MEMS Technology

Visvesvarya Technological University, Belgaum

A Seminar Report On

MEMS TECHNOLOGY

Submitted in fulfillment for the award of

Bachelor of Engineering In

Electronics and Communication Engineering

Madhura S M (1BM07EC054)

Under the guidance ofMr Dinesh

Lecturer, Dept. of E&C,BMSCE

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MEMS Technology

CERTIFICATE

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

B.M.S COLLEGE OF ENGINEERING

BANGALORE – 560019

This is to certify that the seminar entitled MEMS Technology has been carried out by Madhura S M bearing USN 1BM07EC054 submitted in the fulfillment for the award of Bachelor of Engineering degree prescribed by the Visvesvaraya Technological University, Belgaum during academic year 2011 .

Seminar Guide Signature Signature of HOD

DATE:

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MEMS Technology

Contents

Sl No Section/Topic Page No

1. Introduction/overview 4

2. MEMS Description 7

3. MEMS Design Process 8

4. MEMS Fabrication Technologies 17

5. Key applications 19

6. Advantages & comparisons 20

7. Current Challenges 21

8. Future Developments 22

9. Conclusion 23

10. Refrences 24

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MEMS Technology

ABSTRACT

The technology, Micro-Electro-Mechanical-Systems (MEMS), emerged in the

late1980s which enables us to fabricate mechanical parts on the order of microns.

Micromachining technology is suitable for developing new transducers or improving

existing transducer designs. Due to the dramatic reduction in size, micro transducers

can outperform traditional ones by orders of magnitude. Furthermore, MEMS is a

fundamental technology which has the potential to influence advancements in many

fields. In the automobile, electronics, bio-medical and television industries, MEMS

products have already made appreciable impacts.

SECTION 1 INTRODUCTION

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.

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

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individually perform simple tasks, but in combination can accomplish complicated

functions.

SECTION 1.1 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.

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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SECTION 1.2 WHAT ARE MEMS / MICROSYSTEMS?

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

MEMS fabrication 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 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.

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MEMS Technology

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 the movable 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) indicates 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!

SECTION 2 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

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MEMS Technology

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.

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.

SECTION 3 MEMS DESIGN PROCESS

There are three basic building blocks in MEMS technology - 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.

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MEMS Technology

SECTION 3.1 DEPOSITION PROCESSES

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

films of material. 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

2. Depositions that happen because of a physical reaction:

o Physical Vapor Deposition (PVD)

o Casting

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 product of that reaction is a solid material with condenses on all surfaces inside the reactor. 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

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MEMS Technology

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.

Figure 1: Typical hot-wall LPCVD reactor.

ELECTRODEPOSITION

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

to electrically conductive materials. There are basically two technologies for plating:

Electroplating and Electro-less 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.

In the electro-less plating process a more complex chemical solution is

used, in which deposition happens spontaneously on any surface which forms a

sufficiently high electrochemical potential with the solution. This process is desirable

since it does not require any external electrical potential and contact to the substrate

during processing. Unfortunately, it is also more difficult to control with regards to

film thickness and uniformity. A schematic diagram of a typical setup for

electroplating is shown in the figure below.

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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. If an amorphous/polycrystalline substrate surface is used, the film will

also be amorphous or polycrystalline.

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

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. A schematic diagram of a typical vapor phase epitaxial reactor is shown in

the figure below.

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MEMS Technology

Figure 3: 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. As the thickness of the oxidized

layer increases, the diffusion of oxygen to the substrate becomes more difficult

leading to a parabolic relationship between film thickness and oxidation time for films

thicker than ~100nm. 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.

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MEMS Technology

PHYSICAL VAPOR DEPOSITION (PVD)

PVD covers a number of deposition technologies in which material is

released from a source and transferred to the substrate. 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). The thicknesses that can be cast on a substrate range all the way

from a single monolayer of molecules (adhesion promotion) to tens of micrometers.

SECTION 3.2 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 differ (as shown in figure below).

Figure : Transfer of a pattern to a photosensitive material.

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MEMS Technology

THE LITHOGRAPHY MODULE

Typically lithography is performed as part of a well-characterized

module, which includes the wafer surface preparation, photoresist deposition,

alignment of the mask and wafer, exposure, develop and appropriate resist

conditioning. The lithography process steps need to be characterized as a sequence in

order to ensure that the remaining resist at the end of the modules is an optimal image

of the mask, and has the desired sidewall profile. A brief explanation of the standard

process steps included in a lithography module is (in sequence):

Dehydration bake - dehydrate the wafer to aid resist adhesion.

HMDS prime - coating of wafer surface with adhesion promoter.

Resist spin/spray - coating of the wafer with resist either by spinning or spraying.

Typically desire a uniform coat.

Soft bake - drive off some of the solvent in the resist, may result in a significant loss

of mass of resist (and thickness). Makes resist more viscous.

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Alignment - align pattern on mask to features on wafers.

Exposure - projection of mask image on resist causing selective chemical property

change.

Post exposure bake - baking of resist to drive off further solvent content.

Develop - selective removal of resist after exposure. Usually a wet process.

Hard bake - drive off most of the remaining solvent from the resist.

Descum - removal of thin layer of resist scum that may occlude open regions in

pattern helps to open up corners.

SECTION 3.3 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 etching.

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 classic example of this is the <111> crystal plane sidewalls that appear when

etching a hole in a <100> 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.

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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. 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.

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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.

SECTION 4 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

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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

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.

SECTION 4.1 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

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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.

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.

SECTION 4.2 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).

SECTION 4.3 SURFACE MICROMACHINING

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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.

SECTION 5 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 are used in consumer electronics devices such as game

controllers (Nintendo Wii), personal media players / cell phones (Apple iPhone ) and

a number of Digital Cameras. They are also used in PCs to park the hard disk head

when free-fall is detected, to prevent damage and data loss.

MICROENGINES

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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.

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 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).

SECTION 6 ADVANTAGES OF MEMS

Minimize energy and materials use in manufacturing

Cost/performance advantages

Improved reproducibility

Improved accuracy and reliability

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Increased selectivity and sensitivity

Low interference with environment

COMPARISON

CONVENTIONAL MEMS – BASED

Bulky Miniaturised

High power consumption Low power consumption

Mechanical wear and tear Less moving parts

Highly accurate Lower accuracy

Expensive Low cost

SECTION 7 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

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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 find that 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.

SECTION 8 FUTURE DEVELOPMENTS

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

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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 products will be embedded in larger non-MEMS systems,

such as printers, automobiles, and biomedical diagnostic equipment, and will enable

new and improved systems.

SECTION 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, 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.

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.

SECTION 10 REFERENCES

Online Resources

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/

Journals

Journal of Microelectromechanical Systems (JMEMS)

MEMS : Introduction and Fundamentals ( Mohammed Gad-el-Hak)

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