Measurement of Steep Surfaces Using White Light Interferometry
Measurement of Steep Surfaces Using White Light Interferometry
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DOI：
10.1111/j.1475-1305.2008.00595.x
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发表时间：
2010-02
期刊：
影响因子：
2.1
通讯作者：
J. Coupland;J. Lobera
中科院分区：
文献类型：
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作者：
J. Coupland;J. Lobera
翻译后摘要：扫描白色光干涉（SWLI）是一种越来越流行的方法来测量微型元件的表面轮廓。虽然它可以承受轮廓的阶跃变化，但它测量大表面梯度的能力是有限的，而大表面梯度是高纵横比表面的特征。这部分是由于物镜透镜的数值孔径限制了照明和记录场的空间频率含量。然而，更基本的是，SWLI仪器忽略了多次散射的影响，并假设照亮物体的场是如果物体不存在时存在的场。虽然这是一个合理的近似缓慢变化的表面，它通常是不正确的那些陡峭的梯度。本文介绍了SWLI的三维理论，并在此背景下讨论了目前仪器所作的近似。使用有限元方法（FEM），计算SWLI干涉图，对于2D硅V形槽和台阶伪影的情况，并说明多次散射的影响。介绍了提高SWLI测量大表面梯度的能力的方法，首先通过倾斜样品，随后通过使用迭代FEM模型来提供对照明条件的改进估计。
Abstract: Scanning white light interferometry (SWLI) is an increasingly popular method to measure the surface profile of miniature components. Although it is tolerant to step changes in profile, its capability to measure the large surface gradients that are characteristic of high‐aspect‐ratio surfaces is limited. This is in part due to the numerical aperture of the objective lens which restricts the spatial frequency content of both the illumination and recorded fields. More fundamentally, though, SWLI instrumentation neglects the effects of multiple scattering and assumes that the field which illuminates the object is that which would be present if the object were absent. Although this is a reasonable approximation for slowly varying surfaces, it is generally not true for those with steep gradients. In this paper the 3D theory of SWLI is presented and the approximations made by current instrumentation are discussed in this context. Using finite element methods (FEM), SWLI interferograms are calculated, for the cases of 2D Silicon V‐grooves and step artefacts, and the effects of multiple scattering are illustrated. Methods to improve the capability of SWLI to measure large surface gradients, first by tilting the sample and subsequently by using an iterative FEM model to provide improved estimates of the illuminating conditions are introduced.