Analysis of the RC-IGBT snap-back phenomenon on the switching performance of parallel devices

In this paper, a simulation-based study is carried out with respect to the snap-back behavior in the output IV characteristics of reverse conducting RC-IGBTs. Half-cell TCAD models of 1200V RC-IGBT structures with different snap-back voltage levels were generated by varying the peak doping concentration of the punch-through N-buffer region. The effect of the snap-back characteristics on the switching behavior when devices are operating in parallel were studied under varying device and circuit conditions. Current mis-sharing between parallel RC-IGBTs was instigated and analyzed in order to identify the root cause of such behavior during the switching transients. Results show that the RC-IGBT snap-back voltage magnitude and variations along with the circuit and operating conditions play a critical role for determining if the device operates in a stable or un-stable mode.