VLSI Questions and Answers for Experienced people focuses on “Limitations of Scaling -2”.
1. Maximum transit time occurs when the size of the transistor is
A. minimum
B. maximum
C. does not depend on size
D. double
Answer: A
Clarification: Maximum transit time occurs when the size of the transistor is minimum when Va is approximately 0.
2. The spacing of interconnect is scaled by
A. α
B. 1/α
C. α2
D. 1/α2
Answer: B
Clarification: Spacing of interconnect, width and thickness are scaled by 1/α as they are linear dimensions.
3. Cross section area is scaled by
A. α
B. 1/α
C. α2
D. 1/α2
Answer: D
Clarification: Cross section area is scaled by 1/α2 as area is the product of length and width which are scaled by 1/α.
4. The decrease in device dimension ______ the die size.
A. increases
B. decreases
C. does not affect
D. decreases and then increases
Answer: A
Clarification: The decrease in device dimension increases the die size and also the levels of integration.
5. The reduction in die size reduces
A. R
B. d
C. L
D. W
Answer: A
Clarification: The reduction in die size also reduces R and C. Die size depends on both resistor and capacitor.
6. The propogation delay along the optical fiber interconnect can be given as
A. n/Lx
B. nL/c
C. c/nL
D. nc/L
Answer: B
Clarification: The propogation delay along the optical fiber interconnect can be given as nL/c where n is the refractive index, L is the length of the fiber and c is the speed of light.
7. The breakdown voltage can be reduced by _____ electric field strength.
A. increasing
B. decreasing
C. does not depend
D. exponentially decreasing
Answer: A
Clarification: The increase in electric field strength lowers the breakdown voltages. Electric field is inversely proportional to the voltage.
8. Greater the switching speed _____ is the more.
A. low
B. more
C. all of the mentioned
D. none of the mentioned
Answer: B
Clarification: Increase in switching speed increases the noise problems. Switching speed is the rate a which the logic level varies.
9. Substrate concentration is scaled by
A. α
B. 1/α
C. α2
D. 1/α2
Answer: A
Clarification: Substrate concentration Nb which gives the doping level of substrate is scaled by α.
10. The increase in operating frequency results in ______ in cross-talk noise.
A. increase
B. decrease
C. no change
D. doubling
Answer: A
Clarification: The increase in operating frequency and reduction in rise time tr results in the increase of cross-talk noise.
11. Flicker noise is scaled by
A. 1/α2
B. α2/β2
C. 1/β2
D. β2/α2
Answer: B
Clarification: Flicker noise occurs due to fluctuations of carriers trapped in the channel by surface states. It is scaled by α2/β2.
12. Scaling affects _____ generated noise.
A. internally
B. externally
C. internally and externally
D. does not generate
Answer: C
Clarification: Scaling affects both internally and externally generated noise and this degrades both the production yeild and the reliability of high density chip layouts.