Appeal No. 2000-1587
Application 09/055,254
we find that Zheng provides no teaching or suggestion for
modifying the 1:1 ratio. Whereas claim 1 requires that the
etching back be performed with a recipe having a higher etch
rate for the oxide than that of the SOG. This differential
etch rate causes most of the thick oxide layer over the hard
mask in the larger area be etched away while more of the SOG
layer remains over the shallow trench in the larger area as it
is etched more slowly (specification, page 5, lines 19-26).
We next review the teachings of Wolf 1 with respect to
heating of the low temperature, low density silicon dioxide in
order to densify the oxide layer and decrease its etch rate in
hydrofluoric acid (HF) solution (page 184). We first observe
that the teaching relied upon by the Examiner relates to oxide
layers deposited at low temperatures using Chemical Vapor
Deposition (CVD), rather than the claimed spin-on-glass (SOG).
Additionally, we note that Wolf 1 merely suggests that
“[s]ubsequent heating of such [CVD] films to temperatures
between 700-1000EC causes densification.” Therefore, Wolf 1
provides no teachings or suggestion to support “multiple
cycling of placing silicon oxide by PECVD and etching for
adhesion [that] will create a build up such as by High Density
10
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