Iterative method for in situ measurement of lens aberrations in lithographic tools using CTC-based quadratic aberration model.
Iterative method for in situ measurement of lens aberrations in lithographic tools using CTC-based quadratic aberration model.
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DOI：
10.1364/oe.20.014272
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发表时间：
2012-06
期刊：
影响因子：
3.8
通讯作者：
Shiyuan Liu;Shuang Xu;Xiaofei Wu;W. Liu
中科院分区：
文献类型：
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作者：
Shiyuan Liu;Shuang Xu;Xiaofei Wu;W. Liu
本文提出了一种基于二次像差模型（QAM）的光刻工具中原位透镜像差测量的迭代方法，该模型是考虑各个泽尼克系数之间的相互作用而形成的线性模型的自然扩展。通过引入称为交叉三重相关（CTC）的广义算子，借助快速傅立叶变换（FFT）可以非常快速且准确地计算二次模型。高达 37 阶甚至更高阶的 Zernike 系数是通过根据专门设计的掩模图案的多个离焦航空图像通过迭代过程解决反演问题来确定的。仿真工作验证了理论推导，并证实这种方法易于实现，并且可以产生高质量的波前估计，特别是对于像差相对较大的情况。完全期望该方法将为光刻工具成像质量的在线监测提供有用的实用手段。
This paper proposes an iterative method for in situ lens aberration measurement in lithographic tools based on a quadratic aberration model (QAM) that is a natural extension of the linear model formed by taking into account interactions among individual Zernike coefficients. By introducing a generalized operator named cross triple correlation (CTC), the quadratic model can be calculated very quickly and accurately with the help of fast Fourier transform (FFT). The Zernike coefficients up to the 37th order or even higher are determined by solving an inverse problem through an iterative procedure from several through-focus aerial images of a specially designed mask pattern. The simulation work has validated the theoretical derivation and confirms that such a method is simple to implement and yields a superior quality of wavefront estimate, particularly for the case when the aberrations are relatively large. It is fully expected that this method will provide a useful practical means for the in-line monitoring of the imaging quality of lithographic tools.