Lithographic print bias/overlay target and applied metrology

摘要

A print bias target is imaged in a single layer of light-sensitive material. The print bias target is made up of a pair of concentric geometric shapes in which a plurality of target regions forms a plurality of isolated edges. Each target region is of a different image structure than each other target region immediately adjacent thereto. The positioning of a given isolated edge in the print bias target is determined relative to a corresponding isolated edge in the design image from which the print bias target was imaged. Focus setting and/or exposure setting for a lithographic system to minimize print bias may be determined using print bias information obtained from a print bias target matrix of varying exposure and focus. An imaging aberration may also be identified using print bias information from a print bias target matrix, such as lithographic astigmatism, lithographic coma and vibration. A slope of an imaging profile may also be determined from print bias information. Overlay may be determined by imaging a print bias target on top of a prior level image to create an overlay target, determining a center of the prior level image, determining an average center of the print bias target and determining a location of the average center relative to the prior level image center, thereby determining the overlay.