i

Contents:

Abstract .......................................................................................................................... ii Abbreviations ............................................................................................................... iii Introduction .................................................................................................................... 1

What is MEMS Technology? ..................................................................................... 1 What are MEMS / Microsystems? ............................................................................. 2 MEMS DESCRIPTION .................................................................................................. 3

SILICON ................................................................................................................... 3 POLYMERS .............................................................................................................. 3

METALS .................................................................................................................. 4 MEMS Design Process .................................................................................................. 4

Deposition Processes ................................................................................................. 4

Chemical Vapor Deposition (CVD)....................................................................... 5 Electrodeposition ................................................................................................... 6 Epitaxy ................................................................................................................... 6 Thermal oxidation .................................................................................................. 7

Physical Vapor Deposition (PVD) ......................................................................... 8 Casting ................................................................................................................... 8

Lithography .................................................................................................................... 8 Pattern Transfer .......................................................................................................... 8

Alignment .................................................................................................................. 9 Exposure .................................................................................................................... 9

Etching Processes......................................................................................................... 10

Wet etching .............................................................................................................. 10

Dry etching............................................................................................................... 11 Fabrication Technologies ............................................................................................. 11

IC Fabrication .......................................................................................................... 12

Bulk Micromachining and Wafer Bonding .............................................................. 13 Surface Micromachining .......................................................................................... 14

Micro molding ......................................................................................................... 14 Current Challenges....................................................................................................... 14 Applications ................................................................................................................. 15

Conclusion ................................................................................................................... 23 References .................................................................................................................... 24

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Abstract

Sensors have been used as detection elements for past decades. One

simple and common example is the mercury thermometer used to measure the body

temperature that relies on the Physical property called thermal expansion. In general,

a sensor needs a transducer that transforms the measured magnitude in another one

that is easier to interpret or visualize. Actuators on the other hand are the elements

that perform an action when triggered by a signal.

Microelectromechanical 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, transducer, pressure and flow sensors. New applications are

emerging as the existing technology is applied to the miniaturization and integration

of conventional devices.

iii

Abbreviations

CVD: Chemical Vapour Deposition

DLC: Diamond like carbon

DLP: Digital Light Processing

DMD: Digital micromirror device

DNA: Deoxyribonucleic acid

HMDS: Hexamethyldisilazane

IC: Integrated Circuit

IMOD: Interferometric modulator display

LIGA: Lithographie, Galvanoformung, und Abformung

LPCVD: Low Pressure Chemical Vapour Deposition

MEMS:Micro Electro Mechanical Systems

PECVD: Plasma Enhanced Vapour Deposition

PVD: Physical Vapour Deposition

RIE: Reactive Ion Etching

SOI: Silicon on Insulator

VPE: Vapor Phase Epitaxy

1

Introduction

MEMS 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 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.

What is 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.

Micromotor gear

2

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.

What are MEMS / Microsystems?

MEMS is an abbreviation for Micro Electro Mechanical Systems. This

rapidly emerging technology combines 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.

Torsional actuator

3

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 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.

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. 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.

4

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

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.

Deposition Processes

One of the basic building blocks in MEMS processing is the ability to

deposit thin films of material. We assume a thin film to have a thickness anywhere

between a few nanometers to about 100 micrometer

MEMS deposition technology can be classified in two groups:

1. Depositions that happen because of a chemical reaction:

o Chemical Vapor Deposition (CVD)

o Electrodeposition

o Epitaxy

o Thermal oxidation

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These processes exploit the creation of solid materials directly from chemical

reactions in gas and/or liquid compositions or with the substrate material. The

solid material is usually not the only product formed by the reaction.

Byproducts can include gases, liquids and even other solids.

2. Depositions that happen because of a physical reaction:

o Physical Vapor Deposition (PVD)

o Casting

Common for all these processes are that the material deposited is physically

moved on to the substrate. In other words, there is no chemical reaction which

forms the material on the substrate. This is not completely correct for casting

processes, though it is more convenient to think of them that way.

Chemical Vapor Deposition (CVD)

In this process, the substrate is placed inside a reactor to which a number

of gases are supplied. The fundamental principle of the process is that a chemical

reaction takes place between the source gases.

The two most important CVD technologies in MEMS are the Low

Pressure CVD (LPCVD) and Plasma Enhanced CVD (PECVD). The LPCVD process

produces layers with excellent uniformity of thickness and material characteristics.

The main problems with the process are the high deposition temperature (higher than

600°C) and the relatively slow deposition rate. The PECVD process can operate at

lower temperatures (down to 300° C) thanks to the extra energy supplied to the gas

molecules by the plasma in the reactor. However, the quality of the films tends to be

inferior to processes running at higher temperatures. Secondly, most PECVD

deposition systems can only deposit the material on one side of the wafers on 1 to 4

wafers at a time. LPCVD systems deposit films on both sides of at least 25 wafers at a

time.

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Electrodeposition

This process is also known as "electroplating" and is typically restricted

to electrically conductive materials. The electrodeposition process is well suited to

make films of metals such as copper, gold and nickel. There are basically two

technologies for plating: Electroplating and Electroless plating. In the electroplating

process the substrate is placed in a liquid solution (electrolyte). When an electrical

potential is applied between a conducting area on the substrate and a counter electrode

(usually platinum) in the liquid, a chemical redox process takes place resulting in the

formation of a layer of material on the substrate and usually some gas generation at

the counter electrode. A schematic diagram of a typical setup for electroplating is

shown in the figure below.

Epitaxy

This technology is quite similar to what happens in CVD processes,

however, if the substrate is an ordered semiconductor crystal (i.e. silicon, gallium

arsenide); it is possible with this process to continue building on the substrate with the

same crystallographic orientation with the substrate acting as a seed for the

deposition.

There are several technologies for creating the conditions inside a

reactor needed to support epitaxial growth, of which the most important is Vapor

Phase Epitaxy (VPE). In this process, a number of gases are introduced in an

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induction heated reactor where only the substrate is heated. The temperature of the

substrate typically must be at least 50% of the melting point of the material to be

deposited. Epitaxy is a widely used technology for producing silicon on insulator

(SOI) substrates. A schematic diagram of a typical vapor phase epitaxial reactor is

shown in the figure below.

Typical cold-wall vapor phase epitaxial reactor.

Thermal oxidation

This is one of the most basic deposition technologies. It is simply

oxidation of the substrate surface in an oxygen rich atmosphere. The temperature is

raised to 800°C - 1100°C to speed up the process. This is also the only deposition

technology which actually consumes some of the substrate as it proceeds. The growth

of the film is spurned by diffusion of oxygen into the substrate, which means the film

growth is actually downwards into the substrate. This process is naturally limited to

materials that can be oxidized, and it can only form films that are oxides of that

material. This is the classical process used to form silicon dioxide on a silicon

substrate. A schematic diagram of a typical wafer oxidation furnace is shown in the

figure below.

Typical wafer oxidation furnace

8

Physical Vapor Deposition (PVD)

PVD covers a number of deposition technologies in which material is

released from a source and transferred to the substrate.PVD is far more common than

CVD for metals since it can be performed at lower process risk and cheaper in regards

to materials cost. However PVD’s quality of film is inferior to CVD. The two most

important technologies are evaporation and sputtering.

Casting

In this process the material to be deposited is dissolved in liquid form in

a solvent. The material can be applied to the substrate by spraying or spinning. Once

the solvent is evaporated, a thin film of the material remains on the substrate. This is

particularly useful for polymer materials, which may be easily dissolved in organic

solvents, and it is the common method used to apply photoresist to substrates (in

photolithography). In recent years, the casting technology has also been applied to

form films of glass materials on substrates.

Lithography

Pattern Transfer

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 (shown below).

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Transfer of a pattern to a photosensitive material

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.

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.

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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:

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

Wet etching

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 principle of anisotropic and isotropic wet etching is illustrated in the figure

below.

Difference between anisotropic and isotropic wet etching.

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Dry etching

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. Vapour 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. Dry etching is an expensive technology compared to wet etching, though it

has a higher resolution than the later.

Fabrication Technologies

The three characteristic features of MEMS fabrication technologies are

miniaturization, multiplicity, and microelectronics. Miniaturization enables the

production of compact, quick-response devices. Multiplicity refers to the batch

fabrication inherent in semiconductor processing, which allows thousands or millions

of components to be easily and concurrently fabricated. Microelectronics provides the

intelligence to MEMS and allows the monolithic merger of sensors, actuators, and

logic to build closed-loop feedback components and systems. The successful

miniaturization and multiplicity of traditional electronics systems would not have

12

been possible without IC fabrication technology. Therefore, IC fabrication

technology, or microfabrication, has so far been the primary enabling technology for

the development of MEMS. Microfabrication provides a powerful tool for batch

processing and miniaturization of mechanical systems into a dimensional domain not

accessible by conventional techniques. Furthermore, microfabrication provides an

opportunity for integration of mechanical systems with electronics to develop high-

performance closed-loop-controlled MEMS.

IC Fabrication

Any discussion of MEMS requires a basic understanding of IC

fabrication technology, or microfabrication, the primary enabling technology for the

development of MEMS. The major steps in IC fabrication technology are:

Film growth: Usually, a polished Si wafer is used as the substrate, on which a

thin film is grown. The film, which may be epitaxial Si, SiO2, silicon nitride

(Si3N4), polycrystalline Si, or metal, is used to build both active or passive

components and interconnections between circuits.

Doping: To modulate the properties of the device layer, a low and controllable

level of an atomic impurity may be introduced into the layer by thermal

diffusion or ion implantation.

Lithography: A pattern on a mask is then transferred to the film by means of a

photosensitive (i.e., light sensitive) chemical known as a photoresist. The

process of pattern generation and transfer is called photolithography. A typical

mask consists of a glass plate coated with a patterned chromium (Cr) film.

Etching: Next is the selective removal of unwanted regions of a film or

substrate for pattern delineation. Wet chemical etching or dry etching may be

used. Etch-mask materials are used at various stages in the removal process to

selectively prevent those portions of the material from being etched. These

materials include SiO2, Si3N4, and hard-baked photoresist.

Dicing: The finished wafer is sawed or machined into small squares, or dice,

from which electronic components can be made.

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Packaging: The individual sections are then packaged, a process that involves

physically locating, connecting, and protecting a device or component. MEMS

design is strongly coupled to the packaging requirements, which in turn are

dictated by the application environment.

Bulk Micromachining and Wafer Bonding

Bulk micromachining is an extension of IC technology for the

fabrication of 3D structures. Bulk micromachining of Si uses wet- and dry-etching

techniques in conjunction with etch masks and etch stops to sculpt micromechanical

devices from the Si substrate. The two key capabilities that make bulk

micromachining a viable technology are:

Anisotropic etchants of Si, such as ethylene-diamine and pyrocatechol (EDP),

potassium hydroxide (KOH), and hydrazine (N2H4). These preferentially etch

single crystal Si along given crystal planes.

Etch masks and etch-stop techniques that can be used with Si anisotropic

etchants to selectively prevent regions of Si from being etched. Good etch

masks are provided by SiO2 and Si3N4, and some metallic thin films such as

Cr and Au (gold).

14

Surface Micromachining

Surface micromachining enables the fabrication of complex

multicomponent integrated micromechanical structures that would not be possible

with traditional bulk micromachining. This technique encases specific structural parts

of a device in layers of a sacrificial material during the fabrication process. The

substrate wafer is used primarily as a mechanical support on which multiple

alternating layers of structural and sacrificial material are deposited and patterned to

realize micromechanical structures. The sacrificial material is then dissolved in a

chemical etchant that does not attack the structural parts. The most widely used

surface micromachining technique, polysilicon surface micromachining, uses SiO2 as

the sacrificial material and polysilicon as the structural material.

Micro molding

In the micromolding process, microstructures are fabricated using molds

to define the deposition of the structural layer. The structural material is deposited

only in those areas constituting the microdevice structure, in contrast to bulk and

surface micromachining, which feature blanket deposition of the structural material

followed by etching to realize the final device geometry. After the structural layer

deposition, the mold is dissolved in a chemical etchant that does not attack the

structural material. One of the most prominent micromolding processes is the LIGA

process. LIGA is a German acronym standing for lithographie, galvanoformung, und

abformung (lithography, electroplating, and molding).

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

Packaging

Fabrication Knowledge Required

15

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.

The deflection of a circular diaphragm can be expressed in polar coordinates by the

equations:

P: pressure difference

a , h : radius and thickness of the diaphragm

v: Poisson’s Ratio

r: radial coordinate

E: Youngs modulus of the structural material

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Normalized deflection of a circular diaphragm as a function of dimensionless stress.

The performance criteria of primary interest in pressure sensors are sensitivity,

dynamic range, full-scale output, linearity, and the temperature coefficients of

sensitivity and offset. Sensitivity is defined as a normalized signal change per unit

pressure change to reference signal:

where is output signal and is the change in this pressure due to the applied

pressure P

The temperature sensitivity of a pressure sensor is an important performance metric.

The definition of temperature coefficient of sensitivity (TCS) is:

where S is sensitivity

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INERTIAL SENSORS & 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 ,personal media players…etc. In the below figure an acceleration

will cause a displacement of the inertial mass and the displacement is sensed either

using piezoelectric or capacitive effect.

The simple force equation for a static load

The force obtained from an applied acceleration

K is the elastic spring constant tensor (N/m) and x is the spatial displacement

of the mass with respect to the reference frame generated by the inertial load.

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Deflection of an anchored cantilever beam under a point force is given by:

E is the modulus of elasticity (Pa) for the spring material and h,w, and l are the

thickness, width, and length (m), respectively, of the beam.

A dashpot configuration is needed to help in the damping action to bring the spring to

neutral position in minimal timing.

Consider the following equation of motion for a forced harmonic oscillator:

where m is mass, c is damping coefficient, and k is spring constant. Introducing a non-

dimensional damping , such that

Where is the system’s natural frequency, hence the above equation can

be written as:

And hence the steady state solution becomes

Where is the amplitude of the response and is the phase difference.

Below is a frequency response og the spring .

19

20

MICRO ENGINES

Microengines uses an electrostatic comb-drive (capacitive actuators1) connected to a

pinion gear by a slider-crank mechanism with a second comb-drive to move the

pinion past the top and bottom dead center. Two comb-drives are necessary because

the torque on a pinion produced by a single actuator has a dependence on angle and is

given by the following equation:

where

F0: force of the comb-drive

: angle between hub of the output gear and the linkage

r: distance between the hub and the linkage

Electrostatic comb-drive actuator Linkages that connect the comb-drives to the gear.

The force of the comb drive is found through the following equation:

Where r and o represents the deielectric constants , A is the area , V as the voltage

and y is the distance between the 2 comb electrodes.

1 Capacitive Actuators are actuators utilizing electrostatic forces that act between two

electrically conductive combs

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A DLC BASED 8-CHANNEL MICROPROBE

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

On-Chip to MicroTotalAnalysis (biosensor, chemosensor).Biomedical applications that

have been proposed or developed include implantable devices for measuring ocular,

cranial, or bowel pressure). The DLC based 8-channel microprobe is used for recording

the electrical activity of neural cells and tissues.

This integrated microprobe for monitoring tissues electrical activity can be used labs,

research centers and in hospitals in treatment for people suffering from neurological

diseases. Two sorts of neural activity could be recorded, local field potential and

spiking activity which reflects the neuronal output.

The DLC based 8-channel microprobe

The tip width is:

- 30 mm for 4 channels microprobe

- 60 mm for 8 channels microprobe

The signals collected from the microprobe need to be amplified and processed in

order to obtain useful information.The impedence measurements reveal different

tissue and organs.

22

SOME OTHER COMMERCIAL APPLICATIONS INCLUDE:

Inkjet printers, which use piezoelectrics 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 are also used in uncooled infrared imaging devices which involve

large arrays of microfabricated elements

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.

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).

23

ADVANTAGES OF MEMS DISADVANTAGES OF MEMS

Minimize energy and materials

use in manufacturing

High performance

Improved reproducibility

Improved accuracy and

reliability

Increased selectivity and

sensitivity

Farm establishment requires

huge investments

Micro-components are Costly

compare to macro-components

Prior knowledge is needed to

integrate MEMS devices

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 test, allowing early

detection of hypertension and restenosis. 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.

24

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.

MEMS provided the discovery of the noise increase phenomenon when

miniaturize mechanics is introduced.

References

[1] Sensors and Actuators A: Physical Future of microelectromechanical systems

(MEMS) Minhang Baoa and Weiyuan Wang.

[2] MEMS Applications El-Hak M.G. 2006

[3] http://www.memsnet.org/mems

[4] http://www.memx.com

[5] Senturia, S.D (2001). Microsystem Design. Springer Science Publications.

[6] http://www.kaajakari.net/~ville/research/tutorials/tutorials.shtml

[7] MicroElectroMechanical Systems (MEMS) S. A. Vittorio Oct 2001