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30 July 2002 Clear-field dual alternating phase-shift mask lithography
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A new double exposure technique using two alternating phase shift masks (APSMs) is developed for patterning clear field designs at ultra small critical dimensions. It is called Clear Field Dual APSM Lithography. It is based on the hypothesis that phase conflicts can be avoided for both masks if apertures oriented along the vertical direction are assigned to one mask, and those along the horizontal direction to the other. It is expressed as a heuristic mask synthesis strategy in which each mask is imaged at the full exposure dose. The strategy was validated using aerial image simulations of various design configurations. Interesting results were obtained regarding image stitching, tight patterns, design rules, image resonance and its mitigation, and the beneficial properties of phase edges.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Douglas A. Bernard and Jiangwei Li "Clear-field dual alternating phase-shift mask lithography", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002);

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