METHOD AND SYSTEM FOR AUTOMATICALLY CORRECTING ABERRATIONS OF A BEAM OF CHARGED PARTICLES

摘要

METHOD AND SYSTEM FOR AUTOMATICALLY CORRECTING ABERRATIONS OF A BEAM OF CHARGED PARTICLES The location of a beam of charged particles within a deflection field is determined by its orthogonal deflection voltages. With the location of the beam in the field, correction currants are supplied to a focus coil and to each of a pair of stigmator coils to correct for change of focal length and astigmatism due to the beam being deflected away from the center of its deflection field.