CPC G03F 7/70633 (2013.01) [G01N 21/4788 (2013.01); G03F 7/70683 (2013.01)] | 16 Claims |
1. A target for determining a performance parameter of a lithographic process, the target comprising:
a first sub-target formed by at least two overlapping gratings, wherein an underlying grating of the first sub-target has a first pitch Pb1 and a top lying grating of the first sub-target has a second pitch Pt1,
wherein a predetermined wavelength generates n scattered orders for the underlying grating of the first sub-target and m scattered orders for the top lying grating of the first sub-target such that the n scattered orders and the m scattered orders generate a Moire pitch according to
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at least a second sub-target formed by at least two overlapping gratings, wherein an underlying grating of the second sub-target has a third pitch Pb2 and a top lying grating of the second sub-target has a fourth pitch Pt2,
wherein a predetermined wavelength generates n scattered orders for the underlying grating of the second sub-target and m scattered orders for the top lying grating of the second sub-target such that the n scattered orders and the m scattered orders generate a Moire pitch according to
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wherein the first pitch Pb1 and the third pitch Pb2 comprise a same bottom pitch P0, which produces an overlay proportionality between a phase and an overlay that is linearly dependent on the bottom pitch P0 according to
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