Characterization of stoichiometric surface and buried SiN films fabricated by ion implantation using extended x-ray absorption fine structure

The microstructural properties of stoichiometric surface and buried Si3N4 films, fabricated with N-15 ion implantation into Si wafers, are studied using the extended x-ray absorption fine structure (EXAFS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopies. Complementary information about the film composition and structure is provided by nuclear reaction analysis (NRA) and cross-section transmission electron microscopy (XTEM). The films have been characterized in the as-implanted state and after annealing in the temperature range 1100-1200 degrees C. For all the examined films, the N/Si ratio at the peak of the nitrogen profile, as measured by NRA is 1.33, a value that corresponds to stoichiometric nitrides. However, small compositional deviations towards a N-rich composition are detected by EXAFS in the surface nitrides. The excess nitrogen is also detectable in the NEXAFS spectra, where it introduces a characteristic resonance Line superimposed to the absorption edge. Finally, XTEM observations confirm the formation of the nitride layers and reveal different degrees of damage at the Si3N4/Si interface for the low and high energy implantations, respectively. (C) 1996 American Institute of Physics.