Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias
Trevor M. Braun, Daniel Josell, Manoj R. Silva, Thomas P. Moffat
This work examines Cu deposition in low chloride, suppressor containing electrolytes that exhibit a transition from passive to active deposition partway down filling features based on the coupling of suppression breakdown and surface topography. The interplay between metal deposition and chloride- mediated suppressor adsorption and deactivation yields S-Shaped Negative Differential Resistance (S-NDR) in voltammetric measurements of Cu deposition that is explored using a rotating disk electrode (RDE). Both RDE rotation rate and chloride concentration impact the potential at which the breakdown of suppression occurs. Copper deposition in the presence of dilute chloride in high aspect ratio Through Silicon Vias (TSV) exhibits deposition passivated near the via opening and a transition to active deposition farther down the via, such as has been previously detailed for certain Au, Ni and Co electrolyte-suppressor systems. At higher chloride concentrations (80 μmol/L), copper deposition in TSV transitions over time to bottom-up filling typically described for Cu-suppressor systems with higher (1 mmol/L) chloride concentrations. A simple, 2-additive S- NDR model utilizing kinetics from the voltammetry quantitatively predicts the passive-active transition and shift to bottom-up filling observed in the TSV. This work, in conjunction with previous results with Ni, Co, Au, and Cu at higher Cl- concentrations, clarifies the conditions for which the different S-NDR filling behaviors are observed as well as the electrochemical signatures of each.
, Josell, D.
, Silva, M.
and Moffat, T.
Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias, Journal of the Electrochemical Society, [online], https://doi.org/10.1149/2.0341901jes
(Accessed April 22, 2021)