Method and apparatus for compensating for process variations in an automatic positioning system

摘要

A target for use in automatic positioning systems that allows the automatic positioning system to align an edge in the pattern laid down with the target on a substrate with an edge in the pattern on a mask. The target compensates for variations in the size of the target and the target's associated pattern due to process variations in forming the target from an initial mask having the target and pattern. The target is symmetrical about a first axis and asymmetrical about a second axis where the first and second axes are orthogonal to each other. The target has two edges that will be detected by a sensing device in the automatic positioning system when the target is scanned along one axis and one edge that will be detected by the sensing device when the target is scanned along the other axis. The positioning system will detect the center of the target as being in the middle of the location of the two detected edges in one axis and the location of the detected edge in the other axis. The center of the target will move as a function of the location of the single edge thereby compensating for process variations in the formation of the target.