Scanning probe microscopy as a scalpel to probe filament formation in conductive bridging memory devices

One promising technology under consideration for future non-volatile memory is conductive bridging random access memory (CBRAM). These devices rely on a reversible change in resistance of a dielectric layer sandwiched between two metal electrodes. To unravel the underlying processes, we present in this work an innovative technique to observe conductive filament in CBRAM devices programmed under real operative conditions. We show the different properties of the conductive filament for the respective on/off resistive states. We demonstrate a novel usage of scanning probe microscopy whereby the tip is used to remove (de-process) the top electrode of the CBRAM device while subsequently we use conductive atomic force microscopy (C-AFM) to characterize the dielectric layer of fresh, set and reset devices. The devices are first programmed under their normal operational conditions, secondly exposed to the layer removal procedure and finally analyzed using C-AFM. Our results indicate that the on/off state of the devices can be linked to the presence or not of an highly conductive filament. (C) 2013 Elsevier B.V. All rights reserved.