Patent ID: 8084872

Claim:
An overlay mark, comprising: four regions that are arranged in a 2×2 array, and include a first region and a second region arranged diagonally and a third region and a fourth region arranged diagonally; N (≧2) sets of parallel x-directional linear patterns respectively defined by N exposure steps and N sets of parallel y-directional linear pattern respectively defined by the N exposure steps; and a set of parallel x-directional photoresist bars and a set of parallel y-directional photoresist bars that are both formed in a lithography process, wherein the N sets of x-directional linear patterns and the set of x-directional photoresist bars are arranged in parallel, the N sets of y-directional linear patterns and the set of y-directional photoresist bars are arranged in parallel, each set of x-directional linear patterns includes a first part of x-directional linear patterns and a second part of x-directional linear patterns, each set of y-directional linear patterns includes a first part of y-directional linear patterns and a second part of y-directional linear patterns, the set of x-directional photoresist bars includes a first part of x-directional photoresist bars and a second part of x-directional photoresist bars, the set of y-directional photoresist bars includes a first part of y-directional photoresist bars and a second part of y-directional photoresist bars, the first parts of x-directional linear patterns of the N sets of x-directional linear patterns and the first part of x-directional photoresist bars are disposed in the first region, the second parts of x-directional linear patterns of the N sets of x-directional linear patterns and the second part of x-directional photoresist bars are disposed in the second region, the first parts of y-directional linear patterns of the N sets of y-directional linear patterns and the first part of y-directional photoresist bars are disposed in the third region, and the second parts of y-directional linear patterns of the N sets of y-directional linear patterns and the second part of y-directional photoresist bars are disposed in the fourth region.