Nanoscale (EOT = 5.6 nm) nonvolatile memory characteristics using n-Si/SiO₂/HfAlO nanocrystal/Al₂O₃/Pt capacitors

The charge storage characteristics of the high-κ HfAlO nanocrystal memory capacitors prepared by atomic layer deposition in an n-Si/SiO ₂/HfAlO/Al₂O₃/Pt structure have been investigated after high-temperature annealing treatment. The high-resolution transmission electron microscopy image shows that the diameter of high-κ HfAlO nanocrystal is<2 nm. The high-κ HfAlO nanocrystals have been also confirmed by x-ray photoelectron spectroscopy measurement. Due to the formation of high-κ HfAlO nanocrystals with the high-temperature (∼900°C) annealing treatment, a large hysteresis memory window of 3.7 V at a sweeping gate voltage <10 V is observed as compared to that of the as-deposited memory capacitors. A hysteresis memory window of ∼1.7 V with a small sweeping gate voltage of ±5 V is also observed. A small equivalent oxide thickness (EOT) of 5.6 nm is obtained due to the high-κ memory structure design. A significant memory window of ΔV≈0.7 V at 20°C and ΔV≈0.6 V at 85°C is observed after 10⁴ s of retention time, due to the charge confinement in the high-κ HfAlO nanocrystals.