Fabrication and electrical characterization of thick-metal-film coplanar waveguides on silicon oxide films by directly bonding Al foils

Abstract We directly bonded 17 μm thick Al foils to 2 μm SiO 2 films on Si substrates with a resistivity of 1–10 Ω cm by using the surface activated bonding and fabricated coplanar waveguides (CPWs) as a prototype of bonding-based interconnects on interlayer dielectrics on low-resistivity substrates. Their RF characteristics were compared with the characteristics of CPWs made of evaporated 0.8 μm thick Al layers on the SiO 2 films and those of CPWs directly fabricated on the exposed surfaces of underlying Si substrates. The Al-foil based CPWs on the SiO 2 films revealed the smallest attenuation constant, which implied that their conductor and/or substrate losses were lower than those of the other CPWs. This result indicates that the direct bonding of metal foils to dielectric films is promising for realizing low-loss interconnects monolithically integrated on low-resistivity substrates.