Ellipsometry of Al2O3 thin films deposited on Si and InP

Al2O3 thin films, possessing potential for MIS electronic applications, have been deposited on clean Si and InP surfaces by evaporating powder from a graphite cell heated by electron bombardment. The build up of the films was monitored by Auger electron spectroscopy (AES). Continuous, amorphous films were also prepared on microgrids, for TEM studies. The film thickness was measured using multiple angle of incidence (66-72 degrees) and 70 degrees angle ellipsometry using a 633 nm laser line. Calibration curves have been calculated for n = 1.61-1.77 limits for Al2O3 and various substrates. They were considerably affected by the substrate optical constants. Evaluation of ellipsometric data resulted in typical thickness values of 5-10 nm as confirmed with cross-sectional TEM.