Appeal No. 2003-0512
Application 09/184,805
turns to Landers for a teaching of these features.
Landers pertains to an improved polishing method for
selectively removing a layer of metallization material 10 such as
tungsten and a liner film 12 such a Ti/TiN from the surface of an
oxide layer 18 of a semiconductor wafer. As set forth in the
abstract (with drawing figure and reference numeral added):
The method includes removing the metallization and
liner layers [10 and 12, respectively] with a first
removal process which utilizes CMP polishing and an
alumina-based slurry. The first removal process is
stopped after the metallization layer [10] is
completely removed . . . [see Fig. 2]. The remainder
of the liner film [12] is completely removed [see Fig.
3] using a second removal process which includes CMP
polishing using a neutral pH silica-based slurry which
is selective to the liner film [12].
According to the examiner (answer, page 3), Landers
“discloses a method of CMP comprising: CMP [polishing] a layer 12
of the substrate with the first slurry until the layer is
partially exposed and CMP [polishing] of the same layer with the
second slurry of lower selectivity until the layer is
substantially exposed . . .” (answer, page 3). The examiner
concludes that it would have been obvious to one of ordinary
skill in the art “to CMP [i.e., polish] the filler layer of
Cadien with multiple slurries in view of Landers to more
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