A mass spectrometric investigation of the plasma polymerization of methyltrimethoxysilane in an r.f. discharge

Quadrupole mass spectrometry was used to determine the chemical species present during r.f. discharges in methyltrimethoxysilane (MTMOS) and in MTMOS-Ar and MTMOS-O₂ mixtures. Hydrogen, low molecular weight (C₁-C₃) hydrocarbons, aldehydes and alcohols and silicon-containing fragments arising from MTMOS decomposition were observed in discharges in MTMOS and in MTMOS-Ar mixtures. The major components of discharges in MTMOS-O₂ mixtures were found to be H₂, OH, H₂O, CO, CO₂ and residual oxygen.Discharges in MTMOS or in MTMOS-Ar mixtures deposited polyalkoxysiloxane films. Similar discharges in MTMOS-O₂ mixtures deposited oxygen-deficient vitreous silica films. All of these films had large internal stresses resulting from the plasma polymerization process. The use of argon as a carrier gas for MTMOS in the production of polyalkoxysiloxane coatings reduced this stress significantly.