Coulomb blur in a multi-electron-beam system with a single column was investigated by simulations and experiments in 1024 two-dimensional electron beams with double lens-doublet optics. Monte Carlo simulation showed three main points. First, in spite of a high current density, Coulomb blur and energy broadening were the same as those in the case of a shaped beam covering a multi-electron-beam area. The Coulomb blur for a electron beam at total beam current was simulated as , which was less than half of that in the case of a single beam. Second, the Coulomb blur is slightly nonuniform depending on the distance from the beam center. Third, the decrease in the Coulomb blur by beam blanking is similar to that by beam absence at the objective plane. In addition, Coulomb blurs of the axial beam were estimated by experiments at various currents. The results show that the experimental blurs were in good agreement with the simulated blurs. In conclusion, the authors clarified that multiplying the number of beams is effective for decreasing Coulomb blur at the same total current.
Munro’s Electron Beam Software Ltd., London, England.