Causes and consequences of the stochastic aspect of filamentary RRAM

Filamentary resistive RAM devices are affected by various sources of instability and variability. Stochastic fluctuations, caused by variability of the RRAM-driving transistor and process-induced device-to-device variations, affect both forming and set/reset transients. Also the intrinsic stochastic mechanisms that control the filament growth and shrinkage complicate the set and reset operation. In particular, RRAM operated at low current shows very broad distributions of both the low and high resistive state. Furthermore, at low read voltage a large amplitude Random Telegraph Noise is measured, caused by both electrostatic modulation of the constricted current flow and by random perturbation of the vacancies in the filament. Additional variability arises from the stochastic probability of finding an intact or a ruptured filament in high resistive state at low current compliance. (C) 2015 Elsevier B.V. All rights reserved.