Appeal No. 2002-1415
Application No. 09/141,812
oxygen plasma.1 The examiner turns to Savas at columns 19 and 20, in particular
column 20, lines 14-37, for teaching “a process to remove the resist and residue via an
oxygen plasma wherein ammonia as well as other compounds may be mixed with the
oxygen plasma....”
Appellants argue that there is no motivation to select ammonia from the possible
additives listed by Savas. The examiner’s position is that motivation exists because
Savas specifically states that mixing ammonia with oxygen will increase the removal
rate of the resist. (Answer at 6.) The examiner further contends that Savas teaches a
cleaning step “directed to clean a via and strip the photoresist as in Molloy” (id. at 7)
and that the teachings of Savas “show that mixture of ammonia and oxygen to clean [a]
via and strip a photoresist is [sic; was] known in the art” (id. at 8).
Savas teaches:
[O]ther gases may be used to enhance stripping. In particular, as is
known in the art, gases may be added to oxygen in small concentrations to
attack specific chemical residues that may form on the resist. During
etching, the resist may become very hard and dense. Ion implantation
may occur and impurities such as boron or arsenic may become
embedded in the resist. Etch processes may also produce a SiO2 residue
or implant aluminum contaminants in the resist. As is known in the art,
these and other side effects from wafer processing can create a resist or
film that is very resistant to reaction with oxygen atoms alone. Additives
1 Molloy indicates oxygen and “amine gases” as possible mixtures (col. 4, ll. 27-31). An amine is
“one of a class of organic compounds which can be considered to be derived from ammonia by
replacement of one or more hydrogens by functional groups.” McGraw-Hill Dictionary of Scientific and
Technical Terms Fifth Ed. at 78 (1994). An amine gas thus may be, but is not necessarily, derived from
ammonia. See, e.g., Kirk-Othmer Encylopedia of Chemical Technology Third Ed., Vol. 2 at 276-77, John
Wiley & Sons (1978) (providing examples of manufacturing amine: four examples using ammonia and one
using hydrogen cyanide and an olefin).
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