An Oxide-Buffered BE-MANOS Charge-Trapping Device and the Role of Al2O3

The role of AI₂O₃ in MANOS device is critically examined, and we conclude that its primary function is to reduce gate injection during erase operation. By itself, AI₂O₃ cannot stop charge leakage from the charge-trapping nitride layer. Furthermore, AI₂O₃ provides no magic during the erase operation, and MANOS erases very slowly through charge de-trapping. BE-SONOS [1], with the band engineered ONO tunneling layers, provides efficient channel hole injection for erase. BE-MANOS [2] should be an ideal combination with fast erase and good reliability. However, it shows poor data retention. By inserting a SiO₂ buffer layer between AI₂O₃ and the SiN storage layer, the oxide-buffered BE-MANOS shows good performance and good reliability. The EOT scalability is also investigated.