Proceedings PaperRim phase-shift mask combined with off-axis illumination: a path to .5lambda/NA geometries
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Phase Shift Mask (PSM) approaches may be classified as either strong or weak. This paper addresses weak PSM approaches which are attractive because of their universal applicability to any pattern. A simple design algorithm for rim PSM, called Biased Rim Design (BiRD), is described. When used with normal stepper illumination ((sigma) equals .5), the modest benefits of rim PSM are of questionable value in many cases. However, theoretical considerations show a synergy of weak PSM combined with off-axis illumination. One specific combination termed BiRD/QUEST, is explored through a series of simulations. These results suggest that a properly biased weak PSM with appropriate illumination allows robust manufacturing of 0.5 (lambda) /NA lithographic patterns.