Endurance and Retention Degradation of Intermediate Levels in Filamentary Analog RRAM

The understanding of the retention and endurance degradation behavior of different levels of filamentary analog RRAM is critical for the development of the neuromorphic computing. This paper investigates the conductance distribution of different levels during retention and endurance tests. The low conductance states and high conductance states change from the normal distribution at the beginning to asymmetric skewed distribution with baking time increasing. But intermediate states remain the normal distribution. A model is proposed to predict the conductance evolution of different levels. It is also found that endurance lifetime depends on the ratio and position of endurance window. The longer endurance lifetime is attributed to switching in a smaller high-C window. Physical mechanism of endurance degradation is discussed.