High-k Hf-Based Nanocrystal Memory Capacitors with IrOx Metal Gate for NAND Application

The memory characteristics of atomic layer deposited high-kappa Hf-based nanocrystals embedded in high-kappa Al₂O₃ films in an n-Si/SiO₂/HfO₂/high-k nanocrystal/Al₂O₃/IrO_x memory structure have been investigated. The high-k nanocrystals can be formed after high temperature (> 900degC) annealing process. The high-k nanocrystal memory devices with a small EOT of ~8 nm show a large hysteresis memory window of DeltaV ap 3.8 V at a sweeping gate voltage of plusmn9 V, 0.2 s. A hysteresis memory window of 0.9 V has also been observed under a small sweeping gate voltage of plusmn7 V. A good uniformity of the high-k nanocrystal memory devices is also observed. A large memory window of >2 V and a low charge loss of 14% are achieved after ~8 times 10⁵ s (9 days) of retention time owing to the charge confinement in the high-k nanocrystals.