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In this paper the static and dynamic pull-in phenomenon of a fixed-fixed micro beam, considering the effects of residual stress, axial stress, damping coefficient, and Fringing field effects have statically and dynamically been analyzed. The nonlinear electromechanical coupled integro- differential equation governing the problem has been derived using variational principle and solved using a computer code based on Finite element method. The problem has been solved for various values of damping coefficients, residual and axial stresses, and various initial gaps between the micro beam and the substrate. The results showed that by increase in damping coefficient the dynamic pull-in voltage is also increased but this increase is continued up to a definite value of damping coefficient more than which, the dynamic pull-in voltage is constant and equal to the static one. The pull-in time is also determined for various damping coefficients and has been shown that with increasing the damping coefficient the pull-in time is increased.

cited By 1; Conference of 10th IEEE Nanotechnology Materials and Devices Conference, NMDC 2015 ; Conference Date: 12 September 2015 Through 16 September 2015; Conference Code:121065; International audience; New dielectric-engineering concept is developed intending a net improvement of the performance of dielectric layers under electrical stress. Instead of synthesis of new dielectric materials a new class of dielectric layers that gain their performance from design rather than from composition is established. Two kinds of nanostructured dielectric layers are presented here: (i) silicon oxynitride layers (SiOxNy:H) with gradual variation of their properties (discrete or continuous), and (ii) SiO2 layers with tailored interfaces; a single layer of silver nanoparticles (AgNPs) is embedded in the vicinity of the dielectric free surface. The nanostructured layers exhibit much shorter charge retention times and appear promising candidates for general applications where surface charging of dielectrics must be avoided, in particular for implementation in RF MEMS capacitive switches with electrostatic actuation.

We present the design, fabrication and characterization of an electrostatically actuated AFM probe. The probe consists of two cantilevers, a relatively long, stiff cantilever on which end a smaller and softer cantilever with a sharp tip is incorporated. The deflection of the small cantilever is controlled by an electrostatic gap-closing actuator, which is monolithically integrated on the cantilevers. A combination of a small and fast cantilever with an integrated electrostatic actuator allows for a high frequency operation and high speed AFM imaging. We have designed and fabricated a probe with the large cantilever having a stiffness of over 400 N/m and small cantilevers with a stiffness of up to 3.2 N/m and a resonance frequency up to 643 kHz. We have confirmed a proper operation of the probe using high-speed imaging (8 scan lines per second) in electrostatically driven tapping mode.

International audience; This paper introduces the tunneling current as a sensor to detect and control displacements of Micro and Nano Electromechanical Systems (MNEMS). Due to its extremely small magnitude, the tunneling current can not be used without an appropriate control strategy. A control methodology involving two feedback loops is proposed to control displacements with an accuracy of 40pm while also compensating the sensor drift. With this strategy, controlling displacements with an amplitude larger than one nanometer is possible, extending the predicted capabilities of tunneling current by the literature. The overall approach is a solution for control of macro to nano systems and may be embedded in positioning applications requiring a very high degree of accuracy.

Nowadays, various competitions between manufacturers take place in the field of MEMS (Micro- Electro-Mechanical Systems), due to the quest for continuous performance improvement in terms of miniaturisation, integration, costs effectiveness etc. This thesis is a step towards the development of IC-compatible bulk acoustic MEMS resonators. The main goal consists in validating the principle of electrostatic actuation of the thickness‒extensional acoustic waves into mono-crystalline substrates and also to explore the energy-trapping possibility provided by this mode. A novel single-port silicon structure fixed on a glass support was studied and analytically modelled to be implemented into a micro-fabrication process. The original models elaborated for a structure vibrating in both thickness‒extensional and flexural modes allowed the estimation of the electrical equivalent circuit parameters and of the static and dynamic mechanical displacements. A two-dimensional theoretical approach based on the dispersion curves estimation of a silicon plate was presented and the means to localize the acoustic energy in the central region of the structure were evaluated. By using the available micro-manufacturing techniques at the MIMENTO facility of the FEMTO-ST Institute, several runs were performed on silicon wafers. The resonators fundamental vibration frequencies range around 10 MHz for the thickness-extensional mode and around 70 KHz for the flexural mode. The electrical and mechanical characterisation results are thoroughly presented. The devices operating in flexural modes were successfully embedded into a customized Wienbridge oscillator design. Finally a gravimetric sensor application was demonstrated.; Le domaine des résonateurs MEMS (Micro-Electro-Mechanical Systems) est aujourd'hui le siège de diverses compétitions entre les producteurs afin d'améliorer les performances en terme de miniaturisation, intégrabilité, coûts de production etc. Ce travail de thèse s'inscrit dans un projet global de développement de résonateurs MEMS à ondes de volume compatibles avec la technologie des circuits intégrées. L'objectif est de valider le principe d'excitation des ondes acoustiques de volume en extension-compression par voie électrostatique dans des substrats monocristallins et aussi d'explorer les possibilités offertes par ces modes pour le confinement de l'énergie acoustique, technique plus largement exploitée dans le domaine des résonateurs à quartz que dans celui des MEMS. En ce sens, une nouvelle structure mono-port en silicium, fixée sur un support en verre, a été étudiée et modélisée analytiquement en vue de son implémentation dans une chaine de fabrication. Les modèles originaux développés dans ce cadre nous ont permis d'estimer les paramètres électriques du circuit équivalent, les déplacements mécaniques statique et dynamique propres au fonctionnement de la structure, autant en mode vibratoire d'extension-compression qu'en mode de flexion. Une étude théorique bidimensionnelle basée sur l'évaluation des courbes de dispersion d'une plaque en silicium a été menée afin d'évaluer les moyens de piégeage de l'énergie au centre de la structure fonctionnant en mode de volume. Tout en exploitant les microtechniques disponibles au sein de la Centrale MIMENTO de l'Institut FEMTO-ST, plusieurs séries de résonateurs ont été fabriquées sur substrat silicium pleine plaque. La fréquence fondamentale de vibration se situe aux alentours de 10 MHz pour le mode d'extension compression et de 70 kHz pour le mode de flexion. On détaille la caractérisation par voie mécanique et électrique. L'intégration des dispositifs fonctionnant en mode de flexion en boucle d'oscillation à l'aide d'un montage à base de point Wien est démontrée ainsi qu'une application de type capteur gravimétrique.

In this paper we present a method for closed-loop operation of pull-in time accelerometers. Accelerometers based on the measurement of the pull-in time of movable parallel-plates MEMS structures have already demonstrated very good resolution capabilities, with low requirements on the capacitive readout. However, open-loop operation delivers very low dynamic range and highly non-linear response. The closed-loop approach relies on electrostatic feedback using counter-actuation electrodes opposite to the pull-in direction and although the control algorithm used was very simple, the dynamic range has been effectively extended and the linearity improved., Fundação para a Ciência e a Tecnologia (FCT)

In this paper we investigate the influence of tilted electrostatic actuators on the imaging in electron microscopes. Previous studies have shown image deformation by electrostatic actuation in electron microscopes, and suggested a strong influence of the tilt angle on the deflection of the electron beam. Our model suggests an influence of 1 \mu m/$^\circ$ of the tilt angle on the amplitude of deflection. Preliminary experimental results indicate an influence of the angle on the amplitude of deflection, but the observed effect is two orders of magnitude smaller than simulations predict. However, there are still some variables we have not explored that might influence the strength of the influence of tilt.

In this paper we investigate the influence of tilted electrostatic actuators on the imaging in electron microscopes. Previous studies have shown image deformation by electrostatic actuation in electron microscopes, and suggested a strong influence of the tilt angle on the deflection of the electron beam. Our model suggests an influence of 1 \mu m/$^\circ$ of the tilt angle on the amplitude of deflection. Preliminary experimental results indicate an influence of the angle on the amplitude of deflection, but the observed effect is two orders of magnitude smaller than simulations predict. However, there are still some variables we have not explored that might influence the strength of the influence of tilt.

The detection of gravitational waves at frequencies below 10mHz requires a reference sensor of the spaceborne inertial system with unprecedented residual acceleration and an optoelectronic system able to detect exceptionally small deviations of space between two reference sensors several million kilometers apart. The test mass, used as a reflecting mirror of such a gravitational optoelectronic detector, is the reference sensor, and the inertial sensor front-end electronics are the electronic system necessary to sense the position of the test mass in the spacecraft and to actuate it in all degrees of freedom, except the main measurement axis used for gravitational wave detector. Due to the nature of the rising electronic noise at low frequency, it is particularly difficult to achieve the requirements below 1mHz, which is the major challenge in the electronic design. Therefore, a work covered by dissertation has been launched aiming to analyze and convert the top-level mission requirements into electronic requirements, define the main design drivers and related technological challenges in the field of capacitance measurement and electronic actuation, evaluate the design options, verify selected designs by building and testing the hardware and collect the acquired knowhow and lessons learned for flight hardware development and future research in this field.

A high fill-factor, dual-axis micromirror array with novel spring and actuator design is developed for high thermal load applications. Each pixel can attain an omnidirectional mechanical DC rotation angle of +/- 4 degrees.

In this paper we are investigating the potential to employ small devices in crucial areas with limited volumes in electron microscopes. We present the analysis of the electric fields that are present in an electrostatically actuated micro electro mechanical systems (MEMS) device. The electric fields are modeled using finite elements methods (FEM). Preliminary results are shown from scanning electron microscope (SEM) measurements of an electrostatically actuated two degrees of freedom (2DOF) nanometer precision table. From the FEM results the influence of the electric fields on an electron beam traversing the devices can be calculated. This influence is calculated to be a trajectory displacement in the order of tens of nanometers for typical acceleration voltages. SEM measurements show significant vibrations in the images of nonmovable parts of the devices when applying actuation voltages to the devices. This shows an effect of actuation on the detected electrons while imaging. Deflections up to 2.2 μm have been observed for a voltage of 80 Vpp. This deflection cannot be fully attributed to deflections of the incoming beam. Therefore we include in a qualitative analysis the trajectory of emitted secondary electrons that are detected.

In this paper we are investigating the potential to employ small devices in crucial areas with limited volumes in electron microscopes. We present the analysis of the electric fields that are present in an electrostatically actuated micro electro mechanical systems (MEMS) device. The electric fields are modeled using finite elements methods (FEM). Preliminary results are shown from scanning electron microscope (SEM) measurements of an electrostatically actuated two degrees of freedom (2DOF) nanometer precision table. From the FEM results the influence of the electric fields on an electron beam traversing the devices can be calculated. This influence is calculated to be a trajectory displacement in the order of tens of nanometers for typical acceleration voltages. SEM measurements show significant vibrations in the images of nonmovable parts of the devices when applying actuation voltages to the devices. This shows an effect of actuation on the detected electrons while imaging. Deflections up to 2.2 μm have been observed for a voltage of 80 Vpp. This deflection cannot be fully attributed to deflections of the incoming beam. Therefore we include in a qualitative analysis the trajectory of emitted secondary electrons that are detected.

The complexity of microsystems, their multidisciplinarity, the heterogeneity of materials and interfaces with the external environment makes difficult the assessment and control of reliability, which is indispensable for the exploitation of the several innovative opportunities that they offer. The approach we proposed, in this work, to predict the reliability of microsystems is based on the intensive use of modelling and simulation, in the use and environmental conditions of micro-system (mission profile), thus by combining the reliability evaluation in the design process: before undertaking any type of functional modelling VHDL-AMS, reliability objectives are expressed explicitly in the specification of the micro-system, as well as the most common performance goals. To support our work, we applied this approach for predicting the reliability for two types of microsystems: - Electro-thermal micro-actuators. - Capacitive RF MEMS switches.; La complexité des microsystèmes, leur multidisciplinarité, l'hétérogénéité des matériaux utilisés et les interfaces avec l'environnement extérieur rendent difficiles l'évaluation et la maîtrise de leur fiabilité indispensables pour l'exploitation des nombreuses possibilités innovantes qu'ils offrent. L'approche que nous avons proposée dans ce travail, afin de prédire la fiabilité des microsystèmes, se fonde sur l'usage intensif de la modélisation et de la simulation, dans les conditions d'usage du microsystème (profil de mission), en associant donc l'évaluation de la fiabilité à la démarche de conception : avant d'entreprendre une modélisation fonctionnelle de type VHDL-AMS, les objectifs de fiabilité sont exprimés explicitement dans le cahier des charges du microsystème, au même titre que les objectifs plus habituels de performances. Afin de supporter nos travaux, nous avons appliqué cette démarche de prédiction de la fiabilité sur deux types de microsystèmes : - des micro-actionneurs électrothermiques. - des commutateurs RF capacitifs à actionnement électrostatique.

This thesis describes the design, fabrication, and characterization of compact optical devices for sensing and switching applications. Our focus has been to realize the devices using CMOS-compatible fabrication processes. Particularly the silicon photonics fabrication platform, ePIXfab, has been used for this purpose.

The present work proposes to use the tunnel current as a sensor to manipulate an object with micrometric dimensions. The use of such a sensor is proposed as an alternative to optical sensors, commonly used to measure or control the position of objects at a micrometric or nanometric scale. This work shows that the tunnel current can be controlled simultaneously with an electrostatic actuator and a piezoelectric actuator to tackle difficulties relative to the reduction of scale, such as drifts or measurement noise. For that purpose, an experimental set-up has been built-up at the GIPSA-Lab in the framework of this PhD. A robust control strategy has been implemented in this set-up to control the position of a microcantilever with an accuracy below the ångström at a speed higher than several hundred of Hertz., Ce doctorat propose l'utilisation d'un capteur à courant tunnel pour manipuler un objet à dimensions microscopiques. L'utilisation de ce capteur est proposée comme une alternative aux capteurs optiques couramment utilisés en nanotechnologie pour caractériser des objets mobiles. De plus, dans un contexte de nanopositionnement, sa mise en oeuvre ne peut se faire sans l'application d'outils de commande. Nous avons démontré que l'utilisation du courant tunnel couplé à un actionnement électrostatique répond aux problématiques récentes dans le domaine du nanopositionnement (correction de dérives, augmentation conjointe de la rapidité de manipulation et de la précision). Pour cela, une plate forme a été construite dans le cadre de ce doctorat. Cette plateforme a pour but de permettre le contrôle de déplacements d'un micro objet sans le toucher par courant tunnel. En particulier, cette plateforme a permis de contrôler la position d'une micropoutre avec une précision de l'ordre de la dizaine de picomètres en milieu bruité.

Nowadays many consumer electronic devices are using small engines (micromotors). Thanks to technological innovation, the components can be imbedded into numerous portable systems. The key factors for a nomadic integration are: reduction of power consumption, reliability, durability and manufacturing cost. From the perspective of an always denser integration, conventional fabrication techniques of motors are reaching their limits (windings, size of the permanent magnet). The technologies developed for the micro-electronics (thin film processes) offer new possibilities to create microscopic size motors. The potential for innovation in this field being very wide, many new concepts are based on this technology. Lots of research centers are trying to find new principles of actuation to increase the overall efficiency of motors. With the challenge of replacing a small "classical" motor by a micromotor based on thin film technologies, the electrostatic actuation is going to have a great potential in the future. Many problems are related to the compatibility of both technologies in terms of coexistence. This is mainly due to problems of dimensions and associated tolerances. The challenge of this research was to propose a solution for the creation of a micromotor including the following concepts: usable mechanical interface between an outer gear and the mechanical output torque of the micromotor (about 0:5 µNm), moderate energy consumption, relatively small chip size in relation to the required performances and finally ability to be easily implemented in a mechanism (module). This thesis presents the different aspects of the concept, design, simulation, fabrication and characterization of a MEMS based motor using silicon micro-technologies. The micromotor is constituted of a fixed base (stator) with an electrostatic actuator (force generator), a rotor and a protective cover (encapsulation). The principle of the electrostatic actuation is based on a comb inter-digitized configuration. A first interface (ratchet system) was developed to allow for the conversion of the back and forth movement of the linear type actuator to a circular motion of the silicon rotor. A challenge was to create an actuator able to deliver an electrostatic force of 500 µN with a applied potential of 40 V. To obtain this force, the actuator itself has an active area of over 10 mm2. The first concept has two large actuators representing 60% of the total area of the stator. In the second concept, the occupied area of the three actuators represents 40 % of the total area of the stator. Two systems were created during this work, based on the same principles of actuation and of actuator/rotor interfacing. The first system uses a crank mechanism to interface the silicon rotor and a metallic pinion. The encapsulation was achieved via a metal support on which a plastic lid was fastened. These two pieces were fabricated by conventional machining (milling) techniques. The micromotor module was made by assembling the different components. The second system was made based on a direct interface type (direct link between internal teeth of the silicon rotor and outer teeth of a metallic gear). The encapsulation concept uses only micro-technologies. The cover was made of a glass substrate on which a silicon spacer was bonded (anodic bonding process). The motor module was then achieved by assembling a silicon base (stator), a silicon rotor and a silicon/glass cover. In accordance with the specifications, the obtained results are very promising. The electrostatic force generated by the actuator is in the order of few hundreds of micronewton. The power consumption is in the order of few microwatts. Many innovative concepts have been studied and manufactured. Some of those have been patented, showing the interest of these new ideas. Experiments have demonstrated the functionality of a MEMS engine.

Integrated optical switches using mechano-optical sensing are gaining more attention in many fields due to their fast switching speed, large bandwidth and compact devices. In this paper, a micromachined electrostatically actuated metal plate to sense the evanescent field above the waveguide is presented. The feasibility of MEMS based light weight mechanical plates to achieve fast switching is evaluated. With decreasing distance between the suspended plate and the substrate it gets more difficult to control the gap due to forces resulting from parasitic charging and the Casimir effect. Measurement of the Casimir force between parallel plates at sub-micron distance is also cumbersome. A methodology to measure the Casimir force between parallel plates is presented here. The prime objective of this research is to come up with an ultra fast optical switch using parallel plates and also to measure the Casimir force between them.

This dissertation is concerned with an analytical modelling and optimization of electrostatic membrane-based actuators. An analytical model of a thin, perfectly clamped, silicon membrane bending described with Lagrange/Newton equation for small deflections is presented taking into account parasitic phenomena like residual stress and initial deflection of a membrane. Responses for uniform pressure are obtained with Galerkin method and are studied in order to describe the membrane's behaviour with a reduced model. Both models are analyzed in the case of electrostatic actuation and are compared in terms of precision, range of use, calculation time and easiness of use in the optimization process. The reduced model is then corrected to be fully applicable for hydrostatic and electrostatic actuation without significant precision loss and is compared with FEM simulations performed with ANSYS®. Obtained results allow defining the model advantages and disadvantages. Next, the analytical model is used to determine the influence of input parameters on actuator behaviour and to perform an optimization phase for various applications. Furthermore, statistical simulations are presented which are useful in the estimation of the influence of parameters dispersion, resulting for example from the technological process, on the device behaviour. All simulations are performed using dedicated tools written in MATLAB®. Finally, the fabrication and the characterization of test structures performed in LAAS-CNRS are described which allows the validation of the developed analytical model.; Résumé. Ce mémoire concerne la modélisation analytique et l'optimisation d'actionneurs électrostatique basés sur une membrane. Le modèle analytique de fléchissement de la membrane mince de silicium, parfaitement encastrée, décrit par l'équation Lagrange/Newton pour les petites déflexions est présentée en prenant sur compte des phénomènes comme les contraintes résiduelles et les déflexions initiales de la membrane. Les réponses pour la pression uniforme sont obtenues grâce à la méthode de Galerkin et sont étudiées pour décrire le comportement de la membrane avec un modèle réduit. Les deux modèles sont analysés pour l'actionnement électrostatique et sont comparés sur le plan de la précision, le gamme d'usage, le temps des calculs et le facilité d'usage en phase d'optimisation. Puis, le modèle réduit est corrigé pour être complètement applicable pour un actionnement hydrostatique et électrostatique sans perte de précision et est comparé avec la simulation FEM réalisée dans l'ANSYS®. Les résultats obtenus permettent de déterminer les avantages et les inconvénients du modèle. En suite, le modèle analytique est utilisé pour développer un outil d'optimisation et de statistique sous MATLAB®. Ce dernier permet d'estimer l'influence de la dispersion des paramètres technologiques sur le comportement des actionneurs. Finalement la fabrication et la caractérisation de structures de tests ont été réalisées au LAAS-CNRS et ont permis la validation du modèle analytique.

In Chapter I, the fundamental electronic properties of two-dimensional (2D) graphene and one-dimensional (1D) carbon nanotubes are discussed, along with the carbon nanotube single-electron transistors (SETs). In addition to nanotubes' extraordinary electronic properties, the phenomena of phonon transport in carbon nanotubes are also notable. In Chapter II, we discuss our experiments probing the thermal properties of multi-walled carbon nanotubes. We exploit the specific breakdown temperature under a large current, which provides an effective thermometer, in conjunction with the known power input to measure the thermal conductivity of the nanotubes. Our results reveal the exceptional micron-scale phonon mean free path at temperatures approaching 900K, and we demonstrate the first evidence for ballistic phonon propagation in nanotubes, reaching a regime where the thermal conductance of nanotubes is limited only by fundamental quantum mechanical limits imposed by their 1D nature. Moreover, the combination of remarkable electrical and mechanical properties makes carbon nanotubes a highly promising candidate for nanoelectromechanical systems (NEMS). In Chapter III, we investigate using doubly clamped suspended single-walled carbon nanotubes as nanomechanical resonators at cryogenic temperatures. Their intrinsic single-electron transistor behavior provides a mixing mechanism to self-detect their motion based on their capacitance to a nearby gate electrode. We exploit our devices to attain an ultrasensitive mass sensor, realizing atomic-scale mass sensing. Finally, in Chapter IV, nanoelectromechanical switches based on using multi-walled carbon nanotubes as nanoscale linear bearings are discussed. First we demonstrate the preparation of the initial OFF state by using electrical breakdown to create gaps in a free-standing MWNT device, while subsequently the ON state is actuated with electrical forces and undergoes linear bearing motion that telescopes the inner shells to bridge the gaps. The switching cycle can be performed in double-walled nanotube devices by restoring the insulating OFF state with a controllable gate voltage. These tubular switches can potentially serve as nonvolatile memory or logic gate elements.

This work is focused on the design, fabrication, and characterization of silicon laterally resonant microcantilevers for measuring absolute pressure. The authors have demonstrated the integration of resonance electrostatic actuation and capacitive readout with a microstructure based on a couple of electrodes and an external amplifier. The microcantilevers have been fabricated with a standard silicon on insulator micromachining process. The characterization method is based on measuring the current at the third harmonic of the excitation frequency flowing through the time-varying cantilever-based capacitor. The variation in resonance response of microcantilevers has been investigated as a function of pressure (10−2−105 Pa), both in terms of resonance frequency and quality factor. Theoretical models and experimental data show very good agreement. The microstructure behavior demonstrates the feasibility of an absolute pressure sensor working over a six-decade range with integrated electrical actuation and rea...

International audience; A closed-loop control approach for the dynamic shaping of a microbeam by electrostatic actuation is described. Starting from a desired displacements reference vector of N small segments of the beam (representing the approximation of the continuous case), n controllers (n is the number of considered modes) output the stresses that must be distributed throughout the beam, on the N actuators. Because this reference may vary with time, the controllers are designed so that they accomplish good response dynamics, as well as performance and robustness specifications. The innovation in this method is that we control the dynamic coefficients associated to the modes of the microbeam and not directly the physical displacements in each small segment, which reduces the number of correctors from N to the number of n modes to control.

The first objective of this dissertation is to present hybrid numerical-analytical approaches and reduced-order models to simulate microelectromechanical systems (MEMS) in multi-physics fields. These include electric actuation (AC and DC), squeeze-film damping, thermoelastic damping, and structural forces. The second objective is to investigate MEMS phenomena, such as squeeze-film damping and dynamic pull-in, and use the latter to design a novel RF-MEMS switch. In the first part of the dissertation, we introduce a new approach to the modeling and simulation of flexible microstructures under the coupled effects of squeeze-film damping, electrostatic actuation, and mechanical forces. The new approach utilizes the compressible Reynolds equation coupled with the equation governing the plate deflection. The model accounts for the slip condition of the flow at very low pressures. Perturbation methods are used to derive an analytical expression for the pressure distribution in terms of the structural mode shapes. This expression is substituted into the plate equation, which is solved in turn using a finite-element method for the structural mode shapes, the pressure distributions, the natural frequencies, and the quality factors. We apply the new approach to a variety of rectangular and circular plates and present the final expressions for the pressure distributions and quality factors. We extend the approach to microplates actuated by large electrostatic forces. For this case, we present a low-order model, which reduces significantly the cost of simulation. The model utilizes the nonlinear Euler-Bernoulli beam equation, the von K´arm´an plate equations, and the compressible Reynolds equation. The second topic of the dissertation is thermoelastic damping. We present a model and analytical expressions for thermoelastic damping in microplates. We solve the heat equation for the thermal flux across the microplate, in terms of the structural mode shapes, and hence decouple the thermal equation from the plate equation. We utilize a perturbation method to derive an analytical expression for the quality factor of a microplate with general boundary conditions under electrostatic loading and residual stresses in terms of its structural mode shapes. We present results for microplates with various boundary conditions. In the final part of the dissertation, we present a dynamic analysis and simulation of MEMS resonators and novel RF MEMS switches employing resonant microbeams. We first study microbeams excited near their fundamental natural frequencies (primary-resonance excitation). We investigate the dynamic pull-in instability and formulate safety criteria for the design of MEMS sensors and RF filters. We also utilize this phenomenon to design a low-voltage RF MEMS switch actuated with a combined DC and AC loading. Then, we simulate the dynamics of microbeams excited near half their fundamental natural frequencies (superharmonic excitation) and twice their fundamental natural frequencies (subharmonic excitation). For the superharmonic case, we present results showing the effect of varying the DC bias, the damping, and the AC excitation amplitude on the frequency-response curves. For the subharmonic case, we show that if the magnitude of the AC forcing exceeds the threshold activating the subharmonic resonance, all frequency-response curves will reach pull-in. Ph. D.

Since few years, the MEMS technology for microwave applications has grown up with the potential toimprove the circuit and device performances. Several components have been designed and demonstrate animportant reduction of loss and a higher linearity than their main counterparts: the semi-conductor components.This work investigates the MEMS switches design and their integration in tunable microwave systems.Thus, we first present a state of art of this MEMS technology and the MEMS microwave devices. Themicromachined switches operation is investigated. The main advantages, drawbacks and some applicationswhere these components could improve the performances are discussed.The second part of this work is dedicated to the mechanical and electromagnetical design of a DCcontact switch. The main objective of this work was to realise a reliable component which present goodperformances. The switch optimisation is presented and discussed with the corresponding mechanical andelectric measurements.The last part of this memory addresses the development of new switchable microwave circuit topologyincluding DC contact micro relays. Three applications are discussed; some tunable filters are developed with ahigh tuning in frequency (22% for the first one and 44% for the other). We also present how to preserve thedevice losses to a low level, and keep high the quality factor of these systems.Key words: MEMS, micromechanical devices, micro-relays, switches, electrostatic actuation, contact resistance,biasing network, reconfigurable systems, tunable filters, quality factor.; La technologie MEMS pour les applications hyperfréquences, s'est développée depuis quelques annéesavec pour objectif d'améliorer les performances des circuits et dispositifs microondes. De nombreux composantsont été développés, démontrant alors une importante réduction des pertes et une plus grande linéarité que leursprincipaux concurrents: les composants semi-conducteurs. Notre étude a porté donc sur la conception d'unmicro-commutateur et son intégration dans des circuits microondes reconfigurables.Dans un premier temps, nous présentons dans le manuscrit un état de l'art de la technologie MEMS etdes composants hyperfréquences qui en résultent. Le fonctionnement de commutateurs micromécaniques y estplus particulièrement étudié. Les principaux atouts et limitations sont également présentés avec quelquesdomaines d'application où ces composants peuvent contribuer à une amélioration de performances.La seconde partie de ces travaux est dédiée à la conception mécanique et électromagnétique d'un microcommutateurà contact ohmique. L'objectif de cette étude était de réaliser un composant fiable avec de bonnesperformances. L'optimisation de ce composant y est présentée, validée par des performances mécaniques etélectriques des dispositifs réalisés.La dernière partie de ces travaux concerne le développement de nouvelles topologies de circuitshyperfréquences reconfigurables équipés de micro-commutateurs à contact ohmique. Nous y présentons troisapplications dont la conception de filtres passe-bande avec un accord discret sur une large plage de fréquences(20% et 44% d'accord). Nous montrons également comment maintenir les pertes de ces dispositifs à un faibleniveau, en conservant les facteurs de qualité de ces composants reconfigurables à une valeur élevée.

Since few years, the MEMS technology for microwave applications has grown up with the potential toimprove the circuit and device performances. Several components have been designed and demonstrate animportant reduction of loss and a higher linearity than their main counterparts: the semi-conductor components.This work investigates the MEMS switches design and their integration in tunable microwave systems.Thus, we first present a state of art of this MEMS technology and the MEMS microwave devices. Themicromachined switches operation is investigated. The main advantages, drawbacks and some applicationswhere these components could improve the performances are discussed.The second part of this work is dedicated to the mechanical and electromagnetical design of a DCcontact switch. The main objective of this work was to realise a reliable component which present goodperformances. The switch optimisation is presented and discussed with the corresponding mechanical andelectric measurements.The last part of this memory addresses the development of new switchable microwave circuit topologyincluding DC contact micro relays. Three applications are discussed; some tunable filters are developed with ahigh tuning in frequency (22% for the first one and 44% for the other). We also present how to preserve thedevice losses to a low level, and keep high the quality factor of these systems.Key words: MEMS, micromechanical devices, micro-relays, switches, electrostatic actuation, contact resistance,biasing network, reconfigurable systems, tunable filters, quality factor., La technologie MEMS pour les applications hyperfréquences, s'est développée depuis quelques annéesavec pour objectif d'améliorer les performances des circuits et dispositifs microondes. De nombreux composantsont été développés, démontrant alors une importante réduction des pertes et une plus grande linéarité que leursprincipaux concurrents: les composants semi-conducteurs. Notre étude a porté donc sur la conception d'unmicro-commutateur et son intégration dans des circuits microondes reconfigurables.Dans un premier temps, nous présentons dans le manuscrit un état de l'art de la technologie MEMS etdes composants hyperfréquences qui en résultent. Le fonctionnement de commutateurs micromécaniques y estplus particulièrement étudié. Les principaux atouts et limitations sont également présentés avec quelquesdomaines d'application où ces composants peuvent contribuer à une amélioration de performances.La seconde partie de ces travaux est dédiée à la conception mécanique et électromagnétique d'un microcommutateurà contact ohmique. L'objectif de cette étude était de réaliser un composant fiable avec de bonnesperformances. L'optimisation de ce composant y est présentée, validée par des performances mécaniques etélectriques des dispositifs réalisés.La dernière partie de ces travaux concerne le développement de nouvelles topologies de circuitshyperfréquences reconfigurables équipés de micro-commutateurs à contact ohmique. Nous y présentons troisapplications dont la conception de filtres passe-bande avec un accord discret sur une large plage de fréquences(20% et 44% d'accord). Nous montrons également comment maintenir les pertes de ces dispositifs à un faibleniveau, en conservant les facteurs de qualité de ces composants reconfigurables à une valeur élevée.

Large electrostatic forces on a micromechanical capacitor plate can be obtained if the capacitor is tuned by using an inductor. Such an LC circuit can be used to control the position of a micromechanical capacitor plate over a large dynamic range. The pull-in phenomenon of capacitor plates does not occur because the LC drive is intrinsically stable. The LC drive can be implemented either by sweeping the frequency or the amplitude of the driving AC voltage. In both cases relatively good linearity can be obtained. It is found that the LC drive can tolerate large parasitic capacitances. Measurements done on a dual capacitive acceleration sensor verify the calculated results. A drive AC voltage rms amplitude of 10% of the DC pull-in voltage deflected the moving plate by about 60% of the nominal gap, limited only by a mechanical stopper.

The general study is dedicated to Wireless Sensor Networks. The idea is to associate micro-mechanical and microwave communication functions to exchange information between a remote sensor and a base station [1]. A specific part of this project concerns the conception, realisation, and characterisation of a passive microwave frequency shifter used for back-modulation around 2 GHz. The interesting point was to develop this function with an integrated silicon micro-mechanical rotating structure. The paper describes the prototype of the RF MEMS already developed in ESIEE laboratory. And we insist on the microwave measurements performed and the associated equivalent models.

We present a novel approach for hydrogen gas detection, based on palladium-coated micromechanical resonators. A sequence of thin film technniques allows the large-scale parallel fabrication of free-standing beams separated from a counter-electrode by a mesoscopic air gap. The readout principle has been confirmed. The device manifests a resonance frequency drop from 6.5 to 3 MHz as it is exposed to 4 % of H2 during 15s. The sensor responds within a few seconds to hydrogen gas and has a power consumption of about 10 pW. Preliminary results suggest that this technique can detect very minute concentrations.

This paper introduces a new actuation scheme for implementing Pulsed Digital Oscillators (PDOs) for electrostatic MEMS resonators. In this scheme, the capacitance of the device is biased with a voltage and it is periodically sampled. Short pulses of zero voltage are applied depending on the decisions taken by the oscillator loop. The paper discusses in detail the implementation of such electrostatic PDO (e-PDO) through a prototype and links the e-PDO to the conventional PDO theory. As an example, it is shown that with this actuation scheme it is possible to excite different resonances of the mechanical structure simply by changing the parameters of the feedback filter of the oscillator. Science Foundation Ireland