Application of PVD silver for integrated microwave passives in silicon technology

High quality broadband passives are needed to implement MMIC/MIC in silicon. This paper discusses potential benefits of silver metallization to boost the performance of the integrated passive components. Silver is chosen because this metal offers the highest possible electrical conductivity at room temperature. A PVD process was used for silver deposition because this technique meets the requirements of high purity and surface quality. Electromigration, electrochemical migration and agglomeration are not expected to be a problem in silver microwave passives due to the coarse dimensions and low operating current densities encountered in these structures. Ag and Cu coplanar waveguides on silicon substrates were designed, fabricated and tested. Silver waveguides showed a 2–3 dB/cm improvement in attenuation over copper devices at 40 GHz.