Study of OPC accuracy by illumination source types

Abstract

The study of OPC (Optical Proximity Correction) model that well predict the wafer result has been researched. As the pattern design shrink down, the need for the CD (Critical Dimension) controllability increased more than before. To achieve these requirements, OPC models must be accurate for full chip process and model inaccuracies are one of several factors which contribute to errors in the final wafer image. For that reason, robust OPC using real lithographic terms was proposed. Real lithographic system is quite different from ideal system that is used for OPC modeling. Until now, this difference was acceptable since pattern size used for OPC model was large, but as device size shrinks, this gap between ideal and real system causes degradation of OPC accuracy. So, various optical parameters such as apodization, laser band width, degree of polarization, illumination are used today in order to compensate for this issue. Especially, major issue in modeling error is related to how the illumination source is used.For this study we assess accuracy of optical model for robust OPC using ideal and actual illumination sources, and test conditions are below. 1) We examined the difference of pupil types to output model respectively.2) A parameterized test pattern layout was used by 1D test pattern types that have various lines and spaces. 3) All models were calculated in automation method so as to exclude the dependency of user skills. 4) OPC accuracies were examined by gate layer patterns on full chip level. The study is performed for 5X~4Xnm nodes lithographic processes. The main focus of the study was on usability of model that is made by measured source data in semiconductor manufacturing. Results clearly showed that the actual source for the optical model has merits and demerits.

The impacts of scanner modeling parameters for OPC model of sub-40nm memory device

“…But, the wafer CD measurement value is definitely different. 5 The old parameters of pupil shape are not able to distinguish between top hat shape and asymmetric diffused illumination source shape from DOE system, thus EDA company try to fit several parameters (like NA, Sigma in/out, and side slope) in order to make more accurate OPC model. The other approach of pupil shape compensation is usage of real measured source shape in modeling.…”