CRITICAL EXAMINATION OF SUBMICRON OPTICAL LITHOGRAPHY USING SIMULATED PROJECTION IMAGES.

Abstract

The prospects for submicron lithography with 0. 75 and 0. 5 mu m minimum features are investigated. Two lens systems are analyzed; a commercially available 0. 28 NA lens operating at 436 nm, and an advanced 0. 35 NA lens operating at 365 nm. The features studied include contact holes, rectangular lines and spaces, and equal line space gratings, and are representative of many typical IC mask patterns. Linewidth tailoring or biasing allows these features to be printed within tolerance simultaneously if the exposure can be controlled within plus or minus 6%. The corresponding depth of focus is about 3 mu m for the 0. 75 mu m features, and 1. 5 mu m for the 0. 5 mu m features. More general shape correction may be needed to print objects of arbitrary complexity.