High-Q broadband passives are needed for monolithic microwave circuits in silicon. Coplanar waveguides (CPWs) provide an effective way to implement passives in silicon monolithic microwave integrated circuits. Silver "fat" wires in the backend interconnects, used for CPW fabrication, will reduce the bulk resistive loss in metallization to the lowest possible level, which is vital to minimize noise. Electromigration, electrochemical migration, and agglomeration issues are not a problem for silver microwave passives, because of their coarse dimensions and the low current densities encountered in these structures. In this letter, Ag and Cu CPWs were designed, fabricated and tested. Silver CPWs showed a 2-3 Ω/cm improvement in resistance over copper devices at 20 GHz. A circuit was identified in which the application of silver passives could provide an improvement in noise performance.

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IEEE Electron Device Letters
Department of Electronics

Levenets, V.V., Amaya, R, Tarr, N.G, Smy, T, & Rogers, J. (2005). Characterization of silver CPWs for applications in silicon MMICs. IEEE Electron Device Letters, 26(6), 357–359. doi:10.1109/LED.2005.848120