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- k interconnects. Ru/TaN and Ru_0.9 Ta_0.1/TaN 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_0.9 Ta_0.1/TaN liner stacks show EM resistance improvement over the Ta/TaN bilayer liner system.