Structural characterisation of SiO2 based multilayers using spectroscopic ellipsometry

We have characterised PECVD-grown non-stoichiometric silicon oxides (SiOx) and thick waveguide structures based on these materials with spectroscopic ellipsometry. We have developed a fit method that allows detailed analysis of complicated ellipsometric spectra, such as those of thick (similar to 10 mum) multilayer structures found in modern integrated optics devices. Elli psometry should be the natural choice for thorough nondestructive character isation of those heterostructures, but extraction of the required parameter s is often impracticable by common approaches. Our fit procedure is based i n spline parametrisations of the unknown optical functions and is applicabl e to materials either with a smooth optical response or displaying sharp el ectronic transitions in the analysed energy range.