Ion contribution to the deposition of silicon dioxide in oxygen/silane helicon diffusion plasmas

A very high silane dissociation rate (greater than or equal to 95%) has been measured using mass spectrometric analysis of neutral species in a low pressure (a few mTorr) high density (greater than or equal to 10(11) cm(-3) for a radio frequency source power of 800 W) oxygen/silane (O-2/SiH4) helicon deposition reactor. Energy selective mass spectrometric measurements of positive ions have been performed for O-2/SiH4 flow rate ratios varying from 1 to 10 and for a constant power of 800 W. A simple model of the ion-induced deposition rate has been developed and the results have been compared to the measured deposition rate. It appears that 20%-50% of the silicon atoms in the near-stoichiometric deposited oxides could result from the flux of silicon-containing ions (essentially Si+ and SiOH+) to the substrate during deposition. An oxidation process via O-2(+) ions and an etching process via H-3(+) ions could possibly be involved in the ion-induced deposition mechanism. (C) 1997 American Institute of Physics.