Composition of tungsten silicide films deposited by dichlorosilane reduction of tungsten hexafluoride

Article abstract of DOI:10.1149/1.2087105

The composition profile of tungsten silicide (WSi_x) films deposited by low-pressure chemical vapor deposition employing dichlorosilane (DCS) reduction of tungsten hexafluoride (WF₆) is studied. Diffusion is the reaction rate-limiting process at chuck temperatures above 550°C and uniform in-depth composition profiles can be obtained. Below 550°C, however, the in-depth composition profile is not uniform for the surface reaction rate-limiting process. Tungsten-rich layers with a Si composition, x, of 1.5, are initially deposited due to the reduction of WF₆ by the Si surface. This layer is amorphous or microcrystalline. Thereafter, the silicon content of the film increases with increasing thickness and a uniform composition profile is obtained as determined by the DCS/WF₆ flow rate ratio in the chemical reaction. Chemical vapor-deposited tungsten silicide (WSi_x) films have been extensively used as polycide gate and interconnections for very large-scale integrated circuits.