Effects of thermal annealing on the electrical characteristics of In-Ga-Zn-O thin-film transistors with Al₂O₃ gate dielectric

We studied how the performance of In–Ga–Zn–O (IGZO) thin film transistors (TFTs) with Al2O3 gate insulator was affected by post-fabrication annealing temperature and annealing time. At a fixed annealing time of 2 min, the IGZO TFT exhibited the best transfer and output characteristics in the case of 300 °C in N2 atmosphere, which is attributed to the achievement of appropriate carrier concentration and Hall mobility in the IGZO film. Further, it was found that both of the carrier concentration and Hall mobility in the IGZO film increased with the increment of annealing temperature. For the annealing temperature of 300 °C, the performance of the IGZO TFT was further improved by extending annealing time to 5 min, i.e., the field effect mobility, sub-threshold swing and on/off current ratio were 11.6 cm2/(V · s), 0.42 V dec−1 and 106, respectively. The underlying mechanism was discussed.