Patent ID: 9007585
Filing Date: 2015-04-14
Classification: G03F,H01L

Abstract:
1. An imaging overlay metrology target, comprising: a self-symmetric target structure including two or more pattern elements; and at least an additional target structure including two or more pattern elements, wherein each of the two or more pattern elements of the at least an additional target structure is contained within a boundary defined by one of the two or more pattern elements of the self-symmetric target structure, wherein the self-symmetric target structure is characterized by a composite exterior region of interest, wherein the composite exterior region of interest is formed by removing two or more exclusion zones corresponding with the two or more pattern elements of the at least an additional target structure from an exterior region of interest encompassing the self-symmetric target structure, wherein the two or more pattern elements of the at least an additional target structure are characterized by two or more interior regions of interest, wherein each of the pattern elements of the at least an additional target structure is characterized by an interior region of interest, wherein the two or more interior regions of interest are contained within the exterior region of interest, wherein the self-symmetric target structure and the at least an additional target structure are configured to have a common center of symmetry upon alignment of the self-symmetric target structure and the at least an additional target structure, wherein the self-symmetric structure is invariant to N degree rotation about the common center of symmetry, wherein the at least an additional target structure is invariant to M degree rotation about the individual center of symmetry.