Title:  Advanced Frequency Output Resonant MEMS Accelerometers

Committee:

Dr. Farrokh Ayazi, ECE, Chair , Advisor

Dr. Levent Degertekin, ECE

Dr. Azadeh Ansari, ECE

Dr. Omer Inan, ECE

Dr. Peter Hesketh, ME

Abstract: MEMS accelerometers are micro-scale devices that measure acceleration of an object with respect to its reference frame. Due to their small size and low cost, MEMS accelerometers have had great success in industrial, automotive and consumer including gesture recognition. However, MEMS accelerometers with extended performance are required by emerging applications like health informatics, robotics, shock measurement, missile guidance, and indoor navigation (or dead reckoning), which are not easily achievable with currently available conventional MEMS accelerometer technology. Therefore, breakthroughs in 3-axis MEMS accelerometer technology are highly desirable. This dissertation mainly focuses on the design and implementation of multi-axis high dynamic range resonant MEMS accelerometers operating in vacuum that sense linear acceleration in wide frequency range (DC - 10 kHz) with high resolution (< 10 micro-g/sqrtHz) by utilizing the electrostatic spring softening effect, or eFM transduction mechanism, and advanced transducers. The design challenges are identified, and the solutions are provided. Especially the physical principles behind temperature stability of the eFM resonant accelerometer is carefully examined and compensation techniques are demonstrated. Additionally, designs and implementations of two piezoelectric resonant accelerometers for two extreme applications are also presented. The first one is piezoelectric eFM accelerometer targeted to have extremely high linear dynamic range (> 180dB). The implemented prototype accelerometer with area changing transduction mechanism and 3D fabrication process demonstrates over 140dB of linear dynamic range. The other is piezoelectric mFM seismometer which requires extremely low noise performance. The implemented mFM seismometer proves the advantage of piezoelectric mFM accelerometer utilizing 3D structure and mechanical force amplifier. The experiments and characterizations performed on the presented resonant accelerometers establish new designs and structures to enable high performance MEMS accelerometer for emerging applications.