Introduction to MOS MCQ Quiz – Objective Question with Answer for Introduction to MOS MCQ

61. What is Lithography?

A. Process used to transfer a pattern to a layer on the chip
B. Process used to develop an oxidation layer on the chip
C. Process used to develop a metal layer on the chip
D. Process used to produce the chip

Answer: A

Lithography is the process used to develop a pattern to a layer on the chip.

62. Silicon oxide is patterned on a substrate using ____________

A. Physical lithography
B. Photolithography
C. Chemical lithography
D. Mechanical lithography

Answer: B

Silicon oxide is patterned on a substrate using Photolithography.

63. Positive photo resists are used more than negative photo resists because ___________

A. Negative photoresists are more sensitive to light, but their photolithographic resolution is not as high as that of the positive photoresists
B. Positive photoresists are more sensitive to light, but their photolithographic resolution is not as high as that of the negative photoresists
C. Negative photoresists are less sensitive to light
D. Positive photoresists are less sensitive to light

Answer: A

Negative photoresists are more sensitive to light, but their photolithographic resolution is not as high as that of positive photoresists. Therefore, negative photoresists are used less commonly in the manufacturing of high-density integrated circuits.

64. The ______ is used to reduce the resistivity of polysilicon.

A. Photoresist
B. Etching
C. Doping impurities
D. None of the mentioned

Answer: C

The resistivity of polysilicon is reduced by Doping impurities.

65. The isolated active areas are created by a technique known as ___________

A. Etched field-oxide isolation
B. Local Oxidation of Silicon
C. Etched field-oxide isolation or Local Oxidation of Silicon
D. None of the mentioned

Answer: C

To create isolated active areas both techniques can be used. Among them, Local Oxidation of Silicon(LOCOS) is the most efficient.

66. The chemical used for shielding the active areas to achieve selective oxide growth is?

A. Silver Nitride
B. Silicon Nitride
C. Hydrofluoric acid
D. Polysilicon

Answer: B

Selective oxide growth is achieved by shielding the active areas. Silicon nitride (Si3N4) is used for shielding the active areas during oxidation, which effectively inhibits oxide growth.

67. The dopants are introduced in the active areas of silicon by using which process?

A. Diffusion process
B. Ion Implantation process
C. Chemical Vapour Deposition
D. Either Diffusion or Ion Implantation Process

Answer: D

Two ways to add dopants are diffusion and ion implantation.

68. To grow the polysilicon gate layer, which of the following chemical is used for chemical vapor deposition?

A. Silicon Nitride(Si3N4)
B. Silane gas(SiH4)
C. Silicon oxide
D. None of the mentioned

Answer: B

Silicon Wafer is placed in a reactor with silane gas (SiH4), and they are heated again to grow the polysilicon layer by chemical vapor deposition.

69. The process by which Aluminium is grown over the entire wafer, also filling the contact cuts is?

A. Sputtering
B. Chemical vapor deposition
C. Epitaxial growth
D. Ion Implantation

Answer: A

Aluminum is sputtered over the entire wafer, it also fills the contact cuts.

70. Chemical Mechanical Polishing is used to ___________

A. Remove silicon oxide
B. Remove silicon nitride and pad oxide
C. Remove the polysilicon gate layer
D. Reduce the size of the layout

Answer: B

The pad oxide and nitride are removed using a Chemical Mechanical Polishing (CMP) step.

71. What is Piranha Solution?

A. It is a 3:1 to 5:1 mix of nitric acid and hydrogen peroxide that is used to develop the oxide layer on a silicon substrate

B. It is a 3:1 to 5:1 mix of sulphuric acid and hydrofluoric acid that is used to clean silicon wafers removing organic and metal contaminants or photoresists after metal patterning

C. It is a 3:1 to 5:1 mix of sulphuric acid and hydrogen peroxide that is used to grow the oxide layer on the silicon

D. It is a 3:1 to 5:1 mix of sulphuric acid and hydrogen peroxide that is used to clean wafers of organic and metal contaminants or photoresists after metal patterning

Answer: D

Piranha solution is a 3:1 to 5:1 mix of sulfuric acid and hydrogen peroxide that is used to clean silicon wafers of metal and organic contaminants or photo-resist after metal patterning.

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