Appeal No. 1996-2088
Application No. 08/082,432
the temperature to the high temperature, and depositing a second portion of the metal on the wafer to
obtain the desired thickness (col. 3, line 52 - col. 4, line 27), thereby improving metal step coverage
(abstract). Madokoro also discloses a two-step metallization process comprising depositing a first Al-
based material layer without heating on a silicon substrate having a contact hole and then depositing a
second Al-based material layer by bringing the effective substrate temperature to 420-450EC (page 5,
first full para.), which process obviates ohmic defects and improves resistance against stress migration
(page 4, first full para.)..
According to the examiner, it would have been obvious to one of ordinary skill in the art to
substitute a TiON layer for the TiN layer of either Maeda or Hu as recited in claims 22, 19 and 16
because TiON has improved Al migration resistance compared to TiN as suggested by the APA
(answer, page 8).
a. claim 22
Appellants argue (1) claim 22 requires depositing an aluminum layer on a Ti/TiON/Ti barrier
layer without heat and (2) a lack of motivation to combine because the APA did not recognize a three-
layer barrier structure and because the APA taught, as far as a two layer barrier structure, that TiON is
unsatisfactory when using deposition at a high temperature (brief, page 8; reply brief, page 3). First,
claim 22 neither precludes nor requires a high temperature Al layer deposition step (answer, page 7).
Second, the test for obviousness is based on the combined teachings of the applied references as a
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