Tungsten plug technology using substitution of W for Si

Novel W plug technology that is compatible with a conventional poly Si filling has been developed. In this technology, low-pressure chemical vapor deposition (LPCVD) poly Si is embedded in contacts and vias using etchback, and tungsten (W) is substituted for poly Si using Si reduction of WF₆. This plug technology has been successfully applied to a 0.6-μm contact and a via filling. The specific contact resistivity was 2×10^-7 and 4×10 ^-7 Ω-cm² for n⁺ and p⁺ contacts, respectively. For vias on W and WSi₂ polycide interconnections, the contact resistivity is found to be less than 1×10^-8 Ω-cm². The amount of W substituted for Si by this reaction is determined by several process parameters: thin oxides on Si surfaces, deposition temperature, and partial pressure of WF₆. W films that are more than 1.5-μm thick can be substituted for Si in this technology