Transcript Introduction to MEMS - MicroFlex

Introduction to MEMS
• What is MEMS?
• SWhat
do MEMS devices look like?
Beeby, J Tudor, University of Southampton
• What can they do?
• How do we make them on textiles?
MICROFLEX
S Beeby, J Tudor, University of Southampton
What are MEMS?
MEMS – MicroElectroMechanical Systems
S Beeby, J Tudor, University of Southampton
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.
MICROFLEX
S Beeby, J Tudor, University of Southampton
Scales and Dimensions - MEMS
MEMS
S Beeby, J Tudor, University of Southampton
10-6
Pollen
MICROFLEX
10-5
10-4
Human hair
(f 80-100mm)
10-3
10-2
10-1
Silicon die
(5 x 5 mm)
S Beeby, J Tudor, University of Southampton
10-0
10-1
Example 1 - Inertial MEMS
Mechanical
component
S Beeby, J Tudor, University of Southampton
Signal
Processing
Integrated
electronics
Silicon
substrate
Integrated mechanical and electrical components
Smart microsensor systems
MICROFLEX
S Beeby, J Tudor, University of Southampton
Example 2: Optical MEMS - DLP
S Beeby, J Tudor, University of Southampton
Texas Instruments
Digital Light Processors
1.3 million mirrors, 13mm
Wide, used in projectors.
http://www.dlp.com/includes/demo_flash.aspx
MICROFLEX
S Beeby, J Tudor, University of Southampton
Factors to Consider
• MEMS requires a mechanical structure
specifically designed for the application
S Beeby,
J Tudor, University ofprocess
Southampton
• The
fabrication
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
MICROFLEX
S Beeby, J Tudor, University of Southampton
Example 3: Pressure
Sensors
Pressure sensors utilise an thin
membrane formed on or in the silicon
chip.
S Beeby, J Tudor, University of Southampton
Photo from GE Novasensor – Catheter pressure sensors
Pressure
Sensing mechanism detects the
movement of the diaphragm.
Signal conditioning electronics
integrated on the same die.
MICROFLEX
S Beeby, J Tudor, University of Southampton
Microfluidics
MEMS designed to handle or process minute quantities of
liquids. Devices include micro-pumps, micro-mixers, flow
channels,
reaction chambers, micro-filters.
S Beeby, J Tudor, University of Southampton
Example micropump
MICROFLEX
S Beeby, J Tudor, University of Southampton
S Beeby, J Tudor, University of Southampton
MICROFLEX
Sensors & Transducers Magazine (S&T e-Digest), Vol.66, Issue 4, April 2006, pp.521-525
S Beeby, J Tudor, University of Southampton
Micromachining
This is the process of fabricating mechanical components
in the micron to millimetre size range.
• Typically based upon
S Beeby, J Tudor, University of Southampton
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
MICROFLEX
Denso Corporation
S Beeby, J Tudor, University of Southampton
Silicon Micromachining Processes
Typically based upon IC fabrication processes which enable:
• Simultaneous device processing on each wafer
• Batch fabrication (many wafers simultaneously)
S Beeby,
J Tudor,
of Southampton
• Low
cost
inUniversity
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)
MICROFLEX
S Beeby, J Tudor, University of Southampton
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 /
S Beeby, J Tudor, University of Southampton
depositing
layers of materials, patterning and selectively
removing them
Structure
Substrate
MICROFLEX
S Beeby, J Tudor, University of Southampton
Surface Micromachining (2)
Example on silicon:
Poly Si
Silicon
S Beeby, J Tudor, University of Southampton
Silicon Nitride
Dry etch
Silicon Dioxide
Wet etch
Dry etch
MICROFLEX
S Beeby, J Tudor, University of Southampton
Recommended Reading!
MEMS Mechanical Sensors
S Beeby, J Tudor, University of Southampton
by Steve P. Beeby, Graham Ensell,
Michael Kraft and Neil White
£62 on Amazon
MICROFLEX
S Beeby, J Tudor, University of Southampton