Characteristics of Resistive Memory Read Fluctuations in Endurance Cycling

We report on new fluctuation dynamics of the high resistance state of Hafnia-based RRAM devices after RESET. We observe that large amplitude fluctuations occur more frequently immediately after programming and their frequency of occurrence decays in the tens of microseconds. The fluctuation amplitude, on the other hand, does not decay noticeably over the entire millisecond read time. While post-programming instability and post-programming resistance dispersion have both been reported in the literature, the relaxation in the frequency of occurrence without a commensurate amplitude decay is new. Since picosecond pulses were used for our RESET operation, post-programming thermalization occurs on the nanosecond time scale. This clearly eliminates a thermally driven mechanism as the cause of the observed fluctuation behavior. Furthermore, reducing the READ voltage by tenfold does not have any effect and also eliminates read disturb as possible cause.