Infrared phase-modulated ellipsometer for in-situ characterization of surfaces and thin films

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Abstract
A new infrared phase modulated ellipsometer (IRPME) is presented here. The polarization phase modulation technique takes advantage of the high frequency modulation (37 kHz) provided by a ZnSe photoelastic modulator. In order to increase the signal to noise ratio, the conventional globar source was superseded by a cascade arc, which emitted intensity corresponds to that of a blackbody at a temperature > 10,000 K. Ellipsometric measurements can be recorded from 700 up to 4000 cm-1 combining photovoltaic InSb and MCT detectors. A monochromator is used to record spectra, with a 2 - 5 cm-1 spectral resolution, depending on the wavelength domain. The signal acquisition and data processing is based on the use of a numerical electronic system. The improvements of both optical and electronic parts of the ellipsometer result in increased performances by more than one order of magnitude. The precision on (Psi) and (Delta) is now approximately equals 0.01 deg., achieving a submonolayer sensitivity.

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