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

This study systematically investigates the influence of hydrogen incorporation in Al₂O₃ 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 100–250 ℃, the hydrogen concentration within the Al₂O₃ 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 cm²/V·s, 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 to 73.7 mV/dec. For PBTS evaluation, the device with Al₂O₃ deposited at 200 ℃ demonstrates superior stability, with a threshold voltage shift of only −15.4 mV at 125 ℃ after 10⁴ 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.