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 cm²/V·s, a steep subthreshold swing of 263 mV/decade, a high I_ON/I_OFF ratio of 7.56 × 10⁸ 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:O₂ = 3 : 3), 0.9V (vacuum), 1.0V (O₂). These results can be explained by the O_II/O_total of the AZO films. The AZO film annealed in mixed gas (Ar:O₂ = 3 : 3) has the least oxygen vacancy density that leads to the least ΔV_th under positive bias.