Appeal No. 1999-2115
Application No. 08/724,574
5, while Morimoto has been cited only for the teaching relating
to steam ambients as recited in appealed claim 7. (Examiner's
answer, page 8.) Since the examiner has not explained how Tang
or Morimoto remedies the fundamental deficiencies of the
rejection based on Yu '843 and Rao, it follows that we also
cannot uphold rejections II and III.
Turning to rejections IV through VI, Yu '534 teaches a two-
step process of plug (tungsten) formation using chemical
mechanical planarization, in which the first CMP step is
selective to the plug material and removes the upper layer of
tungsten from an oxide surface while removing very little or no
oxide from a wafer surface and the second CMP step is selective
to the oxide and removes a portion of the insulation material to
a level even with or slightly below the tungsten plugs. (Column
3, lines 27-57.)
The examiner admits that Yu '534, like Yu '843, does not
teach the reflowing step recited in appealed claim 9.
(Examiner's answer, page 5.) This difference notwithstanding,
the examiner held that "[o]ne of ordinary skill in this art
would have been motivated to" use Rao's reflowing step to carry
out the process described in Yu '534.
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