Local impedance and microchemical analysis of electrical heterogeneities in multilayer electroceramic devices

We present an experimental methodology for locating and studying local failure sites in multilayer electroceramic devices at the submicron-length scale. In particular, the inhomogeneous degradation of multilayer ceramic capacitors is studied using a judicious combination of scanning electron microscopy (SEM), local-probe electrical measurements, focused ion beam (FIB) extraction, and transmission electron microscopy (TEM). Voltage-contrast SEM permits the identification of regions of different electrical potential within degraded multilayer devices. The local impedance from specific regions is measured in situ between a tungsten probe and the internal device electrodes, while impedance spectra are extracted for more detailed analysis. Because implementation occurs in dual-beam FIB/SEM, these locally defective sites can be extracted and thinned to electron transparency for further investigation by TEM. In this study, degraded sites in BaTiO₃ multilayer capacitors are found to be associated with local oxygen deficiencies in BaTiO₃, as measured by electron energy loss spectroscopy.