Atmospheric-pressure silica-like thin film deposition using 200 kHz/13.56 MHz dual frequency excitation

Atmospheric pressure plasma enhanced chemical vapour deposition was used to synthesize silica-like thin films on polyethylene 2, 6 naphthalate substrate with hexamethyldisiloxane as the precursor and Ar/O₂/N₂ mixture as the working gas. A dual frequency (DF) excitation consisting of 200 kHz and 13.56 MHz frequencies was employed as the plasma source. The results have shown that compared to the single low frequency discharges, the DF excitation helps to improve plasma uniformity with less filaments. This could help to reduce the macro-defects and therefore to improve the permeation performance of the barriers. Besides, due to the increased electron density and gas temperature, the DF excitation demonstrates a more efficient breaking of Si-CH₃ bonds and therefore more oxidized structures of the deposited silica-like thin films.