Investigation of switching mechanism in HfOx-ReRAM under low power and conventional operation modes.

Wei Feng,Kenji Ohmori,Hisashi Shima,Hiroyuki Akinaga

doi:10.1038/srep39510

Abstract

Low-power resistive random access memory (LP-ReRAM) devices have attracted increasing attention owing to their advantages of low operation power. In this study, a vertical-type LP-ReRAM consisting of TiN/Ti/HfO2/TiN structure was fabricated. The switching mechanism for LP-ReRAM was elucidated as the conductive filament mechanism for conventional mode, and an interface-type switching mechanism for low power mode was proposed. The analysis of low frequency noise shows that power spectral density (PSD) is approximately proportional to 1/f for conventional operation mode. Nevertheless, for low power mode, the PSD of low resistance state (LRS) is proportional to 1/f, while that of high resistance state (HRS) is clear proportional to 1/f2. The envelope of multiple Lorentzian spectra of 1/f2 characteristics due to different traps reveals the characteristics of 1/f. For HRS of low power mode, a limited number of traps results in a characteristic of 1/f2. During the set process, the number of oxygen vacancies increases for LRS. Therefore, the PSD value is proportional to 1/f. Owing to the increase in the number of traps when the operation mode changes to conventional mode, the PSD value is proportional to 1/f. To the best of our knowledge, this is the first study that reveals the different noise characteristics in the low power operation mode from that in the conventional operation mode.

Highlights

Reported a self-rectifying and self-compliant resistive random access memory (ReRAM) cell, which exhibits low operating currents[25]
conductive filament (CF) was not observed by electron beam absorbed current (EBAC), which is in support of an interface type switching mechanism for low-power mode
The limited number of oxygen ions near the Ti/HfO2 interface contributes to the resistive switching under low power mode

Summary

Introduction

Reported a self-rectifying and self-compliant ReRAM cell, which exhibits low operating currents[25]. Shima et al previously found that the reliable bipolar resistance state (RS) can be demonstrated in the TiN/Ti/HfO2/TiN ReRAM structure by introducing post deposition annealing (PDA) process[27]. This result implies that the control of the redox reaction in the ReRAM cell is crucial to obtain the optimum operating performance of this memory. On the other hand, limited number of oxygen ions near the Ti/HfO2 interface contributes to the low-power resistive switching. In this latter case, the electric field becomes the dominant driving force for the oxygen ion movement. The noise characteristics were examined for LRS and HRS under two operation modes of LP-ReRAM

Methods

Results

Conclusion