CONSTRUCTION AND PERFORMANCE OF A FOURIER-TRANSFORM INFRARED PHASE-MODULATED ELLIPSOMETER FOR IN-PROCESS SURFACE DIAGNOSTICS

A Fourier-transform infrared phase-modulated spectroscopic ellipsomete r (FT-IR PMSE) has been constructed by insertion of a grid polarizer a s an analyzer in front of an infrared detector in addition to a conven tional setup for phase-modulated reflection absorption spectroscopy (P MRAS). Although ellipsometric parameters Psi and Delta are subject to the effect of mirrors placed between a photoelastic modulator and the analyzer, this can be canceled out in the derivation of optical densit y of the measured surface. The performance of the ellipsometer has bee n demonstrated in the characterization of thermally oxidized Si surfac es. It is shown that the imaginary part of the optical density spectru m has a higher signal-to-noise ratio than the real part, which corresp onds to the spectrum obtained by PMRAS, and a linear relationship with SiO2 thickness. By this method the presence of a fluorinated layer ha s been detected on CF4 plasma-treated Si surface.