RuleLearner: OPC Rule Extraction From Inverse Lithography Technique Engine

Model-based optical proximity correction (OPC) with subresolution assist feature (SRAF) generation is a critical standard practice for compensating lithography distortions in the fabrication of integrated circuits at advanced technology nodes. Typical model-based OPC and SRAF algorithms involve the selection of user-controlled rule parameters. Conventionally, these rules are heuristically determined and applied globally throughout the correction regions, which can be time consuming and require expert knowledge of the tool. Additionally, the correlations of rule parameters to the objectives are highly nonlinear. All these factors make designing a high-performance OPC engine for complex metal designs a nontrivial task. This article proposes RuleLearner, a comprehensive mask optimization system designed for SRAF generation and model-based OPC in real industrial scenarios. The proposed framework learns from the guidance of an information-augmented inverse lithography technique engine, which, although expressive for complex designs, is expensive to generate refined masks for a whole set of design clips. Considering the nonlinearity and the tradeoff between local and global performance, the extracted rule value distributions are further optimized with customized natural gradients. The sophisticated SRAF generation, the edge segmentation and movements are then guided by the rule parameter. Experimental results show that RuleLearner can be applied across different complex design patterns and achieve the best lithographic performance and computational efficiency.