Characterization of "ultrathin-Cu"/Ru(Ta)/TaN liner stack for copper interconnects

Barrier property, gap-fill quality, and electromigration (EM) resistance of a TaN diffusion barrier with ultrathin-Cu/Ru(Ta) liner layers were carried out to evaluate its feasibility for back-end-of-the-line Cu/low-κ interconnects. Ru/TaN and Ru0.9Ta0.1TaN liner stacks show comparable oxidation and Cu diffusion barrier properties to the conventional Ta/TaN bilayer liner stack. Through observed better wettability to ultrathin Cu seed and therefore enhanced gap-fill quality, both Ru/TaN and Ru 0.9Ta0.1TaN liner stacks show EM resistance improvement over the Ta/TaN bilayer liner system. © 2010 IEEE.