Informatics-based computational lithography for phase-shifting mask optimization

Abstract

Phase-shifting mask (PSM) is widely used in semiconductor fabrication to improve the resolution and image fidelity of optical lithography process. However, the theoretical image fidelity limit of the PSM lithography process is not fully understood. In this paper, the information transmission mechanism of PSM layout in optical lithography system is unveiled from the perspective of information theory. First, an information channel model is established to depict the information transfer of PSM layout in optical lithography system. Based on the law of information entropy, the optimal mutual information (OMI) of the PSM lithography process is derived, and the theoretical lower bound of the PSM image error is obtained. Finally, an informatics-based computational lithography approach is proposed to optimize the PSM, which achieves higher image fidelity compared to the traditional optimization algorithm. The benefit of PSM over the binary lithography mask is also discussed from the information theoretical aspects.