Micromachined coplanar waveguides in CMOS technology

Coplanar waveguides were fabricated in standard complimentary metal-oxide semiconductor (CMOS) with postprocessing micromachining. ICs were designed with commercial CAD tools, fabricated through the MOSIS service, and subsequently suspended by maskless top-side etching. Absence of the lossy silicon substrate after etching results in significantly improved insertion loss characteristics, dispersion characteristics, and phase velocity. Measurements were performed at frequencies from 1 to 40 GHz, before and after micromachining. These show improvement in loss characteristics of orders of magnitude. For the micromachined line, loss does not exceed 4 dB/cm. Before etching, loss as high as 38 dB/cm is measured. Phase velocity /spl Gamma//sub p//spl ap/0.8/spl middot/c is achieved for the micromachined line.