Wafer-level vacuum-encapsulated ultra-low voltage tuning fork MEMS resonator

Date of Award

2017

Degree Name

M.S. in Electrical Engineering

Department

Department of Electrical and Computer Engineering

Advisor/Chair

Advisor: Vamsy Chodavarapu

Abstract

In this thesis, a low-voltage 32 kHz silicon tuning fork MicroElectroMechanical Systems (MEMS)-based resonator design with a high Quality factor of over 73,000 is presented with a Complementary Metal-Oxide Semiconductor (CMOS) sustaining amplifier towards a low power oscillator. The resonator is designed using MEMS Integrated Design for Inertial Sensors (MIDIS) process developed by Teledyne DALSA Semiconductor Inc. (TDSI). MIDIS offers wafer-level vacuum encapsulation with ultra-low leak rate. Ultra-low polarization voltage, as low as 10mV, is needed to excite the resonator by using a transduction gap reduction technique based on electrostatic deflection of movable electrodes and subsequent localized melting of welding pads for permanent position locking. Further, the technique helps to minimize unexpected electrostatic stiffness induced by time-varying capacitance across transduction gaps to just -0.6 N/m. The motional resistance drops down to about 2k& as a result of a small gap size and the technique helps to improve the Quality Factor (Q). A sustaining amplifier using a transimpedance operational amplifier configuration is system-integrated with the tuning fork resonator to establish continuous oscillation with low damping losses. An average power consumption of around 600æW is measured on the oscillator, which is suitable for mobile electronic systems.

Keywords

Resonators Design and construction, Microelectromechanical systems, Electrical Engineering, MEMS-based tuning fork resonator, MIDIS process, 32 kHz oscillator circuit, transduction gap reduction technology

Rights Statement

Copyright © 2017, author

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