VLSI Design - May 2012

Electronics Engineering (Semester 7)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1(a) Compare semi-custom and full-custom design.(5 marks) 1(b) Compare buried and butting contact.(5 marks) 1(c) Compare ion Implantation and Diffusion.(5 marks) 1(d) Draw stick diagram for CMOS inverter.(5 marks) 2(a) Explain twin tub process in detail.(10 marks) 2(b) What is latch-up in CMOS and How to prevent.(10 marks) 3(a) Calculate the threshold voltage V_T0 at V_SB =0.5 V. For a polyslicon gate n-channel MOS transistor, with the following parameters.
T_OX =500A^o , N_A=10¹⁶ cm^-3
N_D=2x10²⁰ cm^-3
Nox=4x10¹⁰ cm^-2,br> (10 marks) 3(b) Explain short channel effect in MOSFET.(10 marks) 4(a) Draw the stick diagram and mask layout using ? based design rules for a depletion load NMOS inverter with pullup to pulldown ratio as 4:1. (10 marks) 4(b) Explain various sources of power dissipation in digital CMOS circuits. (10 marks) 5(a) Explain constant voltage and constant field scaling in detail with their merits. (10 marks) 5(b) Write Verilog code fr 1 bit full adder and use it to design a 4 bit full adder. (10 marks) 6(a) Implement the following Boolean function In CMOS logic.
Y=CMOS logic/C(D+E)+A.B. (10 marks) 6(b) What is the need for design rules? Justify.(10 marks)

Write short notes on:

7(a) Wafer processing:(7 marks) 7(b) MOS capacitor:(7 marks) 7(c) VLSI design flow:(7 marks)