Model-based dimensional optical metrology
Model-based dimensional optical metrology
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基于模型的尺寸光学计量
DOI：
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发表时间：
2020
期刊：
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通讯作者：
E. Manske
中科院分区：
文献类型：
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作者：
J. Bischoff;T. Pahl;P. Lehmann;E. Manske
基于模型的尺寸计量方法在精度方面具有很大的潜力。在某些情况下，它们甚至可以帮助克服经典的分辨率标准。一个著名的例子是用于测量半导体芯片在十纳米范围内的关键尺寸的光学散射测量法。基本上，这些技术依赖于反问题的解决，即从信号中检索被测量的剖面，例如光学散射测量中的光谱。在这里，模型的适当性和准确性对于实现定量计量的目标至关重要。另一方面，实现的模型应该为实际应用程序提供快速的周转周期。因此，较长的计算时间和巨大的内存消耗是难以接受的。我们研究并比较了两种同样成熟的光学剖面技术——激光聚焦扫描（LFS）和相干扫描干涉测量（CSI）——在不同情况下与应用相关的模型复杂性和严密性。特别考虑了两种电磁衍射方法：有限元法和模态法。一般来说，与基于解析近似的方法相比，严格的方法是相当昂贵和耗时的。特别是，完整的3D模型需要巨大的努力和计算资源。因此，本文将讨论一些替代方法，如降维和其他各种加速方法，如对称使用和MM。此外，比较了不同的方法，并得出了它们在CSI和LFS中的实际适用性的结论。
Model based approaches in dimensional metrology have great potential in terms of better accuracy. In some cases they may even help to overcome classical resolution criteria. A famous example is optical scatterometry for measuring critical dimensions on semiconductor chips in the tenth-nanometer range. Basically, these techniques rely on the solution of the inverse problem, i.e. retrieve the measured profile from a signal, e.g. a spectrum in optical scatterometry. Here, the appropriateness and accuracy of the model is of great importance to achieve the goals of quantitative metrology. On the other hand, the implemented models shall enable fast turnaround cycles for practical applications. Thus, long computation times and huge memory consumption can hardly be accepted. We investigate and compare different scenarios of model complexity and rigorousness related to application in two likewise well-established optical profiling techniques, laser focus scanning (LFS) and coherence scanning interferometry (CSI). Especially, two electromagnetic diffraction methods are considered, Finite Element Method (FEM) and Modal Methods (MM). In general, rigorous methods are rather expensive and time consuming compared to methods based on analytical approximations. Particularly, full 3D models require huge efforts and computing resources. Thus, some alternatives shall be discussed in this paper such as reduction of dimensionality and various other methods for acceleration such as symmetry usage and for MM. Moreover, the different approaches are compared and conclusions are drawn with respect to their practical applicability in both, CSI as well as LFS.