Regensburg 2016 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 35: Thin Film Characterisation: Structure Analysis and Composition II

DS 35.3: Vortrag

Mittwoch, 9. März 2016, 15:30–15:45, H8

Determination of thickness and refractive index of ulta-thin films via ellipsometry — Peter Nestler and •Christiane A. Helm — Institut für Physik, Greifswald University, D-17487 Greifswald, Germany

Ellipsometric measurements of layered media deliver information on film parameters like layer thickness and refractive indices with high precision. In the simplest case the substrate is covered with a single homogenous, transparent layer only. Yet, the simultaneous determination of both parameters, thickness and refractive index of the layer, via ellipsometry is immediately possible only if the layer thickness exceeds 15 nm.

Here we present a technique to cross this limitation: A series expansion of the ellipsometric ratio ρ to the second order of the layer thickness relative to the wavelength reveals the first and second ellipsometric moment. These moments are properties of the layered surface and independent of incident angle. Using both moments and one additional reference measurement of the bare substrate enables to simultaneously determine both thickness and refractive index of ultra-thin layers down to 5 nm thickness.