ee c247b – me c218 introduction to mems design spring 2014ee247b/sp14/lectures/lec... · 2014. 1....
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EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 1
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 1
EE C247B – ME C218Introduction to MEMS Design
Spring 2014Prof. Clark T.-C. Nguyen
Dept. of Electrical Engineering & Computer SciencesUniversity of California at Berkeley
Berkeley, CA 94720
Lecture Module 2: Benefits of Scaling
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 2
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]
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 2
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 3
-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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 3
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 5
-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)
§
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 6
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 4
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 7
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 8
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 5
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 9
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 10
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 6
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 11
Chip-Scale Atomic Clocks (CSAC)
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 12
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!
Loses 1 sec every 30 million years!
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 7
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 13
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 14
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!
Loses 1 sec every 30 million years!
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 8
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 15
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 16
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 9
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 17
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 18
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 10
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 19
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 20
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 11
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 21
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 22
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
EE C247b/ME C218: Introduction to MEMSLecture 3m: Benefits of Scaling II
CTN 1/30/14
Copyright @ 2014 Regents of the University of California 12
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 23
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
EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 24
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