DATA-ANALYSIS FOR SPECTROSCOPIC ELLIPSOMETRY

The modeling of spectroscopic ellipsometry data is reviewed, and is di vided into three phases. The first phase involves the calculation of t he Fresnel reflection coefficients for a given layer structure; it is shown that the Abeles formalism provides the most flexibility, and can be readily related. to the Berreman formalism for calculations involv ing anisotropic layers. The second phase is to parameterize the optica l functions of each individual layer; several models are reviewed, inc luding effective media, the Lorentz oscillator and a recent parameteri zation of amorphous semiconductors. The final phase involves the fitti ng of the spectroscopic ellipsometry data to the model, where differen t figures of merit of the fitting function are discussed. A proper num erical analysis technique requires that the reduced chi2 be used as th e figure of merit, which will result in the proper weighting of data p oints, and in obtaining meaningful error limits and a measure of the g oodness of fit.