Micromachined accelerometers have found large attention in recent years due to their low-cost and small size. There are extensive studies with different approaches to implement accelerometers with increased performance for a number of military and industrial applications, such as guidance control of missiles, active suspension control in automobiles, and various consumer electronics devices. This thesis reports the development of various capacitive micromachined accelerometers and various integrated CMOS readout circuits that can be hybrid-connected to accelerometers to implement low-cost accelerometer systems. Various micromachined accelerometer prototypes are designed and optimized with the finite element (FEM) simulation program, COVENTORWARE, considering a simple 3-mask surface micromachining process, where electroplated nickel is used as the structural layer. There are 8 different accelerometer prototypes with a total of 65 different structures that are fabricated and tested. These accelerometer structures occupy areas ranging from 0.2 mm2 to 0.9 mm2 and provide sensitivities in the range of 1-69 fF/g. Various capacitive readout circuits for micromachined accelerometers are designed and fabricated using the AMS 0.8 &micro / m n-well CMOS process, including a single-ended and a fully-differential switched-capacitor readout circuits that can operate in both open-loop and close-loop. Using the same process, a buffer circuit with 2.26fF input capacitance is also implemented to be used with micromachined gyroscopes. A single-ended readout circuit is hybrid connected to a fabricated accelerometer to implement an open-loop accelerometer system, which occupies an area less than 1 cm2 and weighs less than 5 gr. The system operation is verified with various tests, which show that the system has a voltage sensitivity of 15.7 mV/g, a nonlinearity of 0.29 %, a noise floor of 487 Hz &micro / g , and a bias instability of 13.9 mg, while dissipating less than 20 mW power from a 5 V supply. The system presented in this research is the first accelerometer system developed in Turkey, and this research is a part of the study to implement a national inertial measurement unit composed of low-cost micromachined accelerometers and gyroscopes.

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-06Bitstream added on 2014-06-13T20:18:25Z : No. of bitstreams: 1 freitasjr_jl_me_guara.pdf: 1619418 bytes, checksum: c9f600bef1bd4a38f5a6b1437fb62dd6 (MD5) / Universidade Estadual Paulista (UNESP) / Sistemas micro-eletromecânicos (MEMS) é uma tecnologia revolucionária que envolve a miniaturização de componentes e estruturas para a transdução, atuação e controle de sinais, através de interfaces eletrônicas, afetando a forma que pessoas e máquinas interagem com o mundo físico. Este avanço tecnológico é conseqüência da integração de áreas multidisciplinares, que possibilitou o desenvolvimento de componentes de pequenas dimensões, de baixo consumo e operando em diferentes ambientes. O objetivo deste trabalho foi estudar a aplicabilidade de sensores de aceleração tipo capacitivo que utilizam desta tecnologia, visando desenvolver um sistema para monitoramento de sinais de vibração em máquinas rotativas, levando em consideração o custo, a portabilidade e a capacidade de monitoramento de sinais na faixa entre zero e 5kHz. Os resultados foram satisfatórios, alcançando os objetivos propostos. / Micro-electromechanical Systems (MEMS) is a revolutionary technology involving miniaturization of components and structures to transduction, performance and control of signals, through electronic interface, affecting the form that people and machines interact with the physical world. This technologic progress is consequence of the integration of several areas, which made possible the development of devices with small dimensions, requiring low power and able to operate in several environments. The objective of this work was to study the applicability of the capacitive sensor based in this technology, seeking to develop a monitor system for vibration in rotative machines, taking into account the cost, the portability and the capacity of work with frequency between zero and 5kHz. The results were satisfactory, reaching the proposed objectives.

Orientador: Mauro Hugo Mathias / Banca: Sandro Aparecido Baldacim / Banca: João Zangrandi Filho / Resumo: Sistemas micro-eletromecânicos (MEMS) é uma tecnologia revolucionária que envolve a miniaturização de componentes e estruturas para a transdução, atuação e controle de sinais, através de interfaces eletrônicas, afetando a forma que pessoas e máquinas interagem com o mundo físico. Este avanço tecnológico é conseqüência da integração de áreas multidisciplinares, que possibilitou o desenvolvimento de componentes de pequenas dimensões, de baixo consumo e operando em diferentes ambientes. O objetivo deste trabalho foi estudar a aplicabilidade de sensores de aceleração tipo capacitivo que utilizam desta tecnologia, visando desenvolver um sistema para monitoramento de sinais de vibração em máquinas rotativas, levando em consideração o custo, a portabilidade e a capacidade de monitoramento de sinais na faixa entre zero e 5kHz. Os resultados foram satisfatórios, alcançando os objetivos propostos. / Abstract: Micro-electromechanical Systems (MEMS) is a revolutionary technology involving miniaturization of components and structures to transduction, performance and control of signals, through electronic interface, affecting the form that people and machines interact with the physical world. This technologic progress is consequence of the integration of several areas, which made possible the development of devices with small dimensions, requiring low power and able to operate in several environments. The objective of this work was to study the applicability of the capacitive sensor based in this technology, seeking to develop a monitor system for vibration in rotative machines, taking into account the cost, the portability and the capacity of work with frequency between zero and 5kHz. The results were satisfactory, reaching the proposed objectives. / Mestre

Accelerometer sensors fabricated with micromachining technologies started to take place of yesterday&rsquo / s bulky sensors in many application areas. The application areas include a wide range from consumer electronics and health systems to military and aerospace applications. Therefore, the performance requirements extend form 1 &mu / g&rsquo / s to 100 thousand g&rsquo / s. However, high performance strategic grade MEMS accelerometer sensors still do not exist in the literature. Smart designs utilizing the MEMS technology is necessary in order to acquire high performance specifications. This thesis reports a high performance accelerometer with a new process by making the use of bulk micromachining technology. The new process includes the utilization of Silicon-on-Insulator (SOI) wafer and its buried oxide (BOX) layer. The BOX layer helps to realize interdigitated finger structures, which commonly find place in surface micromachined CMOS-MEMS capacitive accelerometers. The multi-metal layered CMOS-MEMS devices inherently incorporate interdigitated finger structures. Interdigitated finger structures are highly sensitive to acceleration in comparison with comb-finger structures, which generally find usage in bulk-micromachined devices, due to absence of anti-gap. The designed sensors based on this fabrication process is sought to form a fully-differential signal interfaced sensor with incorporation of the advantages of high sensitive interdigitated finger electrodes and high aspect ratio SOI wafer&rsquo / s bulk single crystal silicon device. Under the light of the envisaged process, sensor designs were made, and verified using a computing environment, MATLAB, and a finite element analysis simulator, CoventorWARE. The verified two designs were fabricated, and all the tests, except the centrifuge test, were made at METU-MEMS Research Center. Among the fabricated sensors, the one designed for the high performance achieves a capacitance sensitivity of 178 fF with a rest capacitance of 8.1 pF by employing interdigitated finger electrodes, while its comb-finger implementation can only achieve a capacitance sensitivity of 75 fF with a rest capacitance of 10 pF.