The low-volatage-switching behavior of sol-gel-derived Pb(Zr, Ti)O3 thin film capacitors

Abstract

The improvement in switching performance of ferroelectric Pb(ZrxTi1-x)O3 (PZT) thin film capacitors under a lower applied voltage was investigated. PZT thin films were prepared by a chemical-solution-deposition method. The film thickness decrease was not as effective as expected due to the increased coercive field. Decreases in film thickness also resulted in a substantial increase in leakage current at the operation voltage. The stacked layer of the tetragonal and rhombohedral PZT thin films slightly improved the low voltage saturation behavior of the remanent polarization (Pr). Cation impurities, such as La, Ca and Sr, also assisted in improving the saturation behavior. However, a modification of the stock solution by adding a special chelating agent, which also greatly improved the shelf life of the solution, was the most effective method of improving Pr saturation of the undoped tetragonal PZT film. A 85% Pr saturation was obtained at an applied voltage as low as 1.5 V when the PZT film thickness was 200 run. This was attributed to the more homogeneous distribution of the precursor molecules in the solution thereby resulting more uniform crystallization of the PZT layer during crystallization annealing.