Some Factors Controlling Gross Leakage Currents in Sputtered Tantalum-Film Capacitors

Methods for producing sputtered tantalum‐film capacitors are described. The breakdown voltage of such capacitors is shown to depend on the type of metal used for the counterelectrode and on the counterelectrode area. This dependency is explained as being due to microfissures (in the oxide), which some metals are more likely to enter than others. Electron micrographs of these fissures are shown. The origin of the microfissures is thought to be lattice mismatch between oxide and metal in those regions where the original tantalum was not sufficiently smooth. It is suggested that anodizing these films in hot solutions will establish a thermal mismatch between metal and oxide, which will partly compensate for the lattice mismatch.