TEMPERATURE DEPENDENT FATIGUE RATES IN THIN-FILM FERROELECTRIC CAPACITORS

A series of fatigue measurements have been performed on PZT capacitors over temperatures ranging from 78K to 423K. The polarization loss is approximately proportional to the logarithm of the number of fatigue cycles, but the fatigue rate shows a strong temperature dependence, particularly at low temperatures. The capacitors fatigue very little at 78K but fatigue rapidly at room temperature. The temperature dependence of the fatigue rate fits an Arrhenius function with an activation energy of 0.043 eV. This data does not support the common interpretation that logarithmic decay results from an aggregate of exponentially decaying species uniformly distributed in activation energy. An alternative model is proposed that attributes fatigue to the formation of opposing domains to relieve the Coulombic and stress energy of charged defects. The result is stable defect/domain structures that resist electrical switching. The observed activation energy is presumed to pertain to the transport of electronic charge necessary to form stable opposing domains.