Abstract
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 Ω/□:TW=100 nm). Moreover, a polymetal gate with Si3N4 cap and sidewalls (Si3N4-capped polymetal) enables the self-aligned contact technique and source/drain self-aligned silicide (SALICIDE). Thus, an Si3N4-capped polymetal structure is thought to be extremely useful to obtain higher density and higher performance LSIs. However, when a low-pressure chemical vapor deposition (LP-CVD) Si3N4 film was deposited on W, granular growth of Si3N4 was observed. We investigated this phenomenon and found the granular growth to be strongly dependent on oxidation of the W surface. We also demonstrated two methods for suppressing the granular growth.
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