Mark Position Determination Method

TL;DR: In this paper, a method of determining positions of marks on a substrate, the marks comprising structures arranged periodically in at least a first direction, at least some of the structures comprising periodic sub-structures, the substructures having a smaller period than the structures, the positional offsets being caused by a combination of both known and unknown components, was proposed.

Abstract: A method of determining positions of marks on a substrate, the marks comprising structures arranged periodically in at least a first direction, at least some of the structures comprising periodic sub-structures, the sub-structures having a smaller period than the structures, the marks being formed with positional offsets between the sub-structures and the structures, the positional offsets being caused by a combination of both known and unknown components, the method comprising illuminating a plurality of the marks with radiation beams having different characteristics and detecting radiation diffracted by the marks using one or more detectors which produce output signals processing the signals, wherein the processing comprises discriminating between constituent parts of the signals, the discriminating being based on a variation of the signals as a function of spatial positions of the marks on the substrate, selecting at least one of the constituent parts of the signals, and using the at least one selected constituent part of the signals, and information relating to differences between the known components, to calculate a corrected position of at least one mark.