Ion implantation uniformity correction using beam current control

Abstract

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.

Dependencies are inferred from the claim text.