The influence of annealing atmosphere on sputtered indium oxide thin-film transistors

Abstract

Abstract Indium oxide (In 2 O 3 ) thin films sputtered at room temperature were annealed under different atmospheres and examined for thin-film transistor (TFT) active channel applications. The annealing process was performed in a rapid thermal annealing system at 350 °C under O 2 , Ar, forming gas (FG, 96% N 2 /4% H 2 ), and N 2 . It was found that the annealed In 2 O 3 TFTs exhibited high field-effect mobility ( μ FE > 40 cm 2 V −1 s −1 ), high on/off current ratio ( I on/off ∼ 10 8 ), and controlled threshold voltage ( V TH ) for the enhancement- and depletion-mode operations. Note that the annealing atmosphere has a significant effect on the electrical performance of the In 2 O 3 TFTs by inducing changes in oxygen-related species, particularly oxygen vacancies (V O ) and hydroxyl/carbonate species (O–H/C–O). For the O 2 -, Ar-, FG-, and N 2 -annealed TFTs, μ FE was in increasing order accompanied by a negative shift in V TH , which is a result attributed to the larger V O in the In 2 O 3 thin films. Furthermore, the Δ V TH of the FG-, and N 2 -annealed TFTs in a positive bias stress test was greater than that of the O 2 -, Ar-annealed devices, attributing to their lower density of O–H/C–O groups in the In 2 O 3 thin films. Our results suggest that the annealing atmosphere contributes to the internal modifications of the In 2 O 3 structure and in turn altered the electrical characteristics of TFTs. These annealed In 2 O 3 TFTs with high performance are promising candidates for realizing large-area, transparent, and high-resolution displays.