Appeal No. 2003-0230
Application No. 09/624,025
forming a shallow trench isolation but does not disclose nitride
spacers or oxygen implantation under the trench.” (Appeal Brief,
page 5, line 22 - page 6, line 2).
The examiner has found that Sheng teaches that nitride may be
used for spacers, and that nitrides and oxides are both dielectric
in nature and would protect the trench sidewall from further
processing steps. The examiner has also found that Sheng uses
nitride for temporary spacers, but that this teaching is
sufficient to suggest that the permanent oxide spacers of Gardner
may be substituted by the nitride spacers of Sheng. (Examiner’s
Answer, page 4, lines 3-11).
The examiner has also found that Arnold teaches implanting
oxygen into the substrate at the bottom of the trench to form
silicon oxide as an isolation between device regions, an
improvement for isolation trenches as dimensions decrease. The
examiner has also found that Arnold teaches the equivalence of
TEOS or HDP for trench filling. (Examiner’s Answer, page 5, lines
19-23).
The examiner then concludes that it would have been obvious
to one of ordinary skill in the art at the time the invention was
made to use the nitride spacers of Sheng, implant oxygen to
improve isolation properties, and fill the trench using HDP with
the reasonable expectation of forming an isolation trench
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