Air Stable High Mobility ALD ZnO TFT with HfO2 Passivation Layer Suitable for CMOS-BEOL Integration

An air-stable ALD ZnO TFT with high field-effect mobility of 82 cm
²
/V·s and high on-off ratio of
$5\times 10^{7}$
is realized with an 18 nm thick channel. This is the highest reported mobility value using an ALD process with a low temperature of 200°C. With HfO
2
as a passivation layer, the TFT exhibits negligible electrical degradation even after 90 days of exposure in ambient air environment, paving the path for BEOL integration.