Survey of P-Block Metal Additives for Superconformal Cu Deposition in an Alkaline Electrolyte

Catalysis of Cu deposition from a near-neutral Cu(2+) complexed electrolyte is examined using Bi(3+), Pb(2+) and Tl(+) additives that were selected based on their known ability to accelerate Au deposition in near neutral pH gold sulfite electrolytes. Where appropriate, the ability of these electrolytes to yield superconformal filling of recessed features is also briefly examined. Voltammetry reveals strong acceleration of Cu deposition by Bi(3+) additions while indication of superconformal filling accompanied by unusual microstructural transitions are evident in cross-sectioned specimens examined by scanning electron microscopy. Results are discussed in the context of behaviors observed for the same heavy metal additives in gold sulfite electrolytes.