用赛德尔像差理论求解极紫外光刻物镜初始结构的方法
The method of solving initial structure by Seidel aberration theory for extreme ultraviolet lithography objective
摘要：
提出了一种基于赛德尔像差理论的近轴光线追迹算法求解极紫外光刻离轴多镜系统初始结构的方法。通过追踪反射系统中的特征光线，得到各表面的高度和近轴角，再通过赛德尔像差系数与这些参数之间的关系，求解出具有良好像差性能的初始结构。我们可以通过添加不同的初始条件约束来获得不同的初始结构。本文通过分配不同的光功率作为不同的初始结构，求解了两种不同的初始结构，并在此基础上优化了两个数值孔径为0.25的离轴六镜系统。它们的波前像差RMS值约为0.04波长，绝对畸变小于1.2nm，具有良好的成像质量。我们相信该方法可以大大提高复杂多镜系统的设计效率和优化效果。
英文摘要：
In this paper, a method for solving the initial structure of an off-axis multi-mirror system applied to extreme ultraviolet (EUV) lithography using a paraxial ray-tracing algorithm based on Seidel aberration theory is proposed. By tracing the characteristic rays in the reflection system, the height and paraxial angle on each surface can be obtained, then through the relationship between the Seidel aberration coefficient and these parameters, the initial structure with good aberration performance can be solved. We can obtain different initial structures by adding different initial condition constraints. In this paper, we have solved two different initial structures by assigning different optical powers as different initial structures, and on this basis, we have optimized two off-axis six-mirror systems with numerical aperture (NA) of 0.25. Their wavefront aberration RMS value is about 0.04 wavelength, and the absolute distortion is less than 1.2nm, with good imaging quality. We believe that this method can greatly improve the design efficiency and optimization effect of complex multi-mirror systems.
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