Suppression Strategy of Snapback Effect for Multi-Cell RC-IGBT

The snapback effect of RC-IGBT occurs when the device transits from the unipolar mode to the bipolar mode during the turn-on process, which will increase the switching loss and affect the reliability of the device. In this paper, we analyze the turn-on process of RC-IGBT and build the mathematical physic model of the lateral-flowing electron current by using the infinitesimal method. We come up with a strategy of suppressing the snapback effect by optimizing the backside layout of devices and point out that increasing the equivalent resistance of collector is the critical solution. There are several specific methods of operation, such as increasing the number of MOS cells in parallel, decreasing the length of N+ short properly or optimizing the relative position of N+ short. By using Silvaco TCAD simulation software and combining the semiconductor fabrication process, we achieve the snapback-free I-V characteristic of RC-IGBT devices, which verifies the availability of our proposed suppression strategy. This research provides a significant reference for the design of RC-IGBT.