KINETIC MODELING OF THE CHEMICAL VAPOR-DEPOSITION OF SILICON DIOXIDE FROM SILANE OR DISILANE AND NITROUS-OXIDE

Gas-phase reaction mechanisms are proposed for the chemical vapor deposition (CVD) of silicon dioxide (SiO2) from silane or disilane with nitrous oxide at atmospheric pressure. Observed SiO2 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 N2O. SiH3 attack on N2O, and SiH3O attack on SiH4, are the propagating reactions. SiH3OH is posited to be the film precursor, which is rapidly oxidized and dehydrogenated on the growth surface. SiH3OH 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 Si2H6 is proposed to initiate the deposition of silicon dioxide from disilane in a large excess of nitrous oxide. Rapid reaction of the decomposition product, SiH2, with N2O suppresses the formation of larger silicon hydrides, generating the oxide film precursor, silanone (SiH2O). Besides the film, oxidized by-products are also formed from SiH2O. 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 N2O concentrations, both of the above mechanisms, as well as silicon hydride reactions, participate to a significant extent, resulting in silicon-rich oxide films, SiOx. Under these conditions, oxidized species containing more than one silicon atom are also suspected of participating in the deposition. © 1990, The Electrochemical Society, Inc. All rights reserved.