Characteristics Improvement of In-Ga-Zn Oxide Thin-Film Transistors by Rapid Post-Annealing

The characteristics of amorphous In-Ga-Zn oxide thin-film transistor(a-IGZO TFT) were considerably improved by rapid post-annealing in N₂-atmosphere. The influence of the “heating-rate” in 400℃-annealing on the microstructures,electronic structures and properties was investigated with atomic force microscopy,X-ray photoelectron spectroscopy and semiconductor device analyzer. The results show that the heating-rate had a major impact. To be specific,as the heating-rate increased from 377℃/60 s to 377℃/10 s,the a-IGZO coatings became increasingly compact,because the grain-size,surface roughness and O-vacancy density decreased. Consequently,performance of the a-IGZO TFT was significantly improved. For example,a heating-rate of 37.7℃/s decreased the threshold-voltage and sub-threshold slope down to 0.2 V(by 67%) and 0.31 V·decade^-1(by 77%),respectively,and increased the carrier-mobility and on/off current-ratio up to 8.7 cm²/Vs(by 171%) and 7.8×10⁶(by 1.1×10³ times),respectively. Moreover,the post-annealing time was shortened to below 5 min.