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26 March 2007 Utilization of optical proximity effects for resist image stitching
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As alternative approaches (i.e. EUV) to pattern smaller device geometries are being explored but none has showed maturity for large volume production, 193nm ArF lithography continues to be the workhorse for semiconductor manufacturing industry. The extension of 193nm lithography heavily depends on the application of Resolution Enhancement Technologies, driving k1 factor closer to the theoretical limit of 0.25. One effective way to drive k1 lower is the combination of dipole illumination with embedded phase-shifting mask (EPSM). However, one of the disadvantages of dipole illumination is the presence of forbidden pitches due to that the illumination conditions are only optimized for the critical pitches. One obvious solution to address this issue is the double exposure strategy. With the critical pitches are patterned using dipole illumination, the looser pitches are addressed by a less aggressive illumination condition. One concern of this double exposure strategy is that the geometries from the first exposure and the geometries from the second exposure need be seamlessly stitched together for certain device designs. This paper discusses the OPC optimization for image stitching. Three stitch OPC schemes are studied to stitch two resist space features together. The results show that the reticle registration tolerance for image stitching depends on how the stitch OPC is done. The registration error tolerance is maximal when the OPC is performed on the low resolution image.
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Yongfa Fan and Tom Castro "Utilization of optical proximity effects for resist image stitching", Proc. SPIE 6520, Optical Microlithography XX, 65201S (26 March 2007);

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