High Q-factor of coplanar waveguide on low-k polymer layer

In this paper, technological solutions based on the use of thick low-k polymer layers on low-resistivity (LR) silicon substrate have been investigated. These thick organic layers provide an insulation of interconnects and passives circuits from the lossy silicon substrate and thus minimize its dramatic impact on the performances. Different thicknesses of polymer layer have been tested. Both EM-simulations and high-frequency characterizations have shown an important benefit in coplanar waveguide performances by employing a large polymer thickness (30 μ in our case). A noticeable increase of the Q-factor close to 16% has been achieved with burying the realized CPW lines into a quasi-homogeneous polymer medium.