Determination of thicknesses and spectral dependences of refractive indices of non-absorbing and weakly absorbing thin films using the wavelengths related to extrema in spectral reflectances

Abstract

In this contribution a new efficient modification of the method enabling us to perform the optical characterization of non-absorbing and weakly absorbing thin films without using the absolute values of the reflectances measured will be presented. Namely, this modification is based on determining the values of the wavelengths corresponding to the points where the spectral dependences of the reflectances of the studied films measured for several angles of incidence touch the envelopes of maxima and minima of these spectral dependences. Using a simple formula containing the wavelengths mentioned one can evaluate the values of the thicknesses and spectral dependences of the refractive indices of the films analyzed. This fact will be demonstrated through optical characterization of a non-absorbing film of silicon dioxide and weakly absorbing film of photoresist placed on silicon single-crystal substrates. The results of this characterization will be compared with those achieved using a combined method of variable angle of incidence spectroscopic ellipsometry and near normal incidence spectroscopic reflectometry.