US Patent 7550851 Adhesion of tungsten nitride films to a silicon surface

A process is described that forms a low resistivity connection between a tungsten layer and a silicon surface with high adherence of the tungsten to the silicon. The silicon surface is plasma-cleaned to remove native oxide. A very thin layer (one or more monolayers) of Si-NH2 is formed on the silicon surface, serving as an adhesion layer. A WNx layer is formed over the Si-NH2 layer, using an atomic layer deposition (ALD) process, to serve as a barrier layer. A thick tungsten layer is formed over the WNx layer by CVD. An additional metal layer (e.g., aluminum) may be formed over the tungsten layer.