Characterization of CVD tungsten deposited by silane reduction

The deposition of tungsten by silane reduction of WF6 was investigated to d etermine the effect of the deposition chemistry on the layer properties. Th e influence of the deposition chemistry on the titanium adhesion layer was also investigated. To perform a direct comparison of the effect of the depo sition parameters on the layer properties layers of equal thickness were de posited. In order to do this the deposition rates first had to be establish ed experimentally. When the SiH4/WF6 ratio was maintained constant at 1 and the deposition temperature increased the resistivity of the layers decreas es, and the roughness increased significantly. When the temperature was mai ntained constant at 450 degreesC and the SiH4/WF6 ratio was varied, it was found that the resistivity remained constant until the tungsten transformed to beta phase tungsten. At this transformation point the stress of the dep osited layer and the roughness were seen to decrease significantly. It was found when the correct chemistry was applied at deposition temperatures up to 400 degreesC the initial reaction between the WF6 and the Ti could be el iminated or reduced. (C) 2001 Kluwer Academic Publishers.