Evaluation of Silicon Nitride Layers of Various Composition by Backscattering and Channeling-Effect Measurements

Composition and density of silicon nitride layers deposited on silicon by the NH3–SiH4 reaction at 850°C were measured as a function of the reaction components. Backscattering and channeling-effect measurements with MeV 4He ions were used to determine the depth dependence of the concentration ratio of nitrogen to silicon and density. The compositions of the silicon nitride layers were stoichiometric with densities approximately 3.0 g/cm3 for NH3/SiH4 deposition ratios greater than 10. For lower ratios, the concentration of nitrogen decreased and that of silicon increased. The variation of the concentration ratio of nitrogen to silicon follows the variation in the physical and electrical properties of the layers.