High-Performance Atomic-Layer-Deposited Indium Oxide 3-D Transistors and Integrated Circuits for Monolithic 3-D Integration

In this work, we report the experimental demonstration of In
₂
O
₃
3-D transistors coated on fin structures and integrated circuits by a back-end-of-line (BEOL) compatible atomic layer deposition (ALD) process. High-performance planar back-gate In
₂
O
₃
transistors with high mobility of 113 cm
²
/
$\text{V}\cdot \text{s}$
and high maximum drain current (
${I}_{\rm D}$
) of 2.5 mA/
$\mu \text{m}$
are achieved by channel thickness engineering and postdeposition annealing. The high-performance ALD In
₂
O
₃
-based zero-
${V}_{\rm GS}$
-load inverter is demonstrated with a maximum voltage gain of 38 V/V and a minimum supply voltage (
${V}_{\rm DD}$
) down to 0.5 V. Top-gate indium oxide (In
₂
O
₃
) transistors by low-temperature ALD of both gate insulator and channel semiconductor are also demonstrated with
${I}_{\rm D}$
of
$570~\mu \text{A}/\mu \text{m}$
and low subthreshold slope (SS) down to 84.6 mV/decade. ALD In
₂
O
₃
3-D Fin transistors with the top-gate structure are then demonstrated, benefiting from the conformal deposition capability of ALD. These results suggest that ALD oxide semiconductors and devices have unique advantages and are promising toward BEOL-compatible monolithic 3-D integration for 3-D integrated circuits.