Patent ID: 6184975
Filing Date: 2001-02-06
Classification: H01J

Abstract:
A particle-optical apparatus which includes:a particle source for emitting a beam of electrically charged particles which travel along an optical axis of the apparatus in order to expose an object, to be irradiated in the apparatus, by means of the particle beam,a focusing lens for focusing the beam of electrically charged particles,and a corrector for correcting the chromatic aberration of the focusing lens,which corrector includes correction elements, each of which is provided with electrodes for producing electric quadrupole fields, said electrodes being arranged in successive layers along the optical axis, the quadrupole fields produced by the electrodes in the layers being rotated through an angle of substantially 90.degree. about the optical axis relative to the quadrupole field produced by the electrodes in an adjacent layer, characterized in thatthe correction elements comprise at least five layers of quadrupole electrodes.