Study on Image Drift Induced by Charging during Observation by Scanning Electron Microscope

摘要

The mechanism of image drift in the observation of a boundary between a metal and an insulator by scanning electron microscope (SEM) is clarified by electron-trajectory simulation and experiment. In the region involving a straight boundary between a large-area metal layer and an insulating substrate, the largest image drift is expected to be observed owing to an asymmetric charging on the sample surface. The simulation result shows that a metal-insulator boundary in the SEM image shifts toward the metal part over several seconds, which is induced by a positively charged area outside of the irradiation region in the insulator part. This simulation result is confirmed to qualitatively coincide with the experimental one. In addition, we demonstrate that the direction and magnitude of the image drift can be controlled by changing the charging voltage of the insulating substrate by applying a bias voltage to the anode facing the sample surface.