OPTICAL GAIN APPROACH FOR ENHANCEMENT OF OVERLAY AND ALIGNMENT SYSTEMS PERFORMANCE
First Claim
1. An optical alignment apparatus, comprising:
- a first beam splitter adapted to divide an image of a grating target on a substrate into first and second portions;
an image transformation element optically coupled to the first beam splitter; and
a second beam splitter adapted to combine the first portion from the first beam splitter and the second portion from the image transformation element,wherein the image transformation element is configured to optically modify the first and/or second portion of the image of the grating target such that a final image formed from the combination of the first and second portions is characterized by a Moiré
pattern.
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Abstract
A resultant image of a grating target may be obtained by dividing an image of the target into first and second portions and optically modifying the first and/or second portion such that a final image formed from their combination is characterized by a Moiré pattern. The resultant image may be analyzed to determine a shift in the grating target from a shift in the Moiré pattern. Optical alignment apparatus may include a first beam splitter, an image transformation element optically coupled to the first beam splitter, and a second beam splitter. The first beam splitter divides an image of a grating target into first and second portions. The second beam splitter combines the first portion and the second portion. The image transformation element optically modifies the first and/or second portion such that a final image formed from their combination is characterized by a Moiré pattern.
19 Citations
13 Claims
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1. An optical alignment apparatus, comprising:
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a first beam splitter adapted to divide an image of a grating target on a substrate into first and second portions; an image transformation element optically coupled to the first beam splitter; and a second beam splitter adapted to combine the first portion from the first beam splitter and the second portion from the image transformation element, wherein the image transformation element is configured to optically modify the first and/or second portion of the image of the grating target such that a final image formed from the combination of the first and second portions is characterized by a Moiré
pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. The apparatus of claim 9, further comprising an image analyzer coupled to the optical sensor, the image analyzer having a memory containing one or more final images and a processor, the processor being adapted to compare a Moiré
- pattern from an image signal obtained from the sensor with a Moiré
from an image stored in the memory or to compare two or more images stored in the memory to determine a shift in the position of the grating target between the images.
- pattern from an image signal obtained from the sensor with a Moiré
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10. A method for optically aligning a substrate with a grating target, comprising:
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a) obtaining a resultant image of the grating target by; i) dividing an image of the grating target into first and second portions; ii) optically modifying the first and/or second portion such that a final image formed from the combination of the first and second portions is characterized by a Moiré
pattern;iii) combining the first and second portions to form the final image; and b) analyzing the resultant image to determine a shift in the grating target from a shift in the Moiré
pattern. - View Dependent Claims (11, 12, 13)
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Specification