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MSE 630 - IC Processing

MSE 630 - IC Processing. CZ processing. k o = C s /C o increases as ingot grows The dopant concentration is given by: I L =I o (1+V s /V o ) ko and C s = -dI L /dV s = C o k o (1-f) ( k o-1). Ingot diameter varies inversely with pull rate:. L = latent heat of fusion N = density

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MSE 630 - IC Processing

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  1. MSE 630 - IC Processing

  2. CZ processing ko = Cs/Co increases as ingot grows The dopant concentration is given by: IL=Io(1+Vs/Vo)ko and Cs = -dIL/dVs = Coko(1-f)(ko-1) Ingot diameter varies inversely with pull rate: L = latent heat of fusion N = density s = Stephan-Boltzman constant km = thermal conductivity at Tm Tm = melt temperture (1417 oC for Si) C, I and V are concentration, number of impurities and volume when o: initial L: liquid and s: solid

  3. Float Zone Processing Liquid Temperature Solid Cs Co CL Concentration In Float Zone refining, solid concentration varies with initial concentration as follows:

  4. Typical defects in crystals Typical defects are: Point defects – vacancies & interstitials Line defects – dislocations Volume defects – stacking faults, precipitates The equilibrium number of vacancies varies with temperature: nv = noexp(-Ev/kT) O and C are also defects with concentrations of 1017-1018 cm-3 and 1015-1016 cm-3 Other impurities are in the ppb range Thermal stresses cause dislocations. Thermal stress is: s = EaDT s = stress, E = Young’s modulus, a = thermal expansion coefficient (mm/m/oC)

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