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.