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Quantitative characterization and modeling of sub-bandgap absorption features in thin oxide films from spectroscopic ellipsometry data

1 GLOBALFOUNDRIES Dresden Module One LLC & Co. KG, Wilschdorfer Landstr. 101, D-01109 Dresden, Germany;
2 KLA-Tencor Corp., One Technology Drive, Milpitas, CA 95035, U.S.A.

Special Issues: Multifunctional Oxide Materials

Analytic representations of the complex dielectric function, which describe various types of materials, are needed for the analysis of optical measurements, in particularly, ellipsometric data. Here, we examine an improved multi-oscillator Tauc-Lorentz (TL) model with a constraint on the band-gap parameter Eg, which forces it to be common for all TL oscillators, and possibility to represent reasonably weak absorption features below the bandgap by inclusion of additional unbounded Lorentz and/or Gaussian oscillators with transition energies located below Eg. We conclude that the proposed model is the most appropriate for the characterization of various materials with sub-band absorption features and provides meaningful value for the energy bandgap. A few examples to illustrate the use of modified model have been provided.
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