1. A Review Paper on MEMS and NEMS Technology
and Devices
Soumya P.Panda
Dept. of Electronics and Communication
National Institute of Technology, Patna
Bihar, India
Anand Kumar Singh
Dept. of Electronics and Communication
National Institute of Technology, Patna
Bihar, India
Abstract—The microelectronics industry has seen explosive
growth during the last thirty years. Extremely large markets for
logic and memory devices have driven the development of the
new materials, and technologies for the fabrication of even more
complex devices with features sizes, now down at the sub micron
and nanometer scale. This paper gives a brief review of history
and components of MEMS and NEMS. This paper will discuss
current and future applications. Further this paper discusses
about their achievements, challenges and requirements. Lastly it
concludes saying that they have enough potential to establish a
second technological revolution of miniaturization that may
create an industry that exceeds the IC industry in both size and
impact on society.
Keywords—MEMS; NEMS; nanotechnology; miniaturisation;
fabrication; smart device
I. INTRODUCTION
One of the major inventions of this century is that of MEMS
and NEMS technology. The acronym MEMS stands for micro
electromechanical system, but MEMS generally refers to
micro scale devices or miniature embedded systems involving
one or more micro machined component that enables higher
level function. Similarly NEMS, nano-electromechanical
system, refers to such nanoscale devices or nano devices.
MEMS and NEMS are fabricated micro scale and nano scale
devices that are often made in batch processes, usually convert
between some physical parameter and a signal, and may be
incorporated with integrated circuit technology. These devices
are not only important for practical applications but are also of
immense importance in fundamental research. MEMS
business worldwide is currently estimated to be close to Rs.5
Lakh Crores. These include sensors, accelerometers, actuators
which form critical components in a range of products
including cars, cell phones and inkjet printers. Fundamental
research interest in these devices include nonlinear dynamics,
origin of noise and damping and observing quantum effects
mechanical structures. MEMS/NEMS devices are sensitive to
a wide range of stimuli such as temperature, mass, pressure
and are thus extensively used as sensors in cars and mobile
phones. The biggest promise of MEMS and NEMS technology
is the development of extremely small sensor systems that can
be used virtually everywhere and thus can impart intelligence
to almost all man-made things. This paper focuses on
discussing about history and components of MEMS and
NEMS. This paper will discuss current and future
applications. Further this paper discusses about their
achievements, challenges and requirements.
II. HISTORY
In 1950's,silicon strain gauge became commercially
available. Thereafter, there was invention of surface
micromachining. With the advent of 1970s came the first
silicon accelerometer. Moreover in the subsequent decade,
there was the demonstration of LIGA process and the first ever
MEMS conference which was a major milestone in the field of
micro and nano technology. In the early 90's, we had deep
reacting ion etching and patenting of Bio MEMS. With the
massive development in technology, the 21st century has
already seen the emergence of MEMS microphones,
accelerometers and vibration energy harvesters. Keeping pace
with the current progress, this industry is expected to grow in
leaps and bounds in the upcoming decades, primarily with the
use of NEMS sensors.
III. COMPONENTS
 Sensors are a class of MEMS that are designed to sense
changes and interact with their environments. These
classes of MEMS include chemical, motion, inertia,
thermal, and optical sensors.
 Actuators are a group of devices designed to provide
power or stimulus to other components or MEMS
devices. In MEMS, actuators are either electrostatically or
thermally driven.
 RF MEMS are a class of devices used to switch or
transmit high frequency, RF signals. Typical devices
include; metal contact switches, shunt switches, tunable
capacitors, antennas, etc.
 Optical MEMS are devices designed to direct, reflect,
filter, and/or amplify light. These components include
optical switches and reflectors.
 Micro fluidic MEMS are devices designed to interact
with fluid-based environments. Devices such as pumps
and valves have been designed to move, eject, and mix
small volumes of fluid.
 Bio MEMS are devices that, much like micro fluidic
MEMS are designed to interact specifically with
biological samples. Devices such as these are designed to
interact with proteins, biological cells, medical reagents,
etc. and can be used for drug delivery or other in-situ
medical analysis.

2. IV. FABRICATION
A. Basic Processes
Deposition processes : One of the basic building blocks in
MEMS processing is the ability to deposit thin films of
material with a thickness anywhere between a few nanometres
to about 100 micrometres. There are two types of deposition
processes - physical deposition and chemical deposition.
Physical vapor deposition (PVD) consists of a process in
which a material is removed from a target, and deposited on a
surface. Techniques to do this include the process of
sputtering, in which an ion beam liberates atoms from a target,
allowing them to move through the intervening space and
deposit on the desired substrate, and evaporation, in which a
material is evaporated from a target using either heat (thermal
evaporation) or an electron beam (e-beam evaporation) in a
vacuum system. Chemical deposition techniques include
chemical vapor deposition (CVD), in which a stream of source
gas reacts on the substrate to grow the material desired. This
can be further divided into categories depending on the details
of the technique, for example, LPCVD (Low Pressure
chemical vapor deposition) and PECVD (Plasma Enhanced
chemical vapor deposition).
Patterning :
a) Lithography: Lithography in MEMS context is typically
the transfer of a pattern into 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 a photosensitive material is selectively exposed 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.This exposed region can then be removed or treated
providing a mask for the underlying substrate.
Photolithography is typically used with metal or other thin
film deposition, wet and dry etching
b) Electron beam lithography: Electron beam
lithography (often abbreviated as e-beam lithography) is the
practice of scanning a beam of electrons in a patterned fashion
across a surface covered with a film (called the resist),
("exposing" the resist) and of selectively removing either
exposed or non-exposed regions of the resist ("developing").
The purpose, as with photolithography, is to create very small
structures in the resist that can subsequently be transferred to
the substrate material, often by etching. It was developed for
manufacturing integrated circuits, and is also used for creating
nanotechnology architectures. The primary advantage of this
technique is that it is one of the ways to beat the diffraction
limit of light and make features in nanometer region. This
form of maskless lithography has found wide usage in
photomask-making used in photolithography, low volume of
semiconductor components and research and development.
c) Diamond patterning: A simple way to carve or create
patterns on the surface of nano diamonds without damaging
them could lead to a new photonic devices. Diamond
patterning is a method of forming diamond MEMS. It is
achieved by the lithographic application of diamond films to a
substrate such as silicon. The patterns can be formed by
selective deposition through a silicon dioxide mask, or by
deposition followed by micromachining or focused ion beam
milling.
Etching Processes:
a) Wet etching: In this process, the material is dissolved
when immersed in a chemical solution .
b) Dry etching: In the latter, the material is sputtered or
dissolved using reactive ions or a vapor phase etchant.
Die preparation: After preparing a large number of MEMS
devices on a silicon wafer, individual dies have to be
separated, which is called die preparation in semiconductor
technology. For some applications, the separation is preceded
by wafer back grinding in order to reduce the wafer thickness.
Wafer dicing may then be performed either by sawing using a
cooling liquid or a dry laser process called stealth dicing.
B. Manufacturing Technologies
a) Bulk micromachining: Bulk micromachining is the
oldest paradigm of silicon based MEMS. The whole thickness
of a silicon wafer is used for building the micro-mechanical
structures.Silicon is machined using various etching processes.
Anodic bonding of glass plates or additional silicon wafers is
used for adding features in the third dimension and for
hermetic encapsulation. Bulk micromachining has been
essential in enabling high performance pressure sensors and
accelerometers that changed the sensor industry in the 1980s
and 90's.
Fig 1. Fabrication in micrometer scale
b) Surface micromachining: Surface micromachining uses
layers deposited on the surface of a substrate as the structural
materials, rather than using the substrate itself. Surface
micromachining was created in the late 1980s to render
micromachining of silicon more compatible with planar

3. integrated circuit technology, with the goal of combining
MEMS and integrated circuits on the same silicon wafer. The
original surface micromachining concept was based on thin
polycrystalline silicon layers patterned as movable mechanical
structures and released by sacrificial etching of the underlying
oxide layer. Interdigital comb electrodes were used to produce
in-plane forces and to detect in-plane movement capacitively.
This MEMS paradigm has enabled the manufacturing of low
cost accelerometers for e.g. automotive air-bag systems and
other applications where low performance and/or high g-
ranges are sufficient.
c) High aspect ratio (HAR) silicon micromachining: A new
etching technology, deep reactive-ion etching, has made it
possible to combine good performance typical of bulk
micromachining with comb structures and in-plane operation
typical of surface micromachining. The materials commonly
used in HAR silicon micromachining are thick polycrystalline
silicon, known as epi-poly, and bonded silicon-on-insulator
(SOI) wafers although processes for bulk silicon wafer also
have been created (SCREAM). Bonding a second wafer by
glass frit bonding, anodic bonding or alloy bonding is used to
protect the MEMS structures. Integrated circuits are typically
not combined with HAR silicon micromachining.
V. APPLICATIONS
 Inkjet printers, which use piezo electrics or thermal
bubble ejection to deposit ink on paper.
 Accelerometers in modern cars for a large number of
purposes including airbag deployment and electronic
stability control.
 Accelerometers and MEMS gyroscopes in remote
controlled, or autonomous, helicopters, planes and multi
rotors (also known as drones), used for automatically
sensing and balancing flying characteristics of roll, pitch
and yaw.
 Accelerometers in consumer electronics devices such as
game controllers (Nintendo Wii), personal media players /
cell phones (Apple iPhone, various Nokia mobile phone
models, various HTC PDA models) and a number of
Digital Cameras (various Canon Digital IXUS models).
Also used in PCs to park the hard disk head when free-fall
is detected, to prevent damage and data loss.
 MEMS gyroscopes used in modern cars and other
applications to detect yaw; e.g., to deploy a roll over bar
or trigger electronic stability control .
 MEMS microphones in portable devices, e.g., mobile
phones, head sets and laptops.
 Silicon pressure sensors e.g., car tire pressure sensors, and
disposable blood pressure sensors
 Displays e.g., the digital micro mirror device (DMD) chip
in a projector based on DLP technology, which has a
surface with several hundred thousand micro mirrors or
single micro-scanning-mirrors also called micro scanners
 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 Micro Total Analysis
(biosensor, chemo sensor), or embedded in medical
devices e.g. stents.
Fig 2. MEMS in Mobile Devices
Fig 3. World's smallest Nano Guitar
 Interferometric modulator display (IMOD) applications in
consumer electronics (primarily displays for mobile
devices), used to create interferometric modulation −
reflective display technology as found in mirasol displays
 Fluid acceleration such as for micro-cooling
 Micro-scale energy harvesting including piezoelectric,
electrostatic and electromagnetic micro harvesters.
 Micro machined ultrasound transducers used in highly
sophisticated cars.

4. VI. FUTURE SCOPE
NEMS stands for Nano-Electro-Mechanical-Systems is the
technology that is similar to MEMS, however it involves
fabrication on the nanometer scale rather than the Micrometer
scale. According to Michael Roukes, NEMS can be built with
masses approaching a few attograms (10- 18 grams) and with
a cross-section of about 10 Nanometers. Processes such as
electron-beam lithography and nano machining now enable
Semiconductor nanostructures to be fabricated below 10 nm.
Although the technology exists to create NEMS, there are
three principal challenges that must be addressed before. The
full potential of NEMS can be realized. First of all,
communicating signals from the Nanoscale to the macroscopic
world can pose a great challenge. Understanding and
Controlling mesoscopic mechanisms are still at the very early
stages. Thermal conductance in this regime is quantized,
which implies that quantum mechanics places an upper limit
on the rate at which energy can be dissipated in small devices
by vibrations. Lastly, we do not have the methods for
reproducible and routing mass nanofabrication; device reprodu
cibility is currently very hard and almost unachievable. It is
clear that if NEMS are ever to become a reality, cleaner
environments and higher precision of Nanofabrication
techniques are needed. As we shrink MEMS towards the
domain of NEMS, the device physics becomes increasingly
dominated by the surfaces. We would expect that extremely
small Mechanical devices made from single crystals and
ultrahigh-purity hetero structures would contain very few
defects; therefore, the energy loses are suppressed and higher
Quality factors should be attainable. However, with the
Possibility of NEMS, which can move on timescales of a
nanosecond or less, the era of the digital electronic age needs
to be carefully re-examined. However, it will be quite a
struggle to reduce the cost of these nano-sensors and also
increase their marketability in case these products ever see
light of the day.
VII. CONCLUSION
The potential exists for MEMS and NEMS to establish a
second technological revolution of miniaturization that may
create an industry that exceeds the IC industry in both size and
impact on society. Micromachining and MEMS technologies
are powerful tools for enabling the miniaturization of sensors,
actuators and systems. In particular, batch fabrication
techniques promise to reduce the cost of MEMS, particularly
those produced in high volumes. Reductions in cost and
increases in performance of micro and nanosensors, actuators
and systems will enable an unprecedented level of
quantification and control of our physical world.
ACKNOWLEDGMENT
We would like to acknowledge the help and support of our
teacher Dr. Waseem Akram who consistently encouraged us to
write a research paper on this topic. We would also like to
thank our parents and friends for their never ending love and
support.
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