Analysis on Turn-on Voltage Tail

Abstract

In this work, we report a newly developed analysis method to investigate the mechanism of turn-on voltage tail of IGBT, aiming at the reduction of turn-on loss (E_on). This analysis method visualizes how gate-collector capacitance (C_GC) increases by monitoring the potential change at the interface of the gate oxide and silicon around the gate trench during the turn-on process. It was found that, in the turn-on transient, initially, the collector-emitter voltage (V_CE) decrease, and C_GC increase drastically when the potential around the gate trench falls below the gate-emitter voltage (V_GE) and that the sudden increase of C_GC causes the turn-on voltage tail. Detailed TCAD analysis reveals that the electric potential around the gate trench is lowered by the dummy trench and causes the sudden increase of C_GC. To verify that the dummy trench is origin of the turn-on voltage tail, full gate trench IGBT with no dummy trench is studied. In the full gate trench IGBT, neither sudden increase of C_GC nor turn-on voltage tail are observed.