JPH09236929A - Projection optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily compensate coma aberration from the external part, by dividing an outer frame for holding plural optical elements constituting a projection optical device between a pupil surface of the device and a mask, and adjusting the relative position of the divided outer frames. SOLUTION: The initially adjusted projection optical device 20 is loaded on a printing measuring unit so as to print a sample pattern. And, various kinds of aberration on the printed image is measured. Next, a washer capable of excellently compensating the measured aberration is selected. At this time, a washer of a thickness suitable to excellently compensate the coma aberration is selected. Thereafter, bolts 36a and 36b are loosened, and the upper lens barrel 32a is slightly jacked up by jack-up bolts 41a and 41b so as to replace the washer. The projection optical device 20 where the aberration is already compensated is loaded on an aligner, then, a pattern on a reticle 10 is projected in an aligning area of a wafer through the projection optical device 20. Thus, a distance between the lenses 28b and 28c is adjusted from the outside of the lens barrel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of projection optical devices, and more particularly to an aberration correction technique for a projection optical device which comprises a plurality of optical elements and projects a pattern formed on a mask onto a substrate. .

[0002]

2. Description of the Related Art In general, when correcting an aberration of a projection optical apparatus consisting of a plurality of optical elements, an interval between certain optical elements is adjusted. In the conventional projection optical apparatus shown in FIG. 4, the five lenses 42, 44, 46, 48 and 50 are
The lens barrels 52, 54, 56, 58, and 60 hold the lens barrel 62 inside. These lens frames 52,
54, 56, 58, and 60 are attached to the lens barrel 6 by the holding ring 64.
2 fixed inside. A washer 66 is interposed between the lens frames 54 and 56. In this device, when the coma aberration is corrected, the washer 66 is replaced with another washer having a different thickness, and the distance from the pupil plane 68 of the optical device to the reticle 70 side (hereinafter, “coma aberration adjustment interval”).
That)).

[0003]

However, in the conventional device as described above, when the coma aberration is corrected, the pressing rings 54 must be removed from the lens barrel 62 and then the lens frames 52 and 54 must be removed. And the work was complicated. Further, when the projection optical apparatus is mounted on the exposure apparatus, changing the lens interval after mounting the optical apparatus on the exposure apparatus causes a significant decrease in work efficiency.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a projection optical apparatus which can easily correct coma from the outside and a projection exposure apparatus using the projection optical apparatus.

[0005]

According to the present invention, in order to solve the above problems, an outer frame for holding a plurality of optical elements constituting an apparatus is divided between a pupil plane of the apparatus and a mask. The coma aberration is corrected by adjusting the relative positions of the divided outer frames.

[0006]

According to the present invention having the above-described structure, the coma aberration can be adjusted without disassembling the projection lens, so that the coma aberration can be easily corrected at any stage after the apparatus is mounted on the exposure apparatus. it can.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the following examples.

FIG. 1 schematically shows a projection exposure apparatus according to this embodiment. This apparatus projects and exposes a predetermined pattern formed on the reticle 10 onto the wafer 12. In the figure, the exposure light output from the exposure light source 14 illuminates the reticle 10 held by the reticle stage 16. The light transmitted through the reticle 10 reaches the wafer 12 placed on the wafer stage 18 by the projection optical device 20, and the pattern of the reticle 10 is projected and exposed on the exposure area. A reflection mirror 22 is fixed on the wafer stage 18 so as to reflect the light from the interferometer 24. The interferometer 24 detects the position of the wafer stage 18 (wafer 12) based on the light returned from the reflection mirror 22. The drive device 26 is mounted on the wafer stage 18.
Are connected, and the wafer stage 18 is driven based on the position of the wafer 12 detected by the interferometer 24.

2 and 3 show the projection optical device 20 as viewed from the reticle 10 side and as viewed from a direction perpendicular to the plane of the paper (cross section), respectively. In the figure, the projection optical device 20 includes five lenses 28a, 28b, 28c, 2
8d, 28e, each lens 28a, 28b,
28c, 28d and 28e are respectively lens frames 30a and
It is arranged inside the lens barrel 32 while being held by each of 30b, 30c, 30d and 30e. The lens barrel 32 is composed of two upper lens barrels 32a and a lower lens barrel 32b, and the lower outer diameter of the upper lens barrel 32a fits into the upper inner diameter of the lower lens barrel 32b to suppress mutual eccentricity. There is. Lens frame 30a, 30
b, 30c, 30d and 30e are fixed in the lens barrels 32a and 32b by the pressing ring 31.

The upper and lower lens barrels 32a and 32b are provided with flanges 34a and 34b, respectively, and bolts 36a and 36 are provided at equal intervals in the circumferential direction of each flange.
A bolt hole into which b and 36c are screwed is formed. Bolts 36a, 36 between the upper lens barrel 32a and the lower lens barrel 32b
hoof-shaped washers 38a, 38 are provided on the outer circumferences of b, 36c.
b and 38c are inserted. In this device, the distance between the lenses 28b and 28c is adjusted by replacing these washers 38a, 38b, 38c. In the vicinity of the bolts 36a, 36b, 36c, jack-up bolts 41a, 41b, 41c as jack-up means for lifting the upper lens barrel 32a with respect to the lower lens barrel 32b penetrate the upper lens barrel 32a. , So as to come into contact with the upper surface of the lower lens barrel 32b. Then, when replacing the washers 40a, 40b, 40c, these jack-up bolts 41a, 41
b and 41c, upper lens barrel 32a and lower lens barrel 32b
It is designed to push the gap between and.

Next, a method of correcting the aberration of the projection optical device 20 will be described. The initially adjusted projection optical device 20 is mounted on a print measuring device (not shown), and a sample pattern is printed. Then, various aberrations in the printed image are measured. Next, a washer is selected that can satisfactorily correct the measured aberration. At this time, the commonly known Seidel's five aberrations (spherical aberration, coma aberration, astigmatism,
Of the distortion and field curvature, at least a washer having a thickness (same thickness) that can favorably correct coma is selected. Then, the bolts 36a, 36b, 36c are loosened, the upper barrel 32a is slightly lifted by the jack-up bolts 41a, 41b, 41c, and the washers are replaced.
In addition, the measurement of the aberration is not limited to the actual print image, and can be measured by a wavefront aberration measuring device using an aerial image or interference fringes.

The projection optical device 20 having the aberration corrected is
1 is mounted on the exposure apparatus shown in FIG. 1 and the pattern on the reticle 10 is projected and exposed onto the exposure area of the wafer 12 via the projection optical apparatus 20. In the above embodiment, the lens 28
Distance between b and 28c (upper barrel 32a and lower barrel 32b
Since the distance between the projection optical device 20 and the projection optical device 20 is adjusted from the outside of the lens barrel, the aberration can be easily corrected even after the projection optical device 20 is mounted on the exposure device.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and does not deviate from the gist of the technical idea of the present invention described in the claims. Various changes are possible with. For example, in the present embodiment, the washer of the same thickness is used to adjust only the distance between the lenses, so that the aberration of the axis is adjusted, but by using the washers of different thicknesses to tilt, Aberration correction can be performed asymmetrically. Further, in the above embodiment, the washer 38
Although the lens spacing is adjusted by a, 38b, and 38c, the upper lens barrel 32a and the lower lens barrel 32 are adjusted by using a driving device or the like.
It can also be configured to automatically adjust the distance from b. In the above embodiment, the upper lens barrel 32a and the lower lens barrel 32b are divided between the lenses 28b and 28c, but at least the pupil plane 100 of the apparatus and the reticle 10 are separated.
Just divide it between and.

[0014]

As described above, according to the present invention, the outer frame of the apparatus is divided between the pupil plane and the mask, and the relative positions of the divided outer frames are adjusted to obtain at least coma aberration. Since it is a configuration for correcting C., the coma aberration can be easily corrected from the outside.

[Brief description of drawings]

FIG. 1 is a conceptual diagram (front view) illustrating a configuration of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a division unit showing the projection optical apparatus according to the present embodiment.

FIG. 3 is a sectional view taken along the line A-A ′ in FIG. 2.

FIG. 4 is a sectional view showing a conventional projection optical device.

[Explanation of symbols]

10 ... Reticle 12 ... Wafer 20 ... Projection optical device 28a, 28b, 28c, 28d, 28e ... Lens 30a, 30b, 30c, 30d, 30e ... Lens frame 32a ... Top mirror Tube 32b ... Lower lens barrel 36a, 36b, 36c ... Bolt 38a, 38b, 38c ... Washer 41a, 41b, 41c ... Jack-up bolt 100 ... Pupil surface

Claims (3)

[Claims] 1. A projection optical apparatus, comprising a plurality of optical elements, for projecting a pattern formed on a mask onto a substrate, comprising: an outer frame for holding the plurality of optical elements, wherein the outer frame is provided in the apparatus. A projection optical device, characterized in that it is divided between a pupil plane and the mask, and adjusting means is provided for adjusting the relative positions of the divided outer frames so as to correct the coma aberration of the device. 2. A projection exposure apparatus for projecting and exposing a pattern formed on a mask onto a substrate via a projection optical system, wherein the projection optical system comprises a plurality of optical elements, and
An outer frame that holds the plurality of optical elements is provided, the outer frame is divided between the pupil plane of the projection optical system and the mask, and the coma aberration of the projection optical system is mainly corrected. A projection exposure apparatus comprising an adjusting means for adjusting the relative position of the divided outer frames. 3. The space between the divided outer frames is adjusted by inserting / removing a member having a predetermined thickness between the divided outer frames. The device according to claim 1 or 2.