Investigation on the Stabilizing Effect of Titanium in HfO2-Based Resistive Switching Devices With Tungsten Electrode

Vittorio Fra,Yusuf Leblebici,Elmira Shahrabi,Carlo Ricciardi

doi:10.3389/fnano.2020.592684

Abstract

Resistive switching (RS) devices, also referred to as Resistive Random Access Memories (ReRAMs), rely on a working principle based on the change of electrical resistance following proper external electrical stimuli. Since the demonstration of the first resistive memory based on a binary transition metal oxide (TMO) enclosed in a Metal-Insulator-Metal (MIM) structure, this class of devices has been considered a key player for simple and low-cost memories. However, successful large-scale integration with standard CMOS technologies still needs systematic investigations. In this work, we examine the beneficial effect titanium has when employed as buffer layer between CMOS-compatible materials like hafnium dioxide and tungsten. Hindering the tungsten oxidation, Ti provides RS stabilization and allows to get faster responses from the devices. Through an extensive comparative study, the effect of both thickness and composition of Ti-based buffer layers is investigated. The reported results show how titanium can be effectively employed to stabilize and tailor the RS behaviour of the devices, and they may open the way to the definition of new design rules for ReRAM-CMOS integration. Moreover, the gradual switching and the response speed tunability observed employing titanium might also extend the domain of interest of these results to brain-inspired computing applications.

Highlights

Devices with tunable electrical resistance find application in information and communication technologies (ICTs) since the end of the 19th century, when the so-called coherer was employed as receiver in Marconi’s wireless telegraph (Marconi, 1899) thanks to the possibility of changing, and retaining, its electrical conductivity upon external stimuli
Platinum and titanium nitride have been shown to be suitable for inert electrodes (Tappertzhofen et al, 2014), while oxidizing metals like tungsten, titanium, hafnium, and tantalum have been studied as electrodes in valence change memory (VCM) devices (Chen et al, 2013; Lin et al, 2013; Shahrabi et al, 2019) and many oxides have been tested as an insulating layer
A 3D sketch of the device structure is reported in Figure 1A, while the field emission scanning electron microscope (FESEM) image in Figure 1B shows the actual geometry with a top view of a single resistive random access memories (ReRAMs) cell

Summary

Introduction

Devices with tunable electrical resistance find application in information and communication technologies (ICTs) since the end of the 19th century, when the so-called coherer was employed as receiver in Marconi’s wireless telegraph (Marconi, 1899) thanks to the possibility of changing, and retaining, its electrical conductivity upon external stimuli. In seeking to fulfill these requirements, many studies have been carried out on subjects ranging from the physical behavior to the hardware implementation As a result, it is well-established that both interface-type (Celano et al, 2017; Govoreanu et al, 2017) and filamentary-type (Joshua Yang et al, 2009; Lee et al, 2009; Celano et al, 2014) resistive switching exist, and it is widely accepted that the formation of a conductive filament involves ion motion within the insulating layer of the MIM structure (Valov, 2014; Sun et al, 2019; Wang et al, 2020). The motion of these species strongly depends on the oxygen exchange between the oxide film and the oxidizing electrode and can be described by the reaction: M bulk

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Conclusion