The Effects of Post Annealing Process on the Electrical Performance and Stability of Al-Zn-O Thin-Film Transistors

In this work, we studied the effects of post annealing process on the electrical performance and positive bias stability (PBS) of aluminum-zinc-oxide (AZO) thin film transistors (TFTs). Among all the devices, the TFT annealed in vacuum atmosphere exhibits excellent I-V characteristics, such as a saturation mobility (μ _sat ) of 45.90 cm ² /V·s, a steep subthreshold swing of 263 mV/decade, a high I _ON /I _OFF ratio of 7.56 × 10 ⁸ because of its excellent film quality. In addition, the positive bias stability of TFTs annealed in different atmosphere under positive bias (+5V, 2000s) were also conveyed. The threshold voltage shift (ΔV _th ) was 0.3V (mixed gas, Ar:O ₂ = 3 : 3), 0.9V (vacuum), 1.0V (O ₂ ). These results can be explained by the O _II /O _total of the AZO films. The AZO film annealed in mixed gas (Ar:O ₂ = 3 : 3) has the least oxygen vacancy density that leads to the least ΔV _th under positive bias.