Microwave properties of PZT/ZrO2 thin films for RF MEMS capacitive shunt switches

The use of PZT as a dielectric for RF MEMS shunt switches to improve the RF performance is investigated. Currently, the dielectric properties of PZT at microwave frequencies are not fully characterized. Thus ungrounded coplanar waveguide (CPW) transmission lines were designed and used to characterize microwave dielectric properties of PZT/ZrO2 combined-layer dieleciric on high resistivity Si substrates. Phase variations oYer the frequency range from 1 to 20 GHz were extracted using measured S-paråmeters. Dielectric properties of lhe PZT/ZrO2 fiIms were extracted using propagation time delay directly measured from vector network analyzer together with a conformal mapping model (CMM) based coplanar waveguide model. In this study, a frequency independent dieleciric constant value of about 148 and loss tangent of about 0.62 at 20 GHz were measured for PZT/ZrO2 combined-layer dielectric.