ABERRATION PROPERTIES OF FOCUSED ION-BEAM INDUCED BY SPACE-CHARGE EFFECT

The ion-beam broadening induced by the space charge effect (SCE) was investigated for conditions relevant to ion beam processes. A Monte Carlo calculation including the effect of lens aberration has been performed. This makes it possible to estimate the beam broadening induced by the SCE following lens aberration changes. Results show that the beam broadening induced by the SCE around the retarding region is less than 8% of the total probe diameter assuming 100 muA/sr of angular current density at the source, 10 eV of energy dispersion, 0.1-10 nA of the probe current, and 0.1-25 keV of landing energy. Results also show that the beam broadening induced by the SCE is more sensitive to angular current density at the source rather than total probe current. The minimum probe diameter at 1 nA of the probe current and 100 eV of landing energy is 0.12 mum at 400 muA/sr of angular current density at the source.