Effects of back-side He irradiation on MOS-GTO performances

A new version of a 1200V-20A MOS-GTO with 0.4 cm² die area is presented. The improvements of the switching performances have been achieved thanks to a new He irradiation technique performed from the back side of the device in order to avoid the degradation of the surface gate oxide. The high energy He irradiation allowed us to kill the lifetime in proximity of the N^-/N⁺ interface in such a way to significantly improve the device switching performances as suggested by the simulations. The irradiation did not affect the on-state characteristics. Instead, a reduction by a factor ~4 in the storage time and more than 30% decrease in the turn-off energy losses have been measured on irradiated samples with respect to not irradiated ones.