Abstract

The optical design of a light-tunnel illumination system for a prototype 193-nm excimer-laser-based photolithographic stepper is presented. We discuss the system design requirements and establish the first-order layout using paraxial matrix methods. We also discuss the aberrations that have the most impact on image formation and point out the key tolerance considerations. Throughput concerns relating to the laser relay optics, the illuminator, and the projection lens are also addressed. The condenser is installed on a stepper, whose I-line lens was replaced by a one-of-a-kind 10 × 193-nm refractive lens with N.A. = 0.35 and a field size of 10 mm². Measurements of uniformity, as well as lithographic results from the system, are presented.

© 1992 Optical Society of America