Ulm, Univ. Diplomarbeit., 2002. Chemical vapor deposition.

München, Techn. Univ., Diss., 2004. / Computerdatei im Fernzugriff.

München, Techn. Universiẗat, Diss., 2004.

Les MEMS sont aujourd’hui une réalité économique et sont d’ores et déjà utilisés dans un grand nombre d’objets de notre quotidien. Ces composants peuvent utiliser un actionnement piézoélectrique, notamment à base de PZT déposé en couches minces, du fait de son fort coefficient piézoélectrique. Pour dimensionner au mieux et de manière prédictive ces MEMS à base de PZT, il est important de connaitre les propriétés mécaniques du PZT, matériau complexe. Nous avons utilisé l’acoustique picoseconde, technique qui permet de sonder la matière avec des ondes acoustiques générées par des impulsions laser ultra-courtes. Elle permet de transposer à l’échelle nanométrique le principe du sonar. Lors de cette thèse nous avons étudié le PZT en couches minces par acoustique picoseconde. Nous avons pu extraire le module d’Young et le coefficient de Poisson sans faire l’approximation de l’un ou de l’autre. Nous avons également étudié la relaxation des parois de domaines, en mettant en œuvre des mesures d’acoustique picoseconde en fréquence. A l’aide des propriétés mécaniques du PZT, issues des mesures d’acoustique picoseconde, nous avons pu extraire le coefficient piézoélectrique par la comparaison de modèles et de mesures sur une poutre encastrée-libre avec un actionneur à base de PZT. Enfin, nous avons appliqué ces données d’entrée au dimensionnement de dalles haptiques utilisant des actionneurs PZT. Le très bon accord entre la caractérisation de ces dispositifs et les modèles mis en place prouve l’apport de l’acoustique picoseconde pour le dimensionnement de MEMS. / MEMS components are today an economic reality and are already used in many mass market applications. These devices can use a piezoelectric actuation, in particular based on thin-film PZT due to its high piezoelectric coefficient. To perform predictive design of high performances components based on PZT actuators, mechanical properties of the PZT are required. We used the picosecond ultrasonic technique which probes thin layers with high frequency acoustics waves generated by ultra-short laser pulses. It allows the transposition of the sonar principle at nanometric scale. During this PhD, we studied thin-film PZT using picosecond ultrasonics. We extracted both Young’s modulus and Poisson ratio without an approximation of one or the other. We also studied wall domain relaxation using picosecond ultrasonic measurement at various frequencies. Using PZT mechanical properties obtained from picosecond ultrasonics, we extracted the PZT piezoelectric coefficient, from the comparison between PZT-based cantilever measurement and numerical modeling. Finally, we applied these data for the design of haptic plates using thin-film PZT actuators. The good agreement between haptic plate measurements and modelization proves all the benefit of picosecond ultrasonics for MEMS design.

This thesis reports the design and modelling of a MEMS (Micro Electro Mechanical system) based inertial accelerometer. The main motivation to design a differential type of accelerometer is that such a kind of structure allows differential electrostatic actuation and capacitive sensing. They can be operated at the border of stability also so that the “pull in” operation mode can be explored. Such kinds of structures have a wide range of applications because of their high sensitivity. One is in the field of minimally invasive surgery where accelerometers will be combined with gyroscopes to be used in the navigation of surgical tools as a inertial micro unit (IMU). The choice for the design of a structure with 1 Degree ofFreedom(DOF) , instead of a 2-DOF device was instigated by the simplicity of the design and by a more efficient 1-DOF dynamic model. The accelerometers were designed and optimized using the MATLAB simulator and COVENTORWARE simulation tool. First set of devices is fabricated using a commercial foundry process called SOIMUMPs. The simulation tests show that the SOl accelerometer system yields 8.8kHz resonant frequency, with a quality factor of 10 and 2.l2mV/g sensitivity. To characterize the accelerometer a new semi automatic tool was formulated for the noise analysis and noise based optimization of the accelerometer design and the analysis estimation shows that there is a trade off between the SIN ratio and the sensitivity and for the given design could be made much better in terms of SIN by tuning its resonant frequency.

This thesis reports the design and modelling of a MEMS (Micro Electro Mechanical system) based inertial accelerometer. The main motivation to design a differential type of accelerometer is that such a kind of structure allows differential electrostatic actuation and capacitive sensing. They can be operated at the border of stability also so that the “pull in” operation mode can be explored. Such kinds of structures have a wide range of applications because of their high sensitivity. One is in the field of minimally invasive surgery where accelerometers will be combined with gyroscopes to be used in the navigation of surgical tools as a inertial micro unit (IMU). The choice for the design of a structure with 1 Degree ofFreedom(DOF) , instead of a 2-DOF device was instigated by the simplicity of the design and by a more efficient 1-DOF dynamic model. The accelerometers were designed and optimized using the MATLAB simulator and COVENTORWARE simulation tool. First set of devices is fabricated using a commercial foundry process called SOIMUMPs. The simulation tests show that the SOl accelerometer system yields 8.8kHz resonant frequency, with a quality factor of 10 and 2.l2mV/g sensitivity. To characterize the accelerometer a new semi automatic tool was formulated for the noise analysis and noise based optimization of the accelerometer design and the analysis estimation shows that there is a trade off between the SIN ratio and the sensitivity and for the given design could be made much better in terms of SIN by tuning its resonant frequency.

Erlangen-Nürnberg, Univ., Diss., 2009.

University, Diss., 2005--Kiel.

This thesis reports the design and modelling of a MEMS (Micro Electro Mechanical system) based inertial accelerometer. The main motivation to design a differential type of accelerometer is that such a kind of structure allows differential electrostatic actuation and capacitive sensing. They can be operated at the border of stability also so that the “pull in” operation mode can be explored. Such kinds of structures have a wide range of applications because of their high sensitivity. One is in the field of minimally invasive surgery where accelerometers will be combined with gyroscopes to be used in the navigation of surgical tools as a inertial micro unit (IMU). The choice for the design of a structure with 1 Degree ofFreedom(DOF) , instead of a 2-DOF device was instigated by the simplicity of the design and by a more efficient 1-DOF dynamic model. The accelerometers were designed and optimized using the MATLAB simulator and COVENTORWARE simulation tool. First set of devices is fabricated using a commercial foundry process called SOIMUMPs. The simulation tests show that the SOl accelerometer system yields 8.8kHz resonant frequency, with a quality factor of 10 and 2.l2mV/g sensitivity. To characterize the accelerometer a new semi automatic tool was formulated for the noise analysis and noise based optimization of the accelerometer design and the analysis estimation shows that there is a trade off between the SIN ratio and the sensitivity and for the given design could be made much better in terms of SIN by tuning its resonant frequency. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Low frequency (<100 Hz) acceleration sensing with low noise and traceability is critical in seismology, military surveillance, and emerging technologies. Typically, MEMS (Microelectromechanical systems) are not ideally suited for low frequency accelerometry since their fundamental thermomechanical fluctuation noise limit is higher than in macroscopic accelerometers of higher proof mass. However recent work on thin film MEMS resonators shows promising development in the reduction of damping which in turn reduces fundamental thermomechanical fluctuation noise limit. We aim to harness these low damping thin films in the context of accelerometry, by mass loading them to make them sensitive to acceleration. This work reports an experimental characterization of a mass-loaded silicon nitride membrane-based resonator, which is investigated towards the development of accelerometers for acceleration sensing at low frequencies. We experimentally demonstrate a 1.1 × 10⁻⁶ kg proof mass system achieving a 17,950 mechanical quality factor for a 526 Hz natural resonance frequency, which compares favorably to other optically interrogated on-chip accelerometers [1]-[3]. The inferred acceleration noise floor of the device is currently limited by the displacement noise of the optical fiber displacement readout, yielding a noise amplitude spectral density of 1 μg/√Hz at 10 Hz. This thesis first details a literature review of various high-performance, mass-loaded MEMS accelerometers categorized by their transduction methods, followed by a comprehensive overview of our devices design and fabrication process. Followed by an overview of the performance of our devices under different mounting conditions. Finally, a custom finite difference simulation is presented to determine the limiting factor in our device's performance along with concluding remarks and potential future work.