VLSI Questions and Answers – nMOS Fabrication

«
»

This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “nMOS Fabrication”.

1. nMOS fabrication process is carried out in
a) thin wafer of a single crystal
b) thin wafer of multiple crystals
c) thick wafer of a single crystal
d) thick wafer of multiple crystals
View Answer

Answer: a
Explanation: nMOS fabrication process is carried out in thin wafer of a single crystal with high purity.
advertisement

2. _____ impurities are added to the wafer of the crystal
a) n impurities
b) p impurities
c) siicon
d) crystal
View Answer

Answer: b
Explanation: p impurities are introduced as the crystal is grown. This increases the hole concentration in the device.

3. What kind of substrate is provided above the barrier to dopants?
a) insulating
b) conducting
c) silicon
d) semi conducting
View Answer

Answer: a
Explanation: Above a layer of silicon dioxide which acts as barrier, insulating layer is provided upon which other layers may be deposited and patterned.

4. The photoresist layer is exposed to
a) visible light
b) ultraviolet light
c) infra red light
d) LED
View Answer

Answer: b
Explanation: The photoresist layer is exposed to ultraviolet light to mark the regions where diffusion is to take place.

5. In nMOS device, gate material could be
a) silicon
b) polysilicon
c) boron
d) phosporus
View Answer

Answer: b
Explanation: In nMOS device, the gate material could be metal or polysilicon. This polysilicon layer has heavily doped polysilicon deposited by CVD.
advertisement

6. The commonly used bulk substrate in nMOS fabrication is
a) silicon crystal
b) silicon-on-sapphire
c) phosporus
d) silicon-di-oxide
View Answer

Answer: c
Explanation: In nMOS fabrication, the bulk substrate used can be either bulk silicon or silicon-on-sapphire.

7. In nMOS fabrication, etching is done using
a) plasma
b) hydrochloric acid
c) sulphuric acid
d) sodium chloride
View Answer

Answer: a
Explanation: In nMOS fabrication, etching is done using hydroflouric acid or plasma. Etching is a process used to remove layers from the surface.

8. Heavily doped polysilicon is deposited using
a) chemical vapour decomposition
b) chemical vapour deposition
c) chemical deposition
d) dry deposition
View Answer

Answer: b
Explanation: The polysilicon layer consists of heavily doped polysilicon deposited by chemical vapour deposition.

9. In diffusion process, ______ impurity is desired
a) n type
b) p type
View Answer

Answer: a
Explanation: Diffusion is carried out by heating the wafer to high temperature and passing a gas containing the desired ntype impurity.
advertisement

10. Contact cuts are made in
a) source
b) drain
c) metal layer
d) diffusion layer
View Answer

Answer: a
Explanation: Contact cuts are made in the desired polysilicon area, source and gate. COntact cuts are those places where connection has to be made.

11. Interconnection pattern is made on
a) polysilicon layer
b) silicon-di-oxide layer
c) metal layer
d) diffusion layer
View Answer

Answer: c
Explanation: The metal layer is masked and etched to form interconnection pattern. The metal layer was formed using aluminium deposited over the formed surface.

12. SIlicon-di-oxide is a good insulator.
a) true
b) false
View Answer

Answer: a
Explanation: SIlicon-di-oxide is a very good insulator so a very thin layer is required in the fabrication of MOS transistor.

13. _______ is used to suppress unwanted conduction
a) phosporus
b) boron
c) silicon
d) oxygen
View Answer

Answer: b
Explanation: Boron is used to suppress the unwanted conduction between transistor sites. It is implanted in the exposed regions.
advertisement

14. Which is used for the interconnection?
a) boron
b) oxygen
c) aluminium
d) silicon
View Answer

Answer: c
Explanation: Aluminium is the suitable material used for the circuit interconnection or connecting two layers.

Sanfoundry Global Education & Learning Series – VLSI.
To practice all areas of VLSI, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
advertisement
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn