phy605 notes semiconductor materials

MATERIALS,SEMICONDUCTOR MATERIALS, and MICROELECTRONICS

Materials science..

..is primarily concerned with the search of basic knowledge about the internal structure, properties, and processing of materials.

Materials engineering....is mainly concerned with the use of fundamental and applied knowledge of materials so that the materials can be converted into products needed or desired by society.

Materials science and engineering....combines both materials science and materials engineering.

Types of materialsMost engineering materials are divided into three main or fundamental classes;

Metallic materials

Polymeric materials

Ceramic materials

Additional application classes;

Composite materials

Electronic materials

Metallic materials..

..(metals and metal alloys) are inorganic materials that are characterized by high

thermal and electrical conductivities. Examples are iron, steel, aluminum, copper.

Polymeric materials..

..are materials consisting of long molecular chains or network of low weight elements

such as carbon, hydrogen, oxygen, and nitrogen. Most polymeric materials have low

electrical conductivities. Examples are polyethylene, polyvinyl chloride (pvc).

Ceramic materials..

..are materials consisting of compounds of metals and nonmetals. Ceramic materials

are usually hard and brittle. Examples are clay products, glass, and pure aluminum

oxide that has been compacted and densified.

Composite materials..

.. are materials that are mixtures of two or more materials. Examples are fiberglass

reinforcing material in a polyester or epoxy matrix.

Electronic materials..

..are materials used in electronics especially microelectronics. Examples are silicon,

gallium arsenide.

Nanomaterials..

..are materials with a characteristic length scale smaller than 100 nm.

Assignment 1Consider a lightbulb. (a) Identify various critical components of a lightbulb. (b) Determine the material selected for each critical component. (c) Rationalize why the material was selected for each component.

Semiconductor materials..

..are nearly perfect crystalline solids with small amount of imperfections, such as

impurity atoms, lattice vacancies, or dislocations, which are sometimes intentionally

introduced to alter their electrical characteristics

A summary of the chemical elements involved in the formation of semiconductors.

The semiconductors can be elemental, such as Si, Ge, and other chemical

elements from group IV.

They can be also compound, a combination between elements from group III and group V, or respectively, from group II and group VI. Examples for such combinations are the binary compounds GaAs and ZnS.

There are also several combinations of practical importance, which involve two or

more elements from the same chemical group.

Such alloy semiconductors can be binary (e.g. SiGe ), ternary (e.g. AlGaAs ),

quaternary (e.g. InGaAsP), and even pentanary (GaInPSbAs) materials.

Electronic materials include insulators, semiconductors, conductors, and

superconductors.

This family of materials has truly revolutionalized the world. From spark plugs made

from alumina, and copper wires for electrical transmission to components for

wireless communications, high powered magnets used in magnetic resonance

imaging, capacitors, inductors, solar cells, active matrix displays, silicon, and gallium

arsenide based computer chips, electronic materials are found in countless numbers

of applications.

New advances in the materials sciences have led to several breakthroughs in the

developement of new electronic materials. We now have ceramics that are not just

excellent insulators, but also semiconductors and superconductors. Similarly, we

now have polymers that are semiconductive and, more recently, a superconductive

polymer has also been discovered.

Classification of technologically useful electronic materials.

©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

By alloying multiple compounds, some semiconductor materials are tunable, e.g., in band gap or lattice constant.

The result is ternary, quaternary, or even quinary compositions.

Band gap.. Ternary compositions allow adjusting the band gap within the range of the involved

binary compounds; however, in case of combination of direct and indirect band gap

materials there is a ratio where indirect band gap prevails, limiting the range usable

for optoelectronics; e.g. AlGaAs LEDs are limited to 660 nm by this.

Lattice constant..Lattice constants of the compounds also tend to be different, and the lattice

mismatch against the substrate, dependent on the mixing ratio, causes defects in

amounts dependent on the mismatch magnitude; this influences the ratio of

achievable radiative/nonradiative recombinations and determines the luminous

efficiency of the device.

Band gap and lattice constant..Quaternary and higher compositions allow adjusting simultaneously the band gap

and the lattice constant, allowing increasing radiant efficiency at wider range of

wavelengths; for example AlGaInP is used for LEDs .

Materials transparent to the generated wavelength of light are advantageous, as this

allows more efficient extraction of photons from the bulk of the material. That is, in

such transparent materials, light production is not limited to just the surface.

http://en.wikipedia.org/wiki/Light_emitting_diode

http://en.wikipedia.org/wiki/Lattice_constant

http://en.wikipedia.org/wiki/Band_gap

Silicon (Si) and Germanium (Ge)

In solid state electronics, either pure silicon or germanium may be used as the

intrinsic semiconductor which forms the starting point for fabrication. Each has four

valence electrons, but germanium will at a given temperature have more free

electrons and a higher conductivity.

Silicon is by far the more widely used semiconductor for electronics, partly because

it can be used at much higher temperatures than germanium.

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/intrin.html

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html

http://www.google.com/url?sa=i&source=images&cd=&docid=SBQTmENYhiCf9M&tbnid=-ZRZXUMfErfwYM:&ved=0CAgQjRwwAA&url=https://www.powerguru.org/application-fields-and-current-performance-limits-for-power-semiconductors/&ei=fcxxUpbIK4qNrgeU4oDQCQ&psig=AFQjCNE0GYNX0iMlZtdIyo5_oHVfKBgyyA&ust=1383276029828280

Si vs GaAs

Compound semiconductors have both advantages and disadvantages.

For example, gallium arsenide (GaAs) has six times higher electron mobility than

silicon, which allows faster operation; wider band gap, which allows operation of

power devices at higher temperatures, and gives lower thermal noise to low power

devices at room temperature.

Direct band gap gives compound semiconductors more favorable optoelectronic

properties than the indirect band gap of silicon; it can be alloyed to ternary and

quaternary compositions, with adjustable band gap width, allowing light emission at

chosen wavelengths, and allowing e.g. matching to wavelengths with lowest losses

in optical fibers.

GaAs can be also grown in a semi-insulating form, which is suitable as a lattice-

matching insulating substrate for GaAs devices.

Conversely..

Silicon is robust, cheap, and easy to process.

whereas..

GaAs is brittle and expensive, and insulation layers cannot be created by just

growing an oxide layer; GaAs is therefore used only where silicon is not sufficient.

http://en.wikipedia.org/wiki/Optoelectronic

Silicon (Si) vs Silicon Carbide (SiC)

SiC devices belong to the so-called wide band gap semiconductor group,

When compared to commonly used silicon (Si), SiC offers a number of attractive

characteristics for high voltage power semiconductors.

Much higher breakdown field strength

Much higher thermal conductivity

thus allow creating devices which outperform by far the corresponding Si ones, and

enable reaching otherwise unattainable efficiency levels.

Indium Arsenide (InAs)http://www.azom.com/article.aspx?ArticleID=8355

DescriptionIndium arsenide is a semiconductor material made of arsenic and indium.

The semiconductor has a melting point of 942 °C and appears in the form of grey

crystals with a cubic structure.

It is very similar to gallium arsenide and is a material having a direct bandgap.

Indium arsenide is popular for its narrow energy bandgap and high electron mobility.

ApplicationsThe applications of indium arsenide are listed below:

• Indium arsenide is used to construct infrared detectors for a wavelength range

of 1–3.8 µm. The detectors are normally photovoltaic photodiodes.

• Detectors that are cryogenically cooled have low noise but InAs detectors can

be used in high-power applications at room temperature also.

• Diode lasers are also made using indium arsenide.

• Indium arsenide and gallium arsenide are similar and it is a direct bandgap

material.

• It is used as a terahertz radiation source.

• It is possible to form quantum dots in a monolayer of indium arsenide on

gallium arsenide or indium phosphide

• It is also possible to form quantum dots in indium gallium arsenide in the form

of indium arsenide dots arranged in the gallium arsenide matrix.

http://www.azom.com/article.aspx?ArticleID=8355

Toxicity of indium arsenide, gallium arsenide, and aluminium gallium arsenide.Tanaka A.Source: Department of Hygiene, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan. [email protected]

Gallium arsenide (GaAs), indium arsenide (InAs), and aluminium gallium arsenide

(AlGaAs) are semiconductor applications. Although the increased use of these

materials has raised concerns about occupational exposure to them, there is little

information regarding the adverse health effects to workers arising from exposure to

these particles. However, available data indicate these semiconductor materials can

be toxic in animals.

Although acute and chronic toxicity of the lung, reproductive organs, and kidney are

associated with exposure to these semiconductor materials, in particular, chronic

toxicity should pay much attention owing to low solubility of these materials.

Between InAs, GaAs, and AlGaAs, InAs was the most toxic material to the lung

followed by GaAs and AlGaAs when given intra-tracheally. This was probably due to

difference in the toxicity of the counter-element of arsenic in semiconductor

materials, such as indium, gallium, or aluminium, and not arsenic itself. It appeared

that indium, gallium, or aluminium was toxic when released from the particles,

though the physical character of the particles also contributes to toxic effect.

Although there is no evidence of the carcinogenicity of InAs or AlGaAs, GaAs and

InP, which are semiconductor materials, showed the clear evidence of carcinogenic

potential. It is necessary to pay much greater attention to the human exposure of

semiconductor materials.

Direct and Indirect Bandgap Semiconductor

In a direct bandgap semiconductor, an electron can be promoted from the

conduction band to the valence band without changing the momentum of the

electron. An example of a direct bandgap semiconductor is GaAs. When the exited

falls back into the valence band, electrons and holes combine to produce light.

Thus, electron + hole hν

This is known as radiative recombination. Thus, direct bandgap materials such as

GaAs and solid solutions of these (e.g. GaAs-AlAs) are used to make light-emitting

diodes (LEDs) of different colours. The bandgap of semiconductors can be tuned

using solid solutions. The change in bandgap produces a change in the wavelength

(i.e. the frequency of the colour (ν) is related to the bandgap Eg as Eg = hν, where h is

the Plank’s constant). Since an optical effect is obtained using an electronic material,

often the direct bandgap materials are known as optoelectronic materials. Many

lasers and LEDs have been developed using these materials. LEDs that emit light in

the infrared range are used in optical-fiber communication systems to convert light

waves into electrical pulses. Different coloured lasers, such as the newest blue laser

using GaN, have been developed using direct bandgap materials.

In an indirect bandgap semiconductor (e.g. Si, Ge, GaP) the electron-hole

recombination is very efficient and the electrons cannot be promoted to the valence

band without a change in momentum. As a result, in materials that have an indirect

bandgap, we cannot get light emission. Instead, electrons and holes combine to

produce heat that is dissipated within the material. Thus, electron + hole heat. This is known as non-radiative recombination.

Note that both direct and indirect bandgap materials can be doped to form n-type or

p-type semiconductors.

OLED

Organic light-emitting diodes (OLEDs) could revolutionize the market for displays.

OLEDs are..

self-luminous

rich in contrast

extremely flat

video-capable

Numerous manufacturers have now introduced their own brands for OLED products,

including Osram Opto Semiconductors. Osram Opto Semiconductors is currently

producing only passivematrix displays made of polymers.

Two types of organic chemicals emit light when a voltage is applied to them: long-

chain polymers and small molecules. Furthermore, two underlying phenomena are

involved: fluorescence and phosphorescence. And in the field of display technology,

there are two contrasting architectures: active-matrix and passive-matrix. Here, the

anode and cathode consist of narrow conductor paths that cross at 90 degrees and

enclose the polymer layer (see graphic). The points at which these electrodes

intersect form pixels. Light is radiated outward through a transparent electrode made

of indium tin oxide. Passive-matrix displays are relatively easy to manufacture, but

because of losses in their electrical conductors, they are limited in size to screen

diagonals of about five centimeters. This limitation is absent in active-matrix displays,

which are more complex. Here, each pixel is individually activated, which requires an

integrated circuit at the display level. The ideal solution would be thin-film transistors

made of polycrystalline silicon, but they are not yet widely available. If integrated

circuits use competing amorphous silicon technology, however, power consumption

is too high.

In a passive-matrix display the cathode and anode form a square grid. Pixels made

of OLED material are excited by an electrical current, causing them to emit light.

Organic Light Emitting Diode (OLED)

OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by

placing a series of organic thin films between two conductors. When electrical

current is applied, a bright light is emitted. OLEDs can be used to make displays and

lighting. Because OLEDs emit light they do not require a backlight and so are thinner

and more efficient than LCD displays (which do require a white backlight).

OLED vs LCDOLED displays have the following advantages over LCD displays;

Lower power consumption

Faster refresh rate and better contrast

Greater brightness - The screens are brighter, and have a fuller

viewing angle

Exciting displays - new types of displays, that we do not have today,

like ultra-thin, flexible or transparent displays

Better durability - OLEDs are very durable and can operate in a

broader temperature range

Lighter weight - the screen can be made very thin, and can even be

'printed' on flexible surfaces

Flexible and transparent OLED displaysIt turns out that because OLEDs are thin and simple - they can be used to create

flexible and even transparent displays.

This is pretty exciting as it opens up a whole world of possibilities:

Curved OLED displays, placed on non-flat surfaces

Wearable OLEDs

Transparent OLEDs embedded in windows

OLEDs in car windshields

New designs for lamps

And many more we cannot even imagine today...

OLED video

https://www.youtube.com/watch?v=QqyW9vdS0x0

*Video (@youtube)-Bendable smartphonehttp://ceramics.org/ceramic-tech-today/video-new-smartphone-prototype-bends-to-meet-consumers-needs

-the verge

https://www.youtube.com/watch?v=QqyW9vdS0x0

Quantum dot

A quantum dot is a semiconductor nanostructure that confines the motion of

conduction band electrons, valence band holes, or excitons (bound pairs of

conduction band electrons and valence band holes) in all three spatial directions.

The confinement can be due to..

- electrostatic potentials (generated by external electrodes, doping, strain,

impurities)

- the presence of an interface between different semiconductor materials

(e.g. in core-shell nanocrystal systems)

- the presence of the semiconductor surface (e.g. semiconductor

nanocrystal)

- ..or a combination of these.

A quantum dot has a discrete quantized energy spectrum.

The corresponding wave functions are spatially localized within the quantum dot, but

extend over many periods of the crystal lattice.

A quantum dot contains a small finite number (of the order of 1-100) of conduction

band electrons, valence band holes, or excitons, i.e., a finite number of elementary electric charges.

Small quantum dots, such as colloidal semiconductor nanocrystals, can be as small

as 2 to 10 nm, corresponding to 10 to 50 atoms in diameter and a total of 100 to

100,000 atoms within the quantum dot volume. Self-assembled quantum dots are

typically between 10 and 50 nm in size.

Quantum dots defined by lithographically patterned gate electrodes, or by etching on

two-dimensional electron gases in semiconductor heterostructures can have lateral

dimensions exceeding 100 nm.

At 10 nm in diameter, nearly 3 million quantum dots could be lined up end to end and

fit within the width of a human thumb.Note: The above text is excerpted from the Wikipedia article "Quantum dot", which has been

released under theGNU Free Documentation License.

Online source :-- Quantum dot slides - http://www.slideshare.net/mcleang1/quantum-dots

Quantum dots article :-http://nanotechweb.org/cws/article/yournews/37550

http://nanotechweb.org/cws/article/tech/47653

http://nanotechweb.org/cws/article/tech/47653

http://nanotechweb.org/cws/article/yournews/37550

http://www.slideshare.net/mcleang1/quantum-dots

http://www.gnu.org/copyleft/fdl.html

http://en.wikipedia.org/wiki/Quantum_dot

Silicon Carbide Schottky Diodes

The differences in material properties between SiC and silicon limit the fabrication of

practical silicon unipolar diodes (Schottky diodes) to a range up to 100V – 150V, with

relatively high on-state resistance and leakage current. On the other hand, SiC

Schottky barrier diodes (SBD) can reach a much higher breakdown voltage; Infineon

offers products up to 1200V as discrete and up to 1700V in modules.

• Applications

• Server

• Telecom

• Solar

• UPS

• PC Silverbox

• Motor Drives

• Lighting

Features Benefits

• Benchmark switching behavior

• No reverse recovery charge

• Temperature independent

switching behavior

• High operating temperature (T j

max 175°C)

• System efficiency improvement

compared to Si diodes

• Reduced cooling requirements

• Enabling higher

frequency/increased power

density

• Higher system reliability due to

lower operating temperature

• Reduced EMI

• Diodes

Diodes

pn homojunctionsHeterojunctionsMetal-semiconductor junctions

Diodes

Metal-Oxide-Semiconductor FET (MOSFET)Junction FET (JFET)

Field-effect transistors

Heterojunction Bipolar TransistorsBipolar junction

transistors

Solar cellsPhotodetectorsPhotoluminescenceElectroluminescenceLight-emitting diodesLaser diodesImage sensors

Optoelectronic Devices

Tunnel diodeGunn diodeImpatt diodePower bipolar transistorPower MOSFETThyristor

Microwave and Power

Devices

NANOTECHNOLOGY

Nanomaterials are defined as materials with at least one external dimension in the

size range from approximately 1-100 nanometers.

Nanoparticles are objects with all three external dimensions at the nanoscale.

Nanotechnology encompasses the understanding of the fundamental physics,

chemistry, biology and technology of nanometre-scale objects.

Nanoparticles can either be..

- the naturally occurring

(e.g., volcanic ash, soot from forest fires)

- the incidental byproducts of combustion processes

(e.g., welding, diesel engines)

- are usually physically and chemically heterogeneous and often termed

ultrafine particles.

Engineered nanoparticles- are intentionally produced and designed with very specific properties related

to shape, size, surface properties and chemistry.

- These properties are reflected in aerosols, colloids, or powders.

- Often, the behavior of nanomaterials may depend more on surface area than

particle composition itself.

- Relative-surface area is one of the principal factors that enhance its reactivity,

strength and electrical properties.

Engineered nanoparticles may be bought from commercial vendors or generated via

experimental procedures by researchers in the laboratory.

(e.g., CNTs can be produced by laser ablation, HiPCO (high-pressure carbon

monoxide, arc discharge, and chemical vapor deposition (CVD)).

Examples of engineered nanomaterials include..

carbon buckeyballs or fullerenes; carbon nanotubes; metal or metal oxide

nanoparticles (e.g., gold, titanium dioxide); quantum dots, among many others.

Research in the microelectronics and nanotechnology area includes topics such

as..

- Fabrication of new electronic materials and devices.

- Computational studies of electronic devices.

Research in nanotechnology in other field of studies include..

Biology

Medicine

Environment

Energy

Electronics -Patterning and Fabrication

Photonics

Sensors

Material Synthesis

Material Properties and Characterization

Topics regarding nanotechnology may cover..

New materials fabrications

New products applications

Materials Characterization

Cleanrooms

Health Issues

CNT

OLED

Quantum Dots

MEMS

Solar Cells

(from article)

Nanotechnology: Health issuesApproaches to Safe Nanotechnology: Managing the Health and Safety Concerns Associated with Engineered Nanomaterials

This document reviews what is currently known about nanoparticle toxicity,

process emissions and exposure assessment, engineering controls, and

personal protective equipment.

This updated version of the document incorporates some of the latest results of

NIOSH research, but it is only a starting point. The document serves a dual purpose:

it is a summary of NIOSH's current thinking and interim recommendations; and it is a

request from NIOSH to occupational safety and health practitioners, researchers, product innovators and manufacturers, employers, workers, interest group members, and the general public to exchange information that will ensure that no

worker suffers material impairment of safety or health as nanotechnology develops.

Potential Health Concerns

The potential for nanomaterials to enter the body is among several factors that

scientists examine in determining whether such materials may pose an occupational

health hazard. Nanomaterials have the greatest potential to enter the body through

the respiratory system if they are airborne and in the form of respirable-sized

particles (nanoparticles). They may also come into contact with the skin or be

ingested.

Based on results from human and animal studies, airborne nanoparticles can be

inhaled and deposit in the respiratory tract; and based on animal studies,

nanoparticles can enter the blood stream, and translocate to other organs.

Experimental studies in rats have shown that equivalent mass doses of insoluble

incidental nanoparticles are more potent than large particles of similar composition in

causing pulmonary inflammation and lung tumors. Results from in vitro cell culture

studies with similar materials are generally supportive of the biological responses

observed in animals.

Experimental studies in animals, cell cultures, and cell-free systems have shown that

changes in the chemical composition, crystal structure, and size of particles can

influence their oxidant generation properties and cytotoxicity.

Studies in workers exposed to aerosols of some manufactured or incidental

microscopic (fine) and nanoscale (ultrafine) particles have reported adverse lung

effects including lung function decrements and obstructive and fibrotic lung diseases.

The implications of these studies to engineered nanoparticles, which may have

different particle properties, are uncertain.

Research is needed to determine the key physical and chemical characteristics of

nanoparticles that determine their hazard potential.

Potential Safety Concerns

Although insufficient information exists to predict the fire and explosion risk

associated with powders of nanomaterials, nanoscale combustible material could

present a higher risk than coarser material with a similar mass concentration given

its increased particle surface area and potentially unique properties due to the

nanoscale.

Some nanomaterials may initiate catalytic reactions depending on their composition

and structure that would not otherwise be anticipated based on their chemical

composition.

Working with Engineered Nanomaterials

Nanomaterial-enabled products such as nanocomposites, surface-coated materials,

and materials comprised of nanostructures, such as integrated circuits, are unlikely

to pose a risk of exposure during their handling and use as materials of non-

inhalable size. However, some of the processes used in their production (e.g.,

formulating and applying nanoscale coatings) may lead to exposure to

nanomaterials, and the cutting or grinding of such products could release respirable-

sized nanoparticles.

Maintenance on production systems (including cleaning and disposal of materials

from dust collection systems) is likely to result in exposure to nanoparticles if

deposited nanomaterials are disturbed.

The following workplace tasks can increase the risk of exposure to nanoparticles:

Working with nanomaterials in liquid media without adequate protection. (e.g.,

gloves)

Working with nanomaterials in liquid during pouring or mixing operations, or

where a high degree of agitation is involved.

Generating nanoparticles in non-enclosed systems.

Handling (e.g., weighing, blending, spraying) powders of nanomaterials.

Maintenance on equipment and processes used to produce or fabricate

nanomaterials and the cleaning-up of spills and waste material containing

nanomaterials.

Cleaning of dust collection systems used to capture nanoparticles.

Machining, sanding, drilling, or other mechanical disruptions of materials

containing nanoparticles.

(from website)

MEMS Technologyhttps://www.mems-exchange.org/MEMS/what-is.html

What is MEMS Technology?Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most

general form can be defined as miniaturized mechanical and electro-mechanical

elements (i.e., devices and structures) that are made using the techniques of microfabrication. The critical physical dimensions of MEMS devices can vary from well below one

micron on the lower end of the dimensional spectrum, all the way to several

millimeters.

Likewise, the types of MEMS devices can vary from relatively simple structures

having no moving elements, to extremely complex electromechanical systems

with multiple moving elements under the control of integrated microelectronics.

The one main criterion of MEMS is that there are at least some elements having some sort of mechanical functionality whether or not these elements can move.

The term used to define MEMS varies in different parts of the world. In the United

States they are predominantly called MEMS, while in some other parts of the world

they are called “Microsystems Technology” or “micromachined devices”.

While the functional elements of MEMS are miniaturized structures, sensors,

actuators, and microelectronics, the most notable (and perhaps most interesting)

elements are the microsensors and microactuators. Microsensors and

microactuators are appropriately categorized as “transducers”, which are defined as

devices that convert energy from one form to another. In the case of microsensors,

the device typically converts a measured mechanical signal into an electrical signal.

https://www.mems-exchange.org/MEMS/what-is.html

Over the past several decades MEMS researchers and developers have

demonstrated an extremely large number of microsensors for almost every possible

sensing modality including temperature, pressure, inertial forces, chemical species,

magnetic fields, radiation, etc. Remarkably, many of these micromachined sensors

have demonstrated performances exceeding those of their macroscale counterparts.

That is, the micromachined version of, for example, a pressure transducer, usually

outperforms a pressure sensor made using the most precise macroscale level

machining techniques. Not only is the performance of MEMS devices exceptional,

but their method of production leverages the same batch fabrication techniques used

in the integrated circuit industry – which can translate into low per-device production

costs, as well as many other benefits. Consequently, it is possible to not only

achieve stellar device performance, but to do so at a relatively low cost level. Not

surprisingly, silicon based discrete microsensors were quickly commercially exploited

and the markets for these devices continue to grow at a rapid rate.

More recently, the MEMS research and development community has demonstrated

a number of microactuators including: microvalves for control of gas and liquid flows;

optical switches and mirrors to redirect or modulate light beams; independently

controlled micromirror arrays for displays, microresonators for a number of different

applications, micropumps to develop positive fluid pressures, microflaps to modulate

airstreams on airfoils, as well as many others. Surprisingly, even though these

microactuators are extremely small, they frequently can cause effects at the

macroscale level; that is, these tiny actuators can perform mechanical feats far larger

than their size would imply. For example, researchers have placed small

microactuators on the leading edge of airfoils of an aircraft and have been able to

steer the aircraft using only these microminiaturized devices.

A surface micromachined electro-statically-actuated micromotor fabricated by the MNX. This

device is an example of a MEMS-based microactuator.

The real potential of MEMS starts to become fulfilled when these miniaturized

sensors, actuators, and structures can all be merged onto a common silicon

substrate along with integrated circuits (i.e., microelectronics). While the electronics

are fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar,

or BICMOS processes), 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. It is even more interesting if MEMS can be merged not

only with microelectronics, but with other technologies such as photonics,

nanotechnology, etc. This is sometimes called “heterogeneous integration.” Clearly,

these technologies are filled with numerous commercial market opportunities.

While more complex levels of integration are the future trend of MEMS technology,

the present state-of-the-art is more modest and usually involves a single discrete

microsensor, a single discrete microactuator, a single microsensor integrated with

electronics, a multiplicity of essentially identical microsensors integrated with

electronics, a single microactuator integrated with electronics, or a multiplicity of

essentially identical microactuators integrated with electronics. Nevertheless, as

MEMS fabrication methods advance, the promise is an enormous design freedom

wherein any type of microsensor and any type of microactuator can be merged with

microelectronics as well as photonics, nanotechnology, etc., onto a single substrate.

A surface micromachined resonator fabricated by the MNX. This device can be used as both

a microsensor as well as a microactuator.

This vision of MEMS whereby microsensors, microactuators and microelectronics

and other technologies, can be integrated onto a single microchip is expected to be

one of the most important technological breakthroughs of the future. This will enable

the development of smart products by augmenting the computational ability of

microelectronics with the perception and control capabilities of microsensors and

microactuators. 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.

Furthermore, because MEMS devices are manufactured using batch fabrication

techniques, similar to ICs, unprecedented levels of functionality, reliability, and

sophistication can be placed on a small silicon chip at a relatively low cost. MEMS

technology is extremely diverse and fertile, both in its expected application areas, as

well as in how the devices are designed and manufactured. Already, MEMS is

revolutionizing many product categories by enabling complete systems-on-a-chip to

be realized.

Nanotechnology is the ability to manipulate matter at the atomic or molecular level to

make something useful at the nano-dimensional scale. Basically, there are two

approaches in implementation: the top-down and the bottom-up. In the top-down

approach, devices and structures are made using many of the same techniques as

used in MEMS except they are made smaller in size, usually by employing more

advanced photolithography and etching methods. The bottom-up approach typically

involves deposition, growing, or self-assembly technologies. The advantages of

nano-dimensional devices over MEMS involve benefits mostly derived from the

scaling laws, which can also present some challenges as well.

An array of sub-micron posts made using top-down nanotechnology fabrication methods.

Some experts believe that nanotechnology promises to:

a). allow us to put essentially every atom or molecule in the place and position

desired – that is, exact positional control for assembly,

b). allow us to make almost any structure or material consistent with the laws of

physics that can be specified at the atomic or molecular level; and

c). allow us to have manufacturing costs not greatly exceeding the cost of the

required raw materials and energy used in fabrication (i.e., massive

parallelism).

Although MEMS and Nanotechnology are sometimes cited as separate and distinct

technologies, in reality the distinction between the two is not so clear-cut. In fact,

these two technologies are highly dependent on one another.

The well-known scanning tunneling-tip microscope (STM) which is used to detect

individual atoms and molecules on the nanometer scale is a MEMS device.

A colorized image of a scanning-tunneling microscope image of a surface, which is a

common imaging technique used in nanotechnology.

Similarly the atomic force microscope (AFM) which is used to manipulate the

placement and position of individual atoms and molecules on the surface of a

substrate is a MEMS device as well. In fact, a variety of MEMS technologies are

required in order to interface with the nano-scale domain.

Likewise, many MEMS technologies are becoming dependent on nanotechnologies

for successful new products. For example, the crash airbag accelerometers that are

manufactured using MEMS technology can have their long-term reliability degraded

due to dynamic in-use stiction effects between the proof mass and the substrate. A

nanotechnology called Self-Assembled Monolayers (SAM) coatings are now

routinely used to treat the surfaces of the moving MEMS elements so as to prevent

stiction effects from occurring over the product’s life.

Many experts have concluded that MEMS and nanotechnology are two different

labels for what is essentially a technology encompassing highly miniaturized things

that cannot be seen with the human eye. Note that a similar broad definition exists in

the integrated circuits domain which is frequently referred to as microelectronics

technology even though state-of-the-art IC technologies typically have devices with

dimensions of tens of nanometers. Whether or not MEMS and nanotechnology are

one in the same, it is unquestioned that there are overwhelming mutual

dependencies between these two technologies that will only increase in time.

Perhaps what is most important are the common benefits afforded by these

technologies, including: increased information capabilities; miniaturization of

systems; new materials resulting from new science at miniature dimensional scales;

and increased functionality and autonomy for systems.

Cleanroom(from website)

Cleanroom http://www.advancetecllc.com/nanotechnology_microelectronics.html

Whether you require a 1,000 square foot Class 100 cleanroom or a fully functional volume production fab, AdvanceTEC can address your critical requirements for contamination control, code compliance, and process tool fit-up & installation. Our Approach

AdvanceTEC provides comprehensive cleanroom design and cleanroom construction capabilities to serve Nanotech and Semiconductor clients. We understand the technical challenges of these facilities, and deploy the capabilities required to ensure your success.

Requirements Gathering Design and Engineering Construction

Management

Process utility studiesCode compliance evaluationsChemical and gas storage and distribution plansHVAC, mechanical and exhaust systems Estimating, budgeting and schedule development

Process tool infrastructure and services integrationConceptual design, programming and layoutDesign for constructability and maintainabilityBudget creation and schedule optimization

Experienced, salaried Project and Construction ManagementClean Build Protocol constructionCommissioning, certification and training Process tool fit-up and hook-upSite safety

Our Experience

AdvanceTEC has a proven track record of addressing diverse mechanical, architectural and process utility requirements of leading edge Nanotech and Semiconductor cleanrooms.

Applications

Design Approach Facility Types

Bay & chase vs. ballroom Fan Filter Unit (FFU) vs. Terminal HEPA Plenum module, flush grid, rod hung T-grid ceilings Raised access floors vs. other flooring systemsRO/DI water systems

R&D applications labsTrace metals cleanrooms Pilot linesHigh volume wafer fabsTest floors and final packagingMOCVD labsTEM/SEM roomsQuiet Labs

http://www.advancetecllc.com/nanotechnology_microelectronics.html

Design Approach Facility Types

HPM evaluation, design and managementScrubbed exhaust systemsToxic gas monitoring and life safetySubfabs, chemical bunkers and distribution centersy

Radiant Cooled Labs

Cleanliness Classifications

Federal Standard 209e more information

ISO Standard 14446 more information

Class 10 Class 100 Class 1,000 Class 10,000 Class 100,000

ISO 4 ISO 5 ISO 6 ISO 7 ISO 8

(from article)

Nanotechnology (CNT) in Civil/Structural Engineering

Nanoscience and nanotechnology provide enormous opportunities to engineers the

properties of materials by working in atomic or molecular level.

It has not only facilitated to overcome many limitations of conventional materials, but also tremendously improved the mechanical, physical and chemical properties of the materials as well.

To develop high performance, multifunctional, ideal (high strength, ductile, crack free, durable) construction material, carbon nanotubes (CNTs) show

promising role to modify/enhance the characteristics of the conventional construction materials such as concrete and steel. In the paper, a brief on geometry and mechanical properties, synthesis processes,

possibilities and findings of different researchers on CNT reinforced composites is

presented. It is also brought out that a crack free durable concrete is possible if

certain issues such as uniform distribution of CNT in composite and bond behavior of

CNT modified concrete can be addressed. Finally, few pre-proof of concepts are

mentioned where CNTs can play the pivotal role to redefine the scope and ability of

civil engineering, in general, and structural engineering, in particular.

Nanoscience has paved the way to tailor the properties of materials based on

particular requirement by working in atomic or molecular level. In general,

nanotechnology is not an isolated technology for certain purposes, but it is an

enabling technology to achieve many goals by engineering a material at nano level.

Similar to the fields like energy, medicine, electronics, etc., nanotechnology shows

remarkable potentiality of its role to play by opening a new way to solve many of the

perennial problems civil engineers do face every day. Aggressive development of

infrastructures using conventional constructional materials will be responsible for

approx. one-third of global warming. It is estimated that per ton production of cement

approximately produces one ton of CO2. Hence, there is an alarming need for

developing new construction material which is smart, efficient and sustainable. The

countries like India, where growth of infrastructure plays a significant role in the

growth of the country, engineering of green and smart construction material will

enormously help to generate public, private, strategic and societal goods. Among all

the nano forms of metals and non-metals, carbon nanotubes (CNTs) seem to have

the most promising role towards developing an ideal (high strength, ductile, crack

free, durable) construction material like concrete. The carbon nanotubes (CNTs)

attract the researchers since their discovery, because of their higher strength and

relatively low weight. These nanotubes are useful for any application where

robustness and flexibility are necessary. Further, nanotubes are also stable under

extreme chemical environments, high temperatures and moisture as well. Use of

nano engineered concrete would lead to considerable reduction in the dimensions of

the structural members which could result in much less consumption of cement and

thereby reduction of CO2 release and make the world sustainable through eco-

friendly products. Further, carbon nanotubes can also be used to make nano

composite steel. Initial research findings reveal that they are about 50 times stronger

and 10 times lighter than conventional steel. Apart from technical intricacies and lack

of information, one of the main obstacles in using CNTs in construction is cost of

CNTs as construction materials need to be produced in mass and should be

reasonably cheap. Exorbitant cost implications in production of CNTs are

diminishing very fast. For example, cost of industrial CNT was $27,000/lb in 1992,

$550/lb in 2006 and $120/lb in 2011. It is also predicted that the price would be as

low as $0.5/lb in 201314 [1]. To bring out the best from carbon nanotubes to the

construction industry, specifically, in usage of construction materials, the

extraordinary geometrical shape, unparallel mechanical properties, complex but

challenging synthesis processes, and probable areas of applications are essential to

be known. Therefore, an overview of these aspects of carbon nanotubes with the

current state of knowledge is brought out in the present paper.