A combined X-ray, ellipsometry and atomic force microscopy study on thin parylene-C films

Parylene-C thin films in a thickness range from 7 to 35 nm are deposited on silicon oxide and investigated for their structural and morphological properties by different methods. It is shown that spectroscopic ellipsometry (SE) is a powerful too] to obtain spatially resolved information on the homogeneity of thin films revealing relative changes in layer thickness and in the refractive index. However, the results can be considerably improved in combination with X-ray reflectivity (XRR) which provides highly accurate results on layer thickness. The layer thickness from XRR is used as a fixed input value for the evaluation of the ellipsometry data which reveals a layer thickness dependence of the refractive index in the thin film regime. The interface roughness is determined from XRR as well as the surface rms roughness which can be compared to the roughness found by atomic force microscopy (AFM) which varies between 0.5 and 2.0 nm. Both results for the roughness show excellent agreement. Additionally, a correlation of the roughness and the deposition rate is found. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim