THE CALCULATION OF THIN-FILM PARAMETERS FROM SPECTROSCOPIC ELLIPSOMETRY DATA

Spectroscopic ellipsometry (SE) has proven to be a very powerful diagn ostic for thin film characterization, but the results of SE experiment s must first be compared with calculations to determine thin film para meters such as film thickness and optical functions. This process requ ires four steps. (1) The quantities measured must be specified and the equivalent calculated parameters identified. (2) The film structure m ust be modeled, where the number of films is specified and certain cha racteristics of each layer specified, such as whether or not the film is isotropic or anisotropic, homogeneous or graded. (3) The optical fu nctions of each layer must be specified or parameterized. (4) The data must be compared with the calculated spectra, where a quantifiable fi gure of merit is used for the comparison. The last step is particularl y important because without it, no ''goodness of fit'' parameter is ca lculated and one does not know whether or not the calculated spectrum fits the data.