A method and apparatus are disclosed for accurately and repeatably determining
the thickness of a thin film on a substrate. A rotating compensator ellipsometer
is used which generates both 2 and 4 output signals. The 4
omega signal is used to provide an indication of the temperature of the sample.
This information is used to correct the analysis of the thin film based on the
2 signal. These two different signals generated by a single device provide
independent measurements of temperature and thickness and can be used to accurately
analyze a sample whose temperature is unknown.
