Elucidation of New Turn-on Voltage Tail Phenomenon of IGBT and Improvement by Dynamic-CSL Structure

The voltage tail phenomenon during IGBTs turn-on is one of the causes of the increase in turn-on loss (Eon). It has been reported that the voltage tail during turn-on can be suppressed by reducing C
gc
, however, we have confirmed that there is a voltage tail phenomenon that cannot be explained by the effect of Cgc alone. To figure out the voltage tail phenomenon during turn-on, it is necessary to understand the 3D carrier behavior and experimentally demonstrate. In this study, we elucidate that this phenomenon is caused by the strong 3D carrier behavior using 3D-TCAD and propose a structure to solve this problem. In the proposed structure, the channel P layer directly below the source has the same accepter concentration as conventional structure, but the dynamic current spreading layer (Dynamic-CSL) where there is no source has a lower acceptor concentration layer. This Dynamic-CSL improves the 3D carrier transport. The voltage tail and Eon were significantly reduced in the proposed structure. We elucidated the voltage tail phenomenon during turn-on, which could not be fully explained by 2D-TCAD analysis, and we could experimentally demonstrate the reduction of voltage tail.