Enhancement-Mode Atomic-Layer-Deposited In₂O₃ 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-layerdeposited (ALD) indium oxide (In 2 O 3 ) 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-endof-line (BEOL) compatible low-temperature annealing is systematically studied on these highly scaled In 2 O 3 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 N 2 , O 2 , and forming gas (FG, 96% N 2 /4% H 2 ) environments. Annealing in all different environments is found to significantly improve the performance of ALD In 2 O 3 transistors, resulting in enhancement-mode operation, high mobility, reduced bulk and interface trap density (Dit as low as 6.3 × 10 11 cm -2 ·eV -1 ), and nearly ideal subthreshold slope (SS) of 63.8 mV/dec. Remarkably, the ALD In 2 O 3 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 In 2 O 3 transistors are highly compatible with the hydrogen-rich environment in BEOL fabrication processes.