Symmetric target design in scatterometry overlay metrology

A metrology target comprising:

• at least three cells, wherein the at least three cells comprises a first cell, a second cell, and a third cell, wherein the first cell comprises a first parallel periodic structure disposed at a first layer, wherein the second cell comprises a second parallel periodic structure disposed at a second layer, and the third cell comprises a third parallel periodic structure disposed at a third layer, wherein the first layer is different from the second layer and the third layer, wherein the second layer is different from the third layer, wherein each of the first parallel periodic structure, the second parallel periodic structure and the third parallel periodic structure include a same pitch,
• wherein the pitch of the first parallel periodic structure, the second parallel periodic structure, and the third parallel periodic structure is uniform across each of the first parallel periodic structure, the second parallel periodic structure, and the third parallel periodic structure,
• wherein a perimeter of the metrology target is defined by one or more cell edges, wherein at least one of the first parallel periodic structure, the second parallel periodic structure, or the third parallel periodic structure is disposed within the perimeter of the metrology target such that it is central with respect to the one or more cell edges,
• wherein the pitch of the first parallel periodic structure and the pitch of the second parallel periodic structure is uniform across the first cell,
• wherein the first cell overlaps with at least one of the second cell or the third cell,
• wherein the first cell, the second cell, and the third cell are individually invariant with respect to a selected rotational transformation about an axis perpendicular to at least one of the first cell, the second cell, or the third cell.