Study on False Turn-On in IGBT With Floating p-Well and Comparing With Improved Structures

In a half bridge circuit, one OFF-state insulated gate bipolar transistor (IGBT) can be turned on falsely if its overshoot of gate voltage (${V}_{\text {GE}}$) exceeds the threshold voltage (${V}_{\text {th}}$) during the turn-on period of the another IGBT. In this article, the mechanism of false turn-on in the IGBT with floating p-well [i.e., injection-enhanced IGBT (IEGT)] is studied based on theoretical analysis, simulation, and experiment. Main factors determining the overshoot of${V}_{\text {GE}}$are Miller capacitance (${C}_{\text {GC}}$), collector voltage change rate ($\textit {dV}_{\text {CE}}/\textit {dt}$), gate-emitter capacitance (${C}_{\text {GE}}$), and gate resistance (${R}_{\text {G}}$). It is found that the peak overshoot of${V}_{\text {GE}}$[${V}_{\text {GE(max)}}$] occurs after the time with peak$\textit {dV}_{\text {CE}}/\textit {dt}$due to the${R}_{\text {G}}~{C}_{\text {GE}}$network, which is beneficial for reducing${V}_{\text {GE(max)}}$to some extent. Reducing${C}_{\text {GC}}$is the most effective way to suppress the false turn-on and improve the tradeoff between turn-on loss (${E}_{\text {on}}$) and${V}_{\text {GE(max)}}$, which is verified by comparing the IEGT with three improved structures, i.e., IGBT with floating p-well separated from the trench gate, micropattern trench (MPT) IGBT, and split gate (SG) IGBT. Experimental results show that${V}_{\text {GE}(\max)}$in MPT IGBT is reduced by 39% even under a higher peak$\textit {dV}_{\text {CE}}/\textit {dt}$.