With escalating costs of higher-NA exposure tools, lithography engineers are forced to evaluate life-span extension of currently available lower-NA exposure tools. In addition to common resolution enhancement techniques such as off-axis illumination, edge movement, or applying sub-resolution assist features, Inverse Lithography Technology (ILT) tools available commercially at this moment offer means of extending current in-house tool resolution and enlarging process window for random as well as periodic mask patterns. In this paper we explore ILT pattern simplification procedures and model calibration for a range of illumination conditions. We study random pattern fidelity and critical dimension stability across process window for 65nm contact layer, and compare silicon results for both conventional optical proximity correction and inverse lithography techniques.

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