Back-End of Line Compatible Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub>/ZrO<sub>2</sub>/Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> Stack Achieving 2P<sub>r</sub> of 39.6 μC/cm<sup>2</sup> and Endurance Exceeding 10<sup>10</sup> Cycles Under Low-Voltage Operation
Yin-Chi Liu, Ji-Ning Yang, Yuchun Li, Xinlong Zhou, Kangli Xu, Yu‐Chang Chen, Genran Xie, Hao Zhang, Lin Chen, Shi‐Jin Ding, Hong-Liang Lü, Wen-Jun Liu
Abstract
In this letter, the back-end of line (BEOL) compatible H0.5Z0.5O2/ZrO2/H0.5Z0.5O2 stack was designed for enhancing both the ferroelectricity and reliability under low-voltage operation. Compared to the conventional H0.5Z0.5O2(HZO) film, the HZO/ZrO2/HZO stack exhibits superior remnant polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{P}_{\text {r}}{)}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$39.6~\mu \text{C}$ </tex-math></inline-formula> /cm2 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$53.8~\mu \text{C}$ </tex-math></inline-formula> /cm2 under 2 MV/cm and 4 MV/cm, respectively. By integrating ZrO2 middle layer (ML) into HZO films, robust reliability was achieved, including a large breakdown electric field of 2.73 MV/cm in 10-year time-dependent dielectric breakdown (TDDB) lifetime, as well as excellent endurance characteristic with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2{P}_{\text {r}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$38.04~\mu \text{C}$ </tex-math></inline-formula> /cm2 after <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4}.{34}\times {10} ^{{9}}$ </tex-math></inline-formula> cycles at 2 MV/cm and no breakdown after <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${6}\times {10} ^{{10}}$ </tex-math></inline-formula> fatigue cycles at 1.5 MV/cm. It is believed that ZrO2 ML could introduce additional strain at a low annealing temperature below 350 °C and improve the proportion of the ferroelectric phase in the HZO/ZrO2/HZO stack. The HZO/ZrO2/HZO stack with low-voltage operation shows the great potential for BEOL-compatible non-volatile memory applications.