Gas phase and surface kinetic processes in polycrystalline silicon hot-wire chemical vapor deposition

Experiments and numerical simulations have been conducted to determine crit ical parameters for growth of polycrystalline silicon via hot-wire chemical vapor deposition. Reactor-scale simulations performed using the Direct Sim ulation Monte Carlo (DSMC) method have revealed a number of important pheno mena such as a sharp drop of 1700 K in the gas temperature from the wire to substrate. The gas-phase reaction of silicon atoms produced on the wire wi th ambient silane molecules has been studied using ab initio quantum chemic al calculations. Results reveal that collisional stabilization of the adduc t (H3SiSiH) is unlikely under typical growth pressures, but an energeticall y favorable, low-pressure pathway has been found that leads to the formatio n of Si2H2 and H-2. Threshold ionization mass spectrometry measurements of radicals have revealed that at the pressure characteristic of growth (2-200 mTorr of 1% SiH4 in He), the radical SiH2 is predominant. Finally, film gr owth studies reveal that hot-wire-produced atomic hydrogen may preferential ly etch amorphous silicon and suppress the formation of small nuclei. (C) 2 001 Elsevier Science B.V. All rights reserved.