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sensors
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Chris Mosser
OutlineIntroduce MEMSApplicationsAutomotive Specific InformationFabricationPackaging
What are MEMS?Micro(small)
Electro(electric components/functionality)
Mechanical(mechanical components/functionality)
Systems(integrated, system-like functionality)
Where do you find MEMs?PrintersHigh DPI inkjets ProjectorsMicro-Mirrors from Texas InstrumentsCell PhonesKnowles Microphones used in most new cell phones Automobiles
Why MEMSSmallTypically .1-100um feature size
Why MEMSLow cost, High yieldUse existing IC fabrication technology
Made primarily on Silicon Wafershttp://media-2.web.britannica.com/eb-media/22/78522-004-BB539CA9.jpg
Why MEMSFavorable scaling for a lot of applicationsFlow-rate sensorsElectrostaticsMagnetismMany others
Not all applicationsSolar PowerTurbulent Boundary Energy Harvesting
Typical ApplicationsAccelerometersMagnetometersMicrophonesMicro-FluidicsRF-MEMSBridge to Nanotechnology
Automotive MEMSMEMS Sensors and Actuators used to control various elements of the automobilePowertrain and Chassis controlEx: Manifold Air Temperature Comfort and ConvenienceEx: Air-Temperature ControlCommunications Ex: Wireless
Where it Began1979 - First recorded use of MEMs in automobilesFederal emission standards required monitoring the air-to-fuel ratio of the engineDensity of air value was neededMany different sensor technologies were introduced to solve this problemMAP (manifold absolute pressure) and MAT (manifold air temperature) sensors were developed using MEMSSilicon based MEMS sensors became the device of choice due to low cost and high yield
Who Developed ItTwo groupsDelco Electronics Group(General Motors)Used piezoresistive sensingFordUsed capacitive sensing
Piezoresistive SensorsUse the piezoresistive effectApplied stress changes resistivity of material
Capacitive SensorsVary two parametersGap Overlap areaAdvantagesLow powerHigh accuracyTemperature independentImportant for a lot of automobile applicationsReciprocalDisadvantagesParasitic capacitanceSmall signal http://www.nanoshift.net/Technology.htm
What about Actuators?Traditionally only sensors were developed for automobilesActuators started to become popular as MEMs development costs decreasedPopular actuators includeMicrophonesFuel injection nozzles
FabricationUse basic IC fabricationMasks/layers/CVD/oxidation/etc
MEMS specific fabricationDRIE (Deep reactive ion etch)SOI (silicon on insulator)
General MEMS PackagingThe most important and expensive part of a MEMS sensor/actuator~45% of the cost of designing a MEMS device is spent on packagingOften times packaging constraints will prevent a design from being producedMay require too complex of a package design for realistic implementationPackage can greatly change the response of a deviceSensitivity/Dynamic Range/etc all effected by package
Automotive MEMS PackagingAutomotive sensors generally only allowed to have 3 wires connected to themMinimizes costEnvironment concerns are especially important in automotive applicationsEngine heat High acceleration/decelerationHumidity
Automotive MEMS SummaryPrecision EngineeringBy V. C. Venkatesh, Sudin Izman
Thank You
ReferencesApplication of MEMS Technology in Automotive Sensors and Actuators, David Eddy and Douglas Spanks
http://www.img.ufl.edu/ms/eel5225/html/assignments.htm
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