Profile of dielectric properties in anodic oxide film of tantalium

A method to analyze the uniformity of electrical properties of anodic tantalum oxide layers is described. It is based on a chemical etching by aqueous solution of HF and NH4F, which is used at the same time as an electrolyte in order to carry out the electrical measurements. It has been found that the anodic layers show an important variation of dielectric properties during the dissolving process. The zone near to the oxide/electrolyte interface shows generally good dielectric behaviour, while the inner zone presents an important level of conduction, which is explained by the presence of tantalum suboxides. (Author)