Cheng Wei, Li Sikun, Wang Xiangzhao, Zhang Zinan
Appl Opt. 2022 May 20;61(15):4437-4448. doi: 10.1364/AO.458059.
Extreme ultraviolet (EUV) multilayer defects result in the degradation of through-focus imaging quality. The optical proximity effect is another crucial factor that degrades the imaging quality. Both the impacts of the defects and the optical proximity effects could be mitigated by modifying the original mask patterns. A heuristic-based defect compensation method considering optical proximity correction and through-focus optimization is proposed in this paper. The edge of the mask pattern and the insertion of sub-resolution assist features (SRAFs) are optimized by covariance matrix adaptation evolution strategy (CMA-ES) to compensate for the degradation of the imaging quality with a certain defocus range. New encoding strategies for the edge pixels of the mask pattern and the SRAFs are proposed and utilized in this paper to ensure the manufacturability of the mask and the efficiency of the optimization at the same time. The rigorous database approach based on the scattering matrix is adopted to simulate the mask diffraction spectrum efficiently. Simulations verify that the through-focus imaging quality of both the defective masks with bump defects and pit defects could be obviously improved by the proposed defect compensation method.
极紫外（EUV）多层膜缺陷会导致全聚焦成像质量下降。光学邻近效应是另一个降低成像质量的关键因素。通过修改原始掩模图案，可以减轻缺陷和光学邻近效应的影响。本文提出了一种基于启发式的缺陷补偿方法，该方法考虑了光学邻近校正和全聚焦优化。通过协方差矩阵自适应进化策略（CMA-ES）对掩模图案的边缘和亚分辨率辅助特征（SRAF）的插入进行优化，以补偿在一定离焦范围内成像质量的下降。本文提出并采用了掩模图案边缘像素和SRAF的新编码策略，以同时确保掩模的可制造性和优化效率。采用基于散射矩阵的严格数据库方法来高效模拟掩模衍射光谱。仿真验证了所提出的缺陷补偿方法可以显著提高具有凸点缺陷和凹坑缺陷的缺陷掩模的全聚焦成像质量。
