Ru Liner Scaling with ALD TaN Barrier Process for Low Resistance 7 nm Cu Interconnects and beyond

Low resistance Cu interconnects with CVD Ru liner have been demonstrated for 7 nm node. Ru liner thickness reduction has been achieved by replacing PVD TaN with a bilayer PVD Ta and ALD TaN stack, while maintaining adequate Cu fill performance. The newly proposed barrier stack (PVD Ta/AldTaN) with thin Ru liner studied in this paper also enabled a significant Ru CMP performance improvement by mitigating two major Ru CMP issues: Cu recess of narrow lines, and trench height variability between dense and isolated patterns. Furthermore, this novel barrier stack with Ru liner could attain void-free Cu fill even for beyond 7 nm node dimension. Thus, the PVD Ta/ALD TaN/CVD Ru liner is a promising candidate as the liner for Cu interconnects of 7 nm node and beyond.