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

Cheng-Li Lin,Tse-Yu Lin

doi:10.1063/1.4943508

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.

Highlights

INTRODUCTIONWhen charge-storage memory continuously scales down, the memory suffers a charge loss and/or eventually reaches its technical and physical limitations.[1,2] Of late, in order to meet the requirements of low power, high speed, small sized and low cost memory technology, the resistive
When charge-storage memory continuously scales down, the memory suffers a charge loss and/or eventually reaches its technical and physical limitations.[1,2] Of late, in order to meet the requirements of low power, high speed, small sized and low cost memory technology, the resistiveRAM is considered the most promising candidate because of its simple structure, small dimensions,[3] high packing density and low power consumption.[4]
After the first dc sweeping measurement, the low resistance state (LRS) turned into a high resistance state (HRS) at the RESET voltage

Summary

INTRODUCTION

When charge-storage memory continuously scales down, the memory suffers a charge loss and/or eventually reaches its technical and physical limitations.[1,2] Of late, in order to meet the requirements of low power, high speed, small sized and low cost memory technology, the resistive. Using the oxygen-deficient HfOx film as a switching layer is beneficial in improving the RRAM switching performance. In oxygen deficient TiOx and ZrOx layers, when capped by Ti electrode capping, the TiOx acts as an oxygen reservoir in a series with an oxygen-deficient ZrOx layer and improves the endurance cycle of ZrO2 RRAM in BRS,[23] but not in URS. For improvement in URS, a new stack ZrOx/ZrO2/ZrOx structure is proposed by this study. A thin ZrOx film with less oxygen was used as a capping on the ZrO2 to form an Al/ZrOx/ZrO2/ZrOx/Al sandwich structured RRAM (denoted as the ZrO2 stack RRAM). This capping showed superior endurance and an obvious performance improvement in unipolar operations for the stack RRAM. The recovery effect of the HRS was observed and studied

EXPERIMENT

RESULTS AND DISCUSSION

CONCLUSION