Understanding the Formation of Conducting Filaments in RRAM Through the Design of Experiments

Abstract

The resistive switching effect in TiO2-x memory devices is thoroughly investigated in order to obtain optimum memory performance, in terms of switching ratio, uniformity of the switching characteristics and multilevel capability. As a result, various fabrication procedures were followed with the aim to enhance the above properties. The main body of our devices was TiO2-x thin film, with constant thickness of 45 nm, while different approaches were implemented during the fabrication process, such as increasing the oxygen content during film growth, depositing top electrodes with different thicknesses, inserting a layer of nanocrystals (NCs) within the middle of the dielectric and using two various oxygen contents during film deposition in order to create a homobilayer structure. The common feature of these techniques is to control the regions where oxygen vacancy creation will take place in order to control the formation/rupture of the conducting filaments (CFs). Conductive-Atomic Force Microscopy (C-AFM) results support the localized nature of the switching effect. The gradual transition during the SET process, which allows precise CF control through proper external stimulus, as well as the self-rectification effect, which alleviates the sneakpath issue in crossbar architecture, are also important assets of our experimental approach.