Microelectromechanical Switch Research Articles

Unified nonlinear quasistatic and dynamic analysis of RF-MEMS switches

In this paper, the modified couple stress-based strain gradient theory is used to provide a unified nonlinear model of the quasistatic and dynamic behavior of an electrostatic microelectromechanical systems microbeam capacitive switch of the Euler–Bernoulli type. Our model not only accounts for the contact between the microbeam and the dielectric substrate using nonlinear springs and dampers, but also accounts for the system size by introducing an internal material length scale parameter. In view of the size of the microbeam and electrostatic gaps involved, Casimir and Van der Waals forces, damping force due to the squeeze membrane effect and electrostatic force with first-order fringing field effects were accounted for in our model. The resulting nonlinear system of PDEs was expanded into a coupled system using series expansion and integrated into ODEs using weighted residuals of the Galerkin type. To overcome the difficulties associated with the determination of the contact length, the Heaviside function for deflection was replaced with a Heaviside function for the contact length, and an iterative procedure was adopted to determine the contact length. To obtain the time variation of the microbeam, the dynamic system of equations was solved using Newmark’s integration scheme. The outcome of our work shows the dependence of the pull-in voltage upon the inertia force, slenderness ratios of the microbeam, the electrostatic gap and the initial boundary conditions of the switch. In addition, we were also able to provide the full history of the microbeam past the pull-in threshold.

An ultra-low voltage MEMS switch using stiction-recovery actuation

In this paper, an ultra-low voltage microelectromechanical system (MEMS) switch is proposed, modeled and demonstrated. Through the introduction of torsional hinges, stiction-recovery actuation was possible, and thus irreversible stiction could be overcome. Owing to this see-saw-like actuation, the switch could be freely designed to have low stiffness resulting in an ultra-low actuation voltage. The proposed switch shows an actuation voltage of around 3 V, which is especially low compared with typical values of several tens of volts in conventional microelectromechanical switches. Variation of the actuation voltage stayed under 12% during 106 cycles. Switching performance was degraded by an increase of contact resistance rather than in-use stiction. Using the proposed switches, low-voltage mechanical logic gates were also proposed and successfully demonstrated, operating at VDD of 3 V.

Topology Optimization of Stressed Capacitive RF MEMS Switches

Geometry design can improve a capacitive radio-frequency microelectromechanical system switch's reliability by reducing the impacts of intrinsic biaxial stresses and stress gradients on the switch's membrane. Intrinsic biaxial stresses cause stress stiffening, whereas stress gradients cause out-of-plane curling. We use topology optimization to systematically generate designs, by minimizing stress stiffening, minimizing curling, or minimizing stress stiffening while constraining the curling behavior. We present the corresponding problem formulations and sensitivity derivations and discuss the role of key elements in the problem formulation.

Nano- and micro-electromechanical switch dynamics

This paper reports theoretical analysis and experimental results on the dynamics of piezoelectric MEMS mechanical logic relays. The multiple degree of freedom analytical model, based on modal decomposition, utilizes modal parameters obtained from finite element analysis and an analytical model of piezoelectric actuation. The model accounts for exact device geometry, damping, drive waveform variables, and high electric field piezoelectric nonlinearity. The piezoelectrically excited modal force is calculated directly and provides insight into design optimization for switching speed. The model accurately predicts the propagation delay dependence on actuation voltage of mechanically distinct relay designs. The model explains the observed discrepancies in switching speed of these devices relative to single degree of freedom switching speed models and suggests the strong potential for improved switching speed performance in relays designed for mechanical logic and RF circuits through the exploitation of higher order vibrational modes.

An Efficient Multi-Objective Genetic Algorithm for MEMS Tuning

Micro-electromechanical switches (MEMS) with good performance in high frequency application such as linearity, no DC power consumption, no noise, small size and capability to co-fabrication on the chip today, it is noteworthy. the evolutionary approach in the design optimization of MEMS is a novel and promising research area. The problem is of a multi-objective nature; hence, multi-objective evolutionary algorithms (MOEA) are used. In this paper we introduced geometrical parameters of micro-electromechanical switch as input parameters or variables of multi-objective genetic algorithms then we compute electrical parameter of mems switch That show good performance and relation between theoretical parameter and simulated results is good.

Energy-Based Approach to Adaptive Pulse Shaping for Control of RF-MEMS DC-Contact Switches

This paper presents a closed-form analysis to design a pre-shaped open-loop driving actuation waveform to reduce the bouncing effect while maintaining fast switching of a microelectromechanical system contact switch. A single-degree-of-freedom model and the principle of energy conservation were utilized to design a shaped voltage waveform to close the switch with low impact speed. The method can easily adapt the voltage waveform to the variance of pull-in voltages due to imperfect manufacturing and to observed pull-in voltage drift during operation. The analytical calculation of the actuation pulse and the closure time of the switch with near zero velocity agree with simulation and are validated experimentally on the set of cantilever switches. It is shown that the analysis is also applicable for electrostatically actuated devices with more general geometries.

A High-Reliability High-Linearity High-Power RF MEMS Metal-Contact Switch for DC–40-GHz Applications

This paper presents an mN-level contact and restoring force RF microelectromechanical systems metal-contact switch exhibiting high reliability, high linearity, and high power handing for dc-40-GHz applications. The device, which is insensitive to stress and temperature effects, achieves 1.2-1.5 mN of contact force (per contact) from 80 to 90 V and 1.0 mN of restoring force (per contact). The up-state capacitance is 8 fF, resulting in an isolation of 46, 31, and 14 dB at 1, 6, and 40 GHz, respectively. Measured results show switch resistances of 1-2 Ω and a reliability of >; 100 million cycles at 2-5 W under cold switching at 100 mW under hot-switching conditions, in an unpackaged and standard laboratory environment. Furthermore, the device was tested under prolonged hold-down conditions and demonstrated excellent RF power handling (>;10 W) and dc current handling (>;1 A) capability.

Reduced-Size Low-Voltage RF MEMS X-Band Phase Shifter Integrated on Multilayer Organic Package

This paper presents an X-band two-bit phase shifter that integrates single-pole four-throw (SP4T) piezoelectric microelectromechanical switches with a compact 3-D passive design on a liquid crystal polymer (LCP) organic substrate. The multilayer LCP process allows a low-cost and lightweight circuit that can easily be integrated with other radio frequency front-end components, such as an antenna, at the packaging level. By routing lines onto embedded multilayers, a 22.5% reduction in area is achieved. In addition, low-loss piezoelectric SP4T switches with a 7 V actuation voltage are used to switch between different phase delays. The phase shifter exhibits a loss of 0.75 dB/bit with 2.25° average phase error at 10 GHz.

High-Power Magnetically Actuated Microswitches Fabricated in Laminates

We report on a microelectromechanical magnetic dc switch that operates at low control voltage (3 V), magnetically latches at on/off stage, and switches large voltages and currents, both dc and ac, in under 3 ms. The device, which measures 3 mm t 3 mm fully packaged, has been measured to handle 0.97 A at 10.6 Vdc (10.2 W) and 15 W at 110 Vac. This represents a remarkable power-handling capability for such a small device, which is almost impossible to achieve in conventional microelectromechanical system devices. The device is constructed using laminate MEMS technology, which is fully compatible with large-scale manufacturing by advanced microelectronics packaging manufacturers. This device has important applications in electronic switching applications for dc circuits, ac circuits, and, potentially, for RF circuits.

Fast RF-CV Characterization Through High-Speed 1-port S-Parameter Measurements

We present a fast radio frequency-capacitance-voltage (RF-CV) method to measure the CV relation of an electronic device. The approach is more accurate, much faster, and more cost effective compared to the existing off-the-shelf solutions. Capacitances are determined using a single-frequency 1-port S-parameter setup constructed from discrete components. We introduce a new way to correct for nonlinearities of the used components, which greatly increases the accuracy with which the phase and magnitude of the reflected signal is measured. The measurement technique is validated on an RF microelectromechanical systems capacitive switch and a barium-strontium-titanate tunable capacitor. Complete CV curves are measured in less than a millisecond, with a measurement accuracy well below 1%.

Experimental isolation of degradation mechanisms in capacitive microelectromechanical switches

DC and bipolar voltage stresses are used to isolate mechanical degradation of the movable electrode from charging mechanism in microelectromechanical capacitive switches. Switches with different metals as the movable electrode were investigated. In titanium switches, a shift in the pull-in voltages is observed after dc stressing whereas no shift occurs after the bipolar stressing, which is to be expected from charging theory. On switches with similar dielectric but made of aluminium, the narrowing effect occurs regardless if dc or bipolar stressing is used, which indicates the mechanical degradation as the mechanism responsible.

Single and multiple optical switches that use freestanding silicon nanowire waveguide couplers

Silicon photonic devices consisting of nanowire waveguides are a promising technology for on-chip integration in future optical telecommunication and interconnection systems based on silicon-large scale integration fabrication. However, the accommodation of variable optical components on a chip remains challenging due to the small size of microchips. In this study, we investigated the characteristics of a microelectromechanical silicon nanowire waveguide switch with a gap-variable coupler. Due to its capacitive operation, the proposed waveguide switch consumed negligible power relative to switches that use a thermo-optical effect and carrier injection. The proposed switch was characterized using analyses based on coupled-mode theory for rectangular waveguides, as well as a simulation using the finite difference time domain method. A 2×2 single switch with an improved configuration and a 2×6 multiple switch composed of the 2×2 switches was designed and fabricated by a combination of electron beam lithography, fast-atom beam etching and hydrofluoric acid vapor sacrificial etching. The properties of the switches were measured and evaluated at a wavelength of 1.55 µm. A new miniature silicon optical switch requires far less electrical power than schemes employing thermo-optic effects or carrier injection. The device, developed by Yuta Akihama and Kazuhiro Hane from Tohoku University in Japan, relies on optical coupling between two arms in a 2×2 silicon waveguide coupler. By allowing one of the arms to move and connecting it to an electrostatic comb-drive actuator, an electrical voltage can be used to vary the gap between the waveguide arms and thus control the amount of coupling. The result is an efficient switch that operates at the wavelength of 1.55 µm and has a footprint of 100 µm×100 µm. As well as demonstrating a single 2×2 switch, the researchers also cascaded several devices together to construct a 2×6 switch.

Direct measurements and numerical simulations of gas charging in microelectromechanical system capacitive switches

Gas breakdown in microelectromechanical system capacitive switches is demonstrated using high resolution current measurements and by particle-in-cell/Monte Carlo collision (PIC/MCC) simulations. Measurements show an electric current through a 3 μm air gap increasing exponentially with voltage, starting at 60 V. PIC/MCC simulations with Fowler-Nordheim [Proc. R. Soc. London, Ser. A 119, 173 (1928)] field emission reveal self-sustained discharges with significant ion enhancement and a positive space charge. The effective ion-enhanced field emission coefficient increases with voltage up to about 0.3 with an electron avalanche occurring at 159 V. The measurements and simulations demonstrate a charging mechanism for microswitches consistent with earlier observations of gas pressure and composition effects on lifetime.

Impact of the Surface Roughness Description on the Electrical Contact Resistance of Ohmic Switches Under Low Actuation Forces

At the present time, the insertion of radio frequency microelectromechanical switches into real architecture requires reduced actuation voltages, reduced dimensions, and better control of the electrical and electromechanical behavior that gives more importance to surface effects, their understanding, and modeling. The use of such devices requires the development of methods for estimating the contact performances as a function of surface roughness, contact materials, and contact topologies. With increase in computation capabilities, the rough surface topography can be implemented in the finite element model but implies long calculation times or even calculation overloading if a high definition of the roughness is desired. To reduce these limitations, assumptions on the microgeometry are required. This paper treats, by use of finite element modeling, the influence of the definition of roughness of contacting switch members on the electrical contact resistance of resistive switches, and investigates the error introduced by using a minimum defined atomic force microscope sampling interval of 10 nm. The present numerical analysis is implemented for switch test structures.

Analysis and numerical solution of a piezoelectric frictional contact problem

We consider a mathematical model which describes the frictional contact between an electro-elastic–visco-plastic body and a conductive foundation. The contact is modelled with normal compliance and a version of Coulomb’s law of dry friction, in which the stiffness and the friction coefficients depend on the electric potential. We derive a variational formulation of the problem and we prove an existence and uniqueness result. The proof is based on a recent existence and uniqueness result on history-dependent quasivariational inequalities obtained in [15]. Then we introduce a fully discrete scheme for solving the problem and, under certain solution regularity assumptions, we derive an optimal order error estimate. Finally, we present some numerical results in the study of a two-dimensional test problem which describes the process of contact in a microelectromechanical switch.

A Multifunctional Reconfigurable Pixeled Antenna Using MEMS Technology on Printed Circuit Board

A multifunctional reconfigurable pixeled antenna that uses microelectromechanical switches (MEMS) and operates within the 4-7 GHz frequency band is presented. The proposed antenna is a highly reconfigurable planar surface radiator composed of an npx × npx matrix of metallic pixels interconnected through MEMS switches. The antenna can be reconfigured to perform multiple functions such as: frequency tuning, pattern diversity, and polarization adaptation. A functional prototype using integrated MEMS switches was fabricated on a printed circuit board substrate, to show its feasibility and the impact of MEMS switches during operation. Simulated and measured data of the return loss and radiation characteristics of the antenna are presented.

A MEMS Microreed Switch With One Reed Embedded in the Silicon Substrate

This paper presents design, fabrication, and characterization of a novel microelectromechanical microreed switch, which consists of two Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> magnetic plates as microreeds. One is embedded in a silicon trench. The other is suspended above the substrate and supported by a pair of crab-leg flexures from the two sides. Both Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> plates are split into two long, narrow strips to improve the sensitivity. The switch is actuated by bringing an external magnet closer to the switch. The magnetic field required to turn on the switch can be as low as 0.5 mT and the initial contact resistance is <; 10 Ω with gold contacts. The switch has been tested to pass more than 40 million hot switching cycles at 2 mA current at room temperature when packaged at wafer level with SU-8 sealing. The die size is 1.7 × 1.8 × 1.1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The proposed microreed switch can be used as the proximity sensor to sense the magnetic field. It also has the potential to replace the conventional reed switch in portable electronics, such as cellular phones, hearing aids, and laptops, where conserving battery power and device size is critical.

Analysis of fluid-structure interaction for predicting resonant frequencies and quality factors of a microcantilever on a squeeze-film

The dynamic behavior of a flexible microcantilever vibrating above a substrate such as the cantilever-based structure of a radio frequency microelectromechanical switch is strongly affected by the motion of gas between the microcantilever and the substrate. In this paper, parameter studies to investigate the effects of geometry, material properties of a microcantilever, and ambient pressure on the resonant frequencies and quality factors of the microcantilever are described. A Reynolds-equation-based continuum model is used to derive the gas force reflecting the gas rarefaction effect due to the size effect of MEMS packed at low ambient pressure. The frequency response function of an inertially-excited microcantilever is developed using the mode superposition method. One interaction parameter, including information on geometry, material properties of a microcantilever, and ambient pressure, is defined to investigate the fluidstructure interaction in a microcantilever vibrating on a squeeze-film. The quality factors of the first three bending modes increase with the decreasing interaction parameter. The changing trend of associated resonant frequencies depends on the order of the bending mode.

Impact of adsorbed organic monolayers on vacuum electron tunneling contributions to electrical resistance at an asperity contact

Electrical contact resistance measurements are reported for RF micro-electromechanical switches situated within an ultrahigh vacuum system equipped with in situ oxygen plasma cleaning capabilities. Measurements were performed on fused (permanently adhered) switches with Au/Au contacts and functioning switches with Au/RuO2 contacts in both the presence and absence of adsorbed monolayers of pentane and dodecane. For switches adhered in the closed position, adsorption occurs only in regions external to direct contact. For functioning switches, however, it can occur either within or exterior to the contact. The data are analyzed within the framework of two distinct geometries, to explore how the presence of adsorbed molecules in regions close to the contact may impact vacuum tunneling contributions to the experimentally measured resistance: (1) The resistance associated with direct contact in parallel with a vacuum tunneling path, which upon uptake of the monolayer is replaced by the molecular resistance and (2) a series connection of the direct contact resistance with the molecular layer after adsorption occurs, with the vacuum tunneling path assumed to be negligible. In all cases, the experimental results quantitatively favor scenario (1), whereby uptake of the molecular layer effectively shuts down the vacuum tunneling path, in this case approximately 30 Ω in the absence of an adsorbed film. The methods described herein thus constitute a new and original approach to documenting vacuum tunneling levels in regions of close proximity.

A Design of Thermo-Electrostatic Actuated Microelectromechanical Switch with Low Voltage and Fabrication Efforts

Requirement of voltage up-converters due to high pull-in voltage is one of the main problems by merely electrostatic actuated Microelectromechanical system-based switches. Thermally actuated switches are another alternatives but with very high power dissipation. In this paper a low voltage switch is demonstrated, which uses a combined thermo-electrostatic actuator. The switch can be integrated with standard CMOS circuits without any up-converters. Thermally power dissipation for the switch is lower than just thermal actuators. The switching time is about 70µs and the maximal temperature of thermal actuator is lower than 150oC which cannot cause any longtime damage. Isolation and Insertion Loss quantities have been calculated to -25dB and -0.65dB at 20GHz from HFSS results respectively.