Adopting curvilinear shapes for production ILT: challenges and opportunities

We have recently demonstrated that curvilinear shapes and multi-beam mask writing are necessary to minimize the impact of mask variability on wafer hotspots. Several key challenges and opportunities remain. We ask how we update mask-inspection rules, and how we correct for mask-process systematics for extreme ultraviolet (EUV), where the optical response must be taken into account. This paper proposes updated mask rule checks (MRC), derived from a mask variability perspective. We also demonstrate the need for MRC-aware inverse lithography technology (ILT) metrics as a pre-requisite to ensure the reticle shapes are what the wafer-side lithographer desires. Armed with a fully curvilinear ILT and mask data preparation (MDP) system, there is an opportunity to relax the restrictions on fully Manhattan designs where possible.