Impact of Electrode Surface Morphology in ZnO-Based Resistive Random Access Memory Fabricated Using the Cu Chemical Displacement Technique

Electrochemical-metallization-type resistive random access memories (ReRAMs) show promising performance as next-generation nonvolatile memory. In this paper, the Cu chemical displacement technique (CDT) is used to form the bottom electrode of ReRAM devices. Compared with conventional deposition methods, the Cu-CDT method has numerous advantages for ReRAM fabrication, including low cost, low temperature fabrication, and the provision of unconsolidated Cu film and large surface roughness. Moreover, the Cu-CDT method is a favorable candidate for overcoming the Cu etching problem and is thus suitable for fabricating ReRAM devices. Using this technique, the surface morphology of a thin Cu film can be easily controlled. The obtained results show that the electric fields during the Forming and SET operations decreased, and the on-state current increased in the RESET operation, as the Cu-CDT displacement time was increased. The Cu-CDT samples exhibited a low operation field, large memory window (>10⁶), and excellent endurance switching cycle characteristics. Moreover, this paper proposes a model to explain the electrical characteristics of ReRAM, which are dependent on the surface morphology.