Effects of the substrate temperature on the deposition of thin SiOx films by atmospheric pressure microwave plasma torch (TIA)

The effect of surface temperature on the deposition of silicon oxide (SiOx) films with a non-thermal microwave axial injection torch (TIA) was investigated in an open air reactor. Argon was used as plasma gas and hexamethyldisiloxane (Si2O2C6H18) as silicon precursor. The parametric study reported here focuses on the influence of the substrate temperature on the morphological and chemical properties of the films deposited in the interval [0 °C-130 °C]. A similar effect of low and high surface temperature on the deposition process and on the microstructure of the deposited films was highlighted. Macroscopically, particles were promptly produced in the gas phase and incorporated to the film, which generates high surface roughness. Microscopically, FTIR results have shown a high carbon contamination of the deposited films at low and high temperatures, resulting in understoichiometric SiOx films. They have also demonstrated that an optimum growth window for smooth and particle free SiOx was to keep the surface temperature between 30 and 60 °C. Simple reaction mechanisms for powder formation and continuous silicon oxide thin films growth are suggested for each temperature ranges.