Unipolar Switching Behaviors of RTO $\hbox{WO}_{X}$ RRAM

The microstructure and electrical properties of the WO
_X
-based resistive random access memory are investigated in this letter. The WO
_X
layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WO
_X
layer and result in a low initial resistance. This letter studies the unipolar operation- the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10
⁷
times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.