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VLSI Design : Question Paper May 2014 - Electronics & Telecomm. (Semester 6) | Mumbai University (MU)

## VLSI Design - May 2014

### Electronics & Telecomm. (Semester 6)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.
1 (a) The segregation co-efficient of oxygen is 0.25. Find the concentration of oxygen in the silicon ingot at a fraction solidified of 0.3. The concentration of oxygen in the silicon at the top of the crystal is 12.5x1017 atoms/cm3 at fraction solidified of 0.1.(5 marks) 1 (b) Draw the schematic diagram and stick diagram of NMOS depletion inverter (5 marks) 1 (c) Explain what is pass transistor logic ? Calculate the op voltage of the circuit if VDD = 5V and VTH = 1.5V(5 marks) 1 (d) Define the threshold voltage with equation and explain the body effect. (5 marks) 1 (e) State the difference between diffusion and ion implementation.(5 marks) 2 (a) With neat cross sectional diagram explain the process of CMOS fabrication using p-well process. Thus give the number of masks required.(10 marks) 2 (b) Consider an Aluminum silicon MOS structure with the following parameters:
ND=2.5x1014 /cm3
QOX=1010 qc/cm3
TOX=650 Ao
?ms= -0.35V
Ni=1.45 x 1010/cm3
(10 marks)
3 (a) Draw the circuit diagram of two input NAND gate using CMOS. Draw its stick diagram & layout using ? based design rules.(10 marks) 3 (b) State all types of inverter with their merits and demerits. Give their applications.(10 marks) 4 (a) Determine pull up to pull down ratio (Zpu/Zpd) for an NMOS inverter when driven by another inverter.(10 marks) 4 (b) Explain latch up in CMOS in detail. What are the remedies to avoid latch-up.(10 marks) 5 (a) Implement the following using CMOS logic function: F= X. (Y + Z) + XW Design the circuit and draw the stick diagram using Euler?s method. (10 marks) 5 (b) Design 4: 1 multiplexer using MOS transmission logic. Draw the stick diagram of the same.(10 marks) 6 (a) Compare both the scaling methods. Show analytically how power dissipation, maximum operating frequency, current density and saturation current scale in terms of scaling factors.(10 marks) 6 (b) Write the Verilog code for 2 input NAND gate using the module of NAND gate design SR latch and write the Switch level Verilog code for the same.(10 marks) 7 (a) Short channel effect in MOSFET?s.(7 marks) 7 (b) Compare buried and butting contacts.(7 marks) 7 (c) Semicustom and full custom design(7 marks)

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