US Patent 7315351 Lithographic apparatus, device manufacturing method and device manufactured therewith

The invention relates to a lithographic apparatus and a device manufacturing method. The lithographic apparatus is of the scanning type, in which a radiation beam effectively scans across a surface of a substrate. The apparatus comprises a beam attenuator, e.g. in the form of a filter, having an attenuation value profile that varies as a function of position along the scanning direction. Appropriate selection of the attenuation value profile allows the illumination of the substrate to be more homogeneous, since e.g. received dose effects due to pulse to pulse variations in a pulsed illumination source are much better averaged out.