root/trunk/matml/transport/problems/cvdreact/cvdreact.tex

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\begin{document}
\begin{enumerate}
\item Chemical vapor deposition reactor design

  The cylindrical chemical vapor deposition reactor shown below deposits
  a thin film onto multiple hot wafers as one step in microelectronic device
  fabrication.
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    \PSbox{cvdcyl.ps}{200pt}{90pt}
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  \begin{enumerate}
  \item Sketch a cross-section of the reactor, and sketch the streamlines
    describing axisymmetric gas flow through it.

  \item Unfortunately, for a long tube reactor such as this, the reactant gases
    can be somewhat depleted by reactions on the first few wafers, so the
    reactant concentration is lower near the later wafers.  As a result, the
    deposition rate in the first few wafers is faster than in the last few
    (since it is roughly proportional to the local reactant gas concentration).

    Suggest a design change which would solve this problem, resulting in the
    same deposition rate at all of the wafers, and briefly support your design
    change using transport phenomena concepts.
  \end{enumerate}
\end{enumerate}
\end{document}