Appl Opt. 2023 Mar 20;62(9):2227-2236. doi: 10.1364/AO.482501.
Semiconductor processing is becoming more challenging as integrated circuit dimensions shrink. An increasing number of technologies are being developed for the purpose of ensuring pattern fidelity, and source and mask optimization (SMO) method has outstanding performances. In recent times, owing to the development of the process, more attention has been paid to the process window (PW). As a crucial parameter in lithography, the normalized image log slope (NILS) is strongly correlated with the PW. However, previous methods ignored the NILS in the inverse lithography model of the SMO. They regarded the NILS as the measurement index for forward lithography. This implies that the optimization of the NILS is the result of passive rather than active control, and the final optimization effect is unpredictable. In this study, the NILS is introduced in inverse lithography. The initial NILS is controlled by adding a penalty function to ensure that it continuously increases, thus increasing the exposure latitude and enhancing the PW. For the simulation, two masks typical of a 45-nm-node are selected. The results indicate that this method can effectively enhance the PW. With guaranteed pattern fidelity, the NILS of the two mask layouts increase by 16% and 9%, and the exposure latitudes increase by 21.5% and 21.7%.
随着集成电路尺寸的缩小，半导体工艺变得越来越具有挑战性。为了确保图形保真度，越来越多的技术被开发出来，源和掩模优化（SMO）方法具有出色的性能。最近，由于工艺的发展，人们越来越关注工艺窗口（PW）。作为光刻中的一个关键参数，归一化图像对数斜率（NILS）与 PW 密切相关。然而，以前的方法在 SMO 的反向光刻模型中忽略了 NILS。他们将 NILS 视为正向光刻的测量指标。这意味着 NILS 的优化是被动而不是主动控制的结果，最终的优化效果是不可预测的。在这项研究中，NILS 被引入到反向光刻中。通过添加罚函数来控制初始 NILS，以确保其不断增加，从而增加曝光宽容度并增强 PW。对于模拟，选择了两个典型的 45nm 节点掩模。结果表明，该方法可以有效地增强 PW。在保证图形保真度的前提下，两个掩模布局的 NILS 分别增加了 16%和 9%，曝光宽容度分别增加了 21.5%和 21.7%。
