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Accuracy of current model descriptions of a DUV photoresist

This paper describes the development of a lithographic model for Shipley UV6 DUV photoresist from fundamental materials constants. Parameters describing optical absorbance, acid generation, acid generation, acid diffusion, resin deprotection, and resists dissolution rate were measured and input into PROLITH/2. Initial simulations showed significant deviations from observed lithographic performance. Simulated E0 swing curves showed a large bulk effect absent in experiment data. Simulated lines showed excessive top loss and tapering which were corrected by the artificial introduction of a surface base contaminant. Lithographic process windows for lines and contacts cold be successfully simulated after considerable adjustment of the acid diffusion coefficient and development parameters, but accurate simulation of both profile and process window with a single set of parameters was only possible for contacts. The manipulations required to match simulated and experimental data did lead to some insights into resists materials design. Simulations suggest that lowering acid diffusion should increase exposure latitude and reduce film thickness loss, while suppressing the resist dissolution rate at the onset of deprotection should improve both focus and exposure latitude.