Appeal No. 1997-3304 Page 9
Application No. 08/181,936
alleviate the
particle build-up, costly maintenance cleaning schedule
procedures have been implemented by semiconductor wafer
manufacturers resulting in undesirable down-time."
Thus, we find that all of the features of claims 1 and 8
are found in the appellants' description of the prior art with
the exception of the tapered pipe outlet coupled to the inlet
of the chamber.
Both the application before us on appeal and Philipossian
are in the same field of semiconductor wafer processing.
Philipossian has recognized a problem associated with the flow
of gas from inlet (15) into a furnace tube (10) for processing
semiconductor wafers. More specifically, Philipossian (Fig.
8) shows that the problem involves turbulent, recirculating
gas flow at the sharp corners of the inlet of the furnace. As
explained in column 5, lines 22-35, the flow of gas passing
the sharp corners of the inlet of Figure 8 experiences an
abrupt change in velocity, as well as physical shape and
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