The analysis and development of robust sensing platforms based on solidly-mounted ZnO bulk acoustic wave devices was proposed. The exploitation of acoustic energy trapping was investigated and demonstrated as a method to define active sensing areas on a substrate. In addition, a new "hybrid" acoustic mode experiencing acoustic energy trapping was studied theoretically and experimentally. This mode was used as an explanation of historical inconsistencies in observed thickness-shear mode velocities. Initial theoretical and experimental results suggest that this mode is a coupling of thickness-shear and longitudinal particle displacements and, as such, may offer more mechanical and/or structural information about a sample under test. Device development was taken another step further and multi-mode ZnO resonators operating in the thickness-shear, hybrid, and longitudinal modes were introduced. These devices were characterized with respect to sample viscosity and conductivity and preliminary results show that, with further development, the multi-mode resonators provide significantly more information about a sample than their single-mode counterparts. An alternative to resonator-based platforms was also presented in the form of bulk acoustic delay lines. Initial conceptual and simulation results show that these devices provide a different perspective of typical sensing modalities by using properly designed input pulses, device tuning, and examining overall input and output signal spectra.

This dissertation discusses the design, simulation and characterization of process-compatible accelerometers and gyroscopes for the implementation of multi-degree-of-freedom (multi-DOF) systems. All components presented herein were designed to operate under the same vacuum-sealed environment to facilitate batch fabrication and wafer-level packaging (WLP), enabling the development of small form-factor single-die inertial measurement units (IMUs). The high-aspect-ratio poly and single-crystal silicon (HARPSS) process flow was used to co-fabricate the devices that compose the system, enabling the implementation ultra-narrow capacitive gaps (< 300 nm) in thick device-layer substrates (40 um). The presented gyroscopes were implemented as high-frequency BAW disk resonators operating in a mode-matched condition. A new technique to reduced dependencies on environmental stimuli such as temperature, vibration and shock was introduced. Novel decoupling springs were utilized to effectively isolate the gyros from their substrate, minimizing the effect that external sources of error have on offset and scale-factor. The substrate-decoupled (SD) BAW gyros were interfaced with a customized IC to achieve supreme random-vibration immunity (0.012 (deg/s)/g) and excellent rejection to shock (0.075 (deg/s)/g). With a scale factor of 800 uV/(deg/s), the complete SD-BAW gyro system attains a large full-scale range (2500 deg/s) with excellent linearity. The measured angle-random walk (ARW) of 0.36 deg/rthr and bias-instability of 10.5 deg/hr are dominated by the thermal and flicker noise of the IC, respectively. Additional measurements using external electronics show bias-instability values as low as 3.5 deg/hr. To implement the final monolithic multi-DOF IMU, accelerometers were carefully designed to operate in the same vacuum environment required for the gyroscopes. Narrow capacitive gaps were used to adjust the accelerometer squeeze-film damping (SFD) levels, preventing an under-damped response. Robust simulation techniques were developed using finite-element analysis (FEA) tools to extract accurate values of SFD, which were then match with measured results. Ultra-small single proof-mass tri-axial accelerometers with Brownian-noise as low as 30 ug/rtHz were interfaced with front-end electronics exhibiting scale-factor values in the order of 5 to 10 mV/g and cross-axis sensitivities of less than 3% before any electronic compensation.

Cette thèse s’inscrit dans le cadre d’une cotutelle internationale entre l’institut FEMTO-ST à Besançon en France et l’université de Sherbrooke au Canada. Elle porte sur l’élaboration d’un biocapteur, potentiellement à bas coût, pour la détection de pathogènes dans les secteurs de l’agroalimentaire, de l’environnement et de la biosécurité. Le modèle biologique visé est la bactérie Escherichia coli, dont les souches pathogènes sont responsables, chaque année et partout dans le monde, de plusieurs crises sanitaires liées à une mauvaise gestion des produits de consommation ou des installations de conditionnement ou de traitements de ces produits. L’utilisation de biocapteurs pour une détection rapide, sensible et sélective d’organismes pathogènes répond ainsi aux inquiétudes quant aux risques d’infection pour la population. La structure du capteur consiste en une fine membrane en arséniure de gallium (GaAs) vibrant sur des modes de cisaillement d’épaisseur générés par champ électrique latéral via les propriétés piézoélectriques du matériau. Nous montrons dans ce travail que le biocapteur offre également des possibilités de microfabrication, de biofonctionnalisation et de régénération intéressantes pour la conception d’un dispositif à bas coût. Le transducteur a été réalisé via des technologies de microfabrication utilisées en salle blanche avec une mise en parallèle des méthodes d’usinage par voie chimique et par plasma, l’objectif étant d’obtenir des membranes minces, planes et avec un état de surface de haute qualité. Une interface fluidique a été mise au point de façon à approvisionner de manière homogène le capteur en fluide. Par ailleurs, nos études se sont portées sur la fonctionnalisation biochimique de l’interface de bioreconnaissance sur l’arséniure de gallium et sa caractérisation fine par les techniques de spectroscopie infrarouge à transformée de Fourier (FTIR). Les résultats de cette étude ont permis de progresser sur la compréhension fondamentale du phénomène d’auto-assemblage de molécules sur GaAs. Un effort particulier a été mis en œuvre pour développer des biointerfaces de haute densité offrant une immobilisation optimale des immunorécepteurs biologiques. Parmi les différentes méthodes de régénération de la biointerface, le procédé de photo-oxydation UV en milieu liquide a démontré un fort potentiel pour des applications de capteurs réutilisables. Enfin, le transducteur a été caractérisé électriquement sous différents environnements. L’impact sur la réponse du résonateur des paramètres électriques, mécaniques et thermiques de ces milieux a été évalué afin de simuler le comportement du dispositif en condition réelle. / Abstract : This PhD thesis was realized in the context of a cotutelle program between FEMTO-ST institute in France and the University of Sherbrooke in Canada. The thesis addresses the development of a potentially low cost sensor dedicated for detection of pathogens in food industry processing, environment and biosafety sectors. Such a sensor could serve detection of Escherichia coli bacteria whose pathogenic strains are the source of foodborne illnesses encountered worldwide every year. Hence, biosensor devices are needed for a rapid, sensitive and selective detection of pathogens to avert, as soon as possible, any sources of contamination and prevent outbreak risks. The design of the sensor consists of a resonant membrane fabricated in gallium arsenide (GaAs) crystal that operates at shear modes of bulk acoustic waves generated by lateral field excitation. In addition to the attractive piezoelectric properties, as shown in this work, fabrication of a GaAs-based biosensor benefits from a well-developed technology of microfabrication of GaAs, as well as biofunctionalization and the possibility of regeneration that should result in cost savings of used devices. The transducer element was fabricated by using typical clean room microfabrication techniques. Plasma and wet etching were investigated and compared for achieving thin membranes with high quality surface morphology. At the same time, we designed and fabricated fluidic elements that allowed the construction of a flow cell chamber integrated in the sensor. Extensive research was carried out with a Fourier transform infrared spectroscopy (FTIR) diagnostic tool to determine optimum conditions for biofunctionalization of the GaAs surface. This activity allowed to advance the fundamental knowledge of self-assembly formation and, consequently, fabrication of high density biointerfaces for efficient immobilization of selected bioreceptors. Among different biochip regeneration methods, it has been demonstrated that liquid UV photooxidation (liquid-UVPO) has a great potential to deliver attractive surfaces for re-usable biochips. Finally, operation of the transducer device was evaluated in air environment and in various liquid media, simulating real conditions for detection.

Numerical models will be developed for the prediction of silencer transmission loss under the operating conditions present in gas turbine exhausts. In these systems the large diameter ducts and high operating temperatures produce a challenging acoustic environment due to the unverified behaviour of fibrous materials at high temperatures and the existence of complex sound fields. To understand the behaviour of fibrous materials at high temperatures their bulk acoustic properties are measured using a modified impedance tube which can heat material samples up to a temperature of 500 C. It will be demonstrated that the high temperature material properties can be extrapolated from room temperature measurements given knowledge of the temperature dependant flow resistivity. Finite element numerical models using point collocation and mode matching techniques to predict the transmission loss of silencers are developed and successfully validated. Dissipative silencer designs with various cross-sectional designs are explored numerically and experimentally according to common industry standards. It is demonstrated that transmission loss may be optimised by the arrangement of the fibrous material across the cross-section. The accurate numerical models allow for effe cient silencers to be designed reducing silencer size and cost. A new hybrid silencer is presented combining dissipative and reactive elements with the aim of increasing the low frequency attenuation of large silencers while maintaining an effective broadband spectrum. Measurements and predictions show this innovative design to be successfull. Application of the hybrid silencer allows for more flexible noise control solutions when design is limited by low frequency noise.

This study describes the design and fabrication of dual-mode film bulk acoustic resonator (TFBAR) devices to construct wafer level T-ladder type filters. Reactive radio-frequency (RF) magnetron sputtering method was used to deposit c-axis- tilted ZnO piezoelectric thin films. The piezoelectric ZnO thin films were deposited by a two-step method at room temperature with off-axis. In this investigation, off-axis distance was varied to determine the optimal growth parameters of the tilted piezoelectric thin film. The SEM and XRD analysis reveal that ZnO thin films deposited at off-axis distances of 35 mm yielded a highly textured and sufficiently-tilted ZnO piezoelectric layer for dual-mode TFBAR. Additionally, the ZnO piezoelectric layer with off-axis distances of 35 mm exhibited enhanced competitive growth, and had a c-axis-tilted angle of 5¢X. To explore the relationship between the c-axis-tilted angle and the dual-mode resonance frequency responses (fL and fS) of TFBAR, two TFBAR devices were fabricated with ZnO c-axis tilted at 4.4¢X and 5¢X, respectively. The TFBAR device with 5¢X-tilted ZnO layer exists shear and longitudinal resonant modes. The center-frequency of longitudinal resonant mode is 2.2 times that of the shear resonant mode. The longitudinal mode is suitable for designing as a communication receiver (Rx) device at WCDMA band. On the other hand, the shear mode of TFBAR is suitable for EGSM-900 band. To optimize the characteristics, the filter was annealed by CTA treatment in 400 ¢J. For the frequency responses of the longitudinal wave, the insertion loss was upgraded from -5.77 dB without annealing to -4.85 dB as annealed, the band rejection was reduced from 13.57 dB to 12.65 dB, the bandwidth was broaden from 69.69 MHz to 73.12 MHz. On the other hand, for the frequency responses of the shear wave, the insertion loss was upgraded from -9.94 dB to -8.21 dB, the band rejection was reduced from 13.74 dB to 13 dB, the bandwidth was decreased from 28.13 MHz to 28.12 MHz.

abstract: Micro-electro-mechanical systems (MEMS) film bulk acoustic resonator (FBAR) demonstrates label-free biosensing capabilities and is considered to be a promising alternative of quartz crystal microbalance (QCM). FBARs achieve great success in vacuum, or in the air, but find limited applications in liquid media because squeeze damping significantly degrades quality factor (Q) and results in poor frequency resolution. A transmission-line model shows that by confining the liquid in a thickness comparable to the acoustic wavelength of the resonator, Q can be considerably improved. The devices exhibit damped oscillatory patterns of Q as the liquid thickness varies. Q assumes its maxima and minima when the channel thickness is an odd and even multiple of the quarter-wavelength of the resonance, respectively. Microfluidic channels are integrated with longitudinal-mode FBARs (L-FBARs) to realize this design; a tenfold improvement of Q over fully-immersed devices is experimentally verified. Microfluidic integrated FBAR sensors have been demonstrated for detecting protein binding in liquid and monitoring the Vroman effect (the competitive protein adsorption behavior), showing their potential as a promising bio-analytical tool. A contour-mode FBAR (C-FBAR) is developed to further improve Q and to alleviate the need for complex integration of microfluidic channels. The C-FBAR consists of a suspended piezoelectric ring made of aluminum nitride and is excited in the fundamental radial-extensional mode. By replacing the squeeze damping with shear damping, high Qs (189 in water and 77 in human whole blood) are obtained in semi-infinite depth liquids. The C-FBAR sensors are characterized by aptamer - thrombin binding pairs and aqueous glycerine solutions for mass and viscosity sensing schemes, respectively. The C-FBAR sensor demonstrates accurate viscosity measurement from 1 to 10 centipoise, and can be deployed to monitor in-vitro blood coagulation processes in real time. Results show that its resonant frequency decreases as the viscosity of the blood increases during the fibrin generation process after the coagulation cascade. The coagulation time and the start/end of the fibrin generation are quantitatively determined, showing the C-FBAR can be a low-cost, portable yet reliable tool for hemostasis diagnostics. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

This dissertation investigates dissipation in microelectromechanical (MEMS) resonators via detailed analysis and modeling of the energy loss mechanisms and provides a framework toward creating resonant devices with ultra-low dissipation. Fundamental mechanisms underlying acoustic energy loss are explored, the results of which are applied to understanding the losses in resonant MEMS devices. Losses in the materials, which set the ultimate limits of the achievable quality factor of the devices, are examined. Other sources of loss, which are determined by the design of the resonator, are investigated and applied to example resonant MEMS structures. The most critical of these designable loss mechanisms are thermoelastic dissipation (TED) and support (or anchor) loss of acoustic energy through the attachment of the MEMS device to its external environment. The dissipation estimation framework enables prediction of the quality factor of a MEMS resonator, which were accurate within a factor of close to 2 for high-frequency bulk acoustic wave MEMS resonators, and represents a signficant step forward by closing one of the largest outstanding problems in MEMS devices: how to predict the quality factor for a given device. Dissipation mitigation approaches developed herein address the most critical dominant loss mechanisms identified using the framework outlined above. These approaches include design of 1D phononic crystals (PCs) and novel 3D MEMS structures to trap and isolate vibration energy away from the resonator anchors, optimization of resonator geometry to suppress thermoelastic dissipation, and analysis of required levels of surface polish to reduce surface dissipation. Phononic crystals can be used to manipulate the properties of materials. In the case of the 1D PC linear acoustic bandgap (LAB) structures developed here, this manipulation arises from the formation of frequency stop bands, or bandgapwhich convert silicon from a material capable of supporting acoustic waves to a material which rejects acoustic propagation at frequencies in the bandgap. The careful design of these LAB structures is demonstrated to be able to enhance the quality factor and insertion loss of MEMS resonators without significant detrimental effects on the overall device performance.

Cette thèse porte sur l'élaboration d'un biocapteur, à bas coût, pour la détection de pathogènes dans les secteurs de l'agroalimentaire et de l'environnement. Le modèle visé est la bactérie Escherichia coli, dont les souches pathogènes sont responsables, chaque année, de plusieurs crises sanitaires. L'utilisation de biocapteurs pour une détection rapide, sensible et sélective de pathogènes répond ainsi aux inquiétudes quant aux risques d'infection pour la population. Le capteur est constitué d'une fine membrane en arsénieure de gallium (GaAs) vibrant sur des modes de cisaillement d'épaisseur générés par champ électrique latéral via ses propriétés piézoélectriques. Nous montrons dans ce travail que la GaAs offre des possibilités de microfabrication, de biofonctionnalisation et de régénération intéressantes pour la conception d'un dispositif à bas coût. Nous avons mis en parallèle deux méthodes d'usinage de membranes minces : par voie chimique et par plasma, avec pour objectif, l'obtention de structures planes et lisse. Nous nous sommes intéressés à la réalisation d'une interface de bioreconnaissance. La caractérisation de celle-ci, par les techniques de spectroscope infrarouge à transformée de Fourier, nous a fait progresser sur a compréhension du phénomène d'auto-assemblage de molécules sur GaAs et nous a permis de développer des interfaces à haute densité. Nous avons étudié sa régénération et la photo-oxydation par UV a démontré un fort potentiel pour des applications de capteurs réutilisables. Enfin à travers des caractérisations électriques du transducteur, nous avons mis en avant l'impact de différents paramètres de l'environnement sur la réponse du dispositif. / This thesis addresses the development of a potentially low cost sensor dedicated for detection of pathogens in food industry processing and environment sectors. Such a sensor could serve detection of Escherichia coli bacteria whose pathogenic strains are the source of foodborne illnesses encountered worldwide every year. Hence, biosensor devices are needed for a rapid, sensitive and selective detection of pathogens to prevent outbreak risks. The design of the sensor consists of a resonant membrane fabricated in gallium arsenide (GaAs) crystal that operates at shear modes of bulk acoustic waves generated by lateral field excitation. In addition to its piezoelectric properties, as shown in this work, fabrication of a GaAs-based biosensor benefits from a well-developed technology of microfabrication and biofunctionalization and the possibility of regeneration that should result in cost savings of used devices. The transducer was fabricated by using typical clean room fabrication techniques. Plasma and wet etching were investigated and compared for achieving thin membranes with high quality surface morphology. Extensive research was carried out by Fourier transform infrared spectroscopy to determine optimum conditions for biofunctionalization of the GaAs surface. This activity allowed to advance the fundamental knowledge of self-assembly formation and, consequently, fabrication of high density biointerfaces. Among different biochip regeneration methods, it has been demonstrated that liquid UV photooxidation has a great potential for re-usable devices. Finally, operation of the transducer device was evaluated in various medium, simulating real conditions for detection.

Ces travaux de thèe portent sur le développement d’un outil d’analyse numérique dédié à l’ étude de nouveaux résonateursà quartz à ondes de volume et utilisant les éléments finis. Cette méthode de caractérisation permet la détermination deséléments du schéma électrique équivalent (résistance, inductance et capacité) d’une fréquence de résonance donnée ainsique son facteur de qualité, tout en prenant en compte dans le modèle la sensibilité du cristal de quartz à la températureet aux contraintes induites par le montage. Une étape de validation est d’abord réalisée afin de vérifier nos choix, enterme de modélisation et de calcul, en confrontant les données issues de la simulation aux mesures de résonateurs déjàexistants. Les trois dispositifs analysés (40 MHz, 10 MHz et 100 MHz) montrent une bonne concordance entre théorieet expérience. Pour obtenir de tels résultats, la structure de maintien est prise en compte et modélisée sous forme dezones d’amortissement de Rayleigh lorsque le piégeage de l’énergie n’est pas optimal (présence d’un mode de plaque).Un aspect important des résonateurs est ensuite étudié : le comportement en température. En effet, les contraintes dedilatation thermique ainsi que l’évolution des coefficients élastiques en fonction de la température induisent une dérivefréquentielle. La comparaison entre théorie et expérience nous permet de vérifier l’allure des courbes et de quantifier ledegré de précision du modèle. L’effet d’une contrainte mécanique appliquée sur le pourtour de la lame de quartz est parla suite introduit dans le modèle en utilisant la méthode de perturbation de Sinha-Tiersten. Il est alors possible de définirl’impact des défauts de fabrication sur la fréquence du résonateur. Enfin, la méthode numérique est appliquée à l’étudede structures innovantes dans le cadre du projet FREQUENCE2009. Il s’agit de revisiter le concept du résonateur BVA etd’envisager des procédés de fabrication collective. L’idée consiste ainsi à remplacer le rayon de courbure d’un résonateur,dont la fréquence utile se trouve aux alentours de 9 MHz, par une série de marches, plus compatible avec les procédés dela micro électronique (DRIE : Deep Reactive Ion Etching). Bien que les résultats expérimentaux soient, dans ce cas, loin denos attentes, nous constatons que l’outil d’analyse est parfaitement capable de prédire les caractéristiques de nouvellesstructures. / This work is devoted to the development of a digital analysis tool dedicated to study new bulk acoustic waves quartz resonatorsby using finite elements. This method of characterization allows the calculation of the elements of the equivalentelectrical circuit (resistor, inductance and capacitor) of a given resonant frequency as well as the quality factor, while takinginto account its sensitivity to the temperature and to the stresses induced by the mounting support. Firstly, a validationphase is carried out in order to check our choices, in terms of modeling and computation, by comparing simulation data tothe measures of existing resonators. The three analyzed devices (40MHz, 10 MHz and 100 MHz) show good agreementbetween theory and experiment. To obtain such results, the mounting support is taken into account and modeled thanks toRayleigh damping areas when the trapping of energy is not optimal (presence of a spurious shell vibration mode). Then, animportant aspect of resonators is studied : the temperature behavior of its vibrating modes. Indeed, the thermal expansionstresses as well as the change of stiffness coefficients according to the temperature induce frequency shift. The comparisonbetween theory and experiment allows us to check the shape of curves and to quantify the accuracy of the model.Thereafter, the effect of mechanical stress applied on the edge of the blank of quartz is introduced in the model by usingthe perturbation method developed by Tiersten and Sinha. So, it is possible to define the influence of some manufacturingdefects on the resonant frequency. Finally, the digital method is applied to study innovative structures in the framework ofthe project FREQUENCE2009. The aim is to review the concept of BVA resonator and consider collective manufacturingprocesses. The idea involves replacing the radius of curvature of a resonator, for which the expected frequency is around9 MHz, by several steps, more compatible with microelectronics processes (DRIE : Deep Reactive Ion Etching). Althoughthe results are far from our expectations, we note that the analysis tool is perfectly able to anticipate the characteristics ofnew structures.

Advancing the field of nanotechnology to incorporate the unique properties observed at the nanoscale into functional devices has become a major scientific thrust of the 21st century. New fabrication tools and assembly techniques are required to design and manufacture devices based on one-dimensional nanostructures. Three techniques for manipulating nanomaterials post-synthesis have been developed. Two of them involve direct contact manipulation through the utilization of a physical probe. The third uses optically generated surface acoustic waves to reproducibly control and assemble one-dimensional nanostructures into desired locations. The nature of the third technique is non-contact and limits contamination and defects from being introduced into a device by manipulation. While the effective manipulation of individual nanostructures into device components is important for building functional nanosystems, commercialization is limited by this one-device-at-a-time process. A new approach to nanostructure synthesis was also developed to site-specifically nucleate and grow nanowires between two electrodes. Integrating synthesis directly with prefabricated device architectures leads to the possible mass production of NEMS, MEMS and CMOS systems based upon one-dimensional nanomaterials. The above processes have been pursued to utilize piezoelectric ZnO nanobelts for applications in high frequency electronic filtering as well as biological and chemical sensing. The high quality, single crystal, faceted nature of these materials make them ideal candidates for studying their properties through the designs of a bulk acoustic resonator. The first ever piezoelectric bulk acoustic resonator based on bottom-up synthesized belts will be demonstrated. Initial results are promising and new designs are implemented to scale the device to sub-micron dimensions. Multiple models will be developed to assist with design and testing. Some of models presented will help verify experimental results while others will demonstrate some of the problems plaguing further investigations.