Estimation of the diameter of a SEM beam by video-signal curves from a trapezoidal Structure: 2. Experiment

Abstract

The main sources of systematic error in measurements of SEM-beam diameter are revealed. The reasons for the occurrence of error in measurements using a relief structure with a trapezoidal profile are studied. One of the most important causes of the error is selection of the ratio between the height of the relief structure and the focal depth of the SEM; another cause is related to the modification of raw SEM images of the structure, measured in the form of a video-signal curve, necessary for the used method of measurement of the beam diameter. These can lead to systematic errors in the hundreds of (and even up to a thousand) percent. Most of the other causes of error occur at the stage of the formation of a beam of electrons emitted by the surface of the structure and forming the video signal. These errors arise due to imperfection of the calculation model of low-energy secondary electron emission near the edge of the structure and some significant quantities of edge variation due to poor technological reproducibility. The contribution of these sources to the relative error was approximately 100%. Ways of eliminating the systematic error are proposed.