Analysis of the relationship between defect site generation and dielectric breakdown utilizing A-mode stress induced leakage current

The dielectric breakdown mechanism is studied from the viewpoint of the relationship with the generation of defect sites in the oxide film, utilizing the “A-mode” stress induced leakage current (A-mode SILC) under the constant-voltage stressing. It is demonstrated that the breakdown occurs when the A-mode SILC becomes a threshold level, I_th. In spite of that, the constant I_th for various stress fields is expected by the conventional model which assumes that each defect site is generated randomly in the oxide film, I _th, increases with the stress field. To explain this variety of I_th by the stress field, the concept of “breakdown-path creation efficiency” (γ_BPC), is proposed, which represents the amount of defect sites in the whole gate area required to create a breakdown path from one side of oxide film to the other side at a local spot. According to this concept, it is demonstrated that the efficiency becomes smaller with the increase in the stress field. These results require us to take account the nonuniform distribution of defect sites in the oxide film into the model for the breakdown mechanism. The introduction of the stress-field dependent depth profile of defect sites allows to explain the variety of I_th