Characterization of Oxide Growth at High Temperatures and Low Pressures from Silane/Nitrous Oxide Reaction

Abstract

The reaction of silane and nitrous oxide at high temperatures and low pressures was investigated for a large range of mole ratio of the reactants. For a nitrous oxide/silane mole ratio of approximately 100, silicon dioxide having the stoichiometric refractive index of 1.45 is obtained for growth at 800°–850°C. For a mole ratio of 2.2 and growth at 700°–750°C, silicon‐rich oxide results with the refractive index increasing linearly from 1.75 to 1.94 with increasing temperature. The growth rate exhibits an Arrhenius‐type temperature dependency in the above ranges with activation energies of 1.43 and 0.89 eV for stoichiometric and silicon‐rich oxide, respectively. The increase in growth rate for both oxides with increased wafer spacing is quantitatively interpreted, for small wafer spacings, in terms of a modified model developed for semi‐insulating polysilicon growth from the same reactants. The refractive index of silicon‐rich oxide also increases with increased spacing, which correlates with greater silicon incorporation at higher growth rates. The functional form of the within‐wafer thickness profile for both oxides is also consistent with the model referred to, as is the linear dependence of stoichiometric‐oxide growth rate on silane partial pressure.