Patent ID: 6937334

Claim:
A method of measuring alignment of a substrate, provided with at least one substrate alignment mark having a periodic structure, with respect to a reference alignment mark having a periodic structure with a period, prior to imaging a mask pattern in a resist layer on the substrate, the method comprising: illuminating a substrate alignment mark with an alignment beam and imaging this mark on a reference alignment mark, and determining the intensity of alignment radiation from the reference alignment mark by, using a substrate alignment mark having a periodic structure with a second period which is smaller than the first period of the reference alignment mark; providing the resist layer with an additional alignment mark having a periodic structure with a third period such that, upon illumination by the alignment beam of the substrate alignment mark and the additional alignment mark, an interference pattern is generated having a fourth period of which is approximately equal to the first period of the reference alignment mark, and imaging the interference pattern on the reference alignment mark, wherein the interference pattern is imaged on a mask alignment mark via an optical filter, which selects diffraction order of the radiation from the substrate alignment marks to proceed to said mask alignment mark.