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Influence of thermal load on 450 mm Si-wafer IPD during lithographic patterning

We report on Finite Element Modeling (FEM) of the influence of heat load due to the lithographic exposure on the inplane distortion (IPD) of 450 mm Si-wafers and hence on the effect of the heat load on the achievable image placement accuracy. Based on a scenario of electron beam writing at an exposure power of 20 mW, the thermo-mechanical behavior of the chuck and the attached Si wafer is modeled and used to derive corresponding IPD values. To account for the pin structured chuck surface, an effective layer model is derived. Different materials for the wafer chuck are compared with respect to their influence on wafer IPD and thermal characteristics of the exposure process. Guidelines for the selection of the chuck material und suggestions for its cooling and corrective strategies on e-beam steering during exposure are derived.