Meng Kai, Hu Daiyi, Wang Kai, Zhang Hangying, Lu Jiahao, Lou Peihuang, Cao Kuikang
Opt Express. 2025 Mar 24;33(6):13358-13375. doi: 10.1364/OE.553377.
Overlay metrology is critical for the management and control of the lithography quality in semiconductor manufacturing. In industrial applications, the empirical DBO (diffraction-based overlay) method based on differential signals is one of the main techniques for this task. However, how to select and identify an overlay indicator with good linearity, sensitivity, and robustness for a wide overlay range is the key challenge for constructing the empirical DBO formulations. In this work, we propose what we believe to be a new overlay indicator based on the polarization eigenstate of the retardance Mueller matrix for ellipsometry-based overlay metrology. The general property requirements and optimization mechanism for the overlay indicator selection are also theoretically analyzed and discussed. Then, the effectiveness of the proposed method is validated by both simulations and experiments. Compared to the existing Mueller matrix-based indicators, the results prove that our method shows better accuracy and robustness for the typical double-layer-grating overlay targets. This work can provide a theoretical basis for the DBO indicator design as well as a potentially new tool for the overlay metrology practice.
重叠计量对于半导体制造中光刻质量的管理和控制至关重要。在工业应用中，基于差分信号的经验性DBO（基于衍射的重叠）方法是完成这项任务的主要技术之一。然而，如何在宽重叠范围内选择和识别具有良好线性、灵敏度和鲁棒性的重叠指标是构建经验性DBO公式的关键挑战。在这项工作中，我们提出了一种基于用于椭偏仪重叠计量的延迟穆勒矩阵偏振本征态的新型重叠指标。还从理论上分析和讨论了重叠指标选择的一般性能要求和优化机制。然后，通过模拟和实验验证了所提方法的有效性。与现有的基于穆勒矩阵的指标相比，结果证明我们的方法对于典型的双层光栅重叠目标具有更高的精度和鲁棒性。这项工作可为DBO指标设计提供理论基础，并为重叠计量实践提供一种潜在的新工具。
