XPS analysis of carrier trapping phenomena in ultrathin SiO ₂ film formed on Si substrate

We have developed an XPS time-dependent measurement technique with which we can address serious reliability issues in metal-oxide-semiconductor field-effect transistors (MOSFETs). By using this technique, we determined the density of hole traps in ultrathin SiO ₂ films without making electrodes for electrical measurements. In this paper, we demonstrate a new application of this method to analysis of the electron trapping and interface states generation during electron-beam irradiation. We found that the Si 2p peak binding energy of a n-type Si substrate covered with a SiO ₂ film (0.8nm) decreases to a saturation value during electron-beam (0.5eV: only electron injection case) irradiation. From the shift of the Si 2p peak binding energy, we were able to obtain the electron trap density of the SiO ₂ film. On the other hand, the binding energy first increases, then decreases to a saturation energy, smaller than the initial value, during electron-beam (6eV: both electron and hole injection case) irradiation. The complex phenomena are discussed in connection with interface states generation at SiO ₂ /Si interfaces.