Fracturing-aware Curvilinear ILT via Circular E-beam Mask Writer

Inverse lithography technology (ILT) plays a crucial role in optical proximity correction, tending to generate curvilinear masks for optimal process windows. Traditional curvilinear mask manufacturing involves fracturing into rectangles, requiring expensive mask write times. A novel E-beam mask writer that writes variable radius circles per shot significantly reduces the shot count for curvilinear masks. To exploit this mask writer's benefits, we present two methods to generate circular fracturing-aware masks. The first one converts pixel-based masks from existing ILT methods into circle-based masks using predefined rules. The second one integrates circular constraints into the ILT process, generating circle-based masks directly via optimization. Extensive experimental results validate both approaches' effectiveness.