Implications of the Incremental Pulse and Verify Algorithm on the Forming and Switching Distributions in RERAM Arrays

In this paper, the implication of an incremental pulse and verify (IPV) algorithm onto the Forming, Set, and Reset read current distributions is studied in terms of the intercell variability and the reliability of 4-kb RERAM arrays with a Ti/HfO2/Ti/TiN stack. It is shown that the IPV algorithm causes an initial generalized Pareto distribution (GPD) for Forming, Set, and Reset current. Due to the read-induced fluctuations, the GPD evolves to a bimodal distribution for all the cases. The separation value between the two distributions coincides with the threshold current of the IPV algorithm. The main problem arises from the minor distribution, which does not respect the algorithm stop condition. The percentage of the unwanted minor distribution is in the order of a few percentage points for Reset and lower than 1% for Set.