COLD REMOTE NITROGEN PLASMA POLYMERIZATION FROM 1.1.3.3-TETRAMETHYLDISILOXANE OXYGEN MIXTURE

Cold remote nitrogen plasma (CRNP) selectively reacts with silane-term inated organosiloxane compounds such as 1.1.3.3-tetramethyldisiloxane to give polymeric layers. Deposition rate measurements, FT-IR and Rama n spectroscopy were performed. The chemical composition of the deposit ed film is closely dependent on the reactive gas composition and its f lowing conditions. An original effect of dioxygen addition in the noni onic reactive media is pointed out: dioxygen addition leads to a fast and highly hydrocarbonated polymer formation with a nitrogen fixation in a silazane structure. Polymerization is described by a model where =Si - O. type of radicals are the critical reactant. A global mechanis m is proposed involving active species of the CRNP in initiation step of hydrogen abstraction and the nitrogen triplet state molecule N2 (A 3SIGMA) in methyl abstraction on =Si. type of free radical. Dioxygen a djunction appears to limit the methyl abstraction steps. The efficient direct oxygen reaction on free radicals leads to an increase of the = Si - O. radical density and, consequently of the average length of the growing polymeric fragments. Nitrogen fixation, involving oxygenated species, is discussed. Under defined conditions, a highly hydrophobic polymeric film is obtained with a volumic mass of 1.34 g/cm3 and a dep osition rate of about 12 mg/cm2 h corresponding to a growth rate of 20 0 angstrom/s. (C) 1994 John Wiley & Sons, Inc.