Appeal No. 2000-1587
Application 09/055,254
are removed using chemical mechanical polishing (CMP) (col. 3,
lines 22-25). However, we find that Zheng provides no
teaching or suggestion, at any stage of the process, that
relates to the claimed step of curing the SOG of which a
partially remaining residue over the shallow trench in the
larger area serves as a protection mask.
We agree with Appellants that Zheng’s relative etching
rate during the step of etching back is different from
Appellants’ claim 1 requiring a higher etching rate for oxide
compared to that of SOG. We find that during etching back of
oxide and SOG layers, Zheng requires that “the etch
selectivity of spin-on-glass to HDP oxide is 1:1" (col. 3,
lines 17 and 18), which indicates the same etching rate for
both the oxide and the SOG layers. We remain unpersuaded by
the Examiner’s arguments that the criticality of the higher
etching rate or “how high” the “higher” etching rate needs to
be are not clearly defined in the disclosure. Appellants
clearly require that the etching rate of the oxide be higher
than that of the SOG (specification, page 5). We further
disagree with the Examiner that changing the etch rate as
disclosed by Zheng is routine optimization and obvious since
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