Uniform 3D vertical AlOδ/Ta2O5−x/TaOy RRAM: Fabrication, characterization and mechanism analysis

3D AlOδ/Ta2O5−x/TaOy RRAM structure with three vertical cells is demonstrated. The devices maintain good performance in endurance (>10⁸ cycles) and retention (>10⁴s @85°C) in comparison with planar devices. The cells in different layers also exhibits excellent uniformity in SET/RESET voltages, HRS and LRS distributions. To further increase data storage density, large HRS/LRS resistance window (>1000) and uniform 4 levels MLC operations are achieved. Moreover, temperature dependent study reveals the conductive filament rupture and formation resistive-switching mechanism, which predicts the future scaling down potential.