| 摘要 |
PROBLEM TO BE SOLVED: To provide a charged particle beam optical lens-barrel enabling reduction in contamination within the lens-barrel and precise keeping of orbit of charged particle beam for a long time. SOLUTION: This charged particle beam optical lens-barrel excites each lens so that axial magnetic fields made by adjacent double lens are reversed each other. Positive voltage electrodes 5, 6, 7, 8, 9, 10, 11, 12, 29 are symmetrically arranged around an optical axis between adjacent lens. Secondary electron which is generated when primary electron is made incident into an aperture or a mask is carried along line of magnetic force away from the optical axis and attracted by electric field formed by electrodes to which positive voltage is applied and moved to be absorbed by the electrodes. Accordingly, the secondary electron exisiting near the optical axis is quickly removed, thereby charging can be prevented.
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