Question

Direction: Question consists of two statements, one labeled as the 'Assertion (A)' and the other as 'Reason (R)'. Examine these two statements carefully and select the answer to this question using the codes given below:

Assertion (A): Si is mainly used for making ICs and not Ge.

Reason (R): In Si, SiO₂ layer which acts as an insulator can be formed for isolation purposes. The corresponding oxide layer cannot be formed in Ge.

1. Both A and R are individually true and R is the correct explanation of A
2. Both A and R are individually true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true

Answer 1

Correct Answer - Option 1 : Both A and R are individually true and R is the correct explanation of A

Silicon is preferred over Germanium because of the following reasons:

1. The leakage current or collection cut-off current (I_co), at room temp is lower than Germanium.

2. Variation in I_co with temperature is less in silicon.

3. The structure of silicon crystal can handle higher temperatures compared to Ge.

4. Peak inverse voltage rating of the Silicon diode is greater than the Germanium diode.

5. Silicon is less expensive due to the greater abundance of elements. The major raw material for si wafer fabrication is sand & there is lots of sand available in nature.

6. For Isolation purposes SiO₂ can be formed only with silicon & this is the major advantage of using Silicon for IC manufacturing.

Conclusion:

Since isolation is the primary requirement in the IC manufacturing process, SiO₂ can only be formed with silicon and therefore Silicon is preferred for IC manufacturing.

# Why SiO₂ is used:

1. Because it is easily deposited on various materials and grown thermally on silicon wafers.

2. It is resistant to many chemicals used during the Etching of other materials.

3. It has high dielectric strength and a relatively wide bandgap, making it an excellent insulator