Understanding the Resistive Switching Phenomena of Stacked Al/Al2O3/Al Thin Films from the Dynamics of Conductive Filaments

Joel Molina-Reyes,Luis Hernandez-Martinez

doi:10.1155/2017/8263904

Joel Molina-Reyes, Luis Hernandez-Martinez

Open Access

https://doi.org/10.1155/2017/8263904

Copy DOI

Abstract

We present the resistive switching characteristics of Metal-Insulator-Metal (MIM) devices based on amorphous Al2O3which is deposited by Atomic Layer Deposition (ALD). A maximum processing temperature for this memory device is 300°C, making it ideal for Back-End-of-Line (BEOL) processing. Although some variations in the forming, set, and reset voltages (VFORM,VSET, andVRESET) are obtained for many of the measured MIM devices (mainly due to roughness variations of the MIM interfaces as observed after atomic-force microscopy analysis), thememristoreffect has been obtained after cyclicI-Vmeasurements. These resistive transitions in the metal oxide occur for bothbipolarandunipolarconditions, while theIOFF/IONratio is around 4–6 orders of magnitude and is formed at gate voltages ofVg<4 V. In unipolar mode, a gradual reduction inVSETis observed and is related to combined (a) incomplete dissolution of conductive filaments (made of oxygen vacancies and metal ions) which leaves some residuals and (b) thickening of chemically reduced Al2O3during localized Joule heating. This is important because, by analyzing the macroscopic resistive switching behavior of this MIM structure, we could indirectly relate it to microscopic and/or nanoscopic phenomena responsible for the physical mechanism upon which most of these devices operate.

Highlights

Since the invention and experimental demonstration of the memristor, several materials in the form of thin dielectric films or solid electrolytes have been tested for these emergent nonvolatile memory devices in order to produce reliable and reversible switching cycles of the resistive state of the oxide
We present the resistive switching characteristics deposited by Atomic Layer Deposition (ALD)
Moderate capacitance in accumulation turns into a dielectric constant of k ∼ 6, a relatively low value compared to what is expected for bulk Al2O3 (k ∼ 9) and yet the good uniformity in the C-V data is again observed for all measured MIS devices

Summary

Introduction

Since the invention and experimental demonstration of the memristor (an integrated device with memory-resistance properties, able to correlate electric charge to magnetic flux q-φ [1]), several materials in the form of thin dielectric films or solid electrolytes have been tested for these emergent nonvolatile memory devices in order to produce reliable and reversible switching cycles of the resistive state of the oxide. Thin film based materials able to switch from a high resistance state (HRS/OFF) to a low resistance state (LRS/ON) and vice versa are responsible for the typical “pinched hysteresis loops,” which are observed during cyclic current-voltage (I-V) measurements of these devices This has contributed to the development of important applications like nonlinear circuits, chaotic systems, highly dense neural networks, and even neuromorphic computing, where the diffusive dynamics of memristors can be used as synaptic emulators. Several Metal-Insulator-Metal structures have shown the ability to switch between these two resistive states (HRS ↔ LRS) after promoting resistive switching phenomena (by forming/dissolving conductive filamentary paths in mostly binary oxides) or ion migration mechanisms (by cation or anion species in solid electrolytes) during high electrical stress of the devices [1, 2] In this sense, Resistive switching Random Access Memory (ReRAM) devices have attracted considerable attention in the recent years due to their superior characteristics for nonvolatile data storage.

Methods

Results

Conclusion