Measurement and compensation of errors in interferometers
First Claim
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1. A method for determining the location of an alignment mark on a stage, the method comprising:
- measuring a location, x1, of a stage along a first measurement axis using an interferometer;
measuring a location, x2, of the stage along a second measurement axis substantially parallel to the first measurement axis; and
determining a location of the alignment mark along a third axis substantially parallel to the first measurement axis based on x1, x2, and a correction term, ψ
3,wherein the interferometer comprises interferometer optics configured to direct a measurement beam to reflect from a mirror where the interferometer optics or the mirror are attached to the stage, and ψ
3 is calculated from predetermined information comprising information characterizing imperfections in the interferometer optics.
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Abstract
In general, in one aspect, the invention features a method for determining the location of an alignment mark on a stage including measuring a location, x1, of a stage along a first measurement axis using an interferometer, measuring a location, x2, of the stage along a second measurement axis substantially parallel to the first measurement axis, and determining a location of the alignment mark along a third axis substantially parallel to the first measurement axis based on x1, x2, and a correction term, ψ3, calculated from predetermined information including information characterizing imperfections in the interferometer.
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Citations
59 Claims
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1. A method for determining the location of an alignment mark on a stage, the method comprising:
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measuring a location, x1, of a stage along a first measurement axis using an interferometer; measuring a location, x2, of the stage along a second measurement axis substantially parallel to the first measurement axis; and determining a location of the alignment mark along a third axis substantially parallel to the first measurement axis based on x1, x2, and a correction term, ψ
3,wherein the interferometer comprises interferometer optics configured to direct a measurement beam to reflect from a mirror where the interferometer optics or the mirror are attached to the stage, and ψ
3 is calculated from predetermined information comprising information characterizing imperfections in the interferometer optics. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 53, 54, 55, 56)
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17. A method, comprising:
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determining a correction term related to imperfections in an interferometer optics of a first interferometer in an interferometry system from measurements of first and second degrees of freedom of a measurement object with the interferometry system, where the interferometer optics are configured to direct a beam to reflect from the measurment object; and correcting subsequent measurements of a third degree of freedom of the measurement object made using the interferometry system based on the correction term. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 57, 58, 59)
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30. A method comprising:
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scanning a mirror surface relative to a pair of substantially parallel measurement axes of an interferometry system for a plurality of scan paths of different relative positions of the mirror surface along the measurement axes, the interferometry system comprising an interferometer including interferometer optics configured to direct a beam to reflect from the mirror; monitoring locations X1 and X2 of the mirror surface relative to the interferometric measurement axes with the interferometry system during the scanning; determining a profile of the mirror surface for each of the scan paths based on the monitored locations; and determining a correction term related to imperfections in the interferometer optics based on variations between the mirror profiles. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method comprising:
correcting measurements of a degree of freedom of a mirror relative to a first axis made using a first interferometer based on information that accounts for imperfections in interferometer optics of the first interferometer for different spatial frequencies, wherein the interferometer optics are configured to direct a beam to reflect from the mirror and contributions to the correction from the different spatial frequencies are weighted differently. - View Dependent Claims (41, 42, 43)
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44. An apparatus comprising:
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an interferometer configured to monitor a location, x1, of a mirror surface along a first axis, the interferometer comprising interferometer optics configured to direct a beam to reflect from the mirror surface; and an electronic controller coupled to the interferometer and configured so that during operation the electronic controller determines a location of the mirror surface along a third axis based on x1, a location, x2, of the mirror surface along a second axis and a correction term, ψ
3, calculated from predetermined information comprising information characterizing imperfections in the interferometer optics. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52)
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Specification