Charging effects on SEM/SIM contrast of metal/insulator system in various metallic coating conditions

Scanning electron microscope (SEM) and scanning ion microscope (SIM) observations were performed to investigate the charging effect and the related contrast variation for images of conductive and non-conductive specimens under electron and Ga⁺ ion beam irradiations. The contrast variation in the specimens was investigated by changing the coating conditions. It was found that the contrast in conductive specimens was basically caused by differences in atomic number and that the charging effect in conductive specimens is generally smaller than that in non-conductive specimens. On the other hand, the SEM contrast of non-conductive specimens varied widely, depending on the coating conditions. These contrast variations were found to be caused by negative charges accumulated on the surface of die specimens. The SIM contrast of non-conductive specimens changed to dark when the coating condition was insufficient. The contrast variations were found to be caused by the accumulation of positive charges on the surface of specimens,