Zhang Jinsong, Liu Jiamin, Zhu Jinlong, Jiang Hao, Liu Shiyuan
Appl Opt. 2023 May 20;62(15):3829-3838. doi: 10.1364/AO.477682.
Due to the advantages of being non-contact, non-destructive, highly efficient, and low in cost, scatterometry has emerged as a powerful technique for nanostructure metrology. In this paper, we propose an angle-resolved scatterometer composed of a scattered light acquisition channel and a spatial imaging channel, which is capable of detecting multi-order diffracted light in a single measurement. Since the high numerical aperture objective lens is usually employed in an angle-resolved scatterometer, the polarization effect of the objective lens introduced by the non-normal incidence and installation stress should be considered. An in-situ calibration method for the objective lens's polarization effects is proposed, in which a known analyzer is appended to the output light path to enable the extraction of the ellipsometric parameters of isotropic samples. Then the polarization effect of the objective lens can be determined in-situ by fitting the measured ellipsometric parameters to the calculated ones. With the objective lens polarization effect being considered, significant improvements in the accuracy and repeatability precision can be achieved in the metrology of the film thickness and grating topography parameters.
由于具有非接触、无损、高效和低成本等优点，散射测量法已成为一种用于纳米结构计量的强大技术。在本文中，我们提出了一种由散射光采集通道和空间成像通道组成的角分辨散射仪，它能够在单次测量中检测多阶衍射光。由于角分辨散射仪通常采用高数值孔径物镜，因此应考虑非垂直入射和安装应力所引入的物镜偏振效应。提出了一种物镜偏振效应的原位校准方法，即在输出光路上附加一个已知的分析器，以提取各向同性样品的椭偏参数。然后，通过将测量的椭偏参数与计算得到的参数进行拟合，可原位确定物镜的偏振效应。考虑物镜偏振效应后，在膜厚和光栅形貌参数的计量中，精度和重复性精度可得到显著提高。
