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20 March 2006 Building a computational model for process and proximity compensation
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Abstract
Computational models used in process proximity correction require accurate description of lithography and etch processes. We present inversion of stepper and photoresist parameters from printed test structures. The technique is based on printing a set of test structures at different dose and defocus settings, and processing the CD-SEM measurements of the printed test structures. The model of image formation includes: an arbitrary pupil illumination profile, defocus bias, flare, chromatic aberrations, wavefront errors and apodization of the lens pupil; interaction of vector EM waves with the stack of materials on the wafer; and molecular diffusion in photoresist. The inversion is done by minimizing a norm of the differences between CDs calculated by the model and CD-SEM measurements. The corresponding non-linear least square problem is solved using Gauss-Newton and Levenberg-Marquardt algorithms. Differences between the CD measurements and the best fitting model have an RMS error of 1.63 nm. An etch model, separate from the lithography model, is fitted to measurements of etch skew.
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Gökhan Perçin, Hsu-Ting Huang, Franz X. Zach, Apo Sezginer, and Ali Mokhberi "Building a computational model for process and proximity compensation", Proc. SPIE 6154, Optical Microlithography XIX, 61543N (20 March 2006); https://doi.org/10.1117/12.656501
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