Constrained MRC Approaches for Inverse Lithography

The dramatically evolved optical proximity correction (OPC) in lithographic process and mask manufacturing is requiring the notion and practice of curvy features in industry to improve printability and pattern fidelity. However, the pragmatic manufacturability of curvy features requires reliable mask rule checks (MRCs), as a consequence, addressing MRC violations is critical in optical proximity correction (OPC) engines. In this paper, we propose a constrained approach for curvy feature MRC compliance where a skeleton-distance map-based method is implemented for MRC violation detection and correction, and a mask rule penalty term per correction with the mask contour as a distance indicator is incorporated into the level-set based optimization process to avoid local rule-violation level-set evolution. Simulation results demonstrate that the constrained approach penalizes the occurrence of mask rule violations and resolve MRC violations without degrading imaging performance.