Metrology method and apparatus, and device manufacturing method
First Claim
1. A method comprising:
- forming a structure on the substrate;
detecting, via at least two optical paths, an image of the structure through an optical system while the structure is illuminated with a beam of radiation;
determining at least one parameter of the structure based on intensity values derived from the detected image, wherein the image of the structure is smaller than an image field of the optical system;
detecting a position of the image within the image field; and
applying a correction to the detected image to reduce an influence on the at least one parameter caused by a difference between the at least two optical paths.
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Abstract
Methods are disclosed for measuring target structures formed by a lithographic process on a substrate. A grating or other structure within the target is smaller than an illumination spot and field of view of a measurement optical system. The position of an image of the component structure varies between measurements, and a first type of correction is applied to reduce the influence on the measured intensities, caused by differences in the optical path to and from different positions. A plurality of structures may be imaged simultaneously within the field of view of the optical system, and each corrected for its respective position. The measurements may comprise first and second images of the same target under different modes of illumination and/or imaging, for example in a dark field metrology application. A second type of correction may be applied to reduce the influence of asymmetry between the first and second modes of illumination or imaging, for example to permit a more accurate overly measurement in a semiconductor device manufacturing process.
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Citations
20 Claims
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1. A method comprising:
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forming a structure on the substrate; detecting, via at least two optical paths, an image of the structure through an optical system while the structure is illuminated with a beam of radiation; determining at least one parameter of the structure based on intensity values derived from the detected image, wherein the image of the structure is smaller than an image field of the optical system; detecting a position of the image within the image field; and applying a correction to the detected image to reduce an influence on the at least one parameter caused by a difference between the at least two optical paths. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An inspection apparatus comprising:
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a detection arrangement configured to form and detect, via at least two optical paths, an image of a structure on a substrate through an optical system while the structure is illuminated with a radiation beam; and a computational arrangement configured to; use intensity values derived from the detected image to determine at least one property of the structure, detect a position of the image within the image field when the image of the structure is smaller than an image field of the optical system, and in response to the detected position, apply a correction to the detected image to reduce an influence on the at least one property caused by a difference between the at least two optical paths. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification