Back-End of Line Compatible Hf0.5Zr0.5O₂ 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 ( <tex-math notation="LaTeX">2P ᵣ </tex-math> ) of <tex-math notation="LaTeX">44.1 ~μ C </tex-math> /cm 2 under 3 MV/cm at 1 kHz and <tex-math notation="LaTeX">2P ᵣ </tex-math> of <tex-math notation="LaTeX">17.6 ~μ C </tex-math> /cm 2 after <tex-math notation="LaTeX">10^9 </tex-math> 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.