Parametric study of the loss characteristics of PZT-based MMIC transmission lines

This paper describes the material parameters which affect high frequency transmission lines built on ferroelectric lead zirconate titanate (PZT) thin films. The electrical characteristics of two transmission line (TL) structures, namely microstrip (MS) and coplanar waveguide (CPW), were studied over 1 to 20 GHz using electromagnetic simulation and verified through measurement. The characteristics were studied by simulating the insertion loss of the lines by varying tan δ of the films and the width of the transmission lines. The length of the line was set constant at 100 μm and its thickness 0.1 μm, the PZT thickness was 0.5 μm. The relative permittivities of PZT used for MS and CPW were 87 and 112, and tan δ = 0.1 and 0.09, respectively. The dielectric properties of the PZT films were obtained from capacitance measurement over the said frequency range. Results of this study show that the structures exhibit similar performance, with MS showing the lowest loss for all given widths. These results indicate the possibility of using PZT as a dielectric material for MMIC.