Effects of junction profiles in bottom protection p-well on electrical characteristics of 1.2 kV SiC trench-gate MOSFETs

Effects of junction profiles in bottom protection p-well (BPW) on electrical characteristics of 1.2 kV SiC trench-gate MOSFETs were investigated using simulation methods. Breakdown mechanisms of BPW in the device were also elucidated by energy-band diagram and electric-field distribution across trench-gate. Monte Carlo Al-implantation simulation on the trench structure for BPW formation was carried out with variations in peak depth (D-BPW), concentration (N-BPW), and thickness of SiO2 spacer (T-spacer) on trench sidewall. The SiC trench-gate MOSFETs with deep D-BPW, high N-BPW, and thin T-spacer are suitable for high drain voltage due to a shielded trench gate by BPW. However, specific on-resistance (R-on,R-sp) increased because of laterally penetrated Al into p-base and accumulation regions during ion implantation for BPW formation. In case of shallow D-BPW, low N-BPW, and thick T-spacer, however, the gate oxide at trench bottom corner is considerably vulnerable to the dielectric breakdown due to fully depleted BPW near trench bottom corner and electric-field crowding at gate oxide.