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