This paper presents the application of tungsten ALD as an advanced nucleation layer for tungsten plug fill. Tungsten has been deposited by atomic layer deposition (ALD) using WF6 and B2H6. The half reactions of WF6 with B2H6 are shown to be self-limiting, with very short reactant saturation times. The WF6/B2H6 ALD process yields a smooth, conformal fill on high-aspect-ratio via structures. The film has a fluorine content of <2 E18 atoms/cm3 and a resistivity of ∼150 μΩcm. Integration of the ALD nucleation layer with conventional tungsten CVD bulk deposition yields complete contact/via fill for high-aspect ratio structures, which significantly extends the capability of current tungsten CVD technology for IC device manufacturing. Data will also be resented on the use of SiH4 as an alternative reducing agent.