JPH01102398A - Collimating optical system - Google Patents

Abstract

PURPOSE:To lessen partial shadow gradation by making X-ray emitted from an X-ray source as parallel light by the use of a paraboloid mirror, using a monocrystal superconductor en route the parallel light and providing a film of excellent permeability of the parallel light of a single wave front. CONSTITUTION:X-rays 2 emitted from an X-ray source 1 are converted into parallel light by the use of a paraboloid mirror 3, only the parallel light having a vertical wave front in the direction of crystal by a filter which is a supercon ductor is emitted, irradiating a mask 5, and the image is transferred to a wafer 6. A monocrystal superconductor is used as a filter 4, permeability of only a plane wave having a vertical wave front in the crystal direction of monocrystal is approximately 100% by superconductive performance because the monocrystal direction is aligned with optical axial direction of the mirror 3, and the other have every small permeability. Since the coherence of the parallel light emitted through the filter 4 is high and the light emitted from the mask 5 is almost parallel transferred to the wafer 5 except the case where a lattice interval of the mask 5 is near to using wave length, partial shadow gradation is not produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an X-ray method for exposing semiconductors, etc. by irradiating a mask with far ultraviolet rays (X-rays) generated from an X-ray light source and transferring the image of the mask onto a wafer. This invention relates to a collimating optical system used in an exposure apparatus.

Conventional technology Conventional 1. As an apparatus for exposing semiconductors using X-rays, the configuration described in the materials distributed at the "Current status and future of ultra-precision technology in X-ray optics" symposium sponsored by the Japan Society for Precision Engineering is known. There is. The conventional X-ray exposure point apparatus will be described below with reference to FIG.

As shown in FIG. 3, X-rays 32 emitted from an X-ray light source 31
was irradiated onto a mask 35 having a mask pattern 34 on a mask substrate 33, and the pattern was transferred onto a wafer 36 by the light transmitted through the mask pattern 34, thereby performing exposure at the same magnification.

Problems to be Solved by the Invention However, in the conventional configuration described above, the size of the X-ray light source 31 is finite, and the light incident on the mask pattern 34 is different from light having a single wavefront and has a complex wavefront. Since the light has a wavefront of .delta., a penumbra blur of .delta. occurs in the image of the mask pattern 34 transferred to the surface of the wafer 86.

The amount of penumbra blur has the relationship shown in the following equation, where the size of the X-ray light source 81 is equal to the distance from the X-ray light source 31 to the mask 35, and the distance from the L1 mask 35 to the wafer 36 is g.

δ=g−D/L In other words, the amount of penumbra blur δ is the size D of the X-ray light source 31
and the distance from the wafer 36 to the mask 35 (gap M)
g, and inversely proportional to the distance from the X-ray light source 31 to the position of the mask 35.

From this, in order to reduce the amount of penumbra blur δ,
Although it is possible to reduce the size D of the X-ray light source 31 and the gap amount g from the wafer 36 to the mask 35, there is a limit to reducing the gag amount g due to the protrusion of the wafer 36 and the like.

Further, if the distance from the X-ray light source 31 to the position of the mask 35 is increased, the amount of penumbra blur δ becomes smaller, but there is a problem in that the amount of light decreases and the throughput deteriorates.

Further, as a light source, there is a synchrotron radiation light source with very good synchrotron radiation coherency, but this light source is very large and has the problem that the exposure apparatus itself becomes very large.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and it is possible to improve the coherency of X-rays irradiated to a mask even if a conventional X-ray light source is used. Another object of the present invention is to provide a collimating optical system that can make the penumbra that is transferred to the wafer extremely small.

Means for Solving the Problems The technical means of the present invention for solving the above problems is an X-ray light source and a paraboloid that converts the X-rays emitted from the X-ray light source into parallel light. It is equipped with a mirror, and a filter that is placed on the optical axis of the parabolic mirror, is made of a superconductor with a single crystal structure, and the direction of the single crystal is aligned with the optical axis direction of the parabolic mirror. be.

action The effects of the above technical means are as follows.

That is, the X-rays emitted from the X-ray light source are turned into parallel light by the parabolic mirror. Since the size of the X-ray light source is finite, the parallel light emitted from this parabolic mirror is a mixture of parallel light with various angular components. A filter made of a superconductor with a single-crystal structure has superconducting performance only in the crystal direction, so this filter has a very high transmittance only for light with a wavefront perpendicular to the crystal direction, so the light emitted from the filter is becomes a plane wave with high coherency.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a collimating optical system in an embodiment of the present invention.

In FIG. 1, 1 is an X-ray light source, 2 is an X-ray emitted from the X-ray light source 1, 3 is a parabolic mirror that converts the X-rays 2 into parallel light, and 4 is a superconductor with a single crystal structure. Single crystal direction 4
a (see FIG. 2) is a filter aligned with the optical axis direction of the parabolic mirror 3, 5 is a mask, and 6 is a wafer.

Next, the operation of the above embodiment will be explained.

X-rays 2 emitted from an X-ray light source 1 are converted into parallel light by a parabolic mirror 3. This parallel light is passed through a filter 4 which is a superconductor, and only the parallel light having a wavefront perpendicular to the crystal direction 4a is emitted and irradiated onto a mask 5, and this image is transferred onto a mask 6.

As filter '4, a single-crystal superconductor is used as described above, and as shown in FIG. In terms of performance, only plane waves having a wavefront perpendicular to the crystal direction 4a of the single crystal have a transmittance of almost 100%, while transmittances of other plane waves are extremely small. Therefore, the coherency of the parallel light emitted from the filter 4 is very high, and the light emitted from the mask 5 is almost parallel to the wafer 6, unless the grating spacing of the mask 5 is close to the wavelength used.
, so no penumbra blurring occurs. Furthermore, the distance between the mask 5 and the wafer 6 can also be increased.

Effects of the Invention As described above, according to the present invention, X-rays emitted from an Since a filter is placed that improves the transmittance of only the parallel light on the wavefront, the coherency of the parallel light that irradiates the mask is extremely high, making it possible to minimize the penumbra blur of the image projected onto the wafer. can.

[Brief explanation of the drawing]

1 and 2 show a collimating optical system in an embodiment of the present invention, FIG. 1 is an overall sectional view, FIG. 2 is an optical path diagram of a filter, and FIG. 3 is a conventional X-ray exposure optical system. FIG. DESCRIPTION OF SYMBOLS 1... X-ray light source, 2... X-ray, 3... Parabolic mirror, 4... Filter, 5... Mask, 6... Wafer. Name of agent: Patent attorney Toshio Nakao and one other personfj
il Figure 2 Figure 3

Claims (1)

[Claims] It consists of an X-ray light source, a parabolic mirror that converts the X-rays emitted from the X-ray source into parallel light, and a superconductor with a single crystal structure that is placed on the optical axis of the parabolic mirror. A collimating optical system characterized by comprising a filter whose crystal direction is matched with the optical axis direction of a parabolic mirror.