Highly-oriented PVD Ruthenium Liner for Low-resistance Direct-plated Cu Interconnects

Low-resistance Cu damascene interconnects have been developed with highly oriented PVD-Ru/TaN liner using a direct-plated Cu process. Texture of the direct-plated Cu on the Ru/TaN is strongly correlated with Ru(002) orientation, enriching Cu(lll) texture comparable with a conventional plated-Cu film on seed-Cu/Ta/TaN. The resistivity of 0.2μm-wide direct-plated Cu lines with the highly (002)-oriented Ru/TaN liner at 20K is 12.4% lower than that of conventional Cu lines with Ta/TaN liner, meaning that the reduction of the resistivity in Cu lines with Ru liner at RT was achieved by smaller interface scattering besides the lower bulk resistivity of Ru than Ta. The orientation control of Ru liner is a key factor for the low-resistance Cu interconnects needed for scaled-down ULSI interconnects.