Low-characteristic impedance transmission line fabricated using benzo-cyclo-butene thin film

Transmission lines of very low characteristic impedance (Z/sub 0/) are fabricated and analyzed. The transmission lines are fabricated on the benzo-cyclo-butene (BCB) films of a low dielectric constant. Two types of coplanar waveguide (CPW) structures are fabricated, which include bottom-ground and double-ground type. Measurement shows that Z/sub 0/ values for each CPW type are 7.3 and 9.4 /spl Omega/, respectively, at a signal line width of 100 /spl mu/m. When the ratio between the spacing of bottom-ground and the signal line width becomes greater than 2.5, the Z/sub 0/ is nearly saturated. In addition, thin film microstrip lines fabricated using the BCB insertion layers show very low Z/sub 0/ of 25.5 /spl Omega/, and this impedance is /spl sim/64 % of the values obtained from the BCB-based CPW structures of the same line width.