Ferroelectric Properties of La0.5Sr0.5CoO3/Pb(Zr0.4, Ti0.6)O3/RuO2 Capacitors

Abstract

As a continuation of the previous studies on Pt/La0.5Sr0.5CoO3/Pb(Zr0.4, Ti0.6)O3/RuO2/SiO2/Si(100) capacitors, the effect of post-annealing conditions of the sputtered-deposited RuO2 bottom electrodes upon crystallization of the PZT(40/60) films and their ferroelectric properties was examined. The switchable polarization (dP=P*-P∧) in the fatigue tests under comparatively low driving voltage amplitudes of 2.0–2.5 V of the PZT films grown on O2- or Ar-annealed RuO2 electrodes continued to be larger than 10 µC/cm2 up to 1010 switching cycles. The fatigue profile generally exhibited gradual degradation with increasing cycles. However, the rates of polarization degradations depended on post-annealing conditions of the bottom electrodes; in the case of O2 annealing, the degradation rate was the lowest (20%) when the annealing temperature was the lowest in the range of 700–800°C. On the other hand, in the case of Ar annealing, the opposite trend was noted. The leakage current density was in the range of 10-6 A/cm2 or less at 2 V, which appeared to be independent of the postannealing condition of the bottom electrode. A possible interpretation of the effectiveness of using the La0.5Sr0.5CoO3 top electrode for the Pb(Zr0.4, Ti0.6)O3 film in suppressing the polarization fatigue has been presented.