Nano-silver Doped Zinc Oxides Adhesion Layer for Wet Copper Metallization of Glass Substrates

In this work, nano-silver doped ZnO (SZO) thin films were prepared on glass substrates and through-glass vias (TGVs) using a sol-gel dip-coating method. The SZO film served as a catalytically active mixed metal oxide adhesion layer, replacing the etching, sensitization, and activation processes typically used in traditional electroless copper plating (ECP). Surface cleaning is essential for achieving high-quality coatings. In this work, an alkaline degreasing solution, followed by a citric acid chelating solution, was used to effectively enhance the wettability of the glass surface. The SZO thin film, formed on the glass substrate after dip-coating and sintering of the SZO sol, can be directly coated with a copper layer via ECP. Following subsequent electroplating, a copper film with a thickness of 11 μm and a resistivity as low as 1.84 μΩ·cm was obtained. The adhesion strength of the copper layer under vacuum annealing at 300 °C in nitrogen atmosphere is 4.19 N cm−1. In addition, the SZO sol-gel dip-coating process achieved complete coverage of the copper seed layer for TGVs with a high aspect ratio (10:1). This approach presented a cost-effective solution for fully solution-processed substrate-to-substrate interconnects in electronic device packaging applications.