Metrology method and inspection apparatus, lithographic system and device manufacturing method
First Claim
1. An inspection apparatus comprising:
- an illumination arrangement operable to deliver conditioned beams of radiation to a substrate for use in measurements;
a detection arrangement operable during such measurements to detect respective images of the substrate using radiation diffracted from the substrate, the illumination arrangement and the detection arrangement forming a measurement optical system;
a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are configured to select which part of a diffraction spectrum of the diffracted radiation contributes to each image;
a controller configured to control the apparatus to produce first and second images of a periodic structure on the substrate, wherein;
the first image is detected in a first measurement using a first selected part of the diffracted radiation, the second image is detected in a second measurement using a second selected part of the diffracted radiation, which is symmetrically opposite to the first part in the diffraction spectrum of the periodic structure without rotating the substrate; and
wherein the detection arrangement further comprises a spatial light modulator operable to apply a varying optical attenuation over the selected part of the diffracted radiation prior to forming the first and second images respectively; and
a computational arrangement arranged to use a difference in intensity values derived from the first and second images to determine an asymmetry-related parameter.
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Abstract
Methods are disclosed for measuring target structures formed by a lithographic process on a substrate. A grating structure within the target is smaller than an illumination spot and field of view of a measurement optical system. The optical system has a first branch leading to a pupil plane imaging sensor and a second branch leading to a substrate plane imaging sensor. A spatial light modulator is arranged in an intermediate pupil plane of the second branch of the optical system. The SLM imparts a programmable pattern of attenuation that may be used to correct for asymmetries between the first and second modes of illumination or imaging. By use of specific target designs and machine-learning processes, the attenuation patterns may also be programmed to act as filter functions, enhancing sensitivity to specific parameters of interest, such as focus.
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Citations
12 Claims
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1. An inspection apparatus comprising:
- an illumination arrangement operable to deliver conditioned beams of radiation to a substrate for use in measurements;
a detection arrangement operable during such measurements to detect respective images of the substrate using radiation diffracted from the substrate, the illumination arrangement and the detection arrangement forming a measurement optical system;
a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are configured to select which part of a diffraction spectrum of the diffracted radiation contributes to each image;
a controller configured to control the apparatus to produce first and second images of a periodic structure on the substrate, wherein;
the first image is detected in a first measurement using a first selected part of the diffracted radiation, the second image is detected in a second measurement using a second selected part of the diffracted radiation, which is symmetrically opposite to the first part in the diffraction spectrum of the periodic structure without rotating the substrate; and
wherein the detection arrangement further comprises a spatial light modulator operable to apply a varying optical attenuation over the selected part of the diffracted radiation prior to forming the first and second images respectively; and
a computational arrangement arranged to use a difference in intensity values derived from the first and second images to determine an asymmetry-related parameter. - View Dependent Claims (2, 3, 5, 8, 9, 10, 11, 12)
- an illumination arrangement operable to deliver conditioned beams of radiation to a substrate for use in measurements;
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4. A lithographic system comprising:
- a lithographic apparatus comprising;
an illumination optical system arranged to illuminate a pattern;
a projection optical system arranged to project an image of the pattern onto a substrate; and
an inspection apparatus comprising, an illumination arrangement operable to deliver conditioned beams of radiation to the substrate for use in measurements;
a detection arrangement operable during such measurements to detect respective images of the substrate using radiation diffracted from the substrate the illumination arrangement and the detection arrangement forming a measurement optical system;
a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are operable to select which part of a diffraction spectrum of the diffracted radiation contributes to each image;
a controller configured to control the apparatus to produce first and second images of a periodic structure on the substrate, wherein;
the first image is detected in a first measurement using a first selected part of the diffracted radiation, the second image is detected in a second measurement using a second selected part of the diffracted radiation which is symmetrically opposite to the first part in the diffraction spectrum of the periodic structure without rotating the substrate; and
wherein the detection arrangement further comprises a spatial light modulator operable to apply a varying optical attenuation over the selected part of the diffracted radiation prior to forming the first and second images respectively and a computational arrangement arranged to use a difference in intensity values derived from the first and second images to determine an asymmetry-related parameter, wherein the lithographic apparatus is arranged to use the measurement results from the inspection apparatus in applying the pattern to further substrates. - View Dependent Claims (6, 7)
- a lithographic apparatus comprising;
Specification