Separation of dynamic current-voltage characteristics (DCVCs) of an oxide film from the DCVC of ionic currents in a metal/oxide/semiconductor structure: Universal quasi-static DCVCs of a film

Abstract

Analytic results for a quasi-equilibrium distribution of mobile ions in an oxide film contained in a metal/oxide/semiconductor (MOS) structure, as well as formulas for the concentration of ions at the center of the film and on its boundary and formulas for the ionic centroid, are reviewed. Thresholds for the emergence of a U-shaped distribution of ions with characteristic accumulation of ions near the film’s boundary (segregation of ions) are analyzed; the case of a half-space is considered as well. A method to determine the dynamic current-voltage characteristic (DCVC) of the film’s ionic currents is proposed. This method uses an experimental DCVC of the entire structure and a quasi-equilibrium (low-frequency) electronic voltage-capacitance characteristic of the structure. The film’s DCVC has to be separated to eliminate masking effects of the semiconductor’s capacitance on the structure’s DCVC. An analytic method for calculation of the film’s quasi-static DCVC is developed for a model of a homogeneous film. When expressed in dimensionless units, such DCVCs, which are shown to depend on only the dimensionless concentration of ions in the film (per unit area), prove to be universal functions. The population of ionic traps on the film’s boundary is described using the energy Gibbs distribution of ions. The presence of traps is shown to result in the emergence of an additional “trap” peak on the film’s DCVC only if the concentration of traps is low; when this concentration is large, a single peak is observed on the DCVC.