XPS and AES characterization of SiNx:H layers deposited by PECVD on Parylene C. Effects of thermal treatments on Parylene C surfaces and Parylene C/SiNx:H interlayers

Comparison of the X-ray photoelectron spectroscopy (XPS) spectra for surfaces of Parylene C thin layers deposited on alumina substrates without heating or after various heating times at 150 °C revealed an increase in chlorine concentration near the surface with increasing heating time. After 200 h heating at 150 °C, the Parylene C layer flaked off of the alumina substrate. The deterioration of the Parylene C seemed to be related to a chlorine transfer from the bulk of the layer to the free surface. A SiN x :H thin film was deposited on the Parylene C layer and characterized by XPS measurements. An Auger study of the SiN x :H film/Parylene C interface also revealed a chlorine excess in the interfacial region induced by heating the SiN x :H-Parylene C multilayer. However, after 200 h heating of the SiN x :H-coated Parylene C, the polymer appeared to be much less deteriorated than the uncoated film. This better stability of the coated Parylene C polymer seems to be the result of a decrease of the chlorine loss caused by the presence of the SiN x :H barrier.