Modified optical proximity correction model to compensate pattern density induced optical proximity effect

As design rule is decreased, OPC accuracy has become the crucial factor for achieving stable device functionality and yield. Usually the lithography and the etching process conditions are main parameters impacting to the OPC accuracy. The OPC accuracy can be changed as function of process conditions, even if we use same OPC model. And we usually expect to obtain same OPC results between different devices in same technology node if we used same OPC model and process. But we observed different OPC results as function of devices as well as process conditions. We suspected this phenomenon was resulted from the different pattern density induced global etch bias variation. First of all, we will prove that the device dependency of OPC accuracy is come from pattern density induced etch bias effect. Finally, we will setup new OPC methodology to compensate this effect.