Patent ID: 7253424

Claim:
An ion implanter comprising: an ion beam generator producing an implant beam having a predetermined beam flux of a desired atomic species, a substrate holder for holding a substrate to be implanted, mechanical scanning apparatus operable to translate a substrate on the holder in a translation direction transverse to the beam direction to produce at least one pass of the beam over the substrate, and to mechanically reciprocate the substrate transversely to said translation direction and transversely to the beam direction, to produce a plurality of scans of the beam over the substrate during each said pass, whereby said scans draw on the substrate a raster of lines having mid-points which have a predetermined spacing in said translation direction, and whereby said raster provides an implanted dose of said atomic species over the substrate, said implanted dose having a uniformity in said translation direction which includes a uniformity component which is a function of said predetermined spacing, a beam profiler to measure the cross-sectional profile of the ion beam at least in said translation direction, and a controller for said scanning apparatus to calculate from said profile a maximum value of said spacing of said mid-points which provides a desired value of said uniformity component, and to control said translation of the substrate to select a value of said spacing which does not exceed said maximum value.