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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 presented a novel approach to the EUV source-optic architecture using a high-brightness light source
array for direct integration within the illumination optical system. Spatial uniformity and Kohler illumination across the
entrance pupil is achieved by dividing the incident light into discrete bundles on a fly's eye mirror. These light bundles
form a secondary source image plane that is projected onto the pupil of the projection optics. This configuration allows
electronic adjustment of partial coherence and depth of focus for improved lithographic contrast and resolving
capability. By distributing total EUV power across discrete units, thermal and particle loadings become manageable
without the need for exotic materials or cooling schemes and sources of contaminating debris are reduced.
Experimental data from a 5×5 xenon-fed microdischarge source array is presented, demonstrating repetition rate and
source addressability for illumination patterning and grayscaling capability. In addition, experimental data from xenon-based
sources will be presented with a suite of plasma and optical diagnostic instruments, including conversion
efficiency, spectral purity and debris generation. Projections for scaling to HVM conditions will also be presented.
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