Microelectromechanical System Relays Research Articles

Utilizing mechanical adhesion force as a high contact force in a MEMS relay

High contact force in a microelectromechanical systems (MEMS) relay is known to be the most important factor in achieving low contact resistance. Achieving a high contact force in an electrostatically-actuated MEMS relay usually requires high actuation voltage to exert a high electrostatic force. In this paper, for the first time, we demonstrate the successful use of a mechanical adhesion force as a high contact force for realizing an extremely low contact resistance, even at a low actuation voltage of 3.8 V. To maximize the mechanical adhesion, we designed a suitably-large contact area (100 μm × 100 μm) in the MEMS relay and a detachment spring structure to separate the two electrodes that were in contact with one another by only the mechanical adhesion force, thereby enabling the MEMS switch to perform multiple switching operations. The proposed MEMS relay exhibited an extremely low contact resistance of 4.9 mΩ with only the mechanical adhesion force after we applied an actuation voltage of 3.8 V, and it achieved a retention time of 105 s because of stable mechanical contact. Through this experiment, we verified that the mechanical adhesion force can provide an efficient source for generating high contact force in the MEMS relay.

4 W Power MEMS Relay With Extremely Low Contact Resistance: Theoretical Analysis, Design and Demonstration

This paper reports on the unprecedented 4 W power microelectromechanical systems (MEMS) relay with a contact- force-maximizing structure in a dual-contact material system. A MEMS relay with dual (hard and soft) contact materials is known to have high durability in hot-switching conditions, and the contact force is also considered to be the most important factor that contributes to an efficient reduction of the contact resistance. We devised a contact-force-maximizing structure with a plate-type suspended structure and in-plate springs and applied it to a dual-contact material system to achieve extremely low contact resistance. The fabricated MEMS relay successfully operated sequential switching between the dual contact materials in the contact-force-maximizing structure and thereby showed an extremely low contact resistance of 1.65 $\text{m}\Omega $ with a switching time of $7 {\mu \text {s}}$ at an operating voltage of 80 V. Thanks to the contact-force-maximizing structure with the dual-contact material system, the fabricated MEMS relay achieved a lifetime of up to $1.3\times 10^{\mathbf {3}}$ cycles in the hot-switching conditions of 4 W (10 V/400 mA) in an air atmosphere with a negligible variation of the contact resistance. This power level is the highest reported to date. [2020-0223]

Design and Fabrication of a Novel MEMS Relay with Low Actuation Voltage.

Compared with conventional solid-state relays, micro-electro mechanical system (MEMS) relays have the advantages of high isolation, low contact resistance, low power consumption, and abrupt switching characteristics. Nevertheless, the widespread application of MEMS relays has been limited due to the issue of the conflict between low actuation voltages and high device performance. This article presents a novel cantilever MEMS relay with an embedded contact electrode which helps to achieve a low actuation voltage (below 8 V) and high restoring force simultaneously. Meanwhile, the contact resistance is as low as around 0.4 Ω and the reliability is verified. To thoroughly investigate and analyze the novel cantilever MEMS relay, a static theoretical model of the structure was developed. Based on the model, the cantilever MEMS relay was designed and optimized. Then, the relays were fabricated by the bulk-silicon micromachining process based on the silicon–glass anodic bonding technology. Finally, the switching performance of the novel cantilever MEMS relay was measured. Experimental results demonstrate that the proposed MEMS relay has a low actuation voltage below 8 V and high performance, which is in good agreement with the simulation results, and shows significant advantages when compared with previous reports. Therefore, the proposed MEMS relay with an embedded contact electrode is promising in practical applications.

A Low Contact Resistance 4-Terminal Mems Relay: Theoretical Analysis, Design, and Demonstration

A 4-terminal microelectromechanical systems (MEMS) relay has long been sought for signal switching applications because it allows de-coupling of the actuation (body and gate) and signal (source and drain) components unlike a 3-terminal MEMS relay. However, the contact resistance still remains a serious problem in current 4-terminal MEMS relays compared with the 3-terminal MEMS relays. In this paper, using theoretical analysis, we first determined that the two-contact design, which was the most common design in the 4-terminal MEMS relay, was the origin of the high contact resistance. We subsequently developed a 4-terminal MEMS relay with a novel single-contact design. The fabricated 4-terminal MEMS relay with the single-contact design exhibited a contact resistance of 18 $\text{m}\Omega $ . To the best of our knowledge, this result is the lowest value among 4-terminal MEMS relays. In addition, we demonstrated that the two-contacts are the origin of the high contact resistance using measurement. The relay operated up to $1.1\times 10^{6}$ cycles at 1 V / 50 mA in air and hot switching conditions. Finally, the proposed 4-terminal MEMS relay was hermetically packaged for use in commercial applications. [2017-0183]

Analysis and Measurement of Residual Stress in Bridge Membrane MEMS Relays

Microelectromechanical system (MEMS) relays are gradually replacing traditional relays because they are smaller and lighter and consume less power. However, performance parameters of MEMS relays, such as the pull-down voltage, response time, and resonant frequency, often deviate from those originally designed, due to residual stress generated during the fabrication process. We present herein a method to measure this residual stress, based on a metal bridge membrane MEMS relay, with the help of a nanoindenter and the finite-element method (FEM). The testing result lies in a reasonable range, indicating that this simple method is reliable and helpful for MEMS relay optimization.

A push-pull double-contact MEMS relay fabricated by MetalMUMPs process

This document presents a push-pull double-contact MEMS (Micro ElectroMechanical System) relay. The MEMS relay is electrostatic driven and laterally actuating. Two push-pull structures form two parallel contacts for the proposed MEMS relay, which can make the contact resistance of the MEMS relay be smaller. The push and pull actions of the push-pull actuators can be accomplished simultaneously using only one action signal. In addition, high inductance DC bias line and substrate removal are used for additional electrical and/or thermal isolation. The fabrication of the proposed switch is based on the standard MetalMUMPs process. The measured pull-in voltage is 116 V and the switch-ON delay is 44 μs. Contact resistance of the MEMS relay is less than 1 Ω when the stress voltage exceeds 120 V.

A Highly Reliable MEMS Relay With Two-Step Spring System and Heat Sink Insulator for High-Power Switching Applications

This paper reports a highly reliable electrostatic microelectromechanical systems (MEMS) relay for high-power switching applications. The main proposal to elevate reliability is to reduce thermal damage in the contact area. Since a contact resistance is the key parameter determining the amount of Joule-heating and the corresponding thermal damage, we devised a unique spring structure to maximize the contact force (resulting in a low contact resistance) using a reasonable actuation voltage named a two-step spring system. Another important feature was applied to alleviate Joule-heating, which is to use an insulator having high thermal conductivity to dissipate the generated heat efficiently, named a heat sink insulator. The fabricated MEMS relay exhibited 2 mΩ in contact resistance, which is the lowest level reported so far with an actuation voltage of 45 V. Reliability was remarkably enhanced over ten times by the heat sink insulator. Consequently, by applying these two approaches simultaneously, the fabricated MEMS relay was successfully operated up to the 5.3 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cycles at 1 V/200 mA in ambient air and hot switching condition, which is the highest reliability reported at that power level.

A Highly Reliable Two-Axis MEMS Relay Demonstrating a Novel Contact Refresh Method

This paper reports on a two-axis actuated microelectromechanical systems (MEMS) relay to realize a unique contact-refresh concept. In comparison with all other conventional MEMS relays utilizing only several designated contact spots during their whole lifetime, the proposed concept can change the real contact spots (asperities) by altering the lateral position of contact asperities, thus providing highly reliable contact endurance. In addition, it can enhance lifetime of the switches that fail by contact resistance increase, and potentially even for switches that fail by contact stiction if the contact position is changed before a critical number of switching cycles is reached; however, the device inevitably has a relatively large device area and additional control circuitry in this stage of development. The fabricated relays showed vertical actuation voltages under 40 V, a switching delay of 190 $\mu \text{s}$ , and a maximum lateral displacement of 10 $\mu \text{m}$ . Owing to the suggested contact-refresh scheme, the total contact endurance in one switching device was dramatically increased, and the sum of dozens of lifetimes measured at the selected lateral positions reached $6 \times 10^{7}$ cycles at 100 mA in hot switching conditions (Au-to-Au contact), which is nearly 50 times higher than the average value of the measured lifetimes in a designated contact spot. [2014-0225]

Electrostatically actuated MEMS relay arrays for high-power applications

Micro-electromechanical systems (MEMS) relays should have high current-carrying capability and high device reliability for high-power applications. The current-carrying capability of MEMS relays is mainly limited by the thickness of metal contacts fabricated by micromachining process. Another significant limiting factor is the high contact resistance resulted from the low driving force, which is provided by microactuators. This paper presents a matrix configuration of electrostatically actuated microcantilever relay arrays that are connected in parallel to shunt high currents to individual relay elements. This method allows the matrix to be configured for different power requirements. The proposed novel hollow suspended spring lowers the driving voltage and enhances the device stability considerably because of its low longitudinal stiffness while high lateral stiffness. The average of pull-in voltages is approximately 39.4 V and the overdamped switching-on time is approximately 180 μs when 42 V of driving voltage is applied. Contact resistance of each relay is less than 1 Ω, and the equivalent contact resistance of the 2 × 2 relay arrays is lower than 250 mΩ. Each relay can operate in over 6.5 × 103 hot-switching cycles without failing at a current of 20 mA with 0.3 μm thick Au contacts, thus the 2 × 2 relay arrays can carry four times currents more than one single relay. Therefore, the proposed MEMS relay arrays are suitable for applications in high-power switching systems that require high reliability and stability, such as space applications.

Integrated Magnetic MEMS Relays: Status of the Technology

The development and application of magnetic technologies employing microfabricated magnetic structures for the production of switching components has generated enormous interest in the scientific and industrial communities over the last decade. Magnetic actuation offers many benefits when compared to other schemes for microelectromechanical systems (MEMS), including the generation of forces that have higher magnitude and longer range. Magnetic actuation can be achieved using different excitation sources, which create challenges related to the integration with other technologies, such as CMOS (Complementary Metal Oxide Semiconductor), and the requirement to reduce power consumption. Novel designs and technologies are therefore sought to enable the use of magnetic switching architectures in integrated MEMS devices, without incurring excessive energy consumption. This article reviews the status of magnetic MEMS technology and presents devices recently developed by various research groups, with key focuses on integrability and effective power management, in addition to the ability to integrate the technology with other microelectronic fabrication processes.

An Electrostatically Actuated Stacked-Electrode MEMS Relay With a Levering and Torsional Spring for Power Applications

This paper reports on a novel electrostatically actuated microelectromechanical systems (MEMS) relay for use in power-switching applications. It features a levering and torsional spring to enhance the stand-off voltage and contact endurance by means of an active-opening scheme. The proposed relay is based on a unique stacked-electrode structure and a soft insulating layer under the contact material that make it possible to obtain extremely low contact resistance, resulting in high current driving capability and reliable contact endurance. The fabricated relay demonstrated actuation voltages under 40 V, a switching time of 230 μs, and a maximum stand-off voltage of 360 V, which is the highest level among electrostatically actuated MEMS relays reported to date. The contact resistance was under 5 mΩ at 40 V of applied voltage, and more than 1 A could be carried. The contact reliability in a hot-switching condition was investigated for various dc current levels. At a current of 10 mA, the relay operated for more than 107 cycles before the test was stopped. In addition, the permanent contact stiction during switching operation at a 200-mA current level was overcome with a pull-off (active-opening) voltage of 90 V by the levering and torsional spring. Using this healing process, a device that failed at about 104 switching cycles in the 200-mA hot-switching mode was revived and reoperated with negligible contact resistance variation, lasting up to 4.9 ×105 cycles, constituting an order-of-magnitude enhancement in the lifetime even after failure.

An Extremely Low Contact-Resistance MEMS Relay Using Meshed Drain Structure and Soft Insulating Layer

This paper presents an electrostatically actuated microelectromechanical systems (MEMS) relay with a stacked-electrode structure having meshed drain electrode and a soft dielectric layer under the contact material to achieve high contact force and low hardness simultaneously, with the aim of providing ultralow contact resistance. In particular, a novel method for laying benzocyclobutene polymer under the contact layer to enlarge the contact area by reducing the effective hardness is proposed and theoretically analyzed. This could reduce the contact resistance by more than half in the case of an Au-Au contact. The fabricated devices have pull-in voltage of 32-43 V, switching time of 25 μs, and current driving capability of 350 mA in a hot-switching condition. Furthermore, the achieved minimum contact resistance is as low as 4 mΩ, which, to our knowledge, is the lowest value reported to date. In addition, negligible variation of contact resistance was observed during 1.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> hot-switching cycles in a 100-mA current level. The fabricated MEMS relay in the relatively low current of 1 mA was able to operate for more than 100 million cycles without failure before the test was stopped.

Lyapunov-Based Stabilization of MEMS Relays

In this paper, nonlinear stabilizers are introduced for voltage-controlled microelectromechanical system (MEMS) relays. The control constructions follow a Lyapunov approach and are based on a nonlinear dynamic model applicable to the two types of MEMS relays—electrostatic and electromagnetic. Two control schemes are presented with the objectives of avoiding pull-in during the microrelay closing and improving the transient response during the microrelay opening. First, an adaptive state feedback stabilizer is proposed to compensate for parametric uncertainty in all mechanical parameters and selected electrical parameters while ensuring asymptotic regulation of the electrode opening and closing. Next, a model-based observer/stabilizer is proposed to account for the lack of velocity measurements. Simulations demonstrate the performance of the two control schemes in comparison to the typical open-loop operation of the MEMS relay.

Significance of Surface Topography on Performance and Lifetime of MEMS Switches and Relays

AbstractSwitches and relays that have emerged from the microelectromechanical systems (MEMS) technology have the potential to replace traditional solid-state devices due to broader operating temperature range, higher breakdown voltage, and much higher off-state resistance. Interest in MEMS switches and relays has surged recently, principally due to the demonstrated performance in switching radio-frequency signals. However, understanding of the effect of the surface topography on performance and lifetime of these microdevices is rather empirical. Therefore, the objective of this study was to explore the role of surface topography in various physical phenomena encountered at contact interfaces of MEMS switches and relays. Emphasis is given on the dependence of pull-in voltage, electric field, and electrical breakdown on surface topography and interpretation of contact interface phenomena associated with surface erosion and adhesion in the context of surface topography effects. In addition, current obstacles in the study of the influence of the surface topography on the performance of MEMS switches and relays are discussed in light of recent findings.

MEMS and Nanotechnology

MEMS (Micro Electro Mechanical Systems) enables the fabrication of value-added system devices on silicon chips. Micromachining that is an extended integrated circuit technology is used for the fabrication. A rotational gyroscope with an electrostatically levitated ring rotor was developed for inertia sensing. Wafer level packaging enabled MEMS relay for LSI tester. Multi-probe data storage and multicolumn electron beam lithography are realized by array MEMS which take advantages of photolithography and nanostructures such as carbon nanotubes formed in them. Microprobes and microresonators provide high sensitivity and spatial resolution by utilizing nanostructures.

A single asperity study of Au/Au electrical contacts

Interfacial force microscopy (IFM) is used to measure the electrical contact properties of electroplated gold thin films of the type used in microelectromechanical system relays. Force and current levels consistent with those present in metal-metal contact switches are examined in an atmospheric-pressure, dry-nitrogen ambient at room temperature, and the nature of a nonmetallic contamination layer which limits contact resistance and lifetime is explicitly examined mechanically, electrically and chemically. The electrical and mechanical properties of the contamination layer on the gold substrate are observed by IFM both before and after being exposed to ozone for an extended period of time. The contamination film is characterized by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, and found to consist mostly of hydrocarbons; the film remains relatively stable in both composition and thickness following ozonation. However, some subtle chemical changes in the contamination layer induced by the ozonation process are found to profoundly affect the electrical properties of the gold-gold contact, reducing the resistance by more than 3 orders of magnitude and considerably reducing variability in the contact resistance between contact events. These results clearly demonstrate the critical role both positive and negative of the latent contamination present on the contact surfaces.

Relay Races

This article illustrates that micro-electro-mechanical systems (MEMS) promises relief to designers seeking a smaller electromechanical option. A MEMS relay could offer the true ON/OFF characteristics of its conventional electromechanical equivalent in a device small enough to be integrated on the same die with semiconductor circuits. Raytheon Co.’s radio and terminal business in Fort Wayne, Ind., a unit of the Command, Control and Communication Systems division, believes MEMS will help produce highly efficient, software-controlled, digital radios for the military. The MEMS devices would replace solid-state switches and their associated components used to switch frequencies in communications systems. With fewer components, size, weight, and power consumption will shrink. The pursuit of a MEMS relay has developers experimenting with various actuating mechanisms and researching the materials and fabrication challenges associated with those mechanisms. Radant Technology plans to incorporate the Analog Devices design in a balloon-borne radar antenna that will scan for incoming cruise missiles from a height of 15,000 feet.