In this study, we proposed low-temperature Au–Au bonding using nanoporous Au–Ag sheets, fabricated by dealloying a Au–Ag sheet in HNO3 solution, as a joint layer. The influence of the annealing temperature on the pore structure and chemical properties of the sheets was investigated. The chemical composition of the sheet was analyzed by X-ray photoelectron spectroscopy (XPS). It was found that the strength of Au–Au bonding with the nanoporous sheet increased. A sheet treated with liquid N2 was also tested; the strength of the Au–Au bond increased as a result of this low-temperature treatment.

A process for the simultaneous fabrication of through-glass interconnect vias (TGVs) and gold (Au) bumps using dry film resist and submicron Au particles is proposed. A Ti/Pt/Au layer was sputtered on the top and bottom surfaces of glass vias to improve the adhesion between the glass substrate and submicron Au particles. The submicron Au particles filled the resist holes and glass vias fabricated by photolithography and by the two-electrode method, respectively, and were then sintered. The height and diameter of the fabricated Au bumps were about 20-25 and 200 µm, respectively. The Ti/Pt/Au layer on the surface of the glass substrate was removed by Ar ion milling to isolate each bump electrically. The resistance of a single Au bump and TGV was evaluated using the four-wire ohm method to be about 0.05 Ω. Furthermore, Au bump bonding was demonstrated. Fractured Au bumps and TGVs were observed by scanning electron microscopy after the bonded sample was peeled. It is expected that this fabrication process using a dry film resist and submicron Au particles will be useful in simple packaging processes to form glass interposer substrates or glass integrated circuit chips.

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We proposed low-temperature Au-Au bump interconnects bonding using nanoporous Au-Ag powders as a connective adhesion. The nanoporous powders were formed by de-alloying Au-Ag alloy in HNO 3 solution. To optimize the pore size, the influence of the annealing temperature on the porous structures was investigated. Selective transfer of the nanoporous powders on bumps was obtained by stamping process. Bonding strength of about 2.4 MPa was achieved at 150 °C by using nanoporous Au-Ag powders. Bonding interface was evaluated by scanning acoustic microscope and scanning electron microscopy. This result indicated that the nanoporous powder is a useful material for low-temperature Au-Au bonding.