LASER-DAMAGE IMPACT ON LITHOGRAPHY SYSTEM THROUGHPUT

With the transition to high-power excimer laser sources for lithograph y systems, the impact of laser damage, particularly compaction in fuse d silica, on the optics life, dose at the wafer plane, and system thro ughput, is a major concern. This paper will develop the first-order eq uations for the analysis, apply the equations to a step-and-scan catad ioptric system, and show that for 248-nm systems, the limitation on th roughput is dose, not laser-induced damage, while at 193 nm, laser-ind uced damage becomes the limitation for throughput for system lifetimes in excess of ten years. The boundary conditions used in the analyses are based on design experience at SVG Lithography Systems, Inc. (SVGL) , data from excimer laser manufacturers, and papers presented at SPIE Microlithography 1995.