Yenhao Chen

Characterization of Contact Resistance Stability in MEM Relays With Tungsten Electrodes

The impact of device operating parameters on the ON-state resistance (RON) of microelectromechanical relays with tungsten (W) electrodes is reported. Due to the susceptibility of W to oxidation, RON increases undesirably over the device operating cycles. This issue is aggravated by Joule heating when the relay is in the on state. The experimental results confirm that shorter ON time, as well as shorter off time, provides for more stable RON with respect to the number of ON/OFF switching cycles.

A new switching device for printed electronics: inkjet-printed microelectromechanical relay.

Printed electronics employing solution-processed materials is considered to be the key to realizing low-cost large-area electronic systems, but the performance of printed transistors is generally inadequate for most of the intended applications due to limited performance of printable semiconductor materials. We propose an alternative approach for a printed switch, where the use of semiconductors can be avoided by building mechanical switches with printed metal nanoparticle-based inks. In this work, we detail the first demonstration of inkjet-printed microelectromechanical (MEM) switches with abrupt switching characteristics, very low on-state resistance (~10 Ω), and very low off-state leakage. The devices are fabricated using a novel process scheme to build three-dimensional cantilever structures from solution-processed metallic nanoparticles and sacrificial polymer layers. These printed MEM switches thus represent a uniquely attractive path for realizing printed electronics.

Hybrid CMOS/BEOL-NEMS technology for ultra-low-power IC applications

Three-dimensional (3-D) nano-electro-mechanical (NEM) switches (relays) are proposed to reduce the die area and power consumption of digital logic and memory circuits.

Multiple-Input Relay Design for More Compact Implementation of Digital Logic Circuits

Multiple-input relays are proposed to enable more compact implementation of digital logic circuits, and the first functional prototypes are presented. A relay with three equally sized input electrodes is demonstrated to perform various three-input logic functions, with a delay that can be well predicted by a lumped-parameter model. Relays with differently sized input electrodes can be used to perform more complex functions. A flash-type analog-to-digital converter is presented as one example.

Recent progress and challenges for relay logic switch technology

The energy efficiency of CMOS technology is fundamentally limited by transistor off-state leakage (IOFF). Mechanical switches have zero IOFF and therefore could be advantageous for ultra-low-power digital logic applications. This paper discusses recent advancements in relay logic switch technology and current challenges which must be addressed to realize its promise.

Multi-input/multi-output relay design for more compact and versatile implementation of digital logic with zero leakage

Multi-functional digital logic circuits, each utilizing only two relays, are demonstrated for the first time. This work can be extended to relay designs comprising greater than two input electrodes and/or greater than two sets of source/drain electrodes, for more compact realization of zero-leakage digital ICs in the future.

Reliable micro-electro-mechanical (MEM) switch design for ultra-low-power logic

Fundamental energy-efficiency limits for transistor-based digital logic circuits have led to renewed interest in micro-electro-mechanical (MEM) switches [1-12] because they have the ideal characteristics of zero off-state leakage and abrupt switching behavior. Reliable operation with high endurance is a key requirement for digital logic applications, and historically has been a challenge for mechanical computing devices. This paper discusses various failure modes for MEM switches, with particular focus on contact stiction due to welding. Experimental results show that device endurance (number of on/off switching cycles before welding-induced failure) improves exponentially with decreasing contact temperature, and that it depends on the contact material, contact voltage (VC), on-state resistance (RON) and load capacitance. A contact reliability model calibrated to the experimental data projects that endurance will exceed 1015 cycles at 1V operating voltage. Implications for switch contact design, logic applications and dimension scaling are discussed.

Reliability of MEM relays for zero leakage logic

Micro-electro-mechanical (MEM) relays are an intriguing alternative to transistors for ultra-low-power digital logic applications [1]. This paper investigates various failure modes for logic relays. Experimental results are presented to show that structural fatigue, dielectric charging, and contact stiction are not reliability-limiting issues. Contact resistance instability caused by surface oxidation and contamination is the primary challenge, and can be influenced by device design and operating conditions.

Effect of Body Biasing on the Energy-Delay Performance of Logic Relays

The effect of the body bias voltage on logic relay performance is investigated. The switching hysteresis voltage, which sets a lower limit for the relay operating voltage, is experimentally found to decrease with increasing body bias voltage, due to reduced surface adhesive force. It is demonstrated that the switching energy of a relay can be reduced by body biasing, at a tradeoff of increased mechanical turn-ON delay. Simulations of nanoscale relay designs indicate that body biasing can be used to mitigate relay manufacturing challenges, while enabling ultralow-voltage (sub-100 mV) operation with relatively fast switching speed.

Inkjet-printed micro-electro-mechanical switches

An inkjet-printed micro-electro-mechanical switch technology is demonstrated to provide for zero off-state leakage, low on-state resistance (∼10 Ω), and moderate switching delay (∼10 µs), indicating promise for application to future large-area displays.