Radiation Effects on MOS Power Transistors

The use of power MOS transistors in spacecraft and military equipment is limited by their vulner-ability to ionizing radiation (total-dose and doserate). The total-dose hardness of four types of power MOS is examined in this paper. All devices experience comparable shifts of VGS(th) following total-dose exposure. Other functional parameters are not affected by dose up to half a megarad. Thus, an effective hardening technique consists of extending the range of gate bias and gate drive to allow operation at high dose levels. The results of dose-rate testing of three types of power MOS are presented and analyzed. Photocurrent burnouts are tentatively attributed to thermally induced second breakdown of the drain-source diode. Decreasing the carrier lifetime of the junction material is anticipated to decrease this vulnerability.