| 摘要 |
<p>In an SEM it is desirable, in given circumstances, to acquire an image of the sample (14) by means of Auger electrons extracted from the sample and traveling back through the bore of the objective lens (8) in the direction opposing the direction of the primary beam. It is known to separate extracted electrons from the primary beam by positioning Wien filters (32, 34) in front of the objective lens (8), the filters being energized in such a way that they do not cause deflection of the primary beam but do defect the secondary electrons. This technique cannot be used for Auger electrons, considering their high energy and hence much stronger fields in the Wien filters, thus causing substantial imaging aberrations in the primary beam. According to the invention a quadrupole field is applied in the same position as the fields of each Wien filter (32, 34, 36), thus ensuring that the resolution of the image of the sample (14) is not degraded by the fields of the Wien filters.</p> |
