Pseudo-Mosfet Analysis of Proton Irradiated and Annealed SOI Wafer

The total dose irradiation effect on the SOI wafer is analyzed at the material level by pseudo-MOSFET technique. The proton irradiation induces positively charged traps in the buried oxide (BOX) and amphoterically charged traps at the film-BOX interface. The amphoteric interface trap charges contribute to the shift in threshold and flatband voltages by accentuating or attenuating the effect of the positive fixed charge in the BOX. The inherent ambipolar pseudo-MOSFET characteristics reveal both NMOS and PMOS properties, making it possible to identify and separate the charges that contribute to the shift of the turn-on voltage. The negatively charged acceptor-like states are located in the upper part of bandgap whereas the positively charged donor-like states are situated in the lower part of bandgap. These interface trap states can be removed by low-temperature annealing, so that only the oxide trapped charges continue to govern the turn-on voltage shift.