Patent ID: 8248608

Claim:
A method of determining the location of a lithographic substrate relative to an imprint template, the method comprising: positioning the substrate adjacent to the imprint template such that an alignment grating on the substrate and an alignment grating on the imprint template form a composite diffraction grating; directing an alignment radiation beam comprising radiation at a first wavelength and radiation at a second wavelength, the second wavelength being longer than the first wavelength, at the composite diffraction grating; providing relative lateral movement between the imprint template and the substrate; detecting radiation diffracted from the composite grating during the relative lateral movement; using the detected radiation at the second wavelength to obtain information regarding a separation between the substrate alignment grating and the imprint template alignment grating; and using the detected radiation at the first wavelength to obtain information regarding the lateral position of the substrate alignment grating relative to the imprint template alignment grating.