Exploration of resist effect in source mask optimization

The resist effect may have a significant impact on source mask optimization (SMO), because the CD change in response to dose, defocus and mask size variations can be substantially modified by the resist effect. In this paper, we elaborate on how the resist effect, represented by compact resist models, changes the cost function of SMO and affects the optimized source shapes and the corresponding lithographic performance. Based on the results, we present the guidelines of using compact resist models in SMO, especially for the case of the negative tone development (NTD) process.