Electrode Dependences of Switching Endurance Properties of Lead-Zirconate-Titanate Thin-Film Capacitors

Switching endurance properties of lead-zirconate-titanate thin-film capacitors with gold, platinum and iridium top electrodes were investigated using a pulse switching characterization technique. Lead-zirconate-titanate capacitor structure formed with Ir top and bottom electrodes exhibited superior switching endurance to Au/PZT/Ir and Pt/PZT/Ir capacitors. The difference between switched and nonswitched polarizations of an Ir/PZT/Ir capacitor reversed by bipolar pulses was more than 38 µ C/ cm2 after 2×109 switching cycles. Nonswitched polarization of this capacitor for negative read-pulses decreased gradually with increase in the number of switching cycles. When positive and negative unipolar pulses, and DC biases were applied to the top electrodes of Pt/PZT/Ir and Ir/PZT/Ir capacitors, remanent polarizations of each capacitor were not changed significantly. However, nonswitched polarizations for negative read-pulses decreased with increase in the number of negative unipolar pulses applied or DC bias application time. Drastic decrease in remanent polarization of a Pt/PZT/Ir capacitor was caused only by bipolar pulse application. The reduction of nonswitched polarization for negative read-pulses suggested the formation of depletion-layer capacitances at the interfaces between top electrodes and PZT layers.