MEMS: microelectromechanicalsystems

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MEMS micro-electromechanical-systems
Example silicon gear wheels (smallest is about
50mm diameter)
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Sandia
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• Applications include
• Sensors (e.g. in cars),
• RF (e.g. 3G mobile phones),
• Optoelectronics (including astronomy),
• Biomedical applications.

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Historical development

• 1970s pressure sensors
• 1980s surface-micromachined polysilicon
  actuators for disc drive heads
• 1991 single-chip MEMS accelerometers for
  automotive airbags
• 1992 first micro-machined hinge

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Estimated MEMS market
Source Yole Développement
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• Vehicle applications
• Tyre pressure sensor.
• Airbag accelerometer sensors
• Fuel sensors
• Engine and brake controls
• Noise cancellation
• Intelligent tyres" that alert the driver to a
  flat

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• Biomedical applications
• Pharmaceutical industry (for testing new drugs)
• Blood-screening sensors for bed-side lab tests
• Networks of channels, pumps, valves, and mixers
  for analytical devices
• Moulds for plastic microfluidic parts

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• Future biomedical applications
• Miniature surgical tools
• Fluid dispensing heads
• Drug delivery
• Implantable sensors

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• Other applications
• Nulti-axis accelerometers
• Inkjet printheads
• Scanners
• Gyros
• Force and displacement transducers
• Miniature solenoids
• Inertial sensors that can withstand more than
  15,000 g for artillery shells

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• Other applications (cont.)
• RF switches and relays, inductors, transmission
  lines, filters, antennas, and transformers
• Optoelectronics include 2-D and 3-D micromirrors
  optical attenuators, and fiber alignment and
  packaging aids
• Future Microfluidic devices with miniature
  pumps and valves to remove heat from electronics

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• MEMS manufacturing technologies
• Bulk micromachining
• Surface micromachining
• High-aspect-ratio micromachining (HARM)
• Electro-discharge micromachining (EDM)

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• MEMS manufacturing technologies
• Bulk micromachining
• The whole thickness of a silicon wafer is used
  for building the micro-mechanical structures.
• Silicon is machined using various etching
  processes

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• MEMS manufacturing technologies
• Surface micromachining
• Uses layers deposited on surface of a substrate
• Created in late 1980's to render MEMS compatible
  with planar IC technology
• Goal combining MEMS and ICs on same silicon wafer

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• MEMS manufacturing technologies
• High-aspect-ratio micromachining (HARM)
• Deep reactive ion etching
• Structural layer thickness in range 10 µm to 100
  µm (compared to 2 µm with surface machining)

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• Silicon surface micromachining
• Uses the same equipment and processes as IC
  manufacturing
• Applications include actuators, electrostatic
  motors, mirrors and accelerometers

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• Silicon surface micromachining (cont.)
• Polycrystalline silicon (polysilicon) has a
  strength of 2 to 3 GPa (compare steel 200 MPa to
  1 GPa)
• Polysilicon is extremely flexible and it does not
  readily fatigue

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Polysilicon tweezers gripping a polysilicon gear
wheel
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Channels in a substrate for microfluidics
applications
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Fabrication design rules impose limited
separation (hence sloppy gears)
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High aspect-ratio fabrication
http//www.mcnc.org/
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Digital micromirror (TI) Example of application
2000 by 1000 array of 16mm by 16mm mirrors for
projection system
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Integration of mechanical components with
micro-mechanical systems
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• Other material available through
• www-ist.massey.ac.nz/rbrowne
• includes
• Overview of MEMS
• Adaptive optics
• Optical MEMS
• Automotive applications
• Example of a biometric application
• MUMPS device gallery
• Also http//mems.colorado.edu/c1.res.vid/
• See especially rotarysteppermotor.avi (3.0MB)

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A useful reference is A (not so) short
Introduction to Micro Electromechanical Systems",
F. Chollet, HB. Liu, version 2.1, Jul. 2007,
http//memscyclopedia.org/introMEMS.html It is
also available for download at http//www-ist.mas
sey.ac.nz/143457/ (file name introMEMS.pdf,
size 1.4MB)