Superior unipolar resistive switching in stacked ZrOx/ZrO2/ZrOx structure

Abstract

This study investigates the performance of unipolar-switched ZrO2 RRAM, using an oxygen-deficient and amorphous ZrOx capping in a sandwich stack Al/ZrOx/ZrO2/ZrOx/Al structure. Superior high and low resistance switching and a resistance ratio (HRS/LRS) greater than 10 showed excellent dc endurance of 7378 switching cycles and 3.8 × 104 cycles in pulse switching measurements. Recovery behavior, observed in the I-V curve for the SET process (or HRS), led to HRS fluctuations and instability. A new resistance switching model for the stacked ZrO2 RRAM is proposed in this paper. In this model, oxygen-deficient and amorphous ZrOx film, capped on polycrystalline ZrO2 film, plays a key role and acts as an oxygen reservoir in making the oxygen ions redox easily for the SET process and in facilitating re-oxidation for the RESET process, resulting in excellent endurance. By improving the stability and recovery phenomena, engineering parameters of the current control may play a critical role during switching, and they can be correlated to the film’s thickness and the oxygen content of the amorphous ZrOx film.

Selection by current compliance of negative and positive bipolar resistive switching behaviour in ZrO2−x/ZrO2bilayer memory

“…Recently, ZrO2-based RRAM has become increasingly investigated because of its high thermodynamic stability, large bandgap, high dielectric constant and compatibility with the CMOS process [10][11][12][13]. Both unipolar and bipolar switching behaviour based on ZrO2 have been reported in previous works [14][15][16][17].…”

Intrinsic RESET speed limit of valence change memories

“…This unipolar switching mode has already been observed for TaO x - [48] and ZrO x -based devices [49], but has never been considered as failure meachanism for neither the RESET kinetics, nor the endurance. It can be triggered by applying a positive voltage to the active electrode, with a higher amplitude compared to the RESET.…”

A Process-Aware Memory Compact-Device Model Using Long-Short Term Memory

“…In (10)- (14), the symbols, f corresponds to the forget gate, i corresponds to the input gate, o corresponds to the output gate, σ is the sigmoid activation, c is cell state, h is the hidden state, and t is the present time step. w is the weight, and b is the bias.…”

“…It is a twoterminal device in which an insulating layer is sandwiched between two metal layers, a typical metal-insulator-metal (MIM) structure. There is a wide variety of insulating materials, such as HfOx [7][8][9][10], ZnOx [11,12], and ZrOx [13,14], available in the fabrication of RRAM. The operation depends upon the formation and destruction of conducting filament in these insulating layers, and this corresponds to two important states of this device, i.e., low resistance state (LRS) and high resistance state (HRS).…”