Vertically-stacked on-chip SiGe/BiCMOS/RFCMOS coplanar waveguides

This paper presents a new on-chip transmission line interconnect structure which offers the potential of superior return and insertion loss characteristics compared to the equivalent standard transmission line device. Conventional on-chip coplanar waveguides (CPW) and differential pairs are routed in a single metal layer in the chip's metal-dielectric stack. The vertically stacked coplanar waveguide (PW) transmission lines presented here consist of metal lines on multiple metal levels connected by continuous via bars. The additional cross-sectional area of the VCPW topology decreases interconnect resistance while the increased effective device thickness increases capacitance to neighboring ground return lines leading to a characteristics impedance reduction.