Simulating the Influence of Supporting Electrolyte Concentration on Copper Electrodeposition in Microvias
Trevor Braun, Jimmy John, Nagarajan Jayaraju, Daniel Josell, Thomas P. Moffat
Robust, void-free Cu electrodeposition in high-aspect ratio features relies on careful tuning of electrolyte additives and electrochemical parameters for a given feature dimension or wafer pattern. Typically, Cu electrodeposition in electronics manufacturing having microscale or larger features (i.e., microvias, through-holes, and high-density interconnects) employs a CuSO4 – H2SO4 electrolyte containing millimolar levels of chloride and, at a minimum, micromolar levels of a polyether suppressor. Research and optimization efforts have largely focused on the relationship between electrolyte additives and growth morphology, with less attention given to the impact of the supporting electrolyte. Accordingly, a computational study exploring the influence of supporting electrolyte on Cu electrodeposition in microvias is presented herein. The model builds upon prior experimental and computational research on localized Cu deposition by incorporating the full charge conservation equation with electroneutrality to describe potential variation in the presence of ionic gradients. Simulations clearly demonstrate enhanced current localization to the microvia bottom as H2SO4 concentration is decreased. This phenomenon derives from enhanced electromigration within recessed features due to the decrease of conductivity as metal ion is depleted locally. This beneficial aspect of low acid electrolytes also depends on feature density, CuSO4 concentration, and the extent of convective transport.
, John, J.
, Jayaraju, N.
, Josell, D.
and Moffat, T.
Simulating the Influence of Supporting Electrolyte Concentration on Copper Electrodeposition in Microvias, Journal of Electrochemical Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933473
(Accessed October 2, 2023)