Identification of electron beam vibration sources by separation of magnetic distortion from electric distortion on...

Different types of distortions in scanning electron microscopy require different methods of their elimination, and therefore influence of these types on particular elements of the SEM system should be known. The proposed method allows for separation of the direct influence of the magnetic field on the electron beam in the SEM chamber from its influence in the SEM column and from the distortions generated in the SEM scanning block. For this purpose, a series of distorted images is registered for several working distances (between the final aperture of the electron column and the specimen) and for several energies of the electrons. Magnitudes of the distortions are measured on these images. For each applied electron energy, the dependence of the results versus the working distance is approximated with the second-order polynomial function. The analysis of the polynomial coefficients allows for the separation of the above-mentioned kinds of distortions. The presented method enables a selection of the most efficient solution to the distortions reduction. It utilizes the SEM itself and does not need any additional equipment.