Excellent Ferroelectric Properties of Hf0.5Zr0.5O2 Thin Films Induced by Al2O3 Dielectric Layer

Abstract

The ferroelectricity of Hf0.5Zr0.5O2 (HZO) thin films has been usually reported to be induced by metallic capping layer. In this work, we successfully obtained ferroelectricity of HZO thin films induced by ultrathin insulating Al2O3 capping layers. The ferroelectric properties of HZO thin films induced by Al2O3 capping layers with different thickness have been investigated. It was found that the Al2O3(2 nm)/HZO (20 nm) stack shows excellent ferroelectric properties. The Au/Al2O3(2 nm)/HZO (20 nm)/TiN capacitor exhibits a very low leakage current of $\sim {4.2}\times {10}^{\text {-9}}$ A at 4 V and a maximum $2{P}_{r}\approx 32.3~\mu \text{C}$ /cm2 at sweeping voltages between ±8 V. In addition, the capacitor also shows excellent endurance properties up to 108 cycles. Our work demonstrated that dielectric films like Al2O3 can be adopted to be used as capping layer to generate excellent ferroelectric properties of HfO2-based thin films, which will contribute to their future applications in ferroelectric memory and negative capacitance transistors.