Microelectromechanical Switch Research Articles

Novel capacitance evaluation model for microelectromechanical switch considering fringe and effect of holes in pull-up and pull-down conditions

This paper reports a model and investigates into capacitive studies of microelectromechanical system switch through considerations of material’s behavior on various parameters like dielectric thickness, thickness and width of bridge structure and also with distance between two electrodes including fringe field effect on pull up and down capacitance. The pull up capacitance and pull-down capacitances are investigated considering effect of fringe field and holes independently as well as combined together. In pull up state, the total capacitance is found to be 6.9945 fF in which three components of the capacitance $$ C_{1,u} $$, $$ C_{2,u} $$ and $$ C_{3,u} $$ contribute 1.1624 fF (16.61%), 2.1924 fF (31.34%) and 3.6397 fF (52.03%) respectively. In pull down state, the total capacitance is found as 2.1439 pF and capacitance sharing of each component ($$ C_{1,d} $$), ($$ C_{2,d} $$) and ($$ C_{3,d} $$) is 0.6503 pF (30.33%), 1.1164 pF (52.07%) and 0.3772 pF (17.59%) respectively. The pull-down capacitance ($$ C_{t,d} $$) and pull up capacitance ($$ C_{t,u} $$) ratio is also calculated and $$ \left( {\frac{{C_{t,d} }}{{C_{t,u} }}} \right)_{max} $$ using model is found as 521.64. The capacitance ratio range is also calculated and range is 48.41–521.64. This model can be used to measure the capacitances in symmetric and asymmetric microelectromechanical switch with error range 2–5%.

Nonlinear Behavior of Electrostatically Actuated Microbeams with Coupled Longitudinal⁻Transversal Vibration.

Microelectromechanical switch has become an essential component in a wide variety of applications, ranging from biomechanics and aerospace engineering to consumer electronics. Electrostatically actuated microbeams and microplates are chief parts of many MEMS instruments. In this study, the nonlinear characteristics of coupled longitudinal–transversal vibration are analyzed, while an electrostatically actuated microbeam is designed considering that the frequency ratio is two to one between the first longitudinal vibration and transversal vibration. The nonlinear governing equations are truncated into a set of coupled ordinary differential equations by the Galerkin method. Then the equations are solved using the multiple-scales method and the nonlinear dynamics of the internal resonance is investigated. The influence of bias voltage, longitudinal excitation and frequency detuning parameters are mainly analyzed. Results show that using the pseudo-arclength continuation method, the nonlinear amplitude–response curves can be plotted continuously. The saturation and jump phenomena are greatly affected by the bias voltage and the detuning frequency. Beyond the critical excitation amplitude, the response energy will transfer from the longitudinal motion to the transversal motion, even the excitation is employed on the longitudinal direction. The large-amplitude jump of the low-order vibration mode can be used to detect the variation of the conditions or parameters, which shows great potential in improving precision of MEMS switches.

An MRI Compatible RF MEMs Controlled Wireless Power Transfer System.

In magnetic resonance imaging (MRI), wearable wireless receive coil arrays are a key technology goal. An MRI compatible wireless power transfer (WPT) system will be needed to realize this technology. An MRI WPT system must withstand the extreme electromagnetic environment of the scanner and cannot degrade MRI image quality. Here, a WPT system is developed for operation in MRI scanners using new microelectromechanical RF switch (RF MEMs) technology. The WPT system includes a class-E power amplifier, RF MEMs automated impedance matching, a primary coil array employing RF MEMs power steering, and a flexible secondary coil with class E rectification. To adapt WPT technology to MRI, techniques are developed for operation at high magnetic field, and to mitigate the RF interactions between the scanner and WPT system. A major challenge was the identification and suppression of noise and harmonic interference, by gating, filtering, and rectifier topologies. The system can achieve 63% efficiency while exceeding 13 W delivery over a coil distance of 3.5 cm. For continuous WPT beyond 5W, added filters and full-wave class E rectification lowers harmonic generation at some cost to efficiency, while image SNR reaches about 32% of the ideal. RF-gated WPT, which interrupts power transfer in the MRI signal acquisition interval, achieves SNR performance to within 1 dB of the ideal. With further refinement, the inclusion of WPT technology in MRI scanners appears completely feasible.

The modeling design integral the electrostatic microelectromechanical switch of capacitive type

This article presents the optimization and static modeling of the design an integral microelectromechanical switch of capacitive type based on a parametric 3D model using finite element analysis software complex ANSYS. The values of the pull-down voltage and switching time are determined. The obtained results give a good theoretical help in the development of various high-performance electrostatic microelectromechanical switches.

Silicon photonic microelectromechanical switch using lateral adiabatic waveguide couplers.

A silicon photonic waveguide switch using adiabatic couplers with lateral comb-drive actuators is designed, fabricated, and tested for microelectromechanical optical matrix switch. One of the waveguides of the adiabatic coupler is moved laterally by three actuators for varying the coupler gap, which enables to switch the path of the waveguides. The coupler waveguides with 250 nm thickness consist of a movable tapered waveguide from 400 nm to 500 nm in width and 50 μm in length and a straight waveguide of 400 nm in width. The three actuators are ultra-small electrostatic comb-drive and move the two movable tapered waveguides. The switch's transmission characteristics were measured as a function of the coupler gap. Around a coupler gap of 109 nm, the port isolation of 16.7 dB was obtained. The switch's insertion loss was roughly estimated to be less than 1 dB. The switching time was 36.7 μsec under the present experimental condition. Moreover, 64 switches were arrayed in a 125 μm period square mash waveguide and an 8 x 8 matrix switch was composed. The matrix switch was also tested.

Analytical Approach in the Development of RF MEMS Switches

Currently, the technology of microelectromechanical systems is widely used in the development of high-frequency and ultrahigh-frequency devices. The most important requirements for modern and advanced devices of the ultra-high-frequency range are the reduction of weight and size characteristics, power consumption with an increase in their functionality, operating frequency and level of integration. Radio frequency microelectromechanical switches are developed using the technology of the manufacture of CMOS-integrated circuits. Integrated radio frequency control circuits require low control voltages, the high ratio of losses to the isolation in the open and closed condition, high performance and reliability. This review is devoted to the analytical approach based on the knowledge of materials, basic performance indices and mechanisms of failure, which can be used in the development of radio-frequency microelectromechanical switches.

A Laterally Driven MEMS Inertial Switch With Double-Layer Suspended Springs for Improving Single-Axis Sensitivity

A novel laterally driven inertial switch with double-layer springs has been proposed and fabricated by surface micromachining technology for improving single-axial sensitivity. The symmetrical distribution of double-layer suspended springs and the constraint structures limits the displacement of the proof mass in the off-axis sensitive direction under an acceleration disturbance. The ANSYS simulation results reveal that compared with the inertial switch with one layer springs, the symmetrical distribution of double-layer serpentine springs effectively reduces the displacement of the proof mass in the off-axis direction. The design of symmetrical distribution of double-layer serpentine springs plays an important role in resisting small acceleration disturbance from the off-axis sensitive $z$ -direction, and the constraint structures can resist the large acceleration disturbance. The modal analysis, contact time, and the collision response in the inertial switch have also been simulated and discussed. Finally, the proposed inertial switch has been fabricated successfully, and the prototype is tested by a dropping hammer system. The test results show that the threshold level of the fabricated inertial switch is 272 g with 20- $\mu \text{s}$ contact time. The combined efforts of double-layer suspended springs and constraint structures effectively lower off-axis sensitivity and improve the single-axis sensitivity of the microelectromechanical system inertial switch.

Charging mechanisms in Y2O3 dielectric films for MEMS capacitive switches

The potential application of Yttrium Oxide (Y2O3) in capacitive Micro-Electro-Mechanical Switches (MEMS) dielectric films is investigated. The electrical properties and the impact of electrical stress on capacitive switches have been investigated with the aid of Metal-Insulator-Metal (MIM) capacitors and MEMS capacitive switches in order to determine the suitability of this material for such application. The assessment in MIMs consisted of recording the current-voltage characteristics in order to determine the transport mechanisms and the charge injection by injecting electrodes during the charging process. The MEMS switches were employed to monitor the charge injection through the bridge during pull-in state and collection during the pull-up state. The process was performed under different stress conditions in order to determine the impact of stressing electric field intensity.

Improved broadband (75–110 GHz) radio frequency characteristics of MEMS shunt switches on quartz substrate

This paper presents improved W-band (75–110 GHz) radio frequency characteristics of micro-electromechanical switches in T and π-matched configurations. The switch structures consist of Au metallic bridge (s) suspended over the coplanar waveguide (CPW) signal line drawn on quartz substrate. Here, a high impedance transmission line is introduced on both the sides of the bridge structure to reduce the return loss. To further tune up the broadband RF response the bridge width (40–80 µm) as well the dielectric thickness (0.15–0.18 µm) are varied. At optimum condition (bridge width: 60 µm; dielectric thickness: 0.18 µm), the T-matched RFMEMS switch structure exhibits return loss better than − 20 dB; insertion loss ~ − 0.2 dB and isolation better than − 30 dB in full W-band frequency range. In π-match configuration, a short section of high impedance transmission line is being introduced between two switch structures for impedance matching. RF parameters of the π-matched shunt switch structure are studied as a function of width (10–40 µm) and length (30–180 µm) of the high impedance transmission line. At optimum condition (line width: 30 µm; length: 130 µm), the π-matched switch structure exhibits return loss: better than − 15 dB; insertion loss: better than − 0.5 dB; and isolation: better than − 45 dB over the entire W-band. From the equivalent circuit modeling, the equivalent inductance, capacitance and resistance values for the optimized switch structures are also reported.

Three-Dimensionally Printed Micro-electromechanical Switches.

Three-dimensional (3D) printers have attracted considerable attention from both industry and academia and especially in recent years because of their ability to overcome the limitations of two-dimensional (2D) processes and to enable large-scale facile integration techniques. With 3D printing technologies, complex structures can be created using only a computer-aided design file as a reference; consequently, complex shapes can be manufactured in a single step with little dependence on manufacturer technologies. In this work, we provide a first demonstration of the facile and time-saving 3D printing of two-terminal micro-electromechanical (MEM) switches. Two widely used thermoplastic materials were used to form 3D-printed MEM switches; freely suspended and fixed electrodes were printed from conductive polylactic acid, and a water-soluble sacrificial layer for air-gap formation was printed from poly(vinyl alcohol). Our 3D-printed MEM switches exhibit excellent electromechanical properties, with abrupt switching characteristics and an excellent on/off current ratio value exceeding 106. Therefore, we believe that our study makes an innovative contribution with implications for the development of a broader range of 3D printer applications (e.g., the manufacturing of various MEM devices and sensors), and the work highlights a uniquely attractive path toward the realization of 3D-printed electronics.

A 0.2 V Micro-Electromechanical Switch Enabled by a Phase Transition.

Micro-electromechanical (MEM) switches, with advantages such as quasi-zero leakage current, emerge as attractive candidates for overcoming the physical limits of complementary metal-oxide semiconductor (CMOS) devices. To practically integrate MEM switches into CMOS circuits, two major challenges must be addressed: sub 1 V operating voltage to match the voltage levels in current circuit systems and being able to deliver at least millions of operating cycles. However, existing sub 1 V mechanical switches are mostly subject to significant body bias and/or limited lifetimes, thus failing to meet both limitations simultaneously. Here 0.2 V MEM switching devices with ≳106 safe operating cycles in ambient air are reported, which achieve the lowest operating voltage in mechanical switches without body bias reported to date. The ultralow operating voltage is mainly enabled by the abrupt phase transition of nanolayered vanadium dioxide (VO2 ) slightly above room temperature. The phase-transition MEM switches open possibilities for sub 1 V hybrid integrated devices/circuits/systems, as well as ultralow power consumption sensors for Internet of Things applications.

Suppression of contact bounce in beam-type microelectromechanical switches using a feedforward control scheme

This paper presents a feedforward control strategy for suppressing the contact bounces in electrostatically driven microswitches. The mathematical model is first developed, including the effects of mid-plane stretching, fringing field capacitance, squeeze-film damping together with the effect of elastic contact with the stationary dielectric substrate. The contact between the movable and the stationary electrodes is modeled as a foundation made by a combination of nonlinear springs and dampers. To discretize the system of partial differential equations of the electrostatic switch into ordinary differential equations, the Galerkin’s method is employed. Both fixed–fixed and fixed–free configurations of the switch are investigated. A parametric study is presented to establish the robustness and efficacy of the proposed technique to mitigate the contact bounces. Additionally, the effect of variation in the extent of damping, stretching parameter and input voltage on switching time is investigated.

Material selection methodology for radio frequency (RF) microelectromechanical (MEMS) capacitive shunt switch

This paper describes the process of selecting the most optimum Radio Frequency Micro- electro- mechanical-systems (RF-MEMS) switch design using Ashby’s methodology. The switches are compared on the basis of parameters like actuation voltage, insertion loss, isolation and switching time using material selection charts. The chart shows that a low-voltage metal-to-metal contact shunt capacitive RF-MEMS having a bridge structure with Si-GaAs substrate, electroplated gold contacts and silicon nitride dielectric layer, is the most optimum of all the switches considered.

RF-MEMS-Based Bandpass-to-Bandstop Switchable Single- and Dual-Band Filters With Variable FBW and Reconfigurable Selectivity

Bandpass (BP)-to-bandstop (BS) switchable filters using radio frequency microelectromechanical system switch are presented here. The filters are implemented in both single- and dual-band versions with variable fractional bandwidth (FBW). Tuning of transmission zeros (TZs) and transmission poles (TPs) for BP filter (BPF) and BS filter (BSF), respectively, is achieved in both single- and dual-band cases leading to reconfigurable selectivity. The first odd-mode frequency of the filter is suppressed using a fixed capacitor and the second odd mode is brought closer to the first even-mode with another variable capacitor to form the passband(s). The second capacitor tunes both the second odd mode and TZs (for BPF) or TPs (for BSF) minimizing the requirement of any extra tuning element. In a single-band fabricated BPF, tuning second odd mode gives the FBW variation of 9.3%–72.7% with TZ on the lower side and 5.6%–55.6% with TZ on the higher side of the passband. The 15-dB FBW of a single-band BSF having TP on both sides of the stopband varies over 5.2%–20.7%. The two passbands of a dual-band BPF independently vary over 4.5%–24% and 4.5%–13%. Also, the 15-dB FBW of the first and second stopbands of BSF independently varies over 6.5%–13.2% and 1.5%–3.6%, respectively.

Finite element based contact analysis of radio frequency MEMs switch membrane surfaces

Finite element simulations were performed to determine the contact behavior of radio frequency (RF) micro-electro-mechanical (MEM) switch contact surfaces under monotonic and cyclic loading conditions. Atomic force microscopy (AFM) was used to capture the topography of RF-MEM switch membranes and later they were analyzed for multi-scale regular as well as fractal structures. Frictionless, non-adhesive contact 3D finite element analysis was carried out at different length scales to investigate the contact behavior of the regular-fractal surface using an elasto-plastic material model. Dominant micro-scale regular patterns were found to significantly change the contact behavior. Contact areas mainly cluster around the regular pattern. The contribution from the fractal structure is not significant. Under cyclic loading conditions, plastic deformation in the 1st loading/unloading cycle smooth the surface. The subsequent repetitive loading/unloading cycles undergo elastic contact without changing the morphology of the contacting surfaces. The work is expected to shed light on the quality of the switch surface contact as well as the optimum design of RF MEM switch surfaces.

Modeling, design, and simulation of a radio frequency microelectromechanical system capacitive shunt switch

AbstractThis tutorial paper presents an empirical model of a capacitive radio frequency microelectromechanical system switch in the microwave domain. The simulation results of the mechanical and electrical aspects of the proposed model were computed with Matlab. The mechanical modeling is validated by COMSOL software through the finite element method to determine the spring constant and the necessary applied voltage. The electromagnetic simulation results are validated by 3 different software: the High‐Frequency Structure Simulator based on the finite element method, the Computer Simulation Technology based on finite integration technique method, and the Advanced Design System based on the method of moments. The obtained results are performed in both down (OFF) and up (ON) states in the frequency range of 1 to 40 GHz, and the considered performance benchmarks are the insertion loss, return loss, isolation, and phase.

Dielectric Charging Asymmetry in SiN Films Used in RF MEMS Capacitive Switches

This paper presents a systematic investigation of the effect of stressing bias polarity to the discharge process of plasma enhanced chemical vapor deposition SiN films that have been fabricated under different deposition conditions. Dielectric charging asymmetry has been observed on the utilized films of metal-insulator-metal capacitors and microelectromechanical systems capacitive switches, since charging is enhanced when negative polarization bias is applied to the top electrode. In addition, it is shown that deposition conditions play a key issue role on the degree of this asymmetry. Finally, a physical model which assumes that hopping dominates the discharging process is used in order to gain a better understanding of the processes that are responsible for the appearance of asymmetric dielectric charging and the results correlate with the material’s electrical properties.

MEMS switch integrated radio frequency coils and arrays for magnetic resonance imaging.

Surface coils are widely used in magnetic resonance imaging and spectroscopy. While smaller diameter coils produce higher signal to noise ratio (SNR) closer to the coil, imaging larger fields of view or greater distance into the sample requires a larger overall size array or, in the case of a channel count limited system, larger diameter coils. In this work, we consider reconfiguring the geometry of coils and coil arrays such that the same coil or coil array may be used in multiple field of view imaging. A custom designed microelectromechanical systems switch, compatible with magnetic resonance imaging, is used to switch in/out conductive sections and components to reconfigure coils. The switch does not degrade the SNR and can be opened/closed in 10 μs, leading to rapid reconfiguration. Results from a single coil, configurable between small/large configurations, and a two-coil phased array, configurable between spine/torso modes, are presented.

Narrowband microwave microelectromechanical switch on gallium arsenide substrates for operation in a frequency band of 10–12 GHz

Discrete electrostatic microwave microelectromechanical switches on gallium arsenide wafers are designed and fabricated. The possibility of integrating the switches in one circuit with monolithic integrated circuits of transreceiving devices fabricated in one production cycle is estimated.

Viscoelasticity Recovery Mechanism in Radio Frequency Microelectromechanical Switches

Radio frequency microelectromechanical system (RF MEMS) switches require a lifetime of 20 years, during which the devices must operate without failure. During operation, the RF MEMS switches are subjected to prolonged actuation which may induce the problems of charge trapping and mechanical relaxation leading to stiction of the moving membrane. In this paper, we suggest an innovative recovery procedure that allows to avoid the stiction. At regular intervals, the switch is opened and an electrical current forced through the suspended membrane can effectively fully recover the switch. Using the topography analysis, we show that the restoring mechanism is based on the recovery of the mechanical properties of the moving bridge during the current flow. The validity of the procedure is demonstrated with the application of the recovery system on several devices for 20 consecutive cycles.