Overlay mark, method of checking local aligmnent using the same and method of controlling overlay based on the same

摘要

An overlay mark is described, including N sets of parallel x-directional linear patterns respectively defined by N (≧2) exposure steps and N sets of parallel y-directional linear patterns 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 both formed in a lithography process. 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.