Low-Temperature Growth of Indium Oxide Thin Film by Plasma-Enhanced Atomic Layer Deposition Using Liquid Dimethyl(N-ethoxy-2,2-dimethylpropanamido)indium for High-Mobility Thin Film Transistor Application

Low-temperature growth of InO films was demonstrated at 70-250 °C by plasma-enhanced atomic layer deposition (PEALD) using a newly synthesized liquid indium precursor, dimethyl(N-ethoxy-2,2-dimethylcarboxylicpropanamide)indium (MeIn(EDPA)), and O plasma for application to high-mobility thin film transistors. Self-limiting InO PEALD growth was observed with a saturated growth rate of approximately 0.053 nm/cycle in an ALD temperature window of 90-180 °C. As-deposited InO films showed negligible residual impurity, film densities as high as 6.64-7.16 g/cm, smooth surface morphology with a root-mean-square (RMS) roughness of approximately 0.2 nm, and semiconducting level carrier concentrations of 10-10 cm. Ultrathin InO channel-based thin film transistors (TFTs) were fabricated in a coplanar bottom gate structure, and their electrical performances were evaluated. Because of the excellent quality of InO films, superior electronic switching performances were achieved with high field effect mobilities of 28-30 and 16-19 cm/V·s in the linear and saturation regimes, respectively. Furthermore, the fabricated TFTs showed excellent gate control characteristics in terms of subthreshold swing, hysteresis, and on/off current ratio. The low-temperature PEALD process for high-quality InO films using the developed novel In precursor can be widely used in a variety of applications such as microelectronics, displays, energy devices, and sensors, especially at temperatures compatible with organic substrates.