Source: http://www.google.com/patents/US7639371?dq=inventor:%22Arthur+R.+Hair%22&ei=VAy0Tsa4NYTl0QGQiqWiBA
Timestamp: 2016-08-24 05:04:23
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Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 02805890', 'Application No. 200480033229', 'Application No. 02805890', 'Application No. 04784089', 'Application No. 10', 'Application No. 10', 'Application No. 10', 'Application No. 10', 'Application No. 02']

Patent US7639371 - Line profile asymmetry measurement - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThis disclosure provides methods for measuring asymmetry of features, such as lines of a diffraction grating. On implementation provides a method of measuring asymmetries in microelectronic devices by directing light at an array of microelectronic features of a microelectronic device. The light illuminates...http://www.google.com/patents/US7639371?utm_source=gb-gplus-sharePatent US7639371 - Line profile asymmetry measurementAdvanced Patent SearchPublication numberUS7639371 B2Publication typeGrantApplication numberUS 12/418,535Publication dateDec 29, 2009Priority dateMar 2, 2001Fee statusPaidAlso published asUS7515279, US20070201043, US20090190138Publication number12418535, 418535, US 7639371 B2, US 7639371B2, US-B2-7639371, US7639371 B2, US7639371B2InventorsChristopher RaymondOriginal AssigneeNanometrics IncorporatedExport CitationBiBTeX, EndNote, RefManPatent Citations (64), Non-Patent Citations (28), Referenced by (2), Classifications (17), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetLine profile asymmetry measurement
US 7639371 B2Abstract
This disclosure provides methods for measuring asymmetry of features, such as lines of a diffraction grating. On implementation provides a method of measuring asymmetries in microelectronic devices by directing light at an array of microelectronic features of a microelectronic device. The light illuminates a portion of the array that encompasses the entire length and width of a plurality of the microelectronic features. Light scattered back from the array is detected. One or more characteristics of the back-scattered light may be examined by examining data from the complementary angles of reflection. This can be particularly useful for arrays of small periodic structures for which standard modeling techniques would be impractically complex or take inordinate time.
This application is a continuation of U.S. patent application Ser. No. 10/571,418, filed Dec. 28, 2006, now U.S. Pat. No. 7,515,279 which is a U.S. National Phase application of PCT/US2004/030115, filed Sep. 13, 2004, which claims the benefit of U.S. Provisional Application No. 60/502,444, filed Sep. 12, 2003. Further, U.S. Patent Application Ser. No. 10/571,418 is a continuation-in-part of U.S. patent application Ser. No. 10/086,339, filed Feb. 28, 2002 now U.S. Pat. No. 6,856,408, which claims the benefit of U.S. Provisional Application No. 60/273,039, filed Mar. 2, 2001. The entirety of each of these applications is incorporated herein by reference.
Prior work in scatterometry used the technique for the measurement of line profiles in resist and etched materials. C. J. Raymond, et al., “Resist and etched line profile characterization using scatterometry, “Integrated Circuit Metrology, Inspection and Process Control XI, Proc. SPIE 3050 (1997). Embodiments of the present invention provide techniques for the measurement of asymmetric line profiles (e.g., unequal sidewall angles).
Diffraction can actually give rise to a number of different “orders,” or light beams, scattered from the features. In modern semiconductor production geometries, the period of the features is small and therefore typically only one diffraction order exists. This order is known as the “specular” or “zeroth” order and is the light beam most frequently used in scatterometry technology. One of the more common ways of analyzing light scatter using the specular order is to vary the incidence angle of the illuminating light source (which is usually a laser). As FIG. 1 illustrates, as the incident angle Θi is varied and a detector moves in tandem at angle Θn to measure the diffracted power of the specular order, a scatter “signature” is measured. It is this scatter signature—known as an angular signature—that contains information about the diffracting structure, such as the thickness of the grating and the width of a grating line. This angular signature, when measured properly, can also contain information about any asymmetry present in the grating lines as well. By measuring through complementary angles (both positive and negative with respect to normal), a signature can be obtained that is asymmetric if the line is asymmetric. Conversely, if the line profile is in fact symmetric, the measured signature will also be symmetric. Complementary angles are not needed, however, if a suitable theoretical diffraction model is available for comparison purposes, and the “inverse” problem (see below) can be performed.
The scatterometry method is often described in two parts, typically known as the “forward” and “inverse” problems, In the simplest sense the forward problem is the measurement of a scatter signature, and the inverse problem is the analysis of the signature in order to provide meaningful data. Many types of scatterometers have been investigated over the years, e.g., C. J. Raymond, et al., “Metrology of subwavelength photoresist gratings using optical scatterometry,” Journal of Vacuum Science and Technology B 13(4), pp. 1484-1495 (1995); S. Coulombe, et al., “Ellipsometric scatterometry for sub 0.1 μm measurements,” Integrated Circuit Metrology, Inspection and Process Control XII, Proc. SPIE 3332 (1999); Z. R. Hatab, et al., “Sixteen-megabit dynamic random access memory trench depth characterization using two-dimensional diffraction analysis,” Journal of Vacuum Science and Technology B 13(2), pp. 174-182 (1995); and X. Ni, et al., “Specular spectroscopic scatterometry in DUV lithography,” Proc SPIE 3677, pp. 159-168 (1999). The most widely studied, though, have been the angular or “2-Θ.” (because of the two theta variables shown in FIG. 1) variety where, as mentioned earlier, the incident angle is varied in order to obtain a scatter signature. It is this type of scatterometer that is preferred, but not necessary, for the measurement of line profile asymmetry. It should be noted that the scanning optical system in FIG. 1 allows this angular scatterometer to measure both positive and negative angles from normal incidence (0 degrees) Up to approximately �47 degrees.
In previous research scatterometry has been used for the measurement of critical dimensions (CDs) and profile characterization of photoresist samples, C. J. Raymond, et al. (1995), supra; and C. Baum, et al., “Resist line width and profile measurement using scatterometry,” SEMATECH AEC-APC Conference, Vail, Colo., (September 1999), as well as etched materials such as poly-silicon and metals, S. Bushman, et al., “Scatterometry Measurements for Process Monitoring of Polysilicon Gate Etch,” Process, Equipment, and Materials Control in Integrated Circuit Manufacturing III, Proc. SPIE 3213 (1997); C. Baum, et al., “Scatterometry for post-etch polysilicon gate metrology,” Integrated Circuit Metrology, Inspection and Process Control XIII, Proc. SPIE 3677, pp. 148-158 (1999); and C. Raymond, et al., “Scatterometry for the measurement of metal features,” Integrated Circuit Metrology Inspection and Process Control XIV Proc. SPIE 3998, pp. 135-146 (2000). Because the technology is rapid, non-destructive and has demonstrated excellent precision, it is an attractive alternative to other metrologies used in mainstream semiconductor manufacturing. In particular, scatterometry is quite amenable to measurements of asymmetry because, as will be demonstrated, angular scatter “signatures” can quickly show (without performing the inverse problem) if any asymmetry is present on the grating lines.
To introduce this concept of asymmetric grating lines giving rise to asymmetric measured scatter signatures, consider the simple photoresist line profiles shown in FIGS. 4( a)-(c). FIG. 4( a) depicts a perfectly symmetric profile with both wall angles equal to 90 degrees. In FIG. 4( b), the right wall angle has been changed to 80 degrees, while in FIG. 4( c) the opposite case is illustrated (left at 80 degrees, right back to 90 degrees). FIG. 5 shows the angular scatter signatures—measured through complementary angles—associated with each of these profiles. As can be seen in the figure, the symmetric profile yields a symmetric scatter signature for both polarizations. However, the asymmetric profiles show a significant amount of asymmetry in both polarizations. In fact, the signatures appear to be skewed, or “tipped,” as a result of the profile asymmetry. Furthermore, a comparison of the signature data for the 80/90 and 90/80 degree cases shows an interesting result—the reversal of the sidewall angles yields a reversal of the signature. Physically this reversal would be the same as rotating the wafer through 180 degrees and thereby transposing the positive and negative regions of the scan, so this result is self-consistent. These figures also illustrate the advantage of angular scatterometry for determining the presence of asymmetry since one could establish that the profiles were non-symmetric with mere visual investigation of the signatures.
The utility of the invention in determining asymmetry in three-dimensional structures by comparison of complementary angles, such as over a range, is graphically depicted in FIGS. 28 and 29. FIG. 28 is a graph of angular scatterometry signatures (mirrored over complementary ranges) of a first series of rectangular three-dimensional rectilinear structure deposited on top of a second series of rectangular structures structure as in FIG. 26. In FIG. 28, the solid line depicts no offset with respect to the overlaid single features, the dashed line depicts a 25 nm offset of these single features, and the dotted line depicts a 50 nm offset. The S-polarized measurements and the P-polarized measurements are symmetric about the 0� angle where there is no offset (the solid line). With 25 nm offset (the dashed line) each profile (such as the S Data profile or the P Data profile) is “skewed” about 0� such that each of the S Data and P Data plots are asymmetric. As the asymmetry of the three-dimensional structure increases, the asymmetry in the resulting plots correspondingly increases, such that the asymmetry is greater at a 50 nm offset (the dotted line) than it is at a 25 nm offset (the solid line). FIG. 29 is a graph of angular scatterometry signatures (mirrored over complementary ranges) of an oval “post-on-post” three-dimensional structure similar to FIG. 25, wherein a first series of oval-shaped posts is deposited on top of a second series of like-shaped posts. The solid line in FIG. 29 depicts no offset with respect to the first and second series, the dashed line depicts a 25 nm offset, and the dotted line depicts a 50 nm offset. As in FIG. 28, the degree of asymmetry within the S Data and in the P Data correlates to the degree of asymmetry in the three-dimensional structure.
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TechnoL B 12(6):3600-3606.28Supplementary European Search Report mailed on Feb. 15, 2007 for EP Application No. 02 70 9756.7, three pages.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS8069020 *Sep 19, 2007Nov 29, 2011Tokyo Electron LimitedGenerating simulated diffraction signal using a dispersion function relating process parameter to dispersionUS20090076782 *Sep 19, 2007Mar 19, 2009Tokyo Electron LimitedGenerating simulated diffraction signal using a dispersion function relating process parameter to dispersion* Cited by examinerClassifications U.S. Classification356/601, 356/636International ClassificationG01B11/02Cooperative ClassificationG01B11/306, G01B11/24, G01N21/95607, G03F7/70633, G03F7/705, G01B11/00, G03F7/70625European ClassificationG03F7/70L10B, G01B11/00, G01N21/956A, G03F7/70L10D, G03F7/70L2B, G01B11/24, G01B11/30CLegal EventsDateCodeEventDescriptionMar 11, 2013FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services