http://www.d-r-t.com/sensortech.htm

Chris Mosser

http://news.thomasnet.com/fullstory/463874

Outline

• Introduce MEMS• Applications• Automotive Specific Information• Fabrication• Packaging

• Micro(small)

• Electro(electric components/functionality)

• Mechanical(mechanical components/functionality)

• Systems(integrated, system-like functionality)

What are MEMS?

http://eed.gsfc.nasa.gov/562/SA_MEMs.htm

http://www.memx.com/

http://www.memx.com/

http://www.forbes.com/2008/04/22/mems-apple-nintendo_leadership_clayton_in_jw_0421claytonchristensen_inl_slide.html

Where do you find MEMs?• Printers

– High DPI inkjets • Projectors

• Micro-Mirrors from Texas Instruments

• Cell Phones– Knowles Microphones used in most new cell

phones • Automobiles

Why MEMS

• Small– Typically .1-100um feature size

Human Hair thickness ~ 50um

http://www.vendian.org/envelope/dir2/scaling_construct.html

http://singularityhub.com/wp-content/uploads/2008/08/red-blood-cells.bmp

Red Blood Cells ~ 10um

Why MEMS

• Low cost, High yield– Use existing IC fabrication technology

– Made primarily on Silicon Wafers

http://media-2.web.britannica.com/eb-media/22/78522-004-BB539CA9.jpg

Why MEMS

• Favorable scaling for a lot of applications– Flow-rate sensors– Electrostatics– Magnetism– Many others

• Not all applications– Solar Power– Turbulent Boundary Energy Harvesting

Typical Applications

• Accelerometers• Magnetometers• Microphones• Micro-Fluidics• RF-MEMS• Bridge to Nanotechnology

Automotive MEMS• MEMS Sensors and Actuators used to

control various elements of the automobile– Powertrain and Chassis control

• Ex: Manifold Air Temperature – Comfort and Convenience

• Ex: Air-Temperature Control– Communications

• Ex: Wireless

Where it Began• 1979 - First recorded use of MEMs in automobiles• Federal emission standards required monitoring the air-to-

fuel ratio of the engine– Density of air value was needed

• Many different sensor technologies were introduced to solve this problem

• MAP (manifold absolute pressure) and MAT (manifold air temperature) sensors were developed using MEMS

• Silicon based MEMS sensors became the device of choice due to low cost and high yield

MAP Sensorhttp://www.quantummatrix.com.my/v1/content/view/231/59/

Who Developed It• Two groups

– Delco Electronics Group(General Motors)• Used piezoresistive sensing

– Ford• Used capacitive sensing

Piezoresistive Sensors

• Use the piezoresistive effect– Applied stress changes resistivity of material

Diaphragm with two embedded piezoresisters

Source: IMG(UF)

Capacitive Sensors• Vary two parameters

– Gap – Overlap area

• Advantages– Low power– High accuracy– Temperature independent

• Important for a lot of automobile applications– Reciprocal

• Disadvantages– Parasitic capacitance– Small signal

http://www.nanoshift.net/Technology.htm

What about Actuators?

• Traditionally only sensors were developed for automobiles

• Actuators started to become popular as MEMs development costs decreased

• Popular actuators include– Microphones– Fuel injection nozzles

Fabrication• Use basic IC fabrication

– Masks/layers/CVD/oxidation/etc

• MEMS specific fabrication– DRIE (Deep reactive ion etch)– SOI (silicon on insulator)

General MEMS Packaging• The most important and expensive part of a

MEMS sensor/actuator– ~45% of the cost of designing a MEMS device is spent

on packaging• Often times packaging constraints will prevent a

design from being produced– May require too complex of a package design for

realistic implementation• Package can greatly change the response of a

device– Sensitivity/Dynamic Range/etc all effected by package

Automotive MEMS Packaging• Automotive sensors generally only allowed

to have 3 wires connected to them– Minimizes cost

• Environment concerns are especially important in automotive applications– Engine heat – High acceleration/deceleration– Humidity

Automotive MEMS Summary

Precision Engineering By V. C. Venkatesh, Sudin Izman

Thank You

References

• Application of MEMS Technology in Automotive Sensors and Actuators, David Eddy and Douglas Spanks

• http://www.img.ufl.edu/ms/eel5225/html/assignments.htm