Effects of post-annealing treatments on the transfer characteristics of amorphous indium-gallium-zinc oxide thin film transistors

The transfer characteristics of amorphous indium-gallium-zinc oxide thin film transistors (a-IGZO TFTs) were investigated after the channel layers were annealed at 350 °C under air, oxygen (100% O₂), and hydrogen (5% H₂ +95% N₂) ambients. There was no obvious change in the threshold voltage (V_TH) and the drain current increased with post-annealing in the hydrogen ambient, whereas post-annealing in the oxygen ambient led to a decrease in the drain current and to a positive shift in the threshold voltage compared to that in the post-annealing in the air ambient. The fieldeffect mobilities of a-IGZO TFTs with post-annealing in air, oxygen, and hydrogen ambients were 14 cm²/V· s, 0.004 cm ²/V· s, and 60 cm²/V· s, respectively. Secondary post-annealing treatment of a-IGZO TFTs in air, oxygen, and hydrogen ambients hardly changed the field-effect mobility and subthreshold slope after they were annealed under an air ambient.