In this paper, the dopant (phosphorus) effects of polycrystalline silicon (poly-Si) on dichlorosilane-based tungsten silicide deposition have been studied with emphasis on the crystallinity of the WSix film. The WSix over doped poly-Si (polycide) was formed using an integrated cluster platform which was equipped with chambers for the deposition of the in situ doped poly-Si and the dichlorosilane-based tungsten silicide without vacuum break. It was found that the phosphorus atoms in poly-Si films enhance the dissociation of WF6, and thus yield a W excessive WSix film having an amorphous feature. As the P concentration of the poly-Si is increased while the deposition temperature is decreased, the formation of the amorphous layer is facilitated. This systematic study reviews the correlations between the dopant in the underlying poly-Si and the structural, compositional, and electrical properties of the as-deposited and the annealed WSix films. Finally, a successful integrated polycide process, avoiding such a dopant effect, has been suggested.