Process window tripling by optimized SRAF placement rules: AP/DFM: Advanced patterning/design for manufacturability

In this paper, we show that optimized Sub-Resolution Assist Features (SRAF) placement rules nearly tripled the depth of focus of the lithography process window for the layer of interest. No SRAF printing was found in wafer SEM images. The detail of how the optimization of Rule Based SRAF (RBSRAF) was carried out is demonstrated step by step. At GLOBALFOUNDRIES, we developed a Best Known Method (BKM) for optimizing RBSRAF. This BKM uses pixelated OPC, SRAF placement rules analysis and simplification, SRAF placement parameters optimization, and SRAF Printing Avoidance. The BKM was applied to the layer of interest, and was proved to be very successful by the Fab wafer CDSEM data. The success of the RBSRAF optimization BKM will have big impact in the semiconductor manufacturing for the next generation technology nodes of 10 nm and 7 nm.