Fast, self-nulling spectroscopic ellipsometer: Instrumentation and application

The advantages of rapid spectral scanning were combined with the inherent accuracy of a compensating ellipsometer operated in the polarizer compensator sample analyzer configuration. Wavelength is varied over the visible-UV at a maximum rate of 114 nm/s by rotating a continuously variable interference filter. A three reflection Fresnel rhomb serves as the achromatic quarter wave compensator. A microcomputer is used to collect spectroscopic measurements, perform instrument calibrations, digital filtering and interpret data. Wavelength independent parameters of multiple film optical models were determined by treating measurements of delta and psi at different wavelengths as independent measurements. Experimental and predicted ellipsometer measurements are compared by use of statistical techniques for the determination of optimum values and confidence limits of model parameters.