Origin of the deep reset and low variability of pulse-programmed WAl2O3TiWCu CBRAM device

In this paper we demonstrate for the first time the origin of the deep reset and low switching variability obtained on pulse-programmed (100ns) 90nm-size WAl₂O₃TiWCuCBRAM device operated at 10 μA. To this aim we develop a Quantum-Point-Contact (QPC) model describing the conduction of the CBRAM states down to deep current levels, allowing to estimate the effective size of the defect particles in the QPC constriction. The model clearly points to smaller particles for CBRAM (Cu particles) as compared to OxRRAM (oxygen-vacancy Vo defects). As a consequence, smaller constrictions (thus larger resistance) may be obtained in CBRAM after reset. In addition, the fluctuation of the number of these small Cu particles in the constriction has lower impact on Random-Telegraph-Noise (RTN), as compared to Vo defects. Finally, the lower switching variability obtained for CBRAM as compared to OxRRAM is also attributed to the larger mobility of Cu ions as compared to V_o particles in Al₂O₃ medium.