Micron Technology, Inc.
WAFER OVERLAY MARKS, OVERLAY MEASUREMENT SYSTEMS, AND RELATED METHODS

Abstract:

A method for determining overlay measurements includes orienting a wafer to align portions of lines of a pattern of an overlay mark with a direction in which a source emits light at the wafer and align other portions of the lines of the pattern to extend in a direction perpendicular to the direction in which the illumination source emits light at the wafer. The method includes capturing at least one image of the wafer via an imager sensor. The method also includes determining contrasts of regions of the overlay mark and determining a location of the overlay mark. Overlay marks include a pattern defining an array of columns. Each column includes a set of continuous lines oriented parallel to each other and extending in a first direction within a first region of a column and extending in a second different direction in a second region of the column.