Analysis of probe current in scanning electron microscopy

Probe current means an electron beam focused on a specimen. Working with the specimen, probe current emits electrons containing information on the specimen such as secondary electrons and backscattered electrons. The size of probe current determines the number of secondary electrons and backscattered electrons emitted. Probe current is determined by the size of the probe, which is directly related with the number and size of apertures and the control current of the condenser lens. In case of SEM that acquires images using secondary electrons, if the size of probe current is large, the brightness of images is high but their resolution is low. On the contrary, if the size of probe current is small, the resolution of images is high but their brightness is low. Thus, probe current should be decided suitably for specimens to be observed. The present study attempts to measure probe current for images obtained using designed aperture and the control current of the condenser lens, and utilize the measurements as model data for improving the assembly state of the columns and the quality of images and for designing the control current of lenses.