Gas‐phase reaction mechanisms are proposed for the chemical vapor deposition (CVD) of silicon dioxide ( SiO 2 ) from silane or disilane with nitrous oxide at atmospheric pressure. Observed SiO 2 growth profiles are presented, and computed profiles are compared to these observations. The deposition of silicon dioxide from silane and excess nitrous oxide is hypothesized to be a chain reaction initiated by the decomposition of N 2 O . SiH 3 attack on N 2 O , and SiH 3 O attack on SiH 4 , are the propagating reactions. SiH 3 OH is posited to be the film precursor, which is rapidly oxidized and dehydrogenated on the growth surface. SiH 3 OH is also posited as an intermediate in the formation of other (non‐depositing) oxidized by‐products. The proposed mechanism accounts for a weak dependence of the peak growth rate on initial silane concentration and a strong dependence on nitrous oxide. The decomposition of Si 2 H 6 is proposed to initiate the deposition of silicon dioxide from disilane in a large excess of nitrous oxide. Rapid reaction of the decomposition product, SiH 2 , with N 2 O suppresses the formation of larger silicon hydrides, generating the oxide film precursor, silanone ( SiH 2 O ) . Besides the film, oxidized by‐products are also formed from SiH 2 O . This second mechanism accounts for a strong dependence of the peak growth rate on initial disilane concentration and a weak dependence on nitrous oxide. At lower N 2 O concentrations, both of the above mechanisms, as well as silicon hydride reactions, participate to a significant extent, resulting in silicon‐rich oxide films, SiO x . Under these conditions, oxidized species containing more than one silicon atom are also suspected of participating in the deposition.
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Giunta et al. (1990) studied this question.