Model-based dimensional optical metrology

Jörg Bischoff; Tobias Pahl; Peter Lehmann; Eberhard Manske

doi:10.1117/12.2554517

1 April 2020 Model-based dimensional optical metrology

Jörg Bischoff, Tobias Pahl, Peter Lehmann, Eberhard Manske

Proceedings Volume 11352, Optics and Photonics for Advanced Dimensional Metrology; 113520P (2020) https://doi.org/10.1117/12.2554517
Event: SPIE Photonics Europe, 2020, Online Only

Abstract

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.

Conference Presentation

Citation Download Citation

Jörg Bischoff, Tobias Pahl, Peter Lehmann, and Eberhard Manske "Model-based dimensional optical metrology", Proc. SPIE 11352, Optics and Photonics for Advanced Dimensional Metrology, 113520P (1 April 2020); https://doi.org/10.1117/12.2554517

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