Hybrid cylindrical radial superlattice conductor-based air-lifted RF inductors with ultra-high quality factor for UWB and K-bands

Abstract

This paper reports the state-of-the-art air-lifted radio frequency (RF) inductors made of hybrid cylindrical radial superlattice (h-CRS) conductors with a gold core featuring ultra-high quality factor (Q-factor) in ultra wideband (UWB) and K-bands. A CRS conductor is made of paired Cu/NiFe layers with a thickness of each pair of 150 nm/25 nm, respectively, using a DC/RF sputtering thin film deposition process. The negative permeability of NiFe thin films above their ferromagnetic resonance frequency is used to cancel the eddy currents inside conductors and reduce the conductor loss in Ku and K-bands. The directional thin film deposition aspect of the used fabrication method for the CRS conductors results in a hybrid conductor structure comprising both solid and multi-layer superlattice parts leading to dual-band high-Q characteristics in UWB and K bands. The intrinsic radial shape of the utilized CRS conductors with the uniform and closed boundaries make them superior for the super compact RF low loss conductors. In result of using CRS conductors with ultra-thin layers and the air-lifted structure with suppressed dielectric losses, a record-breaking Q-factor of greater than 80 at 20 GHz is achieved for 1.8 nH inductors.