IMPROVED ROTATING ANALYZER-POLARIZER TYPE OF SCANNING ELLIPSOMETER

A new type of spectroscopic ellipsometer in which the analyser and polarizer rotate synchronously has been designed and constructed. For the system, the analyser and polarizer were driven 10(4) steps per revolution by two stepping motors with a speed ratio of 2:1. A second polarizer was placed in the optical path to eliminate the source polarization effect. The light intensity thus contains four a.c. components, having frequencies of omega0, 2omega0, 3omega0 and 4omega0. The ellipsometric parameters psi and DELTA, as well as the optical constants, can be independently obtained by calculating any one of the two sets of a.c. signals. The system was self-calibrated, and was fully and automatically controlled by a 386-based microcomputer. The results of measured spectra of the complex refractive index for a 3000 angstrom thick Au film sample are given. An equation for calculating directly the principal angle to obtain the highest precision of the optical constants is presented.