Attenuation characteristics of coplanar waveguides on oxidized porous silicon varying with its oxidation temperature

The attenuation of coplanar waveguides formed on low-resistivity substrate with a thick oxidized porous silicon (OPS) layer varying with the oxidation temperature of the substrate was researched. The oxidation temperature changes the phase of the OPS layer from Si, air to pure SiO2 passing through Si, SiO2, air and SiO2, air. These phase transitions result in variation of the effective dielectric constant and, therefore, the attenuation characteristics of the transmission line. From the measurement results, a higher oxidation temperature improves the attenuation characteristics of CPWs, and the best performance was obtained at 1060 .deg. C for 1 hour as 0.1 dB/mm at 12 GHz with a width and gap of 30 μm and 20 μm (Zo = 75 Ω), respectively.