Optics: measuring and testing – Of light reflection
Patent
1999-06-15
2000-05-02
Kim, Robert H.
Optics: measuring and testing
Of light reflection
356361, G01N 2155
Patent
active
060579285
ABSTRACT:
A non-contact method for determining the index of refraction or dielectric constant of a thin film on a substrate at a desired frequency in the GHz to THz range having a corresponding wavelength larger than the thickness of the thin film (which may be only a few microns). The method comprises impinging the desired-frequency beam in free space upon the thin film on the substrate and measuring the measured phase change and the measured field reflectance from the reflected beam for a plurality of incident angles over a range of angles that includes the Brewster's angle for the thin film. The index of refraction for the thin film is determined by applying Fresnel equations to iteratively calculate a calculated phase change and a calculated field reflectance at each of the plurality of incident angles, and selecting the index of refraction that provides the best mathematical curve fit with both the dataset of measured phase changes and the dataset of measured field reflectances for each incident angle. The dielectric constant for the thin film can be calculated as the index of refraction squared.
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Cho Gyu Cheon
Li Ming
Zhang Xi-Cheng
Kim Robert H.
Natividad Phil
Rensselaer Polytechnic Institute
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