Patent ID: 7403265

Claim:
A lithography apparatus, comprising: a projection system that projects a beam of radiation onto a substrate as an array of sub-beams of radiation; a patterning device that modulates the sub-beams of radiation to substantially produce a requested dose pattern on the substrate, the dose pattern being built up from an array of spot exposures in which at least neighboring ones of the spot exposures are imaged incoherently with respect to each other and each of the spot exposures is produced by one of the sub-beams of radiation at a particular time; a low-pass filter that operates on pattern data derived from the requested dose pattern in order to form a frequency-clipped target dose pattern that predominantly comprises only spatial frequency components below a selected threshold frequency; and a data manipulation device that produces a control signal comprising spot exposure intensities to be produced by the patterning device, based on a direct algebraic least-squares fit of the spot exposure intensities to the frequency-clipped target dose pattern.