A Novel OPC Method Based on Pattern Density

Traditional OPC is based on the assumption of stable lithography process with low correlation to pattern density. Normally it is accurate enough for generic IC layout. But it will depart from model prediction if the layout pattern density cannot be controlled well such as GPU/RF/CIS devices. In this paper we will demonstrate the pattern density induced OPC miss-match with traditional OPC in special IC layout. A novel OPC method with separated SSA table for different pattern density is introduced to reduce the pattern density impact and improve OPC accuracy at extreme high or low pattern density cases.