CHARACTERIZATION OF BROAD-BAND TRANSMISSION FOR COPLANAR WAVE-GUIDES ON CMOS SILICON SUBSTRATES

This paper presents characteristics of microwave transmission in copla nar waveguides (CPW's) on silicon (Si) substrates fabricated through c ommercial CMOS foundries, Due to the CMOS fabrication, the metal strip s of the CPW are encapsulated in thin films of Si dioxide. Many test s ets were fabricated with different line dimensions, all on p-type subs trates with resistivities in the range from 0.4 Omega . cm to 12.5 Ome ga . cm. Propagation constant and characteristic impedance measurement s were performed at frequencies from 0.1 to 40 GHz, using a vector-net work analyzer and the through-reflect-line (TRL) deembeding technique. A quasi-TEM equivalent circuit model was developed from the available process parameters, which accounts for the effects of the electromagn etic fields in the CPW structure over a broad frequency range. The ana lysis was based on the conformal mapping of time CPW multilayer dielec tric cross section to obtain accurate circuit representation for the e ffects of the transverse fields.