| 摘要 |
A scanning beam instrument, such as a scanning electron microscope has a beam column (2) which generates a beam of charged particles which are focussed on a specimen (6) in a specimen chamber (4). Charged particles from the specimen (6) and the vicinity of the specimen are detected by a suitable detector. In one aspect, an arrangement is disclosed in which a magnetic field is generated (70, 72) in the vicinity of the specimen and magnetic shielding is provided in the specimen chamber (4) for containing the field. The magnetic field may be substantially parallel to the surface of the specimen (6) and may also be substantially perpendicular to the axis of the beam (8). In another aspect an electric field is generated (54, 56) substantially parallel to the surface of the specimen (6), and preferably substantially perpendicular to the axis of the beam (8), this electric field is crossed with the magnetic field, and the detector has an electrode (54) substantially perpendicular to the surface of the specimen. In another aspect, the electric and magnetic fields are such as to direct charged particles from the specimen and the vicinity of the specimen to the perpendicular detector electrode (54). |
