Cu/Co Multilayer-Based High Signal Integrity and Low RF Loss Conductors for 5G/Millimeter Wave Applications

This paper presents copper/cobalt (Cu/Co) multilayer-based low RF loss conductors and their usage in high signal integrity coplanar waveguide (CPW) transmission lines (TLs) and high Q-factor inductors for the applications of millimeter wave bands including a 28-GHz 5G communication band. Low conductor loss, reduced signal dispersion, and low noise figure of the fabricated devices are featured. CPW (TLs) employing 10 pairs of Cu (150 nm)/Co (25 nm) superlattice conductors, the so-called metaconductors, have been designed and fabricated. Their RF characterization has been performed. Experimental results show a broadband RF resistance reduction of up to 50% (max.) in 7-32 GHz (3.5 Octaves), a phase delay improvement of 25.5%, and a thermal noise voltage reduction of 33% compared to reference Cu-based CPW TLs. In comparison with the devices from the other literature, the presented TLs show the best signal integrity performance in Ku, K, and Ka bands. In addition, a high Q-factor planar inductor on a glass substrate has been designed, fabricated, and characterized as an example of high-performance RF passive components, showing record high Q-factors of 54 at 28 GHz and 63.5 (max.) at 29 GHz.