Spectroscopic ellipsometry of thin films on transparent substrates: A formalism for data interpretation

By reviewing the operational principles of modem rotating analyzer ellipsometry, we propose general analytical formalism which permits the analysis of spectroscopic ellipsometry data for thin films on transparent substrates. The inclusion of incoherent reflection from the backsurface of an optically thick substrate changes the usual definitions of Aand φ. Experimental data on both glass and ZnO-coated glass are modeled to confirm the validity of this new formalism. We also simulated the ellipsometry spectra of amorphous silicon on glass to show the potential for in situ studies. The results show that the accuracy of ellipsometry data can be improved by including this incoherent backsurface reflection in the measurement, as opposed to roughening the back of the substrate.