| 摘要 |
A method and apparatus is provided for improving implant uniformity of an ion beam experiencing pressure increase along the beam line. The method comprises generating a main scan waveform that moves an ion beam at a substantially constant velocity across a workpiece. A compensation waveform (e.g., quadratic waveform), having a fixed height and waveform, is also generated and mixed with the main scan waveform (e.g., through a variable mixer) to form a beam scanning waveform. The mixture ratio may be adjusted by an instantaneous vacuum pressure signal, which can be performed at much higher speed and ease than continuously modifying scan waveform. The mixture provides a beam scanning waveform comprising a non-constant slope that changes an ion beam's velocity as it moves across a workpiece. Therefore, the resultant beam scanning waveform, with a non-constant slope, is able to account for pressure non-uniformities in dose along the fast scan direction. |
