Characterisation of complex multilayer structures using spectroscopic ellipsometry

We have developed a fit method that allows detailed analysis of complicated ellipsometric spectra, such as those of thick (similar to 10 mu m) multila yer structures found in modern integrated optics devices. Ellipsometry shou ld be the natural choice for thorough nondestructive characterisation of th ose heterostructures, but extraction of the required parameters is often im practicable by common approaches. Our fit procedure is based in spline para metrisations of the unknown optical functions and is applicable to material s either with a smooth optical response or displaying sharp electronic tran sitions in the analysed energy range. We have applied our method to charact erise PECVD-grown non-stoichiometric silicon oxides (SiOx) and thick wavegu ide structures based on these materials.