Application of on-wafer TRL calibration on the measurement of microwave properties of Ba0.5Sr0.5TiO3 thin films

Abstract

A series of Al/Ba0.5Sr0.5TiO3 (BST)/sapphire multi-layered coplanar waveguide (CPW) transmission lines of different geometries and thin-film configurations was fabricated. We employed an accurate on-wafer Through-Line-Reflect (TRL) calibration technique and quasi-TEM analysis to measure the dielectric constant, loss tangent, and tunability of BST thin films using this CPW structure. Experimental results show that the overall insertion loss is less than 3 dB/cm even at frequencies as high as 20 GHz, which is the lowest obtained to date for metal/BST CPW devices. This result indicates that, with optimized impedance matching, normal conductors are also possibly suitable for fabricating low-loss tunable phase-shifter devices.