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Question

A. For impurity diffusion in semiconductor, concentration gradient is the only essential requirement. 

B. Annealing is a mandatory step after ion-implantation. 

C. Wet etching is normally anisotropic 

D. High temperature is required for the growth of $SiO_2$ because oxidation reaction takes place at high temperature 

E. Bird's beak formation is a characteristic of LOCOS isolation 

Choose the correct answer from the options given below:

The correct answer is
B and E only

Semiconductor Fabrication Concepts Analysis

Evaluating each statement regarding semiconductor processing:

  • Statement A: Impurity diffusion relies on a concentration gradient, but other factors like temperature are also essential. Thus, A is incorrect.
  • Statement B: Annealing post-ion implantation is mandatory to repair lattice damage and activate dopants. Thus, B is correct.
  • Statement C: Wet etching is generally isotropic, unlike anisotropic dry etching. Thus, C is incorrect.
  • Statement D: High temperatures are necessary for $SiO_2$ growth kinetics. The statement's explanation is circular. Thus, D is incorrect.
  • Statement E: Bird's beak formation is characteristic of the LOCOS isolation process. Thus, E is correct.

Final Answer Selection

Statements B and E are correct. This corresponds to Option 3.

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Important Questions from Semiconductor Process Flow

  1. Arrange the given process steps in sequence for self-aligned gate formation. 

    A. Thermal oxidation to grow gate oxide. 

    B. Polysilicon deposition 

    C. Photolithography using gate mask 

    D. Etching of polysilicon and oxide 

    E. Source/drain diffusion 

    Choose the correct answer from the options given below:

  2. Match the LIST-I with LIST-II
    LIST-ILIST-II
    A. Shallow trench isolation (STI)I. Low static power dissipation
    B. Junction isolationII. High static power dissipation
    C. CMOS technologyIII. High component density
    D. Bipolar IC technologyIV. Low component density
    Choose the correct answer from the options given below:
  3. Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R 

    Assertion A: Impurity diffusion in semiconductor essentially needs very high temperature. 

    Reason R: Diffusivity of impurity atoms is negligibly small at room temperature. 

    In the light of the above statements, choose the most appropriate answer from the options given below

  4. In particle beam lithography, the resolution depends upon :
  5. When silicon dioxide of thickness d is grown, the Silicon consumed is :

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