EEL6935 Advanced MEMS 2005 H. Xie 1

Lecture 10Agenda:

Integrated Gyroscopes

Term Project

2/11/2005

EEL6935 Advanced MEMS (Spring 2005) Instructor: Dr. Huikai Xie

EEL6935 Advanced MEMS 2005 H. Xie 2

Vibratory Gyroscopes – Topology I

Ωy

Ωz

yd

xs Ωx,s

Anchor

Ωz,d

Coriolis force

External rotation

Excitation

Single Mass with Coupled Modes

Translational Torsional

EEL6935 Advanced MEMS 2005 H. Xie 3

ys

xd

Ωz

Ωx,d

Ωy

xs

xs

Single Mass with Decoupled Modes

Translational Torsional

Vibratory Gyroscopes – Topology II

EEL6935 Advanced MEMS 2005 H. Xie 4

xdxd

Ωy

zszs

ys

xd

Ωz

xd

ys

Dual Mass with Coupled Modes

Dual Mass with Decoupled Modes

Vibratory Gyroscopes – Topology III

EEL6935 Advanced MEMS 2005 H. Xie

Commercial MEMS Gyroscopes

Analog Devices, Inc. Robert Bosch Corp.

Dual Mass with Decoupled Modes

Single Mass with Coupled Modes

EEL6935 Advanced MEMS 2005 H. Xie

Commercial MEMS Gyroscopes

Silicon Sensing System• Joint venture between Sumitomo and BAE Systems

• Ring resonator• Magnetic core

Systron Donner (BEI)Piezoelectric quartz tuning fork

BEI GYROCHIP QRS11

SensoNor (Infineon)Piezoelectric quartz tuning fork

EEL6935 Advanced MEMS 2005 H. Xie

Commercial MEMS IMU

Honeywell

17.25 cu. in.

http://content.honeywell.com/dses/assets/datasheets/mems_presentation.pdfEEL6935 Advanced MEMS 2005 H. Xie 8

CMOS-MEMS Gyroscopes

Translational Vibration

– Polysilicon structures

– Multilayer thin-film structures

– Single-crystal silicon structures

Rotational Vibration

Vibrating Ring

H. Xie and G.K. Fedder, “Integrated MEMS Gyroscopes,” Journal of Aerospace Engineering, Vol. 16 (2003), No. 2, pp. 65-75

EEL6935 Advanced MEMS 2005 H. Xie 9

CMOS-MEMS Gyro: Poly-Si

• Z-axis gyro; Translational oscillation; Polysilicon Structure• Single mass with coupled excitation and sensing• Noise floor: 1°/s/rtHz; Drive mode: 12 kHz• Analog Devices, Inc.’s iMEMS technology • [Clark 96]

Comb fingersfor sense

Spring beamfor sense

Spring beamfor drive

Comb fingersfor drive

Drive mode

Sense mode

1mm by 1 mm

EEL6935 Advanced MEMS 2005 H. Xie 10

CMOS-MEMS Gyro: Poly-Si

• Z-axis gyro; Translational vibration; Polysilicon structure• Single mass with decoupled drive and sense• Parallel-plate actuation; Digital Output• Sandia iMEMS• Noise floor: 3°/s/rtHz• [Jiang 2000]

Drive spring

Sense spring

Sensecomb fingers

Drive comb fingers

0.7mm by 0.8mm by 2.25 µm

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CMOS-MEMS Gyro: Poly-Si

• Z-axis gyro; Translational vibration; Polysilicon structure• Single mass with decoupled drive and sense; Sandia iMEMS• Double-ended tuning fork (DETF)• DETF resonant frequency changes with axial stress induced by

Coriolis force; DETF amplifies Coriolis force• Noise floor: 0.3°/s/rtHz [Seshia 2000]

1.2mm by 1.2mm by 2.25 µmAnchor

DETFDETF

Sense detection

Drive flexure

Outer frame

Frame suspension Lever

arm

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CMOS-MEMS Gyro: Poly-Si

Dual-resonator gyroscope

BiCMOScircuits

• Z-axis gyro; Translational vibration; 4 µm Polysilicon structure• Dual mass with decoupled drive and sense; ADI iMEMS• Impedance-controlled FET for sense node bias• Drive mode: 15 kHz; Q = 45• Noise floor: 0.05°/s/rtHz • [Geen 2002]

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CMOS-MEMS Gyro: Al/Oxide

y-axis accelerometer

sensecomb fingers

y-axis spring

z-axis spring

drivecomb fingers

curl matching frame

y

z x

• X-axis gyro; Translational vibration; Multi-layer structure• Single mass with decoupled drive and sense; Post-CMOS MEMS• Vertical comb drive; Curl matching; Thin z-spring• Drive mode: 5 kHz• Noise floor: 0.5°/s/rtHz [Xie 2001]

0.8mm by 0.6mm by 5 µm

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CMOS-MEMS Gyro: Cu/Oxidesense spring drive spring

anchor

drive fingers

sense fingers

Coriolis acceleration sense direction

drive direction

decoupling frame

• Z-axis gyro; Translational vibration; Multi-layer structure• Single mass with decoupled drive and sense; Post-CMOS MEMS• Drive mode: 8.8 kHz• Noise floor: 0.5°/s/rtHz [Luo 2002]

0.4mm by 0.3mm by 8 µm

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CMOS-MEMS Gyro: Bulk Silicon

sensespring

drivespring

drivecombfingers

sensecombfingers

z-axisaccelerometer

comb fingers for vibration control

y

zx

decoupling frame

• X-axis gyro; Translational vibration; Bulk Si structure• Single mass with decoupled drive and sense• DRIE Post-CMOS MEMS; Electrical isolation of Si• Vertical comb sensing; Thin z-spring• Noise floor: 0.02°/s/rtHz [Xie 2002]

1mm by 1mm by 60 µm

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CMOS-MEMS Gyro - Torsional

• Lateral-axis gyroscope• Dual-axis sensing• Torsional excitation and sensing• [Juneau 97]

• Dual-axis gyro; Torsional vibration; Polysilicon structure

• Single mass with coupled torsional drive and sense; Post-CMOS MEMS

• Drive mode: 28 kHz; Electrostatic tuning for mode matching

• Noise floor: 0.3°/s/rtHz [Juneau 97]

Rotor: φ300µm; 2µm thick

EEL6935 Advanced MEMS 2005 H. Xie 17

CMOS-MEMS Gyro – Vibrating Ring

Delco’s metal ring gyroscope [Sparks 1999]

Anchor

Vibrating ring

Electrodes for actuation and sense

Suspension flexure

v: velocityFc: Coriolis force

nodalpoint

vFc

Fc

v

Fc v

Fcv

Ω

• Z-axis gyro; Vibrating ring• 45° ring vibrating modes; Post-CMOS MEMS• Electroplating metal• Noise floor: 0.1°/s/rtHz

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CMOS-MEMS Gyroscopes: References

[Clark 96] W.A. Clark, R.T. Howe, R. Horowitz, “Surface micromachined Z-axis vibratory rate gyroscope”, Tech. Digest. Solid-State Sensor and Actuator Workshop, Hilton Head Island, SC, USA; 3-6 June 1996, pp.283-287.

[Geen 2002] J.A. Geen, S.J. Sherman, J.F. Chang and S.R. Lewis, “Single-chip surface-micromachining integrated gyroscope with 50 deg/hour root Allan variance”, The 2002 IEEE International Solid-State Circuits Conference, San Francisco, CA, Feb. 3-7, 2002, pp.426-427.

[Juneau 97] T. Juneau, A.P. Pisano, J.H. Smith, “Dual axis operation of a micromachined rate gyroscope”, Tranducers’ 97, Chicago, IL, USA; 16-19 June 1997, pp.883-886.

[Jiang 2000] Xuesong Jiang ; Seeger, J.I.; Kraft, M.; Boser, B.E., “A monolithic surface micromachined Z-axis gyroscope with digital output,” 2000 Symposium on VLSI Circuits. Digest of Technical Papers, 15-17 June 2000; Honolulu, HI, pp. 16-19.

[Luo 2002] H. Luo, X. Zhu, H. Lakdawala, L.R. Carley and G.K. Fedder, “A copper CMOS-MEMS z-axis gyroscope,” in The 15th IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2002), Las Vegas, Nevada, Jan. 21-25, 2002, pp.631-634.

[Seshia 2002] Seshia, A.A. ; Howe, R.T.; Montague, S, “An integrated microelectromechanical resonant output gyroscope,” Technical Digest Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2002), Las Vegas, NV, p.722-726.

[Sparks 1999] D. Sparks, D. Slaughter, R. Beni, L. Jordan, M. Chia, D. Rich, J. Johsnon, T. Vas, “Chip-scale packaging of a gyroscope using wafer bonding”, Sensors and Materials, vol.11 (1999), no.4, pp.197-207.

[Xie 2001] H. Xie, G. K. Fedder, A CMOS-MEMS Lateral-axis Gyroscope, in The 14th IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2001), Interlaken, Switzerland, January 21-25, 2001, pp.162-165.

[Xie 2002] H. Xie, and G.K. Fedder, "A DRIE CMOS-MEMS Gyroscope", IEEE Sensors 2002 Conference, June 12-14, 2002, Orlando, Florida.

EEL6935 Advanced MEMS 2005 H. Xie 19

Term Project

The objective of this project is to find MEMS solutions for some practical problems and/or develop new MEMS designs.

1.Form teams (Jan. 28)Up to three students per team

2. Project proposal (Feb. 21)- Problem statement (motivation)- Your proposed solution(s)- Tasks to be pursued - Project schedule

3. Proposal presentation (Feb. 21)8 minutes presentation + 2 minutes questions

4. Progress presentation (Mar. 18)8 minutes presentation + 2 minutes questions

5. Final presentation (Apr. 18&20)15 minutes presentation + 3 minutes questions

6. Final report (due Apr. 26)

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Term Project Teams

Piezoelectric mirrorYaweiShane Todd

EricSteven Singer

RF oscillatorn.a.Maojiao He

ShaneYawei Li

New mems devicen.a.Julio Correa

electrostatic actuatorN.A.Jessica Bronson

AnkurHongwei Qu

MicropumpSteveEric Stava

InertialN.A.Deyou Fang

?Bryan Blackburn

electrostatic/electrothermal actuationHongweiAnkur Jain

Biomems: drug deliveryN.AAdrian Cameron

NoteTopicTeam memberName

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Assume a differential parallel-plate capacitive accelerometer. The proof mass and resonant frequency of the accelerometer is 2µg and 5kHz, respectively. The plates are 200µm by 200µm. The gaps are 1µm. The modulation sinusoidal signal has an amplitude of 1V and frequency of 1MHz. The parasitic capacitance is 100fF.

(a)Calculate the Brownian noise of the accelerometer (only consider the squeeze-film damping of the parallel pates).

(b)Calculate the mechanical sensitivity (i.e., what’s the displacement per g).(c)Calculate the sensitivity (mV/g) at the sensing node if the input capacitance of the amplifier is 100fF.(d)If the dominant noise of the amplifier is flicker noise (given by the following equation), calculate the

optimal width of the input transistor. Assume the length of the transistor is 0.5µm and only the gate-source capacitance is considered. Assume Kf = 2x10-21V2m2.

(e)List the possible approaches for setting the DC bias of the sensing node.(f) Draw the circuit diagram for the case in which charge integration is used. What value of the feedback

capacitor should be chosen if a sensitivity of 50mV/g at the output node is desired.

EEL6935 Advanced MEMS (Spring 2005) Instructor: Dr. Huikai Xie

C0+∆C

C0-∆C Cp Rdc

+Vm

-Vm

A

2fn Kv

f WLf∆

=∆

Homework 4

Vout