Patent ID: 8115183

Claim:
A method to position a target using a beam of energetic electrically charged particles, comprising: providing a pattern definition means having a plurality of apertures transparent to said particles, illuminating said pattern definition means by means of said beam, which traverses the pattern definition means through said apertures thus forming a patterned beam (pb) consisting of a corresponding plurality of beamlets, forming said patterned beam into an image on the location of the target, said image comprising the images of at least part of the plurality of apertures, said images of apertures having a first width (w), and at least part of the beam impinging on markers provided on the target which then produce secondary radiation, moving the target relative to the pattern definition means along a path within an image plane in which the images of apertures are formed, wherein the relative movement of the target covers a distance of advance greater than the first width as measured on the target, measuring said secondary radiation by a detection system with a suitably high sampling rate, and adjusting the position of the target in a manner that the secondary radiation as measured obtains an extremal (maximum or minimum) value.