NANO-ELECTRO-MECHANICAL SYSTEM(NEMS)

CONTENTSIntroductionBenefits of Nano-machinesFabrication of NEMS deviceAdvantagesApplicationsSummary

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.Chemical vapour deposition. 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 Cost effectiveness.System integration. High Precision.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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