EFFECT OF TUNGSTEN CHEMICAL-VAPOR-DEPOSITION NUCLEATION STEP ON VIA PERFORMANCE

This paper presents a study of the nucleation process for W Chemical V apor Deposition (CVD). The nucleation layer was obtained by reduction of WF6 by SiH4 and H-2. This double reduction had proved to have a lar ge latitude regarding fluorine attack of the Ti/TiN glue layer. High W F6 flows could then be investigated and process parameters controlling the step coverage were determined. Electrical performance within a 0. 25 mu m CMOS interconnects scheme using a collimated PVD glue layer wa s investigated. The W nucleation layer proved to constitute a barrier layer against fluorine diffusion at the bottom of vias during via fill processing. Thus, a high step coverage W nucleation process extends t he TiN barrier efficiency to a higher via aspect ratio.