Back-end-of-line-compatible low-voltage operation in Hf0.5 Zr0.5O2 ferroelectric film enabled by in-situ lanthanum doping

HfO₂-based ferroelectric devices have attracted substantial attention in non-volatile memories due to their sub-3 nm scalability and robust ferroelectric properties. However, challenges such as double remanent polarization (2P _r) degradation and high thermal budget have hindered their integration as advanced technology nodes. Here, we developed an in-situ lanthanum doping strategy in ferroelectric capacitors to address these issues. By controlling the atomic layer deposition pulses of La₂O₃, HfO₂ and ZrO₂, the lanthanum-doped HZO (La: HZO) film with different lanthanum concentrations were prepared. An ultra-low thermal budget below 300°C was demonstrated in the 0.44% La: HZO film, while maintaining a pronounced 2P _r of 27.8 μC/cm². First-principles calculations suggest that lanthanum incorporation promotes the formation of oxygen vacancies, which is believed to stabilize the orthorhombic phase and activate ferroelectricity in the La: HZO films. Furthermore, the back-end-of-line compatible capacitor with La: HZO also exhibits a low operating voltage of 2.0 V, excellent ferroelectricity with 2P _r of 37.5 μC/cm², rapid switching speed of 446 ns, record-high breakdown voltage of 5.73 V, superior endurance properties over 10¹¹ cycles and substantial retention. These results provide new insights for the design of non-volatile memories with low power consumption and high operating speed.