HAO + Al₂O₃ FeFET Gate-Stack for Overall Improvement in Operating Voltage, Endurance, and Retention

Hafnium oxide (HfO2)-based ferroelectric (FE) field-effect transistor (FeFET) is considered as one of the most promising candidates for future embedded non-volatile memory (eNVM). However, the application of HfO2-based FeFET is still limited by the high operating voltage and poor endurance. To address these problems, we developed a novel co-optimization design of the FE layer and the interlayer (IL) in the FeFET gate-stack. In the proposed Hf0.95Al0.05O2 (HAO) + Al2O3 structure, the conventional zirconium-doped HfO2 (HZO) is replaced by HAO, which has a smaller coercive field to reduce the bias stress, while the IL is optimized by replacing the SiOx formed by oxygen diffusion with a high-quality atomic layer deposition (ALD) Al2O3 layer to mitigate charge trapping and FE depolarization. We achieved an overall improvement in memory performance, resulting in a low operating voltage of +4 V, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\mu $ </tex-math></inline-formula> s and −3 V, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu $ </tex-math></inline-formula>s, high endurance of more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{9}}$ </tex-math></inline-formula> cycles, and retention time of over ten years at room temperature. This work helps push forward the development of low voltage and high endurance FeFETs.