Propagation characteristics of finite ground coplanar waveguide on Si substrates with porous Si and polyimide interface layers

Measured and modeled propagation characteristics of Finite Ground Coplanar (FGC) waveguide fabricated on a 15 Ω-cm Si substrate with a 23 μm thick, 68% porous Si layer and a 20 μm thick polyimide interface layer are presented for the first time. Attenuation and effective permittivity as function of the FGC geometry and the bias between the center conductor and the ground planes are presented. It is shown that the porous Si reduces the attenuation by 1 dB/cm compared to FGC lines with only polyimide interface layers, and the polyimide on porous silicon demonstrates negligible bias dependence.