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86802 Pages: 2

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SIXTH SEMESTER B.TECH DEGREE EXAMINATION, APRIL 2018

Course Code: EC304
Course Name: VLSI (EC)

PART A
Answer any two full questions, each carries 15 marks.
Illustrate with diagram the principle of crystal growth by Czochralzki method.

What is photolithography? With diagram illustrate the steps involved in
photolithography process.

A SiO, layer is grown by wet oxidation at 1000°C for 40 minutes followed by
dry oxidation for 1 hour at 1200°C. Determine the thickness of the oxide layer
formed. For wet oxidation at 1000°C, B=0.29 , B/A=1.27 and for dry oxidation
at 1200°C , B= 0.045, B/A= 1.120 , t = 0.027

What is Deal Grove model of oxidation? What are linear and parabolic rate
coefficients with reference to oxidation process?

Explain the principle of molecular beam epitaxy, with schematic diagram of an
MBE system. What are its advantages and disadvantages?

A silicon crystal is to be grown by Czochralski process and is to contain 5105
boron atoms/cm*. Given the segregation constant ko for Boron in silicon is 0.8.
Atomic weight of boron equals 10.81g/mole, density of silicon 2.22g/em* and
Avogadro number is 6.023» 1023 atoms/mole. (a) Determine the initial
concentration of Boron in the melt to produce the required doping density. (b) If
the initial amount of silicon in the crucible is 20kg, how many grams of Boron
should be added to obtain the same doping?

With schematic diagram and chemical reactions involved, illustrate wet and dry
oxidation processes.

Determine the ratio of Silicon consumed to the thickness of grown 510) layer
over silicon wafer. If SiO2 layer of 0.2 ‏سر‎ is to be grown, what would be the
thickness of used up Silicon. Molecular weight of SiO. = 60.08g.mole, density
of SiO2=2.2g/cm3, atomic weight of Si=20.09 and density of Si= 2.33 ‏“ماع‎
‎What are the different methods of fabricating capacitors in integrated circuits?
Illustrate with diagrams.

PART B
Answer any two full questions, each carries 15 marks.
What are the different types of power dissipation in a CMOS inverter? Derive
expression for the total power dissipation.
Realise a THE FUNCTION f= AB’C+A C(DE+A’B) using standard CMOS
logic.

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Duration: 3 Hours

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