2-CHANNEL POLARIZATION MODULATION ELLIPSOMETER

A new wavelength-scanning two-channel polarization modulation ellipsometer is described, where a photoelastic modulator is used and the analyzed light is separated into orthogonally polarized beams using a Wollaston prism. Both beams are detected using phototubes whose bias voltage is dynamically controlled for constant dc. The dc from each phototube is measured with a digital voltmeter, and the fundamental and second harmonic of the phototube current are measured using individual lock-in amplifiers. All three of the associated ellipsometric parameters (N = cos2Ψ, S = sin2Ψ sinΔ, and C = sin2Ψ cosΔ) can be determined simultaneously in a single scan. The versatility of the instrument is demonstrated by the determination of the optical functions of Si from 238 to 652 nm (5.3-1.9 eV). © 1990 Optical Society of America.