Simulation study on the influence of metal contact and MOS interface trap states on the electrical characteristics of SiC IGBT

Abstract

A 13 kV class n-channel 4H–SiC trench gate insulated gate bipolar transistor (IGBT) structure is designed based on Silvaco TCAD device simulator tool. The influence of metal/SiC and SiC MOS interface trap states on the static and dynamic characteristics of SiC IGBT devices are systematically studied. It is found that the electrical properties of SiC IGBTs are insensitive to the donor or acceptor traps at the interface of metal/SiC and the donor traps at the SiC/SiO2 interface. However, the acceptor traps at the SiC/SiO2 interface affect the electrical properties of SiC IGBTs greatly. When the acceptor trap density at the SiC/SiO2 interface (Dita) is up to the level of 1012 cm−2·eV−1, the turn-on voltage drop (VCEON) is increased gradually with the augmentation of Dita. The breakdown voltage (VBR) of the device is increased slightly. Further study of the device’s turn-off characteristics shows that the turn-off loss (EOFF) is decreased with the increase in Dita but a large tail current is formed. The mechanism may be that when the electrons are injected from the N+ source region into the N− drift region, the SiC/SiO2 interfacial acceptor traps at the side wall of trench gate capture a large number of electrons. As a result, the minority carrier concentration is decreased, and the conductance modulation effect on the N− drift region is weakened.