TOTAL-DOSE EFFECTS IN CONVENTIONAL BIPOLAR-TRANSISTORS AND LINEAR INTEGRATED-CIRCUITS

Total dose damage is investigated for discrete bipolar transistors and linear integrated circuits that are fabricated with older processing technologies, but are frequently used in space applications. The Kirk effect limits the current density of discrete transistors with high collector breakdown voltage, increasing their sensitivity to ionizing radiation because they must operate low injection levels. Bias conditions during irradiation had different effects on discrete and integrated circuit transistors: discrete devices were strongly dependent on bias conditions, whereas damage in the linear ICs was nearly the same with or without bias. There were also large differences in the response of these devices at low dose rates. None of the discrete transistors exhibited enhanced damage at low dose rates, whereas substantially more damage occurred in the linear devices under low dose rate conditions, particularly for parameters that rely directly on pnp transistors. The threshold for dose rate effects in pnp transistors was about 0.01 rad(Si)/s, which is approximately two orders of magnitude lower than the corresponding threshold for npn transistors in integrated circuits.