Demonstration of Wake-Up Free 6 nm Ultrathin ZrO-HfO Superlattice Ferroelectric Capacitors with High Endurance Against Fatigue

This study presents the ferroelectric polarization stability characteristics of ultrathin (6 nm) superlattice (SL) ferroelectric layer metal-ferroelectricmetal (MFM) capacitors fabricated with varying ferroelectric layer stacks. Notably, ZrO2-HfO2 SL MFM capacitors with 1 nm ZrO2 as the starting layer exhibited enhanced polarization stability characterized by nearly wake-up free and fatigue-free behavior. The research demonstrates the deposition of ZrO2-HfO2 superlattice by atomic layer deposition (ALD), resulting in highly stable remanent polarization (2Pr @3.3 MV/cm) of approximately 30 μC/cm2. The variation remained small (Δ2Pr ≤ 2.5 μC/cm2; Δ2Pr/2Pr, pristine ≤ 8%) over an impressive 1010 cycles of field cycling. This result is a crucial technique to address the polarization instability commonly reported in ultrathin (≤ 6 nm) Hf0.5Zr0.5O by utilizing the SL structure to achieve nearly wake-up free and fatigue-free polarization performance up to 1010 cycles.