Method for characterizing optical systems using holographic reticles
First Claim
1. A method of using a holographic reticle to characterize an optical system, the method comprising the steps of:
- (1) configuring the optical system such that a first plane containing the holographic reticle is positioned obliquely to a second plane where an image is recorded;
(2) placing the holographic reticle in a path of an optical beam within the optical system; and
(3) recording the image produced by the path of the optical beam passing through the holographic reticle;
wherein the image is configured to characterize the optical system for at least one of field curvature, astigmatism, coma, distortion, telecentricity, spherical aberrations, and variation of coherence.
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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
18 Claims
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1. A method of using a holographic reticle to characterize an optical system, the method comprising the steps of:
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(1) configuring the optical system such that a first plane containing the holographic reticle is positioned obliquely to a second plane where an image is recorded;
(2) placing the holographic reticle in a path of an optical beam within the optical system; and
(3) recording the image produced by the path of the optical beam passing through the holographic reticle;
wherein the image is configured to characterize the 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, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification