Q1 is performed by the first Kepler-type afocal system (2a, 2b), the Galileo-type cylindrical afocal system (3a, 3b) and the second Kepler. Depends on the type afocal system (4a, 4b).

On the other hand, in the lateral direction, the Galileo type cylindrical afocal system (3a, 3b) has no power (refractive power). Therefore, the luminous flux is not expanded by the Galileo-type cylindrical afocal system (3a, 3b). That is, in the lateral direction, the object plane Q1
The expansion or contraction of the parallel light flux emitted from the laser beam depends only on the first Keplerian afocal system (2a, 2b) and the second Keplerian afocal system (4a, 4b).

Next, pay attention to the conjugate relationship with the object plane Q1. As shown in FIGS. 1B and 3B, in the lateral direction, the light emitted from the center point of the object plane Q1 is the first Kepler-type afocal system (2) which is the re-imaging optical system.
a, 2b) to focus the image on the surface Q21. The light condensed to form an image on the surface Q21 is refracted by the Galileo-type cylindrical afocal system (3a, 3b). However, since the Galileo-type cylindrical afocal system (3a, 3b) has no power in the lateral direction, it functions as a mere plane plate.

That is, the light which has passed through the Galileo type cylindrical afocal system (3a, 3b) is slightly displaced from the surface Q21 to the image surface Q3 side in accordance with the total axial thickness of the cylindrical lenses 3a and 3b. Then, a virtual image of the surface Q1 is formed. At this time, face Q21 and face Q
A real image of the surface Q1 is formed at a position of the surface Q24 between the surface 22 and 22. After that, the second Kepler-type afocal system (4a, 4b), which is a re-imaging optical system, relays the virtual image formed on the surface Q22 and forms an image on the image surface Q3.

On the other hand, as shown in FIGS. 1 (a) and 3 (a), in the vertical direction, the light is focused by the first Kepler-type afocal system (2a, 2b) so as to form an image on the surface Q21. The light passes through the Galileo-type cylindrical afocal system (3a, 3b) and forms a virtual image of the surface Q1 on the surface Q22. At this time, a real image of the surface Q1 is formed at the position of the surface Q23 on the image surface 3 side of the surface Q22. After that, the second Keplerian afocal system (4a, 4b) relays the virtual image formed on the surface Q22 and forms an image on the image surface Q3. In the projection optical system of the first example, the position of the surface Q22 in the vertical direction shown in FIG. 3A is configured to match the position of the surface Q22 in the horizontal direction shown in FIG. 3B. There is. The conditions for the position of the surface Q22 to match in the vertical and horizontal directions will be described later.

As described above, in the projection optical system of the first embodiment, the virtual image of the conjugate plane Q21 of the object plane Q1 by the first Kepler-type afocal system (2a, 2b) is changed to the Galileo-type cylindrical afocal system (3a). 3b) is formed on the surface Q22. However, since the position of the surface Q22 is the same in the vertical direction in which the Galileo-type cylindrical afocal system (3a, 3b) has power and in the horizontal direction in which it does not have power, the Galileo-type cylindrical afocal system (3a, 3b) causes On-axis astigmatism is not generated. The virtual image formed on the surface Q22 is relayed by the second Kepler-type afocal system (4a, 4b), and the Galileo-type cylindrical afocal system (3a,
The image is formed on the image plane Q3 at different magnifications in the vertical and horizontal directions according to the magnification of 3b).

Next, the conditions for matching the position of the surface Q22 in the vertical and horizontal directions will be described with reference to FIGS. 3 (a) and 3 (b). As shown in FIG. 3 (b),
In the lateral direction, the cylindrical afocal system (3
a, 3b) merely function as plane-parallel plates. In this case, the conjugate plane Q21 of the object plane Q1 by the first Kepler-type afocal system (2a, 2b) and the virtual image plane Q2 of the plane Q21 by the cylindrical afocal system (3a, 3b).
The distance D from 2 is represented by the following equation (1).

D = (n1-1) t1 / n1 + (n2-1) t2 / n2 (1) Where, n1: refractive index of the cylindrical lens 3a n2: refractive index of the cylindrical lens 3b t1: axis of the cylindrical lens 3a Upper thickness t2: On-axis thickness of the cylindrical lens 3b

As shown in equation (1), the surface Q21 and the surface Q2
The distance D from 2 is defined only by the refractive indices and axial thicknesses of the two cylindrical lenses 3a and 3b, and does not depend on the positions of the cylindrical lenses 3a and 3b on the optical axis. On the other hand, the position of the surface Q21 on the optical axis is
The first Kepler-type afocal system (2a, 3a, 3b) does not depend on the cylindrical afocal system (3a, 3b).
Since it depends only on 2b), it matches in the vertical and horizontal directions. Therefore, in order for the position of the virtual image plane Q22 to match in the vertical and horizontal directions, the conjugate plane Q21 of the object plane Q1 and
Cylindrical afocal system (3a,
3b) so that the distance D ′ between the surface Q21 and the virtual image surface Q22 coincides with the distance D defined by the above equation (1).
It suffices to arrange the three cylindrical lenses 3a and 3b.

By the way, in the vertical direction shown in FIG. 3A, the principal point spacing between the two cylindrical lenses 3a and 3b (the rear side of the cylindrical lens 3a (the image plane side) and the front side of 3b (the object plane side) ) Distance to the main plane) d is
It is expressed by the following equation (2). d = f1 + f2 (2) Here, f1: focal length of the cylindrical lens 3a f2: focal length of the cylindrical lens 3b

The distance from the front main plane of the cylindrical lens 3a to the surface Q21 is x1, and the distance from the rear main plane of the cylindrical lens 3a to the surface Q23 is x.
If 1d, the relationship shown in the following equation (3) is established from Newton's formula. 1 / f1 =-(1 / x1) + (1 / x1d) (3) Note that the signs of the distances x1 and x1d in the formula (3) are:
The direction from the object plane side to the image plane side along the optical axis is positive.
In addition, in the following description, the signs of other distances also have a positive direction from the object plane side to the image plane side along the optical axis.

Further, assuming that the distance from the front main plane of the cylindrical lens 3b to the surface Q23 is x2, and the distance from the rear main plane of the cylindrical lens 3b to the surface Q22 is x2d, the following equation is obtained from Newton's formula: The relationship shown in 4) is established. 1 / f2 =-(1 / x2) + (1 / x2d) (4) Further, the relationship shown in the following expression (5) is established between the distance x1d, the distance x2, and the principal point interval d. d = x1d-x2 (5)

If the distance between the front main plane and the rear main plane of the cylindrical lens 3a is p1 and the distance between the front main plane and the rear main plane of the cylindrical lens 3b is p2, the surfaces Q21 and Q22 in the vertical direction. In order that the distance D ′ between the two and the distance D between the surfaces Q21 and Q22 in the horizontal direction match, the following expression (6) must be satisfied. d + p1 + p2 = x1-x2d + D (6)

From the above equations (2) to (6), the distance x1
Is obtained by the following equation (7).

## EQU00001 ## x1 = f1 {-D.f1 + (f1 + f2) ² + f1 (p1 + p2)} / {(f1-f2) (f1 + f2)} (7)

By arranging the cylindrical afocal system (3a, 3b) so as to satisfy the above formula (7), the first Kepler-type afocal system (2a, 2b) for the light from the object plane Q1 is arranged. And the position of the image plane Q22 by the cylindrical afocal system (3a, 3b) are
As a result, the position of the image plane Q3 of the entire projection optical system matches in the vertical and horizontal directions. That is, the image of the object plane Q1 is vertically and horizontally independent by the projection optical system including one set of Galileo type cylindrical afocal system (3a, 3b) and two sets of Keplerian type afocal system (2a, 2b: 4a, 4b). It is possible to prevent the occurrence of axial astigmatism by enlarging or reducing the image plane Q3 at a magnification of 1, and projecting onto the image plane Q3, and keeping the object plane Q1 and the image plane Q3 conjugate in both the vertical and horizontal directions. it can.

Next, in the specific numerical example of the first embodiment, the position of the cylindrical afocal system (3a, 3b) satisfying the condition for preventing the axial astigmatism from occurring will be determined. The following table (1) shows the specifications of the cylindrical afocal system (3a, 3b) in the numerical example. In Table (1), r1 is the radius of curvature of the surface on the object surface side, and r1
Reference numeral 2 denotes the radius of curvature of the image-side surface, t denotes the axial thickness, and n denotes the refractive index.

[0031]

Table 1 r1 r2 t n Lens 3a-60 ∞ 1.6 1.6 1.6 Lens 3b ∞ -120 4.8 1.6

Based on the specifications shown in Table (1), the focal length f
1, focal length f2, principal point distance d, distances p1 and p2
Has the following value. f1 = -100 f2 = 200 d = 100 p1 = 0.6 p2 = 1.8

As described above, in the lateral direction shown in FIG. 3B, the cylindrical afocal system (3a, 3) is used.
Since b) has no power, it acts just as a plane-parallel plate. Therefore, according to the equation (1), the distance between the surface Q21 and the surface Q22 in the lateral direction is D = 2.4. On the other hand, by substituting the values of f1, f2, D, p1 and p2 described above into the equation (7), the distance x1 = + 33.3333 can be obtained.

Therefore, the first Kepler-type afocal system (2a, 2b) is arranged so that the conjugate plane Q21 of the object plane Q1 is located at a position 33.3333 on the image plane side from the front principal plane of the cylindrical lens 3a. By relatively positioning the cylindrical afocal system (3a, 3b), an image of the object plane Q1 (virtual image in this embodiment) is formed at the same position on the optical axis (position of the surface Q22). By projecting the image formed on the surface Q22 onto the image surface Q3 by the second Kepler-type afocal system (4a, 4b), the images of the object plane Q1 finally differ from each other in the vertical direction and the horizontal direction. Formed at magnification. Furthermore, since the conjugate of the object plane Q1 and the image plane Q3 is maintained in both the vertical direction and the horizontal direction, axial astigmatism does not occur.

The above formulas (1) to (7) are applicable not only to the Galileo type cylindrical afocal system, but also to the Kepler type cylindrical afocal system. FIG. 4 is a diagram schematically showing the configuration of a projection optical system according to the second embodiment of the present invention including a Kepler-type cylindrical afocal system. 4A and 4B show the same optical system along two plane directions orthogonal to each other including the optical axis, that is, the vertical direction and the horizontal direction. 5 is a view corresponding to FIG. 4A and is an enlarged view showing the optical path of the Kepler-type cylindrical afocal system in the projection optical system of FIG.

As shown in FIG. 4 (a), when the optical system is viewed along the vertical direction, two cylindrical lenses 11a and 11b whose busbars are both along the horizontal direction form a pair,
It constitutes a pair of Kepler-type cylindrical afocal systems. Each of the cylindrical lenses 11a and 11b has a positive refracting power in the vertical direction.
In addition, a cylindrical afocal system (11a, 11
Two spherical lenses 12a and 12b form a pair on the image plane Q5 side in b) to form a Kepler-type afocal system.

Therefore, in the vertical direction, the object plane Q
The parallel light flux emitted from the reference numeral 4 is expanded or reduced by the Kepler-type cylindrical afocal system (11a, 11b), and the Kepler-type afocal system (12a, 12b).
After passing through b) and being enlarged or reduced, it reaches the image plane Q5. That is, in the vertical direction, the expansion or contraction of the parallel light flux emitted from the object plane Q4 depends on the Keplerian cylindrical afocal system (11a, 11b) and the Keplerian afocal system (12a, 12b).

On the other hand, as shown in FIG. 4B, the Kepler-type cylindrical afocal system (11a, 11b) has no power in the lateral direction. Therefore, the Kepler-type cylindrical afocal system (11a, 11
No expansion or reduction of the luminous flux is carried out according to b). That is, in the lateral direction, the expansion or contraction of the parallel light flux emitted from the object plane Q4 depends only on the Keplerian afocal system (12a, 12b).

Next, based on the above equations (1) to (7), in the specific numerical example of the second embodiment, a cylindrical afocal system satisfying the condition for preventing axial astigmatism from occurring. Find the position of (11a, 11b).
Cylindrical afocal system (11
The specifications of a, 11b) are shown in the following table (2). In Table (2), r1 represents the radius of curvature of the object-side surface, r2 represents the radius of curvature of the image-side surface, t represents the axial thickness, and n represents the refractive index.

[0040]

Table 2 r1 r2 t n Lens 11a 60 ∞ 1.6 1.6 1.6 Lens 11b ∞ −120 4.8 1.6

Based on the specifications shown in Table (2), the focal length f
1, focal length f2, principal point distance d, distances p1 and p2
Has the following value. f1 = 100 f2 = 200 d = 300 p1 = 0.6 p2 = 1.8

As described above, in the lateral direction shown in FIG. 4 (b), the cylindrical afocal system (11a, 1a) is used.
Since 1b) has no power, it acts just as a plane-parallel plate. Therefore, according to equation (1), D = 2.4
Becomes On the other hand, the above-mentioned f1, f2, D, p1 and p2
Substituting the value of into equation (7), the distance x1 = -300.0
Can be obtained.

Therefore, the cylindrical lens 11a
It can be seen that the object plane or the conjugate plane of the object plane may be located on the surface Q4 of 300.0 from the front main plane of the above to the object plane side. In the case of the second embodiment, the surface Q4 on which the object plane or the conjugate plane of the object plane should be located is on the left side of the figure with respect to the cylindrical afocal system (11a, 11b). Therefore, the relay lens system for forming the conjugate plane of the object plane, such as the first Kepler-type afocal system (2a, 2b) in the first embodiment, is omitted, and the object plane is Q4.
It can be placed directly on the surface.

Thus, by the cylindrical afocal system (11a, 11b), the conjugate plane Q4 'of the object plane Q4 is obtained.
Is formed at a position of +2.4 from the object plane Q4. Then, the image formed on the conjugate plane Q4 'is relayed by the Kepler-type afocal system (12a, 12b), and the same position in the vertical direction and the horizontal direction, that is, the image plane Q5.
Projected on. That is, the image of the object plane Q4 is magnified vertically and horizontally by a projection optical system including a pair of Keplerian cylindrical afocal systems (11a, 11b) and a pair of Keplerian afocal systems (12a, 12b). Alternatively, the image is reduced and projected onto the image plane Q5, and the object plane Q4 and the image plane Q5 are projected both vertically and horizontally.
It is possible to prevent the occurrence of axial astigmatism by keeping and conjugate.

FIG. 6 is a schematic view showing the arrangement of a projection optical system according to the third embodiment of the present invention which includes a Galileo type cylindrical afocal zoom system. Note that FIG.
(A) and (b) show the same optical system along two plane directions orthogonal to each other including the optical axis, that is, the vertical direction and the horizontal direction. FIG. 7 is a view corresponding to FIG. 6A and is an enlarged view showing the optical path of the Galileo-type cylindrical afocal zoom system in the projection optical system of FIG.

As shown in FIG. 6 (a), when the optical system is viewed in the vertical direction, three cylindrical lenses 23, 24, and 25 having their generatrixes in the horizontal direction are the three groups of Galileo type cylindrical lenses. It constitutes an afocal zoom system. In addition, each cylindrical lens 23, 24
And 25 have a positive refractive power, a negative refractive power, and a positive refractive power in the longitudinal direction, respectively. Also, the object plane Q6 of the cylindrical afocal zoom system (23 to 25)
On the side, two spherical lenses 21 and 22 are paired to form a Kepler-type afocal system.

Therefore, in the vertical direction, the object plane Q
The parallel light flux emitted from 6 passes through the Kepler-type afocal system (21, 22) and is expanded or reduced. Then, the cylindrical afocal zoom system (23-2
After being enlarged or reduced by 5), the image plane Q7 'is reached. That is, in the vertical direction, the expansion or contraction of the parallel light flux emitted from the object plane Q6 depends on the Keplerian afocal system (21, 22) and the cylindrical afocal zoom system (23 to 25).

On the other hand, in the lateral direction, the cylindrical afocal zoom system (23 to 25) has no power. Therefore, the luminous flux is not expanded or contracted by the cylindrical afocal zoom system (23 to 25). That is, in the lateral direction, the expansion or contraction of the parallel light flux emitted from the object plane Q6 depends only on the Keplerian afocal system (21, 22).

In the case of the three-group cylindrical afocal zoom system (23 to 25) as shown in FIG. 7, the mathematical expression for obtaining the condition for preventing the axial astigmatism from occurring is the above-mentioned two-group structure. It is more complicated than the cylindrical afocal system. However, it goes without saying that it is theoretically possible to obtain the conditions for preventing the axial astigmatism from occurring by calculation.

By the way, in the case of obtaining the condition for actually causing no axial astigmatism in the cylindrical afocal zoom system (23 to 25), the image point position is calculated by paraxial calculation while changing the object point distance. There is also a method of calculating and finding by trial and error a lens arrangement in which the distance from the object point to the image point in the vertical direction matches the distance D from the object point to the image point in the horizontal direction.

In FIG. 7, an image of the conjugate plane Q7 of the object plane Q6 is formed on the plane Q7 '. And
The distance between the surfaces Q7 and Q7 'matches the distance D from the object point to the image point in the lateral direction shown in FIG. 6 (b). Thus, as shown in FIGS. 6 (a), (b) and FIG.
The Kepler-type afocal system (21, 22) forms an image of the object surface Q6 on the surface Q7, and the light from the image formed on the surface Q7 is converted into a cylindrical afocal zoom system (23 to 2).
It is possible to form an image on the image plane Q7 'both vertically and horizontally by relaying by 5). In other words, the object plane Q6 and the image plane Q7 'can be kept conjugate in both the vertical direction and the horizontal direction, and the axial astigmatism can be prevented from occurring.

In the case of a zoom system, the distance between the object surface (or its conjugate surface) and the cylindrical lens 23 that does not cause axial astigmatism changes with zooming (magnification). In this case, by moving the cylindrical afocal zoom system (23 to 25) integrally along the optical axis with zooming, the fluctuation of the virtual image plane Q7 due to zooming is corrected, and the axial astigmatism is reduced. Occurrence can be prevented.

FIG. 2 is a schematic view showing the arrangement of an exposure apparatus according to the fourth embodiment of the present invention which comprises the projection optical system of the present invention. The illustrated exposure apparatus has an object plane Q1 of the projection optical system.
A light source 1 for supplying a parallel light flux is provided. The parallel light flux emitted from the light source 1 (excimer laser or the like) includes a first Keplerian afocal system (2a, 2b), a cylindrical afocal system (3a, 3b), and a second Keplerian afocal system (4a). 4b), it is shaped into a parallel light beam having a predetermined cross-sectional shape through the projection optical system (beam shaping optical system). The shaped parallel light flux is reflected downward in the figure by the mirror M, and then guided to the incident surface of the fly-eye lens 6 which is a multi-light source forming unit positioned on the image plane Q3 of the projection optical system.

The light incident on the fly-eye lens 6 is two-dimensionally divided by a plurality of lens elements forming the fly-eye lens 6, and a plurality of secondary light sources are formed near the exit surface thereof. Light from a plurality of secondary light sources is condensed by a condenser lens 7 and illuminates a mask (projection original plate) 8 on which a pattern is formed in a superimposed manner. In this way, an extremely uniform illuminance distribution is formed on the mask 8.
The light transmitted through the mask 8 reaches the wafer surface 10 which is the substrate positioned on the image plane of the light through the projection lens 9.
In this way, the pattern formed on the mask 8 is transferred onto the wafer surface 10 by the projection lens 9.

Here, when the light source 1 is a light source that emits a rectangular luminous flux such as an excimer laser, when the light is guided to the fly-eye lens 6 having a substantially square cross-sectional shape, the rectangular shape from the light source 1 is used. It is necessary to shape the beam of light into a substantially square shape by the projection optical system. Further, in order to increase the tolerance for the angular deviation of the light source 1 itself, the light source 1
The exit surface Q1 (i.e., the object surface of the projection optical system) and the entrance surface Q3 of the fly-eye lens 6 (i.e., the image surface of the projection optical system) must be optically conjugate.

As already mentioned in the description of the first embodiment,
First Kepler-type afocal system (2a, 2b), cylindrical afocal system (3a, 3b), and second
When the projection optical system including the Kepler-type afocal system (4a, 4b) is used, the shape of the light flux is shaped from a rectangular shape to a substantially square shape, and the exit surface Q1 of the light source 1 and the entrance surface Q3 of the fly-eye lens 6 are formed. It can be kept conjugate in both the vertical and horizontal directions. Therefore, in the exposure apparatus according to the fourth embodiment, the light quantity loss is small and the tolerance for the angular deviation of the light source is large.

Even if the cross-sectional shape of the fly-eye lens 6 is not square but has a different aspect ratio, the cross-sectional shape of the fly-eye lens 6 can be changed by changing the magnification of the cylindrical afocal system (3a, 3b). It can be shaped accordingly. Further, in the above-mentioned fourth embodiment, an example in which the projection optical system according to the first embodiment is applied to the exposure apparatus is shown, but the projection optical system according to another aspect of the present invention can be applied to the exposure apparatus. It is clear that there is.

Furthermore, in each of the above-mentioned embodiments, the cylindrical optical system is an afocal optical system. However, the cylindrical optical system does not necessarily have to be an afocal optical system in order to achieve the effects of the present invention. In each of the above-described embodiments, the re-imaging optical system (relay optical system) arranged on at least one of the object side and the image plane side of the cylindrical optical system is an afocal optical system. Shows. However, the re-imaging optical system does not necessarily have to be an afocal optical system in order to achieve the effects of the present invention.

Furthermore, in each of the above-described embodiments, the projection optical system is shown as an overall afocal optical system. However, the projection optical system does not necessarily have to be an afocal optical system in order to achieve the effects of the present invention.

[0060]

As described above, in the projection optical system of the present invention, only one set of cylindrical optical system is used,
The image of the object plane can be projected on the image plane by enlarging or reducing the image vertically and horizontally independently. That is, unlike the conventional technique, it is not necessary to provide two sets of cylindrical afocal systems whose busbars are orthogonal to each other, so that the cost can be reduced. Further, since all the generatrix lines of the cylindrical lens are in the same direction, it is easy to adjust the generatrix directions. Further, in the exposure apparatus of the present invention provided with the projection optical system of the present invention, the light flux from the light source can be shaped according to the cross-sectional shape of the fly-eye lens, and the axial astigmatism at the incident surface of the fly-eye lens No aberration occurs. Therefore, it is possible to realize an exposure apparatus that has a small loss of light amount and a large tolerance for an angular deviation of a light source.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a projection optical system including a Galileo type cylindrical afocal system according to a first embodiment of the present invention.

FIG. 2 is a view schematically showing the arrangement of an exposure apparatus according to the fourth embodiment of the present invention, which is equipped with the projection optical system of the present invention.

3 is a view corresponding to FIG. 1 and is an enlarged view showing an optical path of a cylindrical afocal system in the projection optical system of FIG.

FIG. 4 is a diagram schematically showing a configuration of a projection optical system according to a second embodiment of the present invention including a Kepler-type cylindrical afocal system.

5 is a view corresponding to FIG. 4A and is an enlarged view showing an optical path of a Kepler-type cylindrical afocal system in the projection optical system of FIG. 4;

FIG. 6 is a diagram schematically showing the configuration of a projection optical system including a Galileo-type cylindrical afocal zoom system according to a third example of the present invention.

FIG. 7 is a view corresponding to FIG. 6A and is an enlarged view showing an optical path of a Galileo-type cylindrical afocal zoom system in the projection optical system of FIG. 6;

FIG. 8 is a diagram schematically showing a configuration of a conventional projection optical system.

[Explanation of symbols]

 1 Light source 2a, 2b Kepler-type afocal system 3a, 3b Galileo-type cylindrical afocal system 4a, 4b Kepler-type afocal system 6 Fly-eye lens 7 Condenser lens 8 Mask 9 Projection lens 10 Wafer Q1 Object surface Q3 Image plane M Mirror

Claims (7)

[Claims] 1. A light beam from the first surface is condensed to form a predetermined second light beam.
Forming an image of the first surface on a surface, and enlarging or reducing an image in at least one of the two directions in the second surface which are orthogonal to each other relative to the image in the other direction. In the projection optical system, the projection optical system has a cylindrical optical system having a refractive power only in one of the two directions orthogonal to each other, and the cylindrical optical system is arranged in two directions orthogonal to each other. A first optical unit having a refractive power only in one of the directions, and a second optical unit having a refractive power only in the direction having the refractive power of the first optical unit; A projection optical system characterized in that image forming positions in two directions orthogonal to each other in two planes are made to coincide with each other. 2. The re-imaging system, wherein the projection optical system is arranged in an optical path between the first surface and the cylindrical optical system, and collects a light beam from the first surface to form an intermediate image. The projection optical system according to claim 1, further comprising an optical system, wherein the intermediate image is re-imaged on the second surface by the cylindrical optical system. 3. The projection optical system is disposed in an optical path between the cylindrical optical system and the second surface, and an image of the first surface formed by the cylindrical optical system on the second surface. The projection optical system according to claim 1, further comprising a re-imaging optical system for re-imaging to. 4. The first optical system, wherein the projection optical system is arranged in an optical path between the first surface and the cylindrical optical system, and collects light from the first surface to form an intermediate image. An image of the intermediate image, which is arranged in the optical path between the imaging optical system and the cylindrical optical system and the second surface and is re-imaged by the cylindrical optical system, is further re-formed on the second surface. The projection optical system according to claim 1, further comprising a second re-imaging optical system that forms an image. 5. The cylindrical optical system is composed of an afocal optical system for converting a parallel light beam incident on the optical system into a parallel light beam having a predetermined light beam diameter, and the first optical means and the second optical means are provided. The projection optical system according to any one of claims 1 to 4, wherein the projection optical system is formed of a cylindrical lens. 6. The projection optical system is composed of an afocal optical system that converts a parallel light flux from the first surface into a parallel light flux having a predetermined light flux diameter and guides it to the second surface. The projection optical system according to any one of claims 1 to 5. 7. The projection optical system according to claim 1, a light source means for supplying a light beam having a predetermined light beam diameter to the first surface of the projection optical system, and the projection. Multi-light source forming means for forming a plurality of light source images based on a shaped light flux shaped into a predetermined light flux diameter on the second surface by an optical system, and light fluxes from the plurality of light source images are condensed and projected. An exposure apparatus comprising: a condenser optical system that illuminates an original in a superimposed manner; and a projection exposure optical system that projects and exposes an image of a pattern formed on the projection original onto a substrate.