Formation and Rupture of Nanofilaments in Metal/TaOx/Metal Resistive Switches

Abstract

There is an increased interest in the Conductive Bridge Random Access Memory (CBRAM) and Resistive Random Access Memory (RRAM) because of their excellent scaling potential, low power consumption, high switching speed, good retention and endurance properties. Although, various mechanisms have been proposed to explain the switching behavior in CBRAM devices, i.e. metal ion migration and subsequent formation and rupture of conductive filament, formation of conductive path via oxygen ion transport etc, there are still many aspects of these mechanisms that are little understood or are being disputed. This work probes the details of the switching mechanisms on a new level and asks questions like:

1) How is the formation of nanofilament affected by various degrees of Cu diffusion stopping power of the inert electrode? To answer this question, resistive switches with very thin Cu layers covering the Pt electrode were fabricated and analyzed.

2) How does a limited source of active ions impact the formation and rupture of nanofilaments? To answer this question, new samples with limited Cu supply were fabricated and analyzed.

3) What is the mechanism of nanofilament formation in Pt/TaOx/Pt resistive switches where the active copper electrode is removed and replaced by inert Pt electrode.

4) What are the most suitable conditions (material structure of the device and operation conditions) to set and reset multi nanofilaments?

This work summarizes the current status of analysis of the data obtained while attempting to explain interesting phenomena like volatile switching and multiple filament formation experienced by modifying the switch structures.