Patent ID: 9188876
Filing Date: 2015-11-17
Classification: G03F

Abstract:
1. A method of reducing overlay error comprising: transferring a pattern of features from a reticle to a wafer; measuring a positional difference between the pattern on the reticle and the pattern on the wafer at a first set of data points; determining a second set of data points based on the first set of data points, the second set of data points being a subset of the first set of data points, wherein a position of the second set of data points is indicative of a position of at least one of the first set of data points, and a number of the first set of data points is greater than a number of the second set of data points; and changing a position of the reticle to minimize the positional difference based on the second set of data points, wherein the second set of data points comprises at least one region data point and at least one variable data point.