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Abstract
SiC epitaxial films grown in an inverted chimney CVD reactor are analyzed and compared
for growth rates, doping concentration and surface morphology using silane-propane-hydrogen
and dichlorosilane (DCS)-propane-hydrogen chemistry systems. A general 1-D analytical
model is presented to estimate the diffusivity of precursor gases, boundary layer
thickness and growth rates for both gas systems. Decomposition of precursor gases
into Si growth species is investigated by a commercial simulation tool, Virtual Reactor
(VR). DCS suppresses the formation of elemental Si at lower pressures, reduces precursor
losses, and leads to increased growth rate. However, at higher pressures, even DCS
decomposes into elemental Si, which contributes to high Si depletion, limiting the
maximum achievable growth rate. Reduction of Si loss using DCS is verified by mass
measurements of parasitic depositions in the injector tube. The doping concentration
of the epitaxial film is governed by the effective C/Si ratio at the growth surface
rather than the inlet C/Si ratio, which is examined at various growth pressures. In
addition to the widely known Si-depletion, C-depletion is also shown to exist and
it plays a critical role in determining the doping concentration at various growth
conditions. Increased roughness for the DCS growth at higher pressures is addressed
and attributed to excessive HCl etching at higher pressures.