Summary Unit2

# Summary Unit2 - Unit 2 Crystal growth wafer fabrication...

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Unit 2: Crystal growth, wafer fabrication, basic properties of Si wafers Packing factor: (#spheres/cell)(sphere volume) / (volume unit cell) Problem 1: Knowing that Si has a=5.43A, what is the density of Si in atoms/cm 3 ? # atoms in 1 unit cell = # corner + # face centered + # extra = 8 x (1/8) + 6 x (1/2) + 4 = 8 volume density = #atoms unit cell / volume unit cell = 8/a 3 = 8/(5.43A) 3 = 4.9967E22 atoms/cm 3 #atoms in plane = 4 x(1/4) + 2 x (1/2) + 2 = 4, area of (110) plane = 1.414a 2 = 4.1697E-19m 2 area density: #atoms in plane/area of plane = 4/4.1697E-19m 2 =9.59E18atoms/m 2 Defects in crystal: point defects (substitutional impurity, interstitial impurity, lattice vacancy, Frenkel-type defect) Cz process- growth rate (derivation), inherently introduces O and C, O provide mechanical strength, internal gettering If impurities prefer to stay in: o Liquid: C L > C s Solid: C s > C L Segregation coefficient k 0 =C s /C L , most <1 meaning prefer to stay in liquid, as crystal is

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Summary Unit2 - Unit 2 Crystal growth wafer fabrication...

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