Coplanar waveguides fabricated by directly bonding metal foils to high-resistivity Si substrates

Coplanar waveguides are fabricated by directly bonding 17-μm Al foils to Si substrates with different resistivities. A lower insertion loss is observed for a Si substrate with higher resistivity since the substrate loss is decreased. Calculation using an analytical model shows that the insertion loss increases by reducing the thickness of conductors, which demonstrates the superiority of direct bonding of metal foils for realizing low-loss passive components to be integrated on semiconductor substrates.