The effect of water desorption and organosilane coupling agents on the adhesion of poly(p-xylylene) films to a silicon wafer surface

The adhesion strength of a poly(p-xylylene) (PPX) film to a silicon wafer surface deposited from the vapor was studied using a peel test method. It was found that, within the time and the temperature range studied in this work, the adhesion strength increases with the time and the temperature of the vacuum desiccation of the surface prior to the deposition of the film. This shows that the presence of water adsorbed on the surface strongly decreases the adhesion strength of the film. The effect of organosilane coupling agents on the adhesion of the film to the silicon wafer surface was studied for organosilane derivatives of different chemical compositions. It was found that the adhesion strength can be significantly improved by the presence of 3-(trimethoxysilyl)propyl methacrylate vapor before or during the poly(p-xylylene) deposition. No significant effect on PPX film adhesion was observed for other organosilanes having the propylmethacrylate group replaced by phenyl or alkyl groups. It was found that, in contrast to the other organosilanes, the recrystallization of the PPX from solution did not remove the methacrylate organosilane which remained bonded to the PPX crystals. It is suggested that chemical bonding between the methacrylic group and the PPX chain end radicals is responsible for the improved adhesion of the PPX films.[PUBLICATION ABSTRACT]