Regular Article

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

¹ Power Semiconductor Research Center, Korea Electrotechnology Research Institute, Changwon 51543, Republic of Korea
² Department of Electrical Engineering, Myoungji University, Yongin 17058, Republic of Korea

^* e-mail: ogseok@keri.re.kr

Received: 5 September 2019
Received in final form: 24 October 2019
Accepted: 23 January 2020
Published online: 19 February 2020

Abstract

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,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.