EFFECTS OF GAMMA-IRRADIATION ON THE INSULATED-GATE BIPOLAR-TRANSISTOR

The effects of gamma irradiation on the International Rectifier IRGBC2 0 insulated-gate bipolar transistor (IGBT) was investigated. These dev ices were found to be sensitive to gamma irradiation due to their meta l-oxide-semiconductor field-effect-transistor (MOSFET) input drive. To tal doses as small as 50 Krads(Si) increased the saturated collector c urrent (I-c) by an order of magnitude when the irradiation was perform ed with zero gate bias. For a constant (V-g - V-th) of 0.5 V, I-c decr eased to about half its pre-irradiation value after irradiation to 40 Krads(Si). The threshold voltage of the MOSFET shifted in the negative direction with the largest and smallest shifts occurring for a positi ve and negative gate bias applied during the irradiation, respectively . The shift in threshold voltage saturated at the cut-in voltage of th e P-i-N diode portion of the device, indicating that gamma irradiation does not affect the P-i-N diode. The reverse blocking leakage current of the device is not very sensitive to radiation below a total dose o f 400 Krads(Si), but increases sharply for larger doses. All of these radiation-degraded characteristics of the IGBT are primarily the resul t of increasing interface-state and oxide-trapped charge densities wit h total radiation dose, which decreases the carrier channel mobility b y increased carrier scattering. Both room temperature and 150 degrees C annealing were observed to partially recover all of the device chara cteristics by reducing the radiation-induced oxide-trapped charges. Co pyright (C) 1996 Elsevier Science Ltd