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Title: Silicon piezoresistors for MEMS pressure sensor applications
Author: Tan, T. H.
ISNI:       0000 0004 5369 5141
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2014
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Silicon based micromachining technology enables the realization of high performance micro electromechanical systems (MEMS) including a range of physical and environmental sensors. Pressure sensors are used for a wide range of monitoring and control applications, e.g. environmental, industrial, aircraft, automotive. Monitoring of vehicle tyre pressures offers benefits such as improved safety, fuel economy, and tyre life. Micromachined pressure sensors are used at present, but require further research to improve their performance in terms of size, power consumption and manufacturing cost. This thesis has reviews pressure sensor technology and new developments in this area. A comparison of existing and potential future sensing mechanisms has been undertaken and identified as silicon piezoresistors. The focus of the research is motivated by the recently discovered enhanced piezoresistive effect in silicon nanowires where sensitivity can be increased by decreasing the dimension of nanowire. This thesis investigates the piezoresistive effect in p-type <110> silicon nanowires, fabricated using top down approach. It is found that the piezoresistive effect increases when the nanowire width is reduced below 400nm. Compared with micrometre sized piezoresistors, silicon nanowires have produced up to 100% enhancement. In addition, measurements indicate that the temperature coefficient of resistance (TCR) of silicon nanowire has improved with up to 40% decrease in TCR. The improvement in these two areas will be beneficial for the development of new MEMS pressure sensors. COMSOL is employed to simulate the piezoresistance effect in p-type <110> silicon for a range of doping concentrations. Simulation results demonstrate a similar trend to experimental results and publication data and show that the piezoresistance effect decreases as the doping concentration increases.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available