Silicon diffusion through thin tungsten films on silicon,studied with Auger spectroscopy

Silicon out-diffusion through ? 3000 Å tungsten films deposited on silicon by r.f. sputtering was studied using Auger spectroscopy. Silicon first diffuses to the tungsten film surface by grain boundary diffusion and surface migration. The out-diffusion kinetics were most strongly dependent on the thickness of the silicon dioxide layer between tungsten and silicon, and this (native) oxide thickness varied with substrate doping. The out-diffusion rate was independent of tungsten film thickness at 540 Å and 2400 Å. For substrates from which the native oxide was removed by backsputtering just prior to tungsten deposition, no Si out-diffusion to the W film surface was observed until almost the entire film had converted to WSi².