Direct Cu electrodeposition on ta using Pd Nanocolloids: Effect of allyl alcohol on the formation of seed layer

Cu direct electrodeposition (ED) on a Ta substrate was performed using Pd nanocolloids (NCs) as a Cu nucleation promoter. Pd NCs were synthesized by a polyol method and loaded onto a pretreated Ta substrate. Through a two-step potentiostatic ED process in a pyrophosphate-based electrolyte, a continuous Cu seed layer was deposited on the Ta substrate, although the surface showed irregular morphology. The addition of allyl alcohol improved the surface regularity of the Cu seed layer, allowing the conformal Cu seed layer to be formed successfully on the 55 nm patterned Ta substrate. Cu gap-filling was achieved by galvanostatic ED in a sulfate-based electrolyte on the preformed seed layer.