Patent ID: 8767179

Claim:
An imaging method in scanning photolithography to control CD variation within an exposure field, comprising: splitting a source of electromagnetic radiation into at least two paths; a first of the paths being directed through an exposure slit, then through a reticle, then onto a first longitudinal portion of length of a total exposure field on a photosensitive substrate, the total exposure field on the photosensitive substrate having a maximum total width orthogonal to a direction of scan that is along the length of the total exposure field, the first longitudinal portion extending completely and continuously across the maximum total width of the total exposure field; a second of the paths being directed through an attenuator, then through the reticle, then to a second longitudinal portion of the total exposure field which is different from the first longitudinal portion; the directed first and second paths being spaced from each other along the direction of scan; and applying the attenuated electromagnetic radiation of the second path to selected locations within the total exposure field while scanning all of the total exposure field with the electromagnetic radiation of the first path along the direction of scan.