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US 2009/0021723 A1Published application
Generating model signals for interferometry
AssigneeZygo Corporation
InventorXavier Colonna De Lega
Life of this patent
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Abstract
A method is disclosed which includes, for each of multiple areas of a test surface on a test object having different reflectivities, using an interferometry system to measure each area in a first mode of operation that measures information about the reflectivity of the area over a range of angles and wavelengths; using the same interferometry-system to measure the test surface in a second mode of operation that interferometrically profiles a topography of the test surface over a range including at least some of the multiple areas; and correcting the profile based on the information about the reflectivity of the multiple areas to reduce errors.
Claims54
An interferometry method, comprising:
- directing test light to a first calibration surface over a range of illumination angles and combining the test light emerging back from the first calibration surface with reference light to form an interference pattern, wherein the test light from the first calibration surface and the reference light are derived from a common source;
- directing at least a portion of the combined light from the first calibration surface to a multi-element detector so that different elements of the detector correspond to different illumination angles of the first calibration surface by test light;
- directing test light to a second calibration surface different from the first calibration surface over a range of illumination angles and combining the test light emerging back from the second calibration surface with reference light to form an interference pattern, wherein the test light from the second calibration surface and the reference light are derived from the common source;
- directing at least a portion of the combined light from the second calibration surface to the multi-element detector so that different elements of the detector correspond to different illumination angles of the second calibration surface by the test light;
- and
- determining information about an interferometry system based on interference signals measured by the different elements of the detector for the test light emerging from the first and second calibration surfaces and other information about the first and second calibration surfaces,
- wherein:
- the information about the interferometry system comprises information corresponding to at least one of a spectral distribution of the common source, a relative attenuation of a polarization state perpendicular to the plane of incidence compared to a polarization state parallel to the plane of incidence, a variation of the spectral distribution of the illumination across a pupil plane of the interferometry system, a variation of the mean intensity of the illumination across a pupil plane of the interferometry system, a variation of the phase of the illumination across a pupil plane of the interferometry system, and a variation of the spectral intensity of the illumination across a pupil plane of the interferometry system.
5 more elements
An interferometry method comprising:
- for each of multiple areas of a test surface on a test object having different reflectivities, using an interferometry system to measure each area in a first mode of operation that measures information about the reflectivity of the area over a range of angles and wavelengths;
- using the same interferometry system to measure the test surface in a second mode of operation that interferometrically profiles a topography of the test surface over a range including at least some of the multiple areas;
- and
- correcting the profile based on the information about the reflectivity of the multiple areas to reduce errors.
1 more element
The method of claim, 18, wherein the correcting comprises, for each area:
- determining a height offset based on the information about the reflectivity of the area;
- and
- adding the offset to the corresponding portion of the profile.
An interferometry system comprising:
- a light source;
- a multi-element detector;
- an interferometer configured to:
- direct test fight to a first calibration surface over a range of illumination angles and combine the test light emerging back from the first calibration surface with reference light to form an interference pattern, wherein the test light from the first calibration surface and the reference light are derived from a common light source;
- direct at least a portion of the combined light from the first calibration surface to the multi-element detector so that different elements of the detector correspond to different illumination angles of the first calibration surface by test light;
- direct test light to a second calibration surface different from the first calibration surface over a range of illumination angles and combine the test light emerging back from the second calibration surface with reference light to form an interference pattern, wherein the test light from the second calibration surface and the reference light are derived from the light source;
- and
- direct at least a portion of the combined light from the second calibration surface to the multi-element detector so that different elements of the detector correspond to different illumination angles of the second calibration surface by the test light;
- and
- an electronic processor configured to:
- determine information about the interferometry system based on interference signals measured by the different elements of the detector for the test light emerging from the first and second calibration, surfaces and other information about the first and second calibration surfaces,
- wherein:
- the information about the interferometry system comprises information corresponding to at least one of:
- a spectral distribution of the common source, a variation of the spectral distribution of the illumination across a pupil plane of the interferometry system, a variation of the mean intensity of the illumination across a pupil plane of the interferometry system, a variation of the phase of the illumination across a pupil plane of the interferometry system, and a variation of the spectral intensity of the illumination across a pupil plane of the interferometry system.
11 more elements
An apparatus comprising:
- an interferometer system configured to:
- operate in a first mode to, for each of multiple areas of a test surface on a test object having different reflectivities, measure information about the reflectivity of the area over a range of angles and wavelengths;
- operate in a second mode to interferometrically profile a topography of the test surface over a range including at least some of each of the multiple areas;
- and
- correct the profile based on information about the reflectivity of the multiple areas to reduce errors.
2 more elements
Dependencies are inferred from the claim text.