Methods for making holographic reticles for characterizing optical systems
First Claim
1. A method for characterizing an optical system using a holographic reticle, the method comprising:
- receiving two beams of coherent optical radiation;
adjusting a first beam to have a cylindrical wavefront;
adjusting a second beam to have a planewave wavefront;
interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern;
recording said interference pattern in a recording medium to create said holographic reticle;
configuring said optical system such that a first plane that includes said holographic reticle is positioned obliquely to a second plane where an image is recorded;
placing said holographic reticle in a path of an optical beam within said optical system; and
recording the image produced by the path of the optical beam passing through said holographic reticle;
wherein the image is configured to characterize said optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence.
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Accused Products
Abstract
Characterization of an optical system is quickly and easily obtained in a single acquisition step by obtaining image data within a volume of image space. A reticle and image plane are positioned obliquely with respect to each other such that a reticle having a plurality of feature sets thereon, including periodic patterns or gratings, is imaged in a volume of space, including the depth of focus. Metrology tools are used to analyze the detected or recorded image in the volume of space through the depth of focus in a single step or exposure to determine the imaging characteristics of an optical system. Focus, field curvature, astigmatism, spherical, coma, and/or focal plane deviations can be determined. The present invention is particularly applicable to semiconductor manufacturing and photolithographic techniques used therein, and is able to quickly characterize an optical system in a single exposure with dramatically increased data quality and continuous coverage of the full parameter space. In embodiments, the test reticle is holographically generated by interfering two or more beams of optical radiation. The resulting interference pattern is recorded on a reticle and used for testing the optical system. The geometry of the holographic interference pattern is tightly controlled by the properties of the interfering beams and is therefore more accurate than conventional reticle writing techniques.
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Citations
29 Claims
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1. A method for characterizing an optical system using a holographic reticle, the method comprising:
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receiving two beams of coherent optical radiation; adjusting a first beam to have a cylindrical wavefront; adjusting a second beam to have a planewave wavefront; interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern; recording said interference pattern in a recording medium to create said holographic reticle; configuring said optical system such that a first plane that includes said holographic reticle is positioned obliquely to a second plane where an image is recorded; placing said holographic reticle in a path of an optical beam within said optical system; and recording the image produced by the path of the optical beam passing through said holographic reticle; wherein the image is configured to characterize said optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 29)
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10. A method for characterizing an optical system using a holographic reticle, the method comprising:
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receiving two beams of coherent optical radiation; adjusting a first beam to have a spherical wavefront; adjusting a second beam to have a planewave wavefront; interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern; recording said interference pattern in a recording medium to create said holographic reticle; configuring said optical system such that a first plane that includes said holographic reticle is positioned obliquely to a second plane where an image is recorded; placing said holographic reticle in a path of an optical beam within said optical system; and recording the image produced by the path of the optical beam passing through said holographic reticle; wherein the image is configured to characterize said optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence. - View Dependent Claims (11)
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12. A method for characterizing an optical system using a holographic reticle, the method comprising:
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receiving two beams of coherent optical radiation; interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern; exposing photo-resist that is deposited on a reticle with said interference pattern; developing said photo-resist so that said reticle reflects said interference pattern thereby forming said holographic reticle; configuring said optical system such that a first plane that includes said holographic reticle is positioned obliquely to a second plane where an image is recorded; placing said holographic reticle in a path of an optical beam within said optical system; and recording the image produced by the path of the optical beam passing through said holographic reticle; wherein the image is configured to characterize said optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence.
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13. A method for making a holographic reticle that characterizes an optical system, the method comprising:
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receiving two beams of coherent optical radiation; interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern; generating a grating; generating precision phase shifts between adjacent grating patches to monitor image shifting aberrations; and recording said interference pattern in a recording medium to create said holographic reticle; wherein said holographic reticle is adapted to yield information on optical parameters of the optical system and thereby characterize the optical system. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for characterizing an optical system using a holographic reticle, the method comprising the steps of:
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receiving two beams of coherent optical radiation; expanding two of said beams, resulting in two diverging spherical wavefronts; interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern; recording said interference pattern in a recording medium to create said holographic reticle; configuring said optical system such that a first plane that includes said holographic reticle is positioned obliquely to a second plane where an image is recorded; placing said holographic reticle in a path of an optical beam within said optical system; and recording the image produced by the path of the optical beam passing through said holographic reticle; wherein the image is configured to characterize said optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence. - View Dependent Claims (24, 25, 26, 27)
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28. A method for characterizing an optical system using a holographic reticle, the method comprising:
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receiving two beams of coherent optical radiation; adjusting a first beam and a second beam to create plane wave beams; interfering said two beams, resulting in an interference volume of optical radiation having an interference pattern; recording said interference pattern in a recording medium to create said holographic reticle; configuring said optical system such that a first plane that includes said holographic reticle is positioned obliquely to a second plane where an image is recorded; placing said holographic reticle in a path of an optical beam within said optical system; and recording the image produced by the path of the optical beam passing through said holographic reticle; wherein the image is configured to characterize said optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence.
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Specification