Modeling and numerical analysis of quartz crystal resonators

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

Modélisation et analyse numérique de résonateurs à quartz à ondes de volume

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.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

Direct genotyping of Toxoplasma gondii from amniotic fluids based on B1 gene polymorphism using minisequencing analysis

International audienceBACKGROUND: Because some Toxoplasma gondii genotypes may be more virulent in pregnant women, discriminating between them appears valuable. Currently, the main genotyping method is based on single copy microsatellite markers, which limit direct genotyping from amniotic fluids (AFs) to samples with a high parasitic load. We investigated whether the multicopy gene B1 could type the parasite with a higher sensitivity. To estimate the amplifiable DNA present in AFs, we first compared three different PCR assays used for Toxoplasma infection diagnosis: the P30-PCR, targeting the single copy gene P30; the B1-PCR, targeting the repeated B1 gene; and RE-PCR, targeting the repeated element. RESULTS: Of the 1792 AFs analyzed between 2008 and 2011, 73 were RE-PCR positive. Of those, 49 (67.1%) were P30-PCR and B1-PCR positive, and 14 (19.2%) additional AFs were B1-PCR positive only.All 63 BI-positive AFs (France n = 49; overseas n = 14) could be genotyped based on an analysis of eight nucleotide polymorphisms (SNPs) located within the B1 gene. Following high-resolution melting (HRM) analysis, minisequencing was carried out for each of the eight SNPs. DNA from six reference strains was included in the study, and AFs were assigned to one of the three major lineages (Types I, II, and III). In total, 26 genotypes were observed, and the hierarchical clustering distinguished two clades in lineages II (IIa, n = 30 and IIb, n = 4) and III (IIIa n = 23 and IIIb n = 6). There was an overrepresentation of overseas isolates in Clade IIb (4/4, 100%) and Clade IIIa (8/22; 36.4%) (p \textless0.0001), whereas medical interruption and fetal death were overrepresented in Clade IIb (2/4, 50%) and Clade IIIa (4/23, 17.4%) (p = 0.049). CONCLUSIONS: Although the current genotyping system cannot pretend to replace multilocus typing, we clearly show that targeting the multicopy B1 gene yields a genotyping capacity of AFs around 20% better than when single copy targets are used. The present genotyping method also allows clear identification of genotypes of potential higher virulence

Smart Cut™ Piezo On Insulator (POI) substrates for high performances SAW components

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Stress sensitivity coefficients of HBAR

International audienceVibration sensitivity is an important specification for oscillators dedicated to space or airborne systems. Vibration sensitivity can be due to the resonator, the oscillator loop or non-oscillator components like wire, for instance. Commonly, the main source of acceleration sensitivity is due to the resonator. Active compensation can be used to decrease this effect, but such systems are not easily miniaturized. This paper presents computations of the stress sensitivity coefficients of frequency for the high-overtone bulk acoustic resonators and the design of a simple packaging to minimize vibration sensitivity. The final goal is to control vibration sensitivity of the high-overtone bulk acoustic resonators with dedicated packaging. The computed results are compared to experimental ones. The agreement between theoretical and experimental results is about 50%

How to Qualify LGT Crystal for Acoustic Devices?

International audienceBefore using any piezoelectric crystal to realize acoustic devices (sensors, transducers, actuators or ultra-stable resonators) and beyond its mechanical properties, the crystal material itself has to be characterized. Whether the very interesting properties of theLGT crystal make it the best candidate to substitute quartz crystal for frequency output devices, we must take into account the crystal quality. Indeed, applications require homogeneous crystals with reproducible physical properties

New generation of composite substrates based on a layer of LiTaO3 on silicon for surface acoustic waves components

International audienceThe development of new generations of telecommunication systems requires more and more components and radio-frequency (RF) modules to select and the process signals supporting the information. The solution the most used for this kind of application is always based on the principle of surface acoustic waves (SAW) and its associated components, taking into account their unique spectral quality (insertion losses, out of band rejection, group delay?), their design flexibility and their compactness for L- and S-bands. Although still commonly used today, filters on single-crystals such as lithium tantalate (LiTaO3) and lithium niobate (LiNbO3) cannot be used for future RF modules since the intrinsic stability of these substrates is far from being adapted to meet the challenges of modern telecommunications. To respond to this demands, a new generation of substrates is necessary. The main idea of the work presented here then consists in combining a thin piezoelectric film and a substrate having a thermal expansion much lower than that of piezoelectric layer. This kind of structure is named POI for Piezoelectric-On-Insulator. Although studied for years, this solution is meeting a growing interest given the advantages it offers for SAW filters. We propose to present a review of the concepts as well as the work which led to these developments. An overview of the different technologies enabling the manufacture of these composite substrates will also be proposed. Figures of merit on test vehicles as well as examples of applications will be presented in order to highlight the potential of this new technological solution. Finally, we will conclude on the interest and prospects of such a structure for the telecommunications and wireless sensors, compared to single-crystals substrates

4.2 GHz LiNbO 3 Film Bulk Acoustic Resonator

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High-Frequency Surface Acoustic Wave Devices Based on Epitaxial Z-LiNbO3 Layers on Sapphire

International audienceFilter market demand pushes to the development of new piezoelectric materials to address modern telecommunication challenges. Composite wafers combining an epitaxial piezoelectric layer and a said high velocity and acoustic quality substrate is a promising way to answer that demand. However, the fabrication of high-quality LiNbO3 films with reproducible physical properties is complicated by the difficulty to control volatile Li2O incorporation into the film and to measure its composition. So far, large-scale production of films with physical properties suitable for the targeted applications is not available. In this paper, lithium niobate films with controlled nonstoichiometry were deposited by means of pulsed injection metalorganic vapor phase deposition. We have demonstrated a high acoustical performance for surface acoustic wave (SAW) devices operating in the frequency range from 3.7 GHz up to 5.3 GHz and based on grown epitaxial Z-axis oriented LiNbO3 films on sapphire. An electromechanical coupling of 8 % for the Rayleigh wave at 5.3 GHz was demonstrated experimentall

Electrode Confined Acoustic Wave (ECAW) devices for Ultra High Band applications

International audienceThis paper presents a new approach to increase the operational frequency of Surface Acoustic Wave devices. The excitation of a new type of mode called ECAW ( Electrode Confined Acoustic Wave) exhibiting a phase velocity much higher than the one of a standard SAW is demonstrated. In this context, a new composite substrate is considered to guarantee a perfect spectral purity. Therefore, Piezo-On-Glass substrates are manufactured and used for the manufacturing of ECAW device prototypes. Preliminary results show a frequency at 2.5 GHz with an IDT pitch equal to 2 μm. In terms of power handling, widest tested components successfully handle up to 36 dBm without destruction of the devices