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IC FABRICATION STEPS


• Wafer Preparation
• High purity Si. Single crystal.
• 10 – 30 cm in dia, 1 meter in length.
• Sliced, 400-600 micron thick. Surface then polished.
• Oxidation
• Oxygen, wet or dry, chemically reacts with Si => SiO2 at 1000-1200 deg.C
• At Si surface, thin SiO2 film, 0.1 – several micron thick.
• Diffusion
• Atoms move thru crystal lattice at 1000-1200 deg.C
• Doping such as n-well, pn junction, etc.
• As, P, B
• Ion Implantation
• Drive Ions into Si crystal by High voltage (100kV) ion accelerator, at room temp.
• Precise control of doping level.
• Depth of penetration well controlled.
• ex) NBL in BJT
• Chemical Vapor Deposition
• Chemical vapors reacts to form thin films.
• Ex) SiO2, Si3N4 .. at T< 500 deg.C • Polycrystalline Silicon = polysilicon • Metallization • To form interconnects (wires), capacitor plates, … • Aluminium • Photolithography • Photographic pattering of circuit on Si surface. • Photoresist = photosensitive ‘polymeric’ material • Packaging • Chip (1-10mm) = 10-1B transistors; Wafer=several 100 chips • Electrical testing  Dicing the wafer into chips  Packaging





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