Appeal No. 1997-3691 Page 7
Application No. 08/298,018
We are in agreement with the examiner (answer, page 6) that Osinski suggests providing Feist
with a disposable structure. However, even if Feist were provided with a removable structure as
advanced by the examiner, we find that the limitations of claim 6 would still not be met.
Osinski discloses (col. 1, lines 50-63) that
[i]t has been found that the use of an etching mask of photoresist in practice
leads to a number of disadvantages. During the step of etching the
comparatively thick layer of polycrystalline silicon, the photoresist can be
attacked, as a result of which the gate electrode formed obtains side edges
which are arranged obliquely to the surface. Consequently, it is difficult to
provide the gate electrode with suitable edge isolation parts, as a result of
which during the formation of metal silicide there is the risk that the source
and drain zones are electrically connected to the gate electrode. Moreover,
the use of photoresist for the etching mask has the disadvantage that polymeric
residues are left on the surface, which can be removed only with difficulty.”
In Osinski (col. 3, lines 40-68), a disposable structure (silicon nitride mask) (10) is used as a mask in
the forming of the gate electrode (11) to provide an electrode with practically straight edges (12) which
provides for sidewall insulators (edge isolation parts) (20) “in a simple manner on the gate electrode 11
so that during the formation of metal silicide the risk of shortcircuits [sic] is very small.” After the
formation of the source and drains (17) and (18) respectively, the disposable structure (10) is removed
prior to the formation of the silicide regions (27) (col. 4, lines 31-57), with the silicide regions being
formed at the same time. We find that while Feist forms the silicide regions (figure 8) at the same time,
Feist utilizes a photoresist layer (not shown) (figures 3 and 4, and col.6, lines 42-57) to pattern, inter
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