Enhanced reliability of HfO2-based conductive bridge random access memory through MgO insertion

Abstract

Conductive-bridge random access memory (CBRAM) has emerged as a promising candidate for next-generation non-volatile memory due to its simple structure, high scalability, and low power consumption. However, conventional HfO2-based CBRAM devices suffer from poor switching uniformity and volatility arising from the stochastic nature of filament formation and the high ionic mobility of HfO2. Herein, we demonstrate that the incorporation of an ionic-bonded oxide, MgO, into a bilayer architecture with HfO2 effectively enhances resistive switching performance. We performed thermal annealing to improve the crystallinity, which was confirmed by X-ray diffraction (XRD) analysis. The XRD and XPS results revealed that annealing enhanced crystallinity and increased the oxygen vacancy concentration in the HfO2 layer, both of which contributed to the suppression of cycle-to-cycle and device-to-device variations. Furthermore, the bilayer structure significantly impacts switching behavior depending on the oxide stacking order. In the Ag/HfO2/MgO/Pt device, ion accumulation at the HfO2/MgO interface promotes well-confined filament growth, enabling forming-free and highly uniform operation with enhanced retention stability. In contrast, the Ag/MgO/HfO2/Pt device suffers from limited ion mobility in the MgO layer, requiring an electroforming step for activation, which results in higher operating voltages, broader switching characteristics distributions, and reduced stability. XPS depth profiling reveals that controlled oxygen vacancy distributions and interfacial ion accumulation govern filament morphology and rupture sites, determining switching stability. As a result, the optimized bilayer device achieves reliable endurance, a high on/off ratio of ∼105, and low operating voltages, underscoring the potential of ionic oxides and interface engineering for practical non-volatile memory applications.