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US 2022/0065617 A1Published application
Determination of a change of object's shape
AssigneeNikon Corporation
InventorsEric Peter Goodwin, Goldie Goldstein
Life of this patent
Estimating the term…
Abstract
Surface changes are estimated using multiple speckle interferograms acquired using beams incident at different angles. Beam irradiation conditions can be changed to increase signal to noise ratio with averaging, such as weighted averaging. Irradiation conditions can be varied with a tilt plate, a wedge, or by changing beam wavelengths.
Claims39
A method for determining a change in a shape a surface, comprising:
- with the surface in a first state and with an initial first irradiation condition and an initial second irradiation condition:
- (a) collecting a first distribution and a second distribution of radiation in an input plane of a measurement unit, the first distribution and the second distribution of radiation received from the surface in response to irradiation of the surface with a first beam at an initial first irradiation condition and second beam at an initial second irradiation condition;
- (b) processing each of the first and second distributions of radiation associated with the surface in the first state to produce corresponding first and second wavefronts, introducing a shear between the first and second wavefronts, and directing overlapped first and second wavefronts to a radiation detector to produce a first image and a second image of the surface in the first state;
- (c) based on the first image and the second image of the surface in the first state, obtaining corresponding first and second phase maps associated with the surface in the first state;
- changing at least one geometrical parameter or at least one spectral parameter for each of the initial first and second irradiation conditions from initial values to produce modified first and second irradiation conditions;
- and
- repeating steps (a)-(c) to obtain first and second phase maps.
4 more elements
An optical system, comprising:
- an irradiation unit configured to produce first and second output radiation beams, wherein at least one spectral or geometric parameter associated with the first and second output radiation beams is changeable in response to an input applied to the irradiation unit;
- a measurement unit, including:
- a) a radiation detector;
- b) an aperture stop having an aperture stop axis;
- and
- c) an optical-wavefront-multiplier system configured to:
- receive an input radiation beam formed by propagation of the first and second radiation output beams to an object under test, through the aperture stop,
- form at least first and second radiation wavefronts by duplicating the input radiation beam, and
- direct the at least first and second radiation wavefronts onto the radiation detector to form first and second speckle interferograms of the object under test at first time and a second time, respectively;
- and
- a data-acquisition system operably coupled to the radiation detector and configured to determine a change of a shape of the object under test based on Fourier transforms of the first and second images.
8 more elements
A surface shape measuring apparatus, comprising:
- a first optical system situated to irradiate a target surface with an irradiation light beam and produce a speckle pattern associated with the target surface;
- a second optical system situated to receive a portion of the irradiation light beam from the target surface via an aperture, the irradiation light beam associated with a speckle pattern based on the target surface, the second optical system configured to divide the portion of the light beam from the target surface into a first light and a second light, produce a shear between the first light and the second light, and combine the sheared first light and second light;
- and
- a detector situated to receive the combined sheared first light and second light from the second optical system,
- wherein a dimension of the aperture in a first direction is smaller than a dimension of the aperture in a second direction that is perpendicular to the first direction.
2 more elements
The surface shape measuring apparatus of 32, wherein a shear direction associated with the first and second light is a direction perpendicular to the second direction.
A shape measurement system, comprising:
- an optical system coupled to produce speckle interferograms of a surface in a first state and a second state, the speckle interferograms associated with beams incident to the surface at at least two angles of incidence;
- and
- a processing system coupled to the optical system and configured to vary irradiation conditions of the beams and produce a surface map based on a plurality of speckle interferograms associated with the varied irradiation conditions.
Dependencies are inferred from the claim text.