Appeal No. 1996-2088
Application No. 08/082,432
Maeda discloses forming a Ti layer on each side of a TiN layer in a conventional Al/TiN
metallization process to suppress Al electromigration, especially at contact holes, which occurs in the
Al/TiN structure (page 50, col. 2, para. 1-2). Hu discloses an Al(Cu)/Ti/TiN/Ti structure, noting that
the Ti serves to reduce contact resistance between metal silicide and the Al(Cu) conductor, to enhance
electromigration resistance and to provide better adhesion to dielectric materials while the TiN layer is
used as a diffusion barrier layer between Al and Si (para. bridging pages 1498-99). As recognized by
the examiner, “[n]either Maeda nor Hu et al. teach a TiON layer or a two layer Al structure” (answer,
page 4).
The APA, i.e., the “BACKGROUND OF THE INVENTION” section of the specification,
acknowledges both that Ti/TiN and Ti/TiON structures have been used as barrier metal layers between
a silicon (Si) substrate and an Al-based material because Ti alone does not function as an effective
barrier (i.e., Al spikes onto the Si substrate); and, that oxygenating during deposition of the TiN layer
(i.e., forming a TiON layer) has been proposed to further suppress Al migration in the TiN grain
boundary (para. bridging pages 2-3).
Tracy discloses a two-step metallization process comprising depositing a first portion of
predetermined thickness of a metal on a semiconductor device having a via (i.e., contact hole) at a cold
temperature of approximately less than 200EC, wherein the first portion is of sufficient thickness to form
a continuous metal layer in the via at a high temperature of approximately 400EC to 500EC, increasing
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