Microdischarge EUV source array and illuminator design for a prototype lithography tool

The joint specification projected in-band EUV power requirements at the intermediate focus will rise beyond 185W 2%-bw to maintain the necessary 80-100WPH throughput for economic viability. New improvements in photon efficiency and mask illumination are needed to reduce reflections and power demand, as well as improving source spatial uniformity. In 2006, Starfire Industries presented a microdischarge plasma light source concept for consideration as a potential HVM solution for high-power spatial and temporal multiplexing. Using a distributed array architecture, thermal and particle loadings become manageable when spread over 100s to 1000s of discrete units allowing power scalability. In addition, a key tenant is the potential for novel collection and illumination geometries that could simulate Kohler and pupil fill effects found in conventional fly's-eye mirror systems; thus leading to a reduction in optical elements and a factor of > 5x increase in total throughput. A top-level illuminator optical design based on the microsource array technology is presented, as well as thoughts on illumination efficiency, reticle uniformity, partial coherence and uniformity of the pupil fill for a realistic EUV source array. In addition, experimental data from xenon-based sources will be presented with a suite of plasma and optical diagnostic instruments, including conversion efficiency.