A study of the switching mechanism and electrode material of fully CMOS compatible tungsten oxide ReRAM

摘要

Tungsten oxide (WO _X ) resistive memory (ReRAM), a two-terminal CMOS compatible nonvolatile memory, has shown promise to surpass the existing flash memory in terms of scalability, switching speed, and potential for 3D stacking. The memory layer, WO _X , can be easily fabricated by down-stream plasma oxidation (DSPO) or rapid thermal oxidation (RTO) of W plugs universally used in CMOS circuits. Results of conductive AFM (C-AFM) experiment suggest the switching mechanism is dominated by the REDOX (Reduction-oxidation) reaction—the creation of conducting filaments leads to a low resistance state and the rupturing of the filaments results in a high resistance state. Our experimental results show that the reactions happen at the TE/WO _X interface. With this understanding in mind, we proposed two approaches to boost the memory performance: (i) using DSPO to treat the RTO WO _X surface and (ii) using Pt TE, which forms a Schottky barrier with WO _X . Both approaches, especially the latter, significantly reduce the forming current and enlarge the memory window.