Effect of the Focusing of a SEM Probe on the Formation of Relief Structure Images

The effect of focusing a scanning electron microscope probe on the formation of relief structure images is studied in secondary slow electron and backscattering electron collection modes. Protrusions and grooves in silicon with a trapezoidal profile and large inclination angles of lateral walls are used in the experiments. In the defocusing process the probe diameter is increased up to 8 times. It is shown that the image obtained in the secondary slow electron mode greatly varies, while the image acquired in the backscattering electron mode remains unchanged within the noise. The areas of signals strongly affected by the SEM probe are specified as well. According to the results, SEM focusing is necessary for only the secondary slow electron collection mode.