Low-frequency measurements and modelling of MLC capacitors

A model based on electron trapping at electrode-ceramic interface states predicts a t^-n dependence for leakage current. The model has two requirements: that the trap filling rate be proportional to the density of empty traps, and that the interface by inhomogeneous (patchy), so that the active area (i.e. the area with unfilled traps) decreases with time. Near room temperature (≲75°C) the model predicts that n should be near unity, capacitance should decrease logarithmically with time and be dispersion free, and conductance should increase linearly with frequency. As conduction current becomes significant (at temperatures above about 100°C), the model predicts that n should approach zero, conductance dispersion should decrease to zero, and low-frequency capacitance should vary inversely with frequency. The decay parameter n is predicted then to vary linearly with time and voltage and exponentially with temperature. All of these predictions are more or less confirmed by measurements made on commercial X7R, Z5U, and Y5V multilayer ceramic (MLC) capacitors, with agreement for Y5V being very good. Such low-frequency dispersion is similar to that seen for GaAs Schottky diodes with a damaged metal-semiconductor interface