JP2000164489A - Scanning projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve throughput under improved image-forming state, especially under state where longitudinal astigmatic aberration and non-isotropic distortion are corrected appropriately. SOLUTION: In a scanning projection aligner, a pattern image provided on a projection original is formed on a substrate using a projection optical system and the position relationship between a substrate (W) and a projection optical system (PL) is changed along a scanning direction and at the same time projection exposure is made. In the projection aligner, the projection optical system forms an image in a region in a nonisotropic shape, at least two surfaces G1R2 and G17R2 out of the optical surfaces of optical members G1-G30 for composing the projection optical system are in a shape with different power between a specific meridian direction and a direction that orthogonally crosses it, and the optical surfaces of at least two surfaces are in a shape for correcting at least non-isotropic distortion and axial astigmatic difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing a device such as a semiconductor device, a liquid crystal display device, an image pickup device, and a thin film magnetic head by a photographic process. And a scanning projection exposure apparatus of a so-called slit scan type or a step-and-scan type in which a pattern on a projection original is projected and exposed on a substrate by synchronously scanning.

[0002]

2. Description of the Related Art Semiconductor devices, liquid crystal display devices, imaging devices,
When a device such as a thin-film magnetic head is manufactured by a photolithography process, a pattern image of a projection original such as a reticle and a mask is projected and exposed through a projection optical system onto a substrate coated with a photosensitive material such as a photoresist. Projection exposure apparatuses are known. Such a projection exposure apparatus is required to transfer a fine pattern without impairing the high resolving power of the projection optical system.

As a conventional projection exposure apparatus, there is a projection exposure apparatus (stepper) of a batch exposure system (full field system) for simultaneously projecting a pattern of a projection original onto an entire exposure field (shot area) on a substrate. Was common. In recent years, a scanning projection exposure apparatus such as a slit scan method or a step-and-scan method that sequentially projects and exposes a pattern on a projection original onto a substrate has been developed. In this scanning projection exposure apparatus, a pattern area on a projection original is illuminated, for example, in a slit shape, and the projection original is scanned with respect to the slit-shaped illumination area, and a projection optical system is synchronized with the scanning of the projection original. Scanning exposure is performed by scanning the substrate at the same speed ratio as the projection magnification. Further, in this scanning projection exposure apparatus, there is a scanning projection exposure apparatus which does not illuminate a pattern area on a projection original in a slit shape, but limits an exposure area on a substrate to a slit shape by, for example, a field stop in a projection optical system. .

In this scanning projection exposure apparatus, the illumination area on the reticle is smaller than that of the batch exposure method, and therefore the focus position in the exposure field such as the amount of distortion of the projected image, the curvature of field, and astigmatism. And the illuminance non-uniformity can be kept small. Further, the scanning projection exposure apparatus has an advantage that a large area exposure can be performed without being limited by the field size of the projection optical system in the scanning direction.

However, in a scanning projection exposure apparatus, the area that can be exposed per unit time is smaller than that in a batch projection exposure apparatus, so that the throughput (the number of substrates that can be printed per unit time) is reduced. It is said that the method is inferior to the one-shot exposure type projection exposure apparatus.

[0006]

Here, in the scanning projection exposure apparatus, it is conceivable to improve the output of the light source in order to improve the throughput. However, in this case, the following problems occur. 8A and 8B are views showing an exposure area on the image plane of the projection optical system. FIG. 8A shows the case of a scanning projection exposure apparatus, and FIG. The case of is shown. The shape of the exposure area EA of the scanning projection exposure apparatus shown in FIG. 8A is different from that of the collective exposure projection exposure apparatus of FIG. 8B and is not isotropic. Accordingly, there is a bias in the heat distribution of the lens due to the absorption of the exposure light passing through the projection optical system. As shown by the arrows in the figure, the lens has different amounts of thermal expansion in a predetermined direction and a direction perpendicular thereto. Will be caused. At this time, FIG.
As shown in (1), the radius of curvature of the lens surface 10a of the lens 10 changes differently in a predetermined direction (X direction) and in a direction orthogonal to the predetermined direction (Y direction).

Here, consider a case where the radius of curvature 10Rx in the X direction changes sharply and the radius of curvature 10Ry in the Y direction changes slowly. In this case, as shown in FIG. 10, the image forming position of the on-axis object point Oax in a predetermined meridional plane (YZ plane) and the image forming position in a meridional plane (XZ plane) orthogonal thereto. Differ in a direction along the optical axis Ax, and the projection optical system P
In the entire L, astigmatism occurs on the optical axis. Further, in this case, as shown in FIG.
The imaging position of the off-axis object point Oof in the plane (plane) differs from the imaging position of the off-axis object point Oof in the meridional plane (XZ plane) perpendicular to the optical axis Ax, Anisotropic distortion occurs in the entire projection optical system.

Accordingly, an object of the present invention is to improve the throughput under a good imaging state, particularly under a state in which axial astigmatism and anisotropic distortion are well corrected. And

[0009]

In order to achieve the above object, a projection exposure apparatus according to a first aspect of the present invention uses a projection optical system to project an image of a pattern provided on a projection original onto a substrate. A scanning type projection exposure apparatus that performs projection exposure and exposure while relatively changing the positional relationship between the substrate and the projection optical system along the scanning direction, wherein the projection optical system is anisotropic. Forming an image in a region having a general shape, and forming at least two of the optical surfaces of optical members constituting the projection optical system.
The surface has a shape having different powers in a predetermined meridian direction and a direction perpendicular to the meridian direction, and the at least two optical surfaces have at least anisotropic distortion and astigmatic difference on the optical axis. It has a shape that can be corrected.

According to a second aspect of the present invention, in the projection exposure apparatus according to the first aspect, at least four of the optical surfaces of the optical members constituting the projection optical system have a predetermined meridian direction and the meridian direction. The power has a shape different from that in a direction perpendicular to the direction, and the at least four optical surfaces are configured to be rotatable around the optical axis of the projection optical system.

According to a third aspect of the present invention, in the projection exposure apparatus according to the second aspect, the shape of two optical surfaces among the at least four optical surfaces is at least determined by rotating the optical surfaces. It is a shape capable of adjusting the amount of anisotropic distortion, and two optical surfaces different from the two optical surfaces out of the at least four optical surfaces,
By rotating the optical surface, at least the amount of astigmatism on the optical axis can be adjusted.

The astigmatism on the optical axis (on-axis astigmatism) in the present invention refers to the difference in the optical axis direction between the meridional image plane and the sagittal image plane at the image point on the optical axis. Anisotropic distortion refers to aberration in which the amount of distortion at a predetermined image height differs between a predetermined meridian direction and a meridional direction orthogonal thereto.

[0013]

1 and 2 are views for explaining the principle of the present invention. In FIG. 1, as indicated by a broken line in the figure, the image forming position of an on-axis object point in a predetermined meridional plane (YZ plane) and the image forming position in a meridional plane (XZ plane) orthogonal to this are shown. When the astigmatism on the optical axis occurs in the entire projection optical system PL, which differs in the direction along the optical axis Ax, of the optical members (lens elements, reflecting mirrors, etc.) constituting the projection optical system PL , At least one optical member 1
1 is given a surface shape having different powers in the YZ direction and the XZ direction.

In the example of FIG. 1, the optical member 11 has a shape having no power (refractive power) in the YZ plane and a predetermined power (refractive power) in the XZ plane. At this time, when the light from the object point Oax on the optical axis on the object plane O passes through the optical member 11, the light is refracted only in the XZ section, and as shown by the solid line in the figure, An image is formed at the same position in the optical axis direction as the image forming position of the light beam. Thereby, the optical axis A
Astigmatism on x can be corrected.

In FIG. 2, a predetermined meridian plane (YZ)
The imaging position of the off-axis object point in the plane (plane) and the imaging position of the off-axis object point in the meridional plane (XZ plane) orthogonal to the axis are the optical axis A.
When anisotropic distortion occurs in the entire projection optical system PL, which differs in a direction orthogonal to x, at least one of the optical members 12 constituting the projection optical system is in the YZ direction. And a surface shape having different power in the XZ direction.

In the example of FIG. 2, the optical member 12 has a shape having no power (refractive power) in the YZ plane and a predetermined power (refractive power) in the XZ plane. At this time, when the light from the off-axis object point Oof on the object plane O passes through the optical member 12, it undergoes a refraction action only in the XZ section, and as shown by a solid line in the drawing, the light flux in the YZ section An image is formed at the same position in the plane orthogonal to the optical axis (XY plane) as the image formation position. Thereby, anisotropic distortion on the image plane I can be corrected.

As described above, at least two of the optical surfaces (lens surfaces and reflection surfaces) of the optical members in the projection optical system PL have different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction. With such a shape, at least the anisotropic distortion of the projection optical system PL and the astigmatic difference on the optical axis can be corrected. Therefore, the axial astigmatism and the anisotropic distortion are offset by at least two optical surfaces so that the axial astigmatism and the anisotropic distortion generated when the projection optical system is used can be canceled. In this case, even when the output of the light source is increased to improve the throughput, the imaging performance is not deteriorated.

At this time, it is preferable that an optical surface for correcting axial astigmatism is provided near the pupil of the projection optical system, and the optical surface for correcting anisotropic distortion is an object surface or an image surface. Preferably, it is provided near the surface. Now, among the optical members (lenses, reflecting mirrors) in the projection optical system PL, the optical surfaces of at least two optical members have shapes having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction, In addition, if it is relatively rotatable about the optical axis, it is possible to adjust the amount of one of axial astigmatism and anisotropic distortion.

Hereinafter, description will be made with reference to FIGS. 3 (a) and 3 (b). 3A and 3B, the optical members 13, 1
Reference numeral 4 denotes a part of the optical members constituting the projection optical system PL. At least one of these optical members 13 and 14 is provided so as to be rotatable about an optical axis Ax. The optical members 13 and 14 have directions 13A and 14A having the strongest radii of curvature, respectively, and directions 13B and 14B orthogonal to the directions 13A and 14A and having the weakest radii of curvature. Here, in the directions 13A and 14A indicated by solid lines in the figure, the refractive power of the optical members 13 and 14 is the strongest, and in the directions 13B and 14B indicated by broken lines in the figure, the refractive power of the optical members is the weakest. In the following, the directions 13A and 14B in which the radius of curvature (refractive power) is the strongest are referred to as strong principal meridians, and the directions 13B and 14B in which the radius of curvature (refractive power) is the weakest are referred to as weak main meridians.

As shown in FIG. 3A, the strong principal lines 13A and 14A of the two optical members 13 and 14 are 9
When the angle is 0 degree, these two optical members 13 and 14
No axial astigmatism or anisotropic distortion occurs. Further, as shown in FIG. 3B, the strong optical meridians 13A and 14A
If the angle is made different from 90 degrees, an amount of axial astigmatism or anisotropic distortion occurs in accordance with the angle made.

Therefore, for example, of the optical members constituting the projection optical system PL, the optical surfaces of two optical members are shaped to have different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction, and If it is relatively rotatable about the optical axis, one of axial astigmatism and anisotropic distortion can be corrected. Further, the optical surfaces of two optical members different from the two optical members are
If it has a shape having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction, and is relatively rotatable about the optical axis, both axial astigmatism and anisotropic distortion are reduced. Can be corrected.

Therefore, in order to cancel the axial astigmatism and the anisotropic distortion generated when the projection optical system is used, the at least four optical surfaces have the axial astigmatism and the anisotropic distortion. If the distortion is generated as an offset, even if the output of the light source is increased to improve the throughput, the imaging performance will not be degraded, and it is possible to cope with a plurality of types of light sources having different outputs. Can be.

The optical surface for adjusting the amount of on-axis astigmatism is preferably provided near the pupil of the projection optical system. The optical surface for adjusting the amount of anisotropic distortion is preferably , Near the object plane or the image plane. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 is a schematic diagram of a projection exposure apparatus according to an embodiment of the present invention. The projection exposure apparatus shown in FIG. 4 includes an illumination optical device IS for illuminating the reticle R, a reticle stage RS for holding the reticle R, a projection optical system PL for forming a reduced image of the reticle R, and photosensitive elements such as photoresist. Wafer W coated with a conductive resin
A wafer stage WS held via T is provided. Here, the illumination optical device IS is an i-line (wavelength 36) of a mercury lamp.
5 nm), an optical integrator for forming a plurality of light source images or virtual images of the plurality of light sources based on illumination light from the light source unit, a reticle blind, a condenser lens system, and the like. The illumination optical device IS forms a plurality of light source images at the pupil position (position of the aperture stop AS) of the projection optical system PL, that is, the illumination optical device IS performs so-called Koehler illumination.

The pattern image on the reticle R illuminated by the illumination optical device IS is formed on the wafer W by the projection optical system PL having a predetermined reduction magnification β. By the way, prior to the exposure operation, a positioning operation between the reticle R and the wafer W is performed. Here, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken parallel to the plane of FIG. 4 in a plane perpendicular to the Z axis, and the Y axis is taken perpendicular to the plane of FIG. To explain, the reticle stage RS has an X direction, a Y direction,
The reticle R is positioned in the rotation direction, and the wafer stage WS aligns the surface of the wafer W with the image plane of the projection optical system PL and positions the wafer W in the X and Y directions.

Thereafter, an exposure operation is started. At this time,
When exposing one shot area on the wafer W, the reticle R and the wafer W are synchronously scanned with respect to the projection optical system PL with a projection magnification β as a speed ratio to expose a pattern image of the reticle R. The operation of moving the next shot area on wafer W to the exposure area of projection optical system PL and performing exposure by stepping drive of wafer stage WS is repeated in a step-and-scan manner.

The projection optical system PL of the present embodiment has a plurality of lens elements, and the plurality of lens elements have an optical axis Ax
They are arranged along the top. In the present embodiment, among these plurality of lens elements, two lens elements that are close to each other have respective lens surfaces having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction. Further, two lens elements different from the two lens elements, and two lens elements close to each other have lens surfaces having shapes different in power in a predetermined meridian direction and a direction orthogonal to the meridian direction. .

By the action of these four lens surfaces, a desired amount of axial astigmatism and anisotropic distortion can be generated. These desired amounts can be generated by using the axial astigmatism generated when the projection optical system is used. If the aberration and the anisotropic distortion are set so as to be able to cancel each other, even when the output of the light source is increased to improve the throughput, the imaging performance is not deteriorated.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, numerical embodiments of the present invention will be described. FIG. 5 is a lens sectional view of the projection optical system PL of the first embodiment, and FIG. 7 is a lens sectional view of the projection optical system PL of the second embodiment. [First Embodiment] In FIG. 5, a projection optical system PL has an optical axis A
It has a plurality of lens elements G1 to G30 arranged along x. Among the plurality of lens elements G1 to G30,
Lens element G closest to reticle R side (object side)
One lens surface G1R2 on the side of the wafer W is formed in a shape having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction. This lens surface has a function of correcting anisotropic distortion.

The lens surface G17R2 on the wafer W side of the lens element G17 arranged near the position (pupil position) of the aperture stop AS among the plurality of lens elements G1 to G30 is
It is formed in a shape having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction. This lens surface has a function of correcting axial astigmatism. The first
In the projection optical system PL of the embodiment, the lens element G2 and the lens elements G4 to G6 are arranged so as to be independently movable along the optical axis direction, and these lens elements G2 and G4 to G6 are respectively Piezo element driver PD
1, the position in the optical axis direction is controlled by PD2. Also,
The space between the lens element G11 and the lens element G15 is an airtight chamber AM1 sealed from the outside air, and the pressure in the airtight chamber AM1 is controlled by a pressure control unit (not shown). Then, the lens element G20 and the lens element G
26 is an airtight room A sealed from outside air.
The pressure in the airtight chamber AM2 is also controlled by a pressure control unit (not shown).

Here, the lens elements G2, G4 to G6
Is moved in the direction of the optical axis, and the pressure in the airtight chambers AM1 and AM2 is increased / decreased, whereby the isotropic aberration of the projection optical system PL can be corrected. This makes it possible to correct the isotropic component of the aberration generated when the intensity of the lamp is changed, so that the lens surfaces G1R2 and G17 can be corrected.
Anisotropic components to be corrected in R2 (on-axis astigmatism,
The correction amount of anisotropic distortion can be reduced as much as possible.

The lens surface G1R2 in the projection optical system PL of the first embodiment has a function of generating anisotropic distortion, and the amount of the anisotropic distortion is changed by changing the intensity of the lamp. The amount is such that the anisotropic distortion among the aberrations generated at the time can be canceled. Further, the projection optical system P of the first embodiment
The lens surface G17R2 at L has a function of generating on-axis astigmatism. The amount of on-axis astigmatism is determined by the amount of on-axis astigmatism among the aberrations generated when the lamp intensity is changed. It is the amount that can be canceled.

Table 1 below shows the lens data. D0 is the distance on the optical axis from the reticle R to the lens surface on the reticle R side of the lens element G1 disposed closest to the reticle R;
WD is the distance (working distance) on the optical axis from the reticle-side lens surface of the lens element G30 disposed closest to the wafer W to the image plane (wafer W), β is the projection magnification of the projection optical system, Or the unit of the length is mm as an example. Further, in the lower column of Table 1, the leftmost numeral is the order of the lens surfaces from the reticle R (first object) side, r is the radius of curvature of the lens surface in a predetermined meridional direction (meridional direction), and d is the lens. The distance from one surface to the next lens surface, n
Represents the refractive index of the glass material at a wavelength of 365 nm, and the right-most reference numeral represents the reference numeral of the lens element.

[0033]

D0 = 96.34151 WD = 15.53333 β = -0.25 rdn 1 671.10239 14.80316 1.612980 G1 2 304.17256 17.70195 1.000000 3 1800.12100 28.76018 1.615360 G2 4 -294.83934 0.99243 1.000000 5 162.33651 29.85004 1.615360 7900 61.6324. G4 8 0.00000 3.23585 1.000000 9 -1436.07051 9.37482 1.612980 G5 10 91.78283 17.48596 1.000000 11 303.34614 20.93839 1.487340 G6 12 -241.49834 0.98586 1.000000 13 3300.03300 18.37237 1.615360 G7 14 106.51217 27.11385 1.000000 15 -130.360101 15.961 358 316 316 316. 18 1620.65000 0.99258 1.000000 19 1423.87400 34.58149 1.487340 G10 20 -144.20178 0.49987 1.000000 21 -316.64628 22.81938 1.615360 G11 22 -181.74714 0.49251 1.000000 23 -1968.32502 29.12495 1.615360 G12 24 -312.76216 0.67202 1.000000 25 450.72537 31.726. 1.615360 G14 28 1974.73900 0.68874 1.000000 29 227.54939 23.28514 1.615360 G15 30 135.86704 0.69245 1.000000 31 -133.10047 21.15282 1.612980 G16 32 114.68598 37.81791 1.000000 33 -295.57745 15.50758 1.612980 G17 34 216.44577 28.77678 1.000000 37.18.1.636.1361. 38 -522.30541 6.27044 1.000000 39 0.00000 15.52604 1.000000 AS 40 -440.07720 26.39718 1.487340 G20 41 -170.25552 0.71318 1.000000 42 540.79980 39.39782 1.487340 G21 43 -308.61251 0.49137 1.000000 44 695.18515 31.56281 1.615360 29. 0.48859 1.000000 48 681.31343 30.56490 1.615360 G24 49 -582.01710 0.49028 1.000000 50 171.39265 41.11481 1.487340 G25 51 1078.39500 0.48082 1.000000 52 124.36057 41.35491 1.487340 G26 53 553.54147 4.70728 1.000000 54 1355.45200 18.40138 1.612980 G55 4.11263 5.24338 1.000000 56 95.82394 36.19782 1.487340 G28 57 -1172.64608 0.96729 1.000000 58 572.67338 16.40858 1.612980 G29 59 93.23125 0.97305 1.000000 60 69.00901 26.08456 1.487340 G30 61 296.67188 (WD) 1.000000 Lens surfaces G1R2 and G1R2 in Table 2 below
3 shows the surface shape data of FIG. In Table 2 below,
Rx is the radius of curvature of the lens surface in a predetermined meridian direction, and Ry is the radius of curvature of the lens surface in a direction orthogonal to the meridian direction.

[0034]

[First Example] G1R1 (second surface) Rx = 304.17256 (predetermined meridian direction) Ry = 304.17907 (direction orthogonal to the meridian direction) G17R2 (34th surface) Rx = 216.5777 (predetermined meridian) Direction) Ry = 216.44399 (direction orthogonal to the meridian direction) By converting the lens surface G1R2 into an as-surface (a surface having a different radius of curvature between the predetermined meridian direction Mx and the direction My orthogonal to the meridian direction) as described above. In the image plane of the projection optical system PL, as shown by an arrow in FIG.
On the other hand, in the direction My perpendicular to the meridian direction, anisotropic distortion of +0.005 μm occurs at the position of the maximum image height Ymax = 13.2 mm.

Further, by forming the lens surface G17R2 as as above as described above, at the image point on the optical axis on the image plane of the projection optical system PL, +0.23 μm axial astigmatism (predetermined meridian) (An interval along the optical axis between the image plane in the direction Mx and the image plane in the direction My orthogonal to the meridian direction). These values are obtained when the units of the radius of curvature and the surface interval in Tables 1 and 2 are mm.

As described above, in the first embodiment, the two lens surfaces (G1R2, G17R2) of the plurality of lens elements G1 to G30 constituting the projection optical system PL are made to be as-surfaced, so that the light source output is reduced. An amount of on-axis astigmatism and anisotropic distortion that can cancel out the on-axis astigmatism and anisotropic distortion caused by the change can be generated in advance. [Second Embodiment] A projection optical system PL according to a second embodiment shown in FIG. 7 includes a plurality of lens elements G1 to G30 constituting the projection optical system PL having the lens data shown in Table 1 above. Four lens elements (G1, G2, G17, G1
8) Four lens surfaces (G1R2, G2R1, G17R)
, G18R1) has a shape having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction, and the lens element G17 and the lens element G18 are relatively rotatable about the optical axis, so that the on-axis non-axial The amount of astigmatism can be adjusted, and the lens element G1 and the lens element G2 can be relatively rotated about the optical axis to adjust the amount of anisotropic distortion.

In the second embodiment, similarly to the first embodiment, the lens elements G2 and G4 to
G6 is controlled by the piezo element driving units PD1 and PD2 and moves independently along the optical axis direction, and is interposed between the lens element G11 and the lens element G15 and between the lens element G20 and the lens element G26. Space
The airtight chambers AM1 and AM2 are sealed from the outside air, and the pressure inside them is controlled by a pressure control unit (not shown).

In the projection optical system PL shown in FIG. 7, a pair of lens elements G1 and G2 arranged closest to the reticle among the plurality of lens elements G1 to G30 are arranged in a predetermined meridian direction and the meridian direction. It has lens surfaces G1R2 and G2R1 having shapes having different powers in orthogonal directions. Here, the lens surface G1R2 is the lens surface of the lens element G1 on the wafer side, and the lens surface G2R1 is the lens surface of the lens element G2 on the reticle side. In this way, a set of lens surfaces which are astigmatically formed (lens surfaces having different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction) are arranged to face each other.

Each of these lens surfaces G1R2 and G2R1 has a strong principal meridian in which the radius of curvature (refractive power) becomes the strongest and a weak principal meridian in which the radius of curvature (refractive power) becomes the weakest. The strong and weak main meridians are orthogonal to each other. In these lens elements G1 and G2, the amount of anisotropic distortion can be adjusted by changing the angle between the strong main meridians (weak main meridians). Here, when the strong main meridians (weak main meridians) are orthogonal to each other, the amount of anisotropic distortion is minimized, and the strong main meridians (weak main meridians) are parallel to each other. In some cases, the amount of anisotropic distortion is maximized. In this embodiment, when the strong main meridians (weak main meridians) are orthogonal to each other, no anisotropic distortion occurs.

In the projection optical system PL of FIG. 7, a pair of lens elements G17, G17, which are arranged near the aperture stop AS (near the pupil plane) among the plurality of lens elements G1 to G30.
G18 has a lens surface G17R2 having a different power in a predetermined meridian direction and a direction orthogonal to the meridian direction.
G18R1. Here, the lens surface G17R2 is the lens surface of the lens element G17 on the wafer W side, and the lens surface G18R1 is the lens surface of the lens element G18 on the reticle side. As described above, another set of lens surfaces that are formed into a different surface from the set of lens surfaces that are formed into a different surface is disposed so as to face each other.

These lens surfaces G17R2, G18R1
Has a strong principal meridian in which the radius of curvature (refractive power) is the strongest, and a weak principal meridian in which the radius of curvature (refractive power) is the weakest. Are orthogonal to each other. These lens elements G17,
In G18, by changing the angle between the strong main meridians (weak main meridians), the amount of on-axis astigmatism can be adjusted. Here, when the strong main meridians (weak main meridians) are orthogonal to each other, the amount of on-axis astigmatism is minimized, and the strong main meridians (weak main meridians) are parallel to each other. In some cases, the amount of on-axis astigmatism is maximized. In this embodiment, when the strong main meridians (weak main meridians) are orthogonal to each other, no axial astigmatism occurs.

In the projection optical system PL of the second embodiment, of the aberrations generated when the intensity of the lamp is changed, the isotropic aberration components include the movement of the lens elements G2, G4 to G6 in the optical axis direction, The pressure in the airtight chambers AM1 and AM2 is corrected by increasing or decreasing the pressure, and the anisotropic aberration components (on-axis astigmatism and anisotropic distortion) are corrected by the lens element G.
The rotation can be corrected by the rotation of at least one of the optical axes of the lens elements G1 and G2 and the rotation of the lens elements G17 and G18 about at least one of the optical axes. In the second embodiment as well, since the isotropic aberration component can be corrected by another method, the lens surfaces G1R2, G2R1, G
The correction amount of anisotropic components (axial astigmatism, anisotropic distortion) corrected by 17R2 and G18R1 can be reduced as much as possible.

In the projection optical system PL of the second embodiment, the lens data of the predetermined meridional section is as shown in Table 1 above, and Table 3 below shows the lens surfaces G1R2, G2R1, and G17.
9 shows surface shape data of R2 and G18R1. In Table 2 below, Rx is the radius of curvature of the lens surface in a predetermined meridian direction (strong principal meridian), and Ry is the radius of curvature of the lens surface in a direction orthogonal to the meridian direction (weak principal meridian). .

[0044]

Table 3 [Second embodiment] G1R1 (second surface) Rx = 304.17256 (strong main meridian) Ry = 304.17907 (weak main meridian) G2R1 (third surface) Rx = 1800.12100 (strong main meridian) Ry = 1799.90090 ( Weak main meridian) G17R2 (34th plane) Rx = 216.44577 (strong main meridian) Ry = 216.44399 (weak main meridian) G18R1 (35th plane) Rx = -126.36825 (strong main meridian) Ry = -126.36874 (weak main meridian) In the second embodiment, when the lens elements G1 and G2 are arranged such that the strong principal meridian of the lens surface G1R2 and the strong principal meridian of the lens surface G2R1 are at 90 degrees to each other, anisotropically on the image plane No distortion occurs. Also,
When the strong principal meridian of the lens surface G1R2 and the strong principal meridian of the lens surface G2R1 are parallel to each other, the direction of the strong principal meridian and the weak principal meridian at the position of the maximum image height Y = 13.2 mm on the image plane. +0.010 μm (−0.010 μm)
μm) of anisotropic distortion.

In the second embodiment, the lens surface G1
When the lens elements G17 and G18 are arranged such that the strong principal meridian of 7R2 and the strong principal meridian of the lens surface G18R1 are at 90 degrees to each other, no axial astigmatism occurs on the optical axis on the image plane. When the strong principal meridian of the lens surface G17R2 and the strong principal meridian of the lens surface G18R1 are parallel to each other, at a point on the optical axis on the image plane, the image plane along the direction of the strong principal meridian and the weak principal meridian. On-axis astigmatism of 0.46 μm occurs between the image plane along the meridian direction.

These values are obtained when the units of the radius of curvature and the surface spacing in Tables 1 and 3 are mm. Thus, in the second embodiment, the projection optical system PL
Of the plurality of lens elements G1 to G30 (G1R2, G2R1, G17R2, G18
R1) is assimilated and each set (G1R2, G2R)
1 and the set of G17R2 and G18R1) so as to be relatively rotatable about the optical axis to cancel axial astigmatism and anisotropic distortion caused when the light source output is changed. A possible amount of axial astigmatism and anisotropic distortion can be generated. Further, in the second embodiment,
Since the amount of on-axis astigmatism and anisotropic distortion can be adjusted, the projection optical system P
L can correspond.

In the above embodiment, the projection optical system PL
Although the description has been made by taking as an example a refractive projection optical system in which all the optical elements constituting the lens element are lens elements, the present invention is applicable not only to a refractive projection optical system but also to a catadioptric projection optical system and a reflective projection optical system. Applicable. Further, in the above-described embodiment, the lens element is made to be aspered, but a reflective element may be used instead.

In the second embodiment, even when the amount of axial astigmatism and the amount of anisotropic distortion changes with time due to heat absorption of the projection optical system PL, the axial astigmatism does not change. Since the amount of anisotropic distortion and the amount of anisotropic distortion can be controlled, these can be effectively corrected. At this time,
A method of actually measuring the aberration of the projection optical system PL and adjusting the rotation of each of the lens elements G1, G2, G17, and G18 according to the measurement result, and the time required for the exposure light to pass through the projection optical system PL. By measuring, this time and each lens element G1,
A method of referring to a map in which the relationship between the rotation amounts of G2, G17, and G18 is stored can be considered.

In the above-described embodiment, the i-line of the mercury lamp is used as the light source, but the light source is not limited to the mercury lamp.

[0050]

As described above, according to the present invention, the throughput is improved under a good imaging condition, particularly under a condition in which axial astigmatism and anisotropic distortion are well corrected. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a diagram for explaining the principle of the present invention.

FIG. 3 is a diagram for explaining the principle of the present invention.

FIG. 4 is a diagram showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 5 is a sectional view of a lens of a projection optical system according to a first embodiment of the present invention.

FIG. 6 is a diagram for explaining anisotropic distortion.

FIG. 7 is a lens sectional view of a projection optical system according to a second embodiment of the present invention.

FIG. 8 is a diagram showing an exposure area of the projection optical system.

FIG. 9 is a diagram for explaining a problem of the present invention.

FIG. 10 is a diagram for explaining a problem of the present invention.

FIG. 11 is a diagram for explaining a problem of the present invention.

[Explanation of symbols]

 PL: projection optical system R: reticle (mask) W: wafer (substrate)

Claims (3)

[Claims] An image of a pattern provided on a projection original is formed on a substrate by using a projection optical system, and a positional relationship between the substrate and the projection optical system is relatively changed along a scanning direction. In a scanning projection exposure apparatus that performs projection exposure while performing projection, the projection optical system forms an image in a region having an anisotropic shape, and at least one of optical surfaces of optical members constituting the projection optical system The two surfaces have different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction, and the shapes of the at least two optical surfaces are at least anisotropic distortion and astigmatism on the optical axis. A scanning projection exposure apparatus having a shape capable of correcting a gap. 2. The optical system according to claim 1, wherein at least four of the optical surfaces of the optical member constituting the projection optical system have different powers in a predetermined meridian direction and a direction orthogonal to the meridian direction. 2. The scanning projection exposure apparatus according to claim 1, wherein an optical surface of the surface is rotatable about an optical axis of the projection optical system. 3. The shape of two optical surfaces of the at least four optical surfaces is a shape that can adjust at least the amount of anisotropic distortion generated by rotating the optical surfaces. The two optical surfaces different from the two optical surfaces out of the two optical surfaces have a shape that can adjust at least the amount of astigmatic difference on the optical axis by rotating the optical surfaces. The scanning projection exposure apparatus according to claim 2, wherein: