Aluminum metal-insulator-metal connections for coplanar waveguides

In the present paper the possibility for using metal-insulator-metal connections (MIM-bridges) instead of air-bridges is shown. Aluminum coplanar transmission lines on high resistivity silicon substrates have been realized to examine the influence of the MIM-bridges. RF measurements up to 40 GHz show an decreasing influence of the bridges on the attenuation with decreasing width. For a width of 1 /spl mu/m of the ground-to-ground connection we achieve the same attenuation as we achieve for a transmission line without MIM-bridges (0.5 dB@20 GHz at a signal line width of 20 /spl mu/m). Transmission lines with 10 /spl mu/m wide MIM-bridges show a much higher attenuation (1.6 dB@20 GHz). By means of an equivalent circuit for the bridges, we show that reflections at the capacities of the MIM-bridges are the reason for the higher attenuation.