초록 ▼

In a 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

In a 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 deflect 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.

대표청구항 ▼

1. A particle-optical apparatus which includes:a particle source for producing a primary beam of electrically charged particles which travel along an optical axis (4) of the apparatus, a sample holder (20) for a sample (14) to be irradiated by the primary beam, a focusing device (8) for forming a fo

1. A particle-optical apparatus which includes:a particle source for producing a primary beam of electrically charged particles which travel along an optical axis (4) of the apparatus, a sample holder (20) for a sample (14) to be irradiated by the primary beam, a focusing device (8) for forming a focus of the primary beam having a plurality of energy levels in the vicinity of the sample holder (20), at least two Wien filters (34, 36) which are arranged between the particle source and the focusing device (8), wherein means (58, 66, 68) for generating a quadrupole field, said means being arranged at an area of each of the respective said at least two Wien filters so that at least a part of each respective quadrupole field coincides with a field of the associated Wien filter.