Appeal No. 2001-2590
Application No. 09/449,063
1992). Although Wristers is directed to a different goal, it
teaches generally that oxygen implantation, through a layer, is
known to increase oxidation in a silicon substrate. (column 6,
lines 2-7). That is the goal of Hsu’s fluorine implantation.
Both fluorine and oxygen are recognized as oxidation enhancers in
polysilicon in the cited references. As stated in In re Fout, 675
F.2d 297, 301, 213 USPQ 532, 536 (CCPA 1982) “[e]xpress suggestion
to substitute one equivalent for another need not be present to
render such substitution obvious.”
Consequently, we concur with the examiner that claim 1 would
have been obvious in view of Hsu and Wristers, and affirm this
rejection.
The rejection of Claims 7-8 and 10-12 under 35 U.S.C. §103(a)
The examiner has found that Barsan discloses a processing
sequence whereby nitrogen is produced in both high and low
concentrations to form three different thicknesses of gate oxide
layers. (Examiner’s Answer, page 4, lines 19-22). The examiner
thus concludes that it would have been obvious to use the oxygen
of Wristers in the process of Barsan to form three different
layers in Hsu.(Examiner’s Answer, page 4, line 22-page 5, line 3).
The appellants urge that Barsan discloses an N-type dopant
implant for increased oxide thickness and a nitrogen implant for
reduced oxide thickness, but does not teach oxygen. (Appeal
Brief, page 7, lines 1-3).
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