Accurate impurity diffusion simulation under oxidizing conditions demands
the simultaneous simulation of point defects and impurities. Diffusion
equations are solved for the silicon self-interstitials 
and
vacancies 
. In (3.2-32) the symbols 
, 
and
denote the diffusion coefficients for interstitials and vacancies and
the bulk recombination constant (Frenkel-pair mechanism), respectively.
As boundary conditions at the 
interface we assume surface
recombination for interstitials and vacancies, and an interstitial
generation to be proportional to the oxidation rate (3.2-33),
(3.2-34).
is the atomic density of silicon (
), 
and 
are the surface
recombination velocities for interstitials and vacancies, respectively, and
determines the fraction of consumed silicon atoms which is injected
into the substrate.
The boundary conditions for the impurity atoms are the same as in the analytical model. The implemented parameter values are summarized in Table 3.2-6. The values for interstitials are from Bronner and Plummer [Bro87], values for vacancies are from Tan and Gösele [Tan85].
