Asymmetric Conduction in Thin Film Tantalum/Tantalum Oxide/Metal Structures: Interstitial and Substitutional Impurity Effects and Direct Detection of Flaw Breakdown

Abstract

Asymmetric conduction in a thin film tantalum/tantalum oxide/metal structure depends trongly on the method of preparation of the individual elements as well as the conditions under which the structure is measured. Some of the factors which need to be considered are: (i) gas and alloy metal content of the sputtered tantalum film; (ii) structural perfection of the tanta-lum film; (i/i) nature of the metal counter electrode; and (iv) ambient factors such as the presence of moisture during measurement. The principal results from these investigations can be explained on the basis of flaws in the anodic oxide. Evidence xists, however, that some degree of asymmetric on-duction exists in nominally flaw-free films. Many mechanisms have been proposed to explain the rectifying characteristics of anodic oxide films (1). This asymmetric conduction is known to be quite vari-able and has not been satisfactorily explained in terms