Abstract: The invention relates to a method for determining lens errors in a Scanning Electron Microscope, more specifically to a sample that enables such lens errors to be determined. The invention describes, for example, the use of cubic MgO crystals which are relatively easy to produce as so-called ‘self-assembling’ crystals on a silicon wafer. Such crystals have almost ideal angles and edges. Even in the presence of lens errors this may give a clear impression of the situation if no lens errors are present. This enables a good reconstruction to be made of the cross-section of the beam in different under- and over-focus planes. The lens errors can then be determined on the basis of this reconstruction, whereupon they can be corrected by means of a corrector.

Abstract: The invention relates to an apparatus for evacuating samples. A sample 4 is hereby placed in a cavity 3 of a sheet 1 with a smooth surface 2. A sole plate 5 Is placed upon this smooth surface 2, whereby the smooth surface 2 and the sole plate 5 placed thereupon together form a vacuum seal. The sole plate 5, upon which a vacuum column 6 is mounted, can be slid across the smooth surface 2. By sliding the sole plate 5 over the cavity 4, the cavity 4 is evacuated in several steps. In an embodiment of the invention, the vacuum column 6 takes the form of an ESEM (Environmental Scanning Electron Microscope). In this way, it is possible to inspect the evacuated sample 4 with the ESEM.