Patent ID: 8741668
Filing Date: 2014-06-03
Classification: G03F

Abstract:
1. A method for measuring overlay from a multidirectional overlay mark, comprising: providing a first structure having a first pattern element; providing a second structure having a second pattern element, wherein the first structure and the second structure have a common center of symmetry, wherein the first structure and the second structure are invariant to a 180 degree rotation about the common center of symmetry, wherein the first structure and the second structure are arranged within a mark region, wherein the mark region is characterized by a first direction and a second direction, the second direction orthogonal to the first direction, a length of the mark region along the first direction being substantially greater than a length of the mark region along the second direction; illuminating the first structure and the second structure with light; collecting light reflected from the first structure and the second structure; and determining overlay error between two or more structures based on the collected light from the first structure and the second structure.