Investigation of Filamentary Current Fluctuations Features in the High-Resistance State of Ni/HfO<inf>2</inf>-Based RRAM

© 1963-2012 IEEE. In this paper, the presence of filamentary current instabilities in the high resistance state of Ni/HfO2-based RRAM devices and their associated current fluctuations mechanisms are explored. After systematic measurements, the advanced weighted time-lag plot method is employed to accurately identify the contribution of multiple electrically active defects and to minimize the negative effect of the background noise. Special attention is given to the physical analysis of multilevel random telegraph noise (RTN) signals caused by both independent and interactive defects located in the vicinity of the conductive filament (CF), which may alter the tunneling path and induce large stochastic current fluctuations. In addition, irreversible current changes, owing to trap density variations inside or near the CF, are also identified. Finally, the voltage dependence of the RTN phenomena and the occurrence of stress-induced complex fluctuations is evaluated.