Design and fabrication of micromachined capacitive accelerometers

This thesis reports the design and fabrication of MEMS based capacitive accelerometers for detection of defective equipment in automotive applications using PolyMUMPs fabrication technology. A design was developed denoting further improvements in accelerometer topologies based on the SOIMUMPs fabrication process. This research obtained accelerometers with sensitivities of 521 fF/mum and 0% cross-axis sensitivities. A prototype with 5 fF/mum sensitivity, 2.05% nonlinearity and an estimated effective bandwidth of 1.858 kHz for 1% response error with mechanical resolutions of 19.3 mug/√Hz was developed. A new approach to accelerometers configuration analysis is introduced, and future design based on this approach was developed to detect accelerations less than +/-25.9 mg with mechanical resolution of 3.45 mug for 1 kHz bandwidth and a readout circuitry of minimum accuracy of +/-4 fF. This work focuses on developing high performance accelerometers and exploring MEMS technology with contributions made to obtain higher performance devices from the fabrication processes.