Fabrication of Anodic Aluminum Oxide and Cu Electrode and Improvement of Its Mechanical and Electrical Properties

The increasing demand for miniaturized and high-performance integrated circuits requires efficient interposer technologies for advanced semiconductor packaging. In this study, anodic aluminum oxide (AAO) was investigated as a potential interposer substrate owing to its excellent electrical insulation and low dielectric constant. A Pd-TiO₂ ink catalyst was applied to enhance the dielectric performance while suppressing copper ion penetration during the electroless Cu deposition. Compared to conventional Sn-Pd catalysts, the application of Pd-TiO₂ improved the dielectric stability and interfacial reliability. Subsequent Cu electroplating using nitrotetrazolium blue chloride (NTBC) as a leveling additive enabled uniform, void-free through-hole filling while minimizing surface overplating, and demonstrated improved void suppression compared to conventional multi-additive systems. Morphological and electrical characterizations confirmed the effectiveness of this single-additive method. This integrated approach combining Pd-TiO₂ catalysis and NTBC-assisted plating demonstrates a viable route toward AAO-based interposers with enhanced dielectric and metallization properties. These findings support the feasibility of using AAO substrates for next-generation semiconductor packages that require high signal integrity and thermal reliability.

Graphical Abstract

Comparison of catalyst and additive effects on copper filling in AAO interposers. OM images of Cu deposition using a commercial Sn-Pd catalyst, b Pd-TiO₂ catalyst, c NTBC-based single-additive filling after 64 h, and d three-additive filling after 9 h.