Curvilinear data representation and its impact on file size and lithographic performance

As the industry is developing curvilinear mask solutions, some curvilinear postoptical proximity correction (OPC) masks have been reported with file sizes in excess of 10 times the corresponding Manhattan postOPC files, which can greatly impact mask data storage, transfer, and processing. Some file size reduction utilizing spline fittings has been reported in mask postprocessing. However, from an OPC perspective, mask postprocessing is undesirable. In this study, we show that maintaining an adequate density of mask control points (MCPs) is key to achieving the desired on-wafer lithographic performance, regardless of whether the MCPs are connected by spline sections or piecewise-linear segments. Our results suggest that spline-based MULTIGON records (defined by the Curvilinear Working Group convened in 2019) may not offer clear lithographic performance or file size benefits. We will also offer some guidance for controlling piecewise-linear file size without compromising lithographic performance.