Tailoring Al₂O₃ deposition temperature for enhanced electrical performance and reliability of IGZO thin-film transistors

Abstract This study systematically investigates the influence of hydrogen incorporation in Al 2 O 3 gate dielectrics on the electrical characteristics and positive bias temperature stress (PBTS) reliability of amorphous indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs). By varying the atomic layer deposition (ALD) temperature in the range of 100 °C–250 °C, the hydrogen concentration within the Al 2 O 3 gate dielectrics is effectively suppressed, as confirmed by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Increasing the ALD temperature yields notable improvements in device performance: the average field-effect mobility increases from 23.3 to 30.2 cm 2 V −1 · s −1 , the average threshold voltage shifts positively from −0.36 V to −0.03 V, and the average subthreshold swing reduces from 83.3 mV dec −1 to 73.7 mV dec −1 . For PBTS evaluation, the device with Al 2 O 3 deposited at 200 °C demonstrates superior stability, with a threshold voltage shift of only −15.4 mV at 125 °C after 10 4 s of electrical stress. This device achieves the best balance of electrical performance and PBTS reliability, highlighting its suitability for robust and stable IGZO TFT applications.