Les microphones sont des capteurs qui permettent à nos systèmes électroniques de prendre connaissance de notre environnement acoustique en fournissant un signal électrique représentatif des vibrations de l’air. Ils sont employés dans la plupart des systèmes multimédia, mais aussi dans les appareils auditifs. Dans l’implant auditif, le microphone se substitue à l’oreille humaine capable de détecter des pressions acoustiques variants de quelque μPa à quelques Pa. Les microphones, sont en général accompagnés d’un circuit électronique spécifique qui permet leur exploitation au coeur d’un système hétérogène. Depuis les toutes premières transductions acoustique-électriques, le microphone a été perfectionné avec la mise en oeuvre de nouveau principes de transduction et l’élaboration de circuit de conditionnement plus performants. Dernièrement, l’introduction de la technologie MEMS (Micro Electro Mechanical Systems) a permis de réaliser des microphones extrêmement compacts et peu couteux. Ces travaux de recherches concernent la réalisation d’un circuit électronique dédié à l’exploitation d’un transducteur M&NEMS (Micro & Nano Electro Mechanical Systems) survenant comme une évolution du MEMS. Pour commencer l’étude, le principe de transduction et l’application du microphone sont étudiés. Les circuits existants sont examinés en détail et adaptés au transducteur M&NEMS. Les résultats potentiels sont discutés et situés dans l’application. Dans un second temps, un circuit de conditionnement spécifique est proposé. Les résultats sont présentés puis le circuit électronique dédié est intégré sur silicium. Les performances des blocs fonctionnels intégrés sont mesurées et présentées. / Microphones are sensors which allow gauging acoustic environment through an electric representation of vibrations in the air. They can be found in most multimedia equipment and in hearing aids. In this particular application, microphone substitutes a human ear which is able to sense pressure level of sound ranging from a μPa to few Pa. The read-out circuit of microphones converts physical signal from transducer into electronic signals that can be used in any heterogeneous system involving audio processing. Transducers of microphones have known successive generation of improvement. The latest refinement is related to the emergence of MEMS (Micro Electro Mechanical Systems) technology which is suitable to build compact sensor. This thesis explores the design of a readout-circuit using an innovative M&NEMS (Micro & Nano Electro Mechanical Systems) technology derived from MEMS. The thesis is structured beginning with review of existing circuits for M&NEMS microphone. A comparative study is reported considering the proposed technical specifications using simulations and a prototype was realized using discrete components. In the second phase, an innovative circuit was proposed as an ASIC solution targeting M&NEMS technology developed at CEA-LETI. The performance evaluation and the physical measurements of the proposed ASIC are detailed.

Le marché des capteurs de pression pour le secteur aéronautique est mature mais encore en forte croissance, caractérisé par une forte valeur ajoutée, et générateur d'une forte demande en innovation. Par exemple, le rapprochement des systèmes de mesure vers les zones chaudes de l'avion nécessite de revoir l'architecture du capteur, dont l'élément sensible.Pour répondre à ces besoins, nous avons développé un capteur de pression intégrant une détection du mouvement d'un microrésonateur sur membrane avec des nanofils en silicium piezorésistifs. Une version simplifiée de microrésonateur sans ces nanojauges de déformation a été conçue, modélisée, fabriquée puis caractérisée afin d'en valider le bon fonctionnement. En parallèle, les caractéristiques électro-thermo-mécaniques et de bruit de nanojauges couplées à des résonateurs M&NEMS issus de précédents travaux ont été étudiées. Nous avons ainsi montré qu'un nanofil en compression harmonique longitudinale à basse fréquence se comporte comme un ressort-amorti pouvant dominer la réponse harmonique du résonateur MEMS, malgré ses dimensions minuscules. De plus, nous avons montré pour la première fois que la réponse harmonique d'un résonateur pouvait être ajustée « in-situ » à l'aide du phénomène de rétro-action pieozorésistive en modifiant uniquement la polarisation des nanofils. Enfin, les performances théoriques du capteur de pression ont été estimées à partir de données expérimentales relevées sur différents types de résonateurs M&NEMS. Ces performances théoriques sont satisfaisantes vis-à-vis des spécifications du capteur, mais nécessiteront néanmoins d'être validées expérimentalement. / The market of pressure sensors for aeronautics is mature but still strongly growing, defined by a strong added value and a large innovation need. Bringing pressure sensors closer to hot parts of the plane, requires, for example, to re-consider the sensor architecture, including the sensitive element.In order to comply with these requirements, we have developed a resonant pressure sensor with motion detection by Si piezoresistive nanowires. A simplified version of the resonator without these nanogauges has been modelled, fabricated and characterized to confirm its good operation. In parallel, electro-thermo-mechanical and noise characteristics of nanogauges coupled to M&NEMS resonators arising from previous works have been studied. We have notably demonstrated that the damped-spring behavior of an harmonically longitudinally stressed nanowire at low frequency could govern the MEMS resonator response, despite its tiny dimensions. Moreover, we have shown for the first time that the resonator response could be tuned “in situ” owing to the piezoresistive back action phenomenon only by acting on the nanowire biasing.Eventually, the theoretical performances of the resonant pressure sensor have been estimated from experimental data on different kind of M&NEMS resonator. These theoretical performances satisfy the sensor specifications; nevertheless they need to be confirmed experimentally.

In general terms, this thesis is about tuning coupled electronic and nuclear (or mechanical) dynamics in the nanoscale. With “tuning” we mean changing parameters to achieve a specific phenomenon or functionality. This is not a trivial task in this context, because the dynamics of the systems we consider depend nontrivially on the parameters. To be more concrete, we consider two systems which are “complimentary” in many aspects. We start by studying nonradiative decay of an electronic excitation in a minimal example from supramolecular chemistry: a molecular dimer. Each monomer in our model has two electronic states and the respective potential energy surfaces (PESs) are harmonic. Electronic de-excitation occurs in the monomeric level through well-localized regions in the nuclear space which we call ``NRD channels\'\'. The monomers interact via transition dipole-dipole interaction. The decay dynamics of the monomer are trivial due to its harmonic PESs and simple NRD channel. However, the dimer shows distorted and nontrivially coupled PESs conferring rather complex decay dynamics on it. Depending on the position of the NRD channel, we find that the NRD lifetime can exhibit a completely different dependence on the intermolecular-interaction strength. The extension to larger aggregates and the implications to the quantum yield of molecular systems will be discussed. Our findings suggest design principles for molecular systems where a specific fluorescence quantum yield is desired. The most part of this thesis is about a nanoscale rotor driven by charge tunneling. The rotor consists of electronic islands linked to a bearing via insulating arms. The islands can exchange electrons via tunneling with flanking electronic leads. An uniform electrostatic field brings about the coupling between electronic and mechanical degrees of freedom. Moreover, coupling to an environment lead to dissipation in the mechanical dynamics. In the literature one can identify two generic models of this type of rotor [1-3], which we refer to as “mean-field” and “stochastic” models in this thesis. In the mean-field model the system is described by a set of deterministic differential equations involving the average charge on the electronic islands, and therefore charge fluctuations are not taken into account. In the stochastic model the rotor is described by Fokker–Planck equations which fully take into account the charge fluctuations. We start by showing and comparing the dynamics of these models. The models show interesting phenomenology and predict useful functionality to the rotor. However, it is often unclear which assumptions are made upon the system when using these models. To clarify this matter we derived the models using the “orthodox” theory of single electron tunneling [4]. Next, we go on and propose experimental devices which can be described by these models. The parameter ranges accessible using these devices are estimated. Turning our attention back to functionality, we show how to introduce a preferred direction of rotation, which is useful in the context of motors. In the outlook we also show how to recast the system as a current rectifier. [1] A. Y. Smirnov, S. Savel’ev, L. G. Mourokh and F. Nori; Phys. Rev. E 78 031921 (2008). [2] A. Croy and A. Eisfeld; EPL (Europhysics Lett. 98 68004 (2012). [3] A. Smirnov, L. Murokh, S. Savel’ev and F. Nori; Bio-mimicking rotary nanomotors; volume 7364 (2009); doi:10.1117/12.821567; URL http://dx.doi.org/10.1117/12. 821567. [4] B. L. Altshuler, P. A. Lee and W. R. Webb; Mesoscopic phenomena in solids; volume 30; Elsevier (2012).

El objetivo de esta tesis es la implementación de sensores de alta resolución, formados por sistemas micro/nano electromecánicos integrados monolíticamente, basados en palanca como elemento transductor y utilizando para la fabricación tecnologías de silicio. En concreto, se determinará la tecnología de fabricación óptima para la implementación de sensores basados en palancas, para aplicaciones en aire o vacio y líquido. Se establecerán las técnicas de detección y excitación adecuadas para los sensores basados en palancas. Y se realiza la compatibilización de la tecnología de fabricación de sensores con la tecnología CMOS, de forma que se consiga la integración monolítica del sistema.Para ello, se fabrican tres demostradores distintos, dos de ellos sensores de masa formados por palancas resonantes y un tercer sistema capaz de trabajar en medio líquido para detección electroquímica. En el primer demostrador se fabrica un sensor de masa formado por una matriz de palancas de polisilicio integrado monolíticamente con la circuitería de lectura. Para ello se utiliza como capa estructural uno de los niveles de polisilicio de la tecnología CMOS utilizada (tecnología CMOS CNM25 2P, 2M con dos niveles de metal y dos niveles de polisilicio). Se han diseñado matrices de cuatro y ocho palancas que permiten realizar medidas multiplexadas de cada una de las palancas independientemente y medidas diferenciales. De forma que por un lado se aumenta la versatilidad del sistema y al realizar medidas diferenciales mejora la resolución. Durante el proceso CMOS se definen las áreas de fabricación y como post-proceso se definen los transductores mecánicos. Tras caracterización eléctrica de los sistemas, de este demostrador se concluye que la integración monolítica es posible y se dispone de un sistema versátil, con resolución en masa inferior a los 40 ag/Hz. El segundo demostrador consiste en un sensor de masa formado por palancas resonantes de silicio cristalino. Para utilizar silicio cristalino como capa estructural se desarrolla una nueva tecnología, a partir de sustratos SOI, que permite definir regiones para fabricación de la circuitería CMOS y regiones con estructura SOI para la implementación de los transductores. Una vez definida la tecnología, se implementan sensores de masa resonantes (como en el primer demostrador) con mejores características de la capa estructural. Se ha probado el funcionamiento de dichos sensores con una resolución máxima en masa de 7 ag/Hz. La tecnología desarrollada permite la fabricación de sistemas MEMS/NEMS integrados monolíticamente que utilizan silicio cristalino como capa estructural. Por ultimo se ha desarrollado un tercer dispositivo, que permite trabajar en medio líquido. Se utiliza como elemento transductor una palanca de silicio cristalino. Para detectar la deflexión de la palanca (provocada por estrés superficial debido al depósito de moléculas) se miden variaciones de corriente electroquímica entre la palanca y un electrodo muy próximo a ella dentro de un bipotenciostato. Es preciso que la separación entre dos electrodos sea inferior a los 100 nm, para poder medir esta corriente. Definir estas separaciones supone un reto tecnológico importante, dado que se trata de definir cortes en silicio de una micra de grosor, con anchura inferior a los 100 nm. Se utilizan técnicas de litografía con resolución nanométrica (con microscopio de fuerzas atómicas, AFM y haz focalizado de iones, FIB) combinadas con grabado seco por iones reactivos (RIE) y ataque directo mediante FIB. Se han conseguido los cortes requeridos y se demuestra el funcionamiento del dispositivo. / The objective of this thesis work is to implement high resolution sensors, formed by micro/nano electromechanical systems integrated monolithically, using cantilevers as transducer and silicon technologies for the fabrication. In particular, the optimal fabrication technology is determined to implement cantilever based sensors for air or vacuum applications and liquid ones. Detection and excitation optimal techniques for cantilever based systems are established. The compatibilization between the sensors fabrication and the CMOS technology is obtained, to achieve the on chip monolithic system.To achieve these objectives, three different demonstrators are fabricated. Two of them are mass sensors formed by resonant cantilevers; the third one is a system able to work in liquid with electrochemical detection. The first demonstrator is a mass sensor formed by a polysilicon cantilevers array integrated monolithically with the readout circuitry. As structural layer, one of the polysilicon layers of the CMOS technology is used (this technology is CMOS CNM25 2P, 2M with two polysilicon layers and to metal ones). Arrays of four and eight cantilevers have been designed, these designs allow multiplexed measures for individual cantilevers and differential measures. On one hand the versatility of the system is increased, by the other differential measures increase the sensor resolution. During CMOS process, fabrication areas are defined; transducers are defined as a post process. After electrical characterization of the system, it can be conclude that the monolithic integration is possible, and it is disposed a versatile system, with mass resolution lower than 40 ag/Hz.A mass sensor formed by resonant cantilevers of crystalline silicon forms the second demonstrator. To use crystalline silicon as structural layer a new technology is developed: from SOI (Silicon on Insulator) substrates, different regions are defined to implement the CMOS on bulk silicon and regions with SOI structure to the transducers. Once, the technology is defined, mass sensors are implemented (like in first demonstrator) increasing the characteristics of the structural layer. IT has been proved the working way of these sensors, with a mass resolution of 7 ag/Hz. The developed technology allows a new platform for MEMS/NEMS fabrications, by monolithic integration and using crystalline silicon as structural layer. Finally, a third device has been defined, which allows to work in liquid. As transducer a crystalline silicon cantilever is used. The deflexion of the cantilever (caused by superficial stress due to molecules adherence) is measured by variations in the electrochemical current between the cantilever and an electrode place close to it, inside a bipotenciostat system. The separation between both electrodes must be smaller than 100nm, to measure this current. The definition of this gaps suppose an important technological issue, due that gaps have to be defined in one micron thick silicon, with a wide smaller than 100 nm. Lithography techniques with nanometric resolutions (atomic force microscope, AFM, and focus ion beam, FIB) combined with reactive ion etching (RIE) are used, together with direct etching with FIB.

Colloid displacement lithography is proving to be very effective in the designing of nanometer scale electronic devices. Precise control of the structure of matter at the nanometer scale has brought a revolutionary change in science and technology. The use of these nanometer scale devices ranges from the diagnosis of various diseases to cell repair to ultra strong materials. This research focused on optimizing the conditions for gold colloid particle adsorption for colloid displacement lithography, an expansion on gold colloid particle manipulation techniques using a scanned probe microscope. The system consists of a scrupulously cleaned glass surface that is coated with poly(diallyldimethylammonium chloride) (PDDA) and then with 5- or 10- nm gold colloid particles. The optimum conditions include the use of very low molecular weight PDDA (Avg MW <100,000 g/mol) or low molecular weight PDDA (Avg MW 100,000-200,000 g/mol) with an exposure time to the glass substrate of 120 to 150 minutes. This is then followed by a 24-hour exposure to the colloid solution. An atomic force microscope (AFM) is used to pattern the thus prepared colloid coated slides. In this work a variety of salts are used as potential blocking agents to prevent or modify the colloid adsorption. These include potassium iodide, potassium bromide, potassium chloride, sodium fluoride, sodiumsulfate, potassium hydrogen phosphate, potassium hydrogen phthalate, and sodium citrate. In summary, the following were found as a result of this work: The optimum conditions that lead to efficient patterning are: Low molecular weight PDDA with a coating time of 120 to 150 minutes. Exposure to 5-nm gold colloid for 24 hours The most interesting potential blocking agents are the phosphate, sulfate and citrate salts, as they show some potential for modifying the adsorption of the gold colloids on the PDDA. The dispersion of the colloid particles on the PDDA does not change when using the potential blocking agents compared to direct adsorption on the unmodified PDDA layer. The use of the potential blocking agents reduces the force required to pattern by a factor of 100 to 300.

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The scanning tunneling microscope (STM) based on quantum tunneling can attain atomic-scale spatial resolution and help elucidate a wealth of phenomena in the microscopic world. However a limitation in scanning tunneling microscopy is the low temporal resolution due to readout circuit frequency rolloff at a few kHz. This limitation can be overcome by using downmixing directly in the tunneling junction. With this technology we measure the high frequency vibrational modes (~ 1 MHz) of MEMS doubly-clamped beams and explore the implication of STM downmixing for nanomechanics.

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