2020 年 18 巻 p. 106-109
It is known that insulating films charge up positively or negatively under electron beam irradiation. The potential distribution produced at the specimen surface can be measured by our homemade electrostatic force microscope installed in a scanning electron microscope. A global charging, found within several mm from the irradiation area is made by fogging electrons, which are generated by multiple backscattering events between the specimen and the objective lens plate. Since the most of the energy of fogging electrons is less than 5 eV, the global charging can be suppressed at the specimen by applying −5 V to the specimen. On the other hand, the local charging at the irradiation point shows a positive charging in a small dose, but as the dose increases a negative charging is obtained. By increasing the dose further, a positive charging is found. We found two non-charging conditions of insulating film under electron beam irradiation.
