Patent ID: 6855938
Filing Date: 2005-02-15
Classification: H01J

Abstract:
1. An objective lens for an electron microscopy system with magnetic and electrostatic focusing for inspecting an object positionable in an object plane, comprising: a pole shoe arrangement for generating a focusing magnetic field, which pole shoe arrangement is substantially rotationally symmetric about an optical axis of the objective lens extending in a z-direction and comprises an inner pole shoe and an outer pole shoe, wherein a pole shoe gap is formed between the inner and outer pole shoes at a lowermost position in the z-direction of the inner pole shoe, the pole shoe gap including a gap spacing oriented in the z-direction between the outer pole shoe and the inner pole shoe; a coil body disposed in a space between the inner and the outer pole shoes; and an electrode arrangement for generating a focusing electrostatic field, which electrode arrangement is substantially rotationally symmetric about the optical axis and comprises a beam tube which extends along the optical axis through the inner pole shoe and has a lower end, and a terminal electrode disposed spaced apart from the lower end of the beam tube, wherein, in a region within at least 3 cm around the pole shoe gap, the following applies: wherein the following applies: