Simulation of space charge neutralization using ions in electron beam projection optics

Abstract

We have investigated, using Monte Carlo simulations, space charge neutralization using ions in a 4:1 telecentric doublet electron beam (e-beam) projection optics. The simulations were performed for two extreme conditions; one with ions moving at the same axial velocity as the e-beam, the other with stationary ions. For both conditions, global space charge effects; defocus, field curvature and magnification change are almost completely eliminated. Although the stochastic coulomb interaction is increased the total point spread which determines resolution can be decreased, because of the elimination of space charge induced spherical aberration. This suggests that space charge neutralization can reduce the global space charge effects without inducing unacceptable stochastic effects.