Patent Number: 045256292
Section: abstract

A deflective focusing system includes a magnetic lens for focusing a charged particle beam, a plurality of rings made of magnetic material arranged substantially concentrically with the magnetic lens inside of the magnetic lens, the rings being arranged at spaced apart positions in the direction of the central axis of the magnetic lens so as to form a predetermined magnetic focusing field distribution, a one-stage electrostatic deflector having a plurality of deflection electrodes which are spaced apart in a circumferential direction of the magnetic lens, which are arranged substantially concentrically with the magnetic lens inside of the magnetic lens, and which extend in the direction of the central axis so as to form a predetermined electrostatic deflection field distribution, so that the charged particle beam passes through the concentrically arranged deflection electrodes to be deflected in accordance with a voltage applied to the deflection electrodes, and ring-like grounding electrodes disposed substantially concentrically with the magnetic lens on the object plane side and the image plane side of the electrostatic deflector along the passage of the charged particle beam. The electromagnetic field is adjusted by the deflector, the rings and the grounding electrodes to obtain small aberrations and a small landing angle.