Improved microwave performance on low-resistivity Si substrates by introducing an oxidized porous Si interlayer

We propose the use of oxidized porous silicon as a low-loss substrate for the microwave devices. The oxidization of porous silicon is expected to increase the resistivity of Si surface layer and to reduce its effective dielectric loss, which would leads to a significant reduction of the nature loss of low-resisitivity (low-R) Si substrates under the microwave operation. In the present study, a significant improved microwave performance on low-R Si substrates has been demonstrated by measuring the microwave characteristics of coplanar waveguides fabricated on the Si substrates with thick oxidized porous surface layers.