MEMS Technologies and Devices for Single-Chip RF Front-Endsctnguyen/...C. T.-C. Nguyen, “MEMS Technologies and Devices for Single-Chip RF Front-Ends,” CICMT’06, 4/25/06 Outline

C. T.-C. Nguyen, “MEMS Technologies and Devices for Single-Chip RF Front-Ends,” CICMT’06, 4/25/06

MEMS Technologies and Devices for Single-Chip RF

Front-Ends

Clark T.-C. Nguyen

Dept. of Electrical Engineering & Computer ScienceUniversity of Michigan

Ann Arbor, Michigan 48105-2122

CICMT’06April 25, 2006


Outline

• Motivation: Miniaturization of Transceiversneed for high-Qmerged transistor/MEMS process

• High-Q Vibrating Micromechanical Resonatorsclamped-clamped beamsmicromechanical disksmicromechanical circuits

• Low-loss Micromechanical Switches• Tunable C’s and L’s• Conclusions


Wireless Phone

Motivation: Miniaturization of RF Front-Ends

26-MHz XstalOscillator


DiplexerDiplexer

925-960MHz RF SAW Filter925-960MHz

RF SAW Filter

1805-1880MHz RF SAW Filter


897.5±17.5MHz RF SAW Filter


RF Power Amplifier

RF Power Amplifier

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


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, “MEMS Technologies and Devices for Single-Chip RF Front-Ends,” CICMT’06, 4/25/06• Fabrication steps compatible with planar IC processing

Surface Micromachining


• Completely monolithic, low phase noise, high-Q oscillator (effectively, an integrated crystal oscillator)

• To allow the use of >600oC processing temperatures, tungsten (instead of aluminum) is used for metallization

OscilloscopeOutput

Waveform

Single-Chip MEMS/Transistor Integration

[Nguyen, Howe 1993][Nguyen, Howe JSSC’99]


MEMSMEMSTechnologyTechnology

Single-Chip Integration



DiplexerDiplexer

925-960MHz RF SAW Filter925-960MHz

RF SAW Filter





RF Power Amplifier

RF Power Amplifier



3420-3840MHz VCO

3420-3840MHz VCO

Single-ChipTransceiver

Wrist-watch-sized multi-band wireless device might be possible!

Wrist-watch-sized multi-band wireless device might be possible!


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


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


Vibrating RF MEMS


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 et al JSSC’00]


-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)


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


RF BPF

RF BPF

RF BPF


Duplexer

90o0o

A/D

A/D


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!


-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]


Integrated Micromechanical Circuits


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


-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]


Design:Disk Radius, R =17μm

Thickness, h =2μmNitride Gap, d =3.5μmArray Coupling Beam Length, La =26.9μm

Filter Coupling Beam Length, Lc =40.4μm

VP=4V RQi=RQo=13kΩ

Disk Array Composite μMechanical Filter

-25

-20

-15

-10

-5

0

155.2 155.4 155.6 155.8 156.0 156.2 156.4

Tran

smis

sion

[dB

]

Frequency [MHz]

[S.-S. Li, Nguyen, 2006]

Filter Extensional-Mode 3λ/4 Coupling Beam

Filter Extensional-Mode 3λ/4 Coupling Beam

λ/2 Array Couplerλ/2 Array Coupler

Performance:fo=155.9MHzBW=201kHzPBW=0.13%

I.L.=2dB

Performance:fo=155.9MHzBW=201kHzPBW=0.13%

I.L.=2dB

Disk array “composite”end resonator reduces

impedance & suppresses spurious modes

Disk array “composite”end resonator reduces

impedance & suppresses spurious modes


Low Loss Switch Needs

Duplexer

90o0o

A/D

A/D


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

For lowest on-chip loss, replace with RF MEMS switch

For lowest on-chip loss, replace with RF MEMS switch

Low loss switch

Low loss switch


Micromechanical Switch

[C. Goldsmith, 1995]

• Operate the micromechanical beam in an up/down binary fashion

• Performance: I.L.~0.1dB, IIP3 ~ 66dBm (extremely linear)• Issues: switching voltage ~ 50V, switching time: 1-5μs

Electrode

OutputInput

Dielectric


RF MEMS Switch (Radant)

• Metal cantilever DC switch3-terminal devicePt contact interfacehigh R silicon substrateelectrostatic actuation

Vactuate ~ 90V• Package: wafer-to-wafer

glass frit bonded caplow costenv. protection

100 μm

Drain

Gate

Beam

Source

Contact Detail

Packaged Device

• Reliability (gov’t tested):>1 T mechanical cycles>700 B cycles 100mW RF cold switch

• Reliability (Radant tested):>2.5 B cycles 2W RF cold switched>100 B cycles 0.5W RF cold switched

[Radant]


Medium Q Inductor & Capacitor Needs

Duplexer

90o0o

A/D

A/D


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

Tunable MEMS C’s and

μmachined L’s have higher Q

Tunable MEMS C’s and

μmachined L’s have higher Q

GSM VCO attainable by on-chip L and switched C’s

GSM VCO attainable by on-chip L and switched C’s


• Micromachined, movable, aluminum plate-to-plate capacitors• Tuning range exceeding that of on-chip diode capacitors and

on par with off-chip varactor diode capacitors

• Challenges: microphonics, tuning range truncated by pull-in

Voltage-Tunable High-Q Capacitor


Suspended, Stacked Spiral Inductor

• Strategies for maximizing Q:15μm-thick, electroplated Cu windings reduces series Rsuspended above the substrate reduces substrate loss


• Molybdenum-chromium metal solenoids perpendicular to the plane of the substrate

reduced substrate loss high Q• Assembled out-of-plane via curling

stresses, then locked into place• Record Q’s: ~70 on glass, ~40 on

20Ω-cm silicon (85 w/ Cu underside)

LockingMechanism

SolenoidInductor

Stress CurledMetal

Design/Performance:D=600μm, t=1μm

On Glass Substrate:L = 8nH, Q = 70 @ 1GHz

On 20Ω-cm Silicon:L = 6 nH, Q = 40 @ 1GHz(Q ~ 85 w/ Cu underside)

Design/Performance:D=600μm, t=1μm

On Glass Substrate:L = 8nH, Q = 70 @ 1GHz

On 20Ω-cm Silicon:L = 6 nH, Q = 40 @ 1GHz(Q ~ 85 w/ Cu underside)

D

[Chua, Hilton Head’02][PARC]

Out-of-Plane Micromachined Inductor


Reference Oscillator Needs

Duplexer

90o0o

A/D

A/D


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

Replace with vibrating

μmechanicalresonator

Replace with vibrating

μmechanicalresonator

Today, use quartz crystal

to attain Q>10,000

Today, use quartz crystal

to attain Q>10,000


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!



Duplexer

90o0o

A/D

A/D


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


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

Removes all interferers!

Removes all interferers!


Conclusions

• Integrated micromechanical technologies possess high-Q and low loss characteristics capable of greatly enhancing the performance of wireless communications

•• Probable evolution of products based on vibrating RF MEMS:Probable evolution of products based on vibrating RF MEMS:timing devices using micromechanical resonatorscommunication-grade frequency synthesizerssingle-chip of all needed high-Q passivessingle-chip radio (cognitive radio)mechanical radio front-ends …

•• In ResearchIn Research: Time to turn our focus towards mechanical : Time to turn our focus towards mechanical circuit design and mechanical integrationcircuit design and mechanical integration

maximize, rather than minimize, use of high-Q componentse.g., RF channelizer paradigm-shift in wireless designeven deeper frequency computation using VLSI micromechanics

•• Beginnings of a revolution reminiscent of the IC revolution?Beginnings of a revolution reminiscent of the IC revolution?


Acknowledgment

Much of the work presented (of mine and others) was supported by funding from

DARPA.

Documents

MEMS Technologies and Devices for Single-Chip RF Front-Endsctnguyen/...C. T.-C. Nguyen, “MEMS Technologies and Devices for Single-Chip RF Front-Ends,” CICMT’06, 4/25/06 Outline