Abstract

This thesis reports, for the first time, on a novel design and architecture for realizing inertial grade gyroscope based on Micro-Electro-Mechanical Systems (MEMS) technology. The proposed device is suitable for high-precision Inertial Navigation Systems (INS). The new design has been investigated analytically and numerically by means of Finite Element Modeling (FEM) of the shapes, resonance frequencies and decoupling of the natural drive and sense modes of the various implementations. Also, famous phenomena known as spring softening and spring hardening are studied. Their effect on the gyroscope operation is modeled numerically in Matlab/Simulink platform. This latter model is used to predict the drive/sense mode matching capability of the proposed designs. Based on the comparison with the best recently reported performance towards inertial grade operation, it is expected that the novel architecture further lowers the dominant Brownian (thermo-mechanical) noise level by more than an order of magnitude (down to 0.08º/hr). Moreover, the gyroscope's figure of merit, such as output sensitivity (150 mV/º/s), is expected to be improved by more than two orders of magnitude. This necessarily results in a signal to noise ratio (SNR) which is up to three orders of magnitude higher (up to 1,900mV/ º/hr). Furthermore, the novel concept introduced in this work for building MEMS gyroscopes allows reducing the sense parasitic capacitance by up to an order of magnitude. This in turn reduces the drive mode coupling or quadrature errors in the sensor's output signal. The new approach employs Silicon-on-Insulator (SOI) substrates that allows the realization of large mass (>1.6mg), large sense capacitance (>2.2pF), high quality factors (>21,000), large drive amplitude (~2-4 µm) and low resonance frequency (~3-4 KHz) as well as the consequently suppressed noise floor and reduced support losses for high-performance vacuum operation. Several challenges were encountered during fabrication that required developing high aspect ratio (up to 1:20) etching process for deep trenches (up to 500 µm). Frequency Response measurement platform was built for devices characterization. The measurements were performed at atmospheric pressures causing huge drop of the devices performance. Therefore, various MEMS gyroscope packaging technologies are studied. Wafer Level Packaging (WLP) is selected to encapsulate the fabricated devices under vacuum by utilizing wafer bonding. Through Silicon Via (TSV) technology was developed (as connections) to transfer the electrical signals (of the fabricated devices) outside the cap wafers.

Department

Nanotechnology Program

Degree Name

MS in Nanotechnology

Graduation Date

2-1-2013

Submission Date

August 2012

First Advisor

Sedky, Sherif

Extent

NA

Document Type

Master's Thesis

Library of Congress Subject Heading 1

Microelectromechanical systems.

Library of Congress Subject Heading 2

Gyroscopes.

Rights

The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.

Institutional Review Board (IRB) Approval

Not necessary for this item

Comments

There are number of people I would like to acknowledge their support, on professiol and social aspects, that without it this work would never be achieved. I would like first to thank my supervisor Prof. Sherif Sedky for the endless knowledge and research skills that he taught me. In addition, I want to state my utmost appreciation for the unmatched support and advisement that he shown during the entire 3-years of the project. Not to mention his tireless efforts to sustain the project funds. This provided state of art facilities in microfarbication which gave the chance for me, and my colleagues, to obtain high tech hands-on experience. Also, I would like to thank Dr. Amro El Shurafa for his precious advises regarding all the aspect related to research from suggesting a research point to writing a technical paper, in addition, to his supervision on modeling the gyroscopes performance. I can't forget Dr. Ahmed Emira's role for supporting me with several ideas that improved the quality of the latter work. I would like to thank my classmate and my friend, Karim Khairallah for helping me verifying the numerical model. I want to send my special thanks and appreciation to Dr. Mohamed Serry for his guidance during the fabrication phase. His patience and understanding made me master the usage of various microfabrication facilities at the American University in Cairo (AUC) clean room. I learned a lot from him as a researcher and as a person. I am very grateful to my best friend Ahmed Kamal, for his during my beginning months at Yousef Jameel Science and Technology Research Center (YJ-STRC). His illustrations regarding the novel gyroscope design was extremely fruitful. Moreover, I would like to thank Dr. Abdelhameed Sharaf for his help in building the characterization setup for the fabricated devices. I want to send my warm regards to my friend Joseph Ernest for his help in setting up the electroplating facility. Special thanks to Mohamed Ibrahim for his endless efforts to sustain the fabrication quality and facilities at the AUC clean room up to the world standards. I want to send my sincerest thanks to King Abdallah Univeristy for Science and Technology for funding the research project and my masters' studies. At last, but not least, I want to send my warm appreciation to my family (parents, brothers, sister, and fiancée) for their endless efforts to provide stable environment at home and for keeping pushing me forward. Everything I am, and will be, is because of them.

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