Characterization of AlN and AlScN thin films CPW Transmission on High-Resistive Substrates

This article describes a coplanar waveguide (CPW) with a stacked structure of metal, piezoelectric thin film, and high resistance substrate, which can be used for on-chip interconnection of piezoelectric acoustic devices. The performance of CPW on AlN and AlScN platforms is influenced by the effective dielectric constant and parasitic conductivity of the substrate. There is no parasitic conductivity at the interface between AlScN and Si, so etching will cause a decrease in the effective dielectric constant. The performance of AlN CPW has significant losses due to parasitic conductivity effects. By etching, AlN-CPW removes parasitic conductivity effects and the transmission loss can increase from -0.4 dB/mm to -0.3 dB/mm.