Low-loss characteristics of coplanar waveguides fabricated by directly bonding metal foils to high-resistivity Si substrates

Abstract

Coplanar waveguides (CPWs) are fabricated by directly bonding 17-m Al foils to Si substrates with different resistivities and wet etching. Their RF characteristics are compared with those of CPWs fabricated on 0.8-m thick evaporated Al layers. A lower insertion loss is observed for Si substrates with higher resistivity irrespective of thickness of conductors because the substrate loss is decreased. For a 10000-Ω·cm Si substrate, Al-foil-based CPWs reveal a ∼0.7-dB/cm lower insertion loss in comparison with evaporated-Al-based CPWs at 1 GHz. These features agree with calculation, which implies the superiority of direct bonding of metal foils for realizing low-loss passive components.

Heterojunctions fabricated by surface activated bonding–dependence of their nanostructural and electrical characteristics on thermal process

“…We also found that Al-foil-based CPWs on Si wafers with high resistivities (∼10 4 Ωcm) outperformed those of CPWs made of 0.8 μm thick evaporated Al layers. 121) It is assumed, consequently, that low-loss passive components monolithically integrated with electron devices are achievable by suppressing the parasitic effects due to the fabrication process.…”