Cross-sectional transmission electron microscopy study of the influence of niobium on the formation of titanium silicide in small-feature contacts

• The influence of a Nb layer between Si and Ti on the formation of TiSi2 in small-feature contacts and of the substrate doping level has been studied using transmission electron microscopy in combination with convergent-beam electron diffraction. For an As dose of 2.5x10(16) cm(-2), a mixture of C49 and partially agglomerated C54 TiSi2 grains was found in some of the 5x5 mum(2) contact windows, while only C49 existed in the 0.7x0.7 mum(2) windows. Agglomeration is shown to lead to possible C49-C54 coexistence, as well as erroneous interpretation of the C54 nucleation density. Decreasing the As dose to 5x10(15) cm(-2) leads to a thicker TiSi2 layer, but does not have a major influence on phase formation in the small windows, although only C54 TiSi2 was found in the large ones. In the presence of a thin Nb layer between Ti and poly-Si, C40 (Ti,Nb)Si-2 was consistently found in all contacts, indicating that formation does not depend on the contact size at least down to 0.5 mum(2). Surprisingly, Ti was found on both sides of the (Ti,Nb)Si-2 layer and the silicide near the interface to Si was relatively rich in Ti instead of Nb.

Keyword

tisi2

transformation

c54

si

layer

nb

Publication and Content Type

ref (subject category)

art (subject category)