Bias Stress Stability of ITO Transistors and its Dependence on Dielectric Properties

Amorphous oxide semiconductors (AOS) can be processed at low-temperature and their field-effect transistors (FETs) have demonstrated very low off-state current [1], offering promise for low-power back-end-of-line (BEOL) applications. Indium tin oxide (ITO) FETs have recently shown good characteristics [2] and good mobility (>50 cm
²
V
⁻¹
s
⁻¹
[3]), but their stability and degradation remain unknown, e.g. given the mobility-stability trade-off in AOS [4], [5]. Here we investigate, for the first time, the influence of gate dielectric material and thickness on ITO-FET stability, which impacts bias stress through trap states. We find that HfO
2
is more stable than Al
2
O
3
as a gate dielectric for ITO FETs, which contradicts previous stability studies of other AOS.