From MEMS to NEMS: Smaller Is Still Better

DARPA

From MEMS to NEMS: Smaller Is Still Better Clark T.-C. Nguyen Dept. of Electrical Engineering & Computer Science University of Michigan Ann Arbor, Michigan 48105-2122 (Last Month: Program Manager, DARPA/MTO) MARC’06 Meeting Jan. 25-26, 2006 C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

DARPA

Outline

• Introduction:

ª MEMS technology ª integration with transistors: an early driver for MEMS • Benefits of Scaling ª size reduction ª speed, energy conservation, complexity, economy • DARPA/MTO Program Examples ª Nano Mechanical Array Signal Processors (NMASP) ª Chip-Scale Atomic Clock (CSAC) ª Micro Gas Analyzers (MGA) • Conclusions (What’s Next?)

C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

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MEMS: Micro Electro Mechanical Systems

• A device constructed using micromachining (MEMS) tech. • A micro-scale or smaller device/system that operates mainly via a mechanical or electromechanical means • At least some of the signals flowing through a MEMS device are best described in terms of mechanical variables, e.g., displacement, velocity, acceleration, temperature, flow Input: voltage, current acceleration, velocity light, heat … Transducer Transducerto to Convert Control Convert Control to toaaMechanical Mechanical Variable Variable(e.g., (e.g., displacement, displacement, velocity, velocity,stress, stress, heat, heat,…) …)

MEMS

Output: voltage, current acceleration, velocity light, heat, … [Wu, UCLA]

Control: voltage, current acceleration velocity light, heat, …

Angle set by mechanical means to control the path of light C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

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Other Common Attributes of MEMS

• Feature sizes measured in microns or less 80 mm

Gimballed, Spinning Macro-Gyroscope

[Najafi, Michigan]

Micromechanical Vibrating Ring Gyroscope

MEMS Technology (for 80X size Reduction)

1 mm Signal Conditioning Circuits

• Merges computation with sensing and actuation to change

the way we perceive and control the physical world • Planar lithographic technology often used for fabrication ª can use fab equipment identical to those needed for IC’s ª however, some fabrication steps transcend those of conventional IC processing C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

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Bulk Micromachining and Bonding Micromechanical Vibrating Ring Gyroscope

• Use the wafer itself as the

structural material • Adv: very large aspect ratios, thick structures • Example: deep etching and wafer bonding

1 mm [Najafi, Michigan]

Movable Silicon Substrate Structure Silicon Substrate

Electrode

Glass Substrate Metal Interconnect

[Pisano, UC Berkeley]

Anchor


Microrotor (for a microengine)

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Surface Micromachining

• Fabrication steps compatible with planar IC processing


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Single-Chip Ckt/MEMS Integration

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

Oscilloscope Output Waveform [Nguyen, Howe [Nguyen, Howe1993] 1993]

• To allow the use of >600oC processing temperatures,

tungsten (instead of aluminum) is used for metallization


DARPA

Technology Trend and Roadmap for MEMS

Number of Transistors

increasing ability to compute

109

Pentium 4

108 107

CPU’s

106

ADXL-50

105 104 103 102 101

Distributed Structural Control

Terabit/cm2 Data Storage

Digital Micromirror Device (DMD)

Phased-Array Displays Inertial Navigation OMM 32x32 Antenna Integrated Fluidic On a Chip Systems i-STAT 1 Adaptive Weapons, Caliper Optics Safing, Arming, Future MEMS and Fusing Integration Levels Optical Switches & Aligners ADXL-278 Enabled Applications ADXRS ADXL-78

100 0 10 Majority of

Early MEMS Devices (mostly sensors)

101

102

103

104

105

106

107

Number of Mechanical Components increasing ability to sense and act


108

109

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Benefits of Size Reduction: IC’s

• Numerous benefits attained by scaling of transistors: Lower Power

Higher Current Drive Lower Capacitance Higher Integration Density Lower Supply Voltage

Faster Speed

Higher Circuit Complexity & Economy of Scale

• But … some drawbacks: ª poorer reliability (e.g., hot e- effects) ª lower dynamic range (analog ckts suffer)


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Example: Micromechanical Accelerometer

• The MEMS Advantage:

400 μm

Tinymass massmeans means ª >30X size reduction forTiny small output Ö need small output Ö need accelerometer mechanical element integrated integratedtransistor transistor ª allows integration with IC’stotocompensate circuits circuits compensate

Basic Operation Principle xo

x ∝ Fi = ma

x

Displacement Spring

a

Inertial Force Proof Mass Acceleration Analog Devices ADXL 78


DARPA

Technology Trend and Roadmap for MEMS

Number of Transistors

increasing ability to compute

109

Pentium 4

108 107

Distributed Structural 2 8x8 Optical Control OMM Terabit/cm Cross-Connect Switch Data Storage

CPU’s ADXL-50

Adv.: switching, Phased-Array Displays Adv.:faster faster switching,low low loss, larger networks Antenna OMM loss, 32x32 larger networks

Analog 10 Devices ADXRS 6 Integrated Gyroscope Inertial

Navigation Adv.: Adv.:small smallsize sizeOn a Chipi-STAT 1 Adaptive Weapons, Caliper 104 Optics Safing, Arming, and Fusing 103 Optical Switches & Aligners ADXL-278 2 10 ADXRS Caliper Microfluidic Chip ADXL-78

105

101

Early MEMS Devices (mostly sensors)

Integrated Fluidic Systems Future MEMS Integration Levels Enabled Applications

TI Digital Micromirror Device

100 0 10 Majority of

Digital Micromirror Device (DMD)

101

102

103

104

Adv.: Adv.:low lowloss, loss,fast fast switching, high fill factor 9 7 fill 105 switching, 106 10high 108factor 10

Number of Mechanical Components increasing ability to sense and act

Adv.: Adv.:small smallsize, size,small small sample, analysis speed C. T.-C. Nguyen, “From MEMSfast to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05 fast analysis speed sample,

DARPA

Benefits of Size Reduction: MEMS

• Benefits of size reduction clear for IC’s in elect. domain

ª size reduction Ö speed, low power, complexity, economy • MEMS: enables a similar concept, but …

MEMS extends the benefits of size reduction beyond the electrical domain Performance enhancements for application domains beyond those satisfied by electronics in the same general categories Speed

Frequency Ç , Thermal Time Const. È

Power Consumption

Actuation Energy È , Heating Power È

Complexity

Integration Density Ç , Functionality Ç

Economy

Batch Fab. Pot. Ç (esp. for packaging)


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Nano Mechanical Array Signal Processors (NMASP)


DARPA

Basic Concept: Scaling Guitar Strings μMechanical Resonator

Vib. Amplitude

Guitar String

Low Q High Q 110 Hz

Freq.

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

[Bannon 1996]

Stiffness

Guitar

Freq. Equation: 1 kr fo = 2π m r Freq.

Mass


fo=8.5MHz Qvac =8,000 Qair ~50

Performance: Lr=40.8μm mr ~ 10-13 kg Wr=8μm, hr=2μm d=1000Å, VP=5V Press.=70mTorr

3CC 3λ/4 Bridged μMechanical Filter

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Performance: Performance: fof =9MHz, BW=20kHz, PBW=0.2% o=9MHz, BW=20kHz, PBW=0.2% I.L.=2.79dB, I.L.=2.79dB,Stop. Stop.Rej.=51dB Rej.=51dB 20dB 20dBS.F.=1.95, S.F.=1.95,40dB 40dBS.F.=6.45 S.F.=6.45

VP In

Out

Transmission [dB]

0 -10 -20

Pin=-20dBm

Sharper Sharper roll-off roll-off

-30

Loss LossPole Pole

-40 -50 [S.-S. Li, Nguyen, FCS’05]

-60 8.7

[Li, et al., UFFCS’04]

8.9

9.1

Frequency [MHz]


Design: Lr=40μm Wr=6.5μm hr=2μm Lc=3.5μm Lb=1.6μm VP=10.47V P=-5dBm 9.3 RQi=RQo=12kΩ

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Nanomechanical Vibrating Resonator

• Constructed in SiC material w/ 30 nm Al metallization for magnetomotive pickup

Design/Performance: Design/Performance: μm, Wr =120 nm, h= 75 nm LLr =1.1 r =1.1 μm, Wr =120 nm, h= 75 nm fof =1.029 =1.029GHz, GHz,QQ=500 =500@ @4K, 4K,vacuum vacuum

h

Lr

Wr

Magnetomotive Resp. [nV]

o

[Roukes, Zorman 2002]

Frequency [GHz] C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

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Scaling-Induced Performance Limitations Mass Loading Noise Contaminant Molecules

Temperature Fluctuation Noise

[J. R. Vig, 1999]

Photons

1 k f = o 2π m

Nanoresonator Volume ~10-21 m3

Nanoresonator Mass ~10-17 kg

• Differences in rates of

• Absorption/emission of

photons adsorption and desorption of contaminant molecules ª temperature fluctuations ª mass fluctuations ª frequency fluctuations ª frequency fluctuations • Problem: if dimensions too small @ phase noise significant! • Solution: operate under optimum pressure and temperature


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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) Design/Performance: • Below: 20 μm diameter disk R=10μm, t=2.2μm, d=800Å, VP=7V

Polysilicon Electrode

CVD Diamond μMechanical Disk Resonator

R

Ground Plane

Mixed Amplitude [dB]

Polysilicon Stem (Impedance Mismatched to Diamond Disk)

fo=1.51 GHz (2nd mode), Q=11,555

-84 -86 -88 -90 -92 -94

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

Q = 10,100 (air)

-96 -98 -100 1507.4 1507.6 1507.8


1508

1508.2

Frequency [MHz] [Wang, Butler, Nguyen MEMS’04]

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Miniaturization of RF Front Ends Diplexer Diplexer

RF RFPower Power Amplifier Amplifier

925-960MHz 925-960MHz RF RFSAW SAWFilter Filter

897.5±17.5MHz 897.5±17.5MHz RF RFSAW SAWFilter Filter

1805-1880MHz 1805-1880MHz RF RFSAW SAWFilter Filter

Dual-Band Dual-BandZero-IF Zero-IF Transistor TransistorChip Chip

26-MHz 26-MHzXstal Xstal Oscillator Oscillator

Problem: Problem:high-Q high-Qpassives passivespose poseaa bottleneck bottleneckagainst againstminiaturization miniaturization

3420-3840MHz 3420-3840MHz VCO VCO Antenna

Mixer I

LPF

A/D

Diplexer

Wireless Phone From TX

RF BPF

I AGC

0o 90o LNA

RF PLL RXRF LO

Xstal Osc

Q A/D

Mixer Q C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

LPF

AGC

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Miniaturization of RF Front Ends QQ40,in in44sec sec DIMP

46000

Sandia’s Sandia’smicro-GC micro-GCColumn Column

DEMP

64000

3-methylhexane Toluene DMMP

80000

Solvent

Relative Intensity

Design/Measurement Design/MeasurementData: Data: 0.75m 0.75mxx100μ 100μcolumn column 0.1μ 0.1μDB-5 DB-5stationary stationaryphase phase Heart-cut Heart-cut275 275msec msecpeak peakinjection injection Temperature: Temperature:~30 ~30deg degC/sec C/sec 35-39 psi at 1 psi/sec HH2 carrier: 2 carrier: 35-39 psi at 1 psi/sec

1,6-dichlorohexane

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4.8

DARPA

Basic Approach: Separation Analyzer

Three Analytes

Compacted Slice of Analytes

Separated Analytes

Electronic Processor Pump

Pre-Concentrator

Separator

Detector

Miniaturization

Input Gas Mixture

Tiny TinyDimensions Dimensions ¾¾fast fasttime timeconstants constants Tiny ¾¾10,000X TinyDimensions Dimensions 10,000Xgain gainfactor factor ¾¾faster via fasterseparation separation viamulti-staging multi-staging ¾¾lower ¾¾enhanced lowerpower power enhancedsensitivity sensitivity ¾¾lower power lower power C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

Tiny TinyDimensions Dimensions ¾¾higher highersensitivity sensitivity ¾¾faster fasterrefresh refreshrate rate ¾¾lower lowerpower power ¾¾arrays arraysfor forspecificity specificity

Zeptogram Mass Sensors

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Nanomechanical Resonator

Nanomechanical NanomechanicalResonator Resonator

Shutter

Au Measurement Measurementnoise noiselevel level indicates indicates~7 ~7zg zgof ofresolution resolution 0

-200

-500

~100 zg

-400 -600 -800

100 100zg zgAu Auatom atom clumps clumpsresolved! resolved!

-1000 0

50

100 150 200 250 300 350

100

δ m (zg)

0

Frequency Shift (Hz)

Frequency Shift (Hz)

Nozzle

10

~7 zg

1

-1000 0.1

-1500

0

2000

-2000

Time (sec) C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

>1Hz/zg

133 MHz 190 MHz

-2500 -3000

4000

Time (s)

0

1000

2000

Mass (zeptograms)

3000

4000

ITMS: Scaling Leads to Lower Power

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• Example: ion trap mass spectrometer (ITMS) ª separate analytes by molecular weight

VRF

Detector

Stability Thresholds (dependent on mass)

Detector Output

time

vRF 100 ms

Trapped Ions

time

• Advantages of Miniaturization:

Detector

ª can support smaller mean free path Ö relaxed vacuum req. ª result: substantially lower power requirement


Operation at 1.7 Torr!

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1mm 1mmCylindrical CylindricalIon IonTrap Trap

Resistive ResistiveGlass Glass Drift DriftTube TubeDetector Detector

Detector Current [pA]

Channeltron Channeltron Detector Detector 0.16 0.12 0.08

Mass Massspectrum spectrumof ofDMMP DMMPby byaa single single1-mm 1-mmion iontrap trap@ @1.7 1.7Torr Torr Highest Highestpressure pressure ever everdemonstrated! demonstrated!

0.04

Test TestJig Jig(vacuum (vacuum chamber insert) 90 100 80 chamber insert) C. T.-C. Nguyen, “From MEMS to NEMS: Smaller Is Still Better,” MARC’06 Meeting, 1/25-26/05

110

120

m/z

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40μm-Ion Traps Functional!

Array Arrayof of40μm 40μmSi SiIon IonTraps Traps

Heavily-Doped Polysilicon

Oxide

Aluminum

Silicon Xenon Xenonsignal signalobtained obtainedat at -4 low lowHe Hepressure pressure(10 (10-4Torr) Torr) Xe Xeion ionpeak peak

• Should allow much higher pressure operation (~76 Torr)


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Gas Analyzer Technology Progression

Agilent 6852A Vol: 60,000 cm3 Power: 20 W Energy/Analysis: 18 kJ Analysis Time: 15 min.

Gas GasChromatograph/Mass Chromatograph/Mass Spectrometer Spectrometer(GC/MS) (GC/MS)isis aa“gold “goldstandard” standard”in in chemical gas detection chemical gas detection with withexcellent excellentimmunity immunity to false alarms to false alarms Problems: Problems:too toobig, big,too too slow, power hungry slow, power hungry

LLNL Vol: 40,500 cm3 Power: 11.5 W Energy/Analysis: 10 kJ Analysis Time: 15 min.

¾¾small smallenough enoughfor for projectile delivery projectile delivery ¾¾11ppt pptdet. det.limit limit ¾¾very fast very fast ¾¾battery batteryoperable operable

Sandia μChem Lab Vol: 1,050 cm3 Power: 4.5 W Energy/Analysis: 540 J Analysis Time: 2 min.

Solution: Solution:use useMEMS MEMS technology technologyto tominiaturize miniaturize the GC/MS, which the GC/MS, whichin inturn turn makes it faster and more makes it faster and more energy energyefficient efficient


MGA Objective Vol: 2 cm3 Power: 30X size reduction forTiny small output Ö need small output Ö need accelerometer mechanical element integrated integratedtransistor transistor ª allows integration with IC’stotocompensate circuits circuits compensate

Basic Operation Principle xo

x ∝ Fi = ma

x

Displacement Spring

a

Inertial Force Proof Mass Acceleration Analog Devices ADXL 78


DARPA

Conclusions

• MEMS are micro-scale or smaller devices/systems that operate mainly via a mechanical or electromechanical means • MEMS Ö NEMS offer the same scaling advantages that IC technology offers (e.g., speed, low power, complexity, cost), but they do so for domains beyond electronics:

SizeÈ

resonant frequencyÇ (faster speed) actuation forceÈ (lower power) # mechanical elementsÇ (higher complexity) integration levelÇ (lower cost)

• Micro … nano … it’s all good • Just as important: MEMS or NEMS have brought together

people from diverse disciplines Ö this is the key to growth! • What’s next? Ö Nano-nuclear fusion? Chip-scale atomic sensors?

… limitless possibilities …
