Appeal No. 2005-0285 7
Application No. 09/881,675
The examiner admits that the primary reference to Sakurai
fails to identify the claimed barrier metal layer. But, the
Japanese document shows a barrier layer 21, formed between an
emitter electrode 20 and an insulating film 12, in Figure 2, and
the Japanese document uses an emitter electrode of aluminum and a
barrier layer of molybdenum silicide “because it has small
contact resistance with silicon, can stand high-temperature heat
treatment, and is conformable with the conventional silicon
process” (page 4 of the English translation). Moreover, this
barrier layer in the Japanese document is employed to prevent
silicon diffusion into an aluminum emitter electrode and
preventing the lowering of “the main breakdown voltage yield”
(page 4 of the English translation). Thus, the skilled artisan
is taught that where aluminum is used for the emitter electorde,
it would be wise to employ a barrier metal layer to prevent
silicon diffusion.
Sakurai is silent as to the material used for the emitter
electrode 12, and there is no indication that Sakurai would
suffer from the same problem that the Japanese document seeks to
solve, i.e., diffusion of silicon into an aluminum emitter
electrode. However, skilled artisans would have recognized that
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