integrated micromechanical circuits for rf front-ends · c. t.-c. nguyen, “integrated...
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C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Integrated Micromechanical Circuits for RF Front-Ends
Clark T.-C. Nguyen
Dept. of Electrical Engineering & Computer SciencesUniversity of California at Berkeley
Berkeley, California 94720E-mail: [email protected]
IEEE SSCS Dist. Lec.—Fort CollinsNov. 30, 2007
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Outline
• Introduction: Miniaturization of Transceiversneed for high-Q
• Micromechanical Resonatorsclamped-clamped beamsmicromechanical disks
• Micromechanical Resonator Oscillators• Micromechanical Circuits
micromechanical filtersimpedance matchingMSI mechanical circuits
• Conclusions
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wireless Phone
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
Motivation: Miniaturization of RF Front Ends
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
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wireless Phone
Rec
eive
dPow
er
FrequencyωRF
Motivation: Miniaturization of RF Front Ends
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
Need high Q to minimize loss
lower noise figure
Need high Q to minimize loss
lower noise figureHighly selective
frequency filteringHighly selective
frequency filtering
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wireless Phone
FrequencyωRF
Motivation: Miniaturization of RF Front Ends
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
Need high Q to minimize loss
lower noise figure
Need high Q to minimize loss
lower noise figureHighly selective
frequency filteringHighly selective
frequency filtering
DesiredSignal
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wireless Phone
FrequencyωRF
Motivation: Miniaturization of RF Front Ends
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
DesiredSignal
Need high Qor low loss
components to do this
Need high Qor low loss
components to do this
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wireless Phone
So Many Passive Components!
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
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Multi-Band Wireless Handsets
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 1900
LNA
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
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Thin-Film Bulk Acoustic Resonator (FBAR)
• Piezoelectric membrane sandwiched by metal electrodesextensional mode vibration: 1.8 to 7 GHz, Q ~500-1,500dimensions on the order of 200μm for 1.6 GHzlink individual FBAR’s together in ladders to make filters
Agilent FBAR
• Limitations:Q ~ 500-1,500, TCf ~ 18-35 ppm/oCdifficult to achieve several different freqs. on a single-chip
h
freq ~ thicknessfreq ~ thickness
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
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
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Vibrating RF MEMS Wish List
•• MicroMicro--scale waferscale wafer--level fabricationlevel fabricationwould like >1,000 parts per die to at least achieve large-scale integration (LSI) complexityneed wafer-level packaging
•• SingleSingle--chip integrated circuit or chip integrated circuit or system capabilitysystem capability
discrete parts not interestingmust allow many different frequencies on a single-chipneed on-chip connectivityintegration w/ transistors desiredneed real time reconfigurability
•• QQ’’s >10,000 at RF might have a s >10,000 at RF might have a revolutionary impactrevolutionary impact
Frequencies should be determined by lateral
dimensions (e.g., by layout)
Frequencies should be determined by lateral
dimensions (e.g., by layout)
Best if systems can be reconfigured w/o the need
for RF MEMS switches
Best if systems can be reconfigured w/o the need
for RF MEMS switches
900 MHz
1800 MHz
433 MHz200 MHz
70 MHz
1900 MHz
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Vibrating RF MEMS
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Basic Concept: Scaling Guitar StringsGuitar String
Guitar
Vibrating “A”String (110 Hz)Vibrating “A”
String (110 Hz)
High Q
110 Hz Freq.
Vib
. Am
plit
ud
e
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]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Anchor Losses
Q = 15,000 at 92MHz
Fixed-Fixed Beam Resonator
GapAnchor AnchorElectrode
Problem: direct anchoring to the
substrate anchor radiation into the
substrate lower Q
Problem: direct anchoring to the
substrate anchor radiation into the
substrate lower Q
Solution: support at motionless nodal points
isolate resonator from anchors less
energy loss higher Q
Solution: support at motionless nodal points
isolate resonator from anchors less
energy loss higher Q
Lr
Free-Free Beam
Supporting Beams
λ/4
Anchor
Anchor
Elastic WaveRadiation
Q = 300 at 70MHz
Free-Free Beam Resonator
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
• Constructed in SiC material w/ 30 nm Al metallization for magnetomotive pickup
Lr
Wr
h
Frequency [GHz]
Mag
neto
mot
ive
Res
p. [n
V]
Design/Performance:Lr =1.1 μm, Wr =120 nm, h= 75 nm
fo=1.029 GHz, Q =500 @ 4K, vacuum
Design/Performance:Lr =1.1 μm, Wr =120 nm, h= 75 nm
fo=1.029 GHz, Q =500 @ 4K, vacuum
[Roukes, Zorman 2002]
Nanomechanical Vibrating Resonator
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Scaling-Induced Performance Limitations
Mass Loading Noise
• Differences in rates of adsorption and desorption of contaminant molecules
mass fluctuationsfrequency fluctuations
Temperature Fluctuation Noise
• Absorption/emission of photons
temperature fluctuationsfrequency fluctuations
ContaminantMolecules
NanoresonatorMass ~10-17 kg
mk
2π1
of =
Photons
NanoresonatorVolume ~10-21 m3
• Problem: if dimensions too small phase noise significant!• Solution: operate under optimum pressure and temperature
[J. R. Vig, 1999]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Radial-Contour Mode Disk Resonator
VP
vi
Input Electrode
Output Electrode
io ωωο
ivoi
Q ~10,000Disk
Supporting Stem
Smaller mass higher freq. range and lower series Rx
Smaller mass higher freq. range and lower series Rx(e.g., mr = 10-13 kg)(e.g., mr = 10-13 kg)
Young’s Modulus
Density
Mass
Stiffness
RE
mkf
r
ro
121
⋅∝=ρπ
Frequency:
R
VP
C(t)
dtdCVi Po =
Note: If VP = 0V device off
Note: If VP = 0V device off
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
RF BPF
RF BPF
RF BPF
Multi-Band Wireless Handsets
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
WCDMAWCDMA
CDMACDMA--20002000
DCS 1800DCS 1800
PCS 1900PCS 1900
LNA
Duplexer
LNA RF BPF
GSM 900GSM 900
CDMACDMA
From TX
From TX90o
0o
I
Q
Tank
÷ (N+1)/N XstalOsc
Antenna
Capacitively transduced
micromechanical resonators switch
themselves
Capacitively transduced
micromechanical resonators switch
themselves
No need for switches!
No need for switches!
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
-100-98-96-94-92-90-88-86-84
1507.4 1507.6 1507.8 1508 1508.2
1.51-GHz, Q=11,555 Nanocrystalline Diamond 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)
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Self-Aligned Fabrication Process
• Strategy: make stem misalignment impossible• Below:
successive film depositionssimultaneous definition of disk shape and stem location
Silicon Substrate
SiliconNitridePolysiliconOxide Polydiamond
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Self-Aligned Fabrication Process
• Below:define electrode-to-resonator gap spacing via sacrificial oxide sidewall spaceretch stem anchor
Silicon Substrate
SacrificialOxide
SidewallSpacer
Photoresist
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Self-Aligned Fabrication Process
• Below:deposit thick polysiliconpattern to define stem and electrodes
Silicon Substrate
Polysilicon
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Self-Aligned Fabrication Process
• Result: micromechanical disk with perfectly centered stem and nano-scale electrode-to-resonator gaps
Silicon Substrate
Sturdy PolysiliconElectrode (stronger
than previous metal)
Sturdy PolysiliconElectrode (stronger
than previous metal)
Tiny Gaps (50 nm gaps have been achieved)
Tiny Gaps (50 nm gaps have been achieved)
Micromechanical Disk Structure
Micromechanical Disk Structure
Self-Aligned Stem Perfectly Placed at Disk Center
Self-Aligned Stem Perfectly Placed at Disk Center
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Output
Input Anchor
d = 80 nm• Right: zoom-in on the 80 nm gap achieved via the sacrificial sidewall spacer process
Tiny Lateral Transducer Gaps
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
•Freq.-Q product rising exponentially over the past years
1990 1995 2000 2005 2010
1015
109
1010
1011
1012
1013
1014
Year
Freq
uenc
y-Q
Prod
uct
silicon
diamond
silicon
silicon
silicon
silicon
silicon
fo = 1.51 GHzQ = 11,555
fo = 1.51 GHzQ = 11,555
silicon
μMechanical Resonator fo-Q Product
Intrinsic material Q limit nowhere
in sight?
Intrinsic material Q limit nowhere
in sight?
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Micromechanical Resonator Oscillators
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
• Main Function: provide a stable output frequency• Difficulty: superposed noise degrades frequency stability
ωωο
ivoi
A
Frequency-SelectiveTank
SustainingAmplifier
ov
Ideal Sinusoid: ( ) ⎟⎠⎞⎜
⎝⎛= tofVotov π2sin
Real Sinusoid: ( ) ( ) ( )⎟⎠⎞⎜
⎝⎛⎟
⎠⎞⎜
⎝⎛ ++= ttoftVotov θπε 2sin
ωωο
ωωο=2π/TO
TO
Zero-Crossing Point
Tighter SpectrumTighter Spectrum
Oscillator: Need for High Q
Higher QHigher Q
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Output
Input
Input
Output
Support Beams
Wine Glass Disk Resonator
R = 32 μm
Anchor
Anchor
Resonator DataR = 32 μm, h = 3 μmd = 80 nm, Vp = 3 V
Resonator DataR = 32 μm, h = 3 μmd = 80 nm, Vp = 3 V
-100
-80
-60
-40
61.325 61.375 61.425
fo = 61.37 MHzQ = 145,780
Frequency [MHz]
Unm
atch
ed T
rans
mis
sion
[dB
]
Polysilicon Wine-Glass Disk Resonator
[Y.-W. Lin, Nguyen, JSSC Dec. 04]
Compound Mode (2,1)
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Phase Noise in Oscillators
• Single Sideband Phase Noise Density to Carrier Power Ratio in Oscillator, Lfm
Offset Frequency [Hz]
Phas
e N
oise
[dB
c/H
z]
100 1k 10k 100k10
-120
-100
-80
-60
-140
⇒ Carrier Frequency⇒ Offset Frequency⇒ Signal Power
of
mf
oP
•• High High QQreduces close-to-carrier phase noise
•• High High PPooreduces far-from-carrier phase noise
2
m
o
om fQ
fPkTfL ⎟
⎟⎠
⎞⎜⎜⎝
⎛
⋅⋅∝
f
Po
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wine Glass Disk Oscillator
Wine-Glass Disk Resonator (Q=48,000)
VDD = 1.65 V
VSS = -1.65V
M3M4
M1 M2
MRf
Vbias2
Vbias1
M11 M12 M13 M14
Vcm
M17M18
M16M15Output
Input
M5
Shunt-Shunt Feedback Tranresistance Amplifier
Common Mode Feedback Bias Circuit
VP
vi
io
Bond Wire ConnectionBond Wire Connection
MOS ResistorMOS
Resistor
VP=12V Rx=1.5kΩVP=12V Rx=1.5kΩ
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
OutputOutput Custom IC fabricated via TSMC 0.35μm process
Custom IC fabricated via TSMC 0.35μm process
InputInput
200 mV
20 ns
Frequency [MHz]
Pow
er [d
Bm
]
-100
-80
-60
-40
-20
0
61.05 61.1 61.15 61.2 61.25 61.3 61.35
Time & Freq. Domain Performance
Oscilloscope Waveform
Oscilloscope Waveform
Spectrum Analyzer Output
Spectrum Analyzer Output
[Y.-W. Lin, Nguyen, ISSCC’04]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
-160-140-120-100
-80-60-40-20
0
1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06Offset Frequency [Hz]
Phas
e N
oise
[dB
c/H
z] 60 MHz, Wine-Glass Disk Oscillator
Down to 13 MHzFor Comparison
[Y.-W. Lin, Nguyen, JSSC’04]
1/f 3
Phase Noise Measurement
-130 dBc/Hz @ 1 kHz-130 dBc/Hz @ 1 kHz
-147 dBc/Hz-147 dBc/Hz
Nearly satisfies Global System for Mobile Communications (GSM)
phase noise specifications!
Nearly satisfies Global System for Mobile Communications (GSM)
phase noise specifications!Requires only 300 μW
and 150 x 150 μm2!Requires only 300 μW
and 150 x 150 μm2!
f
Po
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Integrated Micromechanical Circuits
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Micromechanical Filter Design Basics
RQ
vo
vi
RQ
VP
ω
xovi
ωo ω
xovi
ωo ω
vovi
ωo ω
vovi
ωo
Disk Resonator
Coupling Beam
Bridging Beam
Termination Resistor
Loss Pole
Loss Pole
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
-60
-50
-40
-30
-20
-10
0
8.7 8.9 9.1 9.3Frequency [MHz]
Tra
nsm
issi
on
[d
B]
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]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
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
ω
vovi
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
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
ω
vovi
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
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
ω
vovi
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
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
All circuit element values determined
by CAD layout
All circuit element values determined
by CAD layout
Amenable to automated circuit
generation
Amenable to automated circuit
generation
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
-60
-50
-40
-30
-20
-10
0
8.7 8.9 9.1 9.3
High-Order Micromechanical Filter
[Wang, MEMS’97]
High-Order Micromechanical Filter
[Wang, MEMS’97]HF Micromech. Filter[Bannon, IEDM’96]
HF Micromech. Filter[Bannon, IEDM’96]
fo = 340kHzIL < 0.6dBRQ = 364kΩ
fo = 340kHzIL < 0.6dBRQ = 364kΩ
Frequency [MHz]
Tra
nsm
issi
on
[d
B]
Sharper roll-offs
Sharper roll-offs
Bridged μMech. Filter[S.-S. Li, UFFCS’2004]Bridged μMech. Filter[S.-S. Li, UFFCS’2004]
fo = 9.3MHzIL < 2.8dBRQ = 12kΩ
fo = 9.3MHzIL < 2.8dBRQ = 12kΩ
fo = 7.8 MHzIL < 2dBRQ = 14.7kΩ
fo = 7.8 MHzIL < 2dBRQ = 14.7kΩ
Loss poleLoss pole
• MEMS Filters excellent insertion loss• Problem: high impedance & poor power handling
Demo’ed Micromechanical Filters
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Impedance Matching(Device Approach)
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Solid Dielectric Capacitive Transducer
Antenna
r h
Gap = d
VP
Disk Electrode Electrode
Air Gap w/ ε = εo
Solid Dielectric w/ Solid Dielectric w/ εε = = εεrrεεoo in the Gapin the Gap
DiskΔGap κ timesPermittivity ε εr times
ΔGap κ timesPermittivity ε εr times
Rx εr2/κ times
( ) 222
4
221
hVd
Qk
rR
Po
rx εωπ
⋅=
377Ω
kr = 7,350,000 N/m
5kΩ
Mismatch!
ResonanceResonance
Opportunity: increase permittivity εsquare law reduction in Rx
Opportunity: increase permittivity εsquare law reduction in Rx
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Output
InputAnchor
Tiny Lateral Solid-Dielectric Gaps
d = 80 nm
20nm 20nm Nitride GapNitride Gap
ElectrodeElectrode
Disk Disk ResonatorResonator
No small gap etch diffusion bottleneck
release step much faster than air gap case
No small gap etch diffusion bottleneck
release step much faster than air gap case
[Y.-W. Lin, C. Nguyen FCS’05]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Air- vs. Solid-Gap Comparison
-90
-80
-70
-60
-50
-40
-30
61.8 61.825 61.85 61.875 61.9
-130-120-110-100-90-80-70-60-50-40-30
61.75 61.85 61.95 62.05
60-MHz Wine-Glass Disk DataIn Vacuum, R = 32 µm, h = 3 µm
do = 80 nm (air gap)VP = 8 V, Pin = -10 dBm
fo = 61.927 MHz
Frequency [MHz]
Tran
smis
sion
[dB
] Q = 54,631
60-MHz Wine-Glass Disk DataIn Vacuum, = 32 µm, h = 3 µm
do = 20 nm (nitride gap) VP = 8 V, Pin = -30 dBm
fo = 61.855 MHz
Frequency [MHz]Tr
ansm
issi
on [d
B] Q = 36,814
Rx = 3.2 kΩRx = 42.67 kΩ
Rx 13X smallerRx 13X smaller
60-MHz WG Disk w/ Air Gap 60-MHz WG Disk w/ Solid Gap
Q is still very high even with solid gap
Q is still very high even with solid gap
Resonance frequency remains
virtually the same!
Resonance frequency remains
virtually the same!
Air GapAir Gap
Solid GapSolid Gap
[Y.-W. Lin, C. Nguyen FCS’05]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Benefit: Greatly Reduced DC-Bias
To achieve 50To achieve 50ΩΩ impedance, the DCimpedance, the DC--Bias voltage can be Bias voltage can be reduced from 147V to 0.91V using solid gap technologyreduced from 147V to 0.91V using solid gap technology
102030405060708090
100
0 20 40 60 80 100 120 140DC-Bias Voltage (V)
Mot
iona
l Res
ista
nce
(Ω) 80nm air
(ε = 1)
20nm nitride(ε = 7.8)
20nm HfO2(ε = 25)
20nm TiO2(ε = 80)
20nm BaSrTiO3(ε = 300)
147V11V 35V
3.5V0.91V
fo = 60 MHzQ = 40,000
fo = 60 MHzQ = 40,000
R = 32 μmh = 3 μm
R = 32 μmh = 3 μm
Assume Rx = 50Ωis required
Assume Rx = 50Ωis required
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Freq
uenc
y [M
Hz]
Temperature [oC]
20 μm
Piezoelectric μMechanical Resonators
• Contour-mode, ring-shaped AlN Resonators• Driven laterally via the d31 coefficient
TCF ~ -24.7 ppm/ºCTCF ~ -24.7 ppm/ºC
• Freqs. up to 473 MHz (so far) determined by lateral dimensions!
• Q’s sufficient for pre-select filters
Tran
smis
sion
[dB
] -50
-60
-70
-80
-90474.25 484.25464.25
Frequency [MHz]
fo~473 MHz Q ~2,900 in air
Rx~80 Ω
fo~473 MHz Q ~2,900 in air
Rx~80 Ω
[Piazza, Pisano MEMS’05]
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Impedance Matching(Mechanical Circuit Approach)
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
• Impedance matching needednot a new problem …
( ) 22
4
221
hVd
Qk
rR
Po
rx ⋅=
ωπ
μMechanical Disk Resonator
Antenna
377Ω
ResonanceResonance
kr = 7,350,000 N/m
5kΩ
Mismatch!
VDD
VSS
Off-ChipCapacitor
(2 pF)
MinimumSize
Inverter
2fFProgressively Larger Inverters
r h
Gap = d
VP
Issue: Impedance Matching
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Impedance Reduction Via Arraying
RL
vo
io
Anchor
VPvi
Support BeamCoupling Beam
MotionalResistance
PowerHandling
Output Current
Freq.
λ/2
ElectrodePhasing Design
Peak Select
ElectrodePhasing Design
Peak Select
λ/2 DesignPeak Split
λ/2 DesignPeak Split
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Support Beams Wine-GlassDisk
Anchor
InputElectrode
Coupling Beam
OutputElectrode
R = 32 μm
9-Wine-Glass Disk Composite Array
-110
-100
-90
-80
-70
-60
-50
-40
-30
61.8 61.85 61.9Frequency [MHz]
Tran
smis
sion
[dB
]
9-ResonatorQ = 118,900Rx = 2.56 kΩ
9-ResonatorQQ = 118,900= 118,900Rx = 2.56 kΩ
1-ResonatorQ = 161,000
Rx = 11.73 kΩ
1-ResonatorQQ = 161,000= 161,000
Rx = 11.73 kΩWine-glass disks
retain Q’s >100,000 even in large arrays!
Wine-glass disks retain Q’s >100,000
even in large arrays!
DataR = 32 μmh = 3 μm
d = 80 nmVP = 7 V
DataR = 32 μmh = 3 μm
d = 80 nmVP = 7 V
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wine Glass Disk Array Oscillator
VDD = 1.65 V
VSS = -1.65V
M3M4
M1 M2
MRf
Vbias2
Vbias1
M11 M12 M13 M14
Vcm
M17M18
M16M15Output
Input
M5
Shunt-Shunt Feedback Tranresistance Amplifier
Common Mode Feedback Bias Circuit
VP
vi
Bond Wire
Bond Wire
MOS ResistorMOS
Resistor
io
Wine-Glass Disk Array-Composite Resonator
Wine-Glass Disk Array-Composite Resonator
VP=7V Rx=2.5kΩ
Q = 118,900
VP=7V Rx=2.5kΩ
Q = 118,900
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
OutputOutputCustom IC fabricated via TSMC 0.35μm process
Custom IC fabricated via TSMC 0.35μm process
InputInput
GSM-Compliant Oscillator
[Y.-W. Lin, Nguyen, IEDM’05]
-160
-140
-120
-100
-80
-60
-40
-20
1.E+01 1.E+02 1.E+03 1.E+04 1.E+05
Offset Frequency [Hz]
Phas
e N
oise
[dB
c/H
z]
9-Wine-Glass Disk ArrayQ = 118,900 , Rx = 2.56 kΩ9-Wine-Glass Disk ArrayQQ = 118,900 = 118,900 , Rx = 2.56 kΩ
9-WG Disk Array @ 62 MHz9-WG Disk Array @ 62 MHz
Single WG Disk @ 62 MHzSingle WG Disk @ 62 MHz
Down to 13 MHz
Down to 13 MHz
GSM specGSM spec
Satisfies Global System for Mobile Communications (GSM)
phase noise specifications!
Satisfies Global System for Mobile Communications (GSM)
phase noise specifications!
All made possible by mechanical circuit design!
All made possible by mechanical circuit design!
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
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
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
-75-70-65-60-55-50-45-40-35-30-25-20-15-10-50
162.6 162.8 163.0 163.2 163.4 163.6
TerminatedUn-terminated
Performancer=17μmh=3μmdo=80nmVP=14VP=-15dBmfo=163.126MHzQres=10,500Rx=977ΩBW=98.477kHzPBW=0.06% I.L.=2.43dB20dB S.F.=2.85RQ1=RQ2=1.6kΩRQ3=RQ4=1.4kΩ
Frequency [MHz]
Tra
nsm
issi
on
[d
B]
High Q & Low RXHigh Q & Low RX
RQ ~ 1.5kΩRQ ~ 1.5kΩ
RQ ~ 50ΩRQ ~ 50Ω
Measured Filter Freq. Characteristics
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
-120
-110
-100
-90
-80
-70
-60
-50
-40
0 50 100 150 200 250 300
Filter Measurement Over 300MHz Span
No Spurious ModesNo Spurious ModesFrequency [MHz]
Tra
nsm
issi
on
[d
B]
Performancer=17μmh=3μmdo=80nmVP=8VP=-15dBmfo=163.126MHzBW=98.477kHzPBW=0.06%
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Wireless Phone
So Many Passive Components!
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 miniaturizationNo longer a problem!No longer a problem!
Use as many high-Qpassives as desired!Use as many high-Qpassives as desired!
Seemingly limitless possibilities …
Seemingly limitless Seemingly limitless possibilities possibilities ……
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
RF Channel Selection
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Motivation: Need for High Q
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Motivation: Need for High Q
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
Wireless Phone
Non-Coherent FSK Detector?(Simple, Low Frequency, Low Power)
Front-End RF Channel Selection
Front-End RF Channel Selection
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
Substantial Savings in Cost and Battery PowerSubstantial Savings in
Cost and Battery Power
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
Wireless Phone
Direct-Sampling A/D Converter Software-Defined Radio
Maximum Flexibility one circuit satisfies all
comm. standards
Maximum Flexibility one circuit satisfies all
comm. standardsFront-End RF
Channel SelectionFront-End RF
Channel Selection
Rec
eive
dPow
er
FrequencyωRF
DesiredSignal
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
RF Channel-Select Filter Bank
Bank of UHF μmechanical
filters
Bank of UHF μmechanical
filters
Switch filters on/off via
application and removal of dc-bias VP, controlled by
a decoder
Switch filters on/off via
application and removal of dc-bias VP, controlled by
a decoderTr
ansm
issi
on
Freq.
Tran
smis
sion
Freq.
Tran
smis
sion
Freq.
1 2 n3 4 5 6 7RF Channels
Remove all interferers!
Remove all interferers!
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Conclusions
•• Vibrating RF MEMS have achievedVibrating RF MEMS have achievedQ’s >10,000 at GHz frequencies in sizes less than 20 μm in diameter and w/o the need for vacuum encapsulationTCf’s < -0.24 ppm/oC (better than quartz)aging at least on par with quartzcircuit-amenable characteristics VLSI potential
•• Time to turn our focus towards mechanical circuit design and Time to turn our focus towards mechanical circuit design and mechanical integrationmechanical integration
maximize, rather than minimize, use of high-Q componentse.g., RF channelizer paradigm-shift in wireless designeven deeper frequency domain computation
•• NeedNeed::automated design tools for LSI and highersingle-chip integrability with transistor circuitsmethods for frequency positioningcontinued scaling to nano-dimensions >10 GHz …
•• Beginnings of a revolution reminiscent of the IC revolution?Beginnings of a revolution reminiscent of the IC revolution?
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
• UC Berkeley:Clark Nguyen, Al Pisanocapacitive & AlN resonators
• Hughes Research:Randy Kubenaquartz resonators
• Cal Tech: Michael Roukesnanomechanical resonators
• Georgia Tech:Farrokh AyaziSOI resonators
• Stanford:Tom Kenny, Roger Howeepi/SOI, SiGe resonators
fo = 1.03 GHzQ = 500
fo = 1.03 GHzQ = 500
Growing Vibrating RF MEMS Research
fo = 473 MHzQ = 2,900Rx ~ 80Ω
fo = 473 MHzQ = 2,900Rx ~ 80Ω
C. T.-C. Nguyen, “Integrated Micromechanical Circuits for RF Front-Ends,” SSCS Dist. Lec.—Fort Collins., 11/30/07
Acknowledgments
• Former graduate students, especiallyProf. Jing Wang, now at the Univ. of South FloridaDr. Sheng-Shian Li, now at RF MicrodevicesDr. Yu-Wei Lin, now at Broadcom
• Much of the work shown was funded by grants from DARPA and by an NSF ERC in Wireless Integrated Microsystems