| 摘要 |
A grid assembly coupled to a discharge chamber of an ion beam source is configured for steering ion beamlets emitted from the discharge chamber at circularly asymmetrically determined steering angles. The grid assembly includes at least first and a second grid with a substantially circular pattern of holes, wherein each grid comprises holes positioned adjacent to one another. A plurality of the holes of the second grid is positioned with offsets relative to corresponding holes in the first grid. Due to the offsets in the holes in the second grid, ions passing through the offset holes are electrostatically attracted towards the closest circumferential portion of the downstream offset holes. Thus, the trajectories of ions passing through the offset holes are altered. The beamlet is steered by predetermined asymmetric angles. The predetermined steering angles are dependent upon the hole offsets, voltage applied to the grids, and the distance between the grids.
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