SiO2 Insulator Geometry Effects on the Characteristics of Coplanar Waveguide Lines Based on High-resistivity-Si Substrate

In this paper, it is shown that the presence and geometry of SiO2 insulator layers sandwiched between CPW line conductors and a HRS Si substrate have an important effect on the propagation characteristics of CPW lines based on these substrates. Measured RF dissipation loss at 40 GHz on a CPW line realised on SiO2-Si substrate is 0.5 dB/cm higher than that of a CPW line constructed directly on the Si substrate. However, the RF losses below 10 GHz in the former line type is lower than that of the latter line type. Experimental results are explained by both microwave and semiconductor physics theory. The dispersion phenomena of all the CPW line types tested are reported.