Microelectromechanical Relay Research Articles

Interfacial adhesion between electrical contacts determined by surface quality

ABSTRACT Micro-Electromechanical-Relay (MER) has widely achieved application in the field of engineering thanks to the excellent features and ever-growing interest in microelectronic products. However, the adhesion phenomenon between gold-sputtered contact pairs in MER usually brings about operating failure of normally closed contacts limiting the reliability level of MER. In this paper, various contact combinations between electrical contact pairs are assembled to simulate real contact conditions, and associated failure type is built by taking advantage of mechanical adhesion theory to reveal failure mechanism about cold adhesion. It is found that the adhesion force is correlated closely with the surface roughness of contact pairs. The specific contact combination is a significant effective strategy to reduce the adhesion failure between electrical contacts.

Investigation of Electrical and Mechanical Reliability of Inkjet-Printed 4-Terminal Microelectromechanical Relays

We investigate the mechanical and electrical reliability of inkjet-printed 4-terminal (4T) microelectromechanical (MEM) relays in various failure modes. Since an inkjet-printed mechanical relay exhibits an extremely low on-resistance (~4 Ω), the endurance of MEM relays can be limited dominantly by Joule heating from the high current density at the contacting asperities, which eventually leads to welding-induced and electromigration failures. Therefore, high drain-source voltage can reduce the mean number of cycles to failure (MCTF). In addition, the endurance also depends on the structural fatigue of the floated beams, where the mechanical strain is concentrated near the junction area of the two floated beams. Thermal and mechanical stress distributions of the suggested printed 4T MEM relay are analyzed by 3-dimensional affected significantly by charging of the dielectric or oxidation of the contacting surface which can degrade a pull-in voltage and on-current, respectively.

A Normalized Model of a Microelectromechanical Relay Calibrated by Laser-Doppler Vibrometry.

This work presents a behavioral model for a microelectromechanical (MEM) relay for use in circuit simulation. Models require calibration, and other published relay models require over a dozen parameters for calibration, many of which are difficult to extract or are only available after finite element analysis. This model improves on prior work by taking advantage of model normalization, which often results in models that require fewer parameters than un-normalized models. This model only needs three parameters extracted from experiment and one dimension known from device fabrication to represent its non-contact behavior, and two additional extracted parameters to represent its behavior when in contact. The extracted parameters–quality factor, resonant frequency, and the pull-in voltage–can be found using laser Doppler vibrometry. The device dimension is the actuation gap size, which comes from process data. To demonstrate this extraction process, a series of velocity step responses were excited in MEM relays, the measured velocity responses were used to calibrate the model, and then then simulations of the model (implemented in Verilog-A) were compared against the measured data. The error in the simulated oscillation frequency and peak velocity, two values selected as figures of merit, is less than 10% across many operating voltages.

Breakdown and Healing of Tungsten-Oxide Films on Microelectromechanical Relay Contacts

This work discusses the electrical break down of tungsten oxide films that form on contacting surfaces of tungsten electrodes in micro-electro-mechanical (MEM) relays. Electrical tests were applied to the contacts of 27 devices to measure the voltage, current and charge required to break down the oxide films, and also to measure the change in current through the contacts as the film healed. The oxide breaks down when an average of 58 <inline-formula> <tex-math notation="LaTeX">$\mu \text{C}$ </tex-math></inline-formula> of electronic charge passes through the oxide, which usually requires applying 1&#x2013;2 V to drive 100 nA-<inline-formula> <tex-math notation="LaTeX">$10~\mu \text{A}$ </tex-math></inline-formula> of current through the contact. The tungsten oxide heals quickly in laboratory ambient conditions: applying 0.5 V to a contact immediately after breaking down an oxide results in a contact current greater than <inline-formula> <tex-math notation="LaTeX">$5~\mu \text{A}$ </tex-math></inline-formula>, but the same test only induces 1 nA of current 1&#x2013;5 minutes later. The reduction in contact current with time follows a power law, which is characteristic of charge relaxation in oxides. Additionally, Holm&#x2019;s experiment shows that current conduction through the contacts is dominated by tunneling through an oxide. These facts together suggest that the break down and healing are electrical processes related to trap accumulation and relaxation in the tungsten oxide. [2021-0161]

Study of MEM Relay Contact Design and Body-Bias Effects on on-State Resistance Stability

Body-biased micro-electro-mechanical (MEM) relays previously have been demonstrated to be a promising alternative to transistors for ultra-low voltage digital logic applications. A basic requirement for reliable relay-based circuit operation is suitably low and stable relay ON-state resistance (RON). In this work, the effect of body biasing on RON is investigated for relays of different contact designs. It is found that a single direct contact design not only provides for the smallest hysteresis voltage but also the smallest RON, making it the most suitable for low voltage applications. Body-biased operation is found to degrade RON stability over many ON/OFF switching cycles, however, due to a reduction in contact velocity.

Understanding of the Static Contact Behaviors of Rod and Spring for Microelectromechanical Relay

The structure configuration of rod and spring contacts is widely used in the microelectromechanical relay. Low and stable electrical contact resistance is a fundamental requirement for reliability and electrical life of relays. In this paper, a theoretical model of rod and spring is presented to calculate the constriction resistance and compared with the classical Holm's models. Furthermore, the relationship between electrical contact resistance and contact force of rod and spring is investigated explicitly with our designed test rig. A power law for contact resistance versus contact force R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = KF <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-m</sup> is established. A schematic model of contact pair with a rough surface is introduced to explain the variation of contact resistance during the loading process. In particular, the transition phenomena from the initial single contact asperity to the whole rectangular contact area are analyzed. Finally, the effects of surface roughness of the Au coating and operating cycles on the static contact behavior are also discussed.

A High-Speed Inkjet-Printed Microelectromechanical Relay With a Mechanically Enhanced Double-Clamped Channel-Beam

We report a high-speed inkjet-printed three-terminal microelectromechanical (MEM) relay with a double-clamped beam that exploits the enhanced stiffness of the double-clamped structure to improve electrical performance. To minimize mechanical delay and pull-in voltage, the contact gap between the channel-beam and drain, and the stiffness of the beam and shape of the drain was carefully designed and optimized through a 3-D finite element simulation. The double-clamped beam prevents stiction-related failure between the channel-beam and drain despite the contact gap being only 370 nm for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt; 500~\mu \text{m}$ </tex-math></inline-formula> long beam. The resulting printed relay delivers a turn-ON delay of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8~\mu \text{s}$ </tex-math></inline-formula> at a gate voltage of 10 V, a pull-in voltage of only 7.2 V, immeasurable off-leakage, excellent subthreshold swing, and a small hysteresis window of 2 V without any bending or collapsing of the beam. The device also shows reliable operation over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{5}$ </tex-math></inline-formula> cycles while maintaining a high ON/OFF ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{8}$ </tex-math></inline-formula> , and extremely low ON-state resistance of 3.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> . [2016-0180]

High-performance inkjet-printed four-terminal microelectromechanical relays and inverters.

We report the first demonstration of inkjet-printed 4-terminal microelectromechanical (MEM) relays and inverters with hyper-abrupt switching that exhibit excellent electrical and mechanical characteristics. This first implementation of a printed 4-terminal device is critically important, since it allows for the realization of full complementary logic functions. The floated fourth terminal (body electrode), which allows the gate switching voltage to be adjusted, is bonded to movable channel beams via a printed epoxy layer in a planar structure, which can move downward together via the electrostatic force between the gate electrodes and body such that the channel can also actuate downward and touch the drain electrode. Because the body, channel, and drain electrodes are completely electrically separated, no detectable leakage or electrical interference between the electrodes is observed. The printed MEM relay exhibited an on-state resistance of only 3.48 Ω, immeasurable off-state leakage, subthreshold swing <1 mV/dec, and a stable operation over 10(4) cycles with a switching delay of 47 μs, and the relay inverter exhibits abrupt transitions between on/off states. The operation of the printed 4-terminal MEM relay was also verified against the results of a 3-dimensional (3D) finite element simulation.

Exploitation of the coffee-ring effect to realize mechanically enhanced inkjet-printed microelectromechanical relays with U-bar-shaped cantilevers

We report a mechanically enhanced inkjet-printed microelectromechanical (MEM) relay with a U-bar-shaped cantilever by exploiting the coffee-ring effect. The printed cantilever shape, especially the effective thickness caused by the elevated walls, can be controlled during the drying process by outward convective flow of silver nanoparticles. This enhances mechanical stiffness to efficiently produce a strongly suspended cantilever that is immune to collapse- and curling-related failures. This approach to enhancing cantilever stiffness is unique to printing-based processes using metal-nanoparticle inks and is not feasible for conventional photolithography processes. The resulting printed MEM relays show a pull-in voltage of only 6.6 V and an on/off ratio of 108 with extremely low on-state resistance (∼14.3 Ω) and off-state leakage that is comparable to those of conventional silicon-based MEM relays.

Microelectromechanical Relay and Logic Circuit Design for Zero Crowbar Current

Microelectromechanical Relay and Logic Circuit Design for Zero Crowbar Current

Demonstration of Integrated Micro-Electro-Mechanical Relay Circuits for VLSI Applications

This work presents measured results from test chips containing circuits implemented with micro-electro-mechanical (MEM) relays. The relay circuits designed on these test chips illustrate a range of important functions necessary for the implementation of integrated VLSI systems and lend insight into circuit design techniques optimized for the physical properties of these devices. To explore these techniques a hybrid electro-mechanical model of the relays' electrical and mechanical characteristics has been developed, correlated to measurements, and then also applied to predict MEM relay performance if the technology were scaled to a 90 nm technology node. A theoretical, scaled, 32-bit MEM relay-based adder, with a single-bit functionality demonstrated by the measured circuits, is found to offer a factor of ten energy efficiency gain over an optimized CMOS adder for sub-20 MOPS throughputs at a moderate increase in area.

MEM relay for reconfigurable RF circuits

We describe a microelectromechanical (MEM) relay technology for high-performance reconfigurable RF circuits. This microrelay, fabricated using surface micromachining, is a metal contact relay with electrical isolation between signal and drive lines. This relay provides excellent switching performance over a broad frequency band (insertion loss of 0.1 dB and isolation of 30 dB at 40 GHz), versatility in switch circuit configurations (microstrip and coplanar, shunt and series), and the capability for monolithic integration with high-frequency electronics. In addition, this MEM relay technology has demonstrated yields and lifetimes that are promising for RF circuit implementation.