Using in situ characterization during rapid thermal annealing in conjunction with
transmission electron microscopy, we demonstrate that multiple metal rich phases
are present in the Ni-Si system when reacting a thin Ni film with an underlying Si
substrate. The formation temperatures for the metal rich phases highly depend on
dopant type but are relatively insensitive to surface preparation. We also show
that a serious limitation for NiSi implementation in devices is the low
morphological stability of the film, which degrades before the monosilicide
transforms to the high resistivity NiSi2 phase. The nucleation of this latest phase is
not desired in devices not only because the resistivity of the phase is larger but
also because its formation requires more consumption of the Si substrate which is
limited in state-of-the-art devices. The nucleation occurs at lower temperature in
thicker films because of the higher area density of nucleation sites. We also find
that the nucleation of NiSi2 is very dependent on the temperature ramp rate as the
morphological degradation of the film competes with the nucleation processes and
retards the phase formation.
By: C. Lavoie, R. Purtell , C. Coïa , C. Detavernier, P. Desjardins , J. Jordan-Sweet, C. Cabral, Jr.,F.M. d'Heurle, J.M.E. Harper.
Published in: RC22445 in 2002
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