Appeal No. 95-3438
Application No. 08/033,656
uniformity of coating thickness of a silicon nitride film is
not required.
Appellants stress that higher operating pressures for
depositing silicon nitride films in the semiconductor
technology are to be avoided because at pressures higher than
0.25 Torr, non-uniform silicon nitride films are produced. As
evidence factually supporting this contention, appellants
refer to the disclosures of Chiang at column 5, lines 11
through 22 and the Sakai patent at column 5, lines 1 through
32. Indeed, the abstract of Sakai discloses that the reactor
pressure for a
LPCVD process for producing a silicon nitride film of uniform
thickness should be in the range of about 0.05 to about 0.25
Torr.
In light of the specific teachings in the art relating
to the advantages of operating in a pressure range
substantially lower than that claimed for depositing a silicon
nitride coating having uniform thickness on a semiconductor
wafer, we agree with appellants that one of ordinary skill in
this art would not have been motivated to increase the
pressure of Chiang’s process to the extent claimed. While
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