Nghiên cứu nâng cao độ nhạy của cảm biến đo vận tốc góc kiểu tuning fork

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY INTERNATIONAL TRAINING INSTITUTE FOR MATERIALS SCIENCE Thesis of graduation IMPROVING THE SENSITIVITY OF MEMS TUNING FORK GYROSCOPE STUDENT: HA SINH NHAT ADVISORS: Dr CHU MANH HOANG Assoc Prof Dr VU NGOC HUNG Hanoi, April 2015 Improving the sensitivity of MEMS tuning fork gyroscopes i DEDICATION This thesis is submitted for International Training Institute for Material Science in Ha Noi University of Science and Technology The work has been carried out in International Training Institute for Material Science, Number 1, Dai Co Viet, Ha Noi, VietNam since October 2012 Except where specific references are made, this thesis is entirely the result of my own work and includes nothing that is the outcome of work done in collaboration No part of this work has been or being submitted for any other degree, diploma or qualification at this or any other university Author Ha Sinh Nhat ii ACKNOWLEDGEMENT This thesis is the result of my two years study in ITIMS where I am trained in the field of materials science with the best study conditions, taken part in exciting and interesting scientific seminars of both MEMS group and study class I would like to say that the obtained results are due to the help of all the members in ITIMS without this help I think that it would be difficult for me to reach this final Foremost among them are my supervisors Dr Chu Manh Hoang and Assoc Prof Dr Vu Ngoc Hung I would like to express my special thanks to them for many things they had done for me, including their personal and professional guidance, encouraging support, and for creating very good research environment I wish thank Assoc Prof Dr Chu Duc Trinh, Msc Dang Van Hieu for his friendly guidance and for co-examining this thesis I would like to thank all members of MEMS group, Msc Nguyen Quang Long, and the other members who created friendly research environment and shared experiences in practical work I would also like to thank sincerely to all the teachers who teach me during time I am studying at ITIMS such as Assoc Prof Dr Nguyen Van Hieu, Assoc Prof Dr Nguyen Phuc Duong, Assoc Prof Dr Nguyen Anh Tuan, Dr Nguyen Van Quy…, kind librarian Nguyen Phuong Loan and other ITIMS staffs Finally, at home, I am indebted with my family for their love, and continuous encouragement over the past several years Ha Noi, April 2015 Ha Sinh Nhat iii CONTENTS DEDICATION ii ACKNOWLEDGEMENT iii CONTENTS iv LIST OF FIGURES .vi LIST OF TABLES x Chapter INTRODUCTION 1.1 The MEMS technology 1.2 MEMS tuning fork gyroscopes 1.2.1 The operation principle of gyroscope 1.2.2 The dynamic characteristics of gyroscope 1.2.3 Tuning fork gyroscopes 11 1.3 Recent developments in improving the sensitivity of tuning fork gyroscope 13 1.3.1 Operation matching of sense and drive modes 13 1.3.2 Improving structure 17 1.3.3 Decreasing damping 20 1.4 Purpose of this thesis 24 Chapter DESIGNS OPTIMIZATION OF TUNING FORK GYROSCOPE 27 2.1 Tuning Fork Gyroscope structure analysis methods 27 2.2 The 10 kHz resonant operation Tuning Fork Gyroscope 28 2.2.1 Structural construction and modal analysis 28 2.2.2 Sense displacement simulation 33 2.3 The 10 kHz version advantage and disadvantage points 35 2.4 The focus point in Tuning Fork Gyroscope optimization: 36 2.4.1 Frequency reduction and proof masses selection 38 2.4.2 The sensing energy arrangement 39 2.4.3 The device thickness selection 40 iv 2.5 Simulation result comparison of two sensor versions 41 2.5.1 Structural properties comparison 43 2.5.2 Angular rate sensitivity 45 2.5.3 Slide damping reduction 49 Chapter FABRICATION PROCESS AND MEASUREMENT 55 3.1 Mask design 55 3.2 Fabrication flow 59 3.3 Packaging 62 3.4 Experimental measurement 64 3.4.1 Frequency response measurement block diagram 64 3.4.2 Characteristic measurement block diagram 66 Chapter RESULTS AND DISCUSSION 69 4.1 Results of gyroscope fabrication 69 4.2 Results of package 71 4.3 Results of characteristics measurement 72 CONCLUSION 75 FUTURE WORK 78 LIST OF THESIS PUBLICATION 79 REFERENCES 80 v LIST OF FIGURES Figure 1.1: MEMS devices application in automobile industry Figure 1.2: Coriolis acceleration concept Figure 1.3: A generic MEMS implementation of a linear vibratory rate gyroscope [1] Figure 1.4: A mass-spring-damper gyroscope lumped model Figure 1.5: Lumped mass-spring-damper resonator model Figure 1.6: The scanning electron micrograph images of the first working prototype tuning fork gyroscope from the Draper Laboratory (a), The high-Q in-plane SOI tuning fork gyroscope from Georgia Institute of Technology (b), and the micromachined gyroscope with high shock resistance from Tongji University (c) 12 Figure 1.7: Amplitude-frequency response of a 1-DOF drive-mode oscillator and a 1DOF sense-mode oscillator 16 Figure 1.8: Design model of lateral micromachined tuning fork gyroscope: (1) outer mass frame, (2) inner mass frame, (3) drive comb electrodes, (4) sense electrodes, (5) folded beam, (6) anchor, (7) lozenge-shaped coupling spring, and (8) self-rotation ring [8] 19 Figure 1.9: Optical photograph of a vacuum packaged tuning fork gyroscope, showing the die, the ceramic package, the glass lid with getter material and metal sealing ring, and structural schematic of the gyroscope architecture [11] 22 Figure 2.1:MEMS TFG 10 kHz version without drive and sense combs (1-Drive comb frame; 2-Sense beam, 3-Drive beam; 4-Sense comb frame; 5-Lozenge shape’s beam; 6Self-rotate ring; 7-Constrain beam; 8-Connecting beam; 9-Anchor; 10-Drive outer frame; 11-Sense frame) 29 Figure 2.2: Deformation of the anti-phase drive and sensing modes of 10 kHz TFG (a) sense mode (b) drive mode 31 vi Figure 2.3:The parasitic modes of 10 kHz TFG version: mode 3rd to mode 6th (a) anti phase x-axis outer frame warp mode; (b) in phase x-axis outer frame warp mode; (c) in phase drive mode; (d) in phase x-axis twist mode 32 Figure 2.4: The parasitic modes of 10 kHz TFG version: mode 7th to mode 10th (a) anti phase x-axis twist mode; (b) anti phase y-axis inner frame twist mode; (c) in phase yaxis inner frame twist mode; (d) in phase sense mode 33 Figure 2.5: The sense displacement versus rotation velocity 34 Figure 2.6: The self-rotate ring increases its radius and changes from constrain beams (a-10 kHz TFG) into beams (b-4.5 kHz TFG) 40 Figure 2.7: The dependence of 10 first order natural frequencies on the thickness of 10 kHz TFG 41 Figure 2.8: Drive modes of 10 kHz TFG version (a) and 4.5 kHz TFG version (b) 44 Figure 2.9: Sense modes of 10 kHz TFG version (a) and 4.5 kHz TFG version (b) 44 Figure 2.10: The dependence of TFG’s resonant drive amplitude on the drive force frequency with Ω=10rad/s (a) 10 kHz TFG and (b) 4.5 kHz TFG 46 Figure 2.11: The dependence of TFG’s resonant drive amplitude on the drive force frequency with Ω=10rad/s (a) 10 kHz TFG and (b) 4.5 kHz TFG 47 Figure 2.12: The sense displacement of 10 kHz TFG and 4.5 kHz TFG calculated as function of the input angular velocity (Ω) 47 Figure 2.13: Capacitance change versus introduced angular velocity 48 Figure 2.14: Schematic of freestanding MEMS tuning-fork gyroscope 50 Figure 2.15: The dependence of sense displacement versus drive force frequency of (a) 10 kHz TFG and (b) 4.5 kHz TFG for non-freestanding and freestanding versions with angular rate of 10 rad/s 53 Figure 2.16: The dependence of sense displacement versus angular rate of (a) 10 kHz TFG and (b) 4.5 kHz TFG for non-freestanding and freestanding versions 54 Figure 3.1: Positive mask design of complete gyroscope with Clewin software 55 vii Figure 3.2: TFG 10 kHz sensor mask design with drive comb and sense comb structures (Positive mask on Clewin software) 58 Figure 3.3: The 4.5 kHz TFG mask design with holes, drive combs and sense combs structure (Negative mask on AutoCAD software) 58 Figure 3.4: The 4.5 kHz TFG Chromium on glass mask for photolithography technique 59 Figure 3.5: Silicon etching profile with Bosch process 60 Figure 3.6: Fabrication process for TFG non-free standing (a) and freestanding (b) TFG sensor 61 Figure 3.7: Westbond Ultrasonic weld wire bonding machine (a) and tip motions in welded process (b) 63 Figure 3.8: The diagram of actuation and sense electrodes for wire circuitry interconnection between gyroscope and PCB (1-Proof mass to VDC connecting terminal, 2-Proof mass to VAC connecting terminal, 3-Sensing capacitor Cs+ terminal, 4-Proof mass for sensing capacitor terminal; 5- Sensing capacitor Cs- terminal) 63 Figure 3.9: Two-port actuation and detection scheme for measuring the natural frequency of gyroscope 65 Figure 3.10: One-port actuation and detection scheme for measuring the natural frequency of gyroscope 66 Figure 3.11: The angular rate detection scheme for gyroscope with MS3110-All capacitance read out IC 67 Figure 3.12: The block diagram of gyroscope characterize system 68 Figure 4.1: SEM images of fabricated 10 kHz and 4.5 kHz TFG sensor: entire of structure (a), (b); self-rotation ring and Lozenge beams (c), (d), folded beam connecting driving and sensing mass frame (e), and zoom-in sense comb-fingers (f) 70 Figure 4.2: Back side image of (a) 10 kHz and (b) 4.5 kHz version with unreleased oxide layer 71 viii Figure 4.3: Gyroscope interconnection circuit and its package 72 Figure 4.4: The dependence of sensor output voltage versus applied VDC with a constant angular rate 73 Figure 4.5: Output voltage of the 10 kHz tuning fork gyroscope measured as a function of input angular rate 74 ix oscillates with tens of microns amplitude in the drive-mode Then, a capacitance to voltage converter is connected to the sense capacitor electrodes and amplifies the differential sensing signal Commercial MS3110-All capacitance readout board has been used for this case (circuit in dashed box) It’s preferred C-V readout product Figure 3.11: The angular rate detection scheme for gyroscope with MS3110-All capacitance read out IC 67 because its stability and femtofarad range detect ability It includes a switchedcapacitor integrator circuit, which consists of a charge amplifier, low-pass filter, and a buffer for amplification It outputs a voltage that is proportional to the change in capacitance Figure 3.12: The block diagram of gyroscope characterize system 68 Chapter RESULTS AND DISCUSSION 4.1 Results of gyroscope fabrication These sensors were fabricated in a SOI wafer having 20m, 30 m, 40 m and 50 m thick device layer and m buried oxide layer The DRIE etching process was carried out at Tohoku University – Japan and the HF-vapor releasing process was carried out at ITIMS-HUST The gyroscope structures after fabrication are characterized by SEM images Fig 4.1 shows the structure overview of both gyroscope versions (10 kHz TFG and 4.5 kHz TFG) and their detail structures The microimages show that the DRIE process has been done well The edges are well-defined and not broken or damaged in structures and sensing electrodes The small and large gaps of sensing comb are m and 7.5 m, which are suitable with designed values As shown in Fig 4.2, the back side etching results of freestanding models is completely reached to oxide layer When the oxide layer is removed, freestanding gyroscope is achieved An addition of Au layer in each electrode is finally deposited; it increases the quality of interconnection between sensors to outside electric circuits 69 Figure 4.1: SEM images of fabricated 10 kHz and 4.5 kHz TFG sensor: entire of structure (a), (b); self-rotation ring and Lozenge beams (c), (d), folded beam connecting driving and sensing mass frame (e), and zoom-in sense comb-fingers (f) 70 Figure 4.2: Back side image of (a) 10 kHz and (b) 4.5 kHz version with unreleased oxide layer 4.2 Results of package Fig 4.3 shows the packaging result of fabricated sensors The fabricated gyroscope is wired with combination of comb drive frames into only one electrode that is used to connect to AC input terminal; and proof masses is connected to DC input terminal This electronic wiring model allows the sensor to drive into its resonance state without inverse-phase electronic circuit that can reject the phase-shift between the proof masses of tuning fork gyroscope The sense comb frames that have the same capacitance change are connected to create only one pair of differential capacitor Finally, the gyroscope is packaged in air inside a box to protect it from dust and external environment effects The fabrication process of the gyroscope is completed for investigating its operation characteristics 71 Figure 4.3: Gyroscope interconnection circuit and its package 4.3 Results of characteristics measurement According to section 3.4, the fabricated gyroscopes are characterized with frequency response and angular rate measurement There is only 10 kHz freestanding gyroscope that has been tested in this time The first test is the natural frequency response of the gyroscope With the frequency response test, a VDC is imposed onto the proof mass and a VAC in amplitude signal from Network Analyzer is applied on one comb drive side, the amplified signal from another side is connected into Network Analyzer input The resonant frequency of this sensor is 11125 Hz and 11108 Hz for drive-mode and sensemode respectively These results are reasonable because number of holes and comb fingers have been added to the real structure in comparison with simulation model To verify the sensor natural frequency, an addition test has been applied with gyroscope is the dependence of sensor output voltage on frequency of applied VAC, in case of constant angular rate For the 10 kHz gyroscope, driving voltages are VAC and VDC, and the angular rate is constant at 60˚/s, the relationship between the sensor 72 output voltage and VAC frequencies is shown in Fig 4.4 The result gives the maximum output voltage at the drive frequency of 11.12 kHz This value is appropriate with the previous natural frequency measured by Network Analyzer The experimental obtained natural frequency is 11.2% higher than the simulation result might rise from the fabrication deviation and the damping effect had been reduced from sensor’s backside remove Figure 4.4: The dependence of sensor output voltage versus applied VDC with a constant angular rate From the obtained natural frequency value, the second test – angular rate measurement is performed For this test, a VDC is applied on the proof mass and 5VAC amplitude with frequency in the range of 11108 Hz to 11125 Hz The MS 3110 circuit board is set up a 1pF capacitance in the input that gives 1mV in output change While the servo motor is controlled to give angular rate change in the range from 0-200 73 deg/s, the output sense response of 10 kHz gyroscope is shown in Fig 4.5 The sensitivity of the 10 kHz sensor is obtained to be 4.39e-4 V/deg/s The measurement results also show that the sensor gives linearity output voltage characteristic over the angular rate range from -200 deg/s to 200 deg/s Figure 4.5: Output voltage of the 10 kHz tuning fork gyroscope measured as a function of input angular rate 74 CONCLUSION The thesis presents about improving the sensitivity of the MEMS tuning fork gyroscope By considering the methods for improving the sensitivity of gyroscope introduced in literature, a MEMS gyroscope with robustness and improved sensitivity is modeled and simulated by finite element method using ANSYS software The design of the gyroscope is improved by optimizing its mechanical structure that is solved by simulation result and compared with the un-improved gyroscope version The initial experiment results in investigating the operation characteristics of the gyroscope are also carried out in this thesis The main achievements in this thesis are summarized as follows Besides satisfying the requirements of a tuning fork gyroscope such as frequency matching condition, prioritized anti-phase driving and sensing modes, and low noise, the operation frequency of current gyroscope is reduced from 10 kHz (in the previous design) to 4.5 kHz The gyroscope resonant frequency has been changed by verifying six outside driving beams, four U-shaped sense beams between outer and inner rectangle frames The sensor proof masses have been adjusted by elongates inner frames and slightly widening outer frames For the new 4.5 kHz TFG design, the stiffness of the centered self-rotate ring is decreased by increase its radius and retain constrain beams in comparison with beams of previous gyroscope (10 kHz TFG version) From the modal analysis result, the 4.5 kHz TFG has the difference between operating mode frequencies and the parasitic modes are 57.3% (5614 Hz) and 138.3% (6025 Hz) in the 10 kHz TFG and 4.5 kHz TFG, respectively Hence, the new gyroscope has got better mechanical properties Although the 4.5 kHz TFG’s in-phase sense frequency has strongly decreased compared with 10 kHz TFG, but still satisfied far apart of 12237 Hz to operating frequencies So, the 4.5 kHz sensing anti-phase structure component is already maintained a properly feature 75 From harmonic analysis result, with 11 VDC and 10 VAC have been applied, the resonant drive oscillation amplitude of the 10 kHz TFG is 6.035 μm and that for the 4.5 kHz TFG is 8.724 μm Therefore, the 4.5 kHz TFG can be forced by a smaller driving voltages than 10 kHz TFG but still get the same desired vibratory amplitude At similar operating amplitude and the same mode-matched of 27 Hz, the sense displacement of 4.5 kHz TFG is 169.17 nm, 11% higher in comparison with 10 kHz TFG sense displacement of 151.89 nm The slope of sensing displacement linear fit line of 10 kHz TFG version is 10.48 nm/rad/s, while this value of 4.5 kHz TFG is 11.43 nm/rad/s They can be considered as gyroscope’s mechanical sensitivity Since, the 4.5 kHz TFG’s sensitivity has been improved compare with 10 kHz TFG version just by structure mechanical optimization The TFG sensing capacitance change was also calculated from angular rate measurement simulation result When the VAC=10 V, VDC=11 V, and Ωz=10rad/s, the sense capacitance change of one sense frame in 4.5 kHz TFG is 51.74 fF, higher than that of 10 kHz TFG, is 29.16 fF The 4.5 kHz TFG sensitivity is 5.17 fF/rad/s, higher than this value of 2.92 fF/rad/s of 10 kHz version, which corresponds to the sensitivity is increased of 77% for 10 rad/s input angular velocity Because of the gyroscope is presented in this thesis which is an air packaged sensor Hence, it should be considered as a heavy damped resonator, inside of surrounding air viscosity To obtain a large Coriolis force and a detectable signal in the sense mode, to keep designed gyroscopes are much sensitive operation in air condition, the damping effect must be reduced For this gyroscope design, both driving mass and sensing mass are designed to vibrate in parallel to the silicon substrate Then, the slide damping by the air gap between them is the dominant damping factor By removing a part of silicon substrate underneath the moving structure (freestanding TFG), the slidefilm damping is reduced so the both driving and sensing modes Quality factor 76 increasing can be The damping ratio of 10 kHz TFG free-standing version is 0.0064 as 13.5% reduced as non-freestanding version (non removed substrate version) With 4.5 kHz TFG, the freestanding version damping coefficient is 0.0165 which 12.2% reduced compare with non-freestanding one The optimally designed gyroscopes were fabricated for characterizing experiments The mask designs for gyroscope versions (non-optimal and optimized gyroscope) were completed using AutoCAD and Clewin software The “Chromium on glass” masks were generated using laser drawing machine There are two addition gyroscope versions with backside etching for decreasing air damping effect which have been fabricated too After that, gyroscope prototypes have been wired to printed circuit board by Aluminum wires using ultrasonic wire bond Finally, the devices are packaged in air-condition box for protection A measurement system is set up for investigating the operation characteristics of the fabricated gyroscope The initial experiment results are performed on the 10 kHz free-standing (backside removed) gyroscope The resonance frequency of freestanding gyroscope designed for operating at 10 kHz free-standing TFG is 11.12 kHz The linearity of sensor output voltage over the angular rate range of -200 deg/s to 200 deg/s is achieved, and its sensitivity is 4.39x10-4 V/deg/s 77 FUTURE WORK The initial experiment results are investigated for the 10 kHz freestanding TFG, the other fabricated gyroscopes such as the 4.5 kHz and 10 kHz non-freestanding and the 4.5 kHz freestanding gyroscope have not been characterized Therefore, the measurement characteristics comparison of un-optimal gyroscopes prototype with optimized version has not been performed yet The future works are completing total measurement for these three remaining gyroscope versions to figure out all optimization work result Furthermore, the electronic processing circuit embedded for gyroscope prototype will be developed in aim 78 LIST OF THESIS PUBLICATION Hung Vu Ngoc, Nhat Sinh Ha, Long Quang Nguyen, Dzung Viet Dao and Hoang Manh Chu, “Design and Analysis of an Intergrated 3-DOF Sensor for Tracking in-Plane Motion”, Proceeding of International Conference on Control, Automation and Information Sciences (ICCAIS), Vietnam, pp 68-72, 2013 Ha Sinh Nhat, Chu Manh Hoang, Nguyen Quang Long, and Vu Ngoc Hung,“ Improving the sensitivity of Z-axis Tuning Fork gyroscope by optimizing its structure”, Advances in applied and engineering physics, Vietnam, pp 111-117, 2014 Nguyen Quang Long, Ha Sinh Nhat, Nguyen Ngoc Minh, Chu Manh Hoang, and Vu Ngoc Hung, “Design And Simulation Of Freestanding Mems Tuning Fork Gyroscope Having Sensitivity Improved By Reducing Air Friction”, Journal of Science & Technology Technical Universities, Vietnam, pp 70-74 2014 Nguyen Quang Long, Nguyen Ngoc Minh, Ha Sinh Nhat, Trinh Quang Thong, Chu Manh Hoang, Vu Ngoc Hung, “Design Optimization of MEMS Z-axis Tuning Fork Gyroscope”, Advanced Materials and Nanotechnology ICAMN-2014, Vietnam, pp 397-402, 2014 79 REFERENCES [1] Acar C, Shkel A (2009) MEMS Vibratory Gyroscopes Structural Approaches to Improve Robustness Springer Science + Business Media, LLC, USA [2] P Greiff, B Boxenhorn, T King, and L Niles.Silicon monolithic micromechanical gyroscope.Tech Dig 6th Int Conf Solid-State Sensors and Actuators (Transducers’91), SanFrancisco, CA, June 1991, pp 966-968 [3] J Bernstein, S Cho, A T King, A Kourepenis, P Maciel, and M.Weinberg.A micromachinedcomb-drive tuning fork rate gyroscope Proc IEEE Microelectromechanical Systems, FortLauderdale, FL, Feb 1993, pp 143-148 [4] Lutz M, Golderer W and Gerstenmeier J 1997 A precisionyaw rate sensor in silicon micromachining Solid StateSensors and Actuators, Transducer’97 vol pp 847–50 [5] Sharma A, Zaman F M and Amini B V 2004 A high-Qin-plane SOI tuning fork gyroscope Proc IEEE 467–70 [6] Zhou J, Jiang T, Jiao J W, Wu M, Design and fabrication of a micromachined gyroscope with high shock resistance.Microsyst Technol 2013, in press [7] Wang R, Cheng P, Xie F, Young D, Hao Z (2011) A multiple-beam tuning-fork gyroscope with high quality factors Sen Actuators A: Physical 166: 22–33 [8] Weinberg MS, KourepenisA (2006) Error sources in in-plane silicon tuning fork MEMS gyroscopes J Microelectromech Syst 15: 479–491 [9] B.L Lee, Y.S Oh, et al , A Dynarmcally Tuned Vibratory Micromichanical Gyroscope and Accelerometer, SPIE 1997, Dec [10] Trusov AA, Schofield AR, Shkel AM (2011) Micromachined rate gyroscope architecture with ultra-high quality factor and improved mode ordering Sen Actuators A: Physical 165: 26–34 [11] Trusov AA, Schofield AR, Shkel AM (2008) A substrate energy dissipation mechanism in in-phase and anti-phase micromachined z-axis vibratory gyroscopes J Micromech Microeng 18: 095016 (10pp) 80 [12] Sharma A, Zaman FM, Ayazi F (2009) A sub-0.2o/hr bias drift micromechanical silicon gyroscope with automatic CMOS mode-matching IEEE J of Solid-State Circuits, 44: 1593-1608 [13] Yoon SW, Lee S, Najafi K (2012) Vibration-induced errors in MEMS tuning fork gyroscopes Sen Actuators A: Physical 180: 32-44 [14] Geen JA, Sherman SJ, Chang JF, Lewis SR (2002) Single-chip surface micromachined integrated gyroscope with 50°/h Allan deviation IEEE J of Solid-State Circuits, 37: 1860-1866 [15] T Q Trinh, L Q Nguyen, D V Dao, H M Chu, H N Vu, Design and analysis of a z‑axis tuning fork gyroscope with guided‑mechanical coupling, MicrosystTechnol (2014) 20:281–289 [16] Park K Y, Jeong H S, An S, Shin S H, and Lee C W, Lateral gyroscope suspended by two gimbals through high aspect ratio ICP etching, Proc, IEEE 1999 Int Conf on Solid State Sensors and Actuators (Tranducers ’99), Sendai, Japan, June 1999, pp 972-975 [17] Jong-Seok Kim, Sang-Woo Lee, Kyu-Dong Jung, Woon-Bae Kim,Sung-Hoon Choa, Byeong-Kwon Ju, Quality factor measurement of micro gyroscope structure accordingto vacuum level and desired Q-factor range package method, Microelectronics Reliability 48 (2008) 948–952 [18] A Duwel, M Weinstein, J Gorman, J Borenstein, P Ward Quality Factors of MEMS Gyros and the Role of Thermoelastic DampingInternational Conference on Micro Electro Mechanical Systems, 2002 Las Vegas, NV, January 2002, pp 214219 [19] C Zener, Internal Friction in Solids II General Theory of Thermoelastic Internal Friction Physical Review, 1938 Vol 53, pp 90-99 [20] A Lateral-Axis Microelectromechanical Tuning-Fork Gyroscope With Decoupled Comb Drive Operating at Atmospheric Pressure, Journal of Microelectromechanical Systems, Vol 19, No 3, June 2010, pp 458- 468 81 ... 24 Chapter DESIGNS OPTIMIZATION OF TUNING FORK GYROSCOPE 27 2.1 Tuning Fork Gyroscope structure analysis methods 27 2.2 The 10 kHz resonant operation Tuning Fork Gyroscope 28 2.2.1... [8] In the development of the tuning fork gyroscope, our research group has also established a compact tuning fork gyroscopes design The schematic of the designed tuning fork is shown in Fig 1.8... electron micrograph images of the first working prototype tuning fork gyroscope from the Draper Laboratory (a), The high-Q in-plane SOI tuning fork gyroscope from Georgia Institute of Technology