An Evaluation for the Depth of Field in SEM Image Depending on Accelerating Voltage

The dependence of the depth of field In a scanning electron microscope (SEM) image on the accelerating voltage is presented. The depth of field depends on the accelerating voltage of the primary beam and on the signal-to-noise ratio of the image if it is evaluated by calculating the image resolution along the optical axis defined in terms of the information passing capacity (IPC) of an optical system. The IPC corresponds to the mean information content included in an optical image, i.e., the quality of the image, evaluated based on the theory of Linfoot. The calculated result has agreed well with the experimental result.