SEM PROVIDED WITH AN ELECTROSTATIC OBJECTIVE AND AN ELECTRICAL SCANNING DEVICE

摘要

The detector (6) for the secondary electrons in a SEM provided with an electrostatic objective (14, 16) is arranged ahead of the objective, thus enabling a high detection efficiency. According to the invention, the deflection of the beam is performed electrically and the deflection electrodes (10, 12) are arranged between the detector (6) and the last two electrodes (14, 16) of the objective. The beam deflection is realized by means of two oppositely directed electrical deflection fields in such a manner that the tilting point of the scanning motion is situated at the center (20) of the objective lens, thus avoiding additional lens defects and obstruction of the beam by the limited dimensions of the objective bore. This results in a large field of view, without loss of resolution. Furthermore, deflection by means of two oppositely directed fields has the effect that the paths (24) of the secondary electrons traveling to the detector (6) are shaped such that a larger part thereof reaches the detection material (6).