Characterization of SiO2 thin films prepared by plasma-activated chemical vapour deposition

In this paper, we report on the preparation of SiO2 thin films onto different substrates using a direct plasma deposition process. The aim of this work was to investigate a variety of film properties depending on the deposition parameters, and to evaluate possible applications. The deposition process was based on a capacitively coupled r.f. low pressure plasma. The carrier and the monomer gases used for the silica deposition were air and hexamethyldisiloxane (HMDSO), respectively. The films deposited onto different substrates like silicon, brass and polyethylene terephthalate (PET) foils were characterized by FT-IR spectroscopy, ellipsometry, AFM, gas permeability measurements and corrosion test measurements. From ellipsometric and FT-IR measurements, it could be concluded that the films deposited at low r.f. input power and relatively high pressure contained carbohydroxyl groups indicating an incomplete reaction of the precursor material. It was found that the SiO2 film properties like refractive index, deposition rate, surface roughness and oxygen permeability were dependant on the deposition parameters. Otherwise, concerning the insulating properties and the corrosion tests strong dependencies were not found.