Physical and memory characteristics of atomic-layer-deposited high-κ hafnium-aluminum-oxide Nanocrystal Capacitors with Iridium-Oxide Metal Gate

The physical and memory characteristics of high-k: hafnium-aluminum-oxide (HfAlO) nanocrystals in an n-Si/SiO₂/HfO₂/Al ₂O₃/iridium- oxide (IrO_x) structure have been investigated. The high-/k HfAlO nanocrystal in the SiO₂/HfO ₂/Al₂O₃ layers is formed owing to the diffusion of Al₂O₃ and HfO₂ films after high-temperature annealing at 900 °C. High-k HfAlO nanocrystals with a small diameter of 5nm and a high density of 1.7 x 10¹² cm^-2 have been confirmed by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Owing to the formation of high-k HfAlO nanocrystals, a large hysteresis memory window of △ ∨ ≈ 4.4 V at a sweeping gate voltage of ±10 V is observed compared with that of as-deposited memory capacitor. A hysteresis memory window of △ ∨ ≈1.4 V with a small sweeping gate voltage of ±7 V is also observed. Good endurance of 10⁴ cycles with a large memory window of △ ∨ ≈3.6 Vis obtained. A significant memory window of △ ∨ ≈1.3 V is observed after a retention time of 5 x 10⁴ s, owing to the charge confinement in the high-k HfAlO nanocrystals.