Patent ID: 7684038

Claim:
A method for aligning metrology targets comprising: locating a region of interest in substrate layers within which targets may be found; locating a center of symmetry for at least two targets in at least two successive layers; wherein locating the center of symmetry comprises: locating an H-structure target within a substrate layer; locating two regions of interest encompassing two line segments of the H-structure in a first direction; correlating horizontal projections of the regions of interest encompassing the two line segments of the H-structure in the first direction to find the center of symmetry in an X direction; locating one region of interest encompassing a middle line segment of the H-structure in a second direction; and correlating a vertical projection of the region of interest encompassing the middle line segment of the H-structure in the second direction to find the center of symmetry in a Y direction, and adjusting at least one of the substrate's successive layers as to align the center of symmetry for at least two targets in at least two successive layers.