Integrated Transmission Lines on High-Resistivity Silicon: Coplanar Waveguides or Microstrips?

We present an experimental study of the effect of the accumulation or inversion layer at the surface of a high-resistivity silicon substrate on the loss of transmission lines. It is shown that the relative contribution of the surface channel to the total loss becomes increasingly significant as the silicon resistivity decreases. The experiments demonstrate that the effect of the surface channel on the loss of an integrated microstrip is considerably lower than that of a comparable coplanar waveguide, favoring microstrips for integration on high-resistivity silicon substrates.