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Transcript of 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.
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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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7/27/2019 project report on MEMS(Micro electromechanical systems)
25/25
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/