An Investigation on OPC Model Coverage to Improve CD Uniformity

Abstract

Model-based Optical Proximity Correction (model-based OPC) has become a necessity for state of the art IC fabrication at advanced node technology. It needs one “reliable” OPC model for successful application of model-based OPC. Namely, the reliable OPC model needs to have much wider coverage and high accuracy to characterize the physical processes that take place during the photoresist exposure and development. One of the key factors for reliability of OPC model is model coverage which depends strongly on test pattern samples for model calibration. In this paper, two sets of test structures were selected to do OPC model calibration to qualify CD uniformity of patterns in array structures at 3xnm technology node. The results show the intermediate number of features for a given pitch is necessary for wider coverage of OPC model. The model including such patterns can improve CD uniformity of array structure. One methodology to design optimal permutation and combination for test patterns is proposed.