Overlay metrology target
In one embodiment, a metrology target for determining a relative shift between two or more successive layers of a substrate may comprise; an first structure on a first layer of a substrate and an second structure on a successive layer to the first layer of the substrate arranged to determine relative shifts in alignment in both the x and y directions of the substrate by analyzing the first structure and second structure overlay.
1. A metrology target for determining a relative shift between two or more successive layers of a substrate comprising:
a first structure on a first layer of the substrate, wherein the first structure comprises:
two parallel line segments separated by a known distance;
a third line segment connecting the two parallel line segments starting from the midpoint of each of the two parallel line segments and resulting in a third line perpendicular to the two parallel line segments,
wherein no other line segments on the first layer intersect any of the two parallel line segments and the third line segment,
a second structure on a successive layer to the first layer of the substrate;
wherein:
centers of symmetry for the first structure and second structure are designed to be placed in coincidence and shifts from this coincident placement may be read as substrate layer shifts; and
the first structure and the second structure have 180 degree symmetry.
2. A metrology target for determining a relative shift between, two or more successive layers of a substrate comprising:
a first structure on a first layer of the substrate, wherein the first structure comprises:
two parallel line segments separated by a known distance;
a third line segment connecting the two parallel line segments starting from known points, wherein the known points are closer to one end of a line segment than to a line segment's second end, on each of the two parallel line segments and resulting in a third line perpendicular to the two parallel line segments,
wherein no other line segments on the first layer intersect any of the two parallel line segments and the third line segment,
a second structure on a successive layer to the first layer of the substrate;
wherein:
centers of symmetry for the first structure and second structure are designed to be placed in coincidence and shifts from this coincident placement may be read as substrate layer shifts; and
the first structure and the second structure have 180 degree symmetry.