1. Micro Electronic Mechanical Systems (MEMS)
Abstract:
In the 21st century world has been revolutionized in all the aspects according to the
views and reliable to the modern man. One of such revolution is advancement micro things
i.e.: micro particles to nano particle. And now it could be converted into mems means
microelectronic mechanical systems it is combination of both mechanical systems and
electrical system it size varies from 100 micrometers to 100 nano metres. The
interdisciplinary nature of MEMS utilizes design, engineering and manufacturing expertise
from a wide and diverse range of technical areas including integrated circuit fabrication
technology, mechanical engineering, materials science, electrical engineering, chemistry and
chemical engineering, as well as fluid engineering, optics, instrumentation and packaging.
MEMS can be found in systems ranging across automotive, medical, electronic,
communication and defence applications. The applications of the MEMS in mechanical
engineering plays a vital role in dealing with effective engine operations by providing various
advantageous features like involving of MEMS in carburation, air bag sensing etc. however
the field of research is extending further development of Micro Electronic Mechanical
Systems into Nano Electronic Mechanical Systems(NEMS)
Key words;
Mems
Fabrication- Photolithography, Materials for Micromachining, Bulk Micromachining, Surface
Micromachining, Packaging, Foundry Services
Properties,
Applications,
INTRODUCTION:
This report deals with the emerging field of micro-electromechanical
systems, or MEMS. MEMS are a process technology used to create tiny integrated devices
or systems that combine mechanical and electrical components. They are fabricated using
integrated circuit (IC) batch processing techniques and can range in size from a few
micrometers to nanometres. These devices (or systems) have the ability to sense, control and
actuate on the micro scale, and generate effects on the macro scale
Current MEMS devices include accelerometers for airbag sensors, inkjet
printer heads, computer disk drive read/write heads, projection display chips, blood pressure
sensors, optical switches, micro valves, biosensors and many other products that are all
manufactured and shipped in high commercial volumes.
MEMS have been identified as one of the most promising
technologies for the 21st Century and have the potential to revolutionize both industrial and
consumer products by combining silicon- based microelectronics with micromachining

2. technology. Its techniques and Microsystems- based devices have the potential to
dramatically affect of all of our lives and the way we live. If semiconductor micro
fabrication was seen to be the first micro manufacturing revolution, MEMS is the second
revolution.
In this paper I am going to introduce the mems (micro electronic mechanical system) into
following sections
1. Definition
2. History
3. Fabrication methods
4. Properties
5. Applications
Definition:
Micro Electro Mechanical systems (MEMS) (also written as micro-electro-
mechanical, MicroElectroMechanical or microelectronic and micro electromechanical
systems and the related micromechatronics) is the technology of very small devices; it
merges at the nano-scale into nano electromechanical system (NEMS) and nanotechnology.
MEMS are also referred to as micro machines, or micro systems technology – MST.
MEMS are separate and distinct from the hypothetical vision of molecular nano technology.
MEMS are made up of components between 1 to 100 micrometres in size (i.e. 0.001 to
0.1 mm), and MEMS devices generally range in size from 20 micrometres (20 millionths of a
metre) to a millimetre (i.e. 0.02 to 1.0 mm). They usually consist of a central unit that
processes data (the microprocessor) and several components that interact with the
surroundings such as micro sensors. At these size scales, the standard constructs of classical
physics are not always useful. Because of the large surface area to volume ratio of MEMS,
surface effects such as electrostatics and wetting dominate over volume effects such as
inertia or thermal mass. In the most general form, MEMS consist of mechanical

3. microstructures, micro sensors, micro actuators and microelectronics, all integrated onto the
same silicon chip. Micro sensors detect changes in the system’s environment by measuring
mechanical, thermal, magnetic, chemical or electromagnetic information or phenomena.
Microelectronics process this information and signal the micro actuators to react and create
some form of changes to the environment
However, MEMS is not just about the miniaturization of mechanical components or making
things out of silicon. MEMS is a manufacturing technology; a paradigm for designing and
creating complex mechanical devices and systems as well as their integrated electronics using
batch fabrication technique
History:
When we are talking about mems (micro electronic mechanical system) need to
remembering the famous scientist prof. Richard Feynman. He worked in this project mems.
He inspired to design the mems by seeing objects of dentist drill (1mm), Artey (1mm),
muscle fibre (1micro-m). When he used to manufacture this mems he had a raised a doubt in
this how they going to useful to mankind. Let’s see how could he get solution for this
problem manufacture of integrated circuits, manufacture of transducers, these are instruments
used to store the data and it reuse when he wants(artificial data storing). Then he gets
solution. Let’s see how mems are going to develop in every 10 years
1950’s: 1958 Silicon strain gauges commercially available
1960’s:1961 First silicon pressure sensor demonstrated, 1967 Invention of surface
micromachining. Westinghouse creates the Resonant Gate Field Effect Transistor, (RGT).
Description of use of sacrificial material to free micromechanical devices from the silicon
substrate.
1970’s: 1970 First silicon accelerometer demonstrated, 1979 First micro machined inkjet
nozzle
1980’s:Early 1980’s:first experiments in surface micro machined silicon, Late 1980’s:
micromachining leverages microelectronics industry and widespread experimentation and
documentation increases public interest,1982 Disposable blood pressure transducer,1982
“Silicon as a Mechanical Material” [9]. Instrumental paper to entice the scientific community
– reference for material properties and etching data for silicon,1982 LIGA Process,1988 First
MEMS conference
1990’s: Methods of micromachining aimed towards improving sensors, 1992 MCNC starts
the Multi-User MEMS Process (MUMPS) sponsored by Defence Advanced Research
Projects Agency (DARPA) 1992 First micro machined hinge, 1993 First surface micro
machined accelerometer sold (Analog Devices, ADXL50),1994 Deep Reactive Ion Etching is

4. patented,1995 BioMEMS rapidly develops,2000 MEMS optical-networking components
become big business
Fabrication of MEMS:
However mems are going to fabricate from the silicon family like
1. Single crystalline silicon
2. Poly crystalline silicon
3. Amorphous silicon
4. Silicon nitride
5. Silicon di-oxide
These are various forms of silicon’s have used in manufacturing of mems and useful in
storing the data.
Why silicon’s are used to fabricate the mems properties of silicon made to attempt to
manufacture the micro systems
• Crystalline silicon is a hard and brittle material that deforms elastically until it reaches its
yield strength, at which point it breaks
• Tensile yield strength = 7 GPa (~1500 lb suspended from 1 mm²)
• Young’s Modulus near that of stainless steel • {100} = 130 GPa; {110} = 169 GPa; {111}
= 188 GPa
• Mechanical properties uniform, no intrinsic stress • Mechanical integrity up to 500°C
• Good thermal conductor, low thermal expansion coefficient
• High piezoresistivity
They are different methods are available to fabricate mems from silicon family. They are
•Sacrificial etching
• Mechanical properties critical
• Thicker films and deep etching

5. • Etching into substrate
• Double-sided lithography
• 3-D assembly
• Wafer-bonding
• Molding
• Integration with electronics, fluidics
Of all these methods etching methods are popular in
fabricating the mems.before manufacturing the mems we need to rectify the crystal defects
which are available in silicon crystal. Based on need of the customers several methods are
available to fabricate the mems like Bulk Etching, Wet Etch Variations, Anisotropic Etching,
KOH Etch etc. After fabricating the mems by chemical vapour deposition (diffusion,
oxidation etc) we need to send it for under cutting, corner compensation, bulk and micro
machining
Properties of microelectronic mechanical system:
When we use any material in mechanical system it is necessary to
know basic properties of the material (like tensile strength, Young’s modulus, brittle ness,
and hardness). In that way this mems will attain good values

6. Applications:
The properties of mems lead to vide range of applications in all fields of
technology like mechanical, electrical, bio medical, genetical engineering etc. Let’s discuss
about the fields of extension of microelectronic mechanical system in the automobile field. In
the field of automobile field it works on the operations of carburetion, air bags sensing,
battery storage, sensing the abnormal working of mechanical parts, regulating the combustion
flow rate in the engine cylinder. In the automotive industry MEMS applications hold a lot of
promise. Automotive components need to be produced in very large volumes not only from a
demands point of view, but also from the necessity of recovering the initial investments.
Operating lifetimes of up to 10 years along with very low unit prices are also required. These

7. qualities are inherent in MEMS devices. Due to the progress made in batch manufacturing of
MEMS, large volumes of highly uniform devices can be created at relatively low cost. Two
areas where MEMS devices are currently being used in automobiles are in engine control and
airbag deployment. Manifold absolute pressure sensors are used in engine control of many
vehicles and silicon accelerometers are used to trigger airbags.
1. Carburetion:
Carburetion means preparing of air & fuel mixture and sends into the
engine cylinder through the throttle valve. Based on the engine working condition we
need to send either rich mixture (or) lean mixture. Here while using this mems sensor
it can senses and prepare the mixture and adjust the throttle valve in required
proportion what engine is expected. This leads to increase the mileage of the vehicle
(fuel efficient)
2. Air bags open arrangement:
These helps to protect the driver when he met with any accidents. It
can opens and reduces the pressure to the rider. Generally, here these bags have to
open 100 percent. To achieve this we are using this mems sensor on the vehicle
Apart from these two MEMS devices that are on production vehicles today, there are many
devices that are at various stages of development. Some of these will be used on production
vehicles in the very near future. Application areas where MEMS devices may be seen in
standard production include wheel speed sensing, yaw-rate sensing, active safety and
steering, navigation, seatbelt pre-tensioning, road condition monitoring, etc.
References:
1. Glenn T. Cunningham, “Introduction to MEMS and Microtechnology”, Tennessee
Technological University, Cookeville, TN.

8. 2. Roger Grace, “MEMS/MST Provide Updated Solutions to Many Automotive
Applications”, www.ianmag.com, Oct. 2002.
3. Roger H. Grace, “Automotive MEMS and Their Killer Apps”
4. R. Neul, “Modeling and Simulation for MEMS Design, Industrial Requirements”, Robert
Bosch GMBH, Germany.
5. Sven Krueger, Roger Grace, “New challenges for Microsystems-Technology in
Automotive Applications”, mst news 1/01.
6. Yie He, James Marchetti, Fariborz Maseeh, “MEMS Computer-aided Design”, European
Design and Test Conference and Exhibition Microfabrication, 1997.
7. ABAQUS v 6.4, Examples manual, ABAQUS, Inc. Pawtucket, RI.
8. MEMSCAP Inc., Durham, NC.
9. Berkeley Sensor and Actuator Center, http://bsac.eecs.berkeley.edu
10. Sandia National Laboratories, SUMMiT * Technologies, http://www.mems.sandia.gov
11. Defense Advanced Research Projects Agency (DARPA), http://www.darpa.mil/MTO/
12. Kovacs, G.T.A., Micromachined Transducers Sourcebook, McGraw-Hill, New York,
NY, 1998.
13. Lion, K.S., Transducers: Problems and Prospects, IEEE Transactions on Industrial
Electronics and Control Instrumentation, Vol. IECI-16, No.1, July 1969, pp. 2-5.