Monolayer nitridation of silicon surfaces by a dry chemical process using dimethylhydrazine or ammonia

A hydrogen-terminated silicon surface was successfully converted to a surface covered with a monolayer of nitrogen. Nitridation was carried out in a vacuum chamber using either dimethylhydrazine [H₂N-N(CH₃)₂] or ammonia at a pressure of 1 mTorr and at temperatures ranging from 400 to 600°C. In situ x-ray photoelectron spectroscopy measurements revealed that the binding energy and the full width at half-maximum in the nitrogen spectra are the same as those in bulk Si₃N₄. Nitrogen content at the surface increased as the nitridation time increased and, below 500°C, saturated at a value that approximately corresponds to a monolayer thickness. These results show the effectiveness of dry chemical processes for preparing uniform Si surfaces terminated with specific atoms or molecules other than hydrogen.