VLSI Propagation Delay MCQ Quiz – Objective Question with Answer for VLSI Propagation Delay

21. Which layer has high capacitance value?

A. metal
B. diffusion
C. silicide
D. polysilicon

Answer: B

Diffusion or active layer has a high capacitance value due to which it has low or moderate IR drop.

 

22. Which layer has a high resistance value?

A. polysilicon
B. silicide
C. diffusion
D. metal

Answer: A

The polysilicon layer has a high resistance value and due to this, it has a high IR drop.

 

23. While measuring the output load capacitance Cgs, n and Cgs, p is not considered. Why?

A. Because Cgs, n and Cgs, p are the capacitances at the input nodes
B. Because Cgs, n and Cgs, p does not exist during the operation of CMOS inverter
C. Because Cgs, n and Cgs, p are storing opposite charges and cancel out each other during the calculation of load capacitance
D. None of the mentioned

Answer: A

Cgs, n and Cgs, p are the gate to source capacitances of nMOS and pMOS transistors in CMOS inverter. They are measured at input node. Therefore they are not considered for the calculation of load capacitance.

 

24. During the calculation of load capacitance of a 1st stage CMOS inverter, the input node capacitances, Cgs, n and Cgs, p of the 2nd stage CMOS inverter are also considered.

A. True
B. False

Answer: B

Instead, thin oxide capacitance over the gate area is used for calculation.

 

25. The resistance of the uniform slab of the conducting material is?

A. Linear(proportional) with length
B. Inversely proportional to the thickness
C. Inversely proportional to the width
D. All of the mentioned

Answer: D

The resistance of a uniform slab of conducting material can be expressed as
R = (ρ.l)/(t.w).

 

26. The sheet resistance of the conducting material is?

A. RS = resistivity/length
B. RS = resistivity/width
C. RS = resistivity/thickness
D. None of the mentioned

Answer: C

The sheet resistance of the conducting material is given by RS = resistivity/thickness.

 

27. In CMOS manufacturing process Sheet resistance is used instead of resistivity because _______________

A. Resistivity is the same for all doped regions
B. Resistivity and thickness are characteristics that cannot be controlled by the circuit designer, and it is expressed as the single sheet resistance parameter
C. Sheet resistance is a dimensionless quantity
D. Sheet resistance is equal to resistivity

Answer: B

It is convenient to use Sheet resistance instead of resistivity because Resistivity and thickness are characteristics that cannot be controlled by the circuit designer, and it is expressed as the single sheet resistance parameter.

 

28. Compute the sheet resistance of a 0.17 µm thick Cu wire if the resistivity of Cu wire is 1.7 µΩ-cm.

A. 0.01 Ω/square
B. 0.001 Ω/square
C. 10.0 Ω/square
D. 0.10 Ω/square

Answer: D

Sheet resistance of copper is = (1.7*10-8)/(0.17*10-6)=0.10 Ω/square.

 

29. For semiconductors doped through diffusion or through surface peaked ion implantation we derive the sheet resistance as ___________

A. Average resistivity of semiconductor/thickness
B. Resistivity/thickness
C. Conductivity/thickness
D. None of the mentioned

Answer: A

For semiconductors doped through diffusion or through surface peaked ion implantation we derive the sheet resistance using the average resistivity of the material.

 

30. Sheet resistance of a semiconductor is ___________

A. Inherent property of the material
B. Function of the thickness of the material
C. Also called Specific Resistance
D. All of the mentioned

Answer: B

Resistivity is the inherent property of any conducting material. It is also called Specific Resistance. Sheet resistance is a function of thickness as resistivity for material is fixed.

Scroll to Top