Nucleation and growth of chemically vapor deposited tungsten on various substrate materials: A review

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Abstract
W films produced by chemical‐vapor deposition(CVD), typically via reduction of WF6, are being used for numerous applications in very large scale integrated circuit technology. Blanket and selectively depositedfilms require nucleation and growth on a specific underlayer material—Si, metal, or metal silicide. The compatibility of CVD W with various underlayers is reviewed for the device applications of contact/via fill, diffusion barrier, metal interconnect, and source/drain coating.Nucleation of W directly on single crystal Si can sometimes produce tunnel‐defect structures at the edges or along the entire interface of the deposit.Sputtered Mo and W, and to some extent TiW and TiN, have been shown to be suitable nucleation layers for CVD W, yielding a fluorine‐free interface with low‐electrical contact resistance. A sputtered W/Ti adhesion bilayer is demonstrated for a blanket W deposition+etchback process. CoSi2 appears an appropriate choice where CVD W and salicide technologies are combined.

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