C. T.-C. Nguyen, TEXMEMS, 5/6/03 DARPA DARPA MTO MTO MEMS: Generalizing the Benefits of Miniaturization Clark T.-C. Nguyen Program Manager, MPG/CSAC/MX/HERMIT Microsystems Technology Office (MTO) Defense Advanced Research Projects Agency TEXMEMS’03 May 6, 2003
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C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTO
MEMS: Generalizing the Benefits of Miniaturization
Clark T.-C. NguyenProgram Manager, MPG/CSAC/MX/HERMIT
Microsystems Technology Office (MTO)Defense Advanced Research Projects Agency
TEXMEMS’03May 6, 2003
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOOutline
• Introduction:MEMS technologyintegration with transistors: an early driver for MEMS
• Benefits of MEMSsize reductionspeed, energy conservation, complexity, economy
• Present MEMS Programs in MTONano Mechanical Array Signal Processors (NMASP)Chip-Scale Atomic Clock (CSAC)Micro Power Generation (MPG)
• What’s Next?• Conclusions
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTO
Angle set by mechanical meansto control the path of light
MEMS: Micro Electro Mechanical System
• 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
MEMS
Input:voltage, current
acceleration, velocitylight, heat …
Output:voltage, current
acceleration, velocitylight, heat, …
Control:voltage, current
acceleration velocity
light, heat, …
Transducer to Convert Controlto a Mechanical Variable (e.g., displacement,
velocity, stress, heat, …)
Transducer to Convert Controlto a Mechanical Variable (e.g., displacement,
velocity, stress, heat, …)
[Wu, UCLA]
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOOther Common Attributes of MEMS
• Feature sizes measured in microns or less
• Merges computation with sensing and actuation to change the way we perceive and control the physical world
• Planar lithographic technology often used for fabricationcan use fab equipment identical to those needed for IC’showever, some fabrication steps transcend those of conventional IC processing
• Differences in rates of adsorption and desorptionof contaminant molecules
mass fluctuationsfrequency fluctuations
Temperature Fluctuation Noise
• Absorption/emission of photons
temperature fluctuationsfrequency fluctuations
ContaminantMolecules
mass ~10-13 kg
mk
2π1
of =
Photons
volume ~10-15 m3
• Problem: if dimensions too small phase noise significant!• Solution: operate under optimum pressure and temperature
[J. R. Vig, 1999]
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTO
733 MHz Self-Aligned Radial Contour-Mode Disk μMechanical Resonator
• Self-aligned stem for reduced anchor dissipation• Polysilicon electrodes for better gap stability• Q > 6,000 seen even in air (i.e., atmospheric pressure)!• Below: 20 μm diameter disk
733 MHz Self-Aligned Radial Contour-Mode Disk μMechanical Resonator
• Self-aligned stem for reduced anchor dissipation• Polysilicon electrodes for better gap stability• Q > 6,000 seen even in air (i.e., atmospheric pressure)!• Below: 20 μm diameter disk
1.14-GHz Self-Aligned Radial Contour-Mode Disk μMechanical Resonator
• Self-aligned stem for reduced anchor dissipation• Operated in the 3rd radial-contour mode• Q > 1,500 seen even in air (i.e., atmospheric pressure)!• Below: 20 μm diameter disk
• Goal: create atomic time and frequency reference units with±1µs/day accuracy< 1 cm3 volume< 30 mW power consumption
• Motivation: enable ultra-miniaturized (wristwatch in size) and ultra low power time and frequency references for
high-security communicationsjam-resistant GPS receivershigh-confidence identification of friends and foesultra-sensitive radar (for slow moving objects)efficient spectrum utilization for increased # of usersradio emitter locatorsimproved denial of systems to unauthorized userslonger autonomy period (radio silence interval)missile and munitions guidance
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOGlobal Positioning Satellite Receiver
• Operation based on trilateration: distances to satellites with known locations are used to interpolate the receiver location
d1
d2
L1
L3
Satellite 1
Satellite 3
• Knowledge of satellite locations (L1, L2, and L3) and distances (d1, d2, and d3) to the GPS receiver GPS receiver location
L2
Satellite 2
d3
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOGlobal Positioning Satellite Receiver
• Distance determination based on lags between pseudorandom signals generated by the satellite and receiver
L1
L2
L3
Satellite 1
Satellite 2
Satellite 3
time
ReceiverGenerated
PseudorandomCode
SatelliteTransmitted
PseudorandomCode
Time Lag Between Received And Local
Pseudorandom Codesd3
The more accurate the clock, the better
and faster the determination of
distance (& location)
The more accurate the clock, the better
and faster the determination of
distance (& location)
d1
d2
d3
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOAccurate Portable Timekeepers/Refs.
• Stability quite good at freqs. around 1 kHz
• {fm=1kHz} = -140dBc/Hz
High-Q Oscillators• Tank Q ~ tens of thousands• Example: crystal oscillator
• Quartz: vibrating mechanical resonance high Q, stable
10MHz Excellent stability at offset
frequencies ~1kHz
Excellent stability at offset
frequencies ~1kHz
Accuracy (@ tiny offset freqs.) good, but not good enough for
some applications
Accuracy (@ tiny offset freqs.) good, but not good enough for
• Frequency determined by an atomic transition energy
InterrogatingLaser
InterrogatingLaser
AbsorptionAbsorption
HyperfineTransitionHyperfineTransition
Input EnergyInput Energy
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOAtomic Clock System Requirements
• Atomic clocks are extremely accurate excellent long-term stability (i.e., excellent close-to-carrier phase noise)
• Problem: very low output power poor short-term stability• Solution: lock to another stable reference with larger output
power capability (e.g., microwave source locked to crystal) 852.11 nm laser
Modulated at9 192 631 770 Hz
PhotoDetector
133Cs vapor at 10–7 torr
Mod f
VCXOVCO
÷ N MicrowaveSource Voltage-Controllable
Crystal OscillatorVoltage-Controllable
Crystal Oscillator
10 MHz4.6 GHz
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOChallenge: Miniature Atomic Cell
• Advantage of Size Reduction:lower heating power: can use longer, thinner supports & smaller volume better thermal isolation
• Consequence of Size Reduction:stability compromise:
stability reduction seen as increase in resonance linewidth• Solutions: (to the above)
buffer gases to prevent wall collisionswall coatings to “cushion” collisions
Cell Size Surface-to-Volume Ratio
Atomic CollisionsWith Cell Walls Stability
LargeVaporCell
TinyVaporCell
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOChip-Scale Atomic Clock
• Key Challenges:cell design for maximum QGHz high-Q reference resonatorthermal isolation for low power
Cs or Cs or RbRbGlassGlassDetectorDetector
VCSELVCSEL
SubstrateSubstrate
GHzGHzResonatorResonatorin Vacuumin Vacuum
MEMS andMEMS andPhotonic Photonic
TechnologiesTechnologies
Chip-ScaleAtomic Clock
133Cs vapor at 10–7 torr
VCXOVCO
÷ N MicrowaveSource
10 MHz4.6 GHz
Laser
Vapor CellVapor Cell
PhotoDetector
Atomic Clock Concept
Mod f852.11 nm
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTO
Micro Power Generation (MPG)
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOMPG Program in a Nutshell
• Objective: Generate power at the micro scale to enable standalone micro sensors and micro actuators with wireless communication to realize new systems and strategies for weapons systems, processes and battlefield environments
Sensors
Fuelstorage
Actuators ASIC/CPURF/Optical
Comm
Heat engine/Fuel reformer
Thermal/Exhaustprocessor 1 mm
TE Converter/Fuel cell
• Approach: Harness fuels with higher energy density
0 2 4 6 8 10 12 14Energy Density (kW-hr/kg)
PropaneMethaneGasoline
DieselEthanol
MethanolLi Battery
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTODistributed Autonomous Sensor Networks
AutonomousSensor Node
• Typical Power Requirement: 10-100 μW continuous, 30 mWpulses 4 times per day (on average)
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOApproach: Fuel Cell
• Common elements among fuel cells:fuel storage/deliveryanode and cathode electrodescatalyst to dissociate fuel (e.g., into H+ and e-) at anode and combine products at cathodeion exchange medium (i.e., electrolyte)
Fuel Storage
Vout
ChemicalEnergy
FuelDelivery
ChemicalEnergy
ElectricalEnergyElectrolyte
PorousAnode
Electrode
PorousCathode
Electrode
Catalyst(e.g., platinum)
Load
+
-H+
e-
H+
e-
CO2O2
H2O
ElectricalEnergy
30–40% eff. with reformer
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOApproach: Micro Engine
• Common elements among micro engines:fuel storage/delivery systemcombustion to generate heatactuator (e.g., rotor): convert heat to mechanical motionelectromechanical transducer: convert mechanical motion to electricity
Fuel Storage CombustionChamber
Heat
Actuator(e.g., rotor, piston)
ElectromechanicalTransducer
ElectricityChemicalEnergy
EvaporatedFuel MotionExpanding Gas
ChemicalEnergy
ElectricalEnergy
MechanicalEnergy 1
MechanicalEnergy 2
20% eff.
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOEngine Types: Piston vs. Rotary
• Dominates automobile engine designs
efficientinexpensiveeasy to refuel
• Not ideal for MEMS
• Several combustion strokes occurring at once
• Fewer moving parts: no valves, camshafts, cams, …
• Smoother operation: no reciprocating piston
• More conducive to MEMS!
Piston Engine Rotary Engine
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTOMEMS Rotary Engine Power System
Apex
Housing Top
Housing Bottom
Apex
Housing Top
Housing Bottom
Conformal SiCSurface Layer
Si Deep RIE
MEMSREPS
Package
Packaging
Soft MagneticPole Integration
IntegratedGenerator
Fuel Evaporator
Micro-RotaryEngine
Ultra-Thick DRIEProcess (900 μm)
Apex & FaceSeal Modeling
IntegratedApex Seal
PhaseEruption
EngineControl
Unit ASIC
• To Date: several components now micro-fabricated
[Pisano, UC Berkeley]
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTO
What’s Next?(numerous possbilities)
C. T.-C. Nguyen, TEXMEMS, 5/6/03
DARPADARPA
MTOMTO
MicromechanicalDevice
Microplatform
Substrate
Vibration IsolatingFilter NetworkHeater
TemperatureSensor
VacuumCap
VacuumVacuum
• Objective: attain superior performance and lifetime of MEMS devices via localized control of their operating environments
• Approach: harness MEMS technology to achieve adaptive integrated micro-chambers that actively respond to changes (e.g., temperature, vibration) in their surroundings so as to provide ideal operating environments for contained devices
• The micro-scale advantages:orders of magnitude smaller sizeorders of magnitude less power consumptionorders of magnitude faster thermal time constants
• MEMS are micro-scale or smaller devices/systems that operate mainly via a mechanical or electromechanical means
• MEMS extend the advantages of size reduction beyond the electrical domain, to the mechanical domain
higher speedlower energy consumptionhigher complexity/functionalitylower cost
• What’s next? ideas that capitalize on the advantages of size reduction; multitude of possibilities:
Micro Gas Analyzers for chemical/biological detectionOn-Chip Data Storage for system on a chip applicationsMicro Cryogenic Cooling for targeted on-chip coolingMicro Propulsion for picosatellites and micro-UAVsNano/Micromechanical Circuits for enhanced circuits