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 In 2 O 3 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 (Me 2 In(EDPA)), and O 2 plasma for application to high-mobility thin film transistors. Self-limiting In 2 O 3 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 In 2 O 3 films showed negligible residual impurity, film densities as high as 6.64–7.16 g/cm 3, smooth surface morphology with a root-mean-square (RMS) roughness of approximately 0.2 nm, and semiconducting level carrier concentrations of 10 17 –10 18 cm –3 . Ultrathin In 2 O 3 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 In 2 O 3 films, superior electronic switching performances were achieved with high field effect mobilities of 28–30 and 16–19 cm 2 /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 In 2 O 3 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.