Modeling polarized illumination for OPC/RET

Abstract

Recent research has shown that properly polarized light source enhances image contrast in photolithography for manufacturing integrated circuit (IC) devices, thus improves the effectiveness of optical proximity correction (OPC) and other resolution enhancement techniques (RET). However, current OPC/RET modeling software can only model the light source polarization of simple types, such as TE, TM, X, Y, or sector polarization with relatively simple configuration. Realistic polarized light used in scanners is more complex than the aforementioned simple ones. As a result, simulation accuracy and quality of the OPC result will be compromised by the simplification of the light source polarization modeling in the traditional approach. With ever shrinking CD error budget in the manufacturing of IC's at advanced technology nodes, more accurate and comprehensive light source modeling for lithography simulations and OPC/RET is needed. In this paper, we present a modeling framework that takes arbitrarily polarized light source. Based on polarization state vector descriptions of the light source, it unifies optical simulations of unpolarized, partially polarized, and completely polarized illuminations. We built this framework into Synopsys' OPC modeling tool ProGen. Combined with ProGen's existing capability to handle vectorial aberration by the projection lens, large angle effects due to high NA, and thin film effects, this framework represents a general vectorial model for optical imaging with the state-of-the-art scanners. Numerical experiments were performed to study CD impact of various illumination polarization modeling schemes in the context of OPC/RET.