This presentation will enable the aspirants to understand the evolution of VLSI technology from vaccum tubes to VLSI.

1. VLSI Technology Evolution
Mr. A. B. Shinde
Assistant Professor,
Electronics Engineering, PVPIT, Budhgaon

2. Before we start… Answer this
 What is VLSI ?
 If your answers is other than…
V L S I = Very Large Scale Integration
then you are most welcome…
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3. Vacuum Tubes
Gas-filled Tube
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4. Early Computers
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Courtesy:
Intel Corporation

5. Vacuum Tubes…
 A gas-filled tube is essentially a vacuum tube having a small
amount of some inert gas at low pressure.
 Gas-filled tubes have two types:
 Cold-cathode type and Hot-cathode type.
Cold-cathode Hot-cathode
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6. Cold-Cathode Gas Diode
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7. Hot-Cathode Gas Diode
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8. Thyratron (Triode)
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9. Atomic Structure
Number of Electrons in orbit = 2n2Neils Bohr
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10. Energy Bands
 larger the orbit of an electron, the greater is its energy and higher is the
energy level.
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11. Energy Bands in Solids
 Valence band: The range of energies (i.e.
band) possessed by valence electrons is
known as valence band.
 Conduction band: The range of energies
(i.e. band) possessed by conduction band
electrons is known as conduction band.
 Forbidden energy gap: The separation
between conduction band and valence band
on the energy level diagram is known as
forbidden energy gap.
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12. Classification of Solids & Energy Bands
Insulators Conductors Semicondutors
1 eV is the amount of energy acquired by an electron when it is
accelerated through a potential difference of 1 V.
energy gap is ≈ 15 eV Bands are overlapped energy gap is ≈ 1 eV
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13. Semiconductors
 Semiconductor has :
 almost full valence band
 almost empty conduction band
 small energy gap (≈ 1 eV) between
valence and conduction bands.
Silicon atom
Germanium atom
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14. Commonly Used Semiconductors
Silicon Germanium
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15. Energy Band Description
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16. Effect of Temperature on Semiconductors
 At absolute zero: All the electrons are tightly held by the
semiconductor atoms. The valence electrons are engaged in co-valent
bonding.
 At this temperature, the co-valent bonds are very strong and there are
no free electrons.
 Hence, the semiconductor crystal behaves as a perfect insulator
 Above absolute zero: Some of the covalent bonds in the
semiconductor break due to the thermal energy supplied.
 The breaking of bonds sets those electrons free therefore few free
electrons exist in the semiconductor.
 The resistance of a semiconductor decreases with the rise in
temperature
 It has negative temperature coefficient of resistance.
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17. Types of semiconductor
 Intrinsic Semiconductor:
 A semiconductor in an extremely pure form is known as an intrinsic
semiconductor
 It has little current conduction capability at room temperature
 Extrinsic Semiconductor:
 The pure semiconductor must be altered so as to significantly increase
its conducting properties.
 This is achieved by adding a small amount of suitable impurity to a
semiconductor.
 The semiconductor with impurity is called as extrinsic semiconductor.
 Further two types:
n-type & p-type
(If Impurity is from 5th column) (If Impurity is from 3rd column)
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18. n-type Semiconductor
 When a small amount of pentavalent impurity is added to a pure
semiconductor, it is known as n-type semiconductor
Pentavalent impurities:
arsenic (At. No. 33) &
antimony (At. No. 51).
Such impurities which produce
n-type semiconductor are
known as donor impurities
because they donate or provide
free electrons
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19. p-type Semiconductor
 When a small amount of trivalent impurity is added to a pure
semiconductor, it is called p-type semiconductor.
Trivalent impurities:
gallium (At. No. 31) &
indium (At. No. 49).
Such impurities which produce p-
type semiconductor are known as
acceptor impurities because the
holes created can accept the
electrons.
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20. pn junction diode
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21. Transistor
 A transistor consists of two pn junctions formed by sandwiching either
p-type or n-type semiconductor between a pair of opposite types.
npn transistor
symbol 2 diode analogy
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22. Transistor
First transistor
1947: Bardeen, Brattain and Schokley at Bell laboratories built the first
working point contact transistor (Nobel Prize in Physics in 1956)
The field of electronics shifted from vacuum tubes to solid-state
devices
Courtesy:
Texas Instruments
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23. Transistors
 To manufacture larger circuits the number of transistors required
will be more…ultimately large board space was required
 Human mind never sits idle
 They was continuously thinking
“can we bring few transistors together…?
 And the answer found in 1958… Yes
IC was invented …!!!
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24. Integrated Circuit
 An integrated circuit (IC) is one in which circuit components such as
transistors, diodes, resistors, capacitors etc. are mounted on small
piece of semiconductor i.e. first IC was developed.
 On IC we can easily mount large number of components together.
 IC Inventers: Jack Kilby & Robert Noyce
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25. Integrated Circuit
First integrated circuit
Courtesy:
Texas Instruments
As 1958: Jack Kilby built the first integrated circuit flip flop at Texas
Instruments (Nobel Prize in Physics in 2000)
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26. Integrated Circuit
 Cross Section: Internal View
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27. Integrated Circuit Growth
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28. Integrated Circuit
Advantages :
1. Increased reliability due to lesser number of connections.
2. Extremely small size
3. Lesser weight and space requirement
4. Low power requirements.
5. Greater ability to operate at extreme values of temperature.
6. Low cost
7. The circuit lay out is greatly simplified
Disadvantages :
1. If any component in an IC goes out of order, the whole IC has to be replaced.
2. In an IC, it is neither convenient nor economical to fabricate capacitances
exceeding 30 pF.
3. It is not possible to fabricate inductors and transformers
4. It is not possible to produce high power ICs (greater than 10 W).
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29. Integrated Circuit
 But… remember “Human mind never sits idle …”
 Continuous research goes on in the direction…
Can we increase the number of transistors…?
Answer is … Yes…!!!
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30. Integration Technology…
Year No. of Transistors
SSI 1964 1 to 20
MSI 1968 20 to 100
LSI 1971 100 to 1,000
VLSI 1980 1,000 to 10,000
ULSI 1984 10,000 and more
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31. VLSI Technology
 Design Stages: Abstraction Levels
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32. VLSI Technology
 Programming Languages
 VHDL
 Verilog
 Implementation Technology
 FPGA
 CPLD
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33. VHDL
 V = VHSIC
 H = Hardware
 D = Description
 L = Language
 VHSIC = Very High Speed Integrated Circuit
 We can describe any hardware (digital logic) using this language
c<= a and b;
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34. Implementation Technology
 FPGA = Field Programmable Gate Array
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35. Implementation Technology
 CPLD = Complex Programmable Logic Devices
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36. VLSI
Design
Flow
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37. VLSI Technology Evolution37
This presentation is published only for educational purpose
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