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The rapidly increasing complexity of photomasks arising from free-form curvilinear mask shapes generated by Inverse Lithography Technology (ILT) has called for exploration of efficient and accurate native curvilinear data representation methodologies. The curvilinear Multigon extension to SEMI P39 OASIS format has been approved as a preliminary standard for the industry to evaluate Multigon-based post-tape-out data preparation flows. In this paper, we will present perspectives on opportunities, challenges, and applications of Multigon-based curvilinear data handling and representation. The representation of a closed curvilinear shape using multiple explicit or implicit Piecewise-Bèzier (PWB) curves will be described, including considerations for ensuring continuity of curves between neighboring Bèziers. A description of useful Multigon properties will be provided, which enables the development of operations fundamental to Computational Lithography, thereby enabling ‘native’ Multigon-based flows. PiecewiseBèzier to Piecewise-Linear (PWL) sampling methods (based on specified quantitative constraints) will be presented as an approach to convert PWB data to edge-based polygon representation such that PWB-based tools can be integrated and tested even in flows where certain components require operations on PWL data. Further, potential approaches, benefits and challenges related to development of Multigon-based data preparation flows will be discussed in the context of Optical Proximity Correction (OPC), Mask Process Correction (MPC) and multibeam mask writer data preparation. Finally, initial results on demonstrating curvilinear MRC (Mask-Rule-Check) on PWB data will be presented.
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