MEMS based mechanical switches are seen to be the likely replacements for CMOS based switches due to the several advantages that these mechanical switches have over CMOS switches. Mechanical switches can be used in systems under extreme conditions and also provide more reliability and cause less power loss. A major problem with mechanical switches is bouncing. Bouncing is an undesirable characteristic which increases the switching time and causes damage to the switch structure affecting the overall switch life. This thesis proposes a new switch design that may be used to mitigate bouncing by using two voltage sources using a double electrode configuration. The effect of many switch’s tunable parameters is also discussed and an effective tuning technique is also provided. The results are compared to the current control schemes in literature and show that the double electrode scheme is a viable control option.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Reconfigurable patch antenna integrated with RF mircoelectromechanical system (MEMS) switches is presented in this paper. The proposed antenna radiates circularly polarized wave at selectable dual frequencies (4.7 GHz and 7.5GHz) of high frequency ratio (1.6:1). The switches are incorporated into the diagonally-fed square patch for controlling the operation frequency, and a rectangular stub attached to the edge of the patch acts as the perturbation to produce the circular polarization. Gain of proposed antenna is 5 - 6dBi, and axial ratio satisfies 3dB criterion at both operating frequencies. The switches are monolithically integrated on quartz substrate. The antenna can be used in applications requiring frequency diversity of remarkable high frequency ratio.

No description available.

This thesis presents the theory, design, fabrication, and measurement results of novel reconfigurable impedance tuner, phase shifter, and vector modulators using the RF MEMS technology. The presented circuits are based on triple stub topology, and it is shown both theoretically and experimentally in this thesis that it is possible to control the insertion phase and amplitude of the input signal simultaneously using this topology. The presented circuits are implemented using an in-house, surface micromachining fabrication process developed at METU, namely METU RF MEMS Fabrication Process, which is implemented using six masks on quartz substrates. The RF MEMS impedance tuner is designed to operate in 6-20 GHz frequency band, and it covers the Smith Chart with 1331 impedance points. The measurement results of 729 impedance points of the fabricated impedance tuner show that a wide Smith Chart coverage is obtained in the entire band. The RF MEMS phase shifter is designed to cover 0-360 degrees range 10 degree steps at 15 GHz center frequency. The measurement results of the fabricated phase shifter show that the average phase error is 1.7 degrees, the average insertion loss is -3.1 dB, and the average return loss is -19.3 dB for the measured 21 phase states. The phase shifter can also work up to 30 GHz and 40 GHz with average insertion losses of -5 dB and -8 dB, respectively. The designed RF MEMS vector modulator operates in 22.5-27.5 GHz band, and it has 3 amplitude and 8 phase states. The measurement results of the fabricated vector modulator show that the amplitude error is 0.5 dB, the phase error is 4 degrees, and the return loss is -15 dB on average among the 24 measured states at each of 22.5, 25, and 27.5 GHz frequencies.

Els serveis de telecomunicacions i sistemes radar estan migrant a freqüències mil•limètriques (MMW), on es disposa d 'una major amplada de banda i conseqüentment d'una major velocitat de transmissió de dades. Aquesta migració requereix de l'ús de diferents tecnologies amb capacitat d'operar a la banda de freqüències mil•limètriques (30 a 300 Ghz), i més concretament en les bandes Ka (26,5 - 40GHz), V (50 – 75GHz) i W (75 – 110GHz). En moltes aplicacions i sobretot en aquelles on l'antena forma part d'un dispositiu mòbil, es cerca poder utilitzar antenes planes, caracteritzades per tenir unes dimensions reduïdes i un baix cost de fabricació. El conjunt de requeriments es pot resumir en obtenir una antena amb capacitat de reconfigurabilitat i amb un baix nivell de pèrdues en cada una de les bandes de freqüència. Per tal d'afrontar aquests reptes, les dimensions de les antenes mil•limètriques, juntament amb els tipus de materials, toleràncies de fabricació i la capacitat de reconfigurabilitat ens porten a l'ús de processos de microfabricació. L'objectiu d'aquesta tesis doctoral és l'anàlisi dels conceptes mencionats, tipus de materials, geometries de línia de transmissió i interruptors, en el context de les freqüències mil•limètriques, així com la seva aplicació final en dissenys d'antenes compatibles amb els processos de microfabricació. Finalment, com a demostració s'han presentat dissenys específics utilitzables en tres aplicacions a freqüències mil•limètriques: Sistemes de Comunicació per Satèl•lit (SCS) a la banda Ka, Xarxes d'àrea personal inalàmbriques (WPAN) a la banda V i sistemes radar per l'automoció a la banda W. La primera part d'aquesta tesis consisteix en l'anàlisi d'algunes tecnologies circuitals a freqüències mil•limètriques. S'han presentat els materials més utilitzats a altes freqüències (Polytetrafluoroethylene or Teflon (PTFE), Quartz, Benzocyclobuten polymer (BCB) i Low Temperature Co-fired Ceramic (LTCC)) i s'han comparat en termes de permitivitat i tangent de pèrdues. També s'inclou un estudi de pèrdues a altes freqüències en les principals línies de transmissió (microstrip, stripline i CPW). Finalment, es presenta un resum dels interruptors RF-MEMS i es comparen amb els PIN diodes i els FET. En la segona part, es presenten diferents agrupacions d'antenes amb la capacitat de reconfigurar la polarització i la direcció d'apuntament. S'han dissenyat dos elements base reconfigurables en polarització: CPW Patch antena i 4-Qdime antena. La primera antena consisteix en un element singular amb interruptors RF-MEMS, dissenyada per operar a les bandes Ka i V. La segona antena consisteix en una arquitectura composta on la reconfigurabilitat en polarització s'obté mitjançant variant la fase d'alimentació de cada un dels quatre elements lineals. La fase és controlada mitjançant interruptors RF-MEMS ubicats en la xarxa de distribució. L'antena 4-Qdime s'ha dissenyat per operar en les bandes V i W. Ambdós elements base s'han utilitzat posteriorment pel disseny de dues agrupacions d'antenes amb capacitat de reconfigurar l'apuntament del feix principal. La reconfigurabilitat es dur a terme utilitzant desfasadors de fase d'1 bit. La part final de la tesis es centra en les toleràncies de fabricació i en els processo de microfabricació d'agrupacions d'antenes mil•limètriques. Les toleràncies de fabricació s'han estudiat en funció dels error d'amplitud i fase en cada element de l'agrupació, fixant-se en les pèrdues de guany, error d'apuntament, error en l'amplada de feix, errors en el nivell de lòbul secundari i en l'error en la relació axial. El procés de microfabricació de les diferents antenes dissenyades es presenta en detall. Els dissenys de l'antena CPW Patch reconfigurable en polarització i apuntament operant a les bandes Ka i V, s'han fabricat en la sala blanca del Cornell NanoScale Science & Technology Facility (CNF). Posteriorment, s'han caracteritzat l'aïllament i el temps de resposta dels interruptors RF-MEMS, i finalment, el coeficient de reflexió, el diagrama de radiació i la relació axial s'han mesurat a les bandes Ka i V per les antenes configurades en polarització lineal (LP) i circular (CP). / Telecommunication services and radar systems are migrating to Millimeter-wave (MMW) frequencies, where wider bandwidths are available. Such migration requires the use of different technologies with the capability to operate at the MMW frequency band (30 to 300GHz), and more specifically at Ka- (26.5 to 40GHz), V- (50 to 75GHz) and W-band (75 to 110GHz). For many applications and more concretely those where the antenna is part of a mobile device, it is targeted the use of planar antennas for their low profile and low fabrication cost. A wide variety of requirements is translated into a reconfiguration capability and low losses within each application frequency bandwidth. To deal with the mentioned challenges, the MMW antenna dimensions, together with the materials, fabrication tolerances and reconfigurability capability lead to microfabrication processes. The aim of this thesis is the analysis of the mentioned concepts, materials, transmission lines geometries and switches in the MMW frequencies context and their final application in antenna designs compatible with microfabrication. Finally, specific designs are presented as a demonstration for three MMW applications: Satellite Communication Systems (SCS) at Ka-band, Wireless Personal Area Network (WPAN) at V-band and Automotive Radar at W-band. The first part of this thesis consist to analyze some MMW circuit technologies. The four most used materials at MMW frequencies (Polytetrafluoroethylene or Teflon (PTFE), Quartz, Benzocyclobuten polymer (BCB) and Low Temperature Co-fired Ceramic (LTCC)) have been presented and compared in terms of permittivity (εr) and loss tangent (tanδ). An study of the main transmission lines attenuation (microstrip, stripline and CPW) at high frequencies is included. Finally, an overview of the RF-MEMS switches is presented in comparison with PIN diodes and FETS switches. The second part presents different polarization and beam pointing reconfigurable array antennas. Two polarization-reconfigurable base-elements have been designed: CPW Patch antenna and 4-Qdime antenna. The first consists of a single reconfigurable element with integrated RF-MEMS switches, designed to operate at Ka- and V-band. The second antenna presented in this thesis has a composed architecture where the polarization reconfigurability is obtained by switching the phase feeding for each of the four linear polarized elements in the feed network with RF-MEMS switches. The 4-Qdime antenna has been designed to operate at V- and W-band. The two base-elements have been used to design two beam pointing reconfigurable antenna arrays. Using phased array techniques, beamsteering is computed and implemented with 1-bit discrete phase-shifter. The final part of the thesis is focused into the fabrication tolerances and microfabrication process of Millimeter-wave antenna arrays. The fabrication tolerances have been studied as a function of the amplitude and phase errors presented at each elements array, focusing on the gain loss, beam pointing error, Half-Power Beamwidth (HPBW) error, sidelobe level error and axial ratio error. The microfabrication process for the designed antennas is presented in detail. Polarization- and pointing- reconfigurable CPW Patch antenna operating at Ka- and V- band have been fabricated in a clean-room facility at Cornell NanoScale Science & Technology Facility (CNF). The RF-MEMS switches isolation and time response have been characterized. Finally, the reflection coefficient, radiation pattern and axial ratio have been measured at Ka- and V-band for the fabricated antennas configured in Linear Polarization (LP) and Circular Polarization (CP).

This dissertation deals with the development of RF MEMS switches with novel materials and micromachining techniques for the RF and microwave applications. To enable the integration of RF and microwave components on CMOS grade silicon, finite ground coplanar waveguide transmission line on CMOS grade silicon wafer were first studied using micromachining techniques. In addition, several RF MEMS capacitive switches were developed with novel materials. A novel approach for fabricating low cost capacitive RF MEMS switches using directly photo-definable high dielectric constant metal oxides was developed, these switches exhibited significantly higher isolation and load capacitances as compared to comparable switches fabricated using a simple silicon nitride dielectric. The second RF MEMS switch developed is on a low cost, flexible liquid crystal polymer (LCP) substrate. Its very low water absorption (0.04%), low dielectric loss and multi-layer circuit capability make it very appealing for RF Systems-On-a-Package (SOP). Also, a tunable RF MEMS switch on a sapphire substrate with BST as dielectric material was developed, the BST has a very high dielectric constant (>300) making it very appealing for RF MEMS capacitive switches. The tunable dielectric constant of BST provides a possibility of making linearly tunable MEMS capacitor-switches. For the first time a capacitive tunable RF MEMS switch with a BST dielectric and its characterization and properties up to 40 GHz was presented. Dielectric charging is the main reliability issue for MEMS switch, temperature study of dielectric polarization effect of RF MEMS was investigated in this dissertation. Finally, integration of two reconfigurable RF circuits with RF MEMS switches were discussed, the first one is a reconfigurable dual frequency (14GHz and 35 GHz) antenna with double polarization using RF MEMS switches on a multi-layer LCP substrate; and the second one is a center frequency and bandwidth tunable filter with BST capacitors and RF MEMS switches on sapphire substrate.

This thesis presents realization of two shunt, capacitive contact RF MEMS switches and two RF MEMS SPDT switches for microwave and millimeter-wave applications, two zero-level package structures for RF MEMS switches and development trials of a BCB based zero level packaging process cycle. Two shunt, capacitive contact RF MEMS switches for 26 GHz and 12 GHz operating frequencies are designed, fabricated and consistencies between fabricated devices and designs are shown through RF measurements. For the switch design at 26 GHz and at the operating frequency, return loss in the upstate is measured to be 27.61 dB, insertion loss and isolation in the downstate is measured to be 0.21 dB and 27.16 dB, respectively. For the switch design at 12 GHz and at the operating frequency, return loss in the upstate is measured to be 38.69 dB, insertion loss and isolation in the downstate is measured to be 0.05 dB and 25.84 dB, respectively. Quite accurate circuit models have been obtained for both of the RF MEMS switches. Two RF MEMS SPDT switches, which utilize the shunt, capacitive contact switches as building blocks are designed through circuit simulations. These two designs are fabricated and their RF measurements have been completed. It is shown from circuit model simulations that, the performances of the fabricated devices and desired responses corresponded to each other. For the SPDT switch design at 26 GHz, return loss at the input port is measured to be 12 dB and insertion loss is measured to be 1.24 dB. For the SPDT switch design at 12 GHz, return loss at the input port is measured to be 5.6 dB and insertion loss is measured to be 0.49 dB. The reason behind the unexpectedly bad performances has been investigated and discovered. The bad performances were due to a common mistake in the layouts of both SPDT switches. These mistakes are corrected in the circuit models and expected performances are obtained. Two different zero-level package structures which use high-resistive Si wafers have been suggested and required design changes have been made on the RF MEMS shunt, capacitive contact switches and SPDT switches in order to minimize the package effects. For this purpose polygonal CPW transitions have been designed and integrated into the designs, followed by the necessary tunings in the switch structures for which EM and circuit simulations are utilized. For the suggested package structures to be produced, two possible process cycles have been studied. One of the process flows was based on KOH anisotropic Si etching and the other one was based on DRIE (Deep Reactive Ion Etching). Great progress has been achieved in the latter process cycle, however this process cycle still needs some more study and it could not be completed in the time required for this thesis study.

Cette thèse s'inscrit dans la continuité des études menées pour améliorer la fiabilité des relais MEMS ohmiques et comprendre les mécanismes de dégradation se produisant au niveau du contact électrique aux échelles micro et sub-micrométriques. Les deux premiers chapitres de ce manuscrit permettent d'établir l'état de l'art du domaine et de décrire les différentes techniques expérimentales utilisées afin de caractériser les mécanismes physiques se produisant lors de l'ouverture et la fermeture d'un relais MEMS sous courant. Le troisième chapitre étudie qualitativement et quantitativement le transfert de matière aux distances sub-micrométriques. L'utilisation d'un microscope à force atomique (AFM) permet d'identifier les paramètres clés, notamment la tension de contact à l'état ouvert et la vitesse de commutation. L'origine de ce transfert de matière est attribuée à des émissions de courant se produisant dans les derniers nanomètres avant la fermeture du contact. Un plasma métallique est également observé et caractérisé pendant les phases de commutations. Ces observations conduisent à l'élaboration d'un scénario permettant d'expliquer le transfert de matière à ces dimensions. Le quatrième chapitre se consacre en première partie à l'étude des rebonds lors de la fermeture du contact. On montre que des rebonds peuvent apparaître quelques µs après la fermeture du contact au cours des cycles. Ceux-ci semblent être des indicateurs de la fin de vie du composant. D'autres rebonds, liés aux forces électrostatiques de contact, sont également mis en évidence lors de fermetures à faibles vitesses (qq nm/s). L'importance de ces forces est néanmoins du second ordre et ces derniers rebonds n'interviennent pas directement dans la phase de fermeture d'un relais MEMS. L'étude de la quantification de la résistance de contact lors de l'ouverture du contact constitue la deuxième partie de ce dernier chapitre. La nature quantique de ce phénomène est mise en évidence dans deux dispositifs : un interrupteur MEMS et à l'aide d'un AFM. Il est notamment montré que ce phénomène est seulement observable pour des courants inférieurs à 100µA. Finalement, l'ensemble de ces travaux mènent à différentes recommandations, détaillées en conclusion, nécessaires pour assurer le bon fonctionnement des relais MEMS. / This thesis aims to improve the reliability of ohmic MEMS switches and focuses on the degradation mechanisms of the electrical contact at the micro and nano-scales. The two first chapters of the manuscript provide a state-of–the-art of MEMS switches and describe the different experimental techniques used to characterize the physical phenomena involved in the opening and closure of a MEMS switch under current (“hot switching actuation”). The third chapter studies qualitatively and quantitatively the material transfer at sub micrometer scale. An Atomic Force Microscope (AFM) is used to identify the main parameters involved in this phenomenon such as the opening contact voltage and the closing velocity. The origin of the material transfer is attributed to field emission in the last tens of nanometers before the contact closure. A metallic plasma is also observed and characterized during switching operations. According to the different observations, a scenario is suggested to explain material transfer at such small dimensions. The fourth chapter deals with dynamic observation during switching operations. First, bounces can be detected after a few millions of operations, they usually appear a few µs just after the first contact. Such bounces seem to be an early indicator of the lifetime of those devices. Other types of bounces related to the electrostatic contact force can be observed at very low closing velocity (a few nm/s). Nevertheless in a MEMS switch the closing and opening velocity is high enough to avoid such bounces. The second part of this chapter investigates the contact conductance quantization during the opening phase of a contact. We show that this phenomenon can be observed in a MEMS switch and with an AFM when the current is lower than 100µA. As a conclusion, several recommendations are provided to improve the reliability of MEMS switches.

This thesis presents development of microwave lumped elements for a specific surface-micromachining based technology, a self-contained mechanical characterization of fixed-fixed type beams and realization of a shunt, capacitive-contact RF MEMS switch for millimeter-wave applications. Interdigital capacitor, planar spiral inductor and microstrip patch lumped elements developed in this thesis are tailored for a surface-micromachining technology incorporating a single metallization layer, which allows an easy and low-cost fabrication process while permitting mass production. Utilizing these elements, a bandpass filter is fabricated monolithically with success, which exhibits a measured in-band return loss better than -20 dB and insertion loss of 1.2 dB, a pass-band located in S-band and a stop-band extending up to 20 GHz. Analytical derivations for deflection profile and spring constant of fixed-fixed beams are derived for constant distributed loads while taking axial effects into account. Having built experience with the mechanical domain, next, Finite Difference solution schemes are established for pre-pull-in and post-pull-in electrostatic actuation problems. Using the developed numerical tools / pull-in, release and zipping phenomena are investigated. In particular, semi-empirical expressions are developed for the pull-in voltage with associated errors not exceeding 3.7 % of FEA (Finite Element Analysis) results for typical configurations. The shunt, capacitive-contact RF MEMS switch is designed in electromagnetic and mechanical domains for Ka-band operation. Switches fabricated in the first process run could not meet the design specifications. After identifying sources of relevant discrepancies, a design modification is attempted and re-fabricated devices are operated successfully. In particular, measured OFF-state return and insertion losses better than -16.4 dB and 0.27 dB are attained in 1-40 GHz. By applying a 20-25V actuation, ON-state resonances are tuned precisely to 35 GHz with an optimum isolation level of 39 dB.

Afin d’améliorer la durée de vie des micro-relais MEMS ohmiques, plusieurs traitements de surface de films minces d’or sont réalisés pour augmenter leur dureté tout en conservant une résistance électrique de contact faible.Les revêtements ultrafins de ruthénium (20 à 100 nm) déposés sur l’or augmentent la dureté des surfaces de contact d’un facteur 15. L’implantation ionique de bore ou d’azote (3,5 ppm à 10 % atomique) à une profondeur de 100 nm dans le film mince d’or permet d’atteindre un gain en dureté de 75%. Le contrôle (AFM, EBSD et DRX) de la microstructure induite met en évidence le durcissement par solution solide par insertion. Mais au-delà de 1% atomique, les atomes d’azote quittent le réseau cristallin de l’or pour former des précipités de nitrure d’or.L’analyse AFM (rugosité et diamètre) des empreintes résiduelles (quelques μm²) réalisées par nano-indentation sphérique, imitant le cyclage et le fluage des surfaces de contact de ces MEMS, démontre l’apport de ces traitements de surface. De plus, leurs résistances électriques de contact, mesurées par nano-indentation instrumentée reproduisant un micro-contact identique à un dispositif réel, sont similaires à celle de l’or pur.La modélisation discrète mécanique du contact rugueux est ajustée à la mesure de la déformation mécanique de nano-rugosités en comparant les relevés topographiques réalisés par AFM avant et après nano-indentation sphérique. La comparaison entre la modélisation et la mesure de la résistance électrique de contact indique que pour les gammes de force utilisées dans les micro-relais MEMS (inférieure au mN), seule une fraction allant de 2% à 9% de la surface de contact réelle est conductrice. / Ohmic MEMS switches made by gold thin films are promising devices but their mechanical contacts are one of the critical concerns for enhancing reliability. For this reason, surface processes are investigated in this work to improve both mechanical and electrical contact resistance (ECR) of MEMS gold contacts. Ruthenium ultra-thin films (20 to 100 nm) deposited on a top of gold layer increase surface hardness by a factor of fifteen. In parallel, surface implantations of both boron (<10% atomic) or nitrogen (<0.1% atomic) into gold reveals a solid solution hardening by insertion, thus increasing the hardness of initial film by about 75% and 25%, respectively. Notably, above 0.1% atomic of nitrogen, atoms precipitate from the tetra or octahedral sites of gold inducing a decrease of hardness.Static and multi load/unload spherical nano-indentation are performed on treated gold thin films to simulate the mechanical actuation of ohmic MEMS switches. Analysis of residual imprints (about few µm²) from treated surface exhibits both minimal local deformation and adhesion forces that reduce stiction probability. In-situ measurement of ECR for treated gold by instrumented nano-indentation, reproducing the design of MEMS, is in the same range of pure gold-to-gold configuration.A new mechanical discrete model of rough contact is introduced, confronted and validated to the experimental mechanical surface deformation obtained by comparison of AFM images before and after spherical nano-indentation. An electrical discrete model is added and fitted to the ECR measurements. In ohmic MEMS switch load range (< 1 mN), the conductive area is found to be about 2% to 9% of the real contact area.