Appeal No. 2005-0285 8
Application No. 09/881,675
an emitter electrode may be made from many conductive elements,
such as polysilicon, or metals, such as aluminum (the Japanese
document teaches the use of aluminum for such electrodes). The
skilled artisan would also have recognized that where materials
such as polysilicon, for example, are used, no barrier metal
layer would be needed because silicon diffusion would not be a
problem. However, where metal materials, such as aluminum, are
used as the emitter electrode, as in the Japanese document, there
would be a problem which a barrier metal layer would solve.
Accordingly, it is clear to us that the artisan would have
recognized that although Sakurai is silent as to the material of
emitter electrode 12, various suitable materials were known,
including aluminum, as taught by the Japanese document. Thus, it
would have been obvious to the artisan to form Sakurai’s emitter
electrode of aluminum, and to use a barrier metal layer, as
taught by the Japanese document, in order to avoid problems with
silicon diffusion.
From the Japanese document, the skilled artisan is taught
that the barrier metal layer should be formed of molybdenum
silicide. However, Okamoto taught, at column 3, lines 5-10, that
a barrier layer of either titanium nitride or tantalum nitride
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