Appeal No. 1999-1047 Page 7
Application No. 08/238,598
cast or molded into the gas distribution plate during its manufacture. Be that as it may,
what is clear is that the reference does not teach that each passage comprises a channel
formed within a base part which is sealed by a separate cover plate.
As explained in columns 1 and 2, the Kessler invention solved a problem that was
present in the art of providing cooling for a gas vapor deposition system for processing
wafers. The problem involved cooling the O-ring seals in the end caps of quartz tubes,
which previously had been attempted by wrapping cooling fluid tubing about the
circumference of the end cap and welding it in place with or without a heat sink paste
between the tubing and the end cap, by machining grooves in the end cap and installing
the tubing therein, and by sliding a sleeve over the tubing in the grooves to force it into
better contact with the end cap. According to Kessler, these techniques resulted in
insufficient cooling and were difficult to accomplish. Kessler solved the problem by
forming a fluid passage in the outer surface of the end cap and then sealing it with a
separate cover plate installed over the fluid passage, with the cover plate being provided
with fluid inlet and outlet ports in communication with the passage. It should be noted that
the fluid passage is not continuous, so the fluid must flow from the inlet, which is at one
end, to the outlet, which is at the other end. The stated advantages of this construction
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