1_MEMS - Introduction.pdf

This article discusses MEMS, i.e. Micro-Electro Mechanical Systems.
It gives a rudimentry idea of MEMS technology, its block diagram, applications, advantages and disadvantages. It also gives a brief idea on the working principle of MEMS devices.

1. MEMS
Introduction

2. Contents:
1.Definition
2.InterdisciplinaryTechnology
3.MEMSProcessBlockDiagram
4.MEMSCharacteristics
5.MEMSDeviceSize
6.MEMSSwitchingTypes
7.AdvantagesofMEMS
8.DisadvantagesofMEMS
9.MEMSApplications
10.BasicFabricationStepsofMEMS
Micro-Electro Mechanical Systems 2

3. MEMS Introduction –Definition:
MEMSstandsforMicro-ElectroMechanicalSystems.
Definition-Atechnologicalprocesstodesignanddevelopminiatureintegrateddevicesthat
comprisebothmechanicalandelectrical-electroniccomponents.
MEMSconsists-CentralProcessingUnit(CPU),andstaticandmovingcomponentsinteracting
withthesurroundingenvironment,i.e.micro-sensors.
CalledasMEMSinUSA,Micro-Machines(MM)inJapanandMicrosystemTechnology(MST)
inEurope.
Umbrellatermforawiderangeofmicro-fabricationdesigns,methodsandmechanismsthat
involverealizingmovingmechanicalpartsatmicroscopicscale.
Micro-Electro Mechanical Systems 3

4. MEMS –Interdisciplinary Nature:
Inter-disciplinaryEngineering–
MechanicalEngineering,MaterialScience,
ChemicalEngineering,DesignEngineering,
ElectricalEngineering,ElectronicsEngineering,
OpticalEngineeringandInstrumentationEngineering.
Micro-Electro Mechanical Systems 4
Fig. 1. MEMS Interdependence

5. MEMS –Manufacturing Process Block Diagram:
Comprehensive Block Diagram of MEMS Manufacturing Process.
Micro-Electro Mechanical Systems 5
Fig. 2. Block Diagram of MEMS Manufacturing

6. MEMS –Characteristics:
TheintrinsiccharacteristicsofMEMS-baseddevicesare:
1.Miniaturization(1μmto1cm)
2.ElectronicIntegration
3.PrecisionControlofPhysicalDimensions.
4.ParallelFabrication
5.CostEffectiveBatchFabrication.
Micro-Electro Mechanical Systems 6

7. MEMS –Characteristics:
Miniaturizationleadsto:
1.Highresonancefrequency(rangingfromHztoMHz).
2.Enhancedsensitivity(outputat5psi/34kPa/345mbarat100millivolts(mV)).
3.GoodStability(greateraccuracywithmarginaldrift).)
4.Lowthermalmassandthermalhysteresis(thermalhysteresisoffsetof<0.05%FSO).
ElectronicIntegrationleadsto:
1.Seamlessintegrationofmechanicalsensorsandactuatorwithelectronicprocessors.
2.Monolithicintegration(completecircuitonasinglepieceofsilicon).
3.Improvedsignalqualityduetoreducednoise.
ParallelFabricationleadsto:
1.Highaspectratio(ratioofwidthtoheight).
2.Highuniformityacrosswafer.
3.Highprecisionandmultidimensionalfeatures.
Micro-Electro Mechanical Systems 7

8. MEMS –Device Size:
FabricatedbyusingICbatchprocessmanufacturingtechniques.
Miniaturizedsizeleadstoconsumeslowpower,andmaintainingofveryhighisolation.
Comprises–simplestatictocomplexstructuresmulti-movingparts.
Size–Fewmicro-meterstomillimetres.
Influence–Macro-scalecontrolelementsanddevices.
Builtofcomponents-1and100μminsize(i.e.,0.001to0.1mm).
MEMSdevicerange-20μmto1millimetre(i.e.,0.02to1.0mm).
Althoughcomponentsarrangedinarrays(e.g.,digitalmicro-mirrordevices)canbemorethan
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Micro-Electro Mechanical Systems 8

9. MEMS –Switch Types:
There are two basic types of MEMS switching technology: Capacitive and Ohmic.
1.Capacitive MEMS switchesare developed using a moving plate or sensing element, which
changes the substrate capacitance (right-hand figure).
2.OhmicMEMS switchesare controlled by electrostatically controlled cantilevers (left-hand
figure).
OhmicMEMS switchescan fail from metal fatigue of the MEMS actuator (cantilever) and
contact wear, since cantilevers can deform over time.
Micro-Electro Mechanical Systems 9
Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two electrically charged objects caused by
contact, an electrical short or dielectric breakdown.

10. MEMS –Advantages:
AdvantagesofMEMS:
1.Smallsize,dimension&weight.
2.Consumptionofverylowpower.
3.Highproductivity(Batchfabricatedinlargearrays).
4.Superiorperformance&Widerangecompatibility.
5.Lowcost.
6.Easytointegrateandmodifyintosystems.
7.Smallthermalconstant,&Improvedthermalexpansiontolerance
8.Negligiblethermalhysteresis.
9.Resistanttoshock,vibrationandradiation.
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11. MEMS –Disadvantages:
DrawbacksinMEMS:
1.Significantpowertransferischallengingduetotheirexcessiveminiaturizedsize.
2.Thewafermaterialcannotbeexposedtolargeloadsasthatmightdamagethewafer.
3.HighcostinvolvementintheResearch&Developmentstages.
4.Itisstilladevelopingfield,andthereforereliabilityattimesisaconcern.
Micro-Electro Mechanical Systems 11

12. MEMS –Applications:
MEMS-capabletosense,controlandactuateonmicroscales.
MEMS-applicationsinelectroniccontrolandbio-sensingapplications.
MEMSdevicesfindwidespreadapplicationsin:
1.Navigationfield.
1) MarineenvironmentandGeo-mapping.
2) NaturalResourceIdentificationlikeOilandGasexploration.
2.EnvironmentalStudies.
1) MEMSbarometer.
2) Weatherpredictions.
3) Waterqualitymonitor.
4) Aquaticandoceanecologystudies.
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13. MEMS –Applications:
3.Biomedicalapplications.
1) Bio-cavityLasertodistinguishbetweencancerousandnon-cancerouscells.
2) SmartPill–bodyimplantationandautomaticdrugdelivery.
3) SyntheticEyesight–MEMSbasedarrayinsertedinretinatoinstilpartialvision.
4) Lab-On-Chip,MicroTotalAnalyser,embeddedmedicaldevices,viz.stents.
4.Securityandsurveillance.
1) MEMSgyroscopeindrones.
2) InertialNavigationSystem(INS)tofacilitateauto-pilot.
5.MilitaryOperation.
1) Pressuresensingforanti-torpedoweaponry.
2) SubmarineDetection.
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14. MEMS –Applications:
6.Highfrequencycircuitdesigns.
1) Micro-actuationinmicro-scaledevices.
2) MEMSswitches.
3) Micro-pumps.
4) Micro-levers.
5) Micro-grippers
7.MicroscaleEnergyHarvester
1) Micro-piezoelectriccrystals.
2) Electrostaticenergyharvesters.
3) Electromagneticenergyharvesters.
8.Microscopy
1) Scanningprobemicroscope.
2) AtomicForcemicroscope.
Micro-Electro Mechanical Systems 14

15. MEMS –Applications:
ThetablebelowhighlightsthemajorMEMSapplications.
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Automotive Electronics Medical Communication Defence
InternalNavigationDiskDriveheads BloodPressureSensorsFibre-opticnetwork
components
Munitionsguidance
Air conditioning
compressorsensors
InkjetprinterheadsMusclestimulatorsand
drugdeliverysystem.
RFRelays,switchesand
filters
Surveillance.
Brakeforcesensors,
suspensioncontrol
accelerometers.
Projectionscreen
television.
Implanted pressure
sensors.
Projectiondisplaysin
portablecommunication
devices.
Armingsystems.
Fuelleveland
vapour pressure
sensors.
Earthquakesensors.Prosthetics. Voltage Controlled
Oscillators(VCO)
EmbeddedSensors.
Airbagsensors. Avionicspressure
sensors.
Miniatureanalytical
instruments.
Splittersandcouplers.Datastorage.
Intelligenttyres. Massdatastorage
systems.
Pacemakers. TuneableLASER Aircraft/Missile
Control.

16. MEMS –Basic Fabrication Steps:
MEMSbecamepracticaloncetheycouldbefabricatedusingmodifiedsemiconductordevice
fabricationtechnologies,normallyusedisElectronics.
MEMSfabricationsteps:
1.Moulding and Plating (Deposition –Physical and Chemical)
2.Patterning (Lithography)
3.Ethching(Wet & Dry)
Wet etching (KOH –Potassium Hydroxide, TMAH –Tetra-methyl-ammonium
Hydroxide)
Dry etching (RIE -Reactive Ion Etchingand DRIE –DeepReactive Ion Etching),
4.Electrical Discharge Machining (EDM),
5.Micro-machining (Bulk, Surface, High Aspect Ratio (HAR)).
6.Packaging
Micro-Electro Mechanical Systems 16

17. References:
1.P.Chttps://www.mems-exchange.org/MEMS/what-is.html
2.P.Chttps://www.bosch-sensortec.com/about-us/our-company/mems-expertise/
3.P.Chttps://wpo-altertechnology.com/mems-packaging/
4.Gabriel K, Jarvis J, Trimmer W (1988).Small Machines, Large Opportunities: A Report on the Emerging
Field of Microdynamics: Report of the Workshop on MicroelectromechanicalSystems Research.National
Science Foundation(sponsor). AT&T Bell Laboratories.
5.WaldnerJB(2008).Nanocomputersand Swarm Intelligence. London:ISTEJohn Wiley & Sons.
p.205.ISBN9781848210097.
6.Angell JB, Terry SC, Barth PW (1983). "Silicon Micromechanical Devices".
7.Sci. Am.248(4): 44–55
8.Bibcode:1983SciAm.248d..44A.doi:10.1038/scientificamerican0483-44.
9.Dirk K. de Vries(2005). "Investigation of gross die per wafer formulas". IEEE Transactions on
Semiconductor Manufacturing. 18 (February 2005): 136–139.
10.https://en.wikipedia.org/wiki/Flexural_strength
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