Thermal instability failure analysis of Shielded-gate Trench MOSFET in linear mode

Shielded-gate Trench (SGT) MOSFET is widely used in the low-voltage field because of its low specific on resistance and gate-to-drain charge. Like most power MOSFETs, thermal instability reduces the safety operation area (SOA) of the SGT MOSFET. Failure of SGT MOSFET due to thermal instability is observed and the mechanism is studied in this paper. According to simulation, increasing the channel length is an effective means to improve thermal stability of SGT MOSFET. Therefore, the improved SGT MOSFETs, T-shaped gate SGT and L-shaped gate SGT, are proposed. The simulation results show that the improved structures can reduce the current corresponding to zero temperature coefficient by 50%.