H2 dilution effect in the Cat-CVD processes of the SiH4/NH3 system

Gas-phase diagnostics in the catalytic chemical vapor deposition processes of the SiH4/NH3/H2 system were carried out to examine the effect of H2 dilution. The decomposition efficiency of NH3 showed a sharp decrease with the introduction of a small amount of SiH4, but this decrease was recovered by the addition of H2 when the NH3 pressure was low. On the other hand, at higher NH3 pressures, the decomposition efficiency showed a minor dependence on the H2 partial pressure. The addition of SiH4 to the NH3 system decreases the H-atom density by one order of magnitude, but this decrease is also recovered by H2 addition. H atoms produced from H2 must re-activate the catalyzer surfaces poisoned by SiH4 when the NH3 pressure is low.