Improved Uniformity in Glass TSV Filling by Asymmetric Dwell Pulsed Potential Deposition

초록

Filling of through vias in glass interposers is explored using an acid copper sulfate electrolyte containing dilute chloride and a polyether suppressor additive. Cyclic voltammetry with a rotating disk electrode shows that suppression breakdown and hysteresis is associated with an S-shaped negative differential resistance (S-NDR). Feature filling experiments at potentials within the hysteretic potential range yield localized deposition that initiates and advances from the center of the through vias to enable void-free Cu filling. Challenges with filling uniformity across the interposer workpiece are addressed using an asymmetric pulsed potential approach to periodically reinforce active growth on the most recessed surface regions. The activation and deposition potentials are selected based on voltammetry and the S-NDR filling mechanism while accounting for distributed ohmic losses due to uncompensated electrolyte and contact resistances.

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