| Summary: | 碩士 === 國立臺灣大學 === 電機工程學研究所 === 96 === In the field of microlithography the demand for highly integrated electronic circuits has motivated investigations into better image resolutions. Inverse lithography technique is a revived resolution enhancement technique (RET), which could decrease semiconductor process coefficient k1 in the Rayleigh criterion and can improve the image resolution. Inverse lithography attempts to synthesize the input mask which leads to the desired output wafer pattern by inverting the forward model from mask to wafer. An optimization strategy is introduced to promote the generation and placement of sub-resolution assist features. This approach uses the pixel-based mask representation, a continuous function formulation, and gradient-based iterative optimization techniques to solve the inverse problem. The continuous function formulation with analytic calculation of the gradient in O(MNlog(MN)) operations for an M × N pixel pattern makes it practically feasible. We propose a two step strategy for our optimization problem. The original mask is split into several parts, and processed individually. Later, all parts are combined and optimized to derived complete mask for lithography. The process would converge to the error tolerance faster than the original one-step approach. After this process, the optimal mask would be generated, and the computational time would be shorter than the original optimization process.
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