Enhanced Ferroelectricity and Reliability in Sub-6 nm Ferroelectric Hf_0.5Zr_0.5O₂/ZrO₂/Hf_0.5Zr_0.5O₂ Stack Film Compatible with BEOL Process

In this work, the back-end of line (BEOL) compatible sub-6 nm Hf 0.5 Zr 0.5 O 2 /ZrO 2 /Hf 0.5 Zr 0.5 O 2 (HZO/ZrO 2 /HZO) stack and the corresponding capacitors were fabricated. The capacitor with the sub-6 nm HZO/ZrO 2 /HZO stack annealed at 400 °C shows a superior remanent polarization (2 P r ) of 26.3 μC/cm 2 under only ±1.25 V sweeping, while the conventional HZO film presents nonferroelectricity. The enhanced ferroelectricity stems from the increased ferroelectric phase proportion with ZrO 2 insertion. Moreover, the capacitor with a HZO/ZrO 2 /HZO stack also achieved an excellent endurance with a 2 P r of 27.1 μC/cm 2 after 10 11 cycles without breakdown and only ∼12% 2 P r degradation at 85 °C. The robust reliability is ascribed to the suppressed generation of defects and domain pinning under the low operating voltage. The sub-6 nm HZO/ZrO 2 /HZO stack presents great potential for BEOL compatible nonvolatile memories in advanced process nodes.