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Study of Multilevel High-Resistance States in HfOx-Based Resistive Switching Random Access Memory by Impedance Spectroscopy | IEEE Journals & Magazine | IEEE Xplore

Study of Multilevel High-Resistance States in HfOx-Based Resistive Switching Random Access Memory by Impedance Spectroscopy


Abstract:

Multilevel high-resistance states are achieved in TiN/HfOx/Pt resistive switching random access memory device by controlling the reset stop voltage. Impedance spectroscop...Show More

Abstract:

Multilevel high-resistance states are achieved in TiN/HfOx/Pt resistive switching random access memory device by controlling the reset stop voltage. Impedance spectroscopy is used to study the multilevel high-resistance states. It is shown that the high-resistance states can be described with an equivalent circuit consisting of the major components R_{s} , R , and C corresponding to the series resistance of the TiON interfacial layer, the equivalent parallel resistance, and capacitance of the leakage gap between the TiON layer and the residual conductive filament, respectively. These components show a strong dependence on the stop voltage, which can be explained in the framework of oxygen vacancy model and conductive filament concept. On the other hand, R is observed to decrease with dc bias, which can be attributed to the barrier lowering effect of the Coulombic trap well in the Poole–Frenkel emission model.
Published in: IEEE Transactions on Electron Devices ( Volume: 62, Issue: 8, August 2015)
Page(s): 2684 - 2688
Date of Publication: 07 July 2015

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I. Introduction

Resistive switching random access memory (RRAM) based on metal oxides, such as Al2O3, ZnO, NiOx, TiO2, and CuxO, is promising in the application of next-generation nonvolatile memory due to its simple structure, low-power consumption, high read/write speed, and good reliability [1]–[7]. Recently, multilevel resistance states in RRAM devices have been demonstrated to increase the storage density of the RRAM device [8], [9]. Until now, most of the studies were focused on the performance improvement and reliability of the multibit storage, there are relatively few studies on the mechanism for the multilevel resistance states of RRAM device. In this brief, impedance spectroscopy is employed to investigate multilevel high-resistance states in TiN/HfOx/Pt RRAM structure. Impedance spectroscopy is a powerful tool to examine the conduction properties of dielectric thin films, making it suitable for resistive switching property study [10], [11]. For the TiN/HfOx/Pt RRAM structure used in this brief, the multilevel high-resistance states may be attributed to the different rupture degrees of the conductive filament, which is hard to be detected by the microscopic techniques such as transmission electron microscopy and scanning probe microscopy. However, through the analysis of the impedance measurement, we have been able to obtain information about the redox reaction relating to the change of TiON interfacial layer and rupture of the conductive filament for different high-resistance states.

References

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