Catadioptric projection systems

Abstract

Catadioptric projection systems are disclosed for projecting an illuminated region of a reticle onto a corresponding region on a substrate. The systems are preferably used with ultraviolet light sources (e.g., 193 nm). The systems comprise a first imaging system, a concave mirror, and a second imaging system. The first imaging system comprises a single-pass lens group and a double-pass lens group. The single-pass lens group comprises a first negative subgroup, a positive subgroup, and a second negative subgroup. Light from the illuminated region of the reticle passes through the single-pass lens group and the double-pass lens group, and reflects from the concave mirror to pass back through the double-pass lens group to form an intermediate image of the illuminated region of the reticle. The light is then directed to the second imaging system that re-images the illuminated region of the reticle on the substrate. Alternatively, light from the single-pass lens group is reflected by a turning mirror to the double-pass lens group, wherein the light returning through the double-pass lens group continues directly to the second imaging system.

Description

[0001]This application claims the benefit of Japanese patent application no. 8-149903, filed May 20, 1996, and is a continuation in part of U.S. patent application Ser. No. 08 / 212,639, filed Mar. 10, 1994 and which issued as U.S. Pat. No. 5,636,066, U.S. patent application Ser. No. 08 / 628,165, filed Apr. 25, 1996 and which issued as U.S. Pat. No. 5,689,377, U.S. patent application Ser. No. 08 / 552,453, filed Nov. 3, 1995 and which issued as U.S. Pat. No. 5,691,802, U.S. patent application Ser. No. 08 / 429,970, filed Apr. 27, 1995 and which issued as U.S. Pat. No. 5,808,805 and is currently pending as U.S. reissue application Ser. No. 09 / 764,157, U.S. patent application Ser. No. 08 / 515,631, filed Aug. 16, 1995 and which issued as U.S. Pat. No. 5,861,997 and is currently pending as U.S. reissue application Ser. No. 09 / 766,486, which correspondingly claim priority under 35 U.S.C. Section 119(a)-(d) to Japanese patent application no. 5-051718, filed Mar. 12, 1993, Japanese patent applicat...

AI Technical Summary

Benefits of technology

[0026]Embodiments of the invention in which the reticle and wafer are in parallel planes or are along the same axis simplify wa

Problems solved by technology

Purely refractive projection systems are inadequate alat ultraviolet wavelengths.

Unfortunately, combining optical elements of synthetic fused quartz and fluorite is ineffective in eliminating chromatic aberration because the Abbe numbers of synthetic quartz and fluorite are not sufficiently different.

Therefore, refractive optical systems for wavelengths less than about 300 nm suffer from unacceptable levels of chromatic aberration.

The refractive index of fluorite changes relatively rapidly with temperature and fluorite polishes poorly.

Therefore, most ultraviolet optical systems do not use fluorite, and thus exhibit uncorrected chromatic aberration.

Because the manufacture of precision aspheric surfaces is extremely difficult, a reflective projection system using an aspheric mirror is prohibitively expensive.

However, because it is symmetric, the optical system has a short working distance.

In addition, because it is difficult with this system to separate the incident light beam and the reflected light beam, a beamsplitter is required.

Consequently

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