Vertical, capacitive microelectromechanical switches produced via direct writing of copper wires.

Zhiran Yi,Ping Cui,Jianjun Guo,Minfeng Yu,Shuai Zhang,Yining Chen,Gaojie Xu,Haiqing Zhang

doi:10.1038/micronano.2016.10

Abstract

Three-dimensional (3D) direct writing based on the meniscus-confined electrodeposition of copper metal wires was used in this study to develop vertical capacitive microelectromechanical switches. Vertical microelectromechanical switches reduce the form factor and increase the area density of such devices in integrated circuits. We studied the electromechanical characteristics of such vertical switches by exploring the dependence of switching voltage on various device structures, particularly with regard to the length, wire diameter, and the distance between the two wires. A simple model was found to match the experimental measurements made in this study. We found that the electrodeposited copper microwires exhibit a good elastic modulus close to that of bulk copper. By optimizing the 3D structure of the electrodes, a volatile electromechanical switch with a sub-5 V switching voltage was demonstrated in a vertical microscale switch with a gap distance as small as 100 nm created with a pair of copper wires with diameters of ~1 μm and heights of 25 μm. This study establishes an innovative approach to construct microelectromechanical systems with arbitrary 3D microwire structures for various applications, including the demonstrated volatile and nonvolatile microswitches.

Highlights

Microelectromechanical systems (MEMS) have been used in many applications in many industries, including the medical, automotive, optics, electronics, and biotechnology sectors[1,2]
We propose the use of a high-efficiency, directwriting technology that is based on the meniscus-confined electrodeposition principle[37] to fabricate vertical microelectromechanical switches
Copper microwires (Cu MWs) with diameters of ~ 1 μm and heights of 20 μm are grown using a micropipette with a diameter of ~ 1 μm filled with 0.1 M CuSO4 aqueous solution

Summary

Introduction

Microelectromechanical systems (MEMS) have been used in many applications in many industries, including the medical, automotive, optics, electronics, and biotechnology sectors[1,2]. MEMS switches operated by radio frequencies are essential components in the circuit architectures of a variety of MEMS-based systems[3]. MEMS switches are typically fabricated with silicon-surface micromachining technology and are typically planar, which requires a large surface budget on integrated circuit chips[5]. Submicron floating cantilevers fabricated with a metal layer (for example, Au, Al, Pt, and so on) are used as mechanical moving electrodes. To accommodate the further miniaturization and integration of devices and systems, there is a trend towards developing three-dimensional (3D) circuit architectures and related 3D devices, including novel 3D MEMS switches

Methods

Results

Conclusion