Enhancement-Mode Atomic-Layer-Deposited In 2 O 3 Transistors With Maximum Drain Current of 2.2 A/mm at Drain Voltage of 0.7 V by Low-Temperature Annealing and Stability in Hydrogen Environment

In this article, we demonstrate atomic-layer-deposited (ALD) indium oxide (In2O3) transistors with a record high drain current of 2.2 A/mm at ${V}_{DS}$ of 0.7 V among oxide semiconductor transistors with the enhancement-mode operation. The impact of back-end-of-line (BEOL) compatible low-temperature annealing is systematically studied on these highly scaled In2O3 transistors with channel length ( ${L}_{ch}$ ) down to 40 nm, channel thickness ( ${T}_{ch}$ ) down to 1.2 nm, and equivalent oxide thickness (EOTs) of 2.1 nm, at annealing temperatures from 250 °C to 350 °C in N2, O2, and forming gas (FG, 96% N2/4% H2) environments. Annealing in all different environments is found to significantly improve the performance of ALD In2O3 transistors, resulting in enhancement-mode operation, high mobility, reduced bulk and interface trap density ( $\text{D}_{it}$ as low as $6.3\times 10^{11}$ cm $^{-2}\cdot $ eV−1), and nearly ideal subthreshold slope (SS) of 63.8 mV/dec. Remarkably, the ALD In2O3 devices are found to be stable in hydrogen environment, being less affected by the well-known hydrogen doping issue in indium–gallium–tin-oxide (IGZO). Therefore, low-temperature ALD In2O3 transistors are highly compatible with the hydrogen-rich environment in BEOL fabrication processes.