A new fabrication process for low-loss millimeter-wave transmission lines on silicon

The new type of coplanar waveguide for millimeter-wave transmission was fab ricated on silicon by chemical mechanical polishing and selective electropl ating processes based on silicon technology The thick interconnections obta ined using these processes have less conductor loss than the conventional i nterconnections, and the deep grooves on both sides of a signal line in thi s new waveguide reduce the dielectric loss caused by the high permittivity of the silicon substrate. The electro-optic sampling technique confirmed th at the new waveguide has excellent millimeter-wave propagation characterist ics, low effective permittivity and low attenuation, at frequencies up to 3 00 GHz. The new fabrication processes should be useful in combining millime ter-wave systems with ultralarge-scale integrated circuits on silicon.