Novel tunneling dielectric prepared by oxidation of ultrathin rugged polysilicon for 5-V-only nonvolatile memories

A novel dielectric fabricated by thermal oxidation of ultrathin rugged polysilicon film is proposed for nonvolatile memories. Different roughness degrees for the top and bottom interfaces of this dielectric are detected by the atomic-force-microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). Due to the microtips formed at the bottom interface of the dielectric, significant improvements in the high conduction efficiency, low trapping rate, good uniformity, and high reliability under positive gate-bias are obtained for the dielectric. Therefore, rugged polyoxide is promising for future 5-V-only floating-gate applications.