A Physical Model for the Statistics of the Set Switching Time of Resistive RAM Measured With the Width-Adjusting Pulse Operation Method

The correlation between the set time (t_set) and the initial off-state resistance (R_OFF) statistics for a Ti/ZrO₂/Pt bipolar resistive random access memory device was investigated. The width-adjusting pulse operation method, which can significantly improve the switching uniformity, was used to accurately measure t_set, and the gathered statistical data were analyzed using Weibull distributions. Both the Weibull slope (β_t) and the scale factor (t_set63%) of tset distributions were found to increase logarithmically with R_OFF. The observed t_set - R_OFF interdependence provides a guideline in improving the switching uniformity and optimizing the tradeoff between set speed and disturb immunity. An analytical cell-based model was developed to explain the R_OFF-dependent t_SET statistics, which can be implemented in statistical compact models and circuit simulators for improving RRAM cell design and memory performances.