Semiconductor Basics (outline of the course and some basic terminologies)

Here, I will give the detailed information about semiconductor from very basic to a advanced level.

I will try to provide some interview questions that has been asked in different semiconductor companies.









ok, so here we go,

So, What you  need to know if you want to go into a semiconductor industries (here, my focus is on VLSI)

You should have  clear concepts of some subjects as I have disscussed below. (You can skip the advanced part if  you are a fresher).

1. Analog electronics

:  Capacitor, Diode,  BJT, FET , MOSFET, Oscillator, Op-amp, 555 Timer

2. Digital electronics

:logic minimization, k-map,Sop,Pos,AOI, Adder, Subtractor, combinational, and sequential circuits, state machine, counters, registers and its types, conversion of flip-flops  etc....

3. Physics of semiconductor

: Good understanding of semiconductor and its types

:Good understanding of mos capacitor with band diagram

4.  Basic VLSI

mosfet, cmos, voltage and transfer characteristics of cmos, Different regions of operation of cmos, stick diagram etc.

5. Advance VLSI

a. static time analysis

: Setup time and hold time

: time exceptions

:false path, multi-cycle path etc.

b. About different  physical cells

c. latch-up issue and its solution

d. Antenna effect and its  solution

e. PnR flow

f. Different updated technologies used by the semiconductor companies.

So, here we go one by one:

Before starting semiconductor we should have some basic knowledge about signal , voltage, current etc.

signal contain information about a variety of things and activities in our physical world.like Information about the weather is contained in signals that contains the air temp. , pressure, wind speed etc. 

Now the question is  how to extract the information from that particular signal?

> extract the information from the signal one needs to process the signal(means signal will go through some process) in some  predetermined manner.

For this to be possible signal must be converted into electrical signal, e.g voltage and current

This process accomplished by a device known  as Transducer.

>> Don't confused with the term signal processing its just like, if you need oil from coconut then to extract the oil, coconut must go through some process . 

Types of signal

1. Analog

2. Digital

1. Analog signal: It derived from the fact that such signal is analogous to the physical signal that it represent.

It can take any value at any time within the given limit.

e.g, The amplitude of an analog signal exhibits a continuous variation over its range of activity.

* An analog signal may be continuous or discrete in nature

--> All continuous signal is analog in nature but not all analog signal is continuous in nature.

>> If time is discretized (i.e the independent variable is discretized) but not  the amplitude (i.e dependent variable is not discretize) it's still an analog signal.

To get the clear view just see the fig1.1b and fig1.1c given below.

>>Now you may have doubt that how amplitude is dependent and time is independent?

 See the fig carefully, the amplitude is changing w.r.t time so, it's depends on time.

at time t1 temprature is 1c at t2 temprature is 2c and so on. so, here the temp. is increasing with increase of time. hence, we can say that amplitude (here Temp.) depends on time. while we can clearly obseve that time is independent variable.

>> Guys do not get confuse with the term discretize, it's just a specific value of signal at a specific time instant. It can be obtained by sampling a continuous signal. in fig1.1a and fig1.1b and  the samples are taken at various time instant these instant may be regular or irregular.

fig1.1a

fig1.1b

When I will discuss about digital signal in detail then you will get more clear idea.

2. Digital signal: It's a representation of signal as sequence of numbers, each numbers represents the signal magnitude at an instant of time, the resulting signal is called as Digital signal

Here we will discuss some basic terminology like current, voltage etc.


Current:   Current is the flow of electrons per unit time.
It's measure in Ampere(A)

one Ampere = one coulomb/1sec
i.e, one ampere current is the flow of one coulomb  electrons per sec.

one coulomb =6.242*10^18 electrons or protrons(approx.)
So, if rating of the device is 1A it means 6.242*10^18 electrons can flow per sec.
If the rating is 1.5A then (6.242*10^18)*1.5=9.63electrons can flow per sec.

Note>> If too many electrons will pass through the circuit then circuit may burn out.

Now, you may have doubt that how circuit will burn out?
Ok, let me explain
Flowing of electrons through a circuit is just like flowing of water through a pipe. Pipe has its own capacity to handle the water pressure if more water will flow per unit time then it will exert more pressure and pipe may burst out. Similarly if too many electrons will flow (beyond the circuit capacity) the circuit may burn out.

Types of current:
a) A.C 
b)D.C

❊✽ Have you ever thought that  why AC gives a shock not a DC?🙎😖😖
>> Actually our body behaves somewhat like a capacitor and property of capacitor is to block DC current and allow AC current to pass. so, our body resist to DC but a AC can pass through our body very easily and hence, AC gives a shock not a DC.😐😃But a heavy DC current can also give a shock.

⭐🔯 Many appliances uses both AC as well as DC.
EX-> Whashing machine>> It uses AC for the induction motor and DC for control circuit board.

Voltage: Voltage is a difference in electrical potential energy per unit of charge between two points.
In a simple way, voltage behaves like a pushing force which  push the electrons to start moving around in a certain direction which creates an electrical current. (Actually in a conductor there are free electrons but all are moving in a zigzag manner cancels out each others effect but when we give voltage then those electrons start moving in a certain direction and speed and no of electrons passing per unit area per unit second depend on the potential energy given to those electrons.)

Resistor:- Resistor controls the flow of current as it slows down the electrons.
EX->If an LED rated at 25mA , 3.3vDC and battery rating is 9v. If you connect the LED to this battery then LED gets burn out because of too much current.
so, to stop the LED from burning out  we need to connect the 270ohm resistor.

⚛️🔯 Guys have you ever noticed which of these voltage or current gives a shock??😮

>> Actually current gives a shock. As current is nothing but flow of electrons per unit time so if more no of electrons with much intensity will flow through the body we get more shock.
Voltage only gives potential to those electrons to accelerate but flow of electrons i.e, current depend on the path resistance. If resistance is more the current will be less and hence, you feel less shock, but if resistance is less then for the same applied voltage the current will be more and you feel more shock.
lets take one example >> if I will try to hit some body with a ball, so I will through the ball with certain potential and ball will hit that body with some intensity but imagine there is wall in between then ball unable to cross the wall and this time that person will not get any kind of shock due to that ball.
Imagine the ball as electrons, force applied by me is voltage and the wall in between as an infinite resistor.