The early oxynitridation stages of hydrogen-terminated (100) silicon after exposure to N-2 : N2O. III. Initial conditions

The structure and thermal stability in N-2 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 H-2 at high temperature (850 degreesC or 1100 degreesC) for durations on the order of 10(2) s. The observed stability with respect to N-2 at 850 degreesC 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 H-2 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 N-2 of hydrogen-terminated silicon is less efficient (per unit exposure) than that by N2O by 4 orders of magnitude.