With reference to FIG. 3, an Mx+1 dielectric 130 may be deposited over the structure, and subsequent damascene or dual damascene structures may be created. The Mx+1 dielectric 130 may electrically insulate the tetragonal phase tungsten silicon layer 120 from additional interconnect levels (not shown) that may be subsequently formed above the tetragonal phase tungsten silicon layer 120. The Mx+1 dielectric 130 may be deposited using typical deposition techniques, for example, chemical vapor deposition. The Mx+1 dielectric 130 may include any suitable dielectric material, for example, silicon nitride (Si3N4), silicon carbide (SiC), silicon carbon nitride (SiCN), hydrogenated silicon carbide (SiCH), or other known capping materials. The Mx+1 dielectric 130 may have a thickness ranging from about 20 nm to about 60 nm and ranges there between, although a thickness less than 20 nm and greater than 60 nm may be acceptable.
Still referring to FIG. 3, a damascene opening 135 may be formed in the Mx+1 dielectric 130. The damascene opening 135 may include a trench opening and two via openings. The damascene opening 135 may be formed using any suitable masking and etching technique known in the art. In one embodiment, a dry etching technique using a fluorine based etchant, such as, for example CxFy, may be used. In one embodiment, the depth of the trench opening may range from about 50 nm to about 100 nm. Also, the via openings may extend vertically from the bottom of the trench opening down to the top of the first and second Mx metals 206, 208.
