| 摘要 |
PURPOSE:To prevent the etching of an aperture mask and improve the working rate by making a mask closest to an ion generation source replaceable and restricting beam current and then forming the aperture diameter of the mask slightly larger than the beam diameter. CONSTITUTION:The first aperture mask 21 for limiting a beam is supported by a holder 22 and is retained in an ion beam cylindrical optical mirror. This aperture mask 21 can easily be removed from the cylindrical optical mirror along with the holder 22 and can easily be replaced with a new one. Besides, the second aperture mask 23 is arranged. This mask 23 is used as only a target when the alignment of the beam to the optical axis is performed by an aligning electrode 10 and the aperture diameter is formed slightly larger than the beam diameter on the mask 23. As a result, the pollution or etching of the mask by the bombardment of the ion beam can be prevented and the working rate of the ion beam unit can be improved. |
