Wynne-Dyson projection lens with reduced susceptibility to UV damage

摘要

A Wynne-Dyson projection lens for use in an ultraviolet optical lithography system is disclosed, wherein the projection lens is configured to have reduced susceptibility to damage from ultraviolet radiation. The projection lens utilizes lens elements that are made of optical glasses that are resistant to damage from ultraviolet radiation, but that also provide sufficient degrees of freedom to correct aberrations. The glass types used for the lens elements are selected from the group of optical glasses consisting of: fused silica, S-FPL51Y, S-FSL5Y, BSM51Y and BAL15Y.

主权项

1. A Wynne-Dyson projection lens having object and image planes and an image field, and that has reduced susceptibility to compaction from ultraviolet radiation, the lens comprising along an optical axis:
a concave mirror having a concave surface; a positive lens group spaced apart from the concave surface of the concave mirror; first and second prisms made of either fused silica or BSM51Y and disposed adjacent the positive lens group opposite the concave mirror and on respective sides of the optical axis, with the first and second prisms having respective surfaces that reside adjacent the object and image planes; wherein the positive lens group consists of:
a first lens group having a cemented doublet consisting of a plano-convex lens element made of either S-FPL51Y, S-FSL5Y or fused silica and having a planar surface in contact with the prisms, and a negative meniscus lens made of either BAL15Y or BSM51Y; anda second lens group spaced apart from the first lens group and consisting of either one or two lens elements each made of either S-FSL5Y, S-FPL51Y or fused silica; and wherein the projection lens has a numerical aperture NA in the range from 0.16 to 0.2, a substantially unit magnification, is substantially doubly telecentric and a Strehl ratio of >0.95 over the image field for a spectral bandwidth that includes ghi radiation.