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 mechanical devices promise to

revolutionize measurements of extremely 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 are quickly replacing

conventional accelerometers for crash air-bag

deployment systems in automobiles.

Figure 6 : Accelerometer(air bags)

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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