A snapback-free reverse conducting IGBT with recess and floating buffer at the backside

We propose two novel ways to alleviate the reverse conducting insulated gate bipolar transistor (RC-IGBT) snapback phenomenon by introducing the floating field stop layer with a lightly doped p-floating layer and recess structure at the backside. The floating field stop layer is submerged in the N-drift region and located several micrometers above the P+ anode region, which would not degrade the blocking capability but can suppress the snapback phenomenon effectively. When the collector length exceeds 100 μm, the snapback voltage ΔVSB of the floating field stop RCIGBTwith the p-floating layer can be less than 0.5V. Furthermore, the recess structure at the backside can separate the N+ short and P+ anode region, which will be beneficial to eliminate the snapback. Finally, an RC-IGBTwith a floating buffer layer and recess at the backside is proposed. Compared to the RC-IGBT featuring an oxide trench between the N+ short and P+ anode, the proposed one has utilized the simple recess structure to replace the costly oxide trench and achieved the identical characteristics simultaneously.