What are MEMS

1
What are MEMS?
Micro-Electro-Mechanical Systems (MEMS) is the
integration of mechanical elements, sensors,
actuators, and electronics on a common silicon
substrate through microfabrication technology.
2
What are Microsystems (MST)?

• Tiny, integrated, self-aware, stand-alone
  products, (based on microfabricated components)
  that can

Courtesy of Sandia National Laboratories
3
Microsystems and Nanotechnology

• In Europe, Microsystems is the term of choice.
  Also, Nanotechnology is often used
  interchangeably with Microsystems and MEMS.
  Hence the confusion.

Nano Satellites weigh less than 10kg. The units
depicted here are about the size of a paperback.
4
MEMS Vs. Integrated Circuits (ICs)

• One way to look at it
• ICs move and sense electrons
• MEMS move and sense mass
• Another
• ICs use Semiconductor processing technologies
• MEMS can use a variety of processes including
  Semiconductor but also Bulk, LIGA, Surface
  Micromachining
• Packaging
• IC packaging consists of electrical connections
  in and out of a sealed environment
• MEMS packaging not only includes input and output
  of electrical signals, but may also include
  optical connections, fluidic capillaries, gas
  channels and openings to the environment. A much
  greater challenge.

5
MEMS and ICs

• ICs
• ICs are based on the transistor a basic unit
  or building block of ICs.
• Most ICs are Silicon based, depositing a
  relatively small set of materials.
• Equipment tool sets and processes are very
  similar between different IC fabricators and
  applications there is a dominant front end
  technology base.
• MEMS
• Does not have a basic building block there is
  no MEMS equivalent of a transistor.
• Some MEMS are silicon based and use sacrificial
  surface micromachining (CMOS based) technology.
• Some MEMS are hybrids (different wafer materials
  bonded), some are plastic based or ceramic
  utilizing a variety of processes Surface bulk
  micromachining, LIGA, electrodeposition, hot
  plastic embossing, extrusion on the micro scale
  etc.
• There is no single dominant front end technology
  base but emerging and established MEMS
  applications have started to self-select
  dominant front-end technology pathways (MANCEF
  2nd Roadmap).

6
More on What are MEMS?

• MEMS devices first took off in the sensor
  industry.
• Most MEMS devices have at least one transducer
  element.
• To sense
• To actuate
• Transducer is a device or system that converts
  one form of energy to another force to voltage,
  voltage to force,

7
MEMS Applications

• Accelerometers
• (Inertial Sensors Crash Bags, Navigation,
  Safety)
• Ink Jet Print Heads
• Micro Fluidic Pumps
• Insulin Pump (drug delivery)
• Pressure Sensor
• Auto and Bio applications
• Spatial Light Modulators (SLMs)
• MOEM Micro Optical Electro Mechanical Systems
• DMD Digital Mirror Device
• DM Deformable Mirror
• Chem Lab on a Chip
• Homeland security
• RF (Radio Frequency) MEMS
• Low insertion loss switches (High Frequency)
• Mass Storage Devices

8
MEMS Pressure Sensors

• Pressure Sensors
• 1960s technology
• Used primarily in Aerospace industry at the
  beginning.
• Companies
• Kulite
• Honeywell

Makes use of the Micromachining of glass and
silicon (bulk etching).
When the automotive industry found that these
sensors could help improve engine performance
including gas mileage, these systems become more
and more useful. Really took off in the 70s when
fuel economy starting becoming more important.
9
Pressure Sensors

• TRW Commercial Gas Engine Sensor - 1985

Top view of the TRW (1985) pressure sensor, the
metal components are on top of the silicon
membrane and are stressed when there is a
pressure differential.
10
Ink Jet

• Ink jet printers are MEMS based late 1970s,
  IBM and HP

11
The Accelerometer

• 1987 TRW NovaSensor Accelerometer First
  generation inertial sensor Poppy seed is on top
  to show scale.

Analog Devices 1993 Saab was the first
automobile company to include MEMS accelerometers
to trigger airbags. Combined standard CMOS
technology with MEMS fabrication
MEMS-based systems answered the call of
government regulated passive restraints in
automobiles where these systems sensed rapid
deceleration and in the event of a collision sent
a signal to inflate rapidly an airbag.
12
Increasingly Sophisticated Inertial Sensors Are
Being Developed
Analog Devices and Bosch are leaders in
automotive inertial sensors. Berkeley is a
leader in microsystems research at the University
level. Inertial sensors measure a change in
velocity (acceleration). The first and most
prevalent of these is the crash sensor. A more
recent application is in IBMs ThinkPad Laptop.
13
Hard Drive Magnetic Read/Write Heads

• By incorporating MEMS actuation, the head can
  be positioned more quickly and to finer
  tolerances, this results in higher density data
  capability.

14
Micro Machines

• Surface Micromachining takes off in the 1990s.
• These photos are from Sandia National Laboratories

This basically consists of alternating layers of
structural materials (poly crystalline silicon)
and sacrificial layers (Silicon Dioxide). The
sacrificial layer is a scaffold and acts as a
temporary support and spacing material. The last
step of the process is the release step, where
the sacrificial layer is removed freeing the
structural layers so they can move.
15
MEMS as Machines

• MEMS are often referred to as Micro Machines.
  Tiny devices that move things.

View of a surface micro machined device close
up of a flip mirror with the legs of a mite.
Each gear tooth is 8 microns wide.
16
MOEMs

• Micro Optical Electro Mechanical Systems

MEMS or Microsystems have the potential of
having a greater impact on global business and
society than did the computer chip. - TI
Development started 1980s, first commercial
product - 1996
17
How Small are these Mirrors?
Pin Point
Each mirror is about 17µm square!
Ant Leg
DMD mirrors complete DLP units have over 2
million mirrors all functioning!
18
1996 Micro Optics Bench
Berkeley
There are two mirrors, three Fresnel lenses and
at the far right a semiconductor laser (placed
there after the optic fabrication).
19
Additional Applications of MOEMS
20
Micro Needles

• MEMS needle within the opening of a small
  hypodermic needle
• Smaller size reduces pain and tissue damage now
  there are much smaller MEMS needle arrays.
• The plastic needle array is made through a
  standard MEMS fabrication process to make the
  molds, micro injection process is used to create
  the arrays.

Procter and Gamble Plastic Needle Array
21
Biomedical Applications
Micromachine needles used to deliver drugs
75 microns
Courtesy of Sandia National Laboratories
22
Monolithically Integrated µChemLab
Courtesy of Sandia National Laboratories
23
BioMEMS

• The Overlap between microbiology and
  microsystem feature sizes makes integration
  between the two possible

Atom
24
Nanotechnology Meets MEMS
25
Cantilever Sensors
As mass is added to the cantilever shifts the
resonance frequency.
A gold dot, about 50 nanometers in diameter,
fused to the end of a cantilevered oscillator
about 4 micrometers long. A one-molecule-thick
layer of a sulfur-containing chemical deposited
on the gold adds a mass of about 6 attograms,
which is more than enough to measure. Craighead
Group/Cornell Univeristy
26
Detection of a single E.coli Cell
Single Cell on Cantilever
AFM of E.Coli Cells
Resonance Shift due to Single Cell
From the webpage of Prof. Harold G. Craighead ,
School of Applied and Engineering Physics,
Cornell University
http//www.hgc.cornell.edu/biomems.html
27
Detection of Single DNA
Gold dot 40nm SiN thickness 90nm
By changing the coating (Nano) one can
functionalize the cantilever to detect single
strands of DNA. Mass resolution is on the order
of under 1 ato gram (10-18grams)
http//www.hgc.cornell.edu/Nems20Folder/Enumerati
on20of20Single20DNA.html
28
Cantilever sensors

• Process used to make cantilever sensors Cornell
  Philip S. Waggoner

Cantilever is the MEMS part functionalizing it
is the Nano piece.
29
Mass Storage - IBM
IBMs Millipede 100 Tera Bit per square inch!
30
Mass Storage - Nanochip
Currently 15nm X 15nm per bit density 5nm X 5nm
in the future NAND flash is at 100nm X 100nm per
bit
Uses 1um Semiconductor equipment NAND Flash uses
70nm equipment

• http//www.nanochip.com/tech.htm

31
What is a Cantilever?
A Diving Board!
32
Cantilever

• Cantilevers are used as Sensors
• Cantilevers are used as Switches
• Many MEMS Sensors use the principles of
  Cantilevers as well as RF Swtiches

33
Cantilever

• A cantilever is supported at one end (fixed).
• It has a length, thickness and width (geometry)
• When a force is applied to the end, it deflects

34
Cantilevers as Sensors

• As sensors, Cantilevers can react to the
  environment in two ways
• The resonance frequency can shift (due to a
  change in loading mass)
• The deflection can shift (due to stress)

35
Common Observations

• Consider this about a diving board
• What happens when a little kid bounces on the end
  of the diving board?
• What happens when his large dad bounces on the
  end of the diving board?
• Which one has a higher resonance frequency?

36
MEMS Cantilever sensors

• In MEMS Cantilever sensors, the ends of the
  cantilevers are coated with a layer of probe
  molecules. When a target molecule is present, it
  attaches to the probe molecule, thereby
  increasing the mass. The resonant frequency goes
  down. You just detected the presence of a
  molecule!

37
Actual System
Operation Modes The static mode is used to
obtain information regarding the presence of
certain target molecules in the sample substance.
The surface stress caused by the adsorption of
these molecules results in minute deflections of
the cantilever. This deflection directly
correlates with the concentration of the target
substance. The dynamic mode allows quantitative
analysis of mass loads in the sub-picogram area.
As molecules get adsorbed, minimal shifts in the
resonance frequency of an oscillating cantilever
can be measured and associated to reference data
of the target substance. Both modes can also be
operated simultaneously.
http//www.concentris.com/
This company uses VCSELs as the laser source
(Vertical Cavity Surface Emitting Lasers).
38
MEMS cantilevers as biosensors
1 Dr. Urs Hubler, Concentris GmbH, Davidsbodenstra
sse 63, CH-4056 Basel, Tel. [phone]
55, hubler_at_concentris.ch, www.concentris.com
Reprint from BioWorld 4-2003
39
Resonance Shift
School of Applied and Engineering Physics and the
Nanobiotechnology Center, Cornell University
5 x 15um Cantilever with an E. Coli cell bound to
immobilized antibody layer.
Black is the response before cell attachment, Red
is after cell attachment.
http//www.news.cornell.edu/releases/April04/attog
rams.ws.html
40
Resonance Frequency Shift as a Function of Mass
41
MEMS Cantilevers
42
Two Concepts of Cantilevers as Sensors

• Response to Stress
• Use a laminate cantilever of dissimilar
  materials.
• One material expands or contracts at a different
  rate as another due to absorption, adsorption,
  heat
• Resulting stress gradient (difference in stress)
  causes the cantilever to bend.
• Response to Mass
• Cantilevers are coated with a material which is
  selective to what can adhere to it.
• When the target material adheres to the
  cantilever, its mass changes resulting in a shift
  of the cantilevers resonance (natural) frequency.

43
Applications of MEMS cantilever beams
44
MEMS cantilevers as biosensors
45
BioMEMSVirus Detection
February 4, 2004 Purdue researchers create device
that detects mass of a single virus particle WEST
LAFAYETTE, Ind. Researchers at Purdue
University have developed a miniature device
sensitive enough to detect a single virus
particle, an advancement that could have many
applications, including environmental-health
monitoring and homeland security.The device is a
tiny "cantilever," a diving board-like beam of
silicon that naturally vibrates at a specific
frequency. When a virus particle weighing about
one-trillionth as much as a grain of rice lands
on the cantilever, it vibrates at a different
frequency, which was measured by the Purdue
researchers.
The next step will be to coat a cantilever with
the antibodies for a specific virus, meaning only
those virus particles would stick to the device.
Coating the cantilevers with antibodies that
attract certain viruses could make it possible to
create detectors sensitive to specific pathogens
46
BioSensors Single Cantilever
47
MEMS cantilevers as biosensors
48
E. ColiHow big is this?
49
(No Transcript)
50
MEMS cantilevers as biosensors
51
MEMS cantilevers as biosensors
Origin of nanomechanical cantilever motion
generated from biomolecular interactions