Properties of thin films deposited from HMDSO/O₂ induced remote plasma: Effect of oxygen fraction
By Saloum, S.; Naddaf, M. & Alkhaled, B.
Published in Vacuum
2008
Abstract
Thin films deposited from Hexamethyledisiloxane (HMDSO)/O₂ mixture excited in a radio-frequency hollow cathode discharge system have been investigated for their structural, optical and corrosive properties as a function of oxygen fraction O₂ ( χO₂ = 0, 0.38, 0.61, 0.76 and 0.90 ). It is found that the effect of oxygen fraction on films properties is related to O₂ dissociation degree (αd) behavior in pure oxygen plasma. αd has been investigated by actinometry optical emission spectroscopy (AOES) combined with double Langmuir probe measurements, a maximum of O₂ dissociation degree of 15% has been obtained for 50 sccm flow rate of O₂ ( χO₂ = 0.61 in HMDSO/O₂ plasma). Fourier transform infrared spectroscopy (FTIR) and optical measurements showed that the behavior of both identified IR group densities and deposition rate as a function of oxygen fraction is similar to that of O₂ dissociation degree. The inorganic nature of the films depends significantly on oxygen fraction, the best inorganic structure of deposited films has been obtained for 62% HMDSO content in the mixture HMDSO/O₂ ( χO₂ = 0.38 ). The refractive index for deposited films from pure HMDSO ( χO₂ = 0 ) has been found to be higher than that of films deposited from HMDSO/O₂mixture. In HMDSO/O₂ plasma, it has a behavior similar to that of deposition rate, and it is comparable to that of quartz. The effect of oxygen fraction on the corrosive properties of thin films deposited on steel has been investigated. It is found that the measured corrosion current density in 0.1 M KCl solution decreases with the addition of O₂ to HMDSO plasma, and it is minimum for χO₂ = 0.38 .