Oxidation Studies of Crystalline CVD Silicon Nitride

Oxidation studies of CVD were performed in dry oxygen, oxygen‐argon, and oxygen‐nitrogen‐argon gas mixtures of various oxygen and nitrogen partial pressures at a total pressure of 1 atm at 1100°–1400°C. Parallel oxidation studies of single‐crystal silicon were also conducted for direct comparison. It was observed that the oxidation of both and Si followed parabolic growth kinetics with activation energies of about 115 kcal/mol and about 30 kcal/mol, respectively. The formation of a single layer of and evolution of could not account for the much lower parabolic rate constants and much higher activation energy for than for Si during the oxidation. Detailed characterization of the oxidation scales using ellipsometry, step‐by‐step etching, SIMS, and XPS techniques indicated that a duplex oxidation scale consisting of and was formed when was oxidized. The intermediate scale was identified as a single‐phase material, not a physical mixture of and . The low oxidation rate and high activation energy for during the oxidation were attributed to the formation of and low oxygen diffusivity in this structurally dense phase.