JP2000066075A - Optical system and its production and exposure device equipped with the optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system equipped with plural optical members and capable of obtaining high optical characteristic (image-formation performance or the like). SOLUTION: The image of the pattern of a reticle 12 is projected and exposed to a wafer 14 through a projection optical system having lenses 3A and 3B. Assuming that the lenses 3A and 3B are held by three-point supporting system holding members 4A and 4B, after the deformation amount of the respective lenses in the case of holding the lenses by members 4A and 4B is obtained (1st stage), the residual aberration of the projection optical system due to the deformation amount is obtained (2nd stage). Then, the rotational angles of the members 4A and 4B are optimized so that the residual aberration may be small (3rd stage) and the rotational angles of the members 4A and 4B in the projection optical system 1 are adjusted to the rotational angles optimized in such a way (4th stage).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical system having a plurality of optical members and a method of manufacturing the same, for example, a projection exposure apparatus used in a lithography process for manufacturing a semiconductor element or a liquid crystal display element. It is suitable for use in a provided projection optical system or the like.

[0002]

2. Description of the Related Art A reticle as a mask is used in a batch exposure type projection exposure apparatus such as a stepper used for manufacturing a semiconductor device or the like, or a scanning exposure type projection exposure apparatus such as a step-and-scan method. Is provided with a projection optical system for transferring an image of the pattern formed on a wafer (or a glass plate or the like) coated with a photosensitive material as a substrate. As the degree of integration of semiconductor elements and the like increases, the imaging performance such as resolution and distortion required for the projection optical system has become extremely high. For this reason, optical members such as various lenses that constitute the projection optical system are manufactured with extremely high accuracy, and the holding members that hold those optical members are also manufactured with high accuracy. Further, the conventional holding member is generally shaped to support the entire circumference of the optical member.

FIG. 22A is a perspective view showing a state where a disk-shaped lens 41 as a conventional optical member and a thin cylindrical holding member 42 for holding the lens 41 are separated.
2 (b) is a plan view showing the holding member 42, and FIG. 22 (c) is an enlarged view of a portion C in FIG. 22 (b). First, FIG.
As shown in (a), a support portion 42a formed of a flange-shaped convex portion is formed on the entire circumference of the inner surface of the holding member 42.
When the lens 41 is mounted on the inner surface of the holding member 42, as shown by hatching in FIGS. 22 (b) and (c),
The ring-shaped area on the upper surface of the support portion 42a is
It was configured to support.

[0004]

As described above, the conventional lens holding member 42 is configured to support the outer peripheral portion of the lens 41 all around. However, in most cases, the holding member 42 is actually in contact with the lens 41 only on a part of the entire circumference of the support portion 42a. Further, since the contact position is unstable, the contact The position could change slightly. Thus, the holding member 42
When the contact position between the lens 41 and the lens 41 changes, the attitude and the like of the lens 41 slightly change, so that the imaging performance of the projection optical system changes, and the resolution of the image transferred onto the wafer decreases and the position shifts. And the like. Particularly, in recent years, projection optical systems are required to have a large numerical aperture in order to achieve higher resolution. Therefore, since each optical member constituting the projection optical system is also large, the posture of each optical member and the like are changed. The amount of change is also increasing, and its adverse effect on imaging performance is also increasing.

On the other hand, in order to eliminate the instability of the contact position between the holding member and the lens, a supporting point composed of a plurality of projections is provided on the inner surface of the holding member, and the plurality of supporting points are provided. A configuration in which the lens is supported at a support point is also conceivable. However, especially when the lens becomes large, the lens is locally deformed mainly between its supporting points mainly due to its own weight, so that measures to reduce the adverse effect of the deformation of the lens on the imaging performance are taken. It is desirable to apply.

Further, when a plurality of such holding members are provided, the imaging performance may be changed by local deformation of each lens by a plurality of supporting points of the plurality of holding members. It is desired to establish a method of assembling and adjusting the projection optical system for obtaining high imaging performance, that is, a method of manufacturing. In view of the above, it is a first object of the present invention to provide an optical system including a plurality of optical members and obtaining high optical characteristics (such as imaging performance).

It is a second object of the present invention to provide an optical system which includes a plurality of optical members and which can easily be assembled and adjusted and has stable optical characteristics. Furthermore, the present invention
A third object is to provide a method of manufacturing an optical system that can assemble such an optical system so as to exhibit high optical characteristics without performing complicated assembly adjustment.

A further object of the present invention is to provide an exposure apparatus having such an optical system and capable of transferring a reticle pattern image onto a wafer with high accuracy.

[0009]

According to a first optical system of the present invention, there is provided an optical system having a plurality of optical members (3A, 3B), wherein a plurality of optical members are supported at a plurality of support points, respectively. Holding members (4A, 4B) are provided, and a plurality of support points (4Aa to 4A) of these plurality of holding members are provided.
c, 4Ba to 4Bc), so as to reduce the residual aberration of the optical system caused by the deformation of the corresponding optical member (3A, 3B).
A, 4B) in which at least one rotation angle is adjusted.

According to the present invention, in order to hold a plurality of optical members, instead of holding members supporting each optical member all around, each optical member (3) is provided at a plurality of support points in the entire circumference.
Since the holding members (4A, 4B) that support the optical members (A, 3B) are used, each optical member is held extremely stably.
However, when the optical member is supported at a plurality of support points as described above, particularly when the size of the optical member is increased, deformation of the optical member due to its own weight occurs between the support points, and this deformation is caused by the deformation of the optical system. May deteriorate the optical characteristics (imaging performance when the optical system is a projection optical system).

Accordingly, in the present invention, the residual aberration of the entire optical system generated as a result of the deformation of each optical member caused by being supported at a plurality of support points is reduced so that At least one rotation angle is adjusted (set). In this case, in order to reduce the residual aberration of the entire optical system caused by the deformation of each optical member due to the support of the plurality of support points, the amount of deformation of each optical member caused by the support of the plurality of support points of each optical member is required. Preferably, the rotation angle of at least one of the plurality of optical members is adjusted (set) based on each of them. Further, it is even more preferable that the rotation angles of the plurality of optical members are respectively adjusted (set).

[0012] In this case, it is desirable to previously calculate the amount of deformation of each optical member between each support point of each holding member, for example, by calculation or measurement in advance. In this sense, each holding member of the present invention only needs to have a holding form in which the deformed shape of each held optical member can be calculated. Also, for example, since the amount of deformation of each optical member has a direction depending on the direction of each support point, for example, the residual aberration of the optical system caused by the deformation of each optical member by calculation or measurement (actual measurement) The rotation angles of the plurality of optical members around the optical axis of the optical system for minimizing the optical members are determined. By setting each rotation angle of a plurality of optical members (holding members) with this rotation angle as a target value, high optical characteristics can be obtained. Further, in addition to the deformation between the plurality of support points, the deformation of each optical member due to the support at the plurality of support points, including the local deformation of each optical member at the position of each support point, etc. It is more desirable to consider

Next, in a second optical system according to the present invention, in an optical system having a plurality of optical members (3A to 3C), a plurality of holding members (3A to 3C) supporting the plurality of optical members at a plurality of support points, respectively. 4A to 4C), the plurality of supporting points of the plurality of holding members are arranged at equal angular intervals with the same number, and the plurality of supporting points (4Aa to 4Ac, 4Ba) of the plurality of holding members are provided. ~ 4Bc, 4Ca
4Cc) is substantially the same direction (the state of FIG. 7A), or is adjacent to an intermediate position between two support points (4Aa, 4Ab) of the first holding member (4A). Second
The relative rotation angle between the plurality of holding members (4B) is set such that one support point (4Ba) of the holding member (4B) is located (the state of FIG. 7B).

In the present invention as well, the plurality of optical members are stably supported by the holding members each having a plurality of support points. By setting the directions of the plurality of support points of each holding member to be substantially the same or to be set alternately, the optical system is assembled in a form in which the optical characteristics are stable and reproducibility is obtained. At this time, whether the plurality of support points are set in substantially the same direction or alternately set may be selected, for example, so that the residual aberration becomes smaller.

Next, in the first method for manufacturing an optical system according to the present invention, a plurality of optical members (3A, 3B) and a plurality of supporting points (4Aa to 4Ac, 4
Ba to 4Bc) and a plurality of holding members (4A, 4B)
B), comprising: a first step of obtaining a deformation amount occurring in a corresponding one of the plurality of optical members between a plurality of supporting points of the plurality of optical members; and a plurality of the optical members. A second step of determining the residual aberration of the optical system caused by the deformation between the plurality of support points, and focusing on the optical axis of the optical system to reduce the residual aberration calculated in this way. A third step of obtaining at least one rotation angle of the plurality of holding members, and at least one of the plurality of rotation members of the plurality of holding members in the optical system based on the rotation angle calculated in the third step. And a fourth step of adjusting the angle.

According to such a manufacturing method, in the first step,
For example, the amount of deformation due to a plurality of supporting points is calculated for each optical member by computer simulation, or the amount of deformation due to the plurality of supporting points is actually measured. In the second step, for example, a computer simulation is used to calculate residual aberration of the optical system caused by the amount of deformation of the plurality of support points for each optical member, or to calculate the amount of deformation due to the amount of deformation of the plurality of support points. The residual aberration of the optical system that is generated is actually measured. Based on the amount of deformation of each optical member due to the plurality of support points obtained in the first and second steps and the amount of residual aberration of the entire optical system, in the third step, a plurality of At least one rotation angle is determined, and based on the result, at least one rotation angle of the plurality of holding members is appropriately set in the fourth step.

That is, obtaining the amounts of deformation of the plurality of optical members at the plurality of supporting points in the first step and obtaining the residual aberration of the entire optical system in the second step are performed by calculations such as computer simulations. It may be a calculation or an actual measurement. In addition, it is preferable that the obtaining of the rotation angle of at least one of the plurality of holding members in the third step is, for example, a calculation by a computer simulation or the like.

Further, in the second method of manufacturing an optical system according to the present invention, a plurality of optical members (3A, 3B) and a plurality of supporting points (4Aa to 4Ac, 4
Ba to 4Bc) and a plurality of holding members (4A, 4B)
B), comprising: a first step of determining a residual aberration of the optical system caused by a deformation between the plurality of support points of the plurality of optical members;
A second step of obtaining at least one rotation angle of a plurality of holding members about the optical axis of the optical system for reducing the residual aberration thus obtained, and a second step of obtaining the rotation angle. Adjusting a rotation angle of at least one of the plurality of holding members in the optical system based on the rotation angle.

According to such a manufacturing method, in the first step,
For example, by computer simulation, the residual aberration of the optical system caused by the deformation by the plurality of support points for each optical member is calculated, or the residual aberration of the optical system caused by the deformation by the plurality of support points Is actually measured. Then, at least one rotation angle of the plurality of holding members is determined in the second step based on the residual aberration amount of the optical system determined in the first step, and based on the result, the third step is performed. The rotation angle of at least one of the plurality of holding members is appropriately set.

That is, the determination of the residual aberration of the optical system in the first step may be a calculation by a computer simulation or the like or an actual measurement. In addition, it is desirable that the calculation of the rotation angle of at least one of the plurality of holding members in the second step is performed by a calculation such as a computer simulation.

Next, an exposure apparatus according to the present invention comprises an optical system (1) according to the present invention, a mask stage (13) for holding a mask (12), and a substrate stage (15) for holding a substrate (14). , Wherein the optical system is used as a projection optical system for projecting an image of the pattern of the mask onto the substrate. According to such an exposure apparatus, the imaging performance of the projection optical system is maintained stably and with high accuracy.

The present invention is not limited to the above-described first to fifth aspects, but may be configured as described in the following (1) or (2). (1) That is, a third method for manufacturing an optical system according to the present invention is a method for manufacturing an optical system having a plurality of optical members and a plurality of holding members each supporting the optical members at a plurality of support points. A first step of obtaining, for each optical member, an amount of deformation caused by the holding member supporting the optical member corresponding to the holding member at a plurality of support points; A second step of determining at least one rotation angle of the plurality of optical members to correct a residual aberration of the optical system caused by being supported by the support point; and a rotation angle determined in the second step. On the basis of,
Adjusting a rotation angle of at least one of the plurality of optical members.

(2) In the exposure method according to the present invention, the step of providing the optical system according to any one of claims 1 and 2 or the above (1), and setting a mask on the object plane of the optical system. A step of setting a photosensitive substrate on an image plane of the optical system, a step of illuminating the mask, and a step of exposing a pattern image of the mask to the photosensitive substrate by the optical system. .

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. In this example, the optical system of the present invention is applied to a projection optical system provided in a projection exposure apparatus. FIG.
1 shows a main part of the projection exposure apparatus of the present embodiment. In FIG. 1, after being emitted from an exposure light source (not shown), a shaping optical system,
Exposure illumination light IL that has passed through an optical integrator, a condenser lens, a field stop, and the like illuminates a pattern surface of a reticle 12 as a mask via a main condenser lens 11. As the illumination light IL, i-line of a mercury lamp (wavelength 365 nm), KrF (wavelength 248 nm)
Or ArF (wavelength 193 nm) excimer laser light such, F ₂ laser beam (wavelength 157 nm), etc. can be used.
Under the illumination light IL, an image of the pattern of the reticle 12 is projected through the projection optical system 1 to a projection magnification β (β is, for example, 1/4, 1
/ 5), the surface of a wafer (wafer) 14 coated with a resist as a substrate is projected and exposed. The projection optical system 1 corresponds to the optical system of the present invention.

That is, the exposure of the reticle pattern onto the wafer using the projection optical system 1 includes the steps of setting a reticle (mask) 12 on the object plane of the projection optical system 1 and setting the wafer on the image plane of the projection optical system 1. This is achieved by a step including a step of setting a (photosensitive substrate) 14, a step of illuminating the reticle 12 with the illumination light IL, and a step of exposing a pattern image of the reticle to the wafer 14 by the projection optical system 1.

In this case, the reticle 12 and the wafer 14
Are held by suction on a reticle stage 13 and a wafer stage 15, respectively. The reticle stage 13 positions the reticle 12 in a plane perpendicular to the optical axis AX of the projection optical system 1, and the wafer stage 15
The wafer 14 is moved and positioned in a plane perpendicular to the optical axis AX, and the wafer 14 is auto-focused so that exposure is performed with the surface of the wafer 14 aligned with the image plane of the projection optical system 1. Is controlled in the direction parallel to the optical axis AX (focus position). At the time of exposure, when the exposure of one shot area on the wafer 14 is completed, the next shot area is moved to the exposure area of the projection optical system 1 by the step movement of the wafer stage 15, and the exposure of the pattern image of the reticle 12 is performed. Is repeated in a step-and-repeat manner. As described above, the projection exposure apparatus of the present embodiment is a batch exposure type, but it goes without saying that the optical system of the present invention can be applied to the projection optical system of a scanning exposure type projection exposure apparatus such as a step-and-scan method. Not even.

Next, a method of holding the optical members constituting the projection optical system 1 of this embodiment will be described in detail. Projection optical system 1
Are two axially symmetric lenses 3A and 3B as optical members,
And other lenses, aberration correction plates and the like (not shown). The lenses 3A and 3B are housed in holding members 4A and 4B as cylindrical lens frames, respectively.
The holding members 4A and 4B are accommodated in the lens barrel 2 of the projection optical system 1, and the rotation angles of the holding members 4A and 4B around the optical axis AX are adjusted to a predetermined angle and fixed. The optical axis AX is provided between the holding members 4A and 4B and above and below the holding members 4A and 4B.
Ring-shaped spacers 6A to adjust the spacing in the direction
6C is arranged, and the lenses 3A and 3B are
The holding members 4A and 4B are fixed in the holding members 4A and 4B with a force that does not deform the holding rings 5A and 5B, respectively. Although not shown, holding members 4A, 4B
In addition, a plurality of holding members each containing a lens are arranged. Further, the optical axis A of the projection optical system 1 of the present embodiment
Since X extends in the vertical direction and the lenses 4A and 4B are urged downward by their own weight, it is not always necessary to use the holding rings 5A and 5B.

FIG. 2 shows one of the lenses 3A as a holding member 4A.
In FIG. 2, the lens 3A has an axially symmetric disk shape having a maximum diameter of dA.
The inner surface 4Ad of the holding member 4A is a cylindrical surface whose inner diameter is slightly larger than dA, and is equiangularly spaced (1
Support points 4Aa to 4A consisting of three convex portions at 20 ° intervals)
c is formed. In this case, the support points 4Aa to 4Ac
Is the same metal (iron, stainless steel, brass, etc.) as the holding member 4A, and the shape including the thickness and height of the supporting points 4Aa to 4Ac is such that the supporting points 4Aa to 4Ac are not easily deformed by the weight of the lens 3A. It is set to have great rigidity. In general, an object is stably supported by determining the positions of three points, and therefore, three support points 4Aa to 4Aa to
By providing 4Ac, the lens 3A can be stably supported, and, for example, by performing a simulation using a computer, each of the support points 4Aa to 4Aa to
There is an advantage that the amount of deformation of the lens 3A due to its own weight between 4Ac can be accurately calculated. The other holding member 4B
Similarly, three support points 4Ba to 4 arranged at equal angular intervals
4Bc (see FIG. 4).

However, the support points may be set at a plurality of points, for example, four points, five points, six points, and the like. If the number of support points is four or more, any of the support points will not come into contact with the lens when the support points and the lens do not deform at all. As a result, all the support points come into contact with the lens, and the lens is almost stably supported. In addition, since the positions of the plurality of support points are accurately known, the amount of deformation of the lens between the support points can be accurately calculated.

The pressing ring 5A has a thin ring shape having an outer diameter that can be accommodated in the inner surface 4Ad of the holding member 4A, and is formed on the bottom surface of the pressing ring 5A by three convex portions at equal angular intervals (120 ° intervals). Pressing parts 5Aa to 5Ac are formed,
A slot 5Ad for rotating the holding ring 5A is formed on the upper surface of the holding ring 5A. Actually, screw portions that screw together are formed on the outer surface of the holding ring 5A and a part of the inner surface of the holding member 4A.
(C)). When the lens 3A is housed inside the holding member 4A via the holding ring 5A, the holding ring 5A is placed above the support points 4Aa to 4Ac of the holding member 4A.
The rotation angle of the holding ring 5A is set so that the holding portions 5Aa to 5Ac are located. Presser ring 5A
By setting the rotation angles of the support points 4Aa to 4A
Since it is not necessary to consider that the lens 3A is deformed by a force other than its own weight during the period c, calculation of the deformation amount of the lens 3A described later can be performed with higher accuracy. When the number of support points of the holding member 4A is four or more, the number and arrangement of the pressing portions of the pressing ring 5A are set in accordance with the supporting points.

FIG. 3A shows that the lens 3 is provided in the holding member 4A.
A is stored (however, the holding ring 5A is not shown).
3 (b) is an enlarged view of a portion B in FIG. 3 (a), FIG. 3 (c) is an enlarged sectional view taken along the line AA in FIG. 3 (a), and the lens 3A is a support point. On the 4Ab, it is supported in the area shown by hatching in FIG. 3B, and the other support points 4Aa,
It is similarly supported on 4Ac. Further, as shown in FIG. 3 (c), the lens 3A is sandwiched and held by the supporting points 4Aa to 4Ac of the holding member 4A and the holding parts 5Aa to 5Ac of the holding ring 5A at three places near the outer peripheral part. I have. For this reason, a screw portion 4Ae is formed on the upper portion of the inner surface of the holding member 4A, and a screw portion 5Ae is formed on the outer peripheral portion of the holding ring 5A so as to correspond thereto, and
Pressing ring 5A is held by holding member 4 by screwing of 5Ae and 5Ae.
A is attached. The holding ring 5A is attached to the holding member 4A in a state in which the lens 3A applies a considerably smaller urging force than the own weight of the lens 3A, and the holding ring 5A is caused to have a play between the screw portions 4Ae and 5Ae. The rotation angle can be adjusted to some extent while the urging force for 3A is kept substantially constant.

In the case of adopting a configuration in which the holding ring 5A is omitted, as shown in FIG. 3D corresponding to FIG. 3C, a thread is formed on the inner surface 4Ad of the holding member 4A. There is no necessity, and the lens 3A is simply supported at the supporting point 4 by its own weight.
It is placed on Aa-4Ac. Then, another holding member 4D (or a spacer or the like) is placed on the holding member 4A.
In particular, the numerical aperture of the projection optical system 1 is large, and the lenses 3A, 3B
Is large and heavy, presser ring 5A,
Even if 5B is omitted, the lenses 3A and 3B are stably held.

As described above, the lenses 3A and 3B as optical members in the projection optical system 1 of this embodiment are
A and 4B are supported by three support points. In such a configuration in which the optical member is supported at a plurality of support points,
Since the contact position between the optical member and the holding member is clear, the amount of deformation of the optical member between the contact positions (support points) can be accurately calculated, and the deformation of the optical member can be calculated based on the result. Is quantitatively calculated on the image forming performance of the projection optical system 1, and the rotation angle of each optical member can be determined such that the deterioration of the image forming performance of the projection optical system 1 is reduced.
Instead of calculating the amount of deformation of the optical member between the support points, the amount of deformation of the optical member can be measured by wavefront interference or the like based on the position of the support point. Therefore, the lenses 3A, 3A,
After calculating or measuring the deformation amount of 3B, the lens 3A,
An example of an operation of setting the rotation angles of the holding members 4A and 4B for housing the 3B to a predetermined angle (optimizing) and housing the 3B in the lens barrel of the projection optical system 1 will be described with reference to FIG.

The holding members 4A, 4A are provided in the projection optical system 1.
If there is a holding member that holds the optical member at a plurality of support points in addition to B, the rotation angle of the holding member is also optimized in the same manner. FIG. 4 shows a part of the manufacturing process of the projection optical system 1 for projecting the image of the reticle 12 on the wafer 14. First, FIG. 4A shows the lenses 3A and 3B at the initial rotation angle before adjustment. 3 shows a state of deformation. That is, in FIG. 4A, the lens 3A is supported by the support points 4Aa to 4Ac of the holding member 4A, and the lens 3B is supported by the support points 4Ba to 4Bc of the holding member 4B. In the initial state, the support points 4Ac, 4
The rotation angles of the holding members 4A and 4B are set such that Bc comes forward (overlaps in the rotation direction). In this example, the lens 3A has a very small amount of deformation at points A, B, and C above the support points 4Aa, 4Ac, and 4Ab, but has an unsupported point D at an intermediate position between the support points 4Ab, 4Aa, and 4Ac. , E and F are deformed vertically downward by their own weight. Furthermore, since the center point G of the lens 3A is not supported by the holding member, it is deformed vertically downward. Similarly, in the lens 3B, the support points 4Ba,
Deformation hardly occurs at points H, I, and J on 4Bc and 4Bb, but the points K, L, M, and N in the middle (including the center) of the supporting points 4Ba, 4Ba, and 4Bc are deformed downward by their own weights. Has occurred. Although these deformation amounts are actually small amounts on the order of the wavelength of visible light, they are exaggerated in FIG.

Such deformation of the lenses 3A and 3B affects the imaging performance of the projection optical system 1. Then, as described below, the lenses 3A, 3B (that is, the holding members 4A, 4
Optimize the rotation angle of B). [First Step] In a first step ST1 of FIG. 4, the amount of deformation of the lenses 3A and 3B as optical members is calculated or measured. The calculation of the deformation amount is performed by the holding member 4 of the lenses 3A and 3B.
A, 4B (support points 4Aa to 4Ac, 4B
a to 4Bc can be made by structural analysis. The structural analysis in this case is, for example, the lens 3
Finite element method analysis using a computer, taking in information such as the shape of A and 3B, the constraint conditions depending on the support mode (there is almost no deformation at the support point, etc.), the Young's modulus, density, Poisson's ratio, etc. of the lens and holding member materials This is performed by calculating the distribution of the amount of deflection due to its own weight at each position other than the support point.

In order to measure the amount of deformation of the lenses 3A and 3B, each surface of the lens may be compared with a reference surface by performing, for example, interference measurement. Hereinafter, a method of measuring the deformation state of one surface of the lens 3B using a Fizeau interferometer will be briefly described. FIG. 5 shows an example of a Fizeau-type interferometer for measuring the shape of the surface of an optical member. In FIG. 5, a laser beam 25 emitted from a laser light source 16 is transmitted through a lens 17 to a beam splitter 18.
Incident on. The laser light source 16 has an oscillation wavelength of 633.
nm He-Ne laser, an Ar laser having an oscillation wavelength of 363 nm, a harmonic generator for converting Ar laser light to a wavelength of 248 nm, or the like can be used.

The laser beam 25 reflected by the beam splitter 18 is converted into a parallel light beam by a collimator lens 19, and the parallel light beam is
Then, the light is incident on a test surface (lens surface) S2 on the upper side of a lens 3B as a test object supported at three points by the holding member 4B. In this case, a reference surface S1 having a slight reflectance is formed on the condenser lens 20, a part of the laser beam 25 is reflected by the reference surface S1 of the condenser lens 20, and the remaining laser beam is collected. The light passes through the lens 20 and is reflected by the test surface S2 of the lens 3B. Holding member 4 for housing lens 3B
B is installed in a state where it is actually installed in the projection optical system 1.

The laser beam reflected on the test surface S2 is returned to the condenser lens 20, and is superimposed on the laser beam reflected on the reference surface S1. The two laser beams thus superimposed return to the beam splitter 18 via the condenser lens 20 and the collimator lens 19, and the laser beam transmitted through the beam splitter 18 is
Interference fringes of the laser beam from the test surface S2 and the reference surface S1 are formed on the imaging surface of an imaging device 22 such as a CCD type via the imaging lens 21. An image signal from the image sensor 22 is supplied to an image processing device (not shown). Information on the shape of the reference surface S1 and information on the shape of the two surfaces of the lens 3B before deformation (on the design data) are input to the image processing device. The obtained interference fringes are analyzed to obtain the distribution of the deformation amount of the shape of the test surface S2 (or the shape of the test surface S2 after the deformation). Similarly, FIG.
The distribution of the amount of deformation of the upper surface (test surface) of the lens 3A housed in the holding member 4A, or the shape after the deformation, is also calculated or measured.

The technique for obtaining the shape of the surface (lens surface) of an optical member such as a lens using a Fizeau interferometer is described in, for example, JP-A-6-126305 and JP-A-6-185997. Are also disclosed. In this example, since the holding members 4A and 4B hold the lenses 3A and 3B at a plurality of support points, the lenses 3A and 3B deform in a simple manner. Therefore, it is easy to calculate the amount of deformation of the lenses 3A and 3B, and it is also possible to measure the amount of deformation with high reproducibility.

[Second Step] In the second step ST2, calculation or measurement of the residual aberration (residual aberration) of the projection optical system 1 caused by the deformation of the lenses 3A and 3B obtained in the first step ST1 is performed. Do. The former calculation of the residual aberration can be performed by, for example, performing an optical simulation. That is, reproduction is performed based on information such as the radius of curvature (or aspherical coefficient in the case of an aspherical lens), the center thickness, the refractive index, and the air gap between the optical members of each optical member constituting the projection optical system 1. The first step ST1
By giving the data of the deformation amounts of the plurality of optical members (lenses 3A and 3B) obtained in step (1) and performing ray tracing or the like using a computer, the residual projection optical system 1 caused by the deformation of the predetermined optical members The amount of aberration can be calculated.

On the other hand, the latter measurement of the residual aberration becomes possible by measuring the wavefront aberration of the projection optical system 1, for example. Here, a method of measuring the wavefront aberration of the projection optical system 1 using the same Fizeau interferometer as in the example of FIG. 5 as in the case of the surface measurement of the optical member will be briefly described. FIG. 6 shows an example of a Fizeau-type interferometer for measuring the wavefront aberration of the projection optical system 1. In FIG. 6, the portions corresponding to FIG. However, as the laser light source 16 in FIG. 6, the illumination light I of the projection exposure apparatus in FIG.
A laser light source that emits light having the same wavelength as L (exposure wavelength) or a wavelength very close to this exposure wavelength is used. Then, the laser beam 25 emitted from the laser light source 16
Is a condenser lens 20 having a reference surface S1 from the lens 17.
, The pinhole plate 23 arranged on the object plane of the projection optical system 1 (corresponding to the pattern plane of the reticle 12 in FIG. 1)
Optical system 1 as an object to be examined
And the laser beam having passed through the projection optical system 1 enters the spherical mirror 24. The inner surface of the spherical mirror 24 is the projection optical system 1
On the image plane 26 conjugate with the object plane, a reflection surface S3 is formed as a spherical surface having a position conjugate with the above-mentioned pinhole as a polar center.

The laser beam reflected by the reflecting surface S3 returns to the condenser lens 20 via the projection optical system 1 and the pinhole plate 23, and is superimposed on the laser beam reflected by the reference surface S1. The two laser beams superimposed in this way are transmitted from the condenser lens 20 to the imaging lens 21.
Then, an interference fringe of the laser beam from the reflection surface S3 and the reference surface S1 is formed on the imaging surface of the imaging element 22 via. By processing the image signal from the image sensor 22 by an image processing device (not shown), the wavefront aberration of the projection optical system 1 is accurately obtained as the residual aberration.

At this time, the projection optical system 1 of this embodiment is held in substantially the same situation as the situation where it is actually mounted on the projection exposure apparatus of FIG. As a result, the residual aberration of the projection optical system 1 in a state of being mounted on the projection exposure apparatus is accurately measured. The residual aberration of the projection optical system 1 is measured by using a test reticle having a pattern suitable for aberration detection, in addition to the method of measuring the wavefront aberration using an interferometer as described above. By projecting the image (aerial image) on the image plane through the projection optical system 1 and scanning the aerial image with, for example, a photoelectric sensor having a slit, thereby measuring the position and contrast of the image. Can also be done. Thus, in the method using the test reticle, spherical aberration, coma,
It is possible to separately measure residuals such as Seidel's five aberrations including astigmatism, curvature of field, and distortion, and other higher-order aberrations as residual aberrations. Also,
The resolution or the like may be measured as the image forming performance of the aerial image of the projection optical system 1.

[Third Step] In the third step ST3, a plurality of lenses having the deformation amounts determined in the first step ST1 that cancel the residual aberration of the projection optical system 1 determined in the second step ST2. Lens 3A, 3B and holding member 4A,
The rotation angle of the 4B projection optical system 1 about the optical axis AX is calculated. That is, in order to reduce the residual aberration of the projection optical system 1 obtained in the second step ST2, the first step S2 is performed.
The projection optical system 1 as a whole is formed by strengthening or weakening the change in the aberration caused by the deformation of the lenses 3A, 3B obtained at T1 between the lenses 3A, 3B.
Holding members 4A and 4B when the residual aberration of
The respective rotation angles of the (lenses 3A, 3B) are determined.
Determining the rotation angle of each holding member in this manner is referred to as “optimization of the rotation angle”, and the rotation angle determined so that the residual aberration of the projection optical system 1 is minimized.
A, 4B is called the optimum rotation angle.

The items evaluated in this optimization are the second step S
Various aberrations (wavefront aberration, Seidel aberration, aerial image characteristics, etc.) calculated or measured at T2, and are well-known optimization methods using an attenuation least squares method (DLS method), a genetic algorithm, or the like. These aberrations are minimized overall. Further, in the optimization, the balance of various aberrations at each position in the exposure area of the projection optical system 1 and the balance of residual aberration for each aberration are taken into consideration, and the aberrations are comprehensively adjusted in the exposure area. It is desirable to optimize the rotation angles of the lenses 3A and 3B so that the residual aberration is reduced as a whole.

[Fourth Step] In the next fourth step ST4 of FIG. 4, a plurality of lenses 3A and 3B are placed in the lens barrel 2 of the projection optical system 1 at the rotation angle optimized in the third step ST3. The stored holding members 4A and 4B are inserted. Alternatively, when the holding members 4A and 4B are already stored in the lens barrel 2,
The rotation angles of the holding members 4A and 4B are adjusted to the optimum rotation angles. By this step, it can be expected that the residual aberration of the projection optical system 1 calculated or measured in the second step ST2 is reduced to the residual aberration optimized in the third step ST3.

FIG. 4B shows the projection optical system 1 in which the rotation angles of the holding members 4A and 4B have been set in the fourth step ST4. In FIG. In order that the supporting point of the member 4B does not overlap in the rotation direction,
That is, the rotation angles of the holding members 4A and 4B are set so that the points A, B and C where the deformation amount of the lens 3A is scarcely overlap the points L, M and K where the deformation amount of the lens 3B is large.

As described above, according to this embodiment, the holding member 4 supporting the lens 3A and the like at the plurality of support points 4Aa to 4Ac and the like.
A and the like, and the rotation angle of the holding member 4A and the like is set so that the residual aberration of the projection optical system 1 is minimized as a whole, so that the image of the pattern of the reticle 12 is transmitted through the projection optical system 1. There is an advantage that the image can be transferred onto the wafer 14 with high accuracy with a small aberration.

When there are other holding members in addition to the holding members 4A and 4B, the rotation angles of these holding members are also optimized. Thus, the plurality of holding members 4
When optimizing the rotation angles of the holding members A and 4B, the rotation angles of predetermined holding members (for example, holding members 4A) are fixed, and the rotation angles of the other holding members 4B and the like are the reference holding members 4A and 4B.
The relative rotation angle with respect to A may be optimized.

The lenses 3A, 3B, etc.
Since the projection optical system 1 is stably supported by the point support method (the same applies to other plural point supports), the projection optical system 1 is not mounted due to vibration or the like when the wafer stage 15 of the projection exposure apparatus in FIG. Even if the column vibrates, the attitude and the like of the lenses 3A and 3B with respect to the lens barrel 2 of the projection optical system 1 do not change. Therefore, high imaging characteristics are always stably maintained.

In the above embodiment, the second step S
At T2, the residual aberration as a whole of the projection optical system 1 is measured once, but instead, the holding members 4A, 4B
While sequentially rotating the (lenses 3A, 3B) around the optical axis AX at a predetermined angle step, the overall wavefront aberration is measured, and the holding members 4A, 4A, when the overall wavefront aberration is minimized. Find the 4B rotation angle,
The rotation angles of the holding members 4A and 4B may be set to the rotation angles thus obtained. According to this method, calculation (or measurement) of the deformation amount in the first step ST1 and calculation for optimizing the rotation angle in the third step ST3 can be omitted. At this time, one holding member 4A is fixed, and the other holding members 4B and the like are gradually rotated to minimize the wavefront aberration as a whole. May be obtained.

Next, another example of the embodiment of the present invention will be described with reference to FIG. In the embodiment of FIG. 4, the rotation angles of the holding members 4A and 4B (lenses 3A and 3B) are optimized. However, when the purpose is to obtain a stable and reproducible imaging characteristic, Even if the relative rotation angle between the plurality of holding members is set to a constant value, a certain effect can be obtained. Thus, in the present embodiment, a description will be given of a projection optical system in which the relative rotation angle between a plurality of holding members is set to a constant state. In FIG. 7, portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 7A shows at least three lenses 3A to 3C as optical members arranged along the optical axis AX.
7 (a), the axially symmetric lenses 3A, 3B, 3C are housed in holding members 4A, 4B, 4C as indicated by two-dot chain lines, respectively. , Three support points 4Aa to 4Ac, 4Ba to 4Bc, and 4Ca to 4C in the holding members 4A, 4B, and 4C, respectively.
c. In this example, the holding member 4A
3C are arranged at equal angular intervals in each of the three support points 4Aa to 4A.
c, 4Ba to 4Bc, and 4Ca to 4Cc are set in the same direction.

In this case, the holding members 4A to 4C are previously
(A) is set and the imaging characteristics (residual aberration and the like) of the projection optical system are measured, and when the projection optical system is actually incorporated into the projection exposure apparatus, the holding members 4A to 4C By setting the rotation angle to the state shown in FIG. 7A, reproducible imaging characteristics can be obtained. In this example, when there are four or more lenses, the directions of the support points of the corresponding four or more holding members are set in the same direction. Also, when the number of support points of each holding member is four or more, the directions of the support points are similarly set in the same direction.

On the other hand, FIG. 7B also shows a lens 3 housed in at least three holding members 4A to 4C.
Although the main part of the projection optical system having A to 3C is shown, in the example of FIG. 7B, the rotation angles of the holding members 4A to 4C are set such that the three support points are alternated. ing. That is, the support points 4Aa to 4A of the first holding member 4A
c at the intermediate position of the second holding member 4B.
4Bc, and the support points 4Cb, 4Cc, 4Cc of the third holding member 4C are located at intermediate positions between these support points 4Ba to 4Bc.
4Ca is located, and as a result, the first holding member 4
The support points of A and the third holding member 4C are in the same direction. Then, even when the number of lenses is four or more, or when the number of support points is four or more, the rotation angle of each holding member is set such that the supporting points of adjacent holding members are staggered. In the example of FIG.
By measuring the imaging characteristics of the projection optical system in advance in the state shown in FIG. 7B, reproducible imaging characteristics can be obtained when the projection optical system is incorporated in a projection exposure apparatus.

The imaging characteristics of the projection optical system are measured with the two arrangements of the rotation angles shown in FIGS. 7A and 7B, and the arrangement of the rotation angles at which a better imaging characteristic is obtained is determined. You may make it select. In the above embodiment, the present invention is applied to a projection optical system composed of a refraction system of a projection exposure apparatus. However, the invention is, for example, a projection optical system composed of a catadioptric system having a concave mirror as an optical member. And soft X
The present invention can be similarly applied to a projection optical system including a reflection system used in an exposure apparatus that uses extreme ultraviolet light (EUV light) such as a line as an exposure beam. Since the projection optical system composed of the latter reflection system uses several reflecting mirrors, even if all of them are held by a holding member having a plurality of support points, the analysis is relatively easy. is there. Further, the present invention can be applied to, for example, a case where a predetermined optical member of an illumination optical system of a projection exposure apparatus or a predetermined optical member of various other optical systems is supported.

[0057]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, when a plurality of optical members in a projection optical system composed of a refraction system are actually held by holding members having a plurality of supporting points, the rotation angles of these holding members are optimized. An example of the procedure will be described. FIG. 8 is a lens configuration diagram showing the projection optical system of the present embodiment. In FIG. 8, the projection optical system of the present embodiment uses a KrF excimer laser beam as illumination light for exposure to form a reduced image of the pattern of the reticle 12. An imaging optical system that projects onto the wafer 14. The optical axis AX of the projection optical system is parallel to the vertical direction, and the wafer 14 is located vertically below. And this projection optical system
A plano-concave lens L1, a biconvex lens L2, a positive meniscus lens L3, a plano-convex lens L4, a negative meniscus lens L5, a biconvex lens L6, a plano-concave lens L7, and a biconcave lens are sequentially arranged along the optical axis AX from the reticle 12 side to the wafer 14 side. L
8, plano-concave lens L9, plano-convex lens L10, negative meniscus lens L11, positive meniscus lens L12, biconvex lens L13, biconvex lens L14, positive meniscus lens L1
5, negative meniscus lens L16, negative meniscus lens L
17, biconcave lens L18, negative meniscus lens L19,
Positive meniscus lens L20, biconvex lens L21, biconvex lens L22, negative meniscus lens L23, biconvex lens L
24, a positive meniscus lens L25, a positive meniscus lens L26, a positive meniscus lens L27, a negative meniscus lens L28, and a positive meniscus lens L29. An aperture stop 31 is arranged between the positive meniscus lens L20 and the biconvex lens L21.

In this embodiment, a series of eight negative meniscus lenses L16 and negative meniscus lenses L1 as optical members are used.
7. A holding member in which a biconcave lens L18, a negative meniscus lens L19, a positive meniscus lens L20, a biconvex lens L21, a biconvex lens L22, and a negative meniscus lens L23 have the same three support points as the holding members 4A and 4B in FIG. (See FIG. 18). The reticle-side and wafer-side surfaces of the negative meniscus lens L16 are referred to as surfaces A and B, respectively.
, Surface O, surface P from the reticle-side surface 17 to the wafer-side surface of the negative meniscus lens L23.
Call.

First, in the projection optical system of this embodiment, the distance D0 on the optical axis from the reticle 12 to the lens surface closest to the reticle, and the distance on the optical axis from the lens surface closest to the wafer to the wafer 14 (working distance). ) WD, projection magnification β, maximum value NA of the numerical aperture on the wafer side, diameter φEX of a circular exposure area (projection area) on the wafer surface, and object image (reticle 1)
Table 1 below shows the distance L on the optical axis between the wafer 2 and the wafer 14). The unit of the length or interval in Tables 1 and 2 below is mm as an example.

[0060]

[Specifications of projection optical system] D0 = 95.739 WD = 18.025 β = 1/5 N.A. (maximum value) = 0.65 φEX = 31.2 L = 1250

Next, Table 2 below shows lens data of the projection optical system shown in FIG. 8 in this example. In Table 2, each parameter is defined as follows. i: order of lens surfaces from the reticle 12, r: radius of curvature of the i-th lens surface, d: interval from the i-th lens surface to the next lens surface, n: i-th lens surface to the next lens surface The refractive index at a wavelength of 248.4 nm of glass or air up to. in this case,
For example, quartz is used as the glass material of the lens.
In addition, the 31st to 46th surfaces correspond to the surfaces A to P in FIG.

[0062]

[Table 2] [Lens data of projection optical system] irdn 1 ∞ 20.000 1.50839 2 336.170 15.668 1 3 563.367 34.000 1.50839 4 -332.714 1.000 1 5 249.094 27.524 1.50839 6 1176.506 1.000 1 7 240.828 30.250 1.50839 8 ∞ 1.000 1 9 244.881 31.413 1.50839 10 110.226 25.492 1 11 644.121 21.700 1.50839 12 -328.953 1.000 1 13 ∞ 13.650 1.50839 14 131.044 31.274 1 15 -213.280 12.500 1.50839 16 218.736 26.000 1 17 -136.472 14.000 1.50839 18 ∞ 31.419 1 19 ∞ 36.700 1.50839 20 -173.675 12.08 1 21 132.991 31.308 1.50839 22 -192.471 1.000 1 23 -765.118 26.256 1.50839 24 -285.268 1.000 1 25 2894.323 26.250 1.50839 26 -526.328 1.000 1 27 507.490 27.709 1.50839 28 -1947.222 1.000 1 29 240.851 33.368 1.50839 30 1110.453 1.000 131 (A) 192.0 1.50839 32 (B) 137.138 9.450 1 33 (C) 173.194 17.600 1.50839 34 (D) 129.182 38.413 1 35 (E) -281.451 13.500 1.50839 36 (F) 235.460 33.518 1 37 (G) -163.802 34.000 1.50839 38 (H)- 1790.552 33.449 1 39 (I) -449.437 22.117 1.50839 40 (J) -234.289 13.000 1 41 (K) 1108.176 29.200 1.50839 42 (L) -443.806 1.000 1 43 (M) 528.770 38.000 1.50839 44 (N) -505.654 18.010 1 45 (O) -257.696 24.750 1.50839 46 (P) -304.843 1.000 1 47 442.554 31.050 1.50839 48 -3008.588 1.000 1 49 231.883 29.400 1.50839 50 520.812 1.000 1 51 173.241 29.750 1.50839 52 304.512 1.000 1 53 135.803 36.000 1.50839 54 367.207 4.609 1 55 555.265 20.000 1.50839 56 80.149 24.952 1 57 91.120 57.685 1.50839 58 621.786 (WD) 1

FIG. 9 shows the wavefront aberration on the optical axis of the wafer surface of the projection optical system when the deformation of each lens constituting the projection optical system of this embodiment is not considered. In FIG. 9, RMS (root-mean-squam) which is the maximum value of the numerical aperture NA, the exposure wavelength λ, and the square root of the average value of the square of the deviation from the ideal spherical wave.
re) are as follows, respectively. NA = 0.65, λ = 0.248385 (μm), RMS = 0.01077 · λ In FIG. 9, the interval Δ between curves representing equal wavefronts is 0.02
Λ, and the wavefront aberration is a sufficiently small value.

Next, the first step ST1 to the fourth step S of FIG.
The operation of optimizing the rotation angles of the negative meniscus lens L16 to the negative meniscus lens L23 in FIG. 8 corresponding to T4 will be described. At this time, a holding member that supports the negative meniscus lens L16 to the negative meniscus lens L23 at three points is provided.
This is represented by the holding member 4 having three support points 4a to 4c in FIG. The support points 4a to 4c are equiangularly spaced (120 °
At intervals), and in the initial state, the support points 4
The Y axis is taken in parallel with a and a straight line passing through the optical axis and the X axis is taken in parallel with a straight line passing through the optical axis and perpendicular to the Y axis. When the holding member 4 is rotated, a counterclockwise rotation angle from the state of FIG. In the initial state, all the holding members 4
Is set to 0.

[First Step] Here, the surfaces A to L of the negative meniscus lens L16 to the negative meniscus lens L23 are generated by holding the negative meniscus lenses L16 to L23 using the holding members 4 that support the three points. The amount of deformation of P is calculated by structural analysis. The rotation angle θ of the holding member 4 at the time of calculation is all 0, and the sign is positive in the direction in which the light beam travels (the direction of the wafer).

FIGS. 10 (a) and 10 (b), FIGS.
(B), FIG. 12 (a), (b), FIG. 13 (a),
(B), FIG. 14 (a), (b), FIG. 15 (a),
(B), FIGS. 16 (a), (b), FIGS. 17 (a), (b)
Are the planes A, B,..., Respectively calculated as described above.
It is the figure which represented the distribution of the deformation amount of surface O and surface P with a contour line.
The interval between the contour lines is 5 nm and 2 nm in FIGS. 10A and 10B, respectively, 5 nm and 2 nm in FIGS. 11A and 11B, and 2 n in FIGS. 12A and 12B.
m, FIGS. 13 (a) and 13 (b) show 1 nm and 2n, respectively.
m, FIGS. 14A and 14B are both 10 nm, and FIG.
(A) and (b) are both 20 nm, and FIGS. 16 (a) and (b)
Are both 20 nm, and FIGS. 17A and 17B are both 10 nm.
It is. For example, it can be seen from FIG. 10A that a relatively large deformation occurs between the support points 4a to 4c of the holding member 4.

[Second Step] In this step, the residual aberration of the projection optical system caused by the deformation of the planes A to P is calculated.
FIG. 19 shows the wavefront aberration on the optical axis of the wafer surface of the projection optical system calculated in this manner. In FIG. 19, the maximum value NA of the numerical aperture, the exposure wavelength λ, and the interval Δ of the uniform wavefront curve are RMS of deviation from ideal spherical wave as same as in FIG.
Is as follows.

RMS = 0.01872 · λ By comparing FIG. 9 with FIG. 19, the wavefront aberration of the projection optical system is deteriorated by the deformation of each lens, and 3
It can be seen that the wavefront shape is rotationally asymmetric with respect to the optical axis due to the deformation due to the point support.

[Third Step] Here, the negative meniscus lens L16 to the negative meniscus lens L16 centered on the optical axis of the projection optical system and canceling the residual aberration obtained in the second step.
The rotation angles of the 23 holding members 4 are calculated. First, using the data of the amount of deformation of the surface O and the surface P in FIGS. 17A and 17B, the wavefront aberration in FIG.
The rotation angle θ (see FIG. 18) of the negative meniscus lens L23 (holding member) is calculated. As a result, 60 ° is obtained as the optimum rotation angle θ.

FIG. 20 shows the wavefront aberration on the optical axis of the wafer surface of the projection optical system calculated under the condition that the negative meniscus lens L23 and the holding member holding the lens are rotated by 60 °. The maximum value NA of the numerical aperture, the exposure wavelength λ, and the interval Δ between the equal wavefront curves are the same as in FIG.
The RMS of the deviation from the ideal spherical wave is as follows. RMS = 0.01344 · λ Comparison between FIG. 20 and FIG. 19 shows that the wavefront aberration of the projection optical system is largely improved to be substantially symmetric by optimizing the rotation angle of one predetermined lens. I understand.

Similarly, planes A to N in FIGS.
The negative meniscus lens L16 to the biconvex lens L for reducing the wavefront aberration shown in FIG.
22 are calculated. As a result, the optimal rotation angles of the negative meniscus lens L16, the biconcave lens L18, the negative meniscus lens L19, and the positive meniscus lens L20 are 60 °, and the optimal rotation angles of the other lenses are 0 °.

FIG. 21 shows the wavefront aberration on the optical axis of the wafer surface of the projection optical system calculated under the condition that each of the plurality of lenses is rotated by 60 °. In FIG. The NA, the exposure wavelength λ, and the interval Δ between the uniform wavefront curves are the same as in FIG. 19, and the RMS of the deviation from the ideal spherical wave
Is as follows. RMS = 0.0112 · λ When comparing FIG. 21, FIG. 19, and FIG. 9, the wavefront aberration of the projection optical system is largely increased to the state of FIG. It can be seen that it has been improved.

In the case where a three-point supporting holding member is used as in the present embodiment, this holding member and the optical member are connected together by 60 °.
The effect obtained by rotating is the same as the effect obtained by rotating the holding member by −60 ° together with the optical member. [Fourth Step] In the projection optical system shown in FIG. 8, the lenses are held together with the holding member in the lens barrel of the projection optical system so that the rotation angles of the negative meniscus lens L16 to the negative meniscus lens L23 determined by optimization in the third step are obtained. Actually incorporate. For other lenses, without considering the rotation angle,
It is incorporated into the lens barrel together with the holding member. by this,
The wavefront aberration of the projection optical system after assembly is as shown in FIG.
This is the same as when there is no deformation in each lens, and high imaging characteristics can be obtained.

Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

[0075]

According to the first optical system of the present invention, since a plurality of optical members are held in a stable posture by a holding member having a plurality of support points, stable optical characteristics (imaging performance) are always obtained. Etc.) are obtained. In addition, since at least one rotation angle of each holding member is set so that the residual aberration of the optical system is reduced, high optical characteristics can be obtained.

Next, according to the second optical system of the present invention, since the plurality of optical members are held in a stable posture by the holding member having the plurality of support points, stable optical characteristics (image formation) are always obtained. Performance). Further, by simply setting the relative rotation angles of the plurality of holding members to a predetermined state, reproducible optical characteristics can be obtained, so that assembly adjustment is easy. Further, according to the first or second method of manufacturing the optical system of the present invention, the first optical system of the present invention can be easily manufactured in a short time without complicated trial and error assembly adjustment steps. There is.

Further, according to the exposure apparatus of the present invention, since the imaging performance of the projection optical system is stably maintained even when vibration occurs during the step movement or the scanning exposure, the pattern image of the mask is always kept high. There is an advantage that it can be transferred onto a substrate with high accuracy.

[Brief description of the drawings]

FIG. 1 is a partially cutaway configuration view showing a projection exposure apparatus according to an example of an embodiment of the present invention.

FIG. 2 is a perspective view showing a state where a lens 3A and a holding member 4A in FIG. 1 are separated.

FIG. 3 is an explanatory view showing a method of holding a lens 3A by a holding member 4A.

FIG. 4 is a diagram for explaining a part of a manufacturing process (a series of processes for optimizing a rotation angle of a predetermined lens) in the projection optical system of FIG. 1;

FIG. 5 is a partially cutaway view showing a configuration example of a Fizeau interferometer for measuring a deformation amount of a lens 3B held by a holding member 4B.

FIG. 6 is a diagram showing a configuration example of a Fizeau interferometer for measuring a wavefront aberration of the projection optical system 1.

FIG. 7A is a perspective view of a main part showing a case where rotation angles of holding members 4A to 4C are set in the same direction in another example of the embodiment of the present invention, and FIG. 7B is a holding member. 4A-4
It is a perspective view of the principal part which shows the case where the rotation angles of C were alternated.

FIG. 8 is a lens configuration diagram illustrating a projection optical system according to an embodiment of the present invention.

FIG. 9 is a diagram illustrating wavefront aberration on the optical axis when the deformation of each lens of the projection optical system of the embodiment is not considered.

FIG. 10 is a diagram showing a state of deformation of surfaces A and B in FIG. 8;

FIG. 11 is a view showing a state of deformation of surfaces C and D in FIG. 8;

FIG. 12 is a view showing a state of deformation of surfaces E and F in FIG. 8;

FIG. 13 is a diagram showing a state of deformation of surfaces G and H in FIG. 8;

FIG. 14 is a diagram showing a state of deformation of planes I and J in FIG. 8;

FIG. 15 is a view showing a state of deformation of surfaces K and L in FIG. 8;

FIG. 16 is a diagram showing a state of deformation of surfaces M and N in FIG. 8;

FIG. 17 is a diagram showing a state of deformation of surfaces O and P in FIG. 8;

FIG. 18 is a cross-sectional view showing a holding member that supports the plurality of lenses of FIG. 8 by a three-point support method.

FIG. 19 is a diagram showing a wavefront aberration on the optical axis when the deformation of each lens of the projection optical system of the embodiment is considered.

FIG. 20 is a diagram showing wavefront aberration on the optical axis when the rotation angle of one lens of the projection optical system of the example is optimized.

FIG. 21 is a diagram illustrating wavefront aberration on the optical axis when the rotation angles of a plurality of lenses of the projection optical system of the example are optimized.

FIG. 22 is an explanatory view showing a conventional lens holding method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Projection optical system, 2 ... Barrel, 3A, 3B ... Lens, 4
A, 4B: holding member, 4Aa-4Ac, 4Ba-4Bc
... Support points, 5A, 5B ... Pressing ring, 5Aa-5Ac ...
Holding part, 6A-6C: spacer, 12: reticle, 13
Reticle stage, 14 wafer, 15 wafer stage, 16 laser light source, 20 condenser lens, 22 imaging device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masato Hatazawa 3-2-3 Marunouchi, Chiyoda-ku, Tokyo F-term in Nikon Corporation (reference) 2H044 AA05 AA12 AC04 2H087 KA06 KA21 LA21 NA09 PA15 PA18 PB20 QA01 QA18 5F046 AA01 BA04 CA07 CB11 CC04 DA12

Claims (5)

[Claims] 1. An optical system having a plurality of optical members, wherein a plurality of holding members are provided for supporting the plurality of optical members at a plurality of support points, respectively, between the plurality of support points of the plurality of optical members. An optical system characterized in that at least one rotation angle of the plurality of holding members is adjusted so as to reduce residual aberration of the optical system caused by the deformation in the above. 2. An optical system having a plurality of optical members, wherein a plurality of holding members are provided for supporting the plurality of optical members at a plurality of support points, respectively. The same number is arranged at equal angular intervals, and the directions of the plurality of support points of the plurality of holding members are substantially the same, or an intermediate position between the two support points of the first holding member. An optical system, wherein a relative rotation angle between the plurality of holding members is set such that one support point of a second holding member adjacent to the second holding member is located. 3. A method of manufacturing an optical system, comprising: a plurality of optical members; and a plurality of holding members each supporting the plurality of optical members at a plurality of support points, wherein the plurality of optical members include a plurality of optical members. A first step of obtaining a deformation amount of the optical member corresponding to the supporting point, and a step of obtaining a residual aberration of the optical system caused by deformation of the plurality of optical members between the plurality of supporting points. A third step of obtaining at least one rotation angle of the plurality of holding members about the optical axis of the optical system for reducing the calculated residual aberration; and a third step. Adjusting a rotation angle of at least one of the plurality of holding members in the optical system based on the rotation angle determined in (4). 4. A method of manufacturing an optical system, comprising: a plurality of optical members; and a plurality of holding members each supporting the plurality of optical members at a plurality of support points, wherein the plurality of optical members are A first step of determining the residual aberration of the optical system caused by the deformation between the support points of the plurality of optical elements, and the plurality of holdings about the optical axis of the optical system for reducing the measured residual aberration. A second step of obtaining at least one rotation angle of the member; and adjusting at least one of the plurality of holding members in the optical system based on the rotation angle obtained in the second step. And a third step. 5. An exposure apparatus comprising: the optical system according to claim 1; a mask stage for holding a mask; and a substrate stage for holding a substrate. An exposure apparatus used as a projection optical system for projecting an image of a pattern onto the substrate.