Patent ID: 9747682
Date: 2017-08-29
CPC Classifications: G03F,G06T,H04N

Claim:
1. A method for measuring overlay, the method comprising: receiving a first image of a first overlay mark selectively captured using light having a first wavelength in a first step; receiving a second image of a second overlay mark selectively captured using light having a second wavelength different from the first wavelength in a second step different from the first step; and measuring a displacement between a central portion of the first image and a central portion of the second image, wherein the first and second overlay marks are disposed on different levels, wherein: the first overlay mark comprises a plurality of first zones comprising a first pattern disposed along an x direction, a second pattern disposed along a y direction, a third pattern disposed along the x direction and a fourth pattern disposed along the y direction, wherein the first through fourth patterns are rotationally symmetric around a center of the first overlay mark, and the second overlay mark comprises a plurality of second zones comprising a fifth pattern disposed along an x direction, a sixth pattern disposed along a y direction, a seventh pattern disposed along the x direction and an eighth pattern disposed along the y direction, wherein the fifth through eighth patterns are rotationally symmetric around a center of the second overlay mark, and wherein the first overlay mark and the second overlay mark are each positioned in a single continuous layer separating the first overlay mark from the second overlay mark.