Full-chip OPC treatment using vector thin film models

Decreasing k1 factors require improved empirical models for full-chip OPC treatment. We have investigated the improvement in calibrating experimental data using a vector thin film compared to a scalar optical model. This optical model was first compared to a commercially available resist simulator with good results. In the OPC tool used, the predicted aerial image is further modified by a variable threshold process model describing resist effects. A number of parameters in the optical portion of the model were varied to improve the final fit including focus, sigma, diffusion, pupil apodization, spherical aberration, and thin film stack parameters. It was found that the goodness of fit for the entire model (optical + process) was significantly improved (for both scalar and vector models) when diffusion and apodization were employed. The goodness of fit for the vector model was quite sensitive to stack parameters, especially the index and absorption values of both the resist and BARC. A preliminary optimization using the vector model resulted in a fit at least as good as that for the scalar model, and slightly better in defocus.