JP2000286178A - Projection optical system, aligner and manufacture of the projection optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a projection optical system wherein asymmetrical components of various aberrations are corrected. SOLUTION: After correcting symmetrical components of various aberrations of a projection optical system PL, random components (asymmetrical components) of the residual aberrations of the system PL are measured. An optical member, having a prescribed refracting power, is selected as a processed member 10 from among optical members constituting the system PL, and such a surface profile having uneven distribution to have the random components of the member 10 cancel out is calculated, based on the measured random components of the various aberrations of the system PL. A member 10 is removed from the system PL and processed, in such a manner that a processed surface 10a thereof will have the calculated uneven surface profile having uneven distribution. The processed member 10 is placed along the optical path of the system PL again.

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 for projecting an image of a pattern on a first object onto a second object, for example, a semiconductor integrated circuit, an image pickup device (such as a CCD), a liquid crystal display, or the like. The present invention is suitable for use in a projection optical system for an exposure apparatus used when a micro device such as a thin film magnetic head is manufactured using lithography technology.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device or the like, an image of a reticle pattern as a mask is projected through a projection optical system.
2. Description of the Related Art An exposure apparatus is used that transfers an image onto each shot area on a wafer (or a glass plate or the like) coated with a resist as a photosensitive substrate. Conventionally, a step-and-repeat type reduction projection type exposure apparatus (stepper) has been frequently used as an exposure apparatus. Recently, however, a step-and-repeat type exposure apparatus that performs synchronous scanning of a reticle and a wafer to perform exposure has been used.
Scanning exposure apparatuses have also attracted attention.

In recent years, with the miniaturization of integrated circuits, it has been required to improve the resolution of a projection optical system used in an exposure apparatus. The resolution of the projection optical system increases as the exposure wavelength used decreases and as the numerical aperture (NA) of the projection optical system increases. For this reason, the exposure wavelength used in the exposure apparatus is becoming shorter year by year, and the numerical aperture of the projection optical system is also increasing. The exposure wavelength that is currently mainstream is 248 nm of a KrF excimer laser, but the shorter wavelength ArF excimer laser is used.
An excimer laser of 193 nm is also being put to practical use. When these excimer laser beams are used for exposure, for example, synthetic quartz glass (SiO ₂ ) or fluorite (CaF ₂ ) is used as a glass material (optical material) for the projection optical system.

[0004] Further, since the resolution of the projection optical system is required to be improved, optical members used for the projection optical system are manufactured with the ultimate manufacturing accuracy. Further, when manufacturing the projection optical system by assembling the manufactured optical members, the intervals between the optical members are adjusted, and the optical members are tilted (rotated around the optical axis perpendicular direction) or shifted (optical axis). The manufacturing error is minimized by making very fine adjustments, such as moving along the vertical direction.

Further, among the various aberrations of the projection optical system, a component which is asymmetric with respect to the optical axis of the projection optical system, that is, a random component cannot be completely corrected even by performing the above-described assembly adjustment. As disclosed in U.S. Pat. No. 6,392,119, various aberrations of a projection optical system are actually measured, and a correction plate having a surface shape having a concavo-convex distribution for canceling these aberrations is manufactured. A way to add it has been proposed.

[0006] In addition to improving the resolution by increasing the NA, modified illumination in which light is obliquely incident by attaching a predetermined aperture stop (σ stop) is also effective in improving the resolution and the depth of focus. When using a super-resolution technique such as the modified illumination method, various aberrations of the projection optical system have a large effect,
The projection optical system is required to have as low aberration as possible. Further, JP-A-7-335516 and JP-A-10-1
As disclosed in Japanese Patent No. 42555, an exposure apparatus that corrects various aberrations caused by a change in exposure conditions such as a change in illumination conditions by arranging a plurality of optical characteristic correction members in a projection optical system is also proposed. Have been.

[0007]

As described above, in the conventional exposure apparatus, the random components of the various aberrations of the projection optical system may not be completely corrected even after the assembly adjustment. A correction plate having a surface shape having a concavo-convex distribution that cancels out the random component is manufactured, and the correction plate is added to the projection optical system to correct random components of various aberrations of the projection optical system.

However, the addition of a correction plate to the projection optical system is not preferable because it leads to an increase in the manufacturing cost of the projection optical system. In particular, when the projection optical system is mass-produced, the effect becomes large. When excimer laser light is used for exposure, synthetic quartz glass, fluorite, or the like is used as a glass material (optical material) for the projection optical system, such as g-line or i-line of a mercury lamp. Is much more expensive than the glass material used for exposure, and the increase in manufacturing cost due to the addition of a correction plate is further increased.

Further, it is expected that the numerical aperture (NA) of the projection optical system will be further increased in the future. When manufacturing a projection optical system having such a large numerical aperture, a correction plate is inserted on the reticle side. For this purpose, it is necessary to increase the area of the correction plate and increase the thickness in order to maintain flatness, and it is difficult to manufacture a thick correction plate having such a large area. In view of the foregoing, an object of the present invention is to provide a projection optical system which can correct nonlinear components (random components) of various aberrations and can be manufactured at low cost.

Another object of the present invention is to provide an exposure apparatus having such a projection optical system and a method for manufacturing such a projection optical system.

[0011]

A first projection optical system according to the present invention is a projection optical system (PL) for projecting an image of a first object (R1) onto a second object (W). An optical member (10) having a predetermined refractive power in an optical path from an object to the second object, at least one surface of the optical member having an uneven distribution for reducing asymmetric residual aberration of the projection optical system; It has been processed into a surface shape having

In the present invention, the residual aberration means the optical member (10), when considering the ideal image forming position when the projection optical system (PL) is an ideal optical system having no aberration.
That is, it indicates the amount of deviation between the actual image forming position of the light beam via the projection optical system (PL) and the ideal image forming position. According to the first projection optical system of the present invention, the surface shape of the optical member (10) located in the optical path from the first object (R1) to the second object (W) is processed. The light beam passing through the optical member (10) is deflected by refraction and condensed at an ideal image forming position, so that the asymmetric residual aberration of the projection optical system can be corrected. Further, since the optical member (10) is a member constituting the projection optical system (PL), the projection optical system (PL) can be formed at a lower cost than in the case where a member such as a correction plate is added to the projection optical system. A system can be manufactured.

Next, a second projection optical system according to the present invention comprises:
In a projection optical system (PL) that projects an image of a first object (R1) onto a second object (W), in order from the first object side,
An optical member having a front group (Gf) having a positive refractive power, an aperture stop (AS), and a rear group (Gr) having a positive refractive power. 10) is arranged,
At least one surface of the optical member is processed into a surface shape having a concavo-convex distribution to reduce asymmetric residual aberration of the projection optical system.

According to the second projection optical system of the present invention, since the optical member (10) is arranged in the front group (Gf) or the rear group (Gr), the optical member (10) is used for image formation. The optical member (10) is provided at a position where the light beam passing through the optical member (10) becomes narrow, and the asymmetric residual aberration of the projection optical system (PL) can be corrected with high accuracy.

When the optical member (10) is disposed in the front group (Gf), the focal length of the front group (Gf) is fgf, and the focal length of the optical member (10) is fc. When the distance between the optical member (10) and the aperture stop (AS) is Lc, it is desirable that the following two conditions are satisfied. 0.05 <| Lc / fc | <10 (1) 1.5 <| fgf / fc | <15 (2) Here, the expression (1) defines a range of a suitable position of the optical member. It is. When the value is below the lower limit of the expression (1), an optical member physically located near the aperture stop (AS) is selected as the optical member (10) to be processed, and the optical member (10) is selected. ) Is not preferable because it makes it difficult to attach and detach the components. On the other hand, when the value exceeds the upper limit of the expression (1), the optical member (10) is too close to the first object (R1), and it becomes difficult to attach or detach the optical member (10). Not preferred.

The expression (2) indicates that the optical member (10)
Defines a preferable range of the refractive power. When the value exceeds the upper limit of the expression (2), the refractive power of the optical member (10) becomes too strong, and the eccentric sensitivity of the optical member (10) becomes too large. Positioning becomes difficult, which is not preferable. On the other hand, (2)
Exceeding the lower limit of the expression is not preferable because a projection optical system that is telecentric on both sides cannot be formed.

If the optical member (10) is subsequently disposed in the group (Gr), then the focal length of the group (Gr) is fgr, the focal length of the optical member (10) is fr, and When the distance between the optical member (10) and the aperture stop (AS) is Lr, it is desirable that the following two conditions are satisfied. 0.05 <| Lr / fc | <6 (3) 0.5 <| fgr / fc | <5 (4) Here, the expression (3) represents a range of a suitable position of the optical member (10). It is specified. If the value is below the lower limit of the expression (3), the optical member physically located close to the aperture stop (AS) is selected as the optical member (10) to be processed. ) Is not preferable because it makes it difficult to attach and detach the components. on the other hand,
When the value exceeds the upper limit of the expression (3), the optical member (1)
0) is too close to the second object (W), which makes it difficult to attach or detach the optical member (10), which is not preferable.

The expression (4) indicates that the optical member (10)
Defines a preferable range of the refractive power. When the value exceeds the upper limit of the expression (4), the refractive power of the optical member (10) becomes too strong, and the eccentric sensitivity of the optical member (10) becomes too large. Positioning becomes difficult, which is not preferable. On the other hand, (4)
Exceeding the lower limit of the expression is not preferable because a projection optical system that is telecentric on both sides cannot be formed.

The focal length f of the optical member (10)
c preferably satisfies the following conditional expression. The unit is mm, and the same applies to the following expressions (6) to (9). 100 <| fc | <200 (5) When selecting an optical member constituting the front group (Gf) as the optical member (10), it is preferable that the following conditional expressions are satisfied.

10 <Lc <1000 (6) 300 <| fgf | <1500 (7) Further, when an optical member constituting the group (Gr) is subsequently selected as the optical member (10), It is preferable to satisfy the conditional expression. 10 <Lr <600 (8) 100 <| fgr | <500 (9) Next, the exposure apparatus according to the present invention provides a projection optical system (PL) of the present invention and a mask stage (RS) holding a mask (R1). ) And a substrate stage (WS) for positioning a substrate (W), wherein the mask is used as the first object and the substrate is used as the second object, and an image of the pattern of the mask is used as the image. The projection is performed on the substrate via the projection optical system.

According to the exposure apparatus of the present invention, since the projection optical system (PL) of the present invention is provided, the asymmetric residual aberration of the projection optical system (PL) can be corrected with high accuracy. The pattern of the mask (R1) can be transferred onto the substrate (W) with high accuracy. Next, a method for manufacturing a projection optical system according to the present invention is a method for manufacturing a projection optical system for projecting an image of a first object (R1) onto a second object (W). A first step of measuring asymmetric residual aberration of the optical member (1), and an optical member (1) having a predetermined refractive power among optical members constituting the projection optical system (PL).
0) and a second step of calculating the surface shape of the optical member (10) selected in the second step, which cancels the residual aberration, based on the measurement result in the first step. The three steps and the optical member (10) selected in the second step are removed from the projection optical system (PL), and the optical member (10) is adjusted to have the surface shape calculated in the third step. It has a fourth step of processing and a fifth step of installing the optical member (10) processed in the fourth step in the optical path of the projection optical system (PL).

According to the projection optical system manufacturing method of the present invention, an optical member (10) having a predetermined refractive power is selected from the optical members constituting the projection optical system (PL), and the optical member is selected. In order to process the member (10) into a surface shape that cancels out the asymmetric residual aberration of the projection optical system (PL), a member such as a correction plate is added to the projection optical system to correct the asymmetric residual aberration. As compared with the case, a projection optical system in which asymmetric residual aberration is corrected can be manufactured at low cost.

Further, in the method of manufacturing a projection optical system according to the present invention, the projection optical system (PL) includes an aperture stop (A).
S), its first object (R1) and its aperture stop (A
S) and its aperture stop (A)
S) and the rear group (Gr) located between the second object (W)
In the second step, the front group (G
When selecting the optical member (10) from f), it is preferable to select an optical member that satisfies the above-described expressions (1) and (2). On the other hand, in this case, when the optical member (10) is subsequently selected from the group (Gr) in the second step, it is preferable to select an optical member that satisfies the above equations (3) and (4).

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is applied to a projection optical system of a projection exposure apparatus for manufacturing a semiconductor device. FIG. 3 is a diagram showing a schematic configuration of the projection exposure apparatus of the present embodiment. Hereinafter, the optical axis A of the projection optical system PL will be described.
The description will be made by taking the Z axis parallel to X, the X axis parallel to the plane of FIG. 3, and the Y axis perpendicular to the plane of FIG. The illumination optical device IS has, for example, 365 nm (i-line of a mercury lamp), 24
8 nm (KrF excimer laser light), 193 nm (Ar
F excimer laser light), the exposure light wavelengths, such as 157 mm (F ₂ laser), and uniformly illuminates the reticle R1 placed on the reticle stage RS. Below the reticle R1, a projection optical system PL having a predetermined reduction magnification (for example, 1/4, 1/5, etc.) and substantially telecentric on both sides is provided.
The projection optical system PL includes a reticle R
The lens unit includes, in order from the first side, a front group Gf having a positive refractive power, an aperture stop AS, and a rear group Gr having a positive refractive power. It corresponds to the reduction ratio. In the front group Gf, a member to be processed 10 made of a refractive optical member having a positive or negative refractive power and processed to correct an asymmetric component of various aberrations (such as distortion) of the projection optical system PL is provided. The workpiece 10 is included in the projection optical system PL by the holding member 11. Here, the projection optical system PL of the present example is optically designed so that aberration correction is performed in a state including the workpiece 10. Therefore, the light from the reticle R1 illuminated by the illumination optical device IS reaches the wafer W placed on the wafer stage WS via the projection optical system PL including the workpiece 10 and is then transferred to the wafer W by the reticle R1. A reduced image of the pattern is formed. This wafer stage WS is X
The wafer W is positioned in the direction, the Y direction, and the Z direction. In the present example, the member to be processed 10 is formed of a plano-convex single lens made of a glass material (optical material) such as synthetic quartz glass (SiO ₂ ) or fluorite (CaF ₂ ) that transmits exposure light.

FIG. 2A is a plan view of the workpiece 10 of the present embodiment, and in FIG.
Is provided with an orientation flat 12 for positioning by notching a cylindrical side surface. Preferably, the workpiece 10 is provided with an orientation flat or alignment mark for alignment as in this example. Thereby, the workpiece 10 can be attached to the projection optical system PL with high positioning accuracy. Note that the orientation flat and the alignment make may be used together. Further, when an alignment mark is provided on the workpiece 10 to optically detect a position with respect to the holding member 11 (the lens barrel of the projection optical system PL), it is desirable to provide the alignment mark at a position where the exposure light does not pass. .

As shown in FIG. 2B, the workpiece 10 has a plano-convex shape in which one surface is processed into a flat surface and the other surface is polished into a spherical shape so as to have a predetermined radius of curvature. In this example, the plane side of the workpiece 10 is a processed surface 10a on which processing for correcting asymmetric components of various aberrations of the projection optical system PL is performed. The optical member selected as the member to be processed 10 from among the plurality of optical members constituting the projection optical system PL is preferably a plano-convex single lens or a plano-concave single lens as in this example. It is preferable that the projection optical system PL be a processed surface on which processing for correcting asymmetric components of various aberrations is performed. In this case, there is an advantage that the processing is easy and the processing can be performed with high accuracy.

A ring-shaped holding member 11 for holding the workpiece 10 in the lens barrel of the projection optical system PL is shown in FIG.
As shown in (c), the workpiece 10 has a convex portion 11 a corresponding to the orientation flat 12.
That is, the holding member 11 is mounted so that the workpiece 10 can be attached to the projection optical system PL with high alignment accuracy.
Are formed in accordance with the outer shape of the workpiece 10.

Next, a method of correcting asymmetric components (asymmetric components with respect to the optical axis) of various aberrations of the projection optical system PL of the present embodiment, that is, a random component will be described. First, as shown in step ST1 of FIG. 1A, random components of various aberrations of the projection optical system PL are measured. Next, in step ST2, an optical member having a predetermined refractive power is selected as the workpiece 10 from the optical members constituting the projection optical system PL,
With respect to the workpiece 10, a surface shape that cancels out the random components of the various aberrations of the projection optical system PL is calculated based on the measurement results. Then, in step ST3, the processing target member 10 is removed from the projection optical system PL, and the processing target portion 10b of the processing target surface 10a of the processing target member 10 is processed to have the surface shape calculated by, for example, the small tool PRB. Then, the processed workpiece 10 is placed again in the optical path of the projection optical system PL.

As described above, by processing the surface shape of the workpiece 10 constituting the projection optical system PL, the light beam passing through the workpiece 10 is deflected by refraction, as shown in FIG. 1B. , Random components of various aberrations of the projection optical system PL can be corrected. Next, the projection optical system PL
The method of measuring the random components of the various aberrations will be described in detail. In this example, before measuring the random components of the various aberrations of the projection optical system PL, the symmetric components of the various aberrations of the projection optical system PL are measured in advance, and based on the measurement results, the projection optical system PL is measured.
Are adjusted and the tilt and shift of the optical members are adjusted to correct the symmetric components of various aberrations of the projection optical system PL.

First, returning to FIG. 3, the test reticle TR is mounted on the reticle stage RS. As shown in FIG. 4, the test reticle TR includes a plurality of crosses arranged in a matrix in a pattern area PA surrounded by a light-shielding band LST that blocks exposure light, that is, a plurality of crosses arranged on lattice points of a square lattice. It has marks M (0,0) to M (8,8).

Next, returning to FIG. 3, the reticle stage R
The test reticle TR on S is illuminated by the exposure light of the illumination optical device IS. The light from this test reticle TR
Through the projection optical system PL, a photosensitive material such as a resist reaches an exposure area on the wafer W coated on the surface, and marks M (0,0) to M of the test reticle TR are formed on the wafer W.
An image (latent image) of (8, 8) is formed. Thereafter, the exposed wafer W is subjected to a developing process, and the images of the exposed marks M (0,0) to M (8,8) are patterned.

FIG. 5 shows a plurality of marks patterned in the exposure area EA on the wafer W. In FIG. 5, intersections IP (0,0) to IP (8,8) of dotted lines are shown.
Indicates an ideal image forming position, which is an image forming position when the projection optical system PL is an ideal optical system (optical system having no aberration). Also,
The pattern P (0,0) corresponding to the mark M (0,0) on the test reticle TR is the test reticle T
The pattern P corresponding to the mark M (0, 1) on R is the pattern P
(0, 1), and the following marks and patterns correspond in the same manner.

Thereafter, the XY coordinates of each of the plurality of patterns P (0,0) to P (8,8) formed on the wafer W are measured by a coordinate measuring machine. In this example, by processing the shape of the processing surface 10a of the processing member 10,
The plurality of patterns P (0,0) to P (8,8) are respectively displaced to the corresponding ideal imaging positions IP (0,0) to IP (8,8).

Next, a method of calculating the surface shape of the workpiece 10 for correcting random components of various aberrations of the projection optical system PL will be specifically described. As shown in FIG. 3, the member to be processed 10 in the present example includes a front group Gf of the projection optical system PL.
Is located inside. This position is relatively high in numerical aperture (N
Since (A) is a position through which a thin light beam passes, the displacement of the principal ray may be typically considered among the light beams that are displaced by the change in the surface shape of the workpiece 10.

Here, the ideal imaging position IP shown in FIG.
(0,0) to IP (8,8) and a plurality of patterns P (0,
0) to P (8,8), w is the shift amount, and the principal ray from the plurality of marks M (0,0) to M (8,8) is the point at which the principal ray passes through the workpiece 10. Assuming that the amount of change in the angle of the normal to the surface of the workpiece 10 at the passing point is θ, the following equation is established.

W = β · Lr (n−1) · θ (10) The angle change θ is relative to the normal line of the surface of the workpiece 10 (the processing surface 10a) in the reference state before the processing. Here, β is the projection magnification of the projection optical system, Lr is the distance along the optical axis direction between the reticle R1 and the processing surface 10a of the processing member 10, and n is the refractive index of the processing member 10. In the expression (10), the processing surface 1 of the processing member 10 is used.
0a is the surface on the wafer W side.

When the workpiece 10 is in the optical path between the projection optical system PL and the wafer W, the following equation is established. w = Lw (n−1) · θ (11) where Lw is the processing surface 1 of the wafer W and the processing member 10
0a along the optical axis direction.

The processing surface 10a of the processing member 10
May be either the surface on the reticle R1 side or the surface on the wafer W side of the workpiece 10, and the workpiece surface 10a is desirably a flat surface as described above. As described above, the plurality of patterns P (0,0) to P
Coordinates of (8,8) and ideal imaging positions IP (0,0) to IP
From the deviation w from (8, 8), the surface normal at the principal ray passing point of the processed surface 10a of the processed member 10 can be obtained.
Thereby, the surface normal of the workpiece 10 is determined at each principal ray passing point. Then, from this surface normal, the tangent vector of the surface at the principal ray passing point can be obtained, so using the Coons formula that complements the curved surface from the coordinates of the point and the tangent vector of the surface at that coordinate, A continuous surface shape can be determined.

However, as shown in FIG.
For example, if the tangent vectors θ (0,0) and θ (1,0) at the adjacent coordinates of the point Q (0,0) and the point Q (1,0) are equal, the complemented curved surface is undulated. Problems arise. Therefore, in this example, as shown in FIG. 6B, the coordinates Q (0,0) are set between adjacent chief rays.
, The vector component in the Z direction of the tangent vector θ (0,0) at the height Z (1,0) in the Z direction, and the coordinates Q
It is added to the coordinate Q (1,0) next to (0,0). Thereby, even when the tangent vectors of the adjacent coordinates Q (0,0) and Q (1,0) are both equal, the complemented curve is represented by these coordinates Q (0,0), Q (1,0). , The coordinates Q (0,0), Q (1,
The principal ray passing between 0) is refracted at substantially equal angles.
Therefore, even when the correction amounts due to the principal rays passing through the adjacent principal ray passing points are equal, the correction amounts of the various aberrations of the projection optical system PL can be equalized between these adjacent principal ray passing points. .

Next, the procedure for surface complementation in this embodiment will be specifically described. First, as shown in FIG.
The XYZ coordinates are set on the 0-processed surface 10a. In FIG. 7, the principal ray of the light beam traveling from the plurality of marks M (0,0) to M (8,8) to the plurality of patterns P (0,0) to P (8,8) is a member to be processed. The principal ray passing points Q (0,0) to Q (8,8) passing through 10 are indicated by intersections of broken lines. Here, the normal vector at each of the principal ray passing points Q (0,0) to Q (8,8) obtained by the above equation (11) is represented by θ (i, j), and each principal ray passing point Q (0,0)
Let Z (i, j) be the height in the Z direction at Q to (8,8). However, in this example, i = 0 to 8 and j = 0 to 8.

Based on the normal vector θ (0,0) of the principal ray passing point Q (0,0), the principal ray passing point of coordinates adjacent to the principal ray passing point Q (0,0) on the Y axis. Q (0,
The height Z (0, 1) in the Z direction in 1) is calculated by the following equation. Z (0, j) = Z (0, j-1) + θy (0, j-1) · (y (0, j) −y (0, j-1)) (12) where θy (0, j) is the principal ray passing point Q (0, j)
, The vector component in the Y-axis direction of the normal vector θ (0, j), y (0, j) is defined with the principal ray passing point Q (0, 0) at the principal ray passing point Q (0, j) as the origin. This is the component in the Y-axis direction of the coordinate value when taken. Note that the principal ray passing point Q
Using (0,0) as a reference in the Z-axis direction, Z (0,0) = 0
And Then, the principal ray passing points Q (0, 2) on the Y axis
Similarly, for Q (0,8), the height Z (0,
2) Calculate Z to (0,8).

Further, based on the normal vector θ (0,0) of the principal ray passing point Q (0,0), the principal ray having coordinates adjacent to the principal ray passing point Q (0,0) on the X axis. Passing point Q
The height Z (1,0) in the Z direction at (1,0) is calculated by the following equation. Z (i, 0) = Z (i-1,0) + θx (i-1,0) · (x (i, 0) −x (i-1,0)) (13) where θx (i, 0) is the principal ray passing point Q (i, 0)
, The vector component x (i, 0) of the normal vector θ (i, 0) in the X-axis direction is based on the principal ray passing point Q (0,0) at the principal ray passing point Q (i, 0). This is the component in the X-axis direction of the coordinate value when taken. Then, with respect to the principal ray passing points Q (2,0) to Q (8,0) on the X axis, the heights Z (2,0) to Z (8,0) in the Z direction are similarly calculated.

As shown in FIG. 8, the height Z (i, j) in the Z direction at the principal ray passing point Q (i, j) between the X axis and the Y axis is calculated based on the following equation. calculate. Z (i, j) = ｛Z (i-1, j) + θx (i-1, j) · (x (i, j) −x (i-1, j)) + Z (i, j-1) + Θy (i, j−1) · (y (i, j) −y (i, j−1))｝ / 2 (14) As shown in FIG. 9, the principal ray passing point Q (1,1) After calculating the height Z (1,1) in the Z direction, the principal ray passing point Q (1,1)
2), Q (2,1), Q (2,2) ... Q (i, j) ... Q
(I, j)... Q (8, 8) height Z (1,
2), Z (2,1), Z (2,2) ... Z (i, j) ... Z
(8, 8) are calculated based on equation (14).

The height Z (i, j) in the Z direction at the principal ray passing point Q (i, j) and the X of the principal ray passing point Q (i, j)
The principal ray passing point Q (i, j) obtained from the Y coordinate and the surface normal vector θ (i, j) at the principal ray passing point Q (i, j)
Based on the tangent vector in j), a curved surface is formed by the Coons patch technique. Thereby, the workpiece 10 that corrects random components of various aberrations of the projection optical system PL
Can be obtained.

Next, a method of processing the surface shape of the workpiece 10 will be described. The workpiece 10 is removed from the projection exposure apparatus shown in FIG. 3, and the surface shape of the removed workpiece 10 is processed based on the obtained surface shape data. Here, in order to correct a random component, the workpiece 10 in this example has a random and irregularly undulating surface shape. Therefore, in this example, a polishing apparatus as shown in FIG. 10 is used. In FIG. 10, the XZ coordinate system is used.

In FIG. 10, the workpiece 10 is XY
The stage 21 is mounted on a holding part 21 a on a stage 21 which is movable in the direction. The drive unit 22 that moves the stage 21 in the X and Y directions is controlled by the control unit 20. To detect the position in the XY directions when the stage 21 is moved by the drive unit 22, a detection unit 30 including an encoder, an interferometer, and the like is provided on the stage 21. The detection signal from the detection unit 30 is transmitted to the control unit 20.

The polishing plate 23 is attached to one end of a rotary shaft 25 via a holding portion 24, and is rotatable about the Z direction in the figure. At the other end of the rotating shaft 25,
A motor 26 controlled by the control unit 20 is attached. Bearing 27 that rotatably supports rotating shaft 25
Is provided movably in the Z direction with respect to a support portion 28 fixed to a main body (not shown). A motor 29 controlled by the control unit 20 is attached to the support unit 20. The operation of the motor 29 causes the bearing 27 to move along the Z direction, thereby moving the polishing plate 23 along the Z direction. I do. The holding unit 2 that holds the polishing plate 23
4 is provided with a sensor (not shown) for detecting a contact pressure between the polishing plate 23 and the workpiece 10, and an output from this sensor is transmitted to the control unit 20.

Next, the operation of the polishing apparatus shown in FIG. 10 will be briefly described. First, the above-described surface shape data is input to the control unit 20. Thereafter, the control unit 20 controls the polishing plate 2
While rotating the stage 3, the stage 21 is moved along the XY directions via the drive unit 22. That is, the polishing plate 23 moves so as to trace the work surface 10a of the work member 10 along the XY directions. The amount of polishing on the processing surface 10a at this time is determined by the contact pressure between the processing surface 10a and the polishing plate 23 and the residence time of the polishing plate 23.

Thereafter, an antireflection film is deposited on the workpiece 10 processed by the polishing apparatus of FIG. 10, and the workpiece 10 processed by the projection exposure apparatus of FIG. Place. In the polishing apparatus shown in FIG. 10, the polishing plate 23 is fixed in the XY directions, but the polishing plate 23 may be moved instead of moving the stage 21 in the XY directions.

As described above, by processing the surface shape of the workpiece 10 constituting the projection optical system PL, the light beam passing through the workpiece 10 is deflected by refraction.
Random components of various aberrations of the projection optical system PL can be corrected. Further, since the workpiece 10 is an optical member constituting the projection optical system PL, the projection optical system PL is compared with a case where a correction plate for correcting various aberrations of the projection optical system PL is added to the projection optical system PL. Can be manufactured at low cost.

Next, an embodiment of the projection optical system PL will be described with reference to FIG.
This will be described with reference to FIG. FIG. 15 shows an example of a lens configuration of the projection optical system PL. In FIG. 15, the projection optical system PL has a first lens group G1, a second lens group G2, a third lens group G3, And a fourth lens group G4. The first lens group G1 includes a plano-convex lens L11, a biconvex lens L12, and a reticle R, each having a flat surface facing the reticle R side from the reticle R side.
It comprises a negative meniscus lens L13 with a convex surface facing the side, a biconvex lens L14, and a biconvex lens L15. The plano-convex lens L11 corresponds to the workpiece 10 in FIG.

The second lens group G2 includes a negative meniscus lens L having a convex surface facing the reticle R side in order from the reticle R side.
21, a biconvex lens L22, a negative meniscus lens L23 having a convex surface facing the reticle R side, a biconcave lens L24, a biconcave lens L25, and a biconcave lens L26. The third lens group G3 includes, in order from the reticle R side, a positive meniscus lens L31 having a convex surface facing the wafer W side, a negative meniscus lens L32 having a convex surface facing the wafer W side, and a positive meniscus lens L32 having a convex surface facing the wafer W side. It comprises a meniscus lens L33, a biconvex lens L34, and a biconvex lens L35.

The fourth lens group G4 includes, in order from the reticle R side, a positive meniscus lens L having a convex surface facing the reticle R side.
41, a negative meniscus lens L42 having a convex surface facing the reticle R side, a negative meniscus lens L43 having a convex surface facing the reticle R side, a biconcave lens L44, a negative meniscus lens L45 having a convex surface facing the wafer W side, and the wafer W Positive meniscus lens L46 with the convex surface facing the side, positive meniscus lens L47 with the convex surface facing the wafer W side, and biconvex lens L
48, a negative meniscus lens L49 having a convex surface facing the wafer W side, a biconvex lens L410, a positive meniscus lens L411 having a convex surface facing the reticle R side, a positive meniscus lens L412 having a convex surface facing the reticle R side, and the reticle R.
Positive meniscus lens L413 with a convex surface facing the negative side, negative meniscus lens L41 with a convex surface facing the reticle R side
4 and a positive meniscus lens L415 having a convex surface facing the reticle R side. Meniscus lenses L46 and L4
7, an aperture stop AS is arranged.

Tables 1 and 2 below show the values of the specifications of the projection optical system shown in FIG. 15 and the values corresponding to the conditional expressions. Here, a indicates the maximum object height, and NA indicates the image-side maximum numerical aperture. Further, the surface numbers in the first column at the left end indicate the order of the surfaces from the reticle side, ri in the second column is the radius of curvature (mm) of the lens surface, and di in the third column is the on-axis spacing of each surface, that is, the surface spacing. (Mm) are shown. Further, the radius of curvature of the convex surface toward the reticle side is positive, and the radius of curvature of the concave surface is negative. Then, a synthetic quartz (Si0 ₂₎ manufactured by a single glass material any of the lens. Further, assuming that the exposure wavelength is the wavelength (248 nm) of the KrF excimer laser light, the refractive index n of the synthetic quartz with respect to this is n =
1.50839.

[0055]

[Table 1]

[0056]

(2) fcf / fc = 0.614 (3) Lr / fc = 0.155 (4) fgr / fc = 0.599

Next, the plano-convex lens L11 of the projection optical system having the lens configuration shown in FIG. 15 is selected as the member to be processed 10 in FIG. 3 and subjected to processing for correcting random components of various aberrations of the projection optical system. 4 shows the results of measuring various aberrations of the projection optical system. Here, test exposure is performed using a test reticle having a total of 11 × 7 cross-shaped marks arranged in a matrix, 11 in the X direction and 7 in the Y direction. Measure the components. FIG. 11 shows an ideal image forming position in the exposure area EA on the wafer of the pattern P corresponding to the mark on the test reticle.

FIG. 13 shows that the unprocessed workpiece is attached to the projection optical system, test exposure is performed, and after the wafer is developed, the amount of deviation of the image formation position of the pattern on the wafer from the ideal image formation position is measured. In FIG. 13, the horizontal axis represents the image height x in the X direction, and the vertical axis represents the amount of deviation ΔX in the X direction and the amount of deviation ΔY in the Y direction from the ideal imaging position of the pattern. . 13 (a) to FIG.
3 (c) shows that the image height y in the Y direction is -2, 0, 2 respectively.
(Mm).

FIG. 12 is based on the measurement result of FIG.
Calculate the surface shape to cancel various aberrations of the projection optical system,
FIG. 12 shows a contour map obtained by processing the workpiece to have the calculated surface shape and then measuring the shape of the workpiece 10b of the workpiece by an interferometer.
, Contour lines 13 are lines having the same sag amount measured by the interferometer.

FIG. 14 shows that the workpiece having the surface shape shown in FIG. 12 is attached to the projection optical system and test exposure is performed.
FIG. 14 shows the result of measuring the amount of deviation of the image forming position of the pattern on the wafer from the ideal image forming position after developing the wafer. In FIG. 14, the horizontal axis represents the image height x in the X direction, and the vertical axis represents the pattern height. Represents the amount of deviation ΔX in the X direction and the amount of deviation ΔY in the Y direction from the ideal imaging position. FIG.
FIGS. 4A to 14C show the cases where the image height y in the Y direction is -2, 0, and 2, respectively.

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is applied to a case where illumination conditions are changed in a projection exposure apparatus for manufacturing a semiconductor element. FIG. 16 shows a schematic configuration of a projection exposure apparatus 70 of this example. In FIG. 16, the projection exposure apparatus 70 includes a wafer stage 72 on which a wafer as a photosensitive substrate (not shown) is mounted, and a wafer stage 72 The apparatus includes a projection optical system PL1 disposed above, a reticle R2 as a mask disposed above the projection optical system PL1, and an illumination optical system 71 for illuminating the reticle R2 with exposure light.

The wafer stage 72 is configured to be movable in a two-dimensional direction of an X axis parallel to the paper surface and a Y axis orthogonal to the paper surface in a horizontal plane orthogonal to the paper surface in FIG. The drive of the wafer stage 72 in the two-dimensional direction (X and Y directions) is performed by a drive system 73. Also,
The position of the wafer stage 72 in the X and Y directions is measured by a laser interferometer (not shown), and the output of the laser interferometer is input to the main control system 74. That is, the main control system 74 controls the position of the wafer stage 72 in the X and Y directions via the drive system 73 while monitoring the output of the laser interferometer.

The projection optical system PL1 is composed of a plurality of optical members having a common optical axis arranged at a predetermined interval in the Z-axis direction orthogonal to the XY plane, and a lens barrel holding these optical members. . In order to correct the linear components of various aberrations of the projection optical system PL1, at least two of the optical members constituting the projection optical system PL1 are spaced and positioned in the Z-axis direction (optical axis direction), and in the X and Y directions. The inclination of is adjustable. These optical members have, for example, approximately 120
支持 Supported at three points at intervals, each supporting point can be driven in the Z-axis direction by an actuator such as a piezo element. Further, as in the first embodiment, random components (non-linear components) of various aberrations of the projection optical system PL1 are applied to the processing target member 10 ′ among the optical members constituting the projection optical system PL1.
Has been applied to correct the

The illumination optical system 71 includes a mercury lamp 36, an elliptical mirror 38, mirrors 40, 44, 54, 58, and a shutter 4.
2, a fly-eye lens 46, an aperture stop plate 48, a blind 52, and a condenser lens 56. Here, each component of the illumination optical system 71 will be described together with its operation. In the "open" state of the shutter 42,
Exposure light (i-line or g-line) emitted from mercury lamp 36
Are condensed by the elliptical mirror 38, reflected by the mirror 40, passed through the position of the shutter 42, reflected again by the mirror 44, transmitted through the fly-eye lens 46 and the aperture stop of the aperture stop plate 48, and transmitted to the blind 52. Reach. Here, the arrangement surface of the blind 52 is conjugate with the pattern formation surface of the reticle R2, and the shape of the illumination region on the reticle R2 is defined by the opening of the blind 52. Exposure light whose shape is defined by the blind 52 is reflected by a mirror 54, condensed by a condenser lens 56, reflected by a mirror 58, and illuminates the reticle R2 from above. Thereby, the image of the circuit pattern formed on the pattern formation surface of reticle R2 is transferred to a wafer (not shown) on wafer stage 72 at a predetermined magnification via projection optical system PL1. On the other hand, when the shutter 42 is in the "closed" state, the exposure light is blocked by the shutter 42, so that the reticle R2 is not illuminated.

As shown in FIG. 17, the above-described aperture stop plate 48 is formed of a disk-shaped member. On this aperture stop plate 48, there is provided an aperture stop 49 having a regular circular aperture at substantially equal intervals.
A, an aperture stop 49B made of a small circular aperture for reducing the σ value that is a coherence factor, a ring-shaped aperture stop 49C for annular illumination, and a plurality of apertures eccentrically arranged for a modified light source method. A modified aperture stop 49D is disposed. In this example, by rotating the aperture stop plate 48, a desired one of the four aperture stops 49A to 49D can be selected. The aperture stop plate 48 is driven to rotate around the Z axis by a rotation drive mechanism 64 controlled by the main control system 74.

Further, in this embodiment, the main control system 74 is provided with a hard disk 68 as a storage unit. In the hard disk 68, the four aperture stops 49A to 49A-4 described above are provided.
Correction values of linear changes of various aberrations of the projection optical system PL1 obtained by test exposure under respective illumination conditions corresponding to 9D are stored in a data file format. next,
A method of processing a member to be processed and a method of creating a data file corresponding to each aperture stop will be described.

First, an aperture stop 49A having a normal circular aperture is set on the optical path of the exposure light, and the unprocessed workpiece 10 'is arranged in the projection optical system PL. Perform exposure. Based on the result of the test exposure, various aberrations of the projection optical system PL1 during normal illumination are measured. Next, based on the measurement result, correction values of a linear component and a random component (non-linear component) that make various aberrations of the projection optical system PL1 at the time of the normal illumination zero are obtained. Then, using the correction values of the random components of the various aberrations of the projection optical system PL1, the surface of the workpiece 10 'is machined so that this value becomes zero, and corresponds to the aperture stop 49A having a normal circular aperture. In other words, the processing target 10 ′ is formed, that is, the processing target 10 ′ is processed into a surface shape having a concavo-convex distribution that reduces various aberrations of the projection optical system PL 1.

Next, using the correction values of the linear components of the various aberrations of the projection optical system PL 1, a data file of the movement amounts of the optical members constituting the projection optical system PL 1 is created and stored in the hard disk 68. Other aperture stops 49B to 49D
In the same manner as described above, test exposure is performed for each illumination condition, various aberrations of the projection optical system PL1 are measured, correction values are obtained, and processing of the workpiece and creation of a data file are performed. Do.

As described above, the processing target member is processed based on the result of the test exposure under the illumination condition using each of the aperture stops, and the created data file is stored in the hard disk 68. Next, the main operation of the projection exposure apparatus 70 of the present embodiment configured as described above prior to actual exposure at the time of exposure will be described.
The control operation will be mainly described.

When an external command, specifically, a command from the operator or a command to change the aperture stop from the host computer is input to the main control system 74, the main control system 74 opens the aperture via the rotary drive mechanism 64. By rotating the aperture plate 48, the aperture is changed to an aperture stop corresponding to the command. At this time, the workpiece in the projection optical system PL is replaced with a workpiece 10 'corresponding to the aperture stop shape. This allows
The non-linear components of various aberrations of the projection optical system PL1 are corrected.
Further, the main control system 74 reads the moving amount of the optical member corresponding to the aperture stop shape from the data file in the hard disk 68, and reads the Z value of the optical member of the projection optical system PL1.
The interval and position in the axial direction (optical axis direction) and the inclination in the X and Y directions are adjusted. Thereby, the linear components of various aberrations of the projection optical system PL1 are corrected.

As described above, the illumination conditions (aperture stop)
After the fluctuations of various aberrations of the projection optical system PL1 due to the change of are corrected, exposure is started. As explained above,
According to this example, it is possible to correct changes in various aberrations of the projection optical system PL1 that occur when the illumination condition using one aperture stop is changed to the illumination condition using another aperture stop. Further, by correcting the change of various aberrations of the projection optical system PL1, it is possible to prevent deterioration of the total overlay (overall misalignment) between process layers under different illumination conditions using different aperture stops. it can.

In this embodiment, the position and inclination of the optical member in the projection optical system in the optical axis direction are adjusted to correct the linear components of various aberrations of the projection optical system. Correction of the linear components of various aberrations of the projection optical system using any method as long as the position in the Z direction can be changed or the optical distance (optical path length) between the reticle and the projection optical system can be changed. May be performed.

Further, in this example, the case where the aperture stop plate 48 and the rotary drive mechanism are used when switching the illumination condition is exemplified. However, the intensity distribution of the exposure light near the position conjugate with the pupil plane of the projection optical system is described. The lighting condition may be switched using any method as long as the lighting condition is changed. next,
A third embodiment of the present invention will be described with reference to FIGS. This example is different from the first embodiment in that the calculation method for the surface shape of the workpiece to correct various aberrations (such as distortion) of the projection optical system is changed. Parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 18 shows a schematic configuration of the projection exposure apparatus of this embodiment. In FIG. 18, in the projection exposure apparatus of this embodiment, the distortion of the projection optical system PL is provided between the reticle R1 and the projection optical system PL. A correction plate CP, which has been subjected to surface shape processing for correcting the above, is arranged. Next, a method of manufacturing the correction plate CP of the present example will be described.

First, similarly to the first embodiment, a plurality of cross-shaped patterns M (0,
0) to M (8, 8) are formed in a matrix in the X and Y directions by using a test reticle TR using a projection optical system PL.
Measure the distortion. In this case, in FIG. 18, the test reticle TR is arranged on the object plane of the projection optical system PL (on the reticle stage RS) instead of the reticle R1 for normal exposure. At this time, between the test reticle TR and the projection optical system PL (on the holding member 14), the parallel plane plate CP1 not functioning as a correction plate at all.
Place.

Next, the test reticle TR is illuminated by the illumination optical device IS, and the marks M (0,0) to M arranged in a two-dimensional matrix of the test reticle TR.
The image of (8, 8) is transferred onto the wafer W via the projection optical system PL. At this time, the surface of the wafer W is
The position of the wafer W is set so as to be adjusted with high precision to the image plane. As a result, as shown in FIG. 5, for example, each mark M (0, 0, 1) on the test reticle TR reflects non-linear distortion remaining in the projection optical system PL.
The images 0) to M (8, 8) are transferred onto the exposure area EA of the wafer W.

Then, the ideal image forming positions IP (0,0) to IP (8,8) as shown by the intersections of the dotted lines in FIG.
8) and corresponding patterns P (0,0) to P
(8, 8) deviation amount in the X and Y directions (distortion amount of projection optical system PL) ωx (0, 0) to ωx
(8, 8), ωy (0, 0) to ωy (8, 8) are quantitatively measured by a registration measuring machine (distortion measuring machine).

Next, a method of calculating the surface shape of the correction plate CP of this embodiment will be described. In this example, the surface shape of the correction plate CP is determined by calculating the amount of displacement of the surface with respect to the reference plane of the correction plate CP at each of a plurality of positions on the surface of the correction plate CP. Note that the reference plane of the correction plate CP is a surface whose normal is the optical axis of the correction plate CP. First,
For simplicity, a case where a correction plate CP is arranged between the projection optical system PL and the wafer W will be considered.

FIG. 19A shows that when a correction plate CP is arranged between the projection optical system PL and the wafer W, a light beam having a certain numerical aperture is affected by the correction surface SCP of the correction plate CP, and is ideal. FIG. 5 is a diagram illustrating a state where an image is formed at an image forming position P1. Here, the light beam having a certain numerical aperture is the correction surface SCP of the correction plate CP.
Is 2R, the refractive index of the correction plate CP is n, and the optical distance (optical path length) of the line segment P1Q1 is l.
1. Assuming that the optical distance of the line segment P1Q2 is l2 and the difference between the thickness of the correction plate CP at the position Q1 and the thickness of the correction plate CP at the position Q2 is Δd, the line segment P1Q1 and the line segment P1Q2
The difference Δl in the optical distance from is expressed by the following equation.

Δl = l1-l2 = (n−1) · Δd (15) FIG. 19B shows that a light beam having a certain numerical aperture is projected onto the projection optical system P.
FIG. 9 is a diagram illustrating a state where an image is formed at a position P2 displaced in the X direction by ωx from the ideal image forming position P1 due to the influence of distortion remaining at L. Here, the distance from the correction surface SCP of the correction plate CP to the image plane (surface of the wafer W) of the projection optical system PL is LW, and the light flux having a certain numerical aperture on the correction surface SCP of the correction plate CP is measured from the center of the light flux. The distance from one end of the light beam and the center of the light beam to the other end of the light beam is R, the optical distance of the line segment P2Q1 is 11, the optical distance of the line segment P2Q2 is 12, and the correction surface SCP of the line segment P2Q1 and the correction plate CP. Intersection with Q3, 2 line segment P2Q1 and line segment P2Q2
Δl (= 11−12), the refractive index of the correction plate CP is n, the difference between the thickness of the correction plate CP at the position Q1 and the thickness of the correction plate CP at the position Q2 is Δd, Assuming that the lengths of the line segments Q1Q3 and Q1Q4 are substantially equal and the triangle P2Q3Q2 is an isosceles triangle, the following equation is obtained.

Tan θ = ωx / LW (16) sin θ ≒ tan θ (17) Δl = 11−12 = 2R · sin θ (18) Then, the following equation is obtained from the relationship between the equations (16) to (18). Is obtained. Δl = 2R · ωx / LW (19) Accordingly, the following expression is obtained from the relationship between Expressions (15) and (19).

Δd = (2R · ωx) / {(n−1) · LW} (20) Equation (20) represents the relationship when the correction plate CP is arranged between the projection optical system PL and the wafer W. Since this is an equation, the following equation is obtained when converted to the case where the correction plate CP is arranged between the reticle R1 and the projection optical system PL. Δd = (2R · ωx · β) / {(n−1) · LR} (21) where LR is the correction surface SC of the correction plate CP from the reticle R1.
The distance to P, β is the projection magnification of the projection optical system PL.

Accordingly, each mark M (0) of the test reticle TR of FIG. 4 is obtained by using the distortion amounts ωx (0,0) to ωx (8,8) of the projection optical system PL in the X direction based on the equation (21). , 0) to M (8, 8)
At each position on P, the difference Δdx in the thickness of the correction plate CP at both ends of the section having a length of 2R in the X direction centered on the position.
(0,0) to Δdx (8,8) can be obtained respectively. Similarly, in the Y direction, each position of the correction plate CP has a length 2R in the Y direction centered on the position.
Of the thickness of the correction plate CP at both ends of the section
0) to Δdy (8, 8) can be obtained. Therefore, at each of a plurality of positions on the surface of the correction plate CP, the amount of displacement of the surface in the optical axis direction with respect to the reference surface of the correction plate CP (the surface having the optical axis of the correction plate CP as the normal) can be obtained.

Next, a method for determining the surface shape of the correction plate CP will be described with reference to FIG. FIG. 20 shows the distortion amount ωx (0,0) in the X direction of the projection optical system PL.
9 shows the distribution in the X direction of the thickness d of the correction plate CP for correcting ωωx (8,0). 20, the horizontal axis x represents the position in the X direction on the correction plate CP, and the vertical axis d represents the thickness of the correction plate CP based on the position of the point q (0). Also,
Points q (0) to q (N) represent the thickness of the correction plate CP at each position separated by a small distance k in the X direction on the correction plate CP.

In each position on the correction plate CP for correcting the amount of distortion ωx (0,0) to ωx (8,0) in the X direction of the projection optical system PL, X
Differences Δdx (0,0) to Δdx (8,8) of the thickness of the correction plate CP at both ends of the section at a minute distance k in the direction are obtained as follows based on the equation (21). Δdx (0,0) = k · β · ωx (0,0) / {(n−1) · LR｝ (22a) Δdx (1,0) = k · β · ωx (1,0) / ｛( (n-1) · LR｝ (22b) Δdx (2,0) = k · β · ωx (2,0) / {(n-1) · LR｝ (22c) Δdx (3,0) = k · β Ωx (3,0) / {(n−1) · LR｝ (22d) Δdx (4,0) = k · β · ωx (4,0) / ｛(n−1) · LR｝ (22e) Δdx (5,0) = k · β · ωx (5,0) / {(n−1) · LR｝ (22f) Δdx (6,0) = k · β · ωx (6,0) / ｛( n−1) · LR｝ (22 g) Δdx (7,0) = k · β · ωx (7,0) / {(n−1) · LR｝ (22h) Δdx (8,0) = k · β Ωx (8,0) / {(n-1) LR} (22i) where the difference between the thicknesses Δdx (0,0) to Δdx
When the value of the minute distance k is determined so that (8, 0) is obtained every other section of the minute distance k, the following equation can be obtained.

Q (1) −q (0) = Δdx (0,0) (23a) q (3) −q (2) = Δdx (1,0) (23b) q (5) −q (4) = Δdx (2,0) (23c) q (7) −q (6) = Δdx (3,0) (23d) q (9) −q (8) = Δdx (4,0) (23e) q ( 11) −q (10) = Δdx (5,0) (23f) q (13) −q (12) = Δdx (6,0) (23g) q (15) −q (14) = Δdx (7, 0) (23h) q (17) −q (16) = Δdx (8,0) (23i) Then, the relationship of the expressions (22) and (23) is satisfied, and the thickness q at each position of the correction plate CP is satisfied. The correction plate CP so that the points (0) to q (N) are smoothly connected as shown in FIG.
Are obtained for the thicknesses q (0) to q (N) at each position.

Here, in order to minimize the difference in thickness between regions at a minute distance k adjacent to each other, the thickness at each position of the correction plate CP that minimizes the function represented by the following equation What is necessary is just to obtain the values of q (0) to q (N). f (q (0), q (1), ..., q (N)) = {(q (2) -q (1))-(q (1) -q (0))} ² + {(q (3) −q (2)) − (q (2) −q (1))｝ ² + ... + ｛(q (N) −q (N−1)) − (q (N−1) −q (N-2))｝ ² (24) Further, for simplicity of calculation, q (0) = 0.

As described above, the relationship between the expressions (22) and (23) is satisfied, and the function f (q (0), q (1),
.., Q (N)) is the thickness q (1) to q of the correction plate CP which minimizes
By calculating the value of (N), the thickness d in the X direction of the correction surface SCP of the correction plate CP for correcting the distortion amounts ωx (0,0) to ωx (8,0) of the projection optical system PL.
Can be obtained.

Therefore, the distortion amounts ωx (0,0) to ωx (8,8) and ωy (0,0) of the projection optical system PL
On the basis of (0) to ωy (8, 8), the distribution of the thickness of the correction plate CP for correcting this in the XY two-dimensional directions, that is, the surface shape of the correction plate CP can be obtained. The correction plate C
As a method of calculating the thickness value at each position of P,
Difference of thickness Δdx (0,0) at each position of correction plate CP
Any value can be used as long as the thickness values at the respective positions of the correction plate CP can be smoothly connected to each other based on .DELTA.dx (8, 8), and can be determined by using a predetermined data interpolation method. Difference in thickness Δdx (0,0) to Δdx
(8, 8) may be the inclination of the correction plate CP with respect to the reference plane, and the thickness value at each position of the correction plate CP may be interpolated.

Next, returning to FIG. 18, the parallel plane plate CP1 is removed from the projection exposure apparatus, and the parallel plate CP is obtained based on the information of the two-dimensional distribution of the thickness d of the correction plate CP obtained as described above. Parallel flat plate C using a processing device for flat plate processing
Work the surface of P1. Thereby, it is possible to manufacture a correction plate CP having a correction surface SCP for correcting distortion remaining in the projection optical system PL.

Then, the correction plate CP manufactured as described above is mounted on the holding member 14 of the projection exposure apparatus shown in FIG. Thereby, the distortion of the projection optical system PL can be corrected, and the pattern on the reticle R1 can be accurately transferred onto the wafer W arranged on the image plane of the projection optical system PL without distortion. In this example, the case where the parallel plane plate is processed to form a correction plate for correcting various aberrations of the projection optical system has been described as an example. However, as in the first embodiment, the configuration of the projection optical system is In the case where an optical member having a predetermined refractive power is selected from the optical members to be processed, and processing for correcting various aberrations of the projection optical system is performed,
It goes without saying that the surface shape calculation method of the present embodiment can be used.

In the third embodiment, when processing the parallel plane plate CP1, information on the two-dimensional distribution of the thickness d of the correction plate CP is used, that is, the processing amount of the parallel plane plate CP1. Is directly instructed, so that there is an advantage that it is easy as compared with the first embodiment in which the processing amount needs to be calculated from the surface shape. It should be noted that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the spirit of the present invention.

[0093]

According to the first projection optical system of the present invention, an asymmetric residual aberration of the projection optical system can be corrected, and a member such as a correction plate is added to the projection optical system to provide an asymmetric residual aberration. A projection optical system can be manufactured at a lower cost than when aberrations are corrected. Next, according to the second projection optical system of the present invention, since the optical member is disposed in the front group or the rear group, the position where the light flux passing through the optical member for imaging is narrowed. That is, the optical member is located at a position other than the above, and the asymmetric residual aberration of the projection optical system can be corrected with high accuracy.

Next, according to the exposure apparatus of the present invention, the asymmetric residual aberration of the projection optical system can be corrected with high accuracy, and the pattern of the mask can be transferred onto the substrate with high accuracy. it can. Next, according to the method for manufacturing a projection optical system according to the present invention, the projection optical system in which the residual aberration has been corrected is reduced in comparison with a case where a member such as a correction plate is added to the projection optical system to correct asymmetric residual aberration. Can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method for correcting various aberrations of a projection optical system according to a first embodiment of the present invention.

2A is a plan view showing a workpiece to correct various aberrations of a projection optical system, FIG. 2B is a perspective view of the workpiece shown in FIG. 2A, and FIG. FIG. 3 is a perspective view showing a holding member for holding the workpiece shown in FIG. 2A in the projection optical system.

FIG. 3 is a schematic configuration diagram of a projection exposure apparatus used in the first embodiment of the present invention.

FIG. 4 is a plan view showing a configuration of a test reticle used for measuring various aberrations of a projection optical system.

FIG. 5 is a view showing an example of a pattern on a wafer formed using the test reticle of FIG. 4;

FIG. 6 is a diagram for explaining a curved surface complementing formula according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a technique of surface complementation according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a method of surface complementation according to the first embodiment of the present invention.

FIG. 9 is a diagram illustrating a technique of surface complementation according to the first embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a polishing apparatus for processing a member to be processed.

FIG. 11 is a view showing an ideal image forming position of a cross mark on a test reticle in an exposure area on a wafer.

FIG. 12 is a diagram illustrating an example of a shape of a processed portion of a processed member for correcting various aberrations of a projection optical system.

FIG. 13 is a diagram illustrating an example of measurement results of various aberrations of the projection optical system.

FIG. 14 is a diagram illustrating an example of measurement results of various aberrations of the projection optical system.

FIG. 15 is a diagram illustrating an example of a lens configuration of a projection optical system.

FIG. 16 is a schematic configuration diagram of a projection exposure apparatus used in a second embodiment of the present invention.

FIG. 17 is a diagram showing the aperture stop plate 48 of FIG. 16;

FIG. 18 is a schematic configuration diagram of a projection exposure apparatus used in a third embodiment of the present invention.

FIG. 19 is a diagram illustrating a method of calculating a surface shape for correcting various aberrations of a projection optical system according to a third embodiment of the present invention.

FIG. 20 is a diagram illustrating a method of calculating a surface shape for correcting various aberrations of a projection optical system according to a third embodiment of the present invention.

[Explanation of symbols]

AS: aperture stop, CP: correction plate, Gf: front group, Gr: rear group, IS: illumination optical device, PL: projection optical system, R1, R
2: Reticle, TR: Test reticle, W: Wafer, 1
0: Workpiece member, 11: Holding member, 48: Aperture stop plate,
64: rotation drive mechanism, 68: hard disk, 71: illumination optical system

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA21 LA01 NA01 NA02 NA04 PA15 PA17 PB20 QA01 QA05 QA13 QA21 QA26 QA33 QA42 QA45 RA01 RA11 RA32 RA42 UA03 UA04 5F046 BA04 CA04 CB12 CB25 9A001 BB02 BB03 BB02 BB03 BB02 BB03 BB02 BB03 KK16 KK37 KK54

Claims (9)

[Claims] 1. A projection optical system for projecting an image of a first object on a second object, comprising: an optical member having a predetermined refractive power in an optical path from the first object to the second object. A projection optical system, characterized in that at least one surface of the optical member is processed into a surface shape having a concavo-convex distribution so as to reduce asymmetric residual aberration of the projection optical system. 2. A projection optical system for projecting an image of a first object onto a second object, comprising, in order from the first object, a front group having a positive refractive power, an aperture stop, and a rear group having a positive refractive power. An optical member having a predetermined refractive power is arranged in the front group or the rear group, and at least one surface of the optical member has a concavo-convex distribution that reduces asymmetric residual aberration of the projection optical system. A projection optical system characterized by being processed into a surface shape having the following. 3. The projection optical system according to claim 1, wherein the optical member has a surface shape in which one surface has a flat surface portion and the other surface has a spherical surface portion. A projection optical system characterized by being processed. 4. The projection optical system according to claim 2, wherein the optical member is disposed in the front group, a focal length of the front group is fgf, a focal length of the optical member is fc,
When the distance between the optical member and the aperture stop is represented by Lc, the following two conditions are satisfied. 0.05 <| Lc / fc | <10 1.5 <| fgf / fc | <15 5. The projection optical system according to claim 2, wherein the optical member is disposed in the rear group, a focal length of the rear group is fgr, a focal length of the optical member is fr,
When the distance between the optical member and the aperture stop is Lr, the following two conditions are satisfied. 0.05 <| Lr / fc | <6 0.5 <| fgr / fc | <5 6. An exposure apparatus comprising: the projection optical system according to claim 1; a mask stage for holding a mask; and a substrate stage for positioning a substrate. An exposure apparatus, wherein an image of a pattern of the mask is projected onto the substrate via the projection optical system, using the first object and the substrate as the second object. 7. A method for manufacturing a projection optical system for projecting an image of a first object onto a second object, comprising: a first step of measuring an asymmetric residual aberration of the projection optical system; A second step of selecting an optical member having a predetermined refractive power from the constituent optical members, and for the optical member selected in the second step, the residual aberration is determined based on a measurement result of the first step. A third step of calculating a surface shape that cancels out; and removing the optical member selected in the second step from the projection optical system so that the optical member has a surface shape calculated in the third step. And a fifth step of installing the optical member processed in the fourth step in an optical path of the projection optical system. 8. The method according to claim 7, wherein the third step includes an auxiliary step of calculating an amount of change in the angle of a normal to the surface at each of a plurality of positions on the surface of the optical member.
A manufacturing method of the projection optical system according to the above. 9. The method according to claim 9, wherein the third step includes an auxiliary step of calculating a displacement of the surface with respect to a reference plane of the optical member in the optical axis direction at each of a plurality of positions on the surface of the optical member. A method for manufacturing a projection optical system according to claim 7.