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

摘要

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(sub f)) of the capacitors shows a power law dependence on applied voltage of he form t(sub f) (proportional to) V(sup (minus)n) (n (approximately) 4--5). The capacitor life-time also exhibits a temperature dependence of the form t(sub f) (proportional to) exp(E(sub a)/kT), with an activation energy of (approximately) 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 life-time and leakage current of the Nb-doped PZT films are superior 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.