1 December 1990 Interaction between dispersive and inhomogeneous models for interpreting spectral ellipsometric data of thin films
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Abstract
Spectral ellipsometric data taken on thin-film samples are often used to obtain optical properties of the thin-film materials. A homogeneous model is usually used for the films and a dispersive refractive index is varied to fit the data. Often the data do not fit a homogeneous model. In this case the film is modeled by one or more layers to approximate an inhomogeneous film. A common procedure is to fix the dispersion curve for the film material and to model the indices of the various layers with density or porosity as the adjustable parameter. This paper demonstrates that dispersion and film inhomogeneity can affect ellipsometric data in a similar fashion in certain spectral regions. Thus, the dispersion curve derived using a homogeneous film model may be in error due to inhomogeneities in the film. An example is presented for a silica (SiO2) film on a silicon (Si) substrate. Ellipsometric data are calculated using handbook values for the refractive indices of the materials, but for an inhomogeneous silica film. These data are analyzed using a homogeneous film with a variable Cauchy dispersion equation. The best-fit dispersion curve is found to deviate significantly from the handbook data for silica.
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Charles K. Carniglia, Charles K. Carniglia, Karl N. Schrader, Karl N. Schrader, } "Interaction between dispersive and inhomogeneous models for interpreting spectral ellipsometric data of thin films", Proc. SPIE 1324, Modeling of Optical Thin Films II, (1 December 1990); doi: 10.1117/12.22419; https://doi.org/10.1117/12.22419
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