NANO-ELECTRO-MECHANICAL
SYSTEM(NEMS)
CONTENTS
Introduction
Benefits of Nano-machines
Fabrication of NEMS device
Advantages
Applications
Summary
INTRODUCTION
Nano-Electro-Mechanical
system
(NEMS)
is
the
integration of mechanical elements, sensors, actuators
and electronics on a common silicon substrate.
The Nano mechanical components are fabricated using
compatible “micromachining” process.
NEMS is the enabling technology allowing the
development of smart products.
Nano
electro
revolutionize
mechanical
measurements
devices
of
promise
extremely
to
small
displacement and extremely weak forces, particularly at
the molecular level.
NEMS devices can be so small that hundreds of them
can be fit in the same space as one single micro device
that performs same function.
In Nems devices the sensors gather the information from
surrounding
environment
through
measuring
mechanical, chemical, biological, chemical and optical
phenomenon.
The electronics then process the information derived
form the sensors.
Through some decision making capability direct the
actuators to respond by moving, regulating and filtering.
BENEFITS OF NANO MACHINES
Nano-Mechanical devices promise to revolutionize
measurements of extremely
small displacements and
forces.
Can built with the masses approaching a few
attograms(10-18g) and with the cross section of 10nm.
A second important attribute Nano machines is that they
dissipate less energy.
NEMS are extremely sensitive for the external damping
mechanisms which is crucial for building sensors.
The Geometry of a NEMS device can be tailored so that
the vibrating elements reacts only to external forces in a
specific direction.
NEMS are ultra low power devices.
Fundamental power scale is defined by the thermal
energy divided by the response time
FABRICATION OF NEMS DEVICE
There are three Basic building blocks in NEMS
technology.
Deposition processes.
Lithography.
Etching processes.
Deposition Process :
One of the basic building blocks in NEMS processing is
the ability to deposit thin films of materials.
Thin
films of thickness of about few nm to about
100 nm.
Chemical methods used in NEMS deposition
process.
o Chemical vapour deposition.
o
Epitaxy.
Chemical vapour deposition :
Fig. 1: Typical hot-wall LPCVD reactor
Epitaxy
:
Fig 2: Typical cold-wall vapour phase
epitaxial reactor
Lithography
:
Lithography in the NEMS context is typically the
transfer of a pattern to a photosensitive material by
selective exposure to a radiation source such as light.
A photosensitive material is a material that experiences a
change in its physical properties when exposed to a
radiation source.
Pattern Transfer :
Fig 3: Transfer of a pattern to a photosensitive material
Figure 4:a) Pattern definition in positive resist, b) Pattern definition in
negative resist.
Alignment :
Inorder to make useful devices the patterns for different
lithography steps that belongs to a single structure must
be aligned to one another.
The first pattern includes a set of alignment marks.
The first pattern alignment marks used as the reference
when positining subsequent patterns.
Exposure :
This parameter is required in order to achive accurate
pattern transfer from the Mask to the photo sensitive
layer.
Different Photo resist exhibit different sensitivity to
different wavelengths
Etching
It
:
is necessary to etch the thin films previously
deposited or the substrate itself.
There
are 2 class of etching process.
Wet etching.
Dry etching.
Wet etching :
This is the simplest etching technology.
There are complications since usually Mask is desired to
selectively etch the material.
It requires a container with a liquid solution that dissolve
the material used.
Some single crystall material, such as silicon, exhibits
anistropic etching in certain chemicals.
ADVANTAGES
o
Cost effectiveness.
o
System integration.
o
High Precision.
o
Small size.
APPLICATIONS
OF NEMS
Accelerometer :
NEMS
accelerometers
conventional
are
accelerometers
quickly
for
deployment systems in automobiles.
Figure 6 : Accelerometer(air bags)
crash
replacing
air-bag
Nano nozzles:
Another wide deployment of NEMS is their use as nano
nozzles that direct the ink in inkjet printers.
They are also used to create miniature robots (nano-
robots) as well as nano-tweezers.
NEMS have been rigorously tested in harsh
environments for defense and aerospace where they are
used as navigational gyroscopes.
NEMS in Wireless :
A 3G “smart” phone will require the functionality of as
many as five
radios – for TDMA, CDMA, 3G,
Bluetooth and GSM operation. A huge increase in
component count is required to accomplish this demand.
Thermal actuator :
Thermal actuator is one of the most important NEMS
devices, which is able to deliver a large force with large
displacement.
SUMMARY
Nano-systems have the enabling capability and potential
similar to those of nano-processors .
Since NEMS is a nascent and synergistic technology,
many new applications will emerge, expanding the
markets beyond that which is currently identified or
known.
NEMS is forecasted to have growth similar to its parent
IC technology.
For a great many applications, NEMS is sure to be the
technology of the future.
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