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 (mu(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 x 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 (Delta V-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 Delta V-th under positive bias.