Reoxidation effects on the chemical bonding states of nitrogen accumulated at the oxynitride/silicon interface

Nitrogen bonding states near oxynitride/Si interfaces in NO-nitrided oxide films were investigated by x-ray photoelectron spectroscopy (XPS). A reoxidation process was used to change the nitrogen location in the depth profile. Charge-up effects on the XPS spectra were removed by considering a highly nonuniform nitrogen distribution. We found that the N 1s core-level shifts to a higher energy by 0.4 eV as the interfacial nitrogen is incorporated into the oxide during the reoxidation. It was also shown that the chemical environment of the interfacial nitrogen differs from that in Si3N4. We attribute this gradual chemical shift to the difference in the second nearest neighbor atoms surrounding the nitrogen.