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Generating curvilinear mask shapes in OPC instead of pure rectangular shapes is becoming more and more realistic as a method for improving wafer lithography performance. The main benefit of using curvilinear shapes is an improved process window, meaning that the wafer image is less sensitive to dose and focus conditions during the exposure. With the increased compute power of latest High-Performance-Clusters (HPC) and the availability of Multi-Beam-Mask-Writers (MBMW) those wafer lithography benefits can be realized at technology nodes currently being developed. A very practical challenge for putting masks with curvilinear shapes in production is the availability of reliable Mask- Rule-Checks (MRC). The OPC engine not only needs to generate shapes which are manufacturable, the mask shop also needs a method of verifying that incoming mask data is manufacturable. For curvilinear mask shapes this is more challenging than for rectangular mask shapes, since simple width and space checks as used for rectangular masks are not sufficient anymore. In this paper, a comprehensive set of MRC limits is being discussed and the effectiveness of an MRC engine operating on curvilinear input data is demonstrated. Rules used here include minimum width of exposed features, minimum space between exposed features, minimum curvature of convex and concave shapes, as well as minimum area of exposed features.
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