Loss behavior of microwave transmission line structures on PZT thin films

This paper presents a continuation of an investigation into the behavior of ferroelectric lead zirconate titanate (PZT) thin films at high frequency through electromagnetic simulation. The electrical characteristics were analyzed on two transmission line (TL) structures namely microstrip (MS) and coplanar waveguide (CPW) built on PZT thin films. The characteristics are studied by investigating the effect of varying the loss tangent of PZT and the width of the transmission lines on the insertion loss of the two TL structures. The length of the line was set at 100 μm and the thickness was 0.1 μm. Different characteristic impedances were set to calculate the difference of width for MS and CPW. The PZT film thickness was 0.5 μm, and the structures were simulated over 1 to 20 GHz. Using ε_r values of 87 and 112 respectively for MS and CPW found earlier from capacitance measurements, the insertion loss (IL) was computed at 10 GHz for various structures. The variations of tan d were simulated to predict their IL. The results were compared with tan d at δ 0.1 and 0.09 taken from the capacitance measurement for MS and CPW. Results of this study show that the structures exhibit similar performance, with CPW showing the lower loss for all given widths. These results show the viability of using PZT as a new dielectric material for microwave integrated circuits.