Lithographic exposure latitude aware source and mask optimization

Abstract

Source and mask optimization (SMO) technology is an increasingly important resolution enhancement technology (RET) that can optimize the source and mask. Various SMO methods have made great progress in terms of computational efficiency and pattern fidelity. Besides, process window (PW) is also an important indicator to evaluate the performance of lithography imaging. PW consists of exposure latitude (EL) and depth of focus (DOF). However, currently, there are few SMO methods that can directly improve EL. In this paper, we propose an EL aware SMO (ELASMO) method by innovating a new penalty function for improving the exposure latitude. Compared to the conventional SMO, the proposed ELASMO can significantly enhance aerial image contrast and enlarge the exposure latitude from 5% to 11% under the premise of ensuring imaging fidelity. ELASMO achieves high-fidelity lithography in a larger process window.