In 
the previous lecture which was an introduction.
We have seen some of the devices and we have
seen why the semiconductor devices are important,
how they help us build better systems in electrical
engineering. We also saw what are the various
topics, we are going to cover in this course.
In today’s lecture we will discuss the uniqueness
and evolution of semiconductor technology.
Some of the material in this lecture has been
taken from the chapter: Origin and Personality
of Microelectronics in the book titled “Transistors:
Fundamentals for the Integrate Circuit Engineer.”
This book has been authored by R.M Warner
and B.I. Grung, it is a very nice book. And
if you get a chance to look at this book please
go through it.
Let us begin by trying to understand what
technology? And then we will see what semiconductor
technology? Technology means, processing of
material, energy, or information so as to
develop a useful product. In most general
definition of technology. So you could either
process material, energy in some form, or
even information. That is why now-a-days we
have, what is called, information technology.
Now, when does technology become high technology?
When the processing conditions are very stringent
and when the product that you get it has a
very high reliability and performance and
a low cost. So, either you get the same performance
and reliability but at lower cost or at the
same cost you get much higher reliability
and performance, then the technology is called
high technology. Semiconductor technology
is materials oriented high technology. That
is, it involves processing of materials and
you get products which have high reliability
and much higher performance. Let me give an
example, supposing you take the invention
of transistors, how it has changed the reliability
and performance of systems. Now, before the
transistor was invented the device that was
being used for amplification was a vacuum
tube triode, it was made in vacuum tube.
Now vacuum tube the size of the vacuum tube
is large, if any of you have seen vacuum tube
you would know, compare the size of the vacuum
tube and a transistor. The size is large then
the vacuum tube is fragile because it has
a glass casing. So, it is said that when they
built the first computer using vacuum tubes,
the area occupied by the computer was about
900 square feet and they had a number of engineers
to maintain this whole system because it would
fail very often.ok
Another important problem was how to dissipate
the heat generated. So, whereas you compare
a computer that we use today - a note book
computer or now-a-days you even have palmtop
computers, see the power dissipated, see the
size and see the speed. You are getting much
higher performance and reliability, the computers
are very reliable. So this is what the semiconductor
technology has done and it has given you products
which are very highly reliable and which have
a much better performance. Now it is important
for us to know that this advantage is achieved
only because the material is processed under
very stringent conditions and that is the
price you are paying.
So let us understand that in a little more
detail. What the processing conditions in
semiconductor technology? What is shown here
is a clean room where semiconductors are processed.
You see cannot make devices in open air. You
cannot make semiconductor devices in open
air. So the first stringent condition is that
you need a single crystal material.
Most of the semiconductor devices are made
in single crystal material; this is a very
stringent condition because a single crystal
material means the arrangement of atoms should
be very very regular throughout the size of
the crystal. So.a lot of energy and cost you
are expanding in getting a single crystal
material. Growth of single crystal material.
That is the first stringent condition
The next stringent condition is an ultra clean
environment that is what is seen in this diagram
here, So you see the person who is processing
has wearing a mask and some kind of a attire
which prevents any dirt from him getting into
the environment. This is not only for protecting
him the person against chemicals and so on,
but is for protecting the environment against
pollution by the person. So, you must understand
this that when the size of the transistor
is a very small, of the order of microns or
even submicron; it means that even a very
small dust particle can kill a few transistors
on the chip. Now, how do you measure the cleanliness
of environment? So When people talk about
“the class of the environment” for example,
a class 10 clean room – what does it mean,
this means that there are no more than 10
particles of size more than fractions of a
micron like point three micron in per cubic
feet.
So a class 10 clean room means that the number
of dust particles of a size more than point
three microns is no more than 10 per cubic
feet. To 
give some idea what is involved in creating
such a clean room which is what is required
for semiconductor processing; open air the
class is more than a million. It can be as
bad as that, a lot of cost and energies is
involved in reducing this particle count to
class 10. Another stringent condition: the
water. You need water for processing materials.
So, the water should not have ions, it should
be pure. The water used in semiconductor processing
is called ‘De ionized’ water (D I).
So, how do you measure the cleanliness of
water. You use the resistivity of water. The
resistivity of tap water is about 20 kilo
ohms cm tap water, whereas the resistivity
of water that is used for semiconductor processing
has to be as high as may be 20 Mega ohms.
So you have to remove the ions from the water
so that you get the clean water then you have
clean chemicals ultra clean chemicals.
So, if you look at the bottles that are used,
bottles containing chemicals, when you are
doing experiments in Chemistry, if you have
taken care to see the labels on the bottles
of chemicals there are several grades of chemicals,
starting from the lowest grade like laboratory
grade then you have analytical grade, then
semiconductor grade and even in semiconductor
grade now you have what is called the MOS
grade Metal Oxide Semiconductor grade. Because
to make MOS transistors your cleanliness has
to be even higher, so they have introduced
what is called MOS grade chemicals. So gases
also have to be similarly ultra pure. These
conditions are rather stringent.
In fact the amount of capital investment that
you must do because of these reasons into
a functioning semiconductor manufacturing
unit is enormously high. Even a simple semiconductor
unit making discrete devices, the investment
could be something like 500 crore rupees!
So, it is said that, if you want to compare
different Nations in terms of the wealth they
have, all that you need to do is just count
the number of semiconductor factories these
countries have. So number of semiconductor
factories is the index of the wealth of a
country. This is the reason why even though
the products are very useful and of very high
performance, unless you have large amount
of capital invest invested in this you cannot
make these products. So you can call this
as one of the limitations of technology. In
spite of the high capital investment, the
cost of the product becoming lower is because
the production volume is very high.
You are able to generate new applications
with products which are high performance,
which are very light and so your production
volume is becoming very high and that is how
the capital investment, the cost that you
are putting in it gets divided, and that is
why the computers and pocket calculators and
so on are becoming so affordable.
One big unit trying to make large number of
products that is how this particular technology
works. It has its advantages and disadvantages.
The disadvantage is, only a very rich country
or very rich man can set up such a unit and
then he or she may be able to control, that
is the disadvantage of this. There are many
aspects of technology that one needs to understand.
I have focused here a few of them which are
related to the semiconductor technology.
Now, another thing is the sophisticated equipment
which is also responsible for the high cost
of the semiconductor unit. Most of the equipment
for example, we use for this manufacture in
India are imported. You can also see in the
diagram the cleaner benches - the environment
which is maintaining higher level of cleanliness
in the place that you are processing. The
room itself is clean but the particular environment
in which you are processing the silicon pieces
and so on; subjecting it to various chemicals
is even more cleaner.
So, for example, what you see here is called
the cleaner benches. In fact this person is
processing in a cleaner bench. The cleanliness
is maintained of the air a higher cleanness
is maintained by maintaining a slightly positive
pressure in the region where the processing
takes place. So the air is sucked in from
outside through some filters and then it is
pumped into this region and then the air flows
out and this way the positive pressure is
maintained, constantly air is coming out of
that region, that is how you can prevent the
dust particles from entering into the region.
That is how the cleaner bench is made. Let
us discuss some other things related to this
technology.
Products of semiconductor technology: Unlike
in many other technologies, the use of the
products becomes progressively easy with advancement
of technology. It is a very unique feature
of semiconductor technology.
To give an idea, supposing you take automobile
technology. In automobile technology, lets
take the products which will reflect advancement
in the technology. Let us start with the cycle,
not really an automobile but the simplest
thing that gives you the mobility. To start
with, the cycle, and go to scooter, then go
to a car, then you can go to may be an aircraft,
and then probably you can talk about a spacecraft.
So you see advancement in technology. The
person who is operating this vehicle needs
higher and higher levels of skill, almost
everybody can ride a cycle, few can ride a
scooter. For car again you need much better
training and then you go to the aircraft and
then you go to the spacecraft.
This is one example where as technology advances
you need higher and higher levels of skills
to use the product. Whereas in the case of
semiconductor technology what you find is,
as technology advances it becomes more and
more user friendly, so even an illiterate
person can use this can make use of the products.
The level of skill required is very less.
There is something very positive about this.
Another unique feature of this technology
is that, the second point in the slide, the
performance of new products can be predicted
using relatively simple models and this is
because you are using the single crystal material.
Though the single crystal material is difficult
to make but the performance of devices which
are made in this material is easy to predict
because you have regular arrangements of atoms,
so modeling is easy. That is why you have
so many simulators and so on which are used
to predict new devices even before you make
them. This is not something that is easy in
other materials. For example, in glass and
steel the performances cannot be predicted
so easily because these are not single crystal
materials.
Now, let us come to the training required
in semiconductor technology. The theory of
semiconductors is abstract and also if you
see the technology in its totality it is highly
interdisciplinary. For this reason, you need
a strong training in Mathematics as well as
in Sciences to really be effective in this
technology.
So, a person who is working with steel or
glass the level of training required is much
less than a person who is to be trained in
semiconductor technology. So, you will see
that A semiconductor industry or lab, for
example, appoints people ranging from Mathematicians,
Chemists, Physicists, material Scientists,
electrical Engineers and chemical Engineers;
so they need people of all use to really make
the technology work. That is why we have students
undergoing a theory course before they are
taken to the practical class.
Those who are working with steel and glass
can start playing with the material and with
a large amount number of trial and error they
can come to some understanding of the material.
But that is not the way one enters the semiconductor
technology. One does not start playing with
silicon and then you find you get interested.
So let us understand this more and then let
us take a course. That is not the way it works.
You have a course on devices and so on and
technology and then you start practicing.
So let us look at the evolution of this technology.
What I said just now, that a high level of
training is required. This is because, in
this technology, the Science came first and
the empiricism came later. Some of these features
we will see when we see the sequence of events
which I am going to just talk about in a short
while.
Again taking the example of other materials
like glass and steel people have been working
with these materials for 100s or may be 1000s
of years. They did not have an understanding
of the atomic structure or molecular structure
of steel or the structure of the glass before
they started working with these materials.
But by doing lot of trial and error experiments
they have perfected the art of making better
and better steel and glass and so on.
The understanding of the structure has come
only recently in last 200 years or something
like that. Of course that must have also helped
them to build better material there is no
doubt. But a lot of progress has taken place
even before the Science of the materials was
understood. But that is not true of semiconductors.
In semiconductors first came the Science,
that is, lot of experiments were done and
they found that semiconductor materials have
different set of properties than metals and
insulators, then they tried to understand
the structure and so on. And after they understood
the structure then they realized that may
be you can do large number of things with
this particular material. And that is how
this area has acquired importance. So this
is what is meant by Science first, empiricism
next. Trial and error experiments come later
after understanding the Science. The only
other example in this category is nuclear
Science or nuclear technology and even there
the Science came first and then empiricism
or the practice of this.
The second important point is that in the
growth of this technology, Scientists, Engineers
and Inventers all these three types of people
have contributed extensively. Often we use
these terms interchangeably scientists, engineers
and inventers. Many times these are used interchangeably.
But it is not true if you try to look at people
who have been working and you understand what
Science is, what Engineering is and what invention
is. The type of people, their capabilities,
their way of working is quite different. So
a person who is a good Engineer may not be
a Scientist.
Similarly an inventor need not be a good Scientist
or they can be a Scientist who is not an Inventor.
So these three types of people have contributed
extensively to this technology. We will see
a little bit on Science, Engineering and Invention
because it has a relationship to this topic
that we are discussing.
Another important thing that you need to understand
about evolution is that this technology the
interest in the technology was driven initially
by the need to improve communications. How
to improve communication, how to make communication
faster, and more effective that was the goal.
So in beginning it was found that this technology
will help you to improve communication and
that is how the interest developed. But after
the technology developed, now, the communication
is being driven by all the developments that
you have in this technology. It is the other
way around now, the communication field is
being driven by the solid state field.
So let us understand the difference between
Science, Engineering and Invention. In Science
the ultimate goal is publication of new knowledge
frequently mathematical. The ultimate goal
of Scientist is to publish a book, a paper
or something like that which deals with which
establishes new links and patterns of understanding
and integrates seemingly unrelated observations
and phenomena into a grand pattern. That is
the job of the Scientist. So definitely a
Scientist is highly intellectual. But the
important thing is whatever he or she does
need not result in a useful product. It is
some sort of a publication which details this
knowledge.
As against this since we are supposed to be
engineers at least IITs are supposed to produce
engineers or inventors those who have few
characteristics what are those characteristics.
In Engineering the ultimate goal is the product.
The requirements for Engineering are knowledge
of scientific principles and Applied Mathematics,
hands on experience - this is very important
hands on experience. So if someone says that
he or she is working in the area of semiconductor
technology or an Engineer or a technologist,
then it is not sufficient to just take a few
courses and understand what are the fabrication
steps in the for a semiconductor device and
how a device works and so on. He or she must
have hands on experience, must have used the
material, processed it and so on, then the
ability to approximate.
This is another important property that an
Engineer must have. So an Engineer must be
able to work with very simple formula; derive
simple formula for design purposes. And then
finally one aspect of engineering that is
related to economics and so on unlike Science
you cannot deal Engineering by Economics that
much.
Entrepreneurship: (25.22) that is, you must
have a person who sets up a unit that translates
all these practical knowledge and so on into
a useful product. So in fact the level of
Engineering in any country also depends on
what is the extent of entrepreneurship in
the society. How many people are trying to
set up units which will make products. They
might fail but the question is how many trials
have been made.
So it is found that those countries which
are advanced engineering there the number
of people who try to setup units, who try
to be entrepreneurs is very very high. If
you compare for example, United States and
India, in United States you will find the
number of entrepreneurs is very large. May
be one in four only succeeded but the number
who are trying is very high. So this is also
an important requirement for Engineering.
Let us look at the invention. What is invention?
It is a useful new combination. Let us consider
examples in the context of semiconductor technology.
So I have given here two examples, one is
called the planar process and the other is
the Pocket Calculator. Planar process is the
process invention and pocket calculator is
the product invention. Let us discuss this
point in little more detail.
What is the planar process? In fact the person
who worked with this planar process who used
it for making IC has got a Noble prize recently.
You know all of you. Who is the person who
got the prize? In fact this is the only example
where an Engineer has been given a Noble prize
for the invention because the integrated circuit
has revolutionized the entire Electrical Engineering.
And in fact you can say the whole life. A
number of systems, different kinds of systems
that has been built and the amount of new
Science that has been generated, because in
trying to understand integrated circuit is
so large so that the person was given a Noble
prize. So, that is why let us look at this
planar process.
You can make a diode as follows, which was
the initial process that was used in olden
days, when I say olden days that means in
the beginning of the evolution of semiconductor
technology. That is, may be 50 years ago.
So this is a structure of PN junction made
by what is called the MESA process.
That is, the structure looks like a MESA pyramid.
So here, how is this device made? Well you
have a wafer or a piece of silicon, N type
silicon, whole of which at the surface is
converted into P type. The size in those days
could be of 2 inch diameter; it is a circular
wafer, a circular piece.
The thickness of this is of the order of 200
microns. To give you a feel for this thickness
- the human hair is about 50 microns diameter,
so this is about four times the thickness
of the human hair. This thickness depends
on this diameter because you must be able
to handle the silicon piece mechanically.
So for 2 inch diameter wafer it is about 200.
Convert the whole of the surface into P type
but your individual diode is very small. So
you have to separate this particular wafer
into individual diodes. So how do you do that?
Now that is where what you do is you etch
out locally, the materials. And then you dice
or break the wafer at these points. Now each
of this device is shown here separately.
When you separate this particular wafer into
devices, what will happen is the surface will
be exposed to the atmosphere, and impurities
can get in there which will spoil the characteristics
of this diode. So what is done is, you have
what is called as a passivation layer. So
it is some material which you put here so
that the surface junction is protected from
environment, this is the MESA process. What
we want to talk about is the planar process.
After understanding the MESA process, now
we will appreciate the innovation involved
in the planar process. These particular diodes
were quite leaky, that is the leakage current
was high.
You see the diode characteristics, this is
current versus voltage. So reverse characteristics
this represents the leakage current. That
leakage current was high for these devices.
Now let us look at the structure of the diode
which is made by the planar process.
So, first I will draw the individual diode
structure and then we will discuss how this
individual diode is separated from a complete
wafer. This is a structure of a planar process,
the device made by a planar process. So here
what is happening is this is the so called
passivation layer made of silicon dioxide.
And what you find here is the junction is
on a plane surface and that is why it is called
a planar process. The PN junction is exposed
to the atmosphere and wherever it is exposed
that is on a plane surface, that is why it
is called a planar process.
All the devices are made on a single plane.
However, here you can see that it is not a
planar device because the structure itself
is like a MESA. So the advantage of this is,
now the PN junction is automatically passivated.
It turns out that the silicon silicon dioxide
interface can be made of a very high quality
and the leakage current of this device is
therefore much lower. That is not the only
advantage of planar process or rather even
the main advantage. The main advantage is,
now it makes very easy for a person to integrate
various devices on a single surface, that
is the main property of the planar process.
You can make different devices in a single
plane.
So 
I can have a diode like this and then I can
have a transistor, so this is an example where
I am showing a diode and a transistor in the
same silicon wafer. This is the so called
emitter contact, this is so called base contact
and this is the so called collector contact
and they are all in the same plane.
Look at this MESA process, here this is the
top contact and this is the bottom contact.
Whereas for PN planar diode both the contacts
can be on the top, this is P contact, this
is N contact. That is what is happening for
the transistor also, all the contacts namely
the emitter, base and collector are on the
top on the same plane. So you can integrate
this very easily. I can run a metal line,
suppose I want to connect this region to a
diode for some reason, I can just run a metal
line here and connect, so interconnection
of various devices on a single plane, that
is uniqueness of this and it is this arrangement
that enables you to build large number of,
millions of transistors or devices on a single
silicon wafer because you can go on shrinking
the sizes and you can increase the density
of the surface. Incidentally these two regions
are called isolation regions which should
be P type so that the PN junction along this
area isolates this transistor from other devices
and prevents unwanted interconnections between
them. So PN diode, for example, made by planar
process will have much lower leakage current
than a PN diode made by MESA process.
Also MESA process will not enable you to integrate
various devices. So here how is this diode
made? The sequence of steps is as follows.
You take the same wafer N type wafer, but
the first step in a planar process is to grow
the silicon dioxide layer which is the so
called passivation layer, then you etch windows,
that is areas where you want the P region,
you remove the silicon dioxide. And then in
these regions you create P regions by a diffusion,
process called diffusion, that is, introduce
impurities through this particular window
so as to create the P regions. Now automatically
what happens is since the impurity is diffused
inside they also diffuse sideways and the
junction goes and sits under the passivation
layer, automatically it is under the passivation
layer.
So as I have said the silicon silicon dioxide
interface can be made of a very high quality.
It is possible to make a very high quality
interface using simple means and therefore
it enables you to get very low leakage current
and very good passivation. The surface is
protected against the environment. So now
this was a process invention which made possible
putting larger and larger number of devices
in smaller and smaller area, the planar process.
Now you have some such invention it gives
you a jump, it opens up many possibilities.
Now the next question arose, you have the
capability of integrating large number of
devices in a small area, but what do you do
with this capability, what product you make,
because this is also very important, what
is the product that will be very useful out
of this particular capability? So, in fact
one of the first products that were thought
of was the pocket calculator. So someone said
we can use this technology and make a small
device which will calculate and everybody
can have this device in his or her their pocket.
When the suggestion was made people made fun
and said it is not going to be very useful
at all.
Now-a-days we know almost everybody needs
a calculator. So, the product invention of
a pocket calculator is a very important invention.
It looks like a very simple idea. That is
how all inventions which are very wide capability.
All inventions which are wide applicability,
their property that they are very simple in
consumption. Pocket calculator is a product
invention which showed how you can exploit
this planar process capability and make a
useful product.
Having understood the Science, Engineering
and Invention. Now let us see how three people
have contributed to the growth of semiconductor
technology. Here what I have done is I have
listed a number of important events in a chronological
order. The events are listed for communication
field area of communication, because as we
have said the interest in this technology
initially allows the because of the need to
improve communications and then, side by side
the developments in solid state, science of
solid state. One can trace it back to 1820,
the development that initiated the communications
field was magnetism from electricity and vice
versa, Orested and Faraday; the idea of electromagnetic
induction and so on. So here you have the
suffix indicated against the names of the
persons associated with this event. S stands
for Scientist, I stands for an Inventor and
E stands for an Engineer.
So one of the purposes of this particular
phrenology is to show how a Scientist develops
an idea and then comes an Inventor who exploits
it and makes a useful product. That require
sometimes the knowledge of some new observations,
so again you have a Scientist who comes in
their and who explains some of the new observations,
this results in more knowledge and new knowledge
and again then there is an inventor coming
in who exploits this new knowledge that is
developed. So you have the sequence going
on, Scientist - inventor and so on.
So here, for example in communications you
can see that after 
understanding ideas of magnetism from electricity,
Morse was an inventor who came up and proposed
the telegraph. How to use these ideas for
communication? Communications with wires,
then you have the theory of Electromagnetism
being given by Maxwell. On the right hand
side you can see the developments in solid
states.
Here the two strands are separate and there
is no connection between them, as of now,
as in 1820. So you have a set of Scientists
studying the solid state materials - thermoelectric
property. So they were studying the thermoelectric
property of various materials, they found
some materials seem to be showing some unique
features in this property; then came the intrinsic
property and photovoltaic effect by Faraday
and Becquerel, then photoconductivity.
After the studies of all these properties,
there was an inventor who suggested that we
can use these unique properties of material
and till then it was not known or the word
the “semiconductor” was not coined by
1870. But the Scientists understood that there
was some material which behaved in a peculiar
fashion; neither like metals nor like insulators.
So Braun was an inventor who said that you
can put a metal contact to this material and
it will have rectifying property instead of
having a resistive property, that is, the
current for one polarity of voltage is very
different from current for other polarity.
And then he said we can use this kind of a
device in communication for detection.
First device that was proposed by was an inventor
Braun and thereafter again you have Scientists
studying the properties of semiconductors
in the solid state field.
Telephone was an invention by Graham Bell
for improving the communications. After that
you had an experimental proof of electromagnetic
waves by Hertz who was a Scientist. Maxwell
gave the theory for electromagnetism, but
the presence of electromagnetic waves practically
was demonstrated by Hertz, so moment this
was demonstrated, came an inventor that is
Bose-Marconi, there is still some confusion
as to who is the original inventor of wireless
communication.
The latest information is that Bose was probably
ahead of Marconi in this. Then you had vacuum
tube Diode and Triode, again an inventor came
up and proposed the device for detection in
wireless communication.
How do you detect the radio waves? We use
this device for detection; on the right hand
side here you see magneto resistance being
studied in solid state and then the understanding
of Quantum Mechanics by Max Plank and photoelectric
effect by Einstein. It was in 1910 that the
word semiconductor was coined. They found
that this set of materials had so many unique
properties that they wanted to give it a separate
name which is not an insulator, not a metal
and not a conductor. So the word semiconductor
was coined in 1910. At around this time the
communications field was still developing,
you can see that positive feedback and sine
wave oscillator, how do you generate the signals
required for communication? This was the topic
that was addressed by Armstrong. To proceed
further, in the area of communications you
have an engineer coming in here. Armstrong
also as you can see was an engineer and an
inventor.
Similarly Herald Black proposed a negative
feedback which was very useful in building
good amplifiers, again for communication purposes.
Then you had frequency modulation, Armstrong
proposed, so you had lot of developments in
the field of communications here. Now, after
1920 because of the importance of radar in
World War II this is the important event which
actually brought the communications and solid
state fields together.
There was certainly lot of interest in the
solid state area because they found that using
the vacuum tube which was used for detection
in communications could not go to very high
frequencies and that is where they found that
the diode proposed by Braun which was simply
being considered as a rectifying device was
very useful as a detector.
Instead of a vacuum tube diode, he used a
solid state diode, it is much better it is
very small in size, it has a small capacitance
and therefore you can use it at higher frequencies.
We started perfecting this device, beyond
this the solid state and communications which
where as separate areas joined together. And
thereafter you have an inventor coming here
in this area of solid state, the semiconductor
triode. If a Braun’s diode can replace a
vacuum tube diode and give you much better
performance, then people thought why not replace
the vacuum tube triode, vacuum tube amplifier
by a solid state amplifier.
So someone suggested how you can translate
this idea of vacuum tubes into a solid state
field. When we discuss the MOSFET we will
discuss about this particular invention of
the semiconductor triode a little more in
detail, the field effect transistor. And thereafter
the interest in the area of semiconductor
grew exponentially and you can see a large
number of models to explain the behavior of
semiconductor devices, the first important
model being the Energy Band model, then the
Theory of Rectifying Junctions and so on.
And in around 1950 that is in exactly in 1947
was the invention of the first solid state
amplifier that is the discovery you can say
the Bipolar Junction Transistor (BJT).
So although the first transistor that was
proposed is the field effect transistor, the
first device that was made is the Bipolar
Junction Transistor because they were not
able to make Field Effect Transistor and in
trying to study why Field Effect Transistors
were difficult to make, they discovered accidentally
the Bipolar Junction Transistor. And thereafter
you have the Planar Process being used for
integrated circuit by Noyce and Kilby.
So in fact Kilby got the Noble prize for his
invention of integrated circuit and thereafter
now we have the solid state area progressing
and driving the communications. So you had
series of devices being proposed MESFET, proposed
by Mead then you had medium scale integration,
the integration of devices into IC started,
filters, then you had large scale integration
being used for making a Random Access Memory
and analog to digital converters, microprocessors
and so on.
Then in 1980s you had the High Electron Mobility
Transistor (HEMT), and then in integrated
circuits you had VLSI that is 64 KB Random
Access Memory (RAM). In 1990s you had three
dimensional integration that is, you integrate
not only on a plane but also in the vertical
dimension.
Most recently we have had Nano electronics
coming up wherein we make devices out of either
Nano crystalline materials or we make devices
which are of Nano dimensions but made in crystalline
materials.
Now having seen the way the semiconductor
technology has evolved and how Scientists,
Engineers and Inventors have contributed to
this evolution, let us briefly review the
status of India in this technology. Broadly
we could divide the technology into three
levels: the software level, the hardware level
which involves architecture and assembly,
and finally the devices or components level
which is heavily dependent on materials.
The capability index for this technology is
indicated here, we are doing very well in
software, so that is A, excellent or very
good, we are exporting software, in the hardware
level we are good, we can make super computers
and we are sending satellites into space so
this level involves integrating components
and making systems.
However, at the devices or components level
we need improvement, that is presently the
level is not satisfactory as U - stands for
unsatisfactory and we are improving but we
need to improve more. The reason why we are
weak at the devices or components level is
because we are weak in the area of material
oriented technology so we import the technology
for making sewing needles which is based on
the processing of steel material, so it is
not surprising that we imported technologies
for making semiconductor devices, semiconductor
and steel both are materials. Now the chain
is only as strong as the weakest link so the
level of engineering or technology in India
can become excellent only if all the three
levels we are strong in and the chain is strong.
Now let us see, as a part of the status in
India what are the various industries, research
laboratories and academic institutes which
are participating in development of technology.
So in industries we have Bharath Electronics
limited Bangalore, Continental Devices India
Limited CDIL New Delhi, we have semiconductor
complex Chandigarh, then we have Indian Telephone
Industries that is ITI Bangalore.
So the research laboratories are Solid State
Physics Laboratory in New Delhi, the Central
Electronic Engineering Research Institute
CEERI in Pilani Rajasthan, then there are
academic institutes which are participating
in the development, which have small laboratories
but which have strong teaching programs in
this area, these are the Indian Institutes
of Technology and the Indian Institute of
Science, Bangalore. One of the purposes of
developing the video lectures is to have more
colleges in the country involved in teaching
of this technology which is advancing rapidly.
Now in the end of this lecture I would like
to tell you what is the way the remaining
lectures will be conducted. So, for the remaining
lectures we will have 20 minutes of lecturing
followed by about 8 minutes of discussion,
and then we again have 20 minutes of lecturing
followed by about 8 minutes of discussion.
This is an approximate idea of the division
of the time of 56 minutes into lectures and
discussion which involve questions and answers.
Then problems and solutions are provided in
a separate CD, some problems will be solved
in class, but some will be given to you and
you will have to solve them yourself, these
are provided in separate sheet. Then also
have a separate CD for discussion of select
problems and their solutions. And finally
what are reference materials?. Apart from
listening to these video lectures you could
refer to text books which are available.
There are many textbooks such as textbooks
by M. S. Thyagi of IIT Kanpur, on Introduction
to Semiconductor Material and Devices, and
then Ben Streetman is a book on semiconductor
electronic devices. Now apart from this I
would also urge you to use the internet for
understanding various concepts and I will
demonstrate to you in the remaining lectures
how internet can be used.
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