Effects of Moisture Absorption on the Electrical Behaviors of InGaZnO Thin Film Transistors

InGaZnO is easy to absorb moisture, thus leading to the formation of metal-hydroxyl (M-OH) defects. The effects of M-OH on the performance of InGaZnO thin-film transistor (TFT) as well as the methods to improve the performance are investigated by characterizing TFTs with various post-metallization-annealing (PMA) treatments. The formation of M-OH has an adverse influence on the TFT electrical parameters including threshold voltage (V-th), mobility, off-current and sub-threshold swing. M-OH also leads to an abnormal Vth shift under a positive-gate bias stress. Forming-gas annealing (N-2/H-2 = 95%/5%) is effective to reduce the formation of M-OH due to the passivation effect of H-2 and thus can effectively suppress the adverse influence caused by the M-OH. Moreover, due to its extremely strong passivation ability, the formation of M-OH as well as the effects on the TFT performance can be significantly suppressed by fluorine treatment.