For the presented formulation of the HPCVD model which is derived
from [35] a finite element discretization scheme was used. The
governing principle for continuum transport determined chemical vapor
deposition is species balance, i.e., time dependent diffusion of gas species in
the gas phase including homogeneous (volume) reactions
Moreover we assume a constant concentration of the th species at the top of
the simulation domain
(7.1) is formulated in an AMIGOS volume model assigned to the complete
simulation domain. (7.2) is set up in a boundary model description applied
only to the wafer surface. (7.3) and (7.4) are handled as
Dirichlet boundary condition at the top of the simulation domain and as Neumann
condition at the domain sidewalls, respectively. The diffusion and reaction
equations contain the concentrations of all involved gas species which are
coupled by the stoichiometry of the chemical reactions. Consequently, transport
of gas molecules from the plasma above the wafer into the feature competes with
surface reactions which transform the reactants to a solid material forming the
deposited layer. This competition leads to a steady state equilibrium and a
geometry specific species concentration distribution depending on the ratio
between gas diffusivities and surface reaction rates. For the steady state
it is sufficient to solve the time independent formulation
Putting the resulting steady state concentrations at the boundary into the reaction rate equations leads to specific local deposition velocities which are passed on to the topography module.
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Up: 7.1 Simulation Model
Next: 7.1.4 Surface Propagation