ASML Holding N.V.
Mark position determination method

Abstract:

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