RESOLUTION-ENHANCING OPTICAL PHASE STRUCTURE FOR A PROJECTION ILLUMINATION SYSTEM

摘要

In an optical projection system for use in projection printing of masks to wafers, comprising an illumination system including a light source and a mask positioned in the optical path of the illumination system, an optical phase structure is positioned in the optical path between the light source and the mask. The phase structure comprises a pattern of distributed transparent features having at least one refractive index, the transparent features of said phase structure being related in position and orientation to the opaque features of the mask.