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10 May 2005 Comprehensive CD uniformity control across lithography and etch
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It has been shown that across-wafer CD (critical dimension) uniformity can be improved by compensating for systematic CD variations through the litho-etch sequence by tuning the across-wafer PEB temperature profile1. Earlier work describes the approach to enhance post-develop CD uniformity (CDU) utilizing temperature-to-offset model in conjunction with resist CD's PEB sensitivity. Taking into consideration CD variation induced by plasma etch, we then develop a methodology to improve the post-etch poly CDU. This is done using constrained quadratic optimization techniques. Considering the fact that isolated, semi-isolated and dense lines in multiple sizes coexist on an actual chip, it is desirable to have simultaneous CDU control for isolated, semi-islolated and dense lines of various sizes. In this paper we expand our CDU control concept to simultaneous CDU control for multiple CD targets and propose the use of multi-objective and minimax optimization schemes. A combination of experimental and simulated runs is used to test this approach.
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Qiaolin Zhang, Cherry Tang, Tony Hsieh, Nick Maccrae, Bhanwar Singh, Kameshwar Poolla, and Costas J. Spanos "Comprehensive CD uniformity control across lithography and etch", Proc. SPIE 5752, Metrology, Inspection, and Process Control for Microlithography XIX, (10 May 2005);

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