Modeling of positive-tone silylation processes for 193-nm lithography

A modeling approach is presented for positive-tone silylation processes. By reducing the effect of crosslinking on diffusion of the silylating agent to a characteristic curve, the silylation profiles can be determined from aerial images. Comparisons are made to experimental profiles obtained using a scanning electron microscope and selective staining methods. Deviations from the model are observed as a function of both feature size and feature type. These discrepancies are consistent with a swelling limitation imposed by the cross-linking. By combining an anisotropic etching model with the silylation profiles, the final linewidths can be predicted as a function of dose, selectivity, and overetch.