| 摘要 |
The invention provides uniform ion dose at the wafer position by varying the current of the ion beam synchronously with the scan. The beam is scanned by a linear scan, and beam scan position information is sent from the beam scan electronics to the beam control circuit connected with the ion source; this information transfer preferably occurs over a fiber optic link to cross the high voltage between the two sets of electronics. At initiation, the beam current is held constant and a Faraday cup is scanned across the beam to measure the variation of dose with scan position. A beam versus scan position waveform is calculated to correct the variation in dose; and the waveform is then loaded into a memory in the ion beam control circuit. The ion beam control circuit then varies the output of the ion source synchronously with the scan to adjust the dose as a function of scan position, as determined by the waveform. If necessary, repeated measurements and waveform calculations can be made until the dose is uniform.
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