Improved Stability of $\alpha $ -InGaZnO Thin-Film Transistor under Positive Gate Bias Stress by Using Fluorine Plasma Treatment

The origin of positive-gate-bias-stress (PGBS)-induced instability and the effects of fluorine treatment on the instability of an InGaZnO thin-film transistor (TFT) are investigated. The fluorine treatments on the dielectric/InGaZnO interface and InGaZnO back channel of the device can effectively modulate their electrical properties. By characterizing the TFTs with various fluorine treatments, it is found that the back channel rather than the dielectric/InGaZnO interface dominates the PGBS instability. Electrons induced by moisture absorption near the back channel migrate from the back channel to the interface under PGBS at room temperature, thus resulting in a threshold-voltage decrease. Moreover, the fluorine treatment on the back channel effectively suppresses the PGBS instability due to reduced moisture absorption caused by the fluorine passivation.