Source: https://patents.google.com/patent/US7064838
Timestamp: 2018-05-27 19:47:04
Document Index: 121520555

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 10', 'Application No. 60', 'Application No. 10']

US7064838B2 - Apparatus and method for measurement of fields of backscattered and forward scattered/reflected beams by an object in interferometry - Google Patents
Apparatus and method for measurement of fields of backscattered and forward scattered/reflected beams by an object in interferometry Download PDF
US7064838B2
US7064838B2 US10816172 US81617204A US7064838B2 US 7064838 B2 US7064838 B2 US 7064838B2 US 10816172 US10816172 US 10816172 US 81617204 A US81617204 A US 81617204A US 7064838 B2 US7064838 B2 US 7064838B2
US20040227950A1 (en )
There are different ways to configure source 18 and beam-conditioner 22 to meet the input beam requirements of the different embodiments. Examples of beam-conditioners that may be used in the second technique comprise combinations of a two frequency generator and phase shifting type of beam-conditioner such as described in commonly owned U.S. Provisional Patent Application No. 60/442,858 (47) entitled “Apparatus and Method for Joint Measurements of Conjugated Quadratures of Fields of Reflected/Scattered Beams by an Object in Interferometry” and U.S. patent application Ser. No. 10/765,369, filed Jan. 27, 2004 (ZI-47) and entitled “Apparatus and Method for Joint Measurements of Conjugated Quadratures of Fields of Reflected/Scattered and Transmitted Beams by an Object in Interferometry”. Other examples of beam-conditioners that may be used in the second technique comprising combinations of multiple frequency generators and phase shifting types of beam-conditioners such as described for example in commonly owned U.S. Provisional Patent Application Serial No. 60/459,425 (ZI-50) entitled “Apparatus and Method for Joint Measurement of Fields of Scattered/Reflected Orthogonally Polarized Beams by an Object in Interferometry” and U.S. patent application Ser. No. 10/816,180 filed Apr. 1, 2004 also entitled “Apparatus and Method for Joint Measurement of Fields of Scattered/Reflected Orthogonally Polarized Beams by an Object in Interferometry”. The two U.S. Provisional Patent Applications and the two U.S. Patent Applications are all by Henry A. Hill and the contents of which are incorporated herein in their entirety by reference.
The conjugated quadratures of fields of return measurement beams are obtained by using a single-, double-, bi-, quad-homodyne detection method or variant thereof. The bi- and quad-homodyne detection methods are described for example in cited U.S. Provisional Patent Application No. 60/442,858 (47) and U.S. patent application Ser. No. 10/765,369, filed Jan. 27, 2004 (ZI-47) and entitled “Apparatus and Method for Joint Measurements of Conjugated Quadratures of Fields of Reflected/Scattered and Transmitted Beams by an Object in Interferometry”. The variants of the bi- and quad-homodyne detection methods are described for example in cited U.S. Provisional Patent Application No. 60/459,425 (ZI-50) and U.S. Patent Application10/816,180 filed Apr. 1, 2004 and entitled “Apparatus and Method for Joint Measurement of Fields of Scattered/Reflected Orthogonally Polarized Beams by an Object in Interferometry”.
The double-homodyne detection method which is applicable to non-ellipsometric measurements uses input beam 24 comprising four frequency components and four detectors to obtain measurements of electrical interference signals that are subsequently used to obtain conjugated quadratures in non-ellipsometric measurements. Each detector element of the four detector elements obtains a different one of the four electrical interference signal values with the four electrical interference signal values obtained simultaneously to compute the conjugated quadratures for a field. Each of the four electrical interference signal values contains only information relevant to one orthogonal component of the conjugated quadratures. The double-homodyne detection used herein is related to the detection methods such as described in Section IV of the article by G. M D'ariano and M G. A. Paris entitled “Lower Bounds On Phase Sensitivity In Ideal And Feasible Measurements,” Phys. Rev. A 49, 3022–3036 (1994). Accordingly, the double-homodyne detection method does not make joint determinations of conjugated quadratures of fields wherein each electrical interference signal value contains information simultaneously about each of two orthogonal components of the conjugated quadratures.
The first imaging system 10 is shown schematically in FIG. 1 c. The imaging system 10 is a catadioptric system such as described in commonly owned U.S. patent application Ser. No. 10/028,508 (ZI-38) and U.S. Pat. No. 6,717,736 (ZI-43) both of which are entitled “Catoptric and Catadioptric Imaging System.” Both of the two cited patent applications are by Henry A. Hill and the contents of the two cited patent applications are incorporated herein in their entirety by reference.
Convex lens 52 has a center of curvature the same as the center of curvature of convex lens 50. Convex lenses 50 and 52 are bonded together with pinhole beam-splitter 12 in between. Pinhole array beam-splitter 12 is shown in FIG. 1 d. The pattern of pinholes in pinhole array beam-splitter is chosen to match the requirements of an end use application. An example of a pattern is a two dimensional array of equally spaced pinholes in two orthogonal directions. The pinholes may comprise circular apertures, rectangular apertures, or combinations thereof such as described in commonly owned U.S. patent application Ser. No. 09/917,402 (ZI-15) entitled “Multiple-Source Arrays for Confocal and Near-field Microscopy” by Henry A. Hill and Kyle Ferrio of which the contents thereof are incorporated herein in their entirety by reference. The pinholes may also comprise microgratings such as described in cited U.S. Provisional Patent Application No. 60/459,425 (ZI-50) and U.S. Patent Application filed Apr. 1, 2004 (ZI-50) and entitled “Joint Measurement Of Fields Of Orthogonally Polarized Beams Scattered/Reflected By An Object In Interferometry”. A nonlimiting example of a pinhole array for pinhole array beam-splitter 12 is shown in FIG. 1 d having a spacing between pinholes of b with aperture size a.
φ = 2 ⁢ ⁢ π ⁢ ⁢ L ⁡ ( Δ ⁢ ⁢ f c ) ( 1 )
Δ ⁢ ⁢ f min >> 1 τ p1 . ( 4 )
With respect to the variants of the bi- and quad-homodyne detection methods wherein conjugated quadratures are obtained jointly, a set of eight electrical interference signal values is obtained for each spot on and/or in substrate 60 being imaged. The processing of the measured arrays of sets of measured electrical interference signal values for the determination of conjugated quadratures of fields of return measurement beams is described for example in cited U.S. Provisional Patent Application No. 60/459,425, filed Apr. 1, 2003 (ZI-50) and cited U.S. patent application Ser. No. 10/816,180 filed Apr. 1, 2004 and entitled “Apparatus and Method for Joint Measurement of Fields of Scattered/Reflected Orthogonally Polarized Beams by an Object in Interferometry”, both of which are incorporated herein by reference.
In other embodiments, the first, second, third, and fourth embodiments are configured to make ellipsometric non-joint and joint measurements of fields of scattered/reflected orthogonally polarized beams by the spots on or in substrate 60. The first, second, third, and fourth embodiments use variants of the single-, double-, bi-, and quad-homodyne detection methods such as described in cited U.S. Provisional Patent Application No. 60/459,425 (ZI-50] and U.S. Patent Application No. 10/816,180 filed Apr. 1, 2004 entitled “Apparatus and Method for Joint Measurement Of Fields Of Scattered/Reflected Orthogonally Polarized Beams By An Object In Interferometry”. In the other embodiments, pinhole array 12 may be replaced by an array of microgratings such as described in cited U.S. Provisional Patent Application No. 60/459,425 (ZI-50] and U.S. Patent Application No. 10/816,180 filed Apr. 1, 2004 entitled “Apparatus and Method for Joint Measurement Of Fields Of Scattered/Reflected Orthogonally Polarized Beams By An Object In Interferometry”.
A fifth embodiment comprises the interferometer system of FIG. 1 a with interferometer 10 comprising an interferometric far-field confocal microscope such as described in commonly owned U.S. Pat. No. 5,760,901 entitled “Method And Apparatus For Confocal Interference Microscopy With Background Amplitude Reduction and Compensation” by Henry A. Hill, the contents of which are herein incorporated in their entirety by reference. In the fifth embodiment, source 18 and beam-conditioner 22 are configured to operate in a phase shifting mode. The fifth embodiment has reduced effects of background because of background reduction features of cited U.S. Pat. No. 5,760,901.
A seventh embodiment comprises the interferometer system of FIG. 1 a with interferometer 10 comprising an interferometric far-field confocal microscope such as described in commonly owned U.S. Pat. No. 6,480,285 B1 entitled “Multiple Layer Confocal Interference Microscopy Using Wavenumber Domain Reflectometry and Background Amplitude Reduction and Compensation” by Henry A. Hill, the contents of which are herein incorporated in their entirety by reference. In the seventh embodiment, source 18 and beam-conditioner 22 are configured to operate in a phase shifting mode. The seventh embodiment has reduced effects of background because of background reduction features of cited U.S. Pat. No. 6,480,285 B1.
A ninth embodiment comprises the interferometer system of FIG. 1 a with interferometer 10 comprising an interferometric near-field confocal microscope such as described in commonly owned U.S. Pat. No. 6,445,453 (ZI-14) entitled “Scanning Interferometric Near-Field Confocal Microscopy” by Henry A. Hill, the contents of which are herein incorporated in their entirety by reference. In the ninth embodiment, source 18 and beam-conditioner 22 are configured to operate in a phase shifting mode. The eighth embodiment of cited U.S. Pat. No. 6,445,453 in particular is configured to operate in a mode with the measurement beam separated from the reference beam and incident on the substrate being imaged by a non-confocal imaging system, i.e., the measurement beam at the substrate is not an image of an array of pinholes but an extended spot. Accordingly, the corresponding embodiments of the ninth embodiment represent a non-confocal configuration for the measurement beam in both non-ellipsometric and ellipsometric measurements.
US20040227950A1 true US20040227950A1 (en) 2004-11-18
US7064838B2 true US7064838B2 (en) 2006-06-20
U.S. Appl. No. 60/442,858, filed Jan. 2003, Hill.