Lithographic apparatus, device manufacturing method, and device manufactured thereby
AssigneeASML Netherlands B.V.
InventorsArie Jeffrey Den Boef, Maarten Hoogerland, Boguslaw Gajdeczko
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Abstract
An alignment system uses a self-referencing interferometer that produces two overlapping and relatively rotated images of an alignment markers. Detectors detect intensities in a pupil plane where Fourier transforms of the images are caused to interfere. The positional information is derived from the phase difference between diffraction orders of the two images which manifests as intensity variations in the interfered orders. Asymmetry can also be measured by measuring intensities at two positions either side of a diffraction order.
Claims23
A lithographic projection apparatus, comprising:
- a radiation system for providing a projection beam of radiation;
- a support structure for supporting a patterning device used to pattern the projection beam according to a desired pattern;
- a substrate table for holding a substrate;
- a projection system for projecting the patterned beam onto a target portion of the substrate;
- and
- an alignment system having a self-referencing interferometer for projecting two overlapping images of an alignment mark that are relatively rotated by 180°, wherein the alignment system further comprises a light intensity detector system that detects light intensities at a plurality of different positions in a pupil plane of the self-referencing interferometer.
A device manufacturing method, comprising:
- providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
- projecting a patterned beam of radiation onto a target portion of the layer of radiation-sensitive material;
- and
- aligning an alignment mark on the substrate using a self-referencing interferometer that projects two overlapping images that are relatively rotated by 180° of the alignment mark, wherein the aligning comprises measuring the intensities of light at a plurality of different positions in a pupil plane where Fourier transforms of the images of the alignment mark interfere.
Dependencies are inferred from the claim text.