Integration of a Carbon Nanotube Network on a Microelectromechanical Switch for Ultralong Contact Lifetime

Abstract

Micro-/nanoelectromechanical (MEM/NEM) switches have been extensively studied to address the limitations of transistors, such as the increased standby power consumption and performance dependence on temperature and radiation. However, their lifetimes are limited owing to the degradation of the contact surfaces. Even though several materials and structural designs have been recently developed to improve the lifetime, the production of a microswitch that is compatible with a complementary metal-oxide semiconductor (CMOS) with a long lifetime remains a significant challenge. We demonstrate a vertically actuated MEM switch with extremely high reliability by integrating a carbon nanotube (CNT) network on a gold electrode as the contact material using a low-temperature, CMOS-compatible solution process. In addition to their outstanding mechanical and electrical properties of CNTs, their deformability dramatically increases the effective contact area of the switch, thus resulting in the extension of the lifetime. The CNT-coated MEM switch exhibits a lifetime that is more than 7 × 108 cycles when operated in hot-switching conditions, which is 1.9 × 104 times longer than that of a control device without CNTs. The switch also shows an excellent switching performance, including a low electrical resistance, high on/off ratio, and an extremely small off-state current.

Electrostatic pull-in application in flexible devices: A review

“…CNT-NEM switches have great potential in nonvolatile memory devices. In addition, CNTs used with metals in composite electrodes, as a bottom contact electrodes [ 25 – 26 ], or intermediate layer [ 27 ], and can greatly improve the life cycles of switches. However, CNTs prepared by CVD are randomly oriented, and positioning CNTs at the desired location is a challenge that hinders scalable manufacturing.…”

Geometrically Structured Nanomaterials for Nanosensors, NEMS, and Nanosieves

“…Although M/NEM switching devices have outstanding performance, such as quasi‐zero leakage current, low power consumption, high on/off characteristics, and the possibility of operation under harsh environmental conditions, such as high temperatures and external electrical and radiation exposure, they still suffer from unacceptably low reliability, hindering their use in practical applications and their further development. In general, failures of M/NEM switches can be classified into i) permanent stiction by contact material welding and melting during operation and ii) sudden electrical resistance increase due to wear and fracture at the contacting interfaces 14,224–227,229,231,249,265,266. To alleviate these failure issues and demonstrate long‐term reliability in M/NEM switches, various methods based on material, structural, and circuit approaches have been actively developed.…”

“…However, use of carbon nanomaterials in the contacts of M/NEM switches has been difficult to realize. To synthesize high‐quality carbon nanomaterials at contacting points of micro/nanodevices, high temperature and precise location control are essential, both of which are very difficult to achieve in M/NEM switches with conventional fabrication processes 14,249,265. Recent advances in design and fabrication of M/NEM devices, however, have enabled us to develop mechanical switching devices using geometrically structured carbon nanomaterials; resulting materials have shown great improvement in long‐term stability.…”

“…f) CNT networked nanostructure generates numerous contact spots, resulting in lower contact resistance by generating elastic deformation as drain approaches bottom source electrode. e,f) Reproduced with permission 265. Copyright 2019, American Chemical Society.…”

“…At 430 K, a constant source–drain current of 1 mA was conducted through the contact for up to 1.1 × 10 6 hot‐switching operations, and no noticeable degradation of the contact characteristics was observed. More recently, Jo et al demonstrated CNT network‐integrated MEM switches with high reliability 265. Instead of aligned CNT arrays at the contact interface of the MEM switch, they utilized 3D networked CNT arrays for the contact material (Figure 6e).…”