Thermally-actuated piezoresistively-sensed mechanical silicon oscillator
Name
880418015-MIT.pdf
Description
Full printable version
Size
7.44 MB
Format
Adobe PDF
Checksum (MD5)
e8500a4100f7c4675e36135ded919e86
Author(s)
Sundaram, Subramanian, Ph. D. Massachusetts Institute of Technology
Advisor(s)
Dana Weinstein.
Date Issued
2014
Publisher
Massachusetts Institute of Technology
Abstract
In the past two decades, Microelectromechanical (MEMS) resonators have emerged as front runners for RF front-ends, high frequency filters, and frequency sources in various applications. The prospect of seamless integration with CMOS has provided a significant boost to displace Quartz, which for long has been the go-to option for timing sources. To construct an oscillator, a MEMS resonator is operated with an active feedback amplifier, the design of which can be a major challenge at high frequencies. In this work we implement a self sustaining mechanical Si oscillator that has an internal feedback mechanism. The oscillator is based on a thermal actuation mechanism due to the Joule heating effect caused by running currents through narrow channels. These narrow channels when oriented along the <100>direction in an n-doped Si wafer, show large negative piezoresistance coefficients. Beyond significant threshold DC current densities (GA/m 2 ), the thermal-actuation and piezoresitive-feedback loop excite the mechanical structure, causing spontaneous oscillations. We begin with the investigation of scaling trends based on an equivalent circuit model of the device. Targeting high frequency oscillators, we design suitable geometries and discuss the microfabrication processes used to fabricate these devices. Finally, we report the experimental results of the fabricated devices.
Description
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-78).
Subjects
Electrical Engineering and Computer Science.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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