Investigation of Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Grown by Triple-Targets Magnetron Co-Sputtering

The triple-targets magnetron co-sputtering system with three targets of In₂O₃, Ga₂O₃, and Zn was used to deposit amorphous indium gallium zinc oxide (a-IGZO) films. The deposited a-IGZO films were used as the channel layers of the transparent thin film transistors (TFTs). The In₂O₃ RF power of 50 W, Ga₂O₃ RF power of 25 W and Zn DC power of 10 W were independently tuned to obtain the optimal composition (In:Ga:Zn = 3.5:1:2.7) of the a-IGZO films. The effective field-effect mobility, on-to-off current ratio, and subthreshold swing of the optimal a-IGZO TFTs were 62.3 cm ²/V ·s, 6.5 × 10 ⁶, and 0.23 V/decade, respectively. Using the SiO x passivation and thermal-annealing treatment, the effective field-effect mobility, on-to-off current ratio, and subthreshold swing of the optimal a-IGZO TFTs were further improved to 68.5 cm ²/V ·s, 7.0 ×10 ⁶, and 0.22 V/decade, respectively. In addition, stable performances were also noted.