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Good morning to all of you. Welcome to the course on Microsystems and MEMS. So, MEMS
the full name is microelectromechanical systems and this is a very emerging area today and
lot of work is going on around the globe on MEMS and Microsystems and it has got enormous
applications. Today, we will highlight the basic applications and some of the introduction
on MEMS and Microsystems.
Now, the MEMS topic or microsystems is an offshoot of the microelectronics and so to
start the course on MEMS and Microsystems, we will start from microelectronics and let
us look back little bit into the back of the present MEMS which is microelectronics and
we will look into the history on microelectronics.
So, this particular figure you can see the three scientists who are the Bardeen, Brattain
and Schokly from the Bell Laboratories and you know these three scientists first discovered
the Point Contact Transistor which is in 1947. For that discovery they got Nobel Prize in
1956 and that was the first time Nobel Prize was awarded for an engineering device. You
know Nobel Prize is not given for any engineering branch. It is given on basic science, physics,
chemistry, mathematics, and etcetera. But here the Nobel Prize was given in physics
for engineering device.
Later on these three scientists developed a technique by which silicon can be oxidized
and oxidation demonstrated by them in 1953 at Bell Lab. Because of that demonstration
of oxidation from silicon, basically the people started thinking why we cannot make the transistor
on silicon monolithically. The first invention on transistor was a point contact that is
a diskette. Basically, they combined three pieces of silicon N P N and something like
that and then they took contact on each point and they got the transistor action.
This figure you can see is Jack Kilby and he invented integrated circuit in 1958.You can see here so that is the US patent and
which was submitted in February 6, 1959 and this was in September 1958 the patent was
written and that was the first monolithic integrated circuit you can see the picture
here and this gentleman is Jack Kilby and he got again Nobel prize for this particular
device in the year 2000.
So, from that time onwards people are not seeing back and they are proceeding forward,
particularly in the context of miniaturization of different components and making the integrated
circuits. Now this picture you see is the MOS transistor which contains over one million
MOS transistors and that is in early 1990s. Now if you look back to compare the revolution
in the integration of the components, we have to go back to the first transistor which is
also monolithic and that was made in 1960s, where four BJTs and several resistors are
connected together with some metal line. You can see this is a metal contact, this is a
metal born pad, here is another metal born pad and the four transistors and several resistances
were integrated to get some functions off to get some circuit.
Now, after that if we see the what is the status and the what are the trends of silicon
ICs, we have to see this particular figure where this has been obtained from CR route
map and here in one side you can see the minimum feature size of the transistor starting from
1970 to 2020 and on the other side you can see the number of transistors for DRAM chip.
So now look at this figure, here in 1980 where these minimum feature sizes was nearly say
2000 nanometer and then if you go, at present this is the present line 2004 and there you
can see the feature size is nearly 100 nanometer.
So, on the other side, the DRAM chip which is basically always cited the integration
level and that integration level starts from the 4 Kilobyte this is the nineteen four kilobit
DRAM which has come in 1970 and later on you can see from 4 Kilobyte to 64 Kilobyte then
1 Megabyte to16 Megabyte and so on. At present 256 Megabyte DRAM, where this is nearly in
1998 or 99 it came and there transistor count you can see here is one 10 to the power 9
so that means is nearly people are thinking at the moment so transistor level has come
of the order of 10 to the power 10 transistors for DRAM chip.
Now, if you here is one limit by 2010 and 2012, we can see the number of neurons in
the human brain in 15 centimeters cube is nearly 10 to the power 11. 11 is the total
number of the neuron cells and people are speculating that, by that time the number
of transistors for IC or DRAM chip will achieve in that level.
So now, this is another picture you can see which is basically Moore's Law and that gives
you the scaling of the CMOS. That means year to year how the integration is taking place,
you can see from here the model CMOS in 1980 which is nearly one micron technology and
then at present in 2004, the transistor size has come down to 19 nanometer only. Here basically
a route map is given by an international organization and that is the semiconductor route map they
call it, and in the last 34 years the scaling history is such that every generation feature
size sinks by 70 percent.
What do you mean by the generation? The generation basically, on an average of every 2.9 years
they speculate something, they foresee something and after that on that particular year again
depending on the progress of the design and progress of the technology they again just
to control something so the next two years what will happen, so that is basically the
route map. Earlier this generation is nearly 2.9 years but later on the progress is so
fast that has been changed to 2 years recently every two year they are speculating something.
Before that time target achieved, they got something else, much more progress has been
done.
Now, basically the scaling of the CMOS if you can see that the beginning of the some
micron era is started nearly say mid of 85, a mid of 80s that is 1985 nearly in that after
that deep UV lithography then 19 nanometer in 2004. So if you continue in this fashion
so reasonably by 2020, they will come to a limit and that limit of scaling, that means
there the problem is the lithography alignment or which will be the source of lithography.
So, optical lithography is a commercial technique, you know after they highlight, they proceed
to UV, deep UV and then after deep UV there are certain other lithography techniques which
are basically x-ray or lithography but those are not commercially viable.
The people want to stick on optical lithography itself so that's why optical lithography create
some problem after the 90s nanometer and below. Lot of intervention and techniques people
are using in the optical lithography so that they can get the feature size below these
90 or now at present 60 or 65 nanometer people are working on.
But now the silicon microelectronics basically if you see, that is the silicon wafer is 1
0 0 crystal orientation wafer. Now, at present the standard size of the silicon wafer in
industry is nearly 12 inches. Normally in some cases the 4 inch or 6 inch and 8 inch
wafers are also used in some of the small fabs but in big fabs they are working on 8
to 12 inches. Now, you know the lots of circuits are made on silicon wafer and individual single
chip and that is of the order of 2 centimeter square.
I am talking about a larger chip size which you can make now days, is of the order of
2 centimeter square that does not mean that feature size is also very large. Feature size
is very small and if you can get the larger die side that is another achievement. Feature
size goes down and this is known as the die and the die size goes up so that is the challenge
of the technology. Now currently what I just mentioned few minutes back, that the number
of transistors per chip has exceeded the 1000 million. So this is heading towards the billion
and projection in 2014 is 20 billion transistors per chip and that is
the projection at the moment.
Now, here is another diagram, where you can see the feature size goes down, so if you
look into the integrated circuit history, below this is a 0.1 micrometer and this is
10 nanometer range, this is the one transition 0.1 to 10 nanometer and then another transition
level is 10 nanometer to 1 nanometer. So 1 nanometer means this transition is very important
to people and is basically the quantum devices. Now you know the lattice, the constant of
silicon is nearly 3 or 4 or 5 nanometer. Now if you go into 10 nanometer that means few
2 or 3 the atomic diameter is like that. So, that means the few monolayers of silicon within
that if you go into this region then you have to make the devices.
So there, the normal physics of the transistor may not be valid and you have to go into the
quantum mechanical analysis and those are basically the quantum devices. Below that
are atomic dimension and the automatic atomic dimension level, when you make the transistor
lot of other problems will come into the picture. Then here is another table which shows that
the trend of the feature size as well as the wiring levels the mask count and supply voltage
that all this figure tells that is in 1997 where the supply voltage is nearly 2 volts
and in 2003 it is 1.2 volts and people are looking for the circuits and devices which
will work in the 1 volt and at 2012 it's a 0.5 to 0.6 volt.
So, you see how the feature size goes down and at the same time the chip size is going
up as just now I mentioned to 80 millimeter square so they are speculating in 2012 it
will be 1580 millimeter square. The number of transistors in that regime is 1.4 billion
and that is wiring level. That means in the present all the microprocessor chips, the
seven or eight level of metallization is being done there. You know if the number of levels
is more the technology is getting much more complicated and obviously the yield is another
important point which is another yardstick. So, how your technology is good, how it is
commercially viable etcetera, so yield should be very good.
So, for that if number of levels of metallization increases, so then automatically you have
to compromise with some yield but you have to make a compromise on a good yield. At the
same time, number of wiring level increases that is the motto and target. And mask count
is going to increase if the levels are more. So that the interlevel metal you have to have
a dielectric layer then some metal pattern then again another dielectric layer so automatically
the mask level will also increase. So that was the present scenario.
Now the size what i am discussing does matters how you can see this figure here. So, this
is the the area of the micromachining and this Nano machining. So another word you are
coming across now is machining. So machining, the terminology initially it was in mechanical
engineering, people they used to point machining, that means from a huge bulk steel or any of
the metal beam they used to machine it to get small miniature structures. Well later
on the machining is used in microelectronics laboratory also to fabricate the MEMS devices.
Now here you can see the 1meter, that is that elephant and then is gone down to 0.1 so that
is the chip size is you say this is the area where 0.01 meter to 1 centimeter in that area
you can get the IC chip.
Then this is the size of 1 millimeter the grain of sand and then biological cell comes
nearly 0.01 millimeter to 10 micrometer and then
comes 1 micrometer which is the smallest feature size 0.35 micrometer is sometimes back may
be in 1996,97 where that level is micro. Now, if you go beyond that 0.1 micrometer below,
that is entering to the nano area and there some of the examples are shown that the atomic
littering using the scanning telling microscope. This is
1 nanometer, they are obtained from the feature size then DNA is of the 2 nanometer wide that
is the size.
On the other hand if you see the machining, this is the micro machine gear which is nearly
100 micrometer, then this is dust particle side you can compare with that which is a
1 to 5 micrometer and these are some quantum electronic structures, the width of these
structures in nearly 200 Angstrom and the atomic level 1 to 4 Angstrom. So that means,
the size does matters because the with the reduction of the size and minimum feature
size all the technology is going to change and at the same time the equipments are going
to change and if you go below say 1 nanometer level, then physics of devices is going to
change.
So now, if you look here, the size also on the scale that is bottoms up and here it stops
down. So both are shown, here the few areas are is basically plant and animal cell and
this is the bacteria size is the 1 micrometer to 10 micrometer and 10 to 100 micrometers
are plant and animal cell. This is the area where basically the MEMS
are made and now if you go beyond that, which is not microelectronics that is basically
coming nano scales or nano electronic their size comes below the 100 nanometer to say
here is say 1 nanometer. And below 1 nanometer the different area so that 100 nanometer to
1 nanometer, that the size of the virus, proteins and the helical turn of the DNA and this is
the minimum feature size of a MOS transistor in 2004 you can see here. So people are working
so 10 nanometer or 15 nanometer level, obviously, that is the nano scale for the nano and these
are 100 nanometers MOS transistor you can see the gate dielectric is from here to here.
So now, the science of miniaturization with that you can see in case of machine, how the
size is going to reduce. And here the size is basically an accelerometer and here is
a MEMS accelerometer. Now, side by side if you compare you see initially, the conventional,
the accelerometer, the mass was nearly 1.5 Kilo more than that and its size is 15 centimeters
by 8 by 5 centimeter and it requires power of the order of 35 Watts. And on the other
side you can see that, if a MEMS accelerometer if you use so that mass is only 10 grams so
instead of 1587, it has reduced to 10 gram and size is very small compared to these.
Power instead of 35 Watts, is only 1 Milli watt and cost instead of 20,000 Dollars, it
has come down to only 500 Dollars. So, at present the price is further down and you
can get nearly 10 or 50 or 100 Dollars to have MEMS devices.
So, although the microfabrication was originally limited to silicon, now the field is open
people have started using some other materials than silicon particularly the polymers and
ceramics and composite materials and also coming into the picture and people are using
those materials for the MEMS devices and microsystem fabrication. Why people are sticking at the
beginning only on silicon? There are certain reasons. Because silicon technology is fully
mature and there is no new research to be done for the processing of silicon. That is
why they do not want to deviate from the silicon. But later, on the other material particularly
polymer and organic material has some other advantage in certain areas, so they are going
to switch from the silicon to other nonconventional materials also non-silicon materials also
for making MEMS.
So now, the science of miniaturization, if you look into that, although lithography has
been the current method of defining patterns, many forms of direct right schemes are also
being used now a days. Traditional electroplating molding is being used in micro-domain. This
is not used in case of this normal microelectronics. But in case of MEMS we are going to use the
electroplating micro molding and in this liga, all these are coming into the picture and
all the techniques, I will discuss in detail in the future classes.
Now, this is a Micro or Nano world. If you look here, you can see various application
areas. Those application areas are basically, one is the say the physical MEMS or physical
sensors which deals with pressure sensor, force, inertial, sound means that these are
the area where MEMS devices are made. Other area is micro-optics, optical areas which
we call it as MOEMS Micro-Optical Electromechanical Systems. So there is the optical domain, there
are lots of devices made using mircomachining technology. Then another is micro-probing,
the STM and AFM. The AFM components are being made using the MEMS.
Others are the micro-fluidics. Micro-fluidics is a major application in the biology and
not only the biological application, there are others in flow of gas and flow of fluid
in a micro channel, that dynamics is a is a very interesting and there lot of devices
are being made now. This is another area of micro-fluidics. In Bio-MEMS, lot of work is
going and one emerging area of research at present Bio-MEMS area. And by the actuation
and motion that is basically the actuators are also very important. If you want to make
a microsystem, what do you need? You need the sensor, you need actuator and you need
the signal conditioning circuits or processing circuits.
So actuator is one part of the microsystem. So if you look into all the microsensor development
that will not complete the microsystem development. If you want to have some microsystem, you
have to see how the actuators can be made. And it cannot only make how it can be integrated
with the sensor and also the signal condition circuit. So that is why this is another area
of Micro Nano world, how can you make the actuator a precisely working actuator and
is very important which is integrable with the micro sensor.
Now let us look into the MEMS history and if you look there, the gentleman is a fine
man you know, and he basically got a Nobel Prize in 1959. In physics, again he had a
vision and at that time he declared that there is plenty of room at the bottom. That means
on silicon inside you can make lot of small miniature devices and that means there are
a lot of spaces available which people are not utilizing. That vision has come through
in 1959 that has been basically announced. In 1967, if you look that transistor basically
Resonant Gate Transistors came from Wastinghouse, and then in 1989 is another thing that is
basically MEMS device started. This is the picture which is basically 1 micromotor and
has been developed in UC Berkeley.
And then in 1991, you can see the MEMS device which is one digital light processing chip
that is used in DLP projector machine. And in 1993, these are the accelerometer, if you
see commercial MEMS accelerometers coming from analog devices, ADXL series accelerometers
and if you look here that is where actually a chip inside. And not only is the chip, if
I enlarge the picture you see the signal conditioning circuit is also inside. And then the commerce
in 2001 commercial optical cross-connect and switches as coming to the market, that is
a MOEMS devices optical MEMS. So these are basically from 1959 to 2001, the history of
MEMS.
At present, if you see the micro structures made out of the silicon and other materials,
some of the structures are shown: the hinge slider, and this is the one gear, this is
a pin joint, so this is all this made using the micromachining technology. Now there are
two things, one is the MEMS and Microsensors. Sensor is a very important device. Now-a-days,
no system can be made without use of sensor. Lot of sensors is there in any of these microsystems.
So that is basically the difference between sensor and micro is nothing but, the physical
dimension is very very small in case micro sensor and in the range of the sub-millimeter
level.
On the other hand, the M E M S or MEMS microelectromechanical system is a device where microsensors and
mechanical parts, along with signal processing circuits are integrated on a small piece of
silicon. In earlier days, sensors and circuits are not integrated on silicon. But if you
integrate both the devices, then it is known as the microelectromechanical system. Mechanical
means they are basically the mechanical part which means actuation parts. Actuators will
be there, as well as the sensor parts along with the circuits, that is the MEMS.
Now, as the computing power increases, the information systems also move into the physical
world. Lot of the application in physical world using the MEMS and where the MEMS is
playing a major role, that is in particular in case of I/O of input output device of any
of the information system. And they can sense and create motion, velocity, acceleration
they can produce and at the same time in the optical side these devices can reflect or
refract light or radio waves also. And at the moment, the pumps and control fluids gases
reactions gases and reactions are also done with the help of MEMS devices and these are
integrated any of the information system now a days.
Now, the distinctive features of the MEMS are threefold. One is miniaturization, second
is the multiplicity and third is the microelectronics. The miniaturization, i already told you how
the size is bringing down both sensors and actuators, and they are integrated together.
Multiplicity is basically the multiple functions that are being made in a system. If you want
to have a large machine large task, you have to have some small micromachines and those
micromachines are coupled together, integrated together to get best performance on a single
chip that is the multiplicity.
And at the same time, the other advantage is that if you are going to integrate, not
only integrate you are also going to fabricate those devices in batch production. That means
if you make many of the devices from the same chip, automatically cost will be reduced.
At the same time, many machines if you integrate together, they work in parallel, so the total
system if you can think then its cost will also reduce so that means it is inexpensive.
On the other hand, another thing is microelectronics. It integrates microelectronic control device
with sensors and actuators. So these are the three primary distinct feature namely miniaturization,
multiplicity and microelectronics.
Now, the basic microfabrication techniques in case of MEMS are two. One is known, as
I told you machining is the key feature of any of the MEMS devices and there are two
kinds of machining, one is known as the bulk micromachining other is a surface micromachining.
So in bulk micromachining, the first picture you can see the bulk silicon is edged to have
different kinds of shape so depending on the techniques used in fabrication, you can create
a membrane, you can create a rectangular hole or you can create a feature like this. So
here, the yellow color piece is basically silicon and the red color is the passivation
layer and the green color thing here is the stop layer. So, that means there are techniques
used by which the edge can be stopped automatically. That I will discuss in detail in micromachining
lecture. Now, depending on the size of the opening of passivation layer, you can get
different kind of structure from silicon itself. And the bottom picture is taken after surface
micromachining of silicon.
Now here, you can see is one kind of the cantilever and this in a bottom, is basically vacant.
You can see here is a hanging kind of thing and that whole structure is on the surface
of the silicon. So, that means if you can edge with a controlled manner to remove some
of the material, either it is a structural material or it is a sacrificial material to
have different kind of structure at the surface. So that is why it is known as a surface micromachining
and this particular process is fully compatible with the VLSI process and the VLSI chips can
be made on the sense silicon along with these the microsensor, if you go for surface micromachining
technology.
Now, I will just give some of the examples of the structures, so those are one structure
you can see here. So this is basically some of the cantilever beams. Different size of
the cantilever beams you can make out of the silicon and those are hanging and below silicon
has been edged and you see this is another kind of structure the side walls are kept
and a bottom is vacant is removed so these are the various kinds of the microstructure
which is used in many of the devices. On the other hand, here you can see these are diaphragm.
And this is one kind of diaphragm. On the diaphragm, some devices are made and this
is the bonding pads and from where the wires are taken out and these diaphragms is used
for many of the vibrator. In some cases, the diaphragm is used or the membrane is used
and in case of sensors like the temperature sensors or IR detectors. So here is another
structure which is silicon membrane at the bottom of the silicon and this membrane is
basically held by 4 cantilevers.
And this is one fixture of cantilever another fixture and these fixtures are positioned
in such a fashion that the whole membrane is held properly and this on the membrane,
either you can make active devices or also you can make some passive components, or for
actuation also you use the membrane. This side you can see is an electrostatic motor.
This is another MEMS devices and that is another challenge people had solved, that is, motor
which has big size people earlier they had an idea how it can be miniaturized is not
possible now. In the last few years, the R and D had gone in such a level so that a micromotor
of the size of few millimeter you can have that is basically electrostatic motor, and
this is the basically rotor and this is the stator in a side this color is stator this
is a rotor. Now by using the electrostatic field, this rotor can be rotated, just you
can maintain a gradient of the field in the stator so that because of electrostatic attraction,
the rotor can can move from one of the line to another line and again if the gradient
is maintained, it will come here, then it will come here, in this way it started rotating
and this sort of the motors are a very useful to any of the miniature devices. Particularly,
in case of biological application these micromotors are used for microsurgery or knife etcetera
for reviewing some of the biological spaces from the body.
So now, other few examples I am showing here, that is the bulk micromachine accelerometer
from silicon microstructure. So here you can see this kind is a bulk thing, this is a bulk
and this here is some kind of the membrane and from there some structure has been made.
So this is another single chip microphone and that is the back plate, is the gold coated
back plate and here this is the structure, basically vibrator and then the other circuits.
Because in a microphone the first the acoustic signal is received and that is converted into
electrical signal and that signal again amplified later on so, the whole thing can be made out
of silicon, the single chip microphone can be made using the MEMS technology. These are
the some holes; those holes are basically some on the silicon that can be also made
by using the micromachining technology.
Here I showed you earlier one accelerometer chip. There is another accelerometer from
analog devices and here you can see this is basically the acceleration sensor and this
sensor has been enlarged the picture has been enlarged here. In this particular portion,
you can see some pins are there and so because of the acceleration, the movements of these
cantilevers will be either as it is basically the capacity of the surface micromachining
accelerometer. So because of the acceleration, the capacitance will change and that capacitance
change can induce the change in electrical signal and that signal can be processed by
the circuit which are developed side by side, so that no further noise will be introduced
into the system and at the same time there is no loss of signal, so you can get maximum
efficiency of that particular chip and that is the airbag, the accelerometer chip and
lot of applications are there in airbag. I will discuss the applications of the microsensor
in automobile. Then again I will highlight what are the various kinds of the micro sensor
used presently in the automobile industry.
Now, another area is biological application of the MEMS and there, if you see, many devices
are made out of the silicon or the polymer. You can see lab-on-chip, this is the lab-on-chip
and here basically lab means where the diagnostic is being made. That means you see your blood
culture or you want to have your lipid profile. So, blood sample is taken and there are a
lot of chemicals are made and then the after reaction, the regions are analyzed reaction
by production are analyzed. From there they can come to a conclusion that the composition
of the blood like cholesterol level, like creatinine level or the sugar level etcetera.
So now in a chip itself if you have lot of micro cavities and each cavities having some
of the regions, so then automatically if there are certain channel, a small amount of blood
is pushed into a small channel and then it will flow through the microchannel into the
different cavities. The reaction will take place and their sensors are there to know
the different composition, different levels of blood constituents. So at the same time
if we are using small amount of blood, you can have total diagnostic of your blood or
lipid profile you can get it so that is known as a laboratory on a chip.
And another picture you can see these are drug delivery system so drug delivery system
is automatic drug delivery system. That means in many cases you know, particularly in a
hospital or nursing home when the patient is admitted and in the night if the attendant
is not there if he have severe pain, and so if you need some drug for releasing his pain
and if no attendant is available, then there is a lot chaos and problem. So if a small
chip has been developed, so if you fix the chip on his hand, so automatically some pain
is there and some pain killer in a liquid form would be automatically injected into
the body so there is no continuous monitoring is required, the chip itself is a taking care
of. On the other hand a lot of people is having blood sugar, so when to put the insulin into
his body can be diagnosed by particular chip and the chip continuously monitoring the health
and the sugar level of a body and then whenever required the insulin is injected into the
body. So that is the drug delivery systems that mean there you have to have certain diagnostic
feature as well as delivery feature. So it's a very intelligent module or chip and that
is coming now days in many of the advanced hospitals or in patient take care of
places. So, these are drug delivery system, is another solution in the place of continuous
monitoring by some sisters or doctors. So in DNA analyzer, a lot of DNA research is
taking place, gene research is taking place and there also these um the MEMS is playing
a major role. And application wise, others are the food
testing, clinical diagnostic as I mentioned, environment, and bio defense, these are other
application areas. These are some of the pictures of the bio MEMS devices.
Now, the advantages of the MEMS are many fold. And particularly, these MEMS devices now days
which are coming are IC compatible. As I mentioned, if it is IC compatible its performance is
very good and miniaturization has got three fold advantage. Not only size is small, it
is a rugged and at the same time if you reduce the size, then power consumption are also
low. That is another demand of the day so whatever the system or chip you made it, power
consumption should be low as minimum as possible. Because everybody wants the system should
be battery driven. And battery driven means, the voltage level if the whole system should
1 volt, 2 volts or 1.5 volts in that range. So for that you need that the power consumption
should be less so that the life of the battery will be higher. So you have to make innovation
in circuits so that low voltage, low power circuits are added into the feature at the
same time you have to have the miniature device whose power consumption will be extremely
small. And the third one is a batch fabrication. Batch fabrication means the low cost. So automatically
it is obvious if the same batch you can fabricate millions of devices, so cost parts will be
reduced drastically. So these are the three major advantages.
Now the impact on engineering, the MEMS devices and what are its impacts on engineering? So
it is basically a driver for multiple and mixed technology integration. What is mixed
technology and multiple technologies? That means, here technology is not only electronic
technology. So here, they are combining materials technology, electronic technology and mechanical.
Because as i told you, the MEMS means motion is involved. That means the mechanical movement
is involved, so lot of mechanical engineering applications are integrated with electronic
application.
That means, technology is a mechanical technology, materials technology and electronic technology,
all are integrated together. So that is the driver for integration of those and orders
of magnitude increase in the number of sensors and actuators. So that is another potential
impact and the third one is beneficiary of and driver for information systems. So in
a present information age, so MEMS and microsystems are driver for taking the information technology
ahead, many folds in a forward direction. Others are the VLSI, as a design and synthesis
approach for electromechanics, so it is electromechanics. So these are the different impacts on engineering.
Now, again a multiple and mixed technology integration, you require in this particular
area is interdisciplinary research. Because, VLSI is basically the research area where
only electronics and electrical engineering people are involved. But here, in the MEMS
or microsystem technology, the interdisciplinary research and people from different disciplines
are required; physics, chemistry is also, people are also involved in lot of etching
here is a micromachining or etching either it is a liquid or gas etching, lot of knowledge
of chemistry of the materials and devices and gases are also necessary. So knowledge
of chemistry is very much involved here, physics is everywhere, material research is required,
so interdisciplinary team is required for R and D on MEMS and microsystems.
So MEMS will counter the technology for narrow specialization. So people are working narrowly
in different aspects, so in a device simulation design a group of electronic or electrical
engineering people are working only. Material is that material science people are working
now this nano specialization, people have to come out of that narrow specialization
and has to see how we can different knowledge can be coupled together to have a good system
which improves the information, which takes forward the information system or information
age. Teams that best integrate multiple disciplines will be best positioned for future opportunities.
And new materials are also necessary now days because of different applications. What are
those materials? As I mentioned, that polymer is coming in a big way in MEMS devices, because
lot of polymer materials are biocompatible. On the other hand, silicon devices are not
always biocompatible, so that is why lot of emphasis is given now days in polymer MEMS
research. And lots of composite and ceramic materials are also coming into the picture.
And now for making the MEMS devices, first you have to design the MEMS devices. For design,
earlier we used to get some software tools for the VLSI devices. MEMS device tools that
mean stimulation tools were not available. But it gradually the MEMS device simulation
tools or MEMS design tools are available and those are namely MEMCAD or CoventorWare from
Coventor Incorporated USA, another is a MEMS Pro MEMSCAP from France and Intellisense from
Corning USA. These are the three major simulation tools for MEMS design. And other than this,
there are other device simulate not device the design tools are used.
Those are the ANSYS are also being use now days because ANSYS is a basically finite element
analysis simulation tool and is a MEMS and microstructures, has not regular structures
there is a lot the irregularity is there for analysis of simulation of those structures,
you have to go for numerical techniques. And for numerical techniques either finite difference
or finite element tools are very much useful and they are based on those finite element
or finite division difference method these software are developed. And these are some
of the structures obtained from the simulation tools and the mechanical analysis, thermomechanical
analysis, electrothermal analysis; all analysis can be made using that software.
Now I will spend sometimes on the players on the MEMS and microsystem. Some key players
around the globe who are working on this particular area, at the same time who are producing commercial
MEMS devices. So namely, the first is coming into this area is analog device company. They
are concentrated on integrated accelerometers made by surface and micromachining technology.
Their major product is micro accelerometers. Another player is a Motorola. They are concentrated
on pressure sensor made by bulk-micromachining technology. Others are Delco/GM, again the
pressure sensors and accelerometers made by bulk-micromachining technology. The other
one is Lucas Novasensors, they concentrate on pressure sensors and accelerometers and
Texas Instruments integrated micro-mirror projection display made by surface micromachining
technology. The DLP projectors basic technology is coming from the TI. So these are the major
players.
Now worldwide activities if you look, you can see this picture here. So you see the
major activities going on around the globe and just from different countries particularly.
You can see USA and Japan they are far ahead from other countries and here the blue color
represents the companies, number of companies who are involved in MEMS activities and this
color is basically universities or research laboratories involved in R and D on MEMS.
So you can see here the Germany, UK, France, Switzerland, Sweden, Netherland and Korea.
Those countries are involved but industrial or major players in industry are basically
coming from 2 countries which are USA and Germany. And in the Asia, you can see, other
than Japan, Korea is also little bit involved on the MEMS and microsystem R and D as well
as the production level. So in the major players are from Europe. Particularly
Germany, UK, France, Switzerland and Sweden, Netherland there the major R and D locations
are there.
And now, at the end I will give you some of the information or resource information. So
those are very important as we continue this course, so you need some information for further
study and some of the journals which deals with MEMS papers and MEMS research activities
are published. Those are:
Sensors and Actuators (A, B, C) IEEE/ASME Journal of Microelctormechanical
system IEEE journal Journal of Micromechanics and Microengineering
This journals are focused only on MEMS. Biomedical Microdevices
BioMEMS lot of papers are coming there and the related journals were not only MEMS other
devices and VLSI papers are also available. Those are:
IEEE Electron Device Latest IEEE Transactions On ED
Journal of ECS Journal of Vacuum Science Technology
Proceedings of SPIE
So these are the journals.
Now I will give some of the conference regularly, organizing on MEMS and microsensors and microsystems.
They are: Solid State Sensors and Actuator Workshop
every even year is taking place International Conferences Solid State Sensors
and Actuators every odd year is taking place MEMS workshop every year is annual event
MicroTAS even year it is in Europe this conference Eurosensors it is also every year
Many other journals and conferences now have MEMS sections.
Now I will give some of the books which are important for further study. Those are
MEMS and MOEMS Technology and Application by Rai-Choudhury and is SPIE publication.
Micro Mehcanical Systems Principles and Technology T. Fukuda and Menz from Elsevier.
Microsensors MEMS and Smart Devices it is a Gardener and Vardan that is again John Wiely
publication in 2001 it came. It is a very good book and deals with all aspects of microsensors
and MEMS is Gardener and Vardan.
Other than these three books, there are other books available and those are the
Microsystems Design by Senturia, RF MEMS and Their Applications by again Vardan
and Fundamentals of Microfabarication Marc J Madou,
it is also CRC press book Semiconductor Sensors by S.M. Sze,it is also
John Wiley publication and Silicone Micromechining by the Elwenspoek
and the Jansen, is a Cambridge University Press.
So these are few books which are available now a days in print and you can have some
of the books in our library also you can borrow those books for further study and other than
this journals and books, lot websites are available now a days and I will give you some
of the websites addresses also, where you can have lot of information on MEMS research
as well as for the present developments of the MEMS and that those websites are very
important.
You can just open this website and you can see what progress is going on. There are certain
websites the MEMS stock website where you have some queries you and push that query
and in the future you can get answer of those queries also. And like all other subject MEMS
books are not plenty I just mentioned few books may be 10, 20 books are only available
and out of those books few are available in the library, others are not available. So
I would request you to find some of the text books and go through that so for further study
and advance research you can get from website and from the journals. Thank you very much.
Preview of Next Lecture Introduction to Microsensors
So in my last lecture, I have introduced the course MEMS and microsystems. So by now you
know that in MEMS and microsystems one of the important blocks is the sensor block and
today's lecture I will highlight the sensor and I will introduce sensor then will go to
the microsensor and different aspects of sensor its specification required and its technological
aspects, all these things I will discuss in today's lecture.
And sensor is a very important device and now in microsystem we use microsensors and
I will discuss what is microsensor and in particular in MEMS and microsystem we normally
use semiconductor sensors. And again why semiconductor sensors? Because
semiconductor materials are used in many ICs and so if I can make the sensor out of the
semiconductor material then it will be easy for us to integrate both the sensor part and
circuit part together and that's why lots or sensors are coming out making use of semiconductor
materials. And in the first, let us see what sensor means. And sensor basically is a word
it is coming from a Latin word sentire.
And that means to perceive that is derived from Latin word sentire. A lot of definitions
are given for sensors. Basically it gives information about the physical and chemical
signals which could not otherwise be directly perceived by our senses.
Or other parameters which you have to take into account when you are selecting or designing
a particular sensor. Repeatability means, ability of a sensor to reproduce output readings
under identical condition of the measurand that is repeatability.
Same conditions you are applying, the output of the sensors should be same. If it is not
same it is not repeatable and repeatability may lose because of different problems in
your designs, different problems you have made choosing on materials of the sensor and
different problems of your environment condition also. And the stability is another important
aspect and that is ability of a sensor to maintain its performance characteristics for
a certain period of time. So that means, how long your sensor is performing well, that
is the stability. So with this, I just gave an introduction to the microsensors and something
I will continue on this topic in the next lecture also. And then I will discuss on the
evolution of this MEMS sensors as well as market survey Thank you. Let me stop here.
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Lecture - 1 Introduction to MEMS & Microsystems

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