IMPROVED ROTATING ANALYZER-POLARIZER TYPE OF SCANNING ELLIPSOMETER

A new type of spectroscopic ellipsometer in which the analyser and pol arizer rotate synchronously has been designed and constructed. For the system, the analyser and polarizer were driven 10(4) steps per revolu tion by two stepping motors with a speed ratio of 2:1. A second polari zer was placed in the optical path to eliminate the source polarizatio n effect. The light intensity thus contains four a.c. components, havi ng frequencies of omega0, 2omega0, 3omega0 and 4omega0. The ellipsomet ric 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 automatica lly controlled by a 386-based microcomputer. The results of measured s pectra of the complex refractive index for a 3000 angstrom thick Au fi lm sample are given. An equation for calculating directly the principa l angle to obtain the highest precision of the optical constants is pr esented.