Pull-down Voltage Research Articles

High-performance inline RF MEMS switch for application in 5G mobile networks

This article presents the results of the design and analysis of a radio-frequency switch made using microelectromechanical systems technology. The device is the capacitive switch with a hybrid type of contact, in which the movable electrode of the structure – the metal membrane is part of the microwave signal line of the coplanar waveguide. The switch design is characterized by a high capacitance ratio and low contact resistance. The zig-zag elastic suspension is used to reduce the value of the pull-down voltage – 2 V and the switching time ∼ 7 us. The central resonant frequency of the switch is 3.8 GHz. In this case, in the open state, the value of the insertion loss is not more than -0.2 dB and the isolation value in the close state is not less than -55 dB. The effective frequency range is the S-band, as well as the C-, X- and Ku-band, in which the isolation value is at least -30 dB. The presented inline RF MEMS switch is suitable for use in various types of ground and satellite communications, in particular for devices and systems of 5G mobile networks.

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.

Conception of a Malleable Multiband Antenna Using RF MEMS Varactors for WIMAX802.16d and X Band

An original and dynamic multi-band CPW-fed antenna with two U notch slots is conceived throughout this paper. Each slot holds a MEMS Varactor. According to the state of these variable capacitors a Single or a Dual-Band can be obtained to cover a range of frequencies in IEEE802.16d (2-11GHz) and X band. The proposed antenna of total area equal to 25.6×27.9mm2 is successfully conceived and simulated by using ADS momentum, it is mounted over a low permittivity substrate of Taconic TL6 with 1.6mm thickness and dielectric loss tangent of 0.0019. The return loss, radiation pattern, power radiation, bandwidths have been presented and discussed. Additionally, in order to determine the needed pull-down voltages, a mechanical study of the used MEMS Varactors has been presented, along with the implemented of high resistive DC bias lines of SiCr with Rbias=10kΩ/sq to activate varactors.

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.

Fabrication process induced changes in scattering parameters of meander type RFMEMS shunt switch

This paper reports about the effect of fabrication process induced changes on scattering parameters of RF MEMS switch structure with meander geometry for 18–40 GHz (Ka-band) application. The designed structure showed a return loss better than 15 dB with a maximum isolation of 43 dB at 35 GHz. From the parametric analysis, both the return loss and isolation parameters are found to be more dependent on the meander width and dielectric thickness compared to the other dimensions. The switch structure is fabricated by surface micromachining technique. The effect of variation of fabricated device dimensions, due to the various processing steps, on the isolation characteristic is also studied. The fabricated structure exhibited an on–off capacitance ratio of ~200:1. The pull-down voltage is found to be 12.5 V. The return loss of the fabricated switch structure is found to be better than 13.5 dB; whereas, the maximum isolation (32 dB) is observed at 33 GHz. The shift in the resonance is due to the reduction of silicon nitride layer thickness during sacrificial layer removal (to release the switch structure) in diluted HF solution. The measured scattering parameters are found to be matching well with the corresponding simulation data of the fabricated switch dimensions.

Cantilever type radio frequency microelectromechanical systems shunt capacitive switch design and fabrication

A new cantilever type radio frequency microelectromechanical systems (RF MEMS) shunt capacitive switch design and fabrication is presented. The mechanical, electromechanical, and electromagnetic designs are carried out to get <40 V actuation voltage, high isolation, and low insertion loss for 24 and 35 GHz and the fabrication is carried out for 24 GHz RF MEMS switch. The fabricated switch shows lower than 0.35 dB insertion loss up to 40 GHz and greater than 20 dB isolation at 22 to 29 GHz frequency band. An insignificant change is observed on RF performance at 24 GHz (ΔS11 ¼ 1 dB, ΔS21 < 0.1 dB) after 200°C thermal treatment for 30 min. The switch is fabricated on quartz wafer using an in-house surface micromachining process with amorphous silicon sacrificial layer structure. Total MEMS bridge thickness is aimed to be 4 μm and consists of 2-μm-thick sputtered and 2-μm-thick electroplated gold layers. The bridge bending models and pull-down voltage simula- tions are carried out for different stress levels and equivalent Young's modulus (Eavg). © 2015 Society of Photo-Optical

On the electrostatic actuation of capacitive RF MEMS switches on GaAs substrate

The electrostatic actuation behaviour of the gold bridge in capacitive radio frequency microelectromechanical system switches, fabricated on GaAs substrate, is investigated. An unconventional imaging technique, based on the out-of-focus reflection, was used to evaluate the topographic profile of the suspended bridge and its lowering as a function of the voltage. Important parameters for the switch actuation, such as the pull-down voltage and the air gap between the bridge and the actuator, are estimated. Capacitance-voltage curves allow to evaluate the capacitance associated to the bridge in the up and down states as well as the dielectric constant of the Si3N4 layer, which covers the actuator. The experimental values of the pull-down voltage and the dielectric constant are used to extract from the theoretical equations the residual stress of the fabricated gold membrane. Finally, the current through the dielectric Si3N4 layer was measured as a function of the voltage applied to the actuator, finding that the Poole–Frenkel effect is the dominant conduction mechanism when the switch is actuated.

Mechanical nanogap switch for low-power on-board electronics

This paper presents the design fabrication and measurement of a nanogap radio frequency microelectromechanical system (RF MEMS) metal-contact switch. The prosed device generates a relatively high contact force with a low actuation voltage using a dielectric layer between the actuation electrode and the moveable beam. The actuation voltage is decreased with good reliability of the device by scaling down the gap. Beam geometry optimization allowed reaching 126 micronewtons contact force with only 10 V bias voltage. The fabricated miniature switch (80 × 50 × 0.95 µm) has indeed a pull-down voltage of 6 V and a contact resistance &lt;2 Ω with 10 V bias applied. By measuring the S-parameters, the up-state capacitance has been fitted to 22 fF. The remarkable figure-of-merit Ron × Cup = 44 fs reflects the good performance of the device. A cycling test showed the device operated for 90 min without any charging problem noted.

Multiple Moving Membrane CMUT With Enlarged Membrane Displacement and Low Pull-Down Voltage

A multiple moving membrane capacitive micromachined ultrasonic transducer ( M3-CMUT) has been fabricated and is shown to exhibit a significantly enlarged total membrane displacement ( ~ 280 nm) compared with the displacement of a conventional CMUT ( ~ 85 nm) for the same bias voltage. The M3-CMUT exhibits a significant reduction of the device pull-down voltage, while showing a much higher capacitance change, 100 fF for the M3-CMUT compared with only 20 fF for CMUT, at a dc bias of 25 V. The device performance, sensitivity, and acoustic power generation capability are primarily associated with the magnitude of the displacement of the membrane, and therefore, are enhanced through employing multiple deflectable membranes in M3-CMUT device. This high performance M3-CMUT is a promising candidate for high resolution ultrasonic imaging application.

Cantilever Beam Metal-Contact MEMS Switch

We present a new design of a miniature RF microelectromechanical system (MEMS) metal-contact switch and investigate various aspects associated with lowering the pull-down voltage and overcoming the stiction problem. Lowering the pull-down voltage in this design is based on reducing the spring constant by changing the cantilever beam geometry of the RF MEMS switch, and the stiction problem is overcome by a simple integrated method using two tiny posts located on the substrate at the free end of the cantilever beam.

High-Power RF MEMS Switched Capacitors Using a Thick Metal Process

This paper presents the design and characterization of a high-power RF microelectromechanical systems switched capacitor. The switch is based on a 4-μm-thick metal plate and four symmetrical springs. The design has low sensitivity to residual stress and stress gradients. -parameter measurements result in Cu = 0.01 pF, Cd = 0.63 pF (Cr = 6.3), a power handling >;10 W using hot switching conditions, and a switching time of ~20 μs. The pull-down voltage ( -55 V) and release voltage (Vr = 25-30 V) are stable to +/-4 V over 25°C-125°C. The design can be arrayed for -bit switched-capacitor networks. Applications areas are in high-power phase shifters and tunable filters.

An All-Metal Micro-Relay With Bulk Foil Pt–Rh Contacts for High-Power RF Applications

This paper describes the performance of stainless-steel micro-relays, with platinum-rhodium metal foil contact elements, in handling high-power RF signals. The electrical and thermal responses are described for electrostatically actuated three-terminal micro-relays that are directly assembled on printed circuit boards. The preliminary designs have footprints of 6.4 mm2. Fabricated relays have 90-V turn-on (pull-down) voltage. The down-state insertion loss and up-state isolation were better than 0.2 and 25 dB over the band of dc-5 GHz, respectively. The devices can accommodate incident RF power up to 18.5 W at 3 GHz when cooled by forced air from a mini-fan.

Effect of residual stress on RF MEMS switch

Studies have been carried out on a RF MEMS shunt switch to analyze the effect of residual stress on its electromechanical characteristics. This paper presents the simulated results as well as theoretically calculated results of a shunt switch due to the presence of residual stress gradient in respect of resonant frequency, pull down voltage and switching characteristics. The effect of introduction of holes in the beam is also studied. The calculated results, corresponding to the switch (without holes) at zero residual stress, of resonant frequency, pull-down voltage and switch on and off time are 28.14 kHz, 28.2 V, 16.35 μsec and 8.6 μsec respectively. Modal analysis of the both the structures (with and without holes) are carried out for different values of residual stress gradients. Modal analysis predicted that higher values of tensile stress gradient are not favorable for switching action. The pull-down voltages and switch on and off times are simulated at different stress gradients. With the increase in compressive stress gradient, the pull-down voltage is found to increase, whereas, switch on and off times is decreased. Corresponding to −20 MPa/μm residual stress gradient, the resonant frequency, pull-down voltage and switch on and off times are found to be 74.5 kHz, 63.5 V, 7.5 μsec and 3.36 μsec respectively. Introduction holes in the structure modified these values to 63.77 kHz, 53.1 V, 8.7 μsec, 3.92 μsec respectively.

RF MEMS Capacitive Switches for Wide Temperature Range Applications Using a Standard Thin-Film Process

In this paper, the design, fabrication, and measurements of a capacitive RF microelectromechanical systems (RF MEMS) switch with very low sensitivity to thermal stress is presented. The switch is built by thin-film technology (0.8-μm Au) and shows <;50-mV/°C variation in the pull-down voltage at 25 °C-125 °C. The effects of the residual biaxial stress and stress gradients are studied in detail and the final switch design is very tolerant to a wide range of stress. The switch exhibits excellent RF and mechanical performances, and a capacitance ratio of about 51-57 (Cu = 54-66 fF, Cd = 3.1 - 3.4 pF) is reported. The mechanical resonant frequency and quality factor are fο = 105 - 115 kHz and Qm ≈ 8, respectively, with a measured switching time of about 3-3.8 μs. The applications areas are in low-loss RF MEMS, phase shifters, and reconfigurable networks.

A Novel Membrane Process for RF MEMS Switches

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A novel fabrication process for a fixed–fixed membrane structure in RF microelectromechanical-systems switches is implemented to alter the stress-distribution and deformation of the membrane and thus vary the required actuation force. This two-step process removes UV-light-exposed photoresist first by wet dissolution of a sacrificial photoresist layer and then by oxygen reactive ion etching. During wet release, the patterned but unexposed photoresist above the membrane helps prevent stiction. Further designs of photoresist-aided membranes are demonstrated to control the measured pull-down voltage level of the switches, which is consistent with the multiphysics simulation work.<formula formulatype="inline"><tex Notation="TeX">$\hfill$</tex></formula>[2009-0281] </para>

A mechanical switch device made of a polyimide-coated microfibrillated cellulose sheet

This paper covers innovative results on the development of an electrostatically actuated mechanical switch device made of a microfibrillated cellulose sheet coated with a thin polyimide layer. For microelectronic applications, biodegradable and biocompatible nanomaterials such as microfibrillated cellulose (MFC) have attracted attention. The studied MFC sheets reveal a fibrous-like morphology composed of cellulose nanofibres leading to a high surface roughness. Moreover, the porous microstructure and the hydrophilic nature of the MFC sheet induce poor dielectric properties. These shortcomings make MFC sheets relatively unsuitable for electronic applications. In order to overcome these drawbacks, both sides of the MFC sheet are coated with a thin polyimide layer, which greatly improves the dielectric properties, moisture sensitivity and sheet surface roughness. This new sheet is then patterned in order to be used as a substrate for the fabrication of a micromechanical switch. Gold electrodes are added onto the sheet for electrostatic actuation and switch detection. The pull-down voltage of this switch, defined as the actuation voltage needed to establish a contact between the free end of the cantilever beam and the substrate, is measured to be about 55 V.

Low-voltage small-size double-arm MEMS actuator

The fabrication and characterisation of a double-arm cantilever-type metallic DC-contact MEMS actuator with low pull-down voltage are reported. Bi-layer TiW cantilevers with an internal stress gradient were fabricated using a microwave-compatible fabrication process. Owing to its small size, cantilever length (L=5–50 µm) and width (W=2–40 µm), i.e. ∼10–100 times smaller in lateral dimensions than a standard MEMS actuator, this actuator showed actuation voltages lower than 10 V. RF measurements of the 10 µm-wide actuators yielded an average insertion loss less than 1 dB and isolation higher than 40 dB up to 25 GHz. The developed actuator is well suited for integration in reconfigurable microwave circuits and systems such as reconfigurable antennas and arrays.

Cryogenic Pull-Down Voltage of Microelectromechanical Switches

Capacitively shunted microelectromechanical (MEM) switches were designed, fabricated and tested in an earlier work. The switch is composed of a coplanar waveguide (CPW) structure with an Au bridge membrane suspended above a center conductor covered with a BaTiO3 dielectric. The membrane is actuated by electrostatic force acting between the center conductor of the CPW and the membrane when a voltage is applied. We have noted that pull-down voltages for MEM switches always demonstrate an extremely strong temperature dependence when actuated at cryogenic temperature. This paper improves the pull-down voltage prediction of MEM switches at cryogenic temperature using the mechanical properties of the bridge, thin film and substrate materials used in the switch. The theoretical and experimental results of the actuation voltages of these structures as a function of temperature are presented and compared.

Analytical model for an electrostatically actuated miniature diaphragm compressor

This paper presents a new analytical approach for quasi-static modeling of an electrostatically actuated diaphragm compressor that could be employed in a miniature scale refrigeration system. The compressor consists of a flexible circular diaphragm clamped at its circumference. A conformal chamber encloses the diaphragm completely. The membrane and the chamber surfaces are coated with metallic electrodes. A potential difference applied between the diaphragm and the chamber pulls the diaphragm toward the chamber surface progressively from the outer circumference toward the center. This zipping actuation reduces the volume available to the refrigerant gas, thereby increasing its pressure. A segmentation technique is proposed for analysis of the compressor by which the domain is divided into multiple segments for each of which the forces acting on the diaphragm are estimated. The pull-down voltage to completely zip each individual segment is thus obtained. The required voltage for obtaining a specific pressure rise in the chamber can thus be determined. Predictions from the model compare well with other simulation results from the literature, as well as to experimental measurements of the diaphragm displacement and chamber pressure rise in a custom-built setup.

Investigation of Structures of Microwave Microelectromechanical-System Switches by Taguchi Method

The optimal design of microwave microelectromechanical-system (MEMS) switches by the Taguchi method is presented. The structures of the switches are analyzed and optimized in terms of the effective stiffness constant, the maximum von Mises stress, and the natural frequency in order to improve the reliability and the performance of the MEMS switches. There are four factors, each of which has three levels in the Taguchi method for the MEMS switches. An L9(34) orthogonal array is used for the matrix experiments. The characteristics of the experiments are studied by the finite-element method and the analytical method. The responses of the signal-to-noise (S/N) ratios of the characteristics of the switches are investigated. The statistical analysis of variance (ANOVA) is used to interpret the experimental results and decide the significant factors. The final optimum setting, A1B3C1D2, predicts that the effective stiffness constant is 1.06 N/m, the maximum von Mises stress is 76.9 MPa, and the natural frequency is 29.331 kHz. The corresponding switching time is 34 µs, and the pull-down voltage is 9.8 V.