Superconformal Bottom-Up Nickel Deposition in High Aspect Ratio Through Silicon Vias
Daniel Josell, Thomas P. Moffat
This work demonstrates controlled bottom-up nickel filling of Through Silicon Vias based on the coupling of suppression breakdown and surface topography. Deposition was performed in a NiSO4 + NiCl2 + H3BO3 electrolyte with a branched polyethyleneimine suppressor. The impact of deposition potential and additive concentration on the filling of patterned features was examined. Voltammetric measurements, including the impact of rotation rate and suppressor concentration on the rate of metal deposition, were used to quantify the interplay between metal deposition and suppressor adsorption. The derived kinetics were used to quantitatively predict the observed bottom-up filling. Based on this understanding, a strategy of progressively increasing the applied overpotential enables void-free feature filling to be accomplished. This work extends the understanding and application of additive derived S-shaped negative differential resistance (S-NDR) in bottom-up superconformal deposition, including previous demonstrations of superconformal copper, nickel, zinc and gold deposition.