Method of calibrating a lithographic apparatus, alignment method, computer program, data storage medium, lithographic apparatus, and device manufacturing method
First Claim
1. A method of calibrating a lithographic apparatus, the method comprising:
- calculating a displacement vector between (a) a position of a mark on a back side of a reference substrate as observed through a front-to-backside alignment optics of the lithographic apparatus and (b) an actual position of said mark;
moving the reference substrate a small distance relative to said front-to-backside alignment optics and comparing a resulting displacement of an image of a point on the back side of the reference substrate to a resulting displacement of a point on the front side of the reference substrate to generate a first correction vector;
repeating said moving and comparing for a different point on the reference substrate to generate a second correction vector; and
applying calibration information based on the displacement vector and the first and second correction vectors.
1 Assignment
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Accused Products
Abstract
In one method of compensating for the distortion of front-to-backside alignment optics, a displacement vector between the estimated position of a substrate mark and the actual position of a substrate mark is calculated. An optical correction array is also calculated by moving a reference substrate by a fixed amount and comparing how far an image of a point on the back side of a reference substrate moves to how far a corresponding point on the front side of the substrate moves. The displacement vector and optical correction array may then be used to accurately calculate the position of further substrates.
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Citations
26 Claims
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1. A method of calibrating a lithographic apparatus, the method comprising:
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calculating a displacement vector between (a) a position of a mark on a back side of a reference substrate as observed through a front-to-backside alignment optics of the lithographic apparatus and (b) an actual position of said mark;
moving the reference substrate a small distance relative to said front-to-backside alignment optics and comparing a resulting displacement of an image of a point on the back side of the reference substrate to a resulting displacement of a point on the front side of the reference substrate to generate a first correction vector;
repeating said moving and comparing for a different point on the reference substrate to generate a second correction vector; and
applying calibration information based on the displacement vector and the first and second correction vectors. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. The method of calibrating a lithographic apparatus, the method comprising:
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for each of a plurality of marks arranged to be observed through a single branch of said front-to-backside alignment optics of the lithographic apparatus, calculating a first displacement vector between (a) the mark and (b) an image of the mark observed in an image window of said front-to-backside alignment optics;
for each of the plurality of marks, calculating a second displacement vector between (a) the mark and (b) an image of the mark observed in an image window of said front-to-backside alignment optics subsequent to said calculating a first displacement vector; and
comparing the first and second displacement vectors to detect a change in the front-to-backside alignment optics. - View Dependent Claims (9, 10, 11, 12, 13)
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14. An alignment method comprising:
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providing an alignment beam of radiation; and
providing an alignment system for projecting the alignment beam onto a substrate mark on the back side of a substrate and detecting said substrate mark, wherein a position of the substrate mark is calculated using a displacement vector and a plurality of correction vectors. - View Dependent Claims (15, 16, 17)
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18. A data storage medium storing machine-executable instructions that describe a method comprising:
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calculating a displacement vector between (a) a position of a mark on a back side of a reference substrate as observed through a front-to-backside alignment optics of the lithographic apparatus and (b) an actual position of said mark;
moving the reference substrate a small distance relative to said front-to-backside alignment optics and comparing a resulting displacement of an image of a point on the back side of the reference substrate to a resulting displacement of a point on the front side of the reference substrate to generate a first correction vector;
repeating said moving and comparing for a different point on the reference substrate to generate a second correction vector; and
applying calibration information based on the displacement vector and the optical correction vectors.
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19. A lithographic apparatus comprising:
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a radiation system configured to provide a beam of radiation;
a support structure configured to support patterning structure, the patterning structure serving to pattern the beam of radiation according to a desired pattern;
a substrate table configured to hold a substrate;
a projection system arranged to project the patterned beam onto a target portion of the substrate;
an alignment system arranged to detect alignment between a reference mark and said substrate mark using an alignment beam of radiation and front-to-backside alignment optics;
a storage device arranged to store a displacement vector and a plurality of correction vectors; and
a correction device arranged to correct an alignment error of the substrate. - View Dependent Claims (20, 21)
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22. A lithographic projection apparatus comprising:
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a radiation system configured to provide a beam of radiation;
a support structure configured to support patterning structure, the patterning structure serving to pattern the beam of radiation according to a desired pattern;
a substrate table configured to hold a substrate;
a projection system arranged to project the patterned beam onto a target portion of the substrate;
front-to-backside alignment optics arranged to project an image of said substrate mark to the front side of said substrate; and
an alignment system arranged to detect alignment between a reference mark and said substrate mark using an alignment beam of radiation and said front-to-backside alignment optics, wherein said front-to-backside alignment optics is configured to simultaneously project images of a plurality of marks including said substrate mark. - View Dependent Claims (23, 24, 25)
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26. A lithographic projection apparatus comprising front-to-backside alignment optics, wherein an object window of the front-to-backside alignment optics has a diameter of at least one millimeter.
Specification