ZrO2 insulator modified by a thin Al2O3 film to enhance the performance of InGaZnO thin-film transistor

A high-performance InGaZnO (IGZO) thin-film transistor (TFT) with ZrO 2 –Al 2 O 3 bilayer gate insulator is fabricated. Compared to IGZO-TFT with ZrO 2 single gate insulator, its electrical characteristics are significantly improved, specifically, enhancement of I on / I off ratios by one order of magnitude, increase of the field-effect mobility (from 9.8 to 14 cm 2 /Vs), reduction of the subthreshold swing from 0.46 to 0.33 V/dec, the maximum density of surface states at the channel-insulator interface decreased from 4.3 × 10 12 to 2.5 × 10 12 cm − 2 . The performance enhancements are attributed to the suppression of leakage current, smoother surface morphology, and suppression of charge trapping by using Al 2 O 3 films to modify the high- k ZrO 2 dielectric.