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.