Metal layer PWOPC solution for 28nm node and beyond

At advanced node of metal layer, defocus conditions need to be taken into account in OPC in order to guarantee metal layer process window. Process window OPC (PWOPC) must be considered for the model-based OPC models under special conditions within a lithographic process window. In this paper, we studied several OPC simulation issues in the application of PWOPC in metal layer. The test run results showed that preparatory work and parameters setting were very important for PWOPC application. Without preparatory work or unbefitting parameters setting, the OPC simulation may lead to undesired results. The depth of focus (DOF) of several hot spots was examined. The pinch and bridge error are hot spots while only OPC model under nominal conditions is employed. These hot spots can be resolved while PWOPC models are in consideration. In addition of PWOPC precision study, PWOPC runtime is also evaluated. The use of PWOPC extends OPC runtime at least 50%, which is unacceptable in the environment of longer OPC runtime for the advanced tech node and continuing pull-in tapeout schedule. The runtime speeding up method is studied to reduce the total runtime.