This set of VLSI Questions and Answers for Freshers focuses on “Design Rules and Layout-2”.
1. Diffusion and polysilicon layers are connected together using __________
a) butting contact
b) buried contact
c) separate contact
d) cannot be connected
View Answer
Explanation: Diffusion and polysilicon layer are joined together using butting contact. In butting contact the two layers are joined or binded together.
2. Which is a more complex process?
a) buried contact
b) butting contact
c) buried & butting contact
d) none of the mentioned
View Answer
Explanation: Butting contact is a complex process whereas buried contact is simple process because butting contact should be done more carefully to serve well and be strong.
3. Which contact cut occupies smaller area?
a) buried contact
b) butting contact
c) buried & butting contact
d) none of the mentioned
View Answer
Explanation: Buried contact occupies smaller area than butting contact as in buried contacts one layer will be completely within or almost within the another layer.
4. Isolation layer between two metal layers must be thinner.
a) true
b) false
View Answer
Explanation: Isolation layer between two metal layers should be thicker. Metal to metal separation is large and is brought about mainly by difficulties in defining metal edges accurately.
5. The oxide layer below the first metal layer is deposited using __________
a) diffusion method
b) chemical vapour deposition
c) solid deposition
d) scattering method
View Answer
Explanation: The oxide layer below the first metal layer is depostied using chemical vapour deposition method. This is a chemical process used to produce high quality high performance solid materials.
6. Which layer is used for power and signal lines?
a) metal
b) polysilicon
c) n-diffusion
d) p-diffusion
View Answer
Explanation: Metal layers are used for power and signal lines as metals has good thermal and electrical conductivity.
7. Minimum feature size for thick oxide is?
a) 2λ
b) 3λ
c) 4λ
d) λ
View Answer
Explanation: The minimum feature size for thick oxide is 3λ and minimum separation between thin oxide regions is also 3λ.
8. Hatching is compatible with __________
a) monochrome encoding
b) bicode encoding
c) tricode encoding
d) not compatible with any encoding
View Answer
Explanation: Hatching is compatible with monochrome encoding and also may be added to color mask coding. It is designed using closely spaced lines or sticks.
9. Minimum n-well width should be ____________ micro meter.
a) 2
b) 3
c) 4
d) 6
View Answer
Explanation: The minimum width of n-well is 3 micro meter because n-well should be with little thickness and in it p-type devices are formed.
10. The minimum spacing between two n-well is _____ micro meter.
a) 4
b) 5
c) 8
d) 8.5
View Answer
Explanation: The minimum spacing between two n-well is 8.5 micro meter according to the lambda based design rules.
11. Which can bring about variations in threshold voltage?
a) oxide thickness
b) ion implantation
c) poly variations
d) all of the mentioned
View Answer
Explanation: One of the problems in the manufacture using design rule is that variation in threshold voltage occurs. And this is caused by oxide thickness, ion implantation and poly variations.
12. What are the advantages of design rules?
a) durable
b) scalable
c) portable
d) all of the mentioned
View Answer
Explanation: Some of the advantages of generalised design rules are those are durable, scalable, portable, increases designer efficiency and automatic translation to final layout can be done.
13. Minimum diffusion space is __________
a) 2λ
b) 3λ
c) 4λ
d) λ
View Answer
Explanation: Minimum diffusion space is 3λ to avoid the possibility of their associated regions overlapping and conducting current.
14. Contact cuts should be ____ apart.
a) 2λ
b) 3λ
c) 4λ
d) λ
View Answer
Explanation: Two contact cuts should be 2λ apart to prevent holes from merging.
Sanfoundry Global Education & Learning Series – VLSI.
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