EFFECT OF ABSORBER THICKNESS ON IMAGE SHORTENING IN X-RAY-LITHOGRAPHY

Image shortening effects have been shown to be a problem for pattern r eplication using current optical tools. However a previous study [R. D ellaGuardia, J. R. Maldonado, and H. Oertel., J. Vac. Sci. Technol. B 12, 3936 (1994)] indicated that image shortening is less pronounced wh en pattern replication is performed using x-ray lithography. This arti cle describes the effect of absorber thickness on the Image shortening observed in x-ray lithography. The goal is to determine the optimum a bsorber thickness that minimizes Image shortening when replicating com plex patterns with the x-ray spectrum from the HELIOS storage ring ins talled at the IBM Advanced Lithography Facility. To study these effect s, an x-ray mask with four quadrants, each having different gold thick ness, was fabricated using the IBM vector scan (VS-5) electron-beam sy stem. The mask contains challenging patterns used in IBM devices with ground rules from 0.4 mu m down to 0.15 mu m, The image shortening eff ects for different mask/wafer gaps, various fine shapes, and feature s izes will be presented in this article. In addition, experimental resu lts with conventional and chemically amplified resists will be present ed ta shed light on the rob of resist in image shortening. (C) 1995 Am erican Vacuum Society.