Next generation memory requires more aggressive scaling down of tunneling oxide to improve performance. Thin tunneling oxide allows low power operation, high speed, and high density. However, FLASH memory will be faced with shrink limitation of tunneling oxide soon. Nanocrystal memory has been emerging as a strong candidate for next generation memory. However, retention degradation is remained unsolved problem especially in case of 3~4 nm tunneling oxide. In this work, we will introduce new material, new fabrication process to improve retention characteristic.
ZnO in nanostructure is reported to have high work function. We deposited high density ZnO nanocrystals by two-step CVD process which can minimize damage to tunneling oxide.
Fabricated MOS device show high performance with 10years retention.
Finally, by stacking double layer ZnO nanocrystals, we achieve more improvement.