The use of optical input/output (I/O) interconnects, in addition to electrical I/Os, is a promising approach for achieving high-bandwidth, chip-to-board communications required for future high-performance gigascale chip-based systems. While numerous efforts are underway to investigate the integration of optoelectronics and silicon microelectronics, virtually no work has been reported relating to testing of such chips. The objective of this research is to explore methods that enable wafer-level testing of gigascale chips having electrical and optical I/O interconnects. A major challenge in achieving this is to develop probe modules which would allow high-precision, temporary interconnection of a multitude of electrical and optical I/Os, in a chip-size area, to automated test equipment. A probe module would need to do this in a rapid, step-and-repeat manner across all the chips on the wafer. In this work, two candidate probe modules were devised, batch-fabricated on Si using microfabrication techniques, and successfully demonstrated. The first probe module consists of compliant electrical probes (10^3 probes/cm^2) fabricated alongside grating-in-waveguide optical probes. The second module consists of micro-opto-electro-mechanical-systems (MOEMS)-based microsocket probes (10^4 probes/cm^2) to interface a chip with polymer pillar-based electrical and optical I/Os. High-density through-wafer interconnects are an essential attribute in both probe substrates for transferring electrical and optical signals to the substrate back-side. Fabrication and characterization of metal-clad, metal-filled, and polymer-filled through-wafer interconnects as well as process integration with probe substrate fabrication are described and numerous possible redistribution schemes are explicated. Chips with optical and electrical I/Os are an emerging technology, and one that test engineers are likely to encounter in the near future. The contributions of this thesis are to help understand and address the issues relating to joint electrical and optical testing during manufacturing.

This dissertation reports very novel solutions for the trimming and compensation of various parameters of silicon micromechanical resonators and resonator-arrays. Post-fabrication trimming of resonance frequency to a target value is facilitated by diffusing in a deposited thin metal layer into a Joule-heated silicon resonator. Up to ~400 kHz of trimming-up and trimming-down in a 100 MHz Silicon Bulk Acoustic Resonators (SiBARs) are demonstrated via gold and aluminum diffusion respectively. The dependence of the trimming range on the duration of Joule heating and value of current passed are presented and the possibility of extending the trimming range up to ~4 MHz is demonstrated. Passive temperature compensation techniques are developed to drastically reduce the temperature coefficient of frequency (TCF) of silicon resonators. The dependence of TCF on the charge carriers in silicon are extensively studied and exploited for the very first time to achieve temperature compensation. A charge surplus via degenerate doping using boron and aluminum is shown to reduce a starting TCF of -30 ppm/°C to -1.5 ppm/°C while a charge depletion effected by creating multiple pn-junctions reduces the TCF to -3 ppm/°C. Further, shear acoustic waves in silicon microresonators have also been identified to effect a TCF reduction and have been excited in a concave SiBAR (or CBAR) to exhibit a TCF that is 15 ppm/°C lesser than that of a conventional rectangular SiBAR. The study on quality factor (Q) sensitivity to the various crystallographic axis of transduction in silicon resonators show that the non-repeatability of Q across various fabrication batches are due to the minor angular misalignment of ≤ 0.5° during the photolithography processes. Preferred axes of transduction for minimal misalignment sensitivity are identified and novel low-loss resonator-array type performances are also reported from a single resonator while transduced along certain specific crystallographic axes. Details are presented on an unprecedented new technique to create and fill charge traps on the silicon resonator which allows the operation of the capacitive SiBARs without the application of any polarization voltages (Vp) for the first time, making them very attractive candidates for ultra-low-power oscillator and sensor applications. Finally, a fabrication process that integrates both the capacitive and piezoelectric actuation/sensing schemes in microresonators is developed and is shown to compensate for the parasitics in capacitive silicon resonators while maintaining their high-Q.

Nanotechnology offers great promise for the development of nanodevices. Hence it becomes important to study the mechanical behavior of nanostructures for their use in such systems. MEMS (Micro ElectroMechanical Systems) provide an effective and precise method for testing nanostructures. Consequently this study focuses on the development of a MEMS thermal nanotensile tester to investigate the mechanical behavior of one-dimensional nanostructures. Extensive characterization of these MEMS devices (structural, electrical and thermal behavior) was performed using experimental as well as finite element methods. Tensile testing of nanostructures requires manipulation of individual nanostructures on the MEMS device. The study involves the development of an efficient methodology for the manipulation of nanowires and nanobeams for nanoscale testing. Furthermore, two different sensing schemes for the developed devices, namely capacitive and resistive, have been extensively investigated and the advantages and various issues related to both have been discussed. Nanocrystalline (nc) Ni nanobeams (typical dimensions of 500 nm x 200 nm x 20 µm) have been tested to failure using the MEMS devices. Improvements in the design for the MEMS nanotensile tester have been suggested to significantly enhance the device performance and to resolve the various issues involved with nano scale tests. Differential capacitive sensing for stress-strain measurements has been suggested to improve the accuracy of strain measurements.

Hypersonic flow is both fascinating and intriguing mainly because of presence of strong entropy and viscous interactions in the flow field. Notwithstanding the tremendous advancements in numerical modeling in the last decade separated hypersonic flow still remains an area where considerable differences are observed between experiments and numerical results. Lack of reliable data base of surface static pressures with good spatial resolution in hypersonic separated flow field is one of the main motivations for the present study. The experiments in hypersonic shock tunnels has an advantage compared to wind tunnels for simulating the total energy content of the flow in addition to the Mach and Reynolds numbers. However the useful test time in shock tunnels is of the order of few milliseconds. Hence in shock tunnel experiments it is essential to have pressure measurement devices which has special features such as small in size, faster response time and the sensors in array form with improved spatial resolutions. Micro Electro Mechanical Systems (MEMS) is an emerging technology, which holds lot of promise in these types of applications. In view of the above requirement, MEMS based pressure sensor array was developed to measure the static pressure distribution. The study is comprised of two parts: one is on the development of MEMS based pressure sensor array, which can be used for hypersonic application and other is on experimental static pressure measurement using MEMS based sensors in separated hypersonic flow over a backward facing step model. Initially a static pressure sensor array with 25 sensors was developed. The static calibration of sensor array was carried out to characterize the sensor array for various characteristic parameters. The preliminary experimental study with cluster of 25 MEMS sensor array mounted on the flat plate did not provide reliable and repeatable results, but gave valuable inputs on the typical problems of using MEMS sensors in short duration hypersonic ground test facilities like shock tunnels. Incidentally, to the best of our knowledge this is first report on use of MEMS based pressure sensors in hypersonic shock tunnel. Later cluster of 5 sensor array was developed with improved electronic packaging and surface finish. The experiments were conducted with flat plate by mounting 5 sensor array shows good agreement in static pressure measurement compared with standard sensors. In the second part of the study a backward facing step model, which simulates the typical gasdynamic flow features associated with hypersonic flow separation is designed. Backward facing step model with step height of 3 mm was mounted with sensor array along the length of model. Just after the step, static pressure measurements were carried out with MEMS sensors. It is important to note that, in the space available in backward facing step model we could mount only one conventional Kulite pressure transducer. The experiments were conducted at Mach number of 6.3 and at stagnation enthalpy of 1.5 MJ/kg in hypersonic shock tunnel (HST-5) at IISc. Based on the static pressure measurement on backward facing step, the location of separation and reattachment points were clearly identified. The static pressure values show that reattachment of flow takes place at about 7 step heights. Numerical simulations were carried out using commercial CFD code, FLUENT for flat plate and backward facing step models to compliment the experiments. The experimental tests results match well with the illustrative numerical simulations results.

Microelectromechanical systems (MEMS) based artificial sensory hairs for flow sensing have been widely explored, but the processes involved in their fabrication are lithography intensive, making the process quite expensive and cumbersome. Most of these devices are also based on silicon MEMS, which makes the fabrication of out-of plane 3D flow sensors very challenging. This thesis aims to develop new fabrication technologies based on Polymer MEMS, with minimum dependence on lithography for the fabrication of piezoresistive 3D out-of-plane artificial sensory hairs for sensing of air flow. Moreover, the fabrication of a flexible sensor array is proposed and new materials are also explored for the sensing application. Soft lithography based approaches are first investigated for the fabrication of an all elastomer device that is tested in a bench top wind tunnel. Micromolding technologies allow for the mass fabrication of microstructures using a single, reusable mold master that is fabricated by SU-8 photolithography, reducing the need for repetitive processing. Polydimethylsiloxane (PDMS) is used as the device material and sputter deposited gold is used as both the piezoresistive as well as the electrode material for collection of device response. The fabrication results of PDMS to PDMS metal transfer micromolding (MTM) are shown and the limitations of the process are also discussed. A dissolving mold metal transfer micromolding process is then proposed and developed, which overcomes the limitations of the conventional MTM process pertinent to the present application. Testing results of devices fabricated using the dissolving mold process are discussed with emphasis on the role of micro-cr  acking as one failure mode in elastomeric devices with thin film metal electrodes. Finally, a laser microfabrication based approach using thin film Kapton as the device material and an electrically conductive carbon-black elastomer composite as the piezoresistor is proposed and demonstrated. Laminated sheets of thick and thin Kapton form the flexible substrate on which the conductive elastomer piezoresistors are stencil printed. Excimer laser ablation is used to make the micro-stencil as well as to release the Kapton cantilevers. The fluid-structure interaction is improved by the deposition of a thin film of silicon dioxide, which produces a stress-gradient induced curvature, strongly enhancing the device sensitivity. This new approach also enables the fabrication of backside interconnects, thereby addressing the commonly observed problem of flow intrusion while using conventional interconnection technologies like wire-bonding. Devices with varying dimensions of the sensing element are fabricated and the results presented, with smallest devices having a width of 400 microns and a length of 1.5 mm with flow sensitivities as high as 60 Ohms/m/s. Recommendations are also proposed for further optimization of the device.

Este trabalho descreve a seqüência de fabricação de uma microválvula piezoelétrica posicionada na saída de um microbocal sônico. A técnica usada para fabricar os microbocais foi o jateamento utilizando pó de alumina e o substrato usado foi de vidro. As microválvulas são atuadores fabricados com o polímero poli(fluoreto de vinilideno) (PVDF) que é um material piezoelétrico. Os microbocais têm um formato convergente-divergente com diâmetro na entrada de 1 mm e com diâmetro na garganta em cerca de 240 microns. O atuador foi fabricado no modo bimorfo (duas folhas do polímero coladas com polarização opostas) com dimensões de 3 mm de largura por 6 mm de comprimento. Ambas as folhas do polímero são recobertas por um filme condutor de 200 nm de espessura usados como eletrodos. Aplicando uma voltagem entre os eletrodos uma folha expande enquanto a outra contrai gerando um movimento vertical do atuador. O movimento vertical pode ser maior ou menor dependendo do valor da tensão aplicada. Os dispositivos foram testados usando uma linha de gás, aplicando tensões DC e AC nos eletrodos do atuador. Para controle, também foram realizadas medidas em bocais sem atuadores. No caso onde foram aplicadas tensões DC nos atuadores, a pressão de entrada foi constante de 266 Pa. Aplicando uma tensão de +300 V DC nos eletrodos, o atuador teve um movimento vertical na direção oposta ao do microbocal de 20 microns (movimento de abertura). Neste caso o fluxo de gás medido, quando a razão de pressão entre a entrada e a saída atingiu 0,5, foi de 150 cm3/min. Aplicando uma tensão de -300 V DC (o que significa um movimento vertical de fechamento de 13 microns), o fluxo de gás medido, quando a razão de pressão foi de 0,5, foi de 134 cm3/min. Assim, existe uma faixa de fluxo entre 134 cm3/min e 150 cm3/min que pode ser controlada através do atuador. Em uma das medidas onde se aplicou uma tensão AC (200 V com 5 Hz de freqüência), foi utilizada uma pressão de entrada 13300 Pa. Neste caso, para uma razão de pressão de 0,5, onde o bocal se encontrava blocado, foi observado um fluxo de 847 cm3/min. Considerando que o fluxo do bocal sem atuador, nas mesmas condições de medida foi de 614 cm3/min, concluímos que o dispositivo no modo AC funciona como uma microbomba. A relevância deste trabalho está a utilização do poli(fluoreto vinilideno) (PVDF) na fabricação de um atuador para uso como microválvula. Este material que ainda não havia sido testado para esta finalidade. A fabricação dos microbocais foi feita em um substrato de vidro usando a técnica de jateamento também é inédita. Esta técnica é bastante usada na fabricação de microestruturas na superfície do vidro. Mas nunca tinha sido usada para a fabricação de microbocais que são canais em formato cônico que atravessam o substrato. / This work describes the fabrication and test of a microvalve integrated in a micronozzle. The technique used to fabricate the micronozzles was powder blasting using aluminum oxide powder and glass as substrate. The microvalves are actuators made from PVDF (poli(vinylidene fluoride)), that is a piezoelectric polymer. The micronozzles have convergent-divergent shape with diameter of 1mm at the entrance and throat around 240µm. The actuators were fabricated as a bimorph structure (two piezoelectric sheets were clamped together with opposite polarization) with dimensions 3 mm width and 6 mm length. Both sheets are recovered with a conductive thin film with 200 nm of thickness used as electrodes. Applying voltage between the electrodes one sheet expands while the other contracts and this generate a vertical movement to the entire actuator. If the voltage is changed, this movement can be higher or lower. The devices were tested in a gas line applying DC and AC voltages between the actuator\'s electrodes. Measurements were also realized using a micronozzle without actuator, for control. In the case where DC voltage was applied between the actuators electrodes, the inlet pressure was kept constant in 266 Pa. Applying +300V DC voltage between the electrodes, the actuator moved 20µm vertically in the opposite direction of the micronozzle (it opened). In this case the volume flux rate, for a pressure ratio (outlet / inlet) of 0.5, was 150 cm3/min. Applying -300V DC between the electrodes (that means it closed 13 microns in the micronozzle direction), for a pressure ratio of 0.5, the volume flux rate was 134 cm3/min. With these results, we conclude that it is possible to control the flow through the device in the range between 134 and 150 cm3/min. Flow measurements were also performed applying AC voltage (200V AC with frequency of 5 Hz) between the actuator electrodes and with the inlet pressure kept constant in 13300 Pa. In this case, with a pressure ratio (outlet / inlet) of 0.5, blocking the micronozzle, the flow rate measured was 847 cm3/min. Considering that the flow rate measured for the micronozzle without actuator was 614 cm3/min, in the same measurement conditions, we concluded that the device, in AC mode, was working as a micropump. The relevance of this work was the use of the poly(vinylidene) (PVDF) in the fabrication of the actuators and use it as a microvalve. The micronozzles were fabricated in a glass substrate using the powder blasting technique that was also new.

There are many ways in which the surrounding media, such as air between an oscillating MEMS structure and a fixed substrate, can affect the dynamic response of a MEMS transducer. Some of these effects involve dissipation while others involve energy transfer. Transverse oscillations of a planar structure can cause a lateral air flow in small gaps that results in pressure gradients. The forces due to the built–up pressure are always against the vibration of the structure and have characteristics of damper and stiffener. In this work, we study the squeeze film phenomenon due to the interaction between the air–film and the structure in the presence of restrictive flow boundary conditions. It is known that the squeeze film damping due to the air trapped between the oscillating MEMS structure and the fixed substrate often contributes to maximum energy dissipation. We carry out an analysis to estimate damping and stiffness in cases with restrictive flow boundaries in dynamic MEMS devices. While the studies reported in the present work address fluid flow damping with restrictive flow boundaries, the analysis of air-flow shows another important phenomenon of enhanced air-spring stiffness. This study is discussed separately in the context of spring stiffening behavior in MEMS devices exhibiting squeeze film phenomenon. First a theoretical framework for modeling squeeze film flow is established and this is followed with analytical and numerical solutions of problems involving squeeze film phenomenon. Modeling of squeeze film effects under different flow conditions is carried out using Reynold’s equation. The problem of squeeze film damping in MEMS transducers is more involved due to the complexities arising from different boundary conditions of the fluid flow. In particular, we focus our attention on estimation of damping in restricted flow boundaries such as only one side vented and no side vented passive boundary conditions. Damping coefficient for these cases are extracted when the fluid is subjected to an input velocity profile according to a specific mode shape at a given frequency of oscillation. We also explain the squeeze film flow in restricted boundaries by introducing the concept of passive and active boundary conditions and analyzing the pressure gradients which are related to the compressibility of the air in the cavity. Passive boundary conditions is imposed by specifying the free flow or no flow along one of the edges of the cavity, whereas, active boundary condition is imposed by the velocity profile being specified at the interface of the cavity with the oscillating structure. Some micromechanical structures, such as pressure sensors and ultrasound transducers use fully restricted or closed boundaries where the damping for such cases, even if small, is very important for the determination of the Q–factor of these devices. Our goal here is to understand damping due to flow in such constrained spaces. Using computational fluid dynamics (ANSYS–FLOTRAN), the case of fully restricted boundaries is studied in detail to study the effect of important parameters which determines the fluid damping, such as flow length of the cavity, air–gap height, frequency of oscillations and the operating pressure in the cavity. A simulation strategy is developed using macros programming which overcomes some of the limitations of the existing techniques and proves useful in imposing a non–uniform velocity and the extraction of damping coefficient corresponding to the flexibility of the structure in specific oscillation modes. Rarefaction effects are also accounted for in the FEM model by introducing the flow rate coefficient, or, alternatively using the concept of effective viscosity. The analysis carried out for the fully restricted case is motivated by the analytical modeling of squeeze film phenomenon for a wide range of different restricted boundaries, and analyzing the resulting pressure gradient patterns. We show that significant damping exists even in fully restricted boundaries due to lateral viscous flow. This is contrary to known reported results, which neglect damping in such cases. The result indicates that in fully restrictive fluid flow boundaries or in a closed cavity, air damping cannot be neglected at lower oscillation frequencies and large flow length to air-gap ratio if the active boundary has a non-uniform velocity profile. Analysis of air-flow in the case of restricted flow boundaries shows another important phenomenon of enhanced air-spring stiffness. It is found that fluid film stiffness has a nonlinear dependence on various parameters such as air-gap to length ratio, fluid flow boundary conditions and the frequency of oscillation. We carry out analysis to obtain the dynamic response of MEMS devices where it is significantly affected by the frequency dependent stiffness component of the squeeze film. We show these effects by introducing frequency dependent stiffness in the equation of motion, and taking examples of fluid boundary conditions with varying restriction on flow conditions. The stiffness interaction between the fluid and the structure is shown to depend critically on stiffness ratios, and the cut-off frequency. It is also inferred that for a given air–gap to flow length ratio, the spring behaviour of the air is independent of the flow boundary conditions at very high oscillation frequencies. Hence, we limit our focus on studying the effect of fluid stiffness in the regime where it is not fully compressible. For non-resonant devices, this study finds its utility in tuning the operating frequency range while for resonant devices it can be useful to predict the exact response. We show that it is possible to design or tune the operating frequency range or shift the resonance of the system by appropriate selection of the fluid flow boundary conditions. The emphasis of the present work has been toward studying the effect of squeeze film flow on dynamic response of MEMS structures with restrictive flow boundary conditions. Estimation of energy dissipation due to viscous flow cannot be ignored in the design of MEMS which comprise of restricted flow boundaries. We also remark that modeling of a system with squeeze film flow of the trapped air in terms of frequency independent parameters, viz. damping and stiffness coefficient, is unlikely to be very accurate and may be of limited utility in specific cases. Although the central interest in studying squeeze film phenomenon is on the damping characteristics because of their direct bearing on energy dissipation or Q–factor of a MEMS device, the elastic behaviour of the film also deserves attention while considering restrictive flow boundary conditions.

No description available.

No description available.

Avec l'apparition de nouveaux standards, les nouveaux systèmes de télécommunication doivent être en mesure de faire cohabiter différentes normes sur une même antenne, de diminuer les interférences avec d’autres utilisateurs, d'améliorer le débit des transmissions, d'éviter les phénomènes d'évanouissements, d'assurer une meilleure efficacité dans la réception du signal... Afin de s'adapter avec un tel environnement évolutif et variable avec un minimum d'encombrement et de complexité, les antennes agiles en fréquence, en diagrammes de rayonnement et en polarisation ont été déployées. Le développement des composants actifs tels que les diodes PIN, les diodes varicaps et les MEMS, utilisés pour produire l'agilité, a facilité l'évolution rapide de ces antennes.Les travaux menées dans le cadre de cette thèse s'inscrivent dans ce contexte. Nous nous sommes intéressé à l'étude et la conception de nouvelles topologies d'antennes agiles.Nous avons essayé tout d'abord de définir le concept d'antenne agile et d'identifier les différentes techniques de reconfigurabilité avant de proposer une classification des antennes agiles en fonction de la fonctionnalité proposée, à savoir l'agilité en fréquence, en diagrammes de rayonnement et en polarisation.Les travaux présentés dans ce mémoire sont principalement axés sur l'étude de chacune de ces fonctionnalités. En effet, plusieurs topologies d'antennes ont été étudiées et expérimentalement caractérisés:- Une antenne carré multi bande avec fente fractale capable de commuter entre quinze bandes de fréquences de 0.5 à 6 GHz.- Une antenne elliptique ULB à rejet de bandes reconfigurable fonctionnant de 0.76 à 6 GHz.- Une antenne dipôle constitué de deux boucles circulaires identiques capables de piloter son diagramme de rayonnement dans trois directions différentes à 1.54 GHz.- Un dipôle avec réflecteurs et directeurs fonctionnant en trois modes, capable de rediriger son diagramme de rayonnement dans une direction privilégiée tout en modifiant l’angle d’ouverture du faisceau rayonné.- Une antenne à double boucles rectangulaires capable de commuter entre une polarisation linéaire à 1.54 GHz ou à 1.63 GHz, une polarisation circulaire droite et une polarisation circulaire gauche.Le choix de la technique de reconfigurabilité est les dicté par besoins de l’application visée. / With the emergence of new standards, new telecommunication systems must be able to cohabit different standards on the same antenna, to reduce interference with other users, improve the flow of communications, avoid the detrimental fading loss, ensure greater efficiency in the signal reception ... In order to adapt with such evolving and changing environment with minimal congestion and complexity, antennas with agile frequency, radiation patterns and polarization properties have been deployed. The development of active components such as PIN diodes, varactors diodes and MEMS switches used to produce agility, facilitated the rapid development of these antennas.Works carried out during this thesis fit into this context. We are interested in the study and design of new topologies of agile antennas.We tried at first to define the concept of agile antenna and identify the different techniques of agility before proposing a classification of agile antennas based on the proposed feature, namely agility in frequency, radiation patterns and polarization.Works presented in this thesis are mainly focused on the study of each of these features. Indeed, several topologies have been studied and experimentally characterized:- A square multiband antenna with fractal slot able to switch between fifteen frequency bands from 0.5 to 6 GHz.- An elliptical UWB antenna with reconfigurable rejection bands operating from 0.76 to 6 GHz.- A dipole antenna consists of two identical circular loops able to tilt its radiation pattern in three different directions at 1.54 GHz.- A dipole with reflectors and directors, working in three modes, able to steer its radiation pattern in a different direction while changing the opening angle of the radiated beam.- Rectangular bi-loop single-feed antenna able to toggle either between Linear Polarization (LP) and Circular Polarization (CP) or between two CP (Right Hand (RHCP) and Left Hand Circular Polarization (LHCP).The choice of used agility technique is dictated by needs of the targeted application.