Electron irradiation effects and room-temperature annealing mechanisms for SiC MOSFETs

Abstract

In this work, the electron irradiation effects and post-irradiation annealing (PIA) response on SiC MOSFETs were investigated and analyzed in terms of the evolution of oxide- and interface-trap charges after irradiation and PIA. It is found that the electron irradiation leads to the significant decrease of Ron, degraded blocking characteristics, and negative shift of capacitance characteristics, which can be ascribed to the promoted generation of positively charged oxide and interface traps by irradiation. Interestingly, these degraded electrical properties can be partly or completely recovered by room-temperature (RT) anneal, which is associated with the difference in the sensitivity to the oxide/interface charge variations in the channel, JFET, and termination region. Surprisingly, the positive charge in the oxide presents an incomplete recovery, which is suggested to result from the tunneling electrons from SiC and thus the subsequent electron capture by positively charged oxygen vacancy in the oxide. Whereas, the irradiation-induced interface-trap charges are fully eliminated even after RT anneal for 15 days. Deep-Level Transient Spectroscopy (DLTS) characterizations shows that the interface defects with the energy band from EC − 0.14 eV to EC − 0.7 eV are enhanced by irradiation and exhibits similar dependence on the filling pulse as the near-interface traps. However, the irradiation-induced interface state density (Dit) distributions show a recovery behavior after RT storage, which is suggested to be resulted from the change in the charge states of interface defects from the electron trapping.

Keywords

• SiC MOSFET
• Electron irradiation
• Room-temperature anneal
• Oxide trap
• Interface trap