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Introduction to MEMS

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Title: Slide 1 Author: Steve Beeby Last modified by: John Created Date: 1/9/2003 11:49:12 AM Document presentation format: On-screen Show Company: ECS – PowerPoint PPT presentation

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Title: Introduction to MEMS


1
Introduction to MEMS
  • What is MEMS?
  • What do MEMS devices look like?
  • What can they do?
  • How do we make them on textiles?

2
What are MEMS?
  • MEMS MicroElectroMechanical Systems
  • Systems that combine mechanical and electrical
    functionality fabricated in dimensions that range
    from microns to millimetre
  • Typically use silicon as the substrate due to its
    semiconducting characteristics and excellent
    mechanical properties.

3
Scales and Dimensions - MEMS
MEMS
Human hair (f 80-100mm)
Silicon die (5 x 5 mm)
Pollen
4
Example 1 - Inertial MEMS
Mechanical component
Signal Processing Integrated electronics
Silicon substrate
Integrated mechanical and electrical components
Smart microsensor systems
5
Example 2 Optical MEMS - DLP
Texas Instruments Digital Light Processors 1.3
million mirrors, 13mm Wide, used in projectors.
http//www.dlp.com/includes/demo_flash.aspx
6
Factors to Consider
  • MEMS requires a mechanical structure specifically
    designed for the application
  • The fabrication process must be considered at the
    outset since this defines dimensional limits and
    material properties
  • MEMS are typically sensors or actuators -
    requires a microscale transducer
  • Most MEMS use silicon but plastics, ceramics and
    glasses can be used

7
Example 3 Pressure Sensors
Pressure sensors utilise an thin membrane formed
on or in the silicon chip.
Photo from GE Novasensor Catheter pressure
sensors
Pressure
Sensing mechanism detects the movement of the
diaphragm. Signal conditioning electronics
integrated on the same die.
8
Microfluidics
MEMS designed to handle or process minute
quantities of liquids. Devices include
micro-pumps, micro-mixers, flow channels,
reaction chambers, micro-filters.
Example micro-pump
9
Sensors Transducers Magazine (ST e-Digest),
Vol.66, Issue 4, April 2006, pp.521-525
10
Micromachining
This is the process of fabricating mechanical
components in the micron to millimetre size
range.
  • Typically based upon silicon IC fabrication
    processes (see next slide). Especially true for
    micron scale devices.
  • Also includes traditional approaches
    (precision CNC machining, electroplating,
    molding)
  • Variety of materials

Denso Corporation
11
Silicon Micromachining Processes
  • Typically based upon IC fabrication processes
    which enable
  • Simultaneous device processing on each wafer
  • Batch fabrication (many wafers simultaneously)
  • Low cost in high volumes
  • Inherently small size (nanometres to
    millimetres)
  • But Beware!
  • High cost of infrastructure (both initial and
    running)
  • High cost of equipment
  • Specialist processes often required
  • (poor standardisation)

12
Surface Micromachining
  • Mechanical structures formed on the surface of a
    substrate.
  • Formed from materials deposited on the substrate.
    Most
  • common method of surface micromachining is known
    as
  • Sacrificial Layer Technology. Additive process
    growing / depositing layers of materials,
    patterning and selectively removing them

13
Surface Micromachining (2)
Example on silicon
Silicon
Silicon Nitride
Silicon Dioxide
Wet etch
14
Recommended Reading!
MEMS Mechanical Sensors by Steve P. Beeby,
Graham Ensell, Michael Kraft and Neil White 62
on Amazon
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