This document discusses MEMS (Micro-Electro-Mechanical Systems) sensors and actuators used in automotive applications. It outlines that MEMS were first used in automobiles in 1979 to monitor air-fuel ratios using pressure and temperature sensors. Major automakers like GM and Ford developed these early MEMS sensors. The document describes common MEMS devices like accelerometers, microphones, and fluidic systems used in vehicles. It provides details on MEMS fabrication using IC processes and specialized techniques like DRIE. Finally, it notes that automotive MEMS packaging presents unique challenges like harsh environments and low wire counts that drive up the cost significantly.

1. http://www.d-r-t.com/sensortech.htm
Chris Mosser
http://news.thomasnet.com/fullstory/463874

2. Outline
• Introduce MEMS
• Applications
• Automotive Specific Information
• Fabrication
• Packaging

3. • 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

4. 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

5. 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

6. 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

7. 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

8. Typical Applications
• Accelerometers
• Magnetometers
• Microphones
• Micro-Fluidics
• RF-MEMS
• Bridge to Nanotechnology

9. 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

10. 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 Sensor
http://www.quantummatrix.com.my/v1/content/view/231/59/

11. Who Developed It
• Two groups
– Delco Electronics Group(General Motors)
• Used piezoresistive sensing
– Ford
• Used capacitive sensing

12. Piezoresistive Sensors
• Use the piezoresistive effect
– Applied stress changes resistivity of material
Diaphragm with two embedded piezoresisters
Source: IMG(UF)

13. 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

14. 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

15. Fabrication
• Use basic IC fabrication
– Masks/layers/CVD/oxidation/etc
• MEMS specific fabrication
– DRIE (Deep reactive ion etch)
– SOI (silicon on insulator)

16. 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

17. 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

18. Automotive MEMS Summary
Precision Engineering
By V. C. Venkatesh, Sudin Izman

19. Thank You

20. References
• Application of MEMS Technology in
Automotive Sensors and Actuators,
David Eddy and Douglas Spanks
• http://www.img.ufl.edu/ms/eel5225/html/as
signments.htm