MA BE-SONOS: A Bandgap Engineered SONOS using Metal Gate and Al2O3 Blocking Layer to Overcome Erase Saturation

A bandgap engineered SONOS (BE-SONOS) (Lue et al., 2005) using Al₂O₃ top blocking layer and metal gate (MA BE-SONOS) is proposed to provide very fast erase speed without erase saturation. Compared with MANOS (Shin et al., 2005) using a thick (4.5 nm) tunnel oxide, MA BE-SONOS shows dramatically faster erase speed, owing to the help of bandgap engineered ONO barrier that facilitates hole tunneling. Compared with BE-SONOS using P⁺-poly gate and top oxide, MA BE-SONOS does not show any erase saturation, owing to the help of metal gate and AI₂O₃ blocking layer, which greatly reduce gate injection during erase. Very large memory window (>7 V) can be achieved with excellent data retention. MA BE-SONOS overcomes the erase difficulty in SONOS-type devices, and is highly potential in the future flash memory technology.