P-buried region effects on breakdown voltage of NPT-TIGBT structure

In this paper, we introduced a P-buried (P
_b
) layer under trench gate which relieved the electric field crowding in the Non Punch Through Trench gate Insulated Gate Bipolar Transistor (NPT-TIGBT) structure. The P
_b
layer, with carrier concentration of 5×10
¹⁶
cm
^-3
, was created underneath the trench gate within the n-drift layer. In this way, the concentration of electric field at the trench bottom corner decreased. As a result, the forward breakdown voltage characteristics of NPT-TIGBT improved. The structures were proposed and verified by T-CAD Sentuarus simulation. From the simulation results, the forward breakdown voltage increased by approximately 25% compared with conventional NPT-TIGBT. Furthermore, the forward current did not degrade the on-state voltage drop. In the experiments, the P
_b
layer was formed by boron implantation energies above 1 MeV with the Varian Genus 1520 High Energy Ion Implanter. The doping profiles were measured and analysed by SIMS.