Radiation and annealing related effects in NBT stressed P-channel power VDMOSFETs

Abstract

In this paper radiation and annealing effects in p-channel power VDMOSFETs previously subjected to the NBT stress during different periods are reported. The purpose of the investigation was to examine effects of a certain radiation stress in devices that had previously been exposed to another stress. It was observed that irradiation of previously NBT stressed devices led to additional increase of ΔVT and the increase is slightly more pronounced for devices previously NBT stressed for 168 h, which might be of interest in the case of a high total dose received. Also, it is observed that in devices subjected to the NBT stress for 1 h, and γ-irradiated up to 90 Gy with the gate voltage applied, thermally activated processes during annealing are not sufficient for reducing the threshold voltage shift to the value before the NBT stress, which can have implications on the device operation in multiple stresses harsh environment conditions.