Leakage and reliability characteristics of lead zirconate titanate thin-film capacitors

Resistance degradation in lead zirconate titanate (Pb-(Zr,Ti)O ₃, PZT) thin-film capacitors has been studied as a function of applied voltage, temperature, and film composition. The mean time-to-failure (lifetime, or t _∫) of the capacitors shows a power-law dependence on voltage of the form t _∫ ∝ V ^-n (n = 4-5). The capacitor lifetime also exhibits a temperature dependence of the form t _∫ ∝ exp[E _a/(kT)], with an activation energy of 0.6-1.0 eV. The steady-state leakage current in these samples seems to be bulk controlled. The voltage V, temperature T, and polarity dependence of the leakage current collectively suggest a leakage-current mechanism that is most similar to a Frenkel-Poole process. The t _∫ value and the leakage current of niobium-doped PZT films are superior to those of undoped PZT films. This result can be explained on the basis of the point-defect chemistry of the PZT system. Finally, the results indicate that the niobium-doped PZT films meet essential t _∫ requirements for decoupling-capacitor applications.