Endurance enhancement of ZnO RRAM through interfacial oxidation control and conduction mechanism analysis

Abstract

In this study, the reliability of ZnO RRAM with Ti electrodes is investigated, with a focus on the formation of titanium oxide (TiO_X) at the TiZnO interface. Electrical measurements, including DC sweep endurance tests, reveal that the TiO_X interfacial layer contributes to elevated high-resistance states and overall performance degradation. To directly observe interfacial composition, atom probe tomography (APT) was employed, providing high-resolution three-dimensional chemical mapping. The APT results confirmed that oxygen diffuses from the ZnO layer into the Ti electrode during operation, forming a distinct TiOx layer. To further understand the impact of this interfacial oxide on electrical behavior, we performed current–voltage fitting with Schottky emission models. These analyses indicated that the formation of the TiO_X layer increased the Schottky barrier height. To mitigate these phenomenon, we introduced a silicon carbon nitride (SiCN) layer between the ZnO and Ti electrodes, deposited via plasma-enhanced atomic layer deposition (PEALD). The SiCN layer acts as an effective oxygen diffusion barrier. Devices incorporating this layer exhibited significantly improved switching uniformity, enhanced endurance, and reduced cycle-to-cycle variability. The structural properties of the ZnO layer were verified using X-ray diffraction (XRD), and secondary ion mass spectrometry (SIMS) confirmed the suppression of oxygen migration. Although the SiCN barrier caused a slight increase in operating voltage, the overall improvement in device stability and reliability highlights the effectiveness of interface engineering. These findings offer valuable insight into interfacial control strategies for high-performance and reliable oxide-based RRAM devices.