Chemical vapor deposition of tungsten on silicon and silicon oxide studied with soft x‐ray photoemission

The growth of tungsten films on silicon and oxidized silicon surfaces via the silicon reduction of WF₆ was studied with soft x‐ray photoemission. The films were grown in ultra‐high vacuum and analyzed in situ. It was found that the growth on clean Si proceeds via diffusion of Si atoms through the W film to the surface, so that the silicon atoms become available for the reduction reaction. Post‐fluorination of these films via XeF₂ was performed in order to ascertain the structural details and to investigate further the role of fluorine in the growth process. Silicon oxide surfaces were prepared and subsequently exposed to WF₆. It was found that a fully formed SiO₂ surface is inert with respect to WF₆, but that a partially formed oxide will permit partial WF₆ dissociation.