MSE 630 - IC Processing
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Transcript of MSE 630 - IC Processing
MSE 630 - IC Processing
CZ processing
Ingot diameter varies inversely with pull rate:
r
T
LNV mmp 3
21 5
max
L = latent heat of fusion
N = density
= Stephan-Boltzman constant
m = thermal conductivity at Tm
Tm = melt temperture (1417 oC for Si)
o = 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)(o-1)
C, I and V are concentration, number of impurities and volume when
o: initial L: liquid and s: solid
Float Zone Processing
L
xk
oos
o
CxC exp11)(
In Float Zone refining, solid concentration varies with initial concentration as follows:
Concentration
Liquid
Tem
pera
ture
Solid
CoCs CL
Typical defects in crystalsTypical 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)
Thermal stresses cause dislocations. Thermal stress is: = ET
= stress, E = Young’s modulus, = thermal expansion coefficient (m/m/oC)
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