ISBN 978-3-8439-0964-8

978-3-8439-0964-8, Reihe Elektrotechnik

Stephan Menzel
Modeling and Simulation of Resistive Switching Devices

156 Seiten, Dissertation Rheinisch-Westfälische Technische Hochschule Aachen (2012), Softcover, B5

Zusammenfassung / Abstract

As conventional memory concepts are approaching their physical scaling limits, novel memory device concepts for highly scalable, ultrafast, energy efficient, nonvolatile memory are demanded. Resistive switching devices, which rely on nanoionic redox phenomena, are potential candidates for the use in resistive random access memories (ReRAMs) or logic applications. By applying appropriate electrical stimuli they can be switched back and forth between different resistance states, which encode the digital information. Based on their physical nature three different resistive switching mechanisms can be distinguished: the electrochemical mechanism (ECM), the valence-change mechanism (VCM) and the thermochemical mechanism (TCM). While the basic principles of the switching processes are well understood, many details are still unknown or under discussion. Especially, the origin of the switching kinetics in VCM cells and the physical origin of the multilevel programming capability in ECM cells need to be clarified. To address these open questions simulation models can be employed. However, until now there are no simulation models available that can answer these questions.

In this thesis, physics-based simulation models of ECM and VCM devices are developed to address these questions. For this, the corresponding simulation results are compared to experimental data.

A physics-based dynamic 1D compact model for resistive switching in ECM cells is presented. Simulations based on this model were performed to investigate fundamental phenomena as the multilevel switching capabilities and the nonlinear switching kinetics. The former is realized by modulation of a tunneling gap between one electrode and a growing filament within the insulating layer. By comparison to experimental data, this model was validated. This model is extended to a 2D finite elements simulation model. With this approach polyfilamentary growth and the unipolar switching phenomenon in ECM cells at very low resistances were investigated and discussed.

Regarding the VCM cell, an electro-thermal finite elements simulation model was developed to explain the origin of the nonlinear switching kinetics. A comparison of the model and the experimental data revealed that the nonlinear switching kinetics is predominantly caused by temperature-accelerated drift of oxygen vacancies. The derived model provides essential rules for an optimized cell design.