Accelerated life-time testing and resistance degradation of thin-film decoupling capacitors

Resistance degradation in PZT thin-film capacitors has been studied as a function of applied voltage, temperature, and film composition. It is found that the mean-time-to-failure (life-time or t _f) of the capacitors shows a power law dependence on applied voltage of the form t_f∝V^-n (n~4-5). The capacitor life-time also (t_f) exhibits a temperature dependence of the form t_f∝exp(E_a/kT), with an activation energy of ~0.8 eV. The steady-state leakage current in these samples appears to be bulk controlled. The voltage, temperature, and polarity dependence of the leakage current collectively suggest a leakage current mechanism most similar to a Frenkel-Poole process. The Nb-doped PZT films exhibit superior life-time and leakage current to the undoped PZT films. This result can be explained based on the point-defect chemistry of the PZT system. Finally, the results indicate that the Nb-doped PZT films meet the essential requirements for decoupling capacitor applications