Laser-damage impact on lithography system throughput

With the transition to high-power excimer laser sources for lithography systems, the impact of laser damage, particularly compaction in fused silica, on the optics life, dose at the wafer plane, and system throughput, is a major concern. This paper will develop the first-order equations for the analysis, apply the equations to a step-and-scan catadioptric system, and show that for 248-nm systems, the limitation on throughput is dose, not laser-induced damage, while at 193 nm, laser-induced 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.<
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