Comparative Analysis of SGTMOS Degradation Under Repeated Off-State Avalanche and Short Circuit Current Pulses

Abstract

In this article, a 60-V split-gate trench vertical double diffused metal-oxide-semiconductor field-effect transistor (SGTVDMOS, SGTMOS) with low on-resistance is designed and manufactured. The device adopts an ultra-deep split gate trench with a grounded bottom shield gate. The electrical parameters degradations subsequent to repeated off-state avalanche and short circuit current pulses are investigated and compared for the first time. After avalanche voltage stress, crucial parameters such as threshold voltage (Vt), Miller capacitance (CGD) remain unaffected. However, a noteworthy change is observed in blocking characteristics, manifested as an increase in breakdown voltage. Conversely, after subjecting the device to short-circuit pulse current stress, a minor reduction in $\rm V_{t}$ is noted, while the breakdown characteristics remain constant. Technology computer-aided design (TCAD) simulation and actual test analysis are combined to reveal the degradation mechanism, it has been determined that electron injection degradation occurs under both stresses. However, distinct degradation phenomena occur due to the disparate positions of electron injection. During avalanche stress, electrons within the polysilicon (shield gate) tunnel into the oxide layer of the bottom shielding gate, while hot electron injection occurs near the active trench gate during a continuous short-circuit pulses.