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Journal of the Electrochemical Society, Vol.166, No.1, D3259-D3271, 2019
Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias
Bottom-up Cu deposition in metallized through silicon vias (TSV) depends on a co-adsorbed polyether-Cl- suppressor layer that selectively breaks down within recessed surface features. This work explores Cu deposition when formation of the suppressor blocking layer is limited by the flux of Cl-. This constraint leads to a transition from passive surfaces to active deposition partway down the via sidewall due to coupling between suppressor formation and breakdown as well as surface topography. The impact of Cl- concentration and hydrodynamics on the formation of the suppressor surface phase and its potential-dependent breakdown is examined. The onset of suppression breakdown is related to the local Cl- coverage as determined by the adsorption isotherm or transport limited flux. A two-additive co-adsorption model is presented that correlates the voltammetric potential of suppression breakdown with the depth of the passive-active transition during TSV filling under conditions of transport limited flux and incorporation of Cl-. The utility of potential waveforms to optimize the feature filling process is demonstrated. At higher Cl- concentrations (>= 80 mu mol/L), sidewall breakdown during Cu deposition occurs near the bottom of the via followed by a shift to bottom-up growth like that seen at higher Cl- concentrations. (C) The Author(s) 2019. Published by ECS.