Surface Silicon Crystallinity and Anomalous Composition Profiles of Buried SiO2 and Si3N4 Layers Fabricated by Oxygen and Nitrogen Implantation in Silicon

Abstract

Buried SiO₂ and Si₃N₄ with residual crystalline surface silicon were fabricated by implantation of O⁺, O₂ ⁺, N⁺ and N₂ ⁺ into single-crystal silicon with 0.6–3.0×10¹⁸ atom/cm² dose at an energy of 70–150 keV/atom. The implanted silicon wafers were annealed at 1150°C to recover the surface silicon crystallinity and to ensure good Si–O and Si–N bonds. After this, high-quality crystalline silicon layers were grown epitaxially on the implanted surface. The surface silicon damage and the buried layer composition profiles were measured reliably by the Rutherford backscattering method together with the channeling technique. In the buried layers, the O/Si ratio did not exceed the stoichiometric ratio of 2.0 for SiO₂ even before annealing. However, the N/Si ratio exceeded the stoichiometric ratio of 4/3 for Si₃N₄.