Appeal 2005-2100
Application 09/826,038
Both Appellant and our dissenting colleague views the types of etching steps that
are conducted before and after a measurement is taken as an unobvious feature of the
claimed invention. We do not agree, for the following reasons.
The use of etching for active area definition, gate recess etching, and waveguide
formation is well recognized by persons of ordinary skill in the art in the field of
compound semiconductor processing. Kirk Othmer, Encyclopedia of Chemical
Technology, vol. 21 (4th ed., 1997) p. 798. According to the reference, wet etching
can provide a clean, damage-free surface with good control of both etch depth and
lateral undercut. Id. The reference discloses one advantage of wet etching over dry
etching is the absence of subsurface damage that is common with dry etching. Metal
contacts placed on wet-etched surfaces exhibit more ideal characteristics than dry-
etched surfaces. Kirk, p. 800. The reference further discloses that for certain
applications dry etching has gained popularity over wet etching because of its
increased control of etch profiles, attaining submicrometer features and the ability to
introduce in situ monitoring capabilities into a dry-etch system. Id. Most wet etches
are isotropic which may limit their usefulness in high aspect ratio submicrometer
applications where straight wall profiles are required.
We reiterate that Appellant admits the following steps have been known in the
art: (1) etching step, (2) dimension of the film acquired, and (3) etching step. That is,
as discussed, supra, Appellant’s admitted prior art on page 1 of the specification
involves an etch step (type not specified), followed by measuring the thickness of the
film, followed by another etch step (type not specified). A feed back technique is used
rather than a feed forward technique.
8
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Next
Last modified: November 3, 2007