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Abstract

A method and system to form a refractory metal layer over a substrate includes introduction of a reductant, such as PH.sub.3 or B.sub.2H.sub.6, followed by introduction of a tungsten containing compound, such as WF.sub.6, to form a tungsten layer. It is believed that the reductant reduces the fluorine content of the tungsten layer while improving the step coverage and resistivity of the tungsten layer. It is believed that the improved characteristics of the tungsten film are attributable to the chemical affinity between the reductants and the tungsten containing compound. The chemical affinity provides better surface mobility of the adsorbed chemical species and better reduction of WF.sub.6 at the nucleation stage of the tungsten layer. The method can further include sequentially introducing a reductant, such as PH.sub.3 or B.sub.2H.sub.6, and a tungsten containing compound to deposit a tungsten layer. The formed tungsten layer can be used as a nucleation layer followed by bulk deposition of a tungsten layer utilizing standard CVD techniques. Alternatively, the formed tungsten layer can be used to fill an aperture.

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