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US 7,889,355 B2Granted
Interferometry for lateral metrology
AssigneeZygo Corporation
InventorsXavier Colonna De Lega, Robert Stoner, Peter De Groot
Life of this patent
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Abstract
A method is disclosed which includes: using a scanning interferometry system, generating a sequence of phase-shifted interferometry images at different scan positions of an object comprising a buried surface, identifying a scan position corresponding to a position of best focus for the buried surface based on the sequence of phase-shifted interferometry images of the object, and generating a final image based on the phase-shifted interferometry images and the scan position, where the interferometric fringes in the final image are reduced relative to the interferometric fringes in the phase-shifted interferometry images.
Claims35
A method comprising:
- using a scanning interferometry system comprising a reference surface to generate a sequence of phase-shifted interferometry images at different scan positions of an object comprising a buried surface, each scan position corresponding to a different optical path length difference between light collected from the object and light collected from a reference surface;
- identifying a scan position corresponding to the position of best focus for the buried surface based on the sequence of phase-shifted interferometry images of the object;
- and
- generating a final image based on the phase-shifted interferometry images and the scan position corresponding to the position of best focus,
- wherein a contrast of intensity fringes in the final image is reduced relative to a contrast of intensity fringes in the phase-shifted interferometry images and the position of best focus for the buried surface is different from a position where the optical path length difference is zero.
2 more elements
A method comprising:
- generating, relative to a reference surface, a sequence of phase-shifted interferometry images of an object comprising a buried surface using an interference microscope, each phase-shifted interferometry image being generated for a different scan position corresponding to a different optical path length difference between light collected from the object and light collected from a reference surface;
- and
- generating a final image of the buried surface based on the phase-shifted interferometry images,
- wherein a contrast of intensity fringes in the final image is reduced relative to a contrast of intensity fringes in the phase-shifted interferometry images and a position of best focus of the buried surface with respect to the interference microscope is different from a position where the optical path length difference is zero.
1 more element
A non-transitory computer readable medium which causes a processor to:
- generate a final image, at a position of best focus of a buried surface in an object with respect to an interference microscope, based on a sequence of phase-shifted interferometry images of the object acquired using the interference microscope comprising a reference surface, each phase-shifted interferometry image being acquired for a different scan position corresponding to a different optical path length difference between light collected from the object and light collected from a reference surface,
- wherein a contrast of intensity fringes in the final image is reduced relative to a contrast of intensity fringes in the phase-shifted interferometry images and the position of best focus for the buried surface is different from a position where the optical path length difference is zero;
- and
- output information based on the image.
1 more element
An apparatus comprising:
- a scanning interferometer comprising a reference surface which, during operation generates a sequence of phase-shifted interferometry images at different scan positions of an object comprising a buried surface, each scan position corresponding to a different optical path length difference between light collected from the object and light collected from a reference surface;
- and
- an electronic controller coupled to the interferometer which, during operation:
- identifies a scan position corresponding to the position of best focus for the buried surface based on the sequence of phase-shifted interferometry images of the object;
- generates a final image based on the phase-shifted interferometry images and the scan position corresponding to the position of best focus, wherein a contrast of intensity fringes in the final image is reduced relative to a contrast of intensity fringes in the phase-shifted interferometry images and the position of best focus for the buried surface is different from a position where the optical path length difference is zero;
- and
- outputs information based on the image.
4 more elements
Dependencies are inferred from the claim text.