Guitar String EE C245 – ME C218 Introduction to …ee245/fa12/lectures/Lec3...EE C245 – ME C218 Introduction to MEMS Design Fall 2012 Prof. Clark T.-C. Nguyen Dept. of Electrical

EE C245/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II

CTN 9/3/12

Copyright @ 2012 Regents of the University of California 1

EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 1

EE C245 – ME C218Introduction to MEMS Design

Fall 2012Prof. Clark T.-C. Nguyen

Dept. of Electrical Engineering & Computer SciencesUniversity of California at Berkeley

Berkeley, CA 94720

Lecture Module 2: Benefits of Scaling


Basic Concept: Scaling Guitar StringsGuitar String

Guitar

Vibrating “A”String (110 Hz)Vibrating “A”

String (110 Hz)

High Q

110 Hz Freq.

Vib.

Am

plitu

de

Low Q

r

ro m

kfπ21

=

Freq. Equation:

Freq.

Stiffness

Mass

fo=8.5MHzQvac =8,000

Qair ~50

μMechanical Resonator

Performance:Lr=40.8μm

mr ~ 10-13 kgWr=8μm, hr=2μmd=1000Å, VP=5VPress.=70mTorr

[Bannon 1996]


-60

-50

-40

-30

-20

-10

0

8.7 8.9 9.1 9.3Frequency [MHz]

Tran

smis

sion

[dB

]

Pin=-20dBm

In Out

VP

Sharper roll-off

Sharper roll-off

Loss PoleLoss Pole

Performance:fo=9MHz, BW=20kHz, PBW=0.2%

I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45

Performance:fo=9MHz, BW=20kHz, PBW=0.2%

I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45

Design:Lr=40μm

Wr=6.5μm hr=2μm

Lc=3.5μmLb=1.6μm VP=10.47VP=-5dBm

RQi=RQo=12kΩ

[S.-S. Li, Nguyen, FCS’05]

3CC 3λ/4 Bridged μMechanical Filter

[Li, et al., UFFCS’04]EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 4

ω

vovi

Micromechanical Filter Circuit

1/krmr cr 1/krmr cr 1/krmr cr-1/ks -1/ks

1/ks

-1/ks -1/ks

1/ks

1/kb 1/kb

-1/kb

Co Co

1:ηe ηe:11:ηc 1:ηcηc:1 ηc:1

1:ηb ηb:1

λ/4

λ/4

3λ/4Input

Outputvi

RQ

RQ

vo

VP

Bridging BeamCoupling Beam

Resonator


CTN 9/3/12



-100-98-96-94-92-90-88-86-84

1507.4 1507.6 1507.8 1508 1508.2

1.51-GHz, Q=11,555 NanocrystallineDiamond Disk μMechanical Resonator

• Impedance-mismatched stem for reduced anchor dissipation

•Operated in the 2nd radial-contour mode•Q ~11,555 (vacuum); Q ~10,100 (air)• Below: 20 μm diameter disk

PolysiliconElectrode R

Polysilicon Stem(Impedance Mismatched

to Diamond Disk)

GroundPlane

CVD DiamondμMechanical Disk

Resonator Frequency [MHz]

Mix

ed A

mpl

itude

[dB

]

Design/Performance:R=10μm, t=2.2μm, d=800Å, VP=7Vfo=1.51 GHz (2nd mode), Q=11,555

fo = 1.51 GHzQ = 11,555 (vac)Q = 10,100 (air)

[Wang, Butler, Nguyen MEMS’04]

Q = 10,100 (air)

§


vi+

vi-

vo+

vo-

VP

VP

λ

λ/2

λ/4

λ/2

λ/4

Port1Port1

Port2Port2

Port3Port3

Port4Port4

λ

λ/2

λ/2

Filter CouplerCom. Array Couplers

Diff. Array Couplers

[Li, Nguyen Trans’07]

163-MHz Differential Disk-Array Filter


Wireless Phone

90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna

Frequency [MHz]

Tran

smis

sion

[dB

]

Micromechanical Bandpass FilterMicromechanical Bandpass Filter

High Q and good linearity of micromechanical resonators

High Q and good linearity of micromechanical resonators

Filters for front-end frequency selection

Filters for front-end frequency selection

Linear MEMS in Wireless Comms


Wireless Phone

Miniaturization of RF Front Ends

26-MHz XstalOscillator

26-MHz XstalOscillator

DiplexerDiplexer

925-960MHz RF SAW Filter925-960MHz

RF SAW Filter

1805-1880MHz RF SAW Filter

1805-1880MHz RF SAW Filter

897.5±17.5MHz RF SAW Filter

897.5±17.5MHz RF SAW Filter

RF Power Amplifier

RF Power Amplifier

Dual-Band Zero-IF Transistor Chip

Dual-Band Zero-IF Transistor Chip

3420-3840MHz VCO

3420-3840MHz VCO

90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna

Problem: high-Q passives pose a bottleneck against miniaturizationProblem: high-Q passives pose a bottleneck against miniaturization


CTN 9/3/12



Duplexer

90o0o

A/D

A/D

RXRF ChannelSelect PLL

I

Q

LPF

LPF

RXRF LO

I

QAGC

AGC

LNA

Duplexer RF BPF

LNAFrom TX

LNA

LNA

RF BPF

RF BPF

RF BPF

WCDMAWCDMA

CDMACDMA--20002000

DCS 1800DCS 1800

PCS 1900PCS 1900LNA

RF BPF

Duplexer

LNA RF BPF

GSM 900GSM 900

CDMACDMA

From TX

From TX90o

0o

I

Q

Tank

÷ (N+1)/N XstalOsc

Antenna

• The number of off-chip high-Qpassives increases dramatically

•Need: on-chip high-Q passives

Multi-Band Wireless Handsets


All High-Q Passives on a Single Chip

WCDMARF Filters

(2110-2170 MHz)

CDMA-2000RF Filters

(1850-1990 MHz)

DCS 1800 RF Filter(1805-1880 MHz)

PCS 1900 RF Filter(1930-1990 MHz)

GSM 900 RF Filter(935-960 MHz)

CDMA RF Filters(869-894 MHz)

0.25 mm

0.5 mm

Low Freq. Reference Oscillator Ultra-High

Q Tank

Optional RF Oscillator

Ultra-High QTanks

Vibrating Resonator62-MHz, Q~161,000

Vibrating Resonator62-MHz, Q~161,000

Vibrating Resonator1.5-GHz, Q~12,000

Vibrating Resonator1.5-GHz, Q~12,000


Chip-Scale Atomic Clocks (CSAC)


NIST F1 Fountain Atomic Clock

VolVol: ~3.7 m: ~3.7 m33

Power: ~500 WPower: ~500 WAcc: Acc: 11××1010––1515

Stab: 3.3x10Stab: 3.3x10--1515/hr/hr

Physics PackagePhysics Package

After 1 sec Error: 10-15 secAfter 1 sec

Error: 10-15 sec

Loses 1 sec every 30 million years!



CTN 9/3/12



Benefits of Accurate Portable Timing

Secure Communications

Networked Sensors

Faster frequency hop ratesFaster frequency hop rates

Faster acquire of pseudorandom signals

Faster acquire of pseudorandom signals

Superior resilience against jamming or

interception

Superior resilience against jamming or

interception

More efficient spectrum utilization

More efficient spectrum utilization

Longer autonomy periodsLonger autonomy periods GPS

Faster GPS acquireFaster GPS acquire

Higher jamming margin

Higher jamming margin

Fewer satellites needed

Fewer satellites needed

Larger networks with longer autonomy

Larger networks with longer autonomy

Better TimingBetter Timing


NIST F1 Fountain Atomic Clock

VolVol: ~3.7 m: ~3.7 m33

Power: ~500 WPower: ~500 WAcc: Acc: 11××1010––1515

Stab: 3.3x10Stab: 3.3x10--1515/hr/hr

Physics PackagePhysics Package

After 1 sec Error: 10-15 secAfter 1 sec

Error: 10-15 sec




1.5 mm

4.2 mm

1.5 mm

Laser

Optics

Cell

Photodiode

1 mm

Total Volume: 9.5 mm3 Stability: 2.4 x 10-10 @ 1sCell Interior Vol: 0.6 mm3 Power Cons: 75 mW

Total Volume: 9.5 mm3 Stability: 2.4 x 10-10 @ 1sCell Interior Vol: 0.6 mm3 Power Cons: 75 mW

1st Chip-Scale Atomic Physics Package

GlassND

SiQuartz

ND

Lens

Alumina

VCSEL

NIST’s Chip-Scale Atomic

Physics Package

NIST’s Chip-Scale Atomic

Physics Package


Tiny Physics Package Performance

NIST’sChip-Scale

Atomic Physics Package

NIST’sChip-Scale

Atomic Physics Package

40 50 60 70 80 905.65

5.66

5.67

PD S

igna

l [V]

Frequency Detuning, Δ [kHz] from 9,192,631,770 Hz

7.1 kHz

Contrast: 0.91% 2.4e-10 Allandeviation @ 1 s2.4e-10 Allan

deviation @ 1 s

• Experimental Conditions:Cs D2 ExcitationExternal (large) Magnetic ShieldingExternal Electronics & LO Cell Temperature: ~80 ºCCell Heater Power: 69 mWLaser Current/Voltage: 2mA / 2VRF Laser Mod Power: 70μW

DimeDime

Open Loop Resonance:Drift to Be Removed in Phase 3

Drift to Be Removed in Phase 3

Sufficient to meet CSAC

program goals

Sufficient to meet CSAC

program goals

100 101 102 103 104 10510-12

10-11

10-10

10-9

Alla

n D

evia

tion,

σy

Integration Time, τ [s]

Stability Measurement:

Drift IssueDrift Issue

Rb (D1)Rb (D1) 1 day1 day1 hour1 hour

Cs (D2)Cs (D2)

Q =1.3x106Q =1.3x106

CSAC Goal


CTN 9/3/12



Atomic Clock Fundamentals

133Cs

m = 0f = 4

m = 0f = 3

m = 1

• Frequency determined by an atomic transition energy

Energy Band Diagram

Excite e- to the next orbital

Excite e- to the next orbital

Opposite e- spins

Opposite e- spins

ΔE = 0.000038 eV

ΔE = 1.46 eV

ν = ΔE/h= 352 THz852.11 nm

ν = ΔE/ħ= 9 192 631 770 Hz


Miniature Atomic Clock Design

ν = ΔE/ħ= 9 192 631 770 Hz

HyperfineSplitting Freq.

HyperfineSplitting Freq.

Sidebands

ModulatedLaser

PhotoDetector

133Cs vapor at 10–7 torr

Mod f

μwave osc

VCXO4.6 GHz

9.2GHz

4.6GHz

Atoms become transparent to light at 852 nm

Atoms become transparent to light at 852 nm

Carrier(852 nm)

λ

Close feedback loop to lock

Close feedback loop to lock

vo


Chip-Scale Atomic Clock

• Key Challenges:thermal isolation for low powercell design for maximum Qlow power μwave oscillator

Atomic Clock Concept Cs or Cs or RbRbGlassGlassDetectorDetector

VCSELVCSEL

SubstrateSubstrate

GHzGHzResonatorResonatorin Vacuumin Vacuum

MEMS andMEMS andPhotonic Photonic

TechnologiesTechnologies

VolVol: 1 cm: 1 cm33

Power: 30 Power: 30 mWmWStab: Stab: 11××1010––1111

Chip-ScaleAtomic Clock

Laser 133Cs vapor at 10–7 torr

Mod f

μwave oscVCXO

4.6 GHzvo PhotoDetector


Challenge: Miniature Atomic CellLarge Vapor Cell Tiny Vapor Cell

1,000XVolumeScaling

Wall collision dephasesatoms lose coherent state

Wall collision dephasesatoms lose coherent state

Inte

nsity

Mod f9.2 GHz

SurfaceVolume

More wall collisions stability gets worse

More wall collisions stability gets worse

lower Qlower Q

lowest Qlowest QAtomic Resonance


CTN 9/3/12



Challenge: Miniature Atomic CellLarge Vapor Cell Tiny Vapor Cell

1,000XVolumeScaling

Inte

nsity

Mod f9.2 GHz

Atomic Resonance

Soln: Add a buffer gas

Soln: Add a buffer gas

Lower the mean free path of the atomic vapor

Lower the mean free path of the atomic vapor

Return to higher Q

Return to higher Q

Buffer Gas


Chip-Scale Atomic Clock

• Key Challenges:thermal isolation for low powercell design for maximum Qlow power μwave oscillator

Atomic Clock Concept Cs or Cs or RbRbGlassGlassDetectorDetector

VCSELVCSEL

SubstrateSubstrate

GHzGHzResonatorResonatorin Vacuumin Vacuum

MEMS andMEMS andPhotonic Photonic

TechnologiesTechnologies

VolVol: 1 cm: 1 cm33

Power: 30 Power: 30 mWmWStab: Stab: 11××1010––1111

Chip-ScaleAtomic Clock

Laser 133Cs vapor at 10–7 torr

Mod f

μwave oscVCXO

4.6 GHzvo PhotoDetector


Rth= 38 K/WCth= 22 J/K

Rth= 38 K/WCth= 22 J/K Rth= 83,000 K/W

Cth= 6.3x10-6 J/KRth= 83,000 K/WCth= 6.3x10-6 J/K

P RthCth

T = P x Rth

Cth ~ volume

Rth ~ support lengthX-section area

Macro-Scale Micro-Scale

P (@ 80oC) = 2.6 mWP (@ 80oC) = 2.6 mW

Warm Up, τ = 0.1 sWarm Up, τ = 0.1 s

P (@ 80oC) = 1.5 WP (@ 80oC) = 1.5 W

Warm Up, τ = 16 min.Warm Up, τ = 16 min.

550x lower power550x lower power

7,300x faster warm up7,300x faster warm up

300x300x300 μm3

Atomic Cell @ 80oC

Long, Thin Polysilicon

Tethers

T Sensor(underneath)

Heater

LaserInsulation

Macro-Oven(containing heater

and T sensor)Atomic Cell @ 80oC

Thermally Isolating Feet

Laser25oC

3 cm

Micro-Scale Oven-Control Advantages


Physics Package Power Diss. < 10 mW

Heater/Sensor SuspensionCesium cell

Frame Spacer

VCSEL Suspension

VCSEL / Photodiode 20 pin LCC

7 mm

0

2

4

6

8

10

12

0 20 40 60 80 100 120 140Temperature [oC]

Pow

er [m

W] Measured

Model

Only ~5 mWheating power

needed to achieve 80oC

cell temperature

Only ~5 mWheating power

needed to achieve 80oC

cell temperature

• Achieved via MEMS-based thermal isolation

Symmetricom / Draper Physics

Package Assembly

Symmetricom / Draper Physics

Package Assembly

Documents

Guitar String EE C245 – ME C218 Introduction to …ee245/fa12/lectures/Lec3...EE C245 – ME C218 Introduction to MEMS Design Fall 2012 Prof. Clark T.-C. Nguyen Dept. of Electrical