Improved Retention Characteristics of Metal-Ferroelectric-Insulator-Semiconductor Structure Using a Post-Oxygen-Annealing Treatment

Abstract

An oxygen-annealing process after SrBi2Ta2O9 (SBT) ferroelectric film deposition has effectively improved retention properties of the metal-ferroelectric-insulator-semiconductor (MFIS) structure for FET-type ferroelectric nonvolatile memory. The annealing treatment 1) reduces the surface roughness of the SBT film, 2) improves crystallinity, 3) effectively decreases the leakage current through the MFM structure, 4) increases the barrier height at the metal-ferroelectric interface, 5) decreases the carrier trap density in SBT film, and 6) improves the retained polarization of SBT film itself. Finally, the retention time of the memorized state in the MFIS diode was successfully increased to 2×104 s or more by the postannealing treatment.