Dual Al₂O₃/Hf₀.₅Zr₀.₅O₂ Stack Thin Films for Improved Ferroelectricity and Reliability

In this letter, a dual Al
₂
O
₃
/Hf
_0.5
Zr
_0.5
O
₂
(HZO) stack structure ferroelectric (FE) capacitor was designed and fabricated. It is found that the dielectric (DE) Al
₂
O
₃
thin film at the middle position of FE HZO thin films could apparently affect the behaviors of the oxygen vacancies at DE/FE interface and the electric field distribution, thereby affecting the corresponding ferroelectricity and reliability. By modulating the thickness of Al
₂
O
₃
middle layer (ML), it is demonstrated that the FE capacitor with 1 nm Al
₂
O
₃
ML exhibits better FE and cycling properties, including wake-up free, weaker fatigue effect, and robust endurance. Specifically, the device performs a considerable remnant polarization (
$2{P}_{\mathrm {r}}$
) of
$36.2 ~\mu \text{C}$
/cm
²
with a coercive electric field (
$2{E}_{\mathrm {c}}$
) of 2.7 MV and
$2{P}_{\mathrm {r}} > 20 ~\mu \text{C}$
/cm
²
after 10
¹⁰
cycles at 3 MV/cm. This work paves the pathway to optimize the ferroelectricity and reliability for future FE application.