Error correction for calibration and data reduction in rotating-polarizer ellipsometry: applications to a novel multichannel ellipsometer

Abstract

Calibration and data-reduction procedures have been developed for use in rotating-polarizer ellipsometry. The procedures are demonstrated with a novel rotating-polarizer multichannel ellipsometer designed for real-time spectroscopic investigations of film growth, etching, and surface phenomena. This instrument employs a photodiode array detection system, permitting the collection of spectra from 1.5 to 4.5 eV with a maximum time resolution of 40 ms. Analyses of errors specific to the detection system, including nonlinearity and stray light, are outlined, and simple correction procedures are applied to calibrations and measurements. Source and polarization system imperfections are determined in expanded calibration procedures that are designed to provide polarizer phase and analyzer azimuth versus photon energy, corrected to first order in the imperfections. Two alternative approaches to calibration are demonstrated, depending on the value of the ellipsometric parameter Δ. Exact data-reduction equations are also derived to include source and polarization system imperfections in the calculation of (Ψ, Δ). Although the overall procedures can also be applied to ellipsometers with single-channel detection, the advantages of the multichannel ellipsometer for characterization and correction of systematic errors are apparent.