Use of electron beam scanning electron microscopy for characterization of a sidewall occluded from line-of-sight of the electron beam

摘要

A semiconductor device is scanned by an electron beam of a scanning electron microscope (SEM). The area includes a three-dimensional (3D) feature having a top opening and a sidewall. The 3D feature is imaged while varying an energy value of the electron beam. The electron beam impinges at a first point within a selected area of the semiconductor device and interacts with the sidewall, wherein the first point is at a distance away from an edge of the top opening. Based on change in a signal representing secondary electron yield at the edge as the energy value of the electron beam is varied during the SEM imaging, it is determined whether the sidewall is occluded from a line-of-sight of the electron beam. A slope of the sidewall may be determined by comparing measured signals with simulated waveforms corresponding to various slopes.