Direct deposition of a blanket tungsten layer on SiO₂ by preexposure of helium plasma

By utilizing preexposure of helium plasma, a method of depositing a blanket tungsten layer directly on SiO₂ has been developed. When SiO₂ films are exposed to a helium plasma, oxygen atoms are knocked on by active species in the plasma and the surface becomes covered with reduced silicon. It is assumed that this silicon reacts with WF₆ to form tungsten nuclei, and that tungsten layers grow through the reaction of H₂ and WF₆ at these nuclei. The deposited tungsten layer is stable with a low resistivity in the form of the α-W crystal and shows strong adhesion to the SiO₂ film due to the anchoring effect of tungsten.