Instead of using the inverse lithography technology (ILT) flow that allows for unrestricted shapes and widths of sub-resolution assist features (SRAFs), Y. Xu et al. propose an alternative approach. This method involves the direct specification of width, curvature, and minimal area to generate constant width curvilinear SRAFs. The study described in Ref. 1 demonstrates several advantages associated with constant width curvilinear SRAFs compared to their freeform counterparts. The advantages include improved compliance with manufacturing rule check (MRC) requirements, mitigation of SRAF printing issues, compatibility with the tile boundary stitching, enhanced runtime robustness, and better control over data volume. In the field of mask process correction (MPC), it is worth examining the potential advantages offered by constant width curvilinear SRAFs. Since all SRAFs must be printed on the mask but not on the wafer during the manufacturing process, the goal of MPC is the same for main features and SRAFs, aiming to ensure that patterns on the fabricated masks align precisely with target shapes and minimize edge placement errors (EPEs). This paper presents a comprehensive study of MPC accuracy and runtime performance when employing constant width SRAFs as input. A comparative analysis is conducted against the use of freeform SRAFs. Various MPC approaches, such as shape-based and dose-based corrections, treating SRAFs as a visible layer without edge bias, curvature-based prebias (CBB), and curvature-based fragmentation (CBF) are explored. The findings of this study provide valuable guidance for the generation of masks with constant width curvilinear SRAFs.
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