COMPARISON BETWEEN THE REACTION-MECHANISMS OF NITRIDATION OF SI(100) BY A NH3 MOLECULAR-BEAM AND BY A N-2(-BEAM() ION)

Nitridation of a Si(100) surface takes place with NH3 at temperatures higher than 600 degrees C and with a low energy N-2(+) ion beam at roo m temperature, forming a thin film of nitride. The nitridation process es have been studied in situ under ultrahigh vacuum by X-ray photoelec tron spectroscopy (XPS). The reaction with NH3 occurs on the surface w ith Si atoms supplied by out-diffusion from the substrate, producing a nitride film. On the other hand, the N atoms of the low energy N-2(+) ion beam (100-1000 eV) penetrate into the bulk by their kinetic energ y and form the nitride layer near the surface. The difference of these mechanisms is clearly observed in the evolution of the N1s and Si2p X PS spectra during the reaction.