Abstract:
A method of calibrating a substrate positioning system of a lithographic apparatus, the method including: exposing a pattern with the lithographic apparatus on an exposed layer on the surface of a substrate having a reference layer, wherein the pattern corresponds to a movement of the substrate by the substrate positioning system; measuring overlay data between the exposed layer and the reference layer on a plurality of positions on the substrate; transforming the overlay data from a spatial domain to a frequency domain by a discrete cosine transformation; modifying the overlay data in the frequency domain by selecting a subset of the overlay data; transforming the modified overlay data from the frequency domain back to the spatial domain by an inverse discrete cosine transformation; calibrating the substrate positioning system by using the modified overlay data in the spatial domain.
Abstract:
A method of calibrating a substrate positioning system of a lithographic apparatus, the method including: exposing a pattern with the lithographic apparatus on an exposed layer on the surface of a substrate having a reference layer, wherein the pattern corresponds to a movement of the substrate by the substrate positioning system; measuring overlay data between the exposed layer and the reference layer on a plurality of positions on the substrate; transforming the overlay data from a spatial domain to a frequency domain by a discrete cosine transformation; modifying the overlay data in the frequency domain by selecting a subset of the overlay data; transforming the modified overlay data from the frequency domain back to the spatial domain by an inverse discrete cosine transformation; calibrating the substrate positioning system by using the modified overlay data in the spatial domain.
Abstract:
A lithographic method for measuring a position of a target grating with a mask sensor apparatus which comprises a plurality of detector modules each comprising a diffraction grating located at a mask side of a projection system of a lithographic apparatus and an associated detector, the method comprising a first step of measuring first intensities of a combination of diffraction orders diffracted from the target grating while the mask sensor apparatus is moved relatively to the target grating along a first direction; a second step of displacing the mask sensor apparatus relative to the target grating in a second direction, wherein a size of the relative displacement is proportional to a spatial frequency of a potential error; and a third step of measuring second intensities of the combination of diffraction orders diffracted from the target grating while the mask sensor apparatus is moved relatively to the target grating along the first direction.