1,720,963 research outputs found
Heat-Based Recovery Mechanism to Counteract Stiction of RF-MEMS Switches
No full textStiction of MEMS (MicroElectroMechanical System) switches for RF (Radio Frequency) applications is a critical issue as it may jeopardize temporarily or permanently the operability of such devices. In this work we present a novel mechanism to enable the self-recovery of RF-MEMS switches in case of stiction. It is based on the application of a restoring force on the stuck membrane, induced by the thermal stress due to self-heating of the switch itself. The heat is generated by a current driven through a high resistivity polysilicon serpentine housed underneath the anchoring points of the suspended switch. After a detailed theoretical analysis, we will report FEM-simulation results (Finite Element Method) describing the behaviour of the structure discussed in this paper
An Active Self-Recovery Mechanism to Restore the Operability of RF-MEMS Switches Affected by Stiction
No full textMicroElectroMechanical switches for Radio Frequency applications, namely RF-MEMS, have been demonstrated to exhibit remarkable performance, like very low-loss, high Q-Factor and good linearity, thus enabling the manufacturing of low-cost lumped elements (switches, variable capacitors and inductors) as well as of complex networks as phase shifters for antenna/radar applications, power dividers and switching units and matrices
Aspects of Mechanical Reliability for RF-MEMS Switches with Self-Recovery Mechanism to Counteract Stiction
No full textIn this work we discuss the operation of an active self-recovery mechanism, embedded within MEMS (MicroElectroMechanical Systems) switches for Radio Frequency (RF) applications, able to counteract the stiction induced by charge accumulation [1] and micro-welding formation [2]. Such a mechanism, based on the thermo-electric effect, allows for restoring the MEMS switch back to normal operation after a failure. This is done by means of two factors, namely, the entrapped charges dispersion speed-up [3] within the insulating layer between the electrodes, and the application of shear forces on the welding points, both induced by the heat. Preliminary experimental results, collected by a few fabricated MEMS switch samples, confirm the viability of the proposed approach
Una procedura per la stima degli effetti dell`incertezza di processo sulle prestazioni di dispositivi RF-MEMS
No full textL’utilizzo di dispositivi Micro-Elettro-Meccanici (MEMS) in sistemi a Radio Frequenza (RF) è da tempo oggetto di studio da parte della comunità scientifica internazionale al fine di progettare ricetrasmettitori radio riconfigurabili, ossia adattabili dinamicamente ai requisiti di diversi standard di comunicazione [1]. L’idea di realizzare componenti circuitali a parametri concentrati di tipo RFMEMS è motivato dall’alto fattore di merito, dalle basse perdite e dalla buone prestazioni in termini di linearità di condensatori variabili, induttori e micro-interruttori (switch) implementati in tali tecnologie. Tuttavia, la scarsa maturità delle tecniche per la realizzazione di dispositivi RF-MEMS fa sì che variazioni anche minime di alcuni passi del processo di fabbricazione portino ad alterazioni significative delle caratteristiche dei componenti, con un conseguente deterioramento delle loro prestazioni. Questi problemi sono ulteriormente aggravati dalla dimensione multifisica dei sistemi RF-MEMS, la cui ottimizzazione elettromeccanica ed elettromagnetica spesso richiede modelli assai sofisticati capaci di descrivere non solo il comportamento di una data classe di dispositivi, ma anche le non idealità dovute allo specifico processo tecnologico adottato per realizzarli. Ad esempio, è ben noto che piccole variazioni delle proprietà elastiche di uno strato di metallo sottile possono influenzare notevolmente le caratteristiche RF di condensatori variabili [2]. In questo contesto, i ricercatori dell’Unità di Trento, in stretta collaborazione con quelli del gruppo MemSRaD della Fondazione Bruno Kessler (FBK) di Trento e con il supporto del Dipartimento di Elettrofisica della Technische Universität München (TUM), hanno messo a punto una procedura sperimentale per stimare il valore efficace di alcuni dei parametri che maggiormente influenzano le prestazioni elettromeccaniche ed elettromagnetiche di strutture RF-MEMS. In particolare, l’attenzione dei ricercatori si è concentrata soprattutto sulla stima di quei parametri di progetto che sono particolarmente sensibili alle incertezze del processo tecnologico impiegato. La procedura proposta è stata validata sperimentalmente su un campione omogeneo di dispositivi RF-MEMS e pone le basi per estrarre i parametri efficaci legati alle proprietà dei materiali e non alla specifica geometria dei componenti considerati. Lo scopo ultimo è quello di fornire ai progettisti di dispositivi e reti RF-MEMS un insieme di valori che, una volta scelta la tecnologia da utilizzare, consenta loro di ottimizzare un certo layout ottenendo caratteristiche sperimentali il più possibile simili a quelle simulate in fase di progettazione
FEM Electromechanical Modelling of a MEMS Variable Capacitor for RF Applications
No full textAccurate modelling of the electromechanical behaviour of RF-MEMS devices is critical in order to predict their characteristics, and consequently how the design has to be optimized in order to overcome the trade-offs arising when dealing with specifications both in the mechanical and electrical/electromagnetic physical domains. In this work we present a complete approach to the simulation of RF-MEMS devices based on FEM (Finite Element Method) simulations performed in ANSYSTM Multiphysics
A Measurement Procedure of Technology-related Model Parameters for Enhanced RF-MEMS Design
No full textThe accurate design of Micro-Electro-Mechanical- Systems (MEMS) for Radio Frequency (RF) architectures (e.g., reconfigurable transceivers) relies on suitable models describing the static and, above all, the dynamic electromechanical and electromagnetic behaviour of moveable structures. Such models usually include multiple parameters, whose values depend on the adopted manufacturing technology, as well as the uncertainty sources affecting the process itself. As a consequence, measuring the technology-related model parameters of a given class of MEMS structures is essential to estimate and to reduce, at an early design stage, possible mismatches between simulation results and device performances. In order to address this issue, in this paper we describe a procedure to measure the parameters describing the behaviour of RF-MEMS switches that are most severely affected by residual mechanical stress and surface roughness. The validity of the proposed methodology is confirmed by the good accordance between simulation and experimental results
Contact Modeling of RF MEMS Switches Based On FEM Simulations
No full textThis paper presents an approach in modeling RF MEMS switches based on FEM simulations performed by means of ANSYSTM software. A two-steps simulation procedure will be introduced, consisting of a structural analysis involving contact elements and a coupled-domains analysis aiming at evaluating the combined effect of pressure, voltage and temperature. The key steps useful to perform both the kind of simulation will be highlighted
Anti-Stiction And Self-Recovery Active Mechanisms For High Reliability RF-MEMS Switches
No full textReliability of RF-MEMS devices is one of the main concerns of the engineers and scientists dealing with such type of devices. In particular, there are plenty of studies and investigations devoted to protection of devices from dierent kind of failures related to their operating conditions. The adhesion of movable parts of switches onto the actuation electrode, also referred to as stiction, due to accumulated charge or to micro-welding phenomenon, are the most common types of RF-MEMS failures. This work presents a novel effective heat-based mechanism that enables to release a stuck component. Such mechanism can be embedded within the switches of any topology and it has no influence on the normal behavior of the device
Experimental Investigation of an Embedded Heating Mechanism to Improve RF-MEMS Switches Reliability
No full textUp to date, the remarkable performances and characteristics of MEMS switches and lumped
components for Radio Frequency applications (i.e. RF-MEMS) have been demonstrated by several
Authors . On the other hand, the reliability of such a technology still has to be fully addressed
in order to enable a successful penetration of RF-MEMS technology into the market. Reliability
of MEMS/RF-MEMS involves several physical phenomena that can jeopardize their normal
operation as well as the stability of their characteristic vs. time. Among such different effects,
the authors believe that one of the most important source of malfunctioning is the stiction (i.e. the
switch remains stuck in the actuated position when the controlling bias is removed) due to the
charge entrapment into the insulator layer and/or the formation of micro-welding. In order to
counteract stiction, the authors already presented an innovative RF-MEMS switch design
employing an active restoring mechanism, based on an high-resistivity serpentine heater (see Figure
1) to bring it back to its normal operability when stiction occurs. In this work we report on the
experimental testing recently performed on such test structures employing the active mechanism,
fabricated in the FBK RF-MEMS technology. Firstly we used the Laser Doppler Vibrometer (LDV)
integrated into a Polytec MSA-500 optical profilometer to verify the effectiveness of the heating
mechanism to induce a movement of the suspended bridge
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