ELECTRICAL CHARACTERIZATION AND RELIABILITY OF LANTHANUM DOPED PZT THIN FILMS CAPACITORS

Abstract

ABSTRACT The resistance degradation phase of PZT capacitors leakage current is known to be related to the migration of oxygen vacancies species under a constant voltage stress. This phenomenon is associated with an increasing leakage current up to two orders of magnitude, and it is usually attributed to a Schottky barrier height lowering induced by the accumulation of oxygen vacancies at the cathode interface. Waser et al. [1] emphasized the role of oxygen vacancies by correlating the effect of donor doping on the amplitude of the resistance degradation. In the behavioral model of leakage current evolution developed by Zafar et al. [2], the oxygen vacancies concentration can be qualitatively determined by evaluating the maximum barrier lowering at the end of the resistance degradation process. By comparing the amplitude of maximum Schottky barrier lowering at the end of the degradation resistance mechanism between PZT capacitors and PLZT capacitors, this work points out the influence of lanthanum doping on oxygen vacancies concentration. Moreover, the role of oxygen vacancies is also featured by evaluating the reliability behavior: the times to breakdown distribution obtained with PLZT capacitors drifts by a factor of 2.5 in comparison with PZT capacitors. This result tends to demonstrate the role of lanthanum doping on reliability improvement.