Failure Mechanisms of Capacitive MEMS RF Switch Contacts

Theoretical and graphical analysis of pull-in-voltage and figure of merit for a fixed-fixed capacitive Micro Electromechanical Systems (MEMS) switch is presented in this paper. MEMS switch consists of a thin electrode called bridge suspended over a central line and both ends of the bridge are fixed at the ground planes of a coplanar waveguide (CPW) structure. A thin layer of dielectric material is deposited between the bridge and centre conductor to avoid stiction and provide low impedance path between the electrodes. When an actuation voltage is applied between the electrodes, the metal bridge acquires pull in effect as it crosses one third of distance between them. In this study, we describe behavior of pull-in voltage and figure of merit (or capacitance ratio) of capacitive MEMS switch for five different dielectric materials. The effects of dielectric thicknesses are also considered to calculate the values of pull-in-voltage and capacitance ratio. This work shows that a reduced pull-in-voltage with increase in capacitance ratio can be achieved by using dielectric material of high dielectric constant above the central line of CPW.

Micro Electro Mechanical Systems (MEMS) Switches have become very popular in the Electronics industry and we need to carefully select beam material and structural parameters for reliability and better performance. A variety of materials can be used as beam material in RF MEMS switches. The cantilever beam is used to change the state of RF switch and for actuation is made mostly using aluminum, copper, gold, molybdenum, nickel and platinum. This paper investigates which is the best material to be used for beam for achieving lower pull-in voltage and also represents the effect of structural parameters such as air gap and beam thickness on the performance of MEMS series switches. Characterization of cantilever MEMS switches is carried out with 3D simulation using COMSOL Multiphysics based on Finite Element Method [FEM]. Reduction of Pull-in voltage can be done by carefully selecting beam material and it can further be reduced by decreasing air gap and beam thickness.

Linearity characteristics of capacitive tuners under large radio frequency (RF) power have become an important issue for today’s cellphone industry. The use of these devices as antenna tuners has become critically important due to the RF spectrum opening in the low-frequency range. Capacitive tuners connected directly to the antenna to change the RF voltage/current pattern and tune lower frequencies are subjected to suffer large voltage swings, especially in the isolation state or minimum capacitance. In this article, we analyze the effects of the large RF power or equivalent rms voltage to capacitive micro-electromechanical systems (MEMS) switches. The theoretical analysis combined with Coventor MEMS+ simulations will allow us to study the capacitance change and MEMS mechanical frequency response. This article evaluates two types of measurement setups to investigate the RF power effects on nominal capacitance and mechanical frequency response. Measurements up to 6 W were completed with two capacitive MEMS tuner products, confirming the modeling predictions and demonstrating the robustness of this technology under large RF power or voltage swings.

This article discusses anti-stiction coating for Microelectromechanical System (MEMS) switch using atomic force microscope (AFM). In the air, stiction occurs by the attractive force that arises from the capillary force generated from forming a liquid meniscus by water vapor across MEMS switch gap, and the switch does not function normally. We have measured adhesion force for Au and Pt surfaces between 10% and 85% relative humidity (RH), and compared it with that of SiO2, Si, and self-assembled monolayer (SAM) surfaces. Our measurements indicate that approximately 20 nm thick sputtered Au and Pt coatings are useful to prevent stiction of MEMS switch.

Microelectromechanical Systems (MEMS) for radio frequency (RF) applications or RF MEMS provides an opportunity to revolutionize the wireless communication. This paper describes the Performance of low loss Fixed-Fixed RF MEMS capacitive switch at higher frequencies. Many researchers focus on RF MEMS capacitive switch, which presents good performance at microwave frequencies. Modelling of RF MEMS devices is essential for design optimization and device reliability. One of the most important RF MEMS components is MEMS switch. A novel approach of designing the RF MEMS switch is presented here to obtain the better performance of the switch at higher frequency ranges from 0.1 to 40 GHz .The RF MEMS capacitive Fixed-Fixed switch exhibit lower losses, better reliability, and good performance at higher frequencies.

A novel, low loss, and highly reconfigurable matching network based on microelectromechanical system (MEMS) switches is proposed. MEMS switches are employed in an equivalent n-network to realize switchable short circuit stub terminations. The advantage of the proposed device is the minimal loading by MEMS switches in OFF states which results in delivering highly consistent performance over all configurations. The matching network is capable of matching varying impedances on both input and output terminals. Empirical design procedure and requirements for the proposed network is presented and the simulations and measurements for a prototype design are in close agreement.

Large apertures are of great benefit to applications that are prime powered limited as is found on aerostat and other airborne platforms. Electronically scanned array antennas are often proposed for these applications. However, increasing the aperture area with conventional array technology is met with prohibitive cost, weight, and prime power increases because of the dense spacing of phase shifters and/or active T/R modules. This paper discusses the recent development of RF MEMS (microelectromechanical system) switch technology and the use of these switches in a Radant lens configuration for arrays of approximately 10m2 at X-band. A proof-of-concept 0.4m2 MEMS electronically steerable antenna (ESA) containing 25,000 MEMS switches has been successfully designed fabricated and tested. The 0.4m2 MEMS ESA was then integrated with an AN/APG-67 radar system to form the MEMS demonstration radar system. The MEMS Demonstration Radar system successfully detected both airborne and ground moving targets during a series of extensive radar demonstrations. This is believed to be the first large scale employment of MEMS switches in a scanning antenna and radar system. The low-cost, lightweight and low power technology demonstrated here can enable weight and power constrained platforms with electronic steering.

Micro electro mechanical systems (MEMS) have experienced an explosive growth over the past few years driven mainly by its physical properties and its promising technological applications in many different fields, particularly in space and Radio Frequency (RF) systems. MEMS technology exhibits greater advantages over the existing semiconductor switches. In this paper, electro-thermal performances of a two hot arms actuator MEMS switch have been investigated. The switch is designed using CST Microwave Studio. Some mathematical equations have been developed to see the temperature distribution of the hot arms as voltage applied on it. Based on this thermal distribution, the linear thermal expansion of the hot arms and the air gap used in this switch is expressed mathematically. The developed equations have been solved and analyzed using the MATLAB software. This analysis shows that this MEMS switch has a wider range of linear operation and has extremely higher breakdown voltage.

The growing demand for artificial intelligence and high‐performance computing accelerates concerns over leakage power in highly integrated semiconductor systems. Power gating can reduce the leakage power by disconnecting idle logic blocks from the power supply through a sleep transistor. However, conventional metal‐oxide‐semiconductor field‐effect transistor‐based sleep transistors exhibit significant leakage currents and area overhead. As promising alternatives for power gating devices, microelectromechanical systems (MEMS) switches have gained significant attention due to their near‐zero off‐state leakage current. Nevertheless, their practical use in power gating has been limited by a fundamental trade‐off between low on‐resistance and fast switching time. This study demonstrates that extreme minimization of the air gap is the key to simultaneously reducing on‐resistance and switching time. By introducing a 20 nm nano air gap and high‐stiffness structural design, we realize—for the first time—a MEMS switch that combines ultra‐low on‐resistance (0.95 Ω) with ultra‐fast switching time (30 ns), while maintaining off‐state leakage below 100 fA. All fabrication processes remain within the back‐end‐of‐line thermal budget, enabling monolithic 3D integration with minimal area overhead. These results establish nano gap MEMS switches as strong candidates for power gating in next generation low‐power semiconductor systems.

We report a novel pull-up type radio frequency (RF) microelectromechanical system (MEMS) switch with no elastic deformation of the cantilever involved in the actuation. At a voltage of 4.5V, reliable actuations are achieved such that the movable lower contact pad is pulled up by the electrostatic force to make contact with the upper pad. At a frequency of 50GHz, an insertion loss of 0.5dB, a return loss of 12.4dB, and an isolation of 55dB are obtained from the switch. The measured transient times for switch-on and switch-off are 120 and 130ns, respectively. Compared to the MEMS switches reported thus far, the pull-up type switch shows the best switching speed and isolation characteristic at 50GHz.

PurposeTo evaluate the performance of micro‐electromechanical systems (MEMS) switches against PIN diodes for switching a dual‐tuned RF coil between 19F and 1H resonant frequencies for multi‐nuclear lung imaging.MethodsA four‐element fixed‐phase and amplitude transmit–receive RF coil was constructed to provide homogeneous excitation across the lungs, and to serve as a test system for various switching methods. The MR imaging and RF performance of the coil when switched between the 19F and 1H frequencies using MEMS switches, PIN diodes and hardwired configurations were compared.ResultsThe performance of the coil with MEMS or PIN diode switching was comparable in terms of RF measurements, transmit efficiency and image SNR on both 19F and 1H nuclei. When the coil was not switched to the resonance frequency of the respective nucleus being imaged, reductions in the transmit efficiency were observed of 32% at the 19F frequency and 12% at the 1H frequency. The coil provides transmit field homogeneity of ±12.9% at the 1H frequency and ±14.4% at the 19F frequency in phantoms representing the thorax with the air space of the lungs filled with perfluoropropane gas.ConclusionMEMS and PIN diodes were found to provide comparable performance in on‐state configuration, while MEMS were more robust in off‐state high‐powered operation (>1 kW), providing higher isolation and requiring a lower DC switching voltage than is needed for reverse biasing of PIN diodes. In addition, clear benefits of switching between the 19F and 1H resonances were demonstrated, despite the proximity of their Larmor frequencies.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Due to the emergence of high-capacity wavelength- division multiplexing transmission systems, new optical cross- connect (OXC) architectures that make a large number of fiber/wavelength counts to switch the signal in the optical domain are needed. Optical microelectromechanical system (MEMS) switches are regarded as the most promising optical switch technology to achieve such functionalities. In this paper, we propose a novel integrated multistage two-dimensional (2-D) MEMS optical switch design with Spanke-Benes architecture and compare it with the conventional crossbar architecture, the L-switching architecture, and Shuffle-Benes architecture. Our proposed architecture is very suitable for building large-port-count 2-D MEMS switches and achieves much better performance in terms of beam divergence loss, longest optical path, mirror radius, substrate size, port-to-port repeatability, and power consumption than the other three architectures. Furthermore, compared with the 2-D conventional crossbar switch commercially available now, the proposed architecture can save 50% mirrors, shorten 87.5% longest optical path, minify 65% mirror radius, and shrink 90% substrate size. </para>

Micro-electromechanical System (MEMS) is a batch fabricated (micro-fabricated) system that contains both electrical and mechanical components. The devices are known to be unstable in there performances due to reliability concerns, trapping mechanism in dielectric is one of the major cause for the reliability issue, modelling of these traps can help to improve stiction occurring in dielectric. With the help of first order kinetic equation it can be possible to determine number of traps. A Model is constructed to predict the amount of charge trapped into the silicon nitride (Si3N4) of the capacitive MEMS Switch.

In this paper, an analytical method of resonant frequency, tuning range, the effective relative dielectric constant, and characteristic impedance is proposed, which is for coplanar waveguide (CPW) resonator loaded by defected ground structure (DGS) and micro-electromechanical systems (MEMS) capacitors. The analytical solution is achieved by an employing equivalent method. The resonant frequency, tuning range, and effective relative dielectric constant are obtained by the analytical solution. For verifying the effectiveness of the proposed method, a CPW tunable bandstop filter (BSF) with DGS and MEMS capacitors is designed, simulated, and fabricated, results show good effectiveness of the proposed analysis method. By changing the height of the MEMS beam with the actuation voltage, the designed BSF can switch the center frequency among three states (i.e. 18.5 GHz, 18.2 GHz, 17.5 GHz, respectively), and fractional bandwidth is changed as well (i.e. 37.8%, 45.6%, 49.5%, respectively).

Microelectromechanical systems (MEMS) switches have a wide range of possible applications due to their promising working characteristics, but commercial success of these devices is limited by low reliability. In contrast with macroscopic electromechanical relays, MEMS switches typically develop a small contact force, which results in unstable and high contact resistance. In this paper we propose the design that ensures several times higher contact force in comparison with previously used structure. Enhancement of the force is achieved without increasing the footprint and operating voltage of the switch. The analytical calculation and finite element simulation of the working characteristics are performed. At the driving voltage of 100 V the modified switch provides the contact force as high as 130 µN, which is an order of magnitude higher than the force developed by the basic device.