project report on MEMS(Micro electromechanical systems)

7/27/2019 project report on MEMS(Micro electromechanical systems)

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1. INTRODUCTION

Micro electromechanical systems (MEMS) are small integrated devices or systems that

combine electrical and mechanical components. They range in size from the sub

micrometer level to the millimeter level and there can be any number, from a few to

millions, in a particular system. MEMS extend the fabrication techniques developed for

the integrated circuit industry to add mechanical elements such as beams, gears,

diaphragms, and springs to devices.

Examples of MEMS device applications include inkjet-printer cartridges, accelerometer,

miniature robots, microengines, locks inertial sensors microtransmissions, micromirrors,

micro actuator (Mechanisms for activating process control equipment by use of

pneumatic, hydraulic, or electronic signals) optical scanners, fluid pumps, and transducer,

pressure and flow sensors. New applications are emerging as the existing technology is

applied to the miniaturization and integration of conventional devices.

These systems can sense, control, and activate mechanical processes on the micro scale,

and function individually or in arrays to generate effects on the macro scale. The micro

fabrication technology enables fabrication of large arrays of devices, which individually

perform simple tasks, but in combination can accomplish complicated functions.

MEMS are not about any one application or device, nor are they defined by a single

fabrication process or limited to a few materials. They are a fabrication approach that

conveys the advantages of miniaturization, multiple components, and microelectronics to

the design and construction of integrated electromechanical systems. MEMS are not only

about miniaturization of mechanical systems; they are also a new paradigm for designing

mechanical devices and systems.

The MEMS industry has an estimated $10 billion market, and with a projected 10-20%

annual growth rate, it is estimated to have a $34 billion market in 2002. Because of the

significant impact that MEMS can have on the commercial and defense markets, industry

and the federal government have both taken a special interest in their development.


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2. WHATIS MEMS TECHNOLOGY?

Micro-Electro-Mechanical Systems (MEMS) is the integration of mechanical elements,

sensors, actuators, and electronics on a common silicon substrate through microfabrication

technology. While the electronics are fabricated using integrated circuit (IC) process

sequences, the micromechanical components are fabricated using compatible

"micromachining" processes that selectively etch away parts of the silicon wafer or add

new structural layers to form the mechanical and electromechanical devices.

Microelectronic integrated circuits can be thought of as the "brains" of a system and

MEMS augments this decision-making capability with "eyes" and "arms", to allow

microsystems to sense and control the environment. Sensors gather information from the

environment through measuring mechanical, thermal, biological, chemical, optical, and

magnetic phenomena. The electronics then process the information derived from the

sensors and through some decision making capability direct the actuators to respond by

moving, positioning, regulating, pumping, and filtering, thereby controlling the

environment for some desired outcome or purpose. Because MEMS devices are

manufactured using batch fabrication techniques similar to those used for integrated

circuits, unprecedented levels of functionality, reliability, and sophistication can be placed

on a small silicon chip at a relatively low cost.


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3. WHATARE MEMS / MICROSYSTEMS?

MEMS is an abbreviation for Micro Electro Mechanical Systems. This is a rapidly

emerging technology combining electrical, electronic, mechanical, optical, material,

chemical, and fluids engineering disciplines. As the smallest commercially produced

"machines", MEMS devices are similar to traditional sensors and actuators although much,

much smaller. E.g. Complete systems are typically a few millimeters across, with

individual features devices of the order of 1-100 micrometers across.

MEMS devices are manufactured either using processes based on Integrated Circuit

fabrication techniques and materials, or using new emerging fabrication technologies such

as micro injection molding. These former processes involve building the device up layer

by layer, involving several material depositions and etch steps. A typical MEMSfabrication technology may have a 5 step process. Due to the limitations of this

"traditional IC" manufacturing process MEMS devices are substantially planar, having

very low aspect ratios (typically 5 -10 micro meters thick). It is important to note that there

are several evolving fabrication techniques that allow higher aspect ratios such as deep x-

ray lithography, electrodeposition, and micro injection molding.

MEMS devices are typically fabricated onto a substrate (chip) that may also contain the

electronics required to interact with the MEMS device. Due to the small size and mass of


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the devices, MEMS components can be actuated electrostatically (piezoelectric and

bimetallic effects can also be used). The position of MEMS components can also be

sensed capacitively. Hence the MEMS electronics include electrostatic drive power

supplies, capacitance charge comparators, and signal conditioning circuitry. Connection

with the macroscopic world is via wire bonding and encapsulation into familiar BGA,

MCM, surface mount, or leaded IC packages.

A common MEMS actuator is the "linear comb drive" (shown above) which consists of

rows of interlocking teeth; half of the teeth are attached to a fixed "beam", the other half

attach to a movable beam assembly. Both assemblies are electrically insulated. By

applying the same polarity voltage to both parts the resultant electrostatic force repels themovable beam away from the fixed. Conversely, by applying opposite polarity the parts

are attracted. In this manner the comb drive can be moved "in" or "out" and either DC or

AC voltages can be applied. The small size of the parts (low inertial mass) means that the

drive has a very fast response time compared to its macroscopic counterpart. The

magnitude of electrostatic force is multiplied by the voltage or more commonly the surface

area and number of teeth. Commercial comb drives have several thousand teeth, each

tooth approximately 10 micro meters long. Drive voltages are CMOS levels.

The linear push / pull motion of a comb drive can be converted into rotational motion by

coupling the drive to push rod and pinion on a wheel. In this manner the comb drive can

rotate the wheel in the same way a steam engine functions!


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4. MEMS DESCRIPTION

MEMS technology can be implemented using a number of different materials and

manufacturing techniques; the choice of which will depend on the device being created

and the market sector in which it has to operate.

SILICON

The economies of scale, ready availability of cheap high-quality materials and ability to

incorporate electronic functionality make silicon attractive for a wide variety of MEMS

applications. Silicon also has significant advantages engendered through its material

properties. In single crystal form, silicon is an almost perfect Hookean material, meaning

that when it is flexed there is virtually no hysteresis and hence almost no energy

dissipation. The basic techniques for producing all silicon based MEMS devices are

deposition of material layers, patterning of these layers by photolithography and then

etching to produce the required shapes.

POLYMERS

Even though the electronics industry provides an economy of scale for the silicon industry,

crystalline silicon is still a complex and relatively expensive material to produce. Polymers

on the other hand can be produced in huge volumes, with a great variety of material

characteristics. MEMS devices can be made from polymers by processes such as injection

moulding, embossing or stereolithography and are especially well suited to microfluidic

applications such as disposable blood testing cartridges.

METALS

Metals can also be used to create MEMS elements. While metals do not have some of the

advantages displayed by silicon in terms of mechanical properties, when used within their

limitations, metals can exhibit very high degrees of reliability. Metals can be deposited by

electroplating, evaporation, and sputtering processes. Commonly used metals include gold,

nickel, aluminum, chromium, titanium, tungsten, platinum, and silver


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5. MEMS DESIGN PROCESS

There are three basic building blocks in MEMS technology, which are, Deposition

Process-the ability to deposit thin films of material on a substrate, Lithography-to apply a

patterned mask on top of the films by photolithograpic imaging, and Etching-to etch the

films selectively to the mask. A MEMS process is usually a structured sequence of these

operations to form actual devices.

5.1 Lithography

Lithography in the MEMS 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. If we selectively expose a photosensitive material to radiation (e.g. by

masking some of the radiation) the pattern of the radiation on the material is transferred to

the material exposed, as the properties of the exposed and unexposed regions differs (as

shown in figure 1).

Figure 1:Transfer of a pattern to a photosensitive material.


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This discussion will focus on optical lithography, which is simply lithography using a

radiation source with wavelength(s) in the visible spectrum.

In lithography for micromachining, the photosensitive material used is typically a

photoresist (also called resist, other photosensitive polymers are also used). When resist is

exposed to a radiation source of a specific a wavelength, the chemical resistance of the

resist to developer solution changes. If the resist is placed in a developer solution after

selective exposure to a light source, it will etch away one of the two regions (exposed or

unexposed). If the exposed material is etched away by the developer and the unexposed

region is resilient, the material is considered to be a positive resist (shown in figure 2a). If

the exposed material is resilient to the developer and the unexposed region is etched away,

it is considered to be a negative resist (shown in figure 2b).

Figure 2: a)Pattern definition in positive resist, b)Pattern definition in negative resist.

Lithography is the principal mechanism for pattern definition in micromachining.

Photosensitive compounds are primarily organic, and do not encompass the spectrum of

materials properties of interest to micro-machinists. However, as the technique is capable


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of producing fine features in an economic fashion, a photosensitive layer is often used as a

temporary mask when etching an underlying layer, so that the pattern may be transferred

to the underlying layer (shown in figure 3a). Photoresist may also be used as a template for

patterning material deposited after lithography (shown in figure 3b). The resist is

subsequently etched away, and the material deposited on the resist is "lifted off".

The deposition template (lift-off) approach for transferring a pattern from resist to another

layer is less common than using the resist pattern as an etch mask. The reason for this is

that resist is incompatible with most MEMS deposition processes, usually because it

cannot withstand high temperatures and may act as a source of contamination.

Figure 3: a)Pattern transfer from patterned photoresist to underlying layer by etching, b)Pattern transfer from patterned photoresist to overlying layer by lift-off.

Once the pattern has been transferred to another layer, the resist is usually stripped. This is

often necessary as the resist may be incompatible with further micromachining steps. It

also makes the topography more dramatic, which may hamper further lithography steps.

ALIGNMENT

In order to make useful devices the patterns for different lithography steps that belong to a

single structure must be aligned to one another. The first pattern transferred to a wafer

usually includes a set of alignment marks, which are high precision features that are used

as the reference when positioning subsequent patterns, to the first pattern (as shown in


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figure 4). Often alignment marks are included in other patterns, as the original alignment

marks may be obliterated as processing progresses. It is important for each alignment

mark on the wafer to be labeled so it may be identified, and for each pattern to specify the

alignment mark to which it should be aligned.

Figure 4:Use of alignment marks to register subsequent layers

Depending on the lithography equipment used, the feature on the mask used for

registration of the mask may be transferred to the wafer. In this case, it may be important

to locate the alignment marks such that they don't effect subsequent wafer processing or

device performance. For example, the alignment mark shown in figure 6 will cease to exist

after a through the wafer DRIE etch. Pattern transfer of the mask alignment features to the

wafer may obliterate the alignment features on the wafer. In this case the alignment marks

should be designed to minimize this effect, or alternately there should be multiple copies

of the alignment marks on the wafer, so there will be alignment marks remaining for other

masks to be registered to.


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Figure 5:Transfer of mask registration feature to substrate during lithography (contactaligner)

Figure 6:Poor alignment mark design for a DRIE through the wafer etches (cross hair isreleased and lost).

Alignment marks may not necessarily be arbitrarily located on the wafer, as the equipment

used to perform alignment may have limited travel and therefore only be able to align to

features located within a certain region on the wafer (as shown in figure 7). The region

location geometry and size may also vary with the type of alignment, so the lithographicequipment and type of alignment to be used should be considered before locating


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alignment marks. Typically two alignment marks are used to align the mask and wafer,

one alignment mark is sufficient to align the mask and wafer in x and y, but it requires two

marks (preferably spaced far apart) to correct for fine offset in rotation.

As there is no pattern on the wafer for the first pattern to align to, the first pattern is

typically aligned to the primary wafer flat (as shown in figure 8). Depending on the

lithography equipment used, this may be done automatically, or by manual alignment to an

explicit wafer registration feature on the mask

Figure 7:Restriction of location of alignment marks based on equipment used.

.


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Figure 8:Mask alignment to the wafer flat.

EXPOSURE

The exposure parameters required in order to achieve accurate pattern transfer from the

mask to the photosensitive layer depend primarily on the wavelength of the radiation

source and the dose required to achieve the desired properties change of the photoresist.

Different photoresists exhibit different sensitivities to different wavelengths. The dose

required per unit volume of photoresist for good pattern transfer is somewhat constant;

however, the physics of the exposure process may affect the dose actually received. For

example a highly reflective layer under the photoresist may result in the material

experiencing a higher dose than if the underlying layer is absorptive, as the photoresist is

exposed both by the incident radiation as well as the reflected radiation. The dose will also

vary with resist thickness.

There are also higher order effects, such as interference patterns in thick resist films on

reflective substrates, which may affect the pattern transfer quality and sidewall properties.

At the edges of pattern light is scattered and diffracted, so if an image is overexposed, the

dose received by photoresist at the edge that shouldn't be exposed may become significant.

If we are using positive photoresist, this will result in the photoresist image being eroded

along the edges, resulting in a decrease in feature size and a loss of sharpness or corners

(as shown in figure 9). If we are using a negative resist, the photoresist image is dilated,


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causing the features to be larger than desired, again accompanied by a loss of sharpness of

corners. If an image is severely underexposed, the pattern may not be transferred at all,

and in less sever cases the results will be similar to those for overexposure with the results

reversed for the different polarities of resist.

If the surface being exposed is not flat, the high-resolution image of the mask on the wafer

may be distorted by the loss of focus of the image across the varying topography. This is

one of the limiting factors of MEMS lithography when high aspect ratio features are

present. High aspect ratio features also experience problems with obtaining even resist

thickness coating, which further degrades pattern transfer and complicates the associated

processing.

Figure 9:Over and under-exposure of positive resist.

5.2 ETCHING PROCESSES

In order to form a functional MEMS structure on a substrate, it is necessary to etch the

thin films previously deposited and/or the substrate itself. In general, there are two classes

of etching processes:


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1. Wet etching where the material is dissolved when immersed in a chemical solution

2. Dry etching where the material is sputtered or dissolved using reactive ions or a

vapor phase etchant

WETETCHING

This is the simplest etching technology. All it requires is a container with a liquid solution

that will dissolve the material in question. Unfortunately, there are complications since

usually a mask is desired to selectively etch the material. One must find a mask that will

not dissolve or at least etches much slower than the material to be patterned. Secondly,

some single crystal materials, such as silicon, exhibit anisotropic etching in certain

chemicals. Anisotropic etching in contrast to isotropic etching means different etches rates

in different directions in the material. The classic example of this is the crystal

plane sidewalls that appear when etching a hole in a silicon wafer in a chemical

such as potassium hydroxide (KOH). The result is a pyramid shaped hole instead of a hole

with rounded sidewalls with a isotropic etchant. The principle of anisotropic and isotropic

wet etching is illustrated in the figure below.

WHENDOWEWANTTOUSEWETETCHING?

This is a simple technology, which will give good results if you can find the combination

of etchant and mask material to suit your application. Wet etching works very well for

etching thin films on substrates, and can also be used to etch the substrate itself. The

problem with substrate etching is that isotropic processes will cause undercutting of the

mask layer by the same distance as the etch depth. Anisotropic processes allow the etching

to stop on certain crystal planes in the substrate, but still results in a loss of space, since

these planes cannot be vertical to the surface when etching holes or cavities. If this is a

limitation for you, you should consider dry etching of the substrate instead. However, keep

in mind that the cost per wafer will be 1-2 orders of magnitude higher to perform the dry

etching

If you are making very small features in thin films (comparable to the film thickness), you

may also encounter problems with isotropic wet etching, since the undercutting will be at

least equal to the film thickness. With dry etching it is possible etch almost straight down

without undercutting, which provides much higher resolution.


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Figure 1:Difference between anisotropic and isotropic wet etching.

DRYETCHING

The dry etching technology can split in three separate classes called reactive ion etching

(RIE), sputter etching, and vapor phase etching.

In RIE, the substrate is placed inside a reactor in which several gases are introduced.

Plasma is struck in the gas mixture using an RF power source, breaking the gas molecules

into ions. The ion is accelerated towards, and reacts at, the surface of the material being

etched, forming another gaseous material. This is known as the chemical part of reactive

ion etching. There is also a physical part which is similar in nature to the sputtering

deposition process. If the ions have high enough energy, they can knock atoms out of the

material to be etched without a chemical reaction. It is very complex tasks to develop dry

etch processes that balance chemical and physical etching, since there are many

parameters to adjust. By changing the balance it is possible to influence the anisotropy of

the etching, since the chemical part is isotropic and the physical part highly anisotropic the

combination can form sidewalls that have shapes from rounded to vertical. A schematic of

a typical reactive ion etching system is shown in the figure below.

A special subclass of RIE which continues to grow rapidly in popularity is deep RIE

(DRIE). In this process, etch depths of hundreds of microns can be achieved with almost

vertical sidewalls. The primary technology is based on the so-called "Bosch process",

named after the German company Robert Bosch which filed the original patent, where two

different gas compositions are alternated in the reactor. The first gas composition creates a

polymer on the surface of the substrate, and the second gas composition etches the

substrate. The polymer is immediately sputtered away by the physical part of the etching,

but only on the horizontal surfaces and not the sidewalls. Since the polymer only dissolves

very slowly in the chemical part of the etching, it builds up on the sidewalls and protects

them from etching. As a result, etching aspect ratios of 50 to 1 can be achieved. The


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process can easily be used to etch completely through a silicon substrate, and etch rates are

3-4 times higher than wet etching. Sputter etching is essentially RIE without reactive ions.

The systems used are very similar in principle to sputtering deposition systems. The big

difference is that substrate is now subjected to the ion bombardment instead of the

material target used in sputter deposition.

Vapor phase etching is another dry etching method, which can be done with simpler

equipment than what RIE requires. In this process the wafer to be etched is placed inside a

chamber, in which one or more gases are introduced. The material to be etched is

dissolved at the surface in a chemical reaction with the gas molecules. The two most

common vapor phase etching technologies are silicon dioxide etching using hydrogen

fluoride (HF) and silicon etching using xenon diflouride (XeF2), both of which are

isotropic in nature. Usually, care must be taken in the design of a vapor phase process to

not have bi-products form in the chemical reaction that condense on the surface and

interfere with the etching process.

WHENDOWEWANTTOUSEDRYETCHING?

The first thing you should note about this technology is that it is expensive to run

compared to wet etching. If you are concerned with feature resolution in thin film

structures or you need vertical sidewalls for deep etchings in the substrate, you have to

consider dry etching. If you are concerned about the price of your process and device, you

may want to minimize the use of dry etching. The IC industry has long since adopted dry

etching to achieve small features, but in many cases feature size is not as critical in

MEMS. Dry etching is an enabling technology, which comes at a sometimes high cost.

Figure 2:Typical parallel-plate reactive ion etching system.


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6. Current Challenges

MEMS and Nanotechnology is currently used in low- or medium-volume applications.

Some of the obstacles preventing its wider adoption are:

LIMITED OPTIONS

Most companies who wish to explore the potential of MEMS and Nanotechnology have

very limited options for prototyping or manufacturing devices, and have no capability or

expertise in microfabrication technology. Few companies will build their own fabrication

facilities because of the high cost. A mechanism giving smaller organizations responsive

and affordable access to MEMS and Nano fabrication is essential.

PACKAGING

The packaging of MEMS devices and systems needs to improve considerably from its

current primitive state. MEMS packaging is more challenging than IC packaging due to

the diversity of MEMS devices and the requirement that many of these devices be in

contact with their environment. Currently almost all MEMS and Nano development efforts

must develop a new and specialized package for each new device. Most companies findthat packaging is the single most expensive and time consuming task in their overall

product development program. As for the components themselves, numerical modeling

and simulation tools for MEMS packaging are virtually non-existent. Approaches which

allow designers to select from a catalog of existing standardized packages for a new

MEMS device without compromising performance would be beneficial.

FABRICATION KNOWLEDGE REQUIRED

Currently the designer of a MEMS device requires a high level of fabrication knowledge

in order to create a successful design. Often the development of even the most mundane

MEMS device requires a dedicated research effort to find a suitable process sequence for

fabricating it. MEMS device design needs to be separated from the complexities of the

process sequence.


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7. APPLICATIONS

PRESSURE SENSORS

MEMS pressure microsensors typically have a flexible diaphragm that deforms in the

presence of a pressure difference. The deformation is converted to an electrical signal

appearing at the sensor output. A pressure sensor can be used to sense the absolute air

pressure within the intake manifold of an automobile engine, so that the amount of fuel

required for each engine cylinder can be computed.

ACCELEROMETERS

Accelerometers are acceleration sensors. An inertial mass suspended by springs is acted

upon by acceleration forces that cause the mass to be deflected from its initial position.

This deflection is converted to an electrical signal, which appears at the sensor output. The

application of MEMS technology to accelerometers is a relatively new development.

Accelerometers in consumer electronics devices such as game controllers (Nintendo Wii),

personal media players / cell phones (Apple iPhone ) and a number of Digital Cameras

(various Canon Digital IXUS models). Also used in PCs to park the hard disk head whenfree-fall is detected, to prevent damage and data loss. iPod Touch: When the technology

become sensitive. MEMS-based sensors are ideal for a wide array of applications in

consumer, communication, automotive and industrial markets.
http://en.wikipedia.org/wiki/IPhonehttp://en.wikipedia.org/wiki/IPhone


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The consumer market has been a key driver for MEMS technology success. For example,

in a mobile phone, MP3/MP4 player or PDA, these sensors offer a new intuitive motion-

based approach to navigation within and between pages. In game controllers, MEMS

sensors allow the player to play just moving the controller/pad; the sensor determines the

motion.

INERTIAL SENSORS

Inertial sensors are a type of

accelerometer and are one of the

principal commercial products that

utilize surface micromachining. They

are used as airbag-deployment sensors

in automobiles, and as tilt or shock

sensors. The application of these

accelerometers to inertial measurement

units is limited by the need to manually

align and assemble them into three-

axis systems, and by the resulting

alignment tolerances, their lack of in-

chip analog-to-digital conversion

circuitry, and their lower limit of

sensitivity

.

MICROENGINES

A three-level polysilicon micromachining process has enabled the fabrication of

devices with increased degrees of complexity. The process includes three movable

levels of polysilicon, each separated by a sacrificial oxide layer, plus a stationary

level. Microengines can be used to drive the wheels of microcombination locks. They

can also be used in combination with a microtransmission to drive a pop-up mirror out

of a plane. This device is known as a micromirror.


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SOME OTHERCOMMERCIALAPPLICATIONSINCLUDE:

Inkjet printers, which usepiezoelectrics or thermal bubble ejection to deposit

ink on paper.

Accelerometers in modern cars for a large number of purposes including

airbag deployment in collisions.

MEMS gyroscopes used in modern cars and other applications to detect yaw;

e.g. to deploy a roll over bar or trigger dynamic stability control. Silicon pressure sensors e.g. car tire pressure sensors, and disposable blood

pressure sensors.

Displays e.g. the DMD chip in a projector based on DLP technology has on its

surface several hundred thousand micromirrors.

Optical switching technology which is used for switching technology and

alignment for data communications.

Bio-MEMS applications in medical and health related technologies from Lab-

On-Chip to MicroTotalAnalysis (biosensor, chemosensor).
http://en.wikipedia.org/wiki/Inkjethttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Accelerometerhttp://en.wikipedia.org/wiki/Airbaghttp://en.wikipedia.org/wiki/DLPhttp://en.wikipedia.org/wiki/Optical_switchinghttp://en.wikipedia.org/wiki/Inkjethttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Accelerometerhttp://en.wikipedia.org/wiki/Airbaghttp://en.wikipedia.org/wiki/DLPhttp://en.wikipedia.org/wiki/Optical_switching


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Interferometric modulator display (IMOD) applications in consumer electronics. Used

to create interferometric modulation - reflective display technology as found in

mirasol displays.

MEMS IC fabrication technologies have also allowed the manufacture of advanced

memory devices (nanochips/microchips).


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As a final example, MEMS technology has been used in fabricating vaporization

microchambers for vaporizing liquid microthrusters for nanosatellites. The chamber is

part of a microchannel with a height of 2-10 microns, made using silicon and glass

substrates

ADVANTAGES OF MEMS DISADVANTAGES OF MEMS

Minimize energy and materials

use in manufacturing

Cost/performance advantages

Improved reproducibility

Improved accuracy and

reliability

Increased selectivity and

sensitivity

Farm establishment requires

huge investments

Micro-components are Costly

compare to macro-components

Design includes very much

complex procedures

Prior knowledge is needed to

integrate MEMS devices


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8. THE FUTURE

Each of the three basic microsystems technology processes we have seen, bulk

micromachining, sacrificial surface micromachining, and micromolding/LIGA, employs

a different set of capital and intellectual resources. MEMS manufacturing firms must

choose which specific microsystems manufacturing techniques to invest in.

MEMS technology has the potential to change our daily lives as much as the computer

has. However, the material needs of the MEMS field are at a preliminary stage. A

thorough understanding of the properties of existing MEMS materials is just as important

as the development of new MEMS materials.

Future MEMS applications will be driven by processes enabling greater functionality

through higher levels of electronic-mechanical integration and greater numbers of

mechanical components working alone or together to enable a complex action. Future

MEMS products will demand higher levels of electrical-mechanical integration and more

intimate interaction with the physical world. The high up-front investment costs for large-

volume commercialization of MEMS will likely limit the initial involvement to larger

companies in the IC industry. Advancing from their success as sensors, MEMS productswill be embedded in larger non-MEMS systems, such as printers, automobiles, and

biomedical diagnostic equipment, and will enable new and improved systems.

HOWTHE MEMS AND NANO EXCHANGE CAN HELP?

The MEMS and Nanotechnology Exchange provides services that can help with some of

these problems.

We make a diverse catalog of processing capabilities available to our users, so our

users can experiment with different fabrication technologies. Our users don't have

to build their own fabrication facilities, and


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Our web-based interface lets users assemble process sequences and submit them

for review by the MEMS and Nanotechnology Exchange's engineers and

fabrication sites.

9. CONCLUSION

The automotive industry, motivated by the need for more efficient safety systems and the

desire for enhanced performance, is the largest consumer of MEMS-based technology. In

addition to accelerometers and gyroscopes, micro-sized tire pressure systems are now

standard issues in new vehicles, putting MEMS pressure sensors in high demand. Such

micro-sized pressure sensors can be used by physicians and surgeons in a telemetry

system to measure blood pressure at a stet, allowing early detection of hypertension andrestenosis. Alternatively, the detection of bio molecules can benefit most from MEMS-

based biosensors. Medical applications include the detection of DNA sequences and

metabolites. MEMS biosensors can also monitor several chemicals simultaneously,

making them perfect for detecting toxins in the environment.

Lastly, the dynamic range of MEMS based silicon ultrasonic sensors have many

advantages over existing piezoelectric sensors in non-destructive evaluation, proximity

sensing and gas flow measurement. Silicon ultrasonic sensors are also very effective

immersion sensors and provide improved performance in the areas of medical imaging

and liquid level detection.

The medical, wireless technology, biotechnology, computer, automotive and

aerospace industries are only a few that will benefit greatly from MEMS.

This enabling technology allowing the development of smart products,

augmenting the computational ability of microelectronics with the perception and

control capabilities of microsensors and microactuators and expanding the space

of possible designs and applications.

MEMS devices are manufactured for unprecedented levels of functionality,

reliability, and sophistication can be placed on a small silicon chip at a relatively

low cost.


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MEMS promises to revolutionize nearly every product category by bringing

together silicon-based microelectronics with micromachining technology, making

possible the realization of complete systems-on-a-chip.

MEMS will be the indispensable factor for advancing technology in the 21st

century and it promises to create entirely new categories of products.

10. REFERENCES

Online Resources

BSAC http://www-bsac.eecs.berkeley.edu/

DARPA MTO http://www.darpa.mil/mto/

IEEE Explore http://ieeexpl ore.ieee.org/Xplore/DynWel.jsp

Introduction to Microengineering http://www.dbanks.demon.co.uk/ueng/ MEMS Clearinghouse http://www.memsnet.org/

MEMS Exchange http://www.mems-exchange.org/

MEMS Industry Group http://www.memsindustrygroup.org/

MOSIS http://www.mosis.org/

MUMPS http://www.memscap.com/memsrus/crmumps.html

Stanford Centre for Integrated Systems http://www-cis.stanford.edu/

USPTO http://www.uspto.gov/

Trimmerhttp://www.trimmer.net/

Yole Development http://www.yole.fr/pagesAn/accueil.asp

Journals

Journal of Micromechanical Systems

Journal of Micromechanics and Microengineering

Micromachine Devices

Sensors Magazine
http://www.trimmer.net/http://www.trimmer.net/

project report on MEMS(Micro electromechanical systems)

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Transcript of project report on MEMS(Micro electromechanical systems)