Nonvolatile memory characteristics of a multi-stacked MOS capacitor using Ta₂O₅ and TaAlO₄ as the charge trap layer

A flash memory, which uses a floating-gate SiO₂/Si ₃N4/SiO₂ (ONO) structure for the next generation, non-volatile memory applications, has serious problems to overcome in the context of scaling down the device size. In this study, Al₂O ₃Ta₂O₅Al₂O₃ (ATA) and Al₂O₃/TaAlO₄/Al₂O₃ (A/TAO/A) multilayer films were fabricated to replace the conventional ONO structure. The structures and thicknesses of the multilayers were analyzed by HRTEM and ellipsometry. All films were found to be comprised of amorphous phases, and interfacial layers (AlSiO₃) were observed in both films. The electrical properties of the A/TAO/A films were better than those of the ATA films. Program/erase cycle tests were performed, and initial memory windows were maintained after 10⁴ program/erase cycles with both films.