10 questions
1. a) Explain the various steps for shaping of crystal obtained from float zone or Cz method. [10]
b) Find the concentration of Boron in crystal at fraction solidified of 0.4, if solid concentration (Cs) at fraction solidified 0.05 is 2x10^8 atoms/cm^3 and segregation coefficient is 0.8. [6]
1. a) Mention the reason for the following: i) Point defects. ii) Surface defects. iii) Volume defects. How these defects changes during the fabrication process. [8]
b) How EGS is obtained from MGS. Also draw the block diagram for the production of EGS and also write it's chemical reaction. [8]
2. a) Define the following terms with respect to oxidation: i) Oxidation techniques. ii) Oxide properties. [8]
b) Arsenic is diffused in silicon with a doping concentration of 5x10^15 atoms/cm^3. Arsenic doping assumes a profile of Gaussian type. Arsenic is diffused for 30 minutes and a junction depth of 20 micrometers is achieved with a surface concentration of 2x10^18 per cm^3. Find the diffusivity of arsenic. [8]
2. a) Show analytic solutions of Fick's law and explain the correction in this theory. [8]
b) Write the range theory of Ion Implantation. [8]
3. a) Explain chemical equilibrium and the law of mass action. [7]
b) What is autodoping and how can this be minimized? [5]
c) Compare LPCVD with APCVD. [4]
3. a) What do you mean by Epitaxy? Explain vapor phase epitaxy and defects in epitaxial growth. [8]
b) Explain the molecular beam epitaxy. [8]
4. a) Explain the projection printing with suitable diagram. [8]
b) Compare Wet Etching with plasma Etching. [8]
4. a) What is optical lithography? Explain proximity printing and compare it with contact and projection printing. [8]
b) Draw the Flow chart for Mask generation process. Explain each term with proper explanation. [8]
5. a) Write the fabrication process sequence for twin tub CMOS process. [8]
b) Write technical note on: i) Metallization. [4] ii) Planarization. [4]
5. a) Explain Bipolar IC fabrication process sequence with help of neat sketch. [8]
b) Write short notes on following: i) LOCOS method. [4] ii) SOI techniques. [4]