Low-temperature high-performance In-Ga-Sn-O thin-film transistors with Al2O3 grown by a facile dual-atomic layer deposition

Abstract

Top gate In-Ga-Sn-O (IGTO) thin-film transistors were fabricated with aluminum oxides (Al2O3) as gate insulators at a low temperature of 150 °C. Threshold voltage (Vth) of IGTO TFTs with Al2O3 grown by plasma-enhanced atomic layer deposition (PEALD) increased from 5.2 to 11.5 V with increasing plasma power from 70 to 200 W. However, IGTO TFTs with Al2O3 grown by thermal ALD showed a conductor-like behavior. By adjusting dual-deposition cycle ratio of Al2O3 layer using a sequential process of PEALD and thermal ALD at 150 °C, IGTO TFTs exhibited excellent electrical characteristics, with as field-effect mobility of 36.7 cm2V−1s−1, a Vth of 0.5 V, and a subthreshold slope of 0.18 Vdec−1 along with large improvement of electrical stability for gate bias stress. Results of analyses of secondary ion mass spectrometry and X-ray photoelectron spectroscopy of IGTO thin films revealed that the performance and electrical stability of low-temperature IGTO TFTs were strongly dependent on the amount of hydroxyl groups and oxygen vacancies in IGTO semiconductors possibly attributed to passivation of oxygen-related defects by hydrogen and water molecules diffused into the IGTO layer during thermal ALD of Al2O3.