Source mask optimization (SMO) study for high-NA EUV lithography to achieve single patterning on random logic metal

Abstract

High numerical aperture (NA) extreme ultraviolet (EUV) lithography single patterning is evaluated through source mask optimization (SMO). The patterning performance is assessed on random logic metal design with minimum pitches of 24, 22, and 20nm in the horizontal direction to confirm the feasibility of logic metal scaling. We set a 1 square micron as a cell window and choose 200 gauges to include various types of features such as dense, isolated, and tip-to-tip. SMO is performed assuming eight permutations of a) dark-field versus bright-field, b) Ta-based versus low-n attenuated phaseshift masks, and c) with sub-resolution assist feature (SRAF) versus without SRAF. For each design, the process window is estimated.