High-κ Hf-based nanocrystal memory capacitors with IrO_x metal gate for NAND application

The memory characteristics of atomic layer deposited high-K Hf-based nanocrystals embedded in high-κ Al₂O₃ films in an n-Si/SiO₂/HfO₂/high-κ nanocrystal/Al ₂O₃/IrO_x memory structure have been investigated. The high-κ nanocrystals can be formed after high temperature (>900°C) annealing process. The high-κ nanocrystal memory devices with a small EOT of ∼ 8 nm show a large hysteresis memory window of ΔV≈3.8 V at a sweeping gate voltage of ±9V, 0.2s. A hysteresis memory window of ΔV≈0.9 V has also been observed under a small sweeping gate voltage of ±7 V. A good uniformity of the high-κ nanocrystal memory devices is also observed. A large memory window of >2V and a low charge loss of 14% are achieved after ∼8×10⁵s (9 days) of retention time owing to the charge confinement in the high-κ nanocrystals.