FEM Study on Electrolyte Additive, External Current Density, and via Geometry for Cu Electroplating of Through-Glass Vias

Cu electroplating is one of the most expensive, complex and critical steps in fabricating through-glass vias (TGVs), which serve as the core component of 2.5D or 3D integration. This paper presents a simplified 2D via electroplating model to systematically investigate the influences of electrolyte additive, current density, and via geometry on plating performance in terms of via filling profile and Cu thickness. Under a fixed accelerator concentration of 0.1 mol/m3, plating performance for both blind- and through-vias initially improves but subsequently deteriorates with increasing suppressor concentration. Notably, the through-via filling mode dramatically transitions from super-conformal to sub-conformal, achieving a maximum throwing power (TP) of 135.74%. A gradual growth in current density from 0.1 to 0.3 amps/dm2 (ASD) leads to deteriorating plating quality for both via types, with the through-via TP dropping to 95.56%. In addition, sub-conformal filling occurs in U-shaped, V-shaped, and X-shaped blind-vias if single-sided plating is employed. However, after shifting them to a through configuration with double-sided plating, complete filling can be realized across all cases. These findings offer a theoretical foundation and practical guidance for enhancing the depositing rate and minimizing/eliminating internal void for the Cu electroplating of TGVs.