Back-End of Line Compatible Hf_0.5Zr_0.5O₂ With ZrO₂ Seed Layer for Enhanced Ferroelectricity

In this letter, four ferroelectric (FE) capacitors with thickness dependent ZrO ₂ seed layer (SL) were designed and fabricated at a low annealing temperature below 350 °C. By modulating the thickness of ZrO ₂ SL, it is demonstrated that the FE capacitor with 1 nm ZrO ₂ SL exhibits a superior remnant polarization ( $2{P} _{r}$ ) of $44.1 ~\mu \text{C}$ /cm ² under 3 MV/cm at 1 kHz and $2{P} _{r}$ of $17.6 ~\mu \text{C}$ /cm ² after $10^{{9}}$ cycles at 3 MV/cm. It is found that the 1 nm ZrO ₂ SL provides more growth sites for the Hf _0.5 Zr _0.5 O ₂ (HZO) thin films, and enhances the ratio of the ferroelectric phases during crystallization, thereby leading to enhancement of its ferroelectricity and reliability. This work provides a robust solution to improve both ferroelectricity and endurance for future ferroelectric device compatible with back end of line (BEOL) process.