Promotion of High-Speed Copper-Filling Performance for Interconnections with Increasing Aspect-Ratio Using Compound Additives

Interconnections are essential for integrating the packaging substrate, and defect-free copper-filling can further improve the reliability in through holes (THs). The coating properties and filling processes are mainly dominated by the interplays among additives in the direct current electroplating. The acidic copper sulfate electroplating solution contained three typical convection-dependent additives and chloride ions (Cl−). The THs with aspect ratios (ARs) of 6.25, 5, and 4.17 (thickness of 500 μm) were selected as the study subjects. The effects of Cl− and ARs on the interactions among the additives were investigated in detail using electrochemical measurements, which were verified by the THs filling experiments. The additive compounds present a convection enhanced inhibition effect and cathodic polarization, leading to a copper filling capacity increase with ARs and the amelioration of copper compactness and corrosion resistance. The defect-free copper filling of THs and a uniform mirror bright surface circuit can be achieved simultaneously using compound additives at a relatively high speed.