Kinetic Modeling of the Chemical Vapor Deposition of Silicon Dioxide from Silane or Disilane and Nitrous Oxide

Abstract

Gas‐phase reaction mechanisms are proposed for the chemical vapor deposition (CVD) of silicon dioxide from silane or disilane with nitrous oxide at atmospheric pressure. Observed 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 . attack on , and attack on , are the propagating reactions. is posited to be the film precursor, which is rapidly oxidized and dehydrogenated on the growth surface. 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 is proposed to initiate the deposition of silicon dioxide from disilane in a large excess of nitrous oxide. Rapid reaction of the decomposition product, , with suppresses the formation of larger silicon hydrides, generating the oxide film precursor, silanone . Besides the film, oxidized by‐products are also formed from . 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 concentrations, both of the above mechanisms, as well as silicon hydride reactions, participate to a significant extent, resulting in silicon‐rich oxide films, . Under these conditions, oxidized species containing more than one silicon atom are also suspected of participating in the deposition.