Appeal No. 2001-1133 6
Application No. 09/014,806
contains a small amount of O2 or CO2. However, when using such a mixed
gas for etching of Si3N4 on top of SiO2, the etch rate of the underlying SiO2
also increases because of the suppression of the formation of the polymers
which are effective to prevent etching of SiO2. Consequently, the selective
ratio of etching between Si3N4 and SiO2 becomes very much lower than the
desired or tolerable level. This deficiency is not fundamentally removed even
when CO2 is added to the etching gas instead of O2.
See column 2, lines 33-44. See also column 1, lines 45-61, and column 3, lines
34-42. We determine that the entire disclosure present in Kadomura supports the
proposition that the utilization of oxygen lowers the selectivity ratio of etching between
silicon nitride on a silicon dioxide substrate. Accordingly, we conclude that Kadomura
expressly teaches away from the utilization of oxygen in etching a silicon nitride on a silicon
dioxide substrate. It follows that the examiner’s conclusion that oxygen be present in an
etching process because it is a well known oxidizing gas is untenable. Accordingly, the
rejection of the examiner cannot be sustained.
DECISION
The rejection of claims 1 through 3, 5 through 10, 12, 13, and 15 through 18
under 35 U.S.C. §103(a) as being unpatentable over Kadomura is reversed.
The rejection of claims 1 through 3, 5 through 10, 12, 13, and 15 through 18
under 35 U.S.C. § 112, first paragraph, for failing to enable any person skilled in the art
to make and use the invention is reversed.
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