Copper coplanar waveguides on Si substrates for frequencies up to 40 GHz

This paper presents an experimental study of copper coplanar waveguides fabricated on silicon substrates suitable for use in post-process CMOS IC fabrication. The waveguides were separated from the substrate by thick layers of polyimide. Waveguide performance is compared to that of aluminum control devices underlayed with silicon dioxide. The lower resistance of the copper and improved substrate isolation obtained with the low-k polyimide dielectric provide a significant performance boost compared to the controls. Application of the copper/polyimide waveguides in a 10 GHz distributed amplifier in 0.35 μm CMOS technology is examined. A significant performance advantage is observed for the Cu/Polyimide CPWs compared to Al/SiO2 controls.