Patent ID: 7550740
Filing Date: 2009-06-23
Classification: H01J

Abstract:
1. A focused ion beam apparatus for focusing an ion beam on a sample to process and/or observe the sample, the apparatus comprising: a corrective magnetic field generating unit disposed on the optical axis of the ion beam for producing a corrective magnetic field to correct the deflection of the ion beam due to the influence of an external magnetic field outside the focusing ion beam optical system, wherein the corrective magnetic field generating unit comprises two pole-piece pairs, each of which consisting of two pole pieces disposed adjacent to each other with a gap d, wherein the two pole-piece pairs are disposed opposite to each other across the optical axis of the ion beam, with a gap g which is greater than gap d, the corrective magnetic field generating unit further comprising: an internal coil wound on each of the four pole pieces; and an external coil wound on each of the two pole-piece pairs in such a manner as to surround the internal coils.