Accelerated lifetime measurements on thin film ferroelectric materials with a high dielectric constant

This paper discusses the investigation of thin film ferroelectric capacitors (high-K) with respect to resistance degradation. Accelerated lifetime tests under elevated temperatures of 210-290degC and dc fields of 25-250 kV/cm were performed on these high-K capacitors. The capacitors were studied, making use of the lifetime specifications for ceramic multi-layer capacitors. The increase of the current density by one order of magnitude is here defined as the lifetime of the capacitors. The capacitor under these conditions is still functioning and therefore this is not the lifetime as determined by a breakdown. The accelerated lifetime measurements are used to investigate activation energies and voltage dependences, to enable the extrapolation of the lifetime to operation conditions. It was found that the resistance degradation of these thin film capacitors is a thermally activated process. Activation energies of 1.1-1.6 eV have been determined. An activation energy dependence on the voltage (E_act* = E_act-f₂*V) has been fitted. For the voltage dependence of the lifetime an exponential dependence has been found.