Enhanced Ferroelectricity and Reliability in Sub-6 nm Ferroelectric Hf0.5Zr0.5O2/ZrO2/Hf0.5Zr0.5O2 Stack Film Compatible with BEOL Process

In this work, the back-end of line (BEOL) compatible sub-6 nm Hf0.5Zr0.5O2/ZrO2/Hf0.5Zr0.5O2 (HZO/ZrO2/HZO) stack and the corresponding capacitors were fabricated. The capacitor with the sub-6 nm HZO/ZrO2/HZO stack annealed at 400 °C shows a superior remanent polarization (2Pr) of 26.3 μC/cm2 under only ±1.25 V sweeping, while the conventional HZO film presents nonferroelectricity. The enhanced ferroelectricity stems from the increased ferroelectric phase proportion with ZrO2 insertion. Moreover, the capacitor with a HZO/ZrO2/HZO stack also achieved an excellent endurance with a 2Pr of 27.1 μC/cm2 after 1011 cycles without breakdown and only ∼12% 2Pr 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/ZrO2/HZO stack presents great potential for BEOL compatible nonvolatile memories in advanced process nodes.