Total-Ionizing-Dose Effects in IGZO Thin-Film Transistors

Total-ionizing-dose (TID) effects are evaluated in back-gated indium-gallium-zinc oxide (IGZO) thin-film transistors irradiated under different gate biases. Negative-bias irradiation leads to worst-case degradation of TID response in these devices, primarily as a result of enhanced charge trapping in the SiO2 overlayer. The relatively small peak transconductance decrease after irradiation illustrates that IGZO transistors are much less sensitive to interface-trap buildup and other instabilities due to hydrogen release and transport than amorphous Si thin film transistors examined previously. The TID response of devices with different gate sizes is also investigated. No significant geometry dependence is observed, which is promising for future scaling down of the technology.