Back-End of Line Compatible Hf0.5Zr0.5O2/ZrO2/Hf0.5Zr0.5O2 Stack Achieving 2Pr of 39.6 μC/cm2 and Endurance Exceeding 1010 Cycles Under Low-Voltage Operation

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 ( $2{P}_{\text {r}}{)}$ of $39.6~\mu \text{C}$ /cm2 and $53.8~\mu \text{C}$ /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 $2{P}_{\text {r}}$ of $38.04~\mu \text{C}$ /cm2 after ${4}.{34}\times {10} ^{{9}}$ cycles at 2 MV/cm and no breakdown after ${6}\times {10} ^{{10}}$ 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.