Application of spectral and temporal weighted error functions for data analysis in real-time spectroscopic ellipsometry

In the analysis of spectroscopic ellipsometry (SE) data acquired on thin film structures, the weighted error function χ² plays a central role, allowing one to assess the validity of the optical model used to generate the best-fit simulation. The most difficult steps in implementing χ², however, involve the required quantification of the precision, accuracy and reproducibility of the SE measurement. In real-time SE, spectra are acquired continuously vs. time during the fabrication of thin film structures, and one has the advantage of extracting the conventional spectral averages of χ² vs. time or the temporal averages vs. photon energy. These two measures of the validity of the optical model, not only provide insights into the fitting procedure, but also allow one to identify otherwise unrecognized errors that can account for unexplained variations in χ². © 2003 Elsevier B.V. All rights reserved.