Localization of weak points in thin dielectric layers by Electron Beam Absorbed Current (EBAC) imaging

A novel approach for the localization of weak points in thin transistor and capacitor oxides before electrical breakdown will be presented in this paper. The proposed approach utilizes Electron Beam Absorbed Current (EBAC) imaging based on Scanning Electron Microscopy (SEM). This technique uses the generation of additional charge carriers within the semiconductor substrate level by scanning with a focused electron beam. Over a thin transistor or capacitor oxide layer inside the interaction volume of the electron beam an increased tunnel current is visualized by EBAC and shows areas with different current intensities indicating weak points. These soft defect areas are investigated in comparison to references which were analyzed by using cross sectioning in a dual beam FIB/SEM system followed by a high resolution Transmission Electron Microscopy (TEM) investigation. The feasibility of this new technique is demonstrated on a defective transistor gate oxide test structure.