The early oxynitridation stages of hydrogen-terminated (100) silicon after exposure to N₂:N₂O. III. Initial conditions

Abstract

The structure and thermal stability in N₂ of hydrogen-terminated (100) silicon has been studied by X-ray photoemission spectroscopy, transmission electron microscopy, atomic force microscopy, thermal programmed desorption, and reflection high energy electron diffraction. Device-quality surfaces were prepared in an open-chamber reactor by exposing single crystalline, (100) oriented silicon to H₂ at high temperature (850 °C or 1100 °C) for durations on the order of 10² s. The observed stability with respect to N₂ at 850 °C is inconsistent with the reported desorption kinetics and may be accounted for in terms of either physico-chemical properties of the system (e.g., the presence of a buried layer of H₂ or of hydrogen-decorated vacancies whose out-diffusion restores the hydrogen terminations on the surface) or the reactor (persistence of hydrogen in the atmosphere even after switching it off). The nitridation by N₂ of hydrogen-terminated silicon is less efficient (per unit exposure) than that by N₂O by 4 orders of magnitude.