Prism spectroscopic ellipsometer

摘要

A conventional prism spectrometer is converted into a transmission spectroscopic ellipsometer (TSELL) by using the prism itself as the sample or substrate. An obliquely incident collimated broadband beam of light is dispersed by the prism into its colors, which are focused by a lens onto a linear detector array. A rotating achromatic linear polarizer is inserted in the incident beam, and a fixed linear analyzer is placed in front of the detector array. Fourier analysis of the output signal as a function of the polarizer azimuth, on a pixel-by-pixel basis, yields the transmission ellipsometric parameters ψ_t (λ) and Δ_t(λ) as functions of wavelength λ. For a given uncoated prism, the deflection angle γ(λ) and the base-line SE data of ψ_t(λ) can be inverted to yield the prism refractive index n_p(λ), or the constant coefficients of an appropriate dispersion relation for the prism material. When the prism is coated by a transparent or semitransparent thin film, the TSELL data of ψ_t(λ), Δ_t(λ) enable the determination of the thickness d and optical constants n_f(λ), k_f(λ) of the film. As an example, the potential of TSELL is illustrated using simulated TSELL spectra for a fused-silica prism that is coated with a ZnS film.