Appeal No. 1999-2406
Application No. 08/825,256
a solution (e.g., a photoresist) to a surface of a substrate
such as a glass substrate or semiconductor wafer.
(Specification, page 1, lines 5-8.) The specification explains
that it has been customary to apply a uniform coating of the
solution by dropping the solution onto the center of the
substrate and then rotating the substrate with a spinner to
spread the coating uniformly over the entire surface of the
substrate under centrifugal forces. (Id. at page 1, lines 14-
19.) However, it is further stated that this conventional
method is problematic in that "a large amount of coating
solution tends to be scattered off." (Id. at page, lines 20-
26.)
Attempts to solve this problem by using a slit nozzle have
been made, but the appellants explain that these previous
methods are still problematic "because the coating solution
cannot completely uniformly be deposited because of the surface
tension of the dropped coating solution" and "the solvent in the
coating solution tends to be evaporated quickly, making the
coating solution more viscous soon." (Id. at page 2, lines 1-
23.) Another previous method involves the use of the tip end of
a slit nozzle "to uniformize the thickness of a film" (id. at
page 2, lines 24-27), but the appellants disclose that "the slit
2
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