Low-Voltage and High-k Properties of Bilayer HZO Capacitors at the Morphotropic Phase Boundary for Next-Generation...

We report the phase stabilization and capacitance enhancement of electric-field-treated Hf_0.5Zr_0.5O₂ (HZO) bilayer capacitors near the morphotropic phase boundary (MPB). Compositional-asymmetric bilayer structures were fabricated by atomic layer deposition, followed by post-deposition annealing and electric-field cycling. The applied cycling induced irreversible phase transitions between the orthorhombic (o-) and tetragonal (t-) phases, effectively stabilizing the MPB region. A pronounced capacitor wake-up effect was observed, indicating self-optimization under repeated cycling. Structural analyses confirmed distinct bilayer formation and progressive phase evolution, while electrical measurements revealed an enhanced dielectric constant and increased remanent polarization. Importantly, the optimized bilayer exhibited a maximum dielectric constant of ∼52 at a reduced operating voltage of 2 V, along with improved endurance characteristics. These results demonstrate a viable strategy for engineering high-κ ferroelectric capacitors with low-voltage operation, making them promising candidates for advanced DRAM and nonvolatile memory applications.