SILICON-OXIDE PARTICLE FORMATION IN RF PLASMAS INVESTIGATED BY INFRARED-ABSORPTION SPECTROSCOPY AND MASS-SPECTROMETRY

In situ Fourier transform infrared absorption spectroscopy has been us ed to study the composition of particles formed and suspended in radio -frequency discharges of silane-oxygen-argon gas mixtures. The silane gas constumption was observed by infrared absorption. The stoichiometr y of the produced particles depends on the silane flow rate and was co mpared with commercial colloidal silica. A small proportion of silane gas produces nanometric stoichiometric particles whereas a large propo rtion produces larger under-stoichiometric particles. Absorption spect roscopy was sufficiently sensitive to reveal particles too small to be visually observed by laser light scattering. Post-oxidation oi hydrog enated silicon particles trapped in an argon plasma was obtained by ad ding oxygen. Mass spectrometry oi negative and positive ions showed an extensive range oi ionic clusters which may be at the origin of the o bserved particle formation. A model based on an iterative reaction seq uence gives a good agreement with the measured positive ion mass spect rum.