Y. Akasaka et al., Highly uniform low-pressure chemical vapor deposition (LP-CVD) of Si3N4 film on tungsten for advanced low-resistivity "polymetal" gate interconnects, JPN J A P 1, 38(4B), 1999, pp. 2385-2389
A W/WSiN/poly-Si multilayered "polymetal" gate structure has been proposed.
An extremely low sheet resistivity can be achieved with this structure (1.
4 Ohm/square:T-w = 100 nm). Moreover, a polymetal gate with Si3N4 cap and s
idewalls (Si3N4 capped polymetal) enables the self-aligned contact techniqu
e and source/drain self-aligned silicide (SALICIDE). Thus, an Si3N4-capped
polymetal structure is thought to be extremely useful to obtain higher dens
ity and higher performance LSIs. However, when a low-pressure chemical vapo
r deposition (LF-CVD) Si3N4 film was deposited on W, granular growth of Si3
N4 was observed. We investigated this phenomenon and found the granular gro
w th to be strongly dependent on oxidation of the W surface. We also demons
trated two methods for suppressing the granular growth.