Optical and chemical characterization of expanding thermal plasma deposited silicon dioxide-like films

In this paper we report on the use of expanding thermal plasma technique for the deposition of carbon-free silicon dioxide films by means of argon/hexamethyldisiloxane/oxygen mixtures, at growth rates in the range of 6-12 nm/s, as a function of the substrate temperature. The variation of substrate temperature has been investigated as an alternative route to ion bombardment in promoting the densification of SiO2-like films. Information concerning film chemical composition was obtained by means of Fourier transform IR absorption and X-ray photoelectron spectroscopies. The films are stoichiometric and a residual hydrogen content of 3.5·1021 at/cm3 is detected in the film deposited at 300 °C (SiO2H0.17). The film optical characterization by means of UV-VIS and IR spectroscopic ellipsometry has highlighted the beneficial role of substrate temperature in the densification of the SiO2 film matrix and the decrease of film porosity.