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Patent US7009712 - Leaky guided wave modes used in interferometric confocal microscopy to ... - Google Patents
A method of using an interferometric confocal microscope to measure features of a trench or via in a substrate, wherein the interferometric confocal microscope produces a measurement beam, the method involving: focusing the measurement beam at a selected location at or near the bottom of the trench or...http://www.google.com/patents/US7009712?utm_source=gb-gplus-sharePatent US7009712 - Leaky guided wave modes used in interferometric confocal microscopy to measure properties of trenches
Publication number US7009712 B2
Application number US 10/765,254
Also published as EP1606575A2, EP1606575A4, US20050128487, WO2004068065A2, WO2004068065A3
Publication number 10765254, 765254, US 7009712 B2, US 7009712B2, US-B2-7009712, US7009712 B2, US7009712B2
Patent Citations (63), Non-Patent Citations (20), Referenced by (3), Classifications (19), Legal Events (5)
Leaky guided wave modes used in interferometric confocal microscopy to measure properties of trenches
US 7009712 B2
A method of using an interferometric confocal microscope to measure features of a trench or via in a substrate, wherein the interferometric confocal microscope produces a measurement beam, the method involving: focusing the measurement beam at a selected location at or near the bottom of the trench or via to excite one or more guided-wave modes within the trench or via; measuring properties of a return measurement beam that is produced when the measurement beam is focused at the selected location, wherein the return measurement beam includes a component corresponding to a radiated field from the one or more guided-wave modes that are excited within the trench; and determining the features of the trench or via from the measured properties of the return measurement beam.
Confocal and interferometric confocal microscopy has been used to measure lateral spatial properties of trenches and trench arrays (see S. S. C. Chim and G. S. Kino, “Optical pattern recognition measurements of trench arrays with submicrometer dimensions,” Applied Optics 33, pp 678–685, 1994). However, confocal and interferometric confocal microscopy has not thus far been used to obtain information about the depth and widths of trenches.
The techniques described herein provide a way to use interferometric confocal microscopy to obtain information about the depth and width of trenches. The techniques involve exciting leaky guided-wave modes of a trench that may be symmetric or antisymmetric in a directions parallel or orthogonal to the walls of the trench by either a symmetric or an antisymmetric near-field beam in directions parallel to or orthogonal to the walls of the trench or by either a symmetric or an antisymmetric far-field optical beam in directions parallel to or orthogonal to the walls of the trench and focused to a spot that forms a corresponding symmetric or an antisymmetric image. The properties of the fields radiated by the excited leaky guided-wave modes are then measured to obtain information about the depth and width of the trench and/or the detection of included defects. Properties of the fields radiated by the excited guided-wave modes are measured using an interferometric confocal microscope. For measurement of properties of excited antisymmetric guided-wave modes, the interferometric confocal microscope may compensate for the effects of the antisymmetric properties of the excited guided-wave modes on the radiated fields to eliminate/reduce effects of background beams. The beams generated by fields radiated by the excited guided-wave modes exhibit properties different from background beams and these differences are used to compensate for and/or also eliminate/reduce effects of the background beams.
FIGS. 1 a–1 c are diagrammatic representations of trenches and paths of optical beams.
As will be described in greater detail below, leaky guided-wave modes that have either antisymmetrical or symmetrical spatial properties are excited in trenches by either far-field or near-field beams and are used in interferometric confocal microscopy to probe properties of the trenches located for example on a wafer. The properties of trenches comprise a depth and a critical dimension of a trench and defects located within the trench. Effects of certain background signals are eliminated interferometrically and certain other background signals are compensated in determination of conjugated quadratures of radiated fields generated by the excited leaky guided-wave modes. Images formed of return measurement beams comprising the radiated fields generated by the excited guided-wave modes exhibit astigmatism that is beneficially used in interferometric far-field and near-field confocal imaging systems and that can be compensated in interferometric far-field confocal imaging system. The beneficial use and/or compensation of the astigmatism increases signal-to-noise ratios of measured conjugated quadratures of fields of the corresponding return measurement beams. The beneficial use and/or compensation of the astigmatism further leads to increases in throughput. The excitation of leaky guided wave modes in vias may also be used to determine properties of the vias.
Trench 150 comprises a slab wave guide of width w and an index of refraction equal to 1 if not filled or if filled with a transparent medium equal to nT that is less than the index of refraction nW of the boundary defining mediums, e.g., fused silica, silicon nitride, or silicon. Accordingly, there is π phase shift experienced by a beam reflected at a large angle of incidence at the boundary of the slab wave guide. A direct consequence of the π phase shift is that the complex amplitude of the electric field of the leaky guided-wave modes used in the described embodiment are equal to zero at the walls of the trench. Accordingly, the complex amplitude of the electric field of the leaky guided-wave mode may be written as E = j2E 0 ⅇ - jk z z - β z + j ω t cos ( k x x ) where ( 1 ) k x w 2 = ( 2 p + 1 ) π 2 , p = 0 , 1 , ± … , ( 2 )
j=√{square root over (−1)}, kx and kz are the x and z components of the real component of the wave number k, and β is the imaginary component of wave number k. The coordinate system is shown in FIG. 1 c. The spectrum of leaky guided-wave modes of interest is continuous because the index of refraction of the trench nT is less than the index of refraction nW of the boundary defining medium and because of small values of w and corresponding small values of θ defined in FIG. 1 c.
Components kx and kz of complex wave number k are
kx=kT sin θT (3)
k z =k T(sec2θT−β2)1/2 (4)
where sin θT=sin θ/nT, kT=nTk0, and k0 is the free space wave number for the beam. For the leaky guided-wave modes of interest, the imaginary component β due to transmission of the leaky guided waves at the boundaries of the slab wave guide is β = - ln [ R S ( θ ) ] 1 / 2 1 w tan θ ( 5 )
where Rs(θ) is the reflectivity of a beam at the boundary of the slab wave guide for s polarization of the beam with an angle of incidence equal to [(π/2)−θ]. For the excited leaky guided-wave modes of interest, β<<|k| and the magnitude of the imaginary component β affects the magnitude of kz only in second and higher order terms in β.
The optical beam incident on slab wave guide shown in FIG. 1 c that will couple with a higher efficiency to a leaky guided-wave mode is one that has either a symmetric or an antisymmetric distribution of the electric field at the surface of the slab wave guide. A measurement beam used in the described embodiment is selected that has either a symmetric or antisymmetric distribution of the electric field to preferentially to excite either symmetric or antisymmetric leaky guided-wave modes of trench 150 according to the magnitude of w relative to λ and to procedures used to eliminate effects of background beams. An approximate expression for the coupling efficiency ζ(θ) of a beam to leaky guided-wave modes of a trench where the beam is focused at the z position 152 of the bottom of the trench is ζ ( θ max ) = 1 2 ( w h ) ( 1 θ max ) ( 6 )
The depth resolution ΔZ of the interferometric confocal imaging system is given by the formula Δ Z = 1 2 ( 1 1 - cos θ max ) λ ( 8 )
where λ is the wavelength of the measurement and return measurement beams.
corresponding to a range of aspect ratios w h ≤ 0.36 ( 10 )
[see Equations (8) and (9)]. The materials comprising the substrate for which results are given in Table 1 are SiO2, SiN, and Si and the reflectivity Rs of the s polarization is listed in Table 1 for a series of materials as a function of |θ| for 0≦|θ|≲0.18.
An important property of the excited leaky guided-wave modes is that the normalized z component kz/k0 of the wave number k departs from a value of 1 by less than approximately 1%. As a result of this property, it is evident that the “effective” index of refraction of the trench for leaky guided-wave modes is to a relatively high accuracy equal to 1. This property is used in converting measured conjugated quadratures to a depth h.
|θ| kz/k0 βw βw βw
degrees β = 0 SiO2 SiN Si
0 1.0000 0.000 0.000 0.000
2 1.0006 0.002 0.001 0.001
4 1.0024 0.009 0.005 0.003
6 1.0055 0.021 0.012 0.006
8 1.0098 0.037 0.022 0.010
10  1.0154 0.057 0.034 0.016
A first embodiment is shown schematically in FIG. 2 a. The first embodiment comprises a first imaging system generally indicated as 310, pinhole beam-splitter 312, detector 370, and a second imaging system generally indicated as numeral 410. The second imaging system 410 comprises a low power microscope having a large working distance, e.g. Nikon ELWD and SLWD objectives and Olympus LWD, ULWD, and ELWD objectives. First imaging system 310 comprises an interferometric confocal microscopy system such as described in commonly owned U.S. Provisional Application No. 60/442,982 (ZI-45) entitled “Interferometric Confocal Microscopy Incorporating Pinhole Array Beam-Splitter” and U.S. patent application filed Jan. 27, 2004 also entitled “Interferometric Confocal Microscopy Incorporating Pinhole Array Beam-Splitter” both of which are by Henry A. Hill. The contents of both of the cited patent applications are herein incorporated in their entirety by reference.
The first imaging system 310 is shown schematically in FIG. 2 b. The imaging system 310 is a catadioptric system such as described in commonly owned U.S. Pat. No. 6,552,852 filed Dec. 20, 2001 (ZI-38) entitled “Catoptric and Catadioptric Imaging System;” U.S. Provisional Patent Application No. 10/366,651 filed Feb. 3, 2003 (ZI-43) entitled “Catoptric and Catadioptric Imaging System;” U.S. Provisional Patent Application No. 60/501,666 filed Sep. 10, 2003 [ZI-54] entitled “Catoptric and Catadioptric Imaging Systems With Adaptive Catoptric Surfaces;” and U.S. Provisional Patent Application No. 60/506,715 filed Sep. 26, 2003 [ZI-56] entitled “Catoptric and Catadioptric Imaging Systems Comprising Pellicle Beam-Splitters And Non-Adaptive And Adaptive Catoptric Surfaces” all four of which are by Henry A. Hill. The contents of the four cited applications are incorporated herein in their entirety by reference.
Convex lens 352 has a center of curvature the same as the center of curvature of convex lens 350. Convex lenses 350 and 352 are bonded together with pinhole beam-splitter 312 in between. Pinhole array beam-splitter 312 is shown in FIG. 2 c. 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 filed Jul. 27, 2001 (ZI-15) entitled “Multiple-Source Arrays for Confocal and Near-field Microscopy” by Henry A. Hill and Kyle Ferrio of which the contents are incorporated herein in their entirety by reference. The spacing between pinholes of pinhole array beam-splitter 312 is shown in FIG. 2 c as b with aperture size a.
The description of the imaging properties of catadioptric imaging system 310 is the same as the corresponding portion of the description given for the imaging properties of catadioptric imaging system 10 in cited U.S. Provisional Application No. 60/442,982 filed Jan. 28, 2003 (ZI-45) and U.S. patent a plication filed Jan. 27, 2004 entitled “Interferometric Confocal Microscopy Incorporating Pinhole Array Beam-Splitter”.
For excitation of antisymmetric leaky guided-wave modes in a trench, an antisymmetric distribution of electric fields at each of the spots of the image spots in the image plane close to substrate 360 is generated in the first embodiment by introducing a π phase shift between the measurement beam components of beam components 328A and 328B. The phase shift may be with respect to the plane orthogonal or parallel to the walls of a trench in substrate 360. The π phase shift is introduced with the addition of a thin layer 356 to a portion of the convex surface of convex lens 350 such that a half wave phase or π phase shift is generated between the measurement beam components of beams 326A and 326B (see FIG. 2 b). The π phase shift can also be introduced by the use of adaptive catoptric surfaces such as described in cited U.S. Provisional Patent Application No. 60/501,666 [ZI-54] and cited U.S. Provisional Patent Application filed Sep. 26, 2003 [ZI-56] entitled “Catoptric and Catadioptric Imaging Systems Comprising Pellicle Beam-Splitters And Non-Adaptive And Adaptive Catoptric Surfaces.”
The description of input beam 324 is the same as corresponding portions of the description given for input beam 24 of cited U.S. Provisional Application No. 60/442,982 [ZI-45] and cited U.S. patent application filed Jan. 27, 2004 (ZI-45) entitled “Interferometric Confocal Microscopy Incorporating Pinhole Array Beam-Splitter” with beam-conditioner 322 configured as a two-frequency generator and frequency-shifter. Input beam 324 comprises two components that have different frequencies and have the same state of plane polarization. The frequency of each component of input beam 324 is shifted between two different frequency values by beam-conditioner 322 according to control signal 374 generated by electronic processor and controller 380. Source 318 of input beam 320 to frequency-shifter 322, such as a laser, can be any of a variety of single frequency lasers.
The conjugated quadratures of fields of the return measurement beams are obtained using either single-, double-, bi- or quad-homodyne detection methods such as described in cited commonly owned No. 60/442,982 (ZI-45) and U.S. patent application filed Jan. 27, 2004 (ZI-45) entitled “Interferometric Confocal Microscopy Incorporating Pinhole Array Beam-Splitter.” The bi- and quad-homodyne detection methods are also described in commonly owned U.S. Provisional Application No. 60/442,858 filed Jan. 27, 2003 (ZI-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 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” both of which are by Henry A. Hill and of which the contents are herein incorporated in their entirety by reference. In the determination of the conjugated quadratures of fields, sets of four measurements of the electrical interference signals 372 are made. For each of the set of four measurements of the electrical interference signals 372, a known sequence of phase shifts is introduced between the reference beam component and the return measurement beam component of output beam components 330A and 330B.
Referring to the bi-homodyne detection method used in various embodiments, a set of four electrical interference signal values are obtained for each spot on and/or in substrate 60 being imaged. The set of four electrical interference signal values Sj, j=1,2,3,4, used for obtaining conjugated quadratures of fields for a single a spot on and/or in a substrate being imaged is represented for the bi-homodyne detection within a scale factor by the formula S j = P j { ξ j 2  A 1  2 + ζ j 2  B 1  2 + η j 2  C 1  2 + ζ j η j 2  B 1   C 1  cos φ B 1 C 1 ɛ j + ξ j ζ j 2  A 1   B 1  cos φ A 1 B 1 ɛ j + ɛ j ξ j η j 2  A 1   C 1  cos φ A 1 C 1 + ξ j 2  A 2  2 + ζ j 2  B 2  2 + η j 2  C 2  2 + ζ j η j 2  B 2   C 2  cos φ B 2 C 2 γ j + ξ j ζ j 2  A 2   B 2  cos φ A 2 B 2 γ j + γ j ξ j η j 2  A 2   C 2  cos φ A 2 C 2 } ( 11 )
where coefficients A1 and A2 represent the amplitudes of the reference beams corresponding to the first and second frequency components of the input beam; coefficients B1 and B2 represent the amplitudes of background beams corresponding to reference beams A1 and A2, respectively; coefficients C1 and C2 represent the amplitudes of the return measurement beams corresponding to reference beams A1 and A2, respectively; Pj represents the integrated intensity of the first frequency component of the input beam in pulse j of the pulse sequence; and the values for ∈j and γj are listed in Table 2. The change in the values of ∈j and γj from 1 to −1 or from −1 to 1 correspond to changes in relative phases of respective reference and measurement beams. The coefficients ξj, ζj, and ηj represent effects of variations in properties of a conjugate set of four pinholes such as size and shape if used in the generation of the spot on and/or in substrate 360 and the sensitivities of a conjugate set of four detector pixels corresponding to the spot on and/or in substrate 360 for the reference beam, the background beam, and the return measurement beam, respectively.
2 −1  −1  1
3 −1  1 −1
4 1 −1  −1
It is assumed in Equation (11) that the ratio of |A2|/|A1| is not dependent on j or on the value of Pj. In order to simplify the representation of Sj so as to project the important features without departing from either the scope or spirit of the present invention, it is also assumed in Equation (11) that the ratio of the amplitudes of the return measurement beams corresponding to A2 and A1 is not dependent on j or on the value of Pj. However, the ratio |C2|/|C1| will be different from the ratio |A2|/|A1| when the ratio of the amplitudes of the measurement beam components corresponding to A2 and A1 are different from the ratio |A2|/|A1|.
Noting that cos φA 2 C 2 =±sin φA 1 C 1 by the control of the relative phase shifts between corresponding reference and return measurement beam components in beam 32, Equation (11) may be rewritten as S j = P j { ξ j 2 (  A 1  2 +  A 2  2 ) + ζ j 2 (  B 1  2 +  B 2  2 ) + η j 2 (  C 1  2 +  C 2  2 ) + 2 ξ j ζ j (  A 1   B 1  cos φ A 1 B 1 ɛ j +  A 2   B 2  cos φ A 2 B 2 γ j ) + 2 ξ j η j [ ɛ j  A 1   C 1  cos φ A 1 C 1 + γ j (  A 2   A 1  ) (  C 2   C 1  )  A 1   C 1  sin φ A 1 C 1 ] + 2 ζ j η j ( ɛ j  B 1   C 1  cos φ B 1 C 1 ɛ j + γ j  B 2   C 2  cos φ B 2 C 2 γ j ) } ( 12 )
Information about conjugated quadratures |C1|cos φA 1 C 1 and |C1|sin φA 1 C 1 are obtained using the symmetric and antisymmetric properties and orthogonality property of the conjugated quadratures terms in Equation (12) as represented by the following digital filters applied to the signal values Sj: F 1 ( S ) = ∑ j = 1 4 ɛ j S j P j ′ ξ j ′2 ( 13 ) = (  A 1  2 +  A 2  2 ) ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ξ j 2 ξ j ′2 ) + (  B 1  2 +  B 2  2 ) ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ζ j 2 ξ j ′2 ) + (  C 1  2 +  C 2  2 ) ∑ j = 1 4 ɛ j ( P j P j ′ ) ( η j 2 ξ j ′2 ) + 2  A 1   C 1  cos φ A 1 C 1 ∑ j = 1 4 ( P j P j ′ ) ( ξ j η j ξ j ′2 ) + 2 (  A 2   A 1  ) (  C 2   C 1  )  A 1   C 1  sin φ A 1 C 1 ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ξ j η j ξ j ′2 ) + 2  A 1   B 1  ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 1 B 1 ɛ j + 2  A 2   B 2  ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 2 B 2 ɛ j + 2  B 1   C 1  ∑ j = 1 4 ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 1 C 1 ɛ j + 2  B 2   C 2  ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 2 C 2 ɛ j , F 2 ( S ) = ∑ j = 1 4 γ j S j P j ′ ξ j ′2 ( 14 ) = (  A 1  2 +  A 2  2 ) ∑ j = 1 4 γ j ( P j P j ′ ) ( ξ j 2 ξ j ′2 ) + (  B 1  2 +  B 2  2 ) ∑ j = 1 4 γ j ( P j P j ′ ) ( ζ j 2 ξ j ′2 ) + (  C 1  2 +  C 2  2 ) ∑ j = 1 4 γ j ( P j P j ′ ) ( η j 2 ξ j ′2 ) + 2  A 1   C 1  cos φ A 1 C 1 ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ξ j η j ξ j ′2 ) + 2 (  A 2   A 1  ) (  C 2   C 1  )  A 1   C 1  sin φ A 1 C 1 ∑ j = 1 4 ( P j P j ′ ) ( ξ j η j ξ j ′2 ) + 2  A 1   B 1  ∑ j = 1 4 γ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 1 B 1 ɛ j + 2  A 2   B 2  ∑ j = 1 4 γ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 2 B 2 γ j + 2  B 1   C 1  ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 1 C 1 ɛ j + 2  B 2   C 2  ∑ j = 1 4 ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 2 C 2 γ j
The parameter [ (  A 2   A 1  ) (  C 2   C 1  ) ] ( 15 )
in Equations (13) and (14) needs to be determined in order complete the determination of a conjugated quadratures. The parameter given in Equation (15) can be measured for example by introducing π/2 phase shifts into the relative phase of the reference beam and the measurement beam and repeating the measurement for the conjugated quadratures. The ratio of the amplitudes of the conjugated quadratures corresponding to (sin φA 1 C 1 /cos φA 1 C 1 ) from the first measurement divided by the ratio of the amplitudes of the conjugated quadratures corresponding to (sin φA 1 C 1 /cos φA 1 C 1 ) from the second measurement is equal to [ (  A 2   A 1  ) (  C 2   C 1  ) ] 2 . ( 16 )
Note that certain of the factors in Equations (13) and (14) have nominal values of 4 within a scale factors, e.g., ∑ j = 1 4 ( P j P j ′ ) ( ξ j η j ξ j ′2 ) ≃ 4 , ∑ j = 1 4 ( P j P j ′ ) ( ζ j η j ξ j ′2 ) ≃ 4. ( 17 )
The scale factors correspond to the average values for the ratios of ξ′j/ηj and ξ′j/ζj, respectively, assuming that the average value of Pj/P′j≅1. Certain other of the factors in Equations (13) and (14) have nominal values of zero, e.g., ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ξ j 2 ξ j ′2 ) ≃ 0 , ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ζ j 2 ξ j ′2 ) ≃ 0 , ∑ j = 1 4 ɛ j ( P j P j ′ ) ( η j 2 ξ j ′2 ) ≃ 0 , ∑ j = 1 4 γ j ( P j P j ′ ) ( ξ j 2 ξ j ′2 ) ≃ 0 , ∑ j = 1 4 γ j ( P j P j ′ ) ( ζ j 2 ξ j ′2 ) ≃ 0 , ∑ j = 1 4 γ j ( P j P j ′ ) ( η j 2 ξ j ′2 ) ≃ 0 , ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ξ j η j ξ j ′2 ) ≃ 0. ( 18 )
The remaining factors, ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 1 B 1 ɛ j , ∑ j = 1 4 ɛ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 2 B 2 γ j , ∑ j = 1 4 ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 1 C 1 ɛ j , ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 2 C 2 γ j , ∑ j = 1 4 γ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 1 B 1 ɛ j , ∑ j = 1 4 γ j ( P j P j ′ ) ( ξ j ζ j ξ j ′2 ) cos φ A 2 B 2 γ j , ∑ j = 1 4 ɛ j γ j ( P j P j ′ ) ( ξ j η j ξ j ′2 ) cos φ B 1 C 1 ɛ j , ∑ j = 1 4 ( P j P j ′ ) ( ζ j η j ξ j ′2 ) cos φ B 2 C 2 γ j , ( 19 )
will have nominal magnitudes ranging from approximately zero to approximately 4 times a cosine factor and either the average value of factor (Pj/P′J)(ξjζj/ξ′j 2) or (Pj/P′J)(ζjηj/ξ′j 2) depending on the properties respective phases. For the portion of the background with phases that do not track to a first approximation the phases of the respective measurement beams, the magnitudes of all of the terms listed in the Equation (19) will be approximately zero. For the portion of the background with phases that do track to a first approximation the phases of the respective measurement beams, the magnitudes of the terms listed in Equation (19) will be approximately 4 times a cosine factor and either the average value of factor (Pj/P′J)(ξ′jζj/ξj 2) and or factor (Pj/P′J)(ζjηj/ξ′j 2).
Other techniques may be incorporated to reduce and/or compensate for the effects of background beams without departing from either the scope or spirit of the present invention 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,” U.S. Pat. No. 5,915,048 entitled “Method and Apparatus for Discrimination In-Focus Images from Out-of-Focus Light Signals from Background and Foreground Light Sources,” and U.S. Pat. No. 6,480,285 B1 wherein each of three patents are by Henry A. Hill. The contents of each of the three cited patents are herein incorporated in their entirety by reference.
The sequence of phase shifts is generated in the first embodiment by shifting the frequencies of components of input beam 324 by beam-conditioner 322. There is a difference in optical path length between the reference beam components and the return beam components of output beam components 330A and 330B and as a consequence, a change in frequencies of components of input beam 324 will generate corresponding phase shifts between the reference beam components and the return beam components of output beam components 330A and 330B. For an optical path difference L between the reference beam components and the return beam components of output beam components 330A and 330B, there will be for a frequency shift Δf a corresponding phase shift φ where φ = 2 π L ( Δ f c ) ( 20 )
Referring to the quad-homodyne detection method used in described embodiments, a set of four electrical interference signal values are obtained for each spot on and/or in substrate 360 being imaged with two pulse sequences from source 318 and beam conditioner 322. The set of four electrical interference signal values Sj, j=1, 2, 3, 4 used for obtaining conjugated quadratures of fields for a single a spot on and/or in a substrate being imaged is represented for the quad-homodyne detection within a scale factor by the formulae S 1 = P 1 { ξ 1 2  A 1  2 + ζ 1 2  B 1  2 + η 1 2  C 1  2 + ζ 1 η 1 2  B 1   C 1  cos φ B 1 C 1 ɛ 1 + ξ 1 ζ 1 2  A 1   B 1  cos φ A 1 B 1 ɛ 1 + ɛ 1 ξ 1 η 1 2  A 1   C 1  cos φ A 1 C 1 + ξ 1 2  A 2  2 + ζ 1 2  B 2  2 + η 1 2  C 2  2 + ζ 1 η 1 2  B 2   C 2  cos φ B 2 C 2 γ 1 + ξ 1 ζ 1 2  A 2   B 2  cos φ A 2 B 2 γ 1 + γ 1 ξ 1 η 1 2  A 2   C 2  cos φ A 2 C 2 } , ( 21 ) S 2 = P 1 { ξ 2 2  A 3  2 + ζ 2 2  B 3  2 + η 2 2  C 3  2 + ζ 2 η 2 2  B 3   C 3  cos φ B 3 C 3 ɛ 2 + ξ 2 ζ 2 2  A 3   B 3  cos φ A 3 B 3 ɛ 2 + ɛ 2 ξ 2 η 2 2  A 3   C 3  cos φ A 3 C 3 + ξ 2 2  A 4  2 + ζ 2 2  B 4  2 + η 2 2  C 4  2 + ζ 2 η 2 2  B 4   C 4  cos φ B 4 C 4 γ 2 + ξ 2 ζ 2 2  A 4   B 4  cos φ A 4 B 4 γ 2 + γ 2 ξ 2 η 2 2  A 4   C 4  cos φ A 4 C 4 } , ( 22 ) S 3 = P 2 { ξ 1 2  A 1  2 + ζ 1 2  B 1  2 + η 1 2  C 1  2 + ζ 1 η 1 2  B 1   C 1  cos φ B 1 C 1 ɛ 3 + ξ 1 ζ 1 2  A 1   B 1  cos φ A 1 B 1 ɛ 3 + ɛ 3 ξ 1 η 1 2  A 1   C 1  cos φ A 1 C 1 + ξ 1 2  A 2  2 + ζ 1 2  B 2  2 + η 1 2  C 2  2 + ζ 1 η 1 2  B 2   C 2  cos φ B 2 C 2 γ 3 + ξ 1 ζ 1 2  A 2   B 2  cos φ A 2 B 2 γ 3 + γ 3 ξ 1 η 1 2  A 2   C 2  cos φ A 2 C 2 } , ( 23 ) S 4 = P 2 { ξ 2 2  A 3  2 + ζ 2 2  B 3  2 + η 2 2  C 3  2 + ζ 2 η 2 2  B 3   C 3  cos φ B 3 C 3 ɛ 4 + ξ 2 ζ 2 2  A 3   B 3  cos φ A 3 B 3 ɛ 4 + ɛ 4 ξ 2 η 2 2  A 3   C 3  cos φ A 3 C 3 + ξ 2 2  A 4  2 + ζ 2 2  B 4  2 + η 2 2  C 4  2 + ζ 2 η 2 2  B 4   C 4  cos φ B 4 C 4 γ 4 + ξ 2 ζ 2 2  A 4   B 4  cos φ A 4 B 4 γ 4 + γ 4 ξ 2 η 2 2  A 4   C 4  cos φ A 4 C 4 } , ( 24 )
where coefficients A1, A2, A3, and A4 represent the amplitudes of the reference beams corresponding to the first, second, third, and fourth frequency components, respectively, of input beam 24; coefficients B1, B2, B3, and B4 represent the amplitudes of background beams corresponding to reference beams A1, A2, A3, and A4, respectively; coefficients C1, C2, C3, and C4 represent the amplitudes of the return measurement beams corresponding to reference beams A1, A2, A3, and A4, respectively; P1 and P2 represent the integrated intensities of the first frequency component in the first and second pulse sequences, respectively, of the input beam 324; and the values for ∈j and γj are listed in Table 2. The description of the coefficients ξj, ζj, and ηj for the quad-homodyne detection method is the same as the corresponding portion of the description given for ξj, ζj, and ηj of the bi-homodyne detection method.
Noting that cos φA 2 C 2 =±sin φA 1 C 1 by the control of the relative phase shifts between corresponding reference and measurement beam components in beam 32, Equations (21), (22), (23), and (24) may be written, respectively, as S 1 = P 1 { ξ 1 2 (  A 1  2 +  A 2  2 ) + ζ 1 2 (  B 1  2 +  B 2  2 ) + η 1 2 (  C 1  2 +  C 2  2 ) + 2 ζ 1 η 1 [  B 1   C 1  cos φ B 1 C 1 ɛ 1 +  B 2   C 2  cos φ B 2 C 2 γ 1 ] + 2 ξ 1 η 1 [ ɛ 1  A 1   C 1  cos φ A 1 C 1 + γ 1 (  A 2   A 1  ) (  C 2   C 1  )  A 1   C 1  sin φ A 1 C 1 ] + 2 ξ 1 ζ 1 [  A 1   B 1  cos φ A 1 B 1 ɛ 1 +  A 2   B 2  cos φ A 2 B 2 γ 1 ] } , ( 25 ) S 2 = P 1 { ξ 2 2 (  A 3  2 +  A 4  2 ) + ζ 2 2 (  B 3  2 +  B 4  2 ) + η 2 2 (  C 3  2 +  C 4  2 ) + 2 ζ 2 η 2 [  B 3   C 3  cos φ B 3 C 3 ɛ 2 +  B 4   C 4  cos φ B 4 C 4 γ 2 ] + 2 ξ 2 η 2 (  A 3   A 1  ) (  C 3   C 1  ) [ ɛ 2  A 1   C 1  cos φ A 1 C 1 + γ 2 (  A 4   A 3  ) (  C 4   C 3  )  A 1   C 1  sin φ A 1 C 1 ] + 2 ξ 2 ζ 2 [  A 3   B 3  cos φ A 3 B 3 ɛ 2 +  A 4   B 4  cos φ A 4 B 4 γ 2 ] } , ( 26 ) S 3 = P 2 { ξ 1 2 (  A 1  2 +  A 2  2 ) + ζ 1 2 (  B 1  2 +  B 2  2 ) + η 1 2 (  C 1  2 +  C 2  2 ) + 2 ζ 1 η 1 [  B 1   C 1  cos φ B 1 C 1 ɛ 3 +  B 2   C 2  cos φ B 2 C 2 γ 3 ] + 2 ξ 1 η 1 [ ɛ 3  A 1   C 1  cos φ A 1 C 1 + γ 3 (  A 2   A 1  ) (  C 2   C 1  )  A 1   C 1  sin φ A 1 C 1 ] + 2 ξ 1 ζ 1 [  A 1   B 1  cos φ A 1 B 1 ɛ 3 +  A 2   B 2  cos φ A 2 B 2 γ 3 ] } , ( 27 ) S 4 = P 2 { ξ 2 2 (  A 3  2 +  A 4  2 ) + ζ 2 2 (  B 3  2 +  B 4  2 ) + η 2 2 (  C 3  2 +  C 4  2 ) + 2 ζ 2 η 2 [  B 3   C 3  cos φ B 3 C 3 ɛ 4 +  B 4   C 4  cos φ B 4 C 4 γ 4 ] + 2 ξ 2 η 2 (  A 3   A 1  ) (  C 3   C 1  ) [ ɛ 4  A 1   C 1  cos φ A 1 C 1 + γ 4 (  A 4   A 3  ) (  C 4   C 3  )  A 1   C 1  sin φ A 1 C 1 ] + 2 ξ 2 ζ 2 [  A 3   B 3  cos φ A 3 B 3 ɛ 4 +  A 4   B 4  cos φ A 4 B 4 γ 4 ] } , ( 28 )
Information about the conjugated quadratures |C1|cos φA 1 C 1 and |C1|sin φA 1 C 1 are obtained using the symmetric and antisymmetric properties and orthogonality property of the conjugated quadratures as represented by the following digital filters applied to the signal values Sj: F 3 ( S ) = ( 1 P 1 ′ ) ( S 1 ξ 1 ′2 - S 2 ξ 2 ′2 ) - ( 1 P 2 ′ ) ( S 3 ξ 1 ′2 - S 4 ξ 2 ′2 ) , ( 29 ) F 4 ( S ) = ( 1 P 1 ′ ) ( S 1 ξ 1 ′2 - S 2 ξ 2 ′2 ) + ( 1 P 2 ′ ) ( S 3 ξ 1 ′2 - S 4 ξ 2 ′2 ) . ( 30 )
The description of ξ′j and P′j for the quad-homodyne detection method is the same as the corresponding description given for ξ′j and P′j in the bi-homodyne detection method. Using Equations (25), (26), (27), (28), (29), and (30), the following expressions are obtained for the filtered quantities containing components of the conjugated quadratures |C1|cos φA 1 C 1 and |C1|sin φA 1 C 1 : F 3 ( S ) = ( P 1 P 1 ′ - P 2 P 2 ′ ) [ (  A 1  2 +  A 2  2 ) ( ξ 1 2 ξ 1 ′2 ) - (  A 3  2 +  A 4  2 ) ( ξ 2 2 ξ 2 ′2 ) ] + ( P 1 P 1 ′ - P 2 P 2 ′ ) [ (  B 1  2 +  B 2  2 ) ( ζ 1 2 ξ 1 ′2 ) - (  B 3  2 +  B 4  2 ) ( ζ 2 2 ξ 2 ′2 ) ] + ( P 1 P 1 ′ - P 2 P 2 ′ ) [ (  C 1  2 +  C 2  2 ) ( η 1 2 ξ 1 ′2 ) - (  C 3  2 +  C 4  2 ) ( η 2 2 ξ 2 ′2 ) ] + 2 ( P 1 P 1 ′ + P 2 P 2 ′ ) [ ( ξ 1 η 1 ξ 1 ′2 ) + ( ξ 2 η 2 ξ 2 ′2 ) (  A 3   A 1  ) (  C 3   C 1  ) ]  A 1   C 1  cos φ A 1 C 1 + 2 ( P 1 P 1 ′ - P 2 P 2 ′ ) (  A 2   A 1  ) (  C 2   C 1  ) [ ( ξ 1 η 1 ξ 1 ′2 ) + ( ξ 2 η 2 ξ 2 ′2 ) (  A 4   A 2  ) (  C 4   C 2  ) ]  A 1   C 1  sin φ A 1 C 1 + 2 ( P 1 P 1 ′ cos φ A 1 B 1 ɛ 1 - P 2 P 2 ′ cos φ A 1 B 1 ɛ 3 ) ξ 1 ζ 1 ξ 1 ′2  A 1   B 1  - 2 ( P 1 P 1 ′ cos φ A 3 B 3 ɛ 2 - P 2 P 2 ′ cos φ A 3 B 3 ɛ 4 ) ξ 2 ζ 2 ξ 2 ′2  A 3   B 3  + 2 ( P 1 P 1 ′ cos φ A 2 B 2 γ 1 - P 2 P 2 ′ cos φ A 2 B 2 γ 3 ) ξ 1 ζ 1 ξ 1 ′2  A 2   B 2  - 2 ( P 1 P 1 ′ cos φ A 4 B 4 γ 2 - P 2 P 2 ′ cos φ A 4 B 4 γ 4 ) ξ 2 ζ 2 ξ 2 ′2  A 4   B 4  + 2 ( P 1 P 1 ′ cos φ B 1 C 1 ɛ 1 - P 2 P 2 ′ cos φ B 1 C 1 ɛ 3 ) ξ 1 ζ 1 ξ 1 ′2  B 1   C 1  - 2 ( P 1 P 1 ′ cos φ B 3 C 3 ɛ 2 - P 2 P 2 ′ cos φ B 3 C 3 ɛ 4 ) ξ 2 ζ 2 ξ 2 ′2  B 3   C 3  + 2 ( P 1 P 1 ′ cos φ B 2 C 2 γ 1 - P 2 P 2 ′ cos φ B 2 C 2 γ 3 ) ξ 1 ζ 1 ξ 1 ′2  B 2   C 2  - 2 ( P 1 P 1 ′ cos φ B 4 C 4 γ 2 - P 2 P 2 ′ cos φ B 4 C 4 γ 4 ) ξ 2 ζ 2 ξ 2 ′2  B 4   C 4  , ( 31 ) F 4 ( S ) = ( P 1 P 1 ′ + P 2 P 2 ′ ) [ (  A 1  2 +  A 2  2 ) ( ξ 1 2 ξ 1 ′2 ) - (  A 3  2 +  A 4  2 ) ( ξ 2 2 ξ 2 ′2 ) ] + ( P 1 P 1 ′ + P 2 P 2 ′ ) [ (  B 1  2 +  B 2  2 ) ( ζ 1 2 ξ 1 ′2 ) - (  B 3  2 +  B 4  2 ) ( ζ 2 2 ξ 2 ′2 ) ] + ( P 1 P 1 ′ + P 2 P 2 ′ ) [ (  C 1  2 +  C 2  2 ) ( η 1 2 ξ 1 ′2 ) - (  C 3  2 +  C 4  2 ) ( η 2 2 ξ 2 ′2 ) ] + 2 ( P 1 P 1 ′ - P 2 P 2 ′ ) [ ( ξ 1 η 1 ξ 1 ′2 ) + ( ξ 2 η 2 ξ 2 ′2 ) (  A 3   A 1  ) (  C 3   C 1  ) ]  A 1   C 1  cos φ A 1 C 1 + 2 ( P 1 P 1 ′ + P 2 P 2 ′ ) (  A 2   A 1  ) (  C 2   C 1  ) [ ( ξ 1 η 1 ξ 1 ′2 ) + ( ξ 2 η 2 ξ 2 ′2 ) (  A 4   A 2  ) (  C 4   C 2  ) ]  A 1   C 1  sin φ A 1 C 1 + 2 ( P 1 P 1 ′ cos φ A 1 B 1 ɛ 1 + P 2 P 2 ′ cos φ A 1 B 1 ɛ 3 ) ξ 1 ζ 1 ξ 1 ′2  A 1   B 1  - 2 ( P 1 P 1 ′ cos φ A 3 B 3 ɛ 2 + P 2 P 2 ′ cos φ A 3 B 3 ɛ 4 ) ξ 2 ζ 2 ξ 2 ′2  A 3   B 3  + 2 ( P 1 P 1 ′ cos φ A 2 B 2 γ 1 + P 2 P 2 ′ cos φ A 2 B 2 γ 3 ) ξ 1 ζ 1 ξ 1 ′2  A 2   B 2  - 2 ( P 1 P 1 ′ cos φ A 4 B 4 γ 2 + P 2 P 2 ′ cos φ A 4 B 4 γ 4 ) ξ 2 ζ 2 ξ 2 ′2  A 4   B 4  + 2 ( P 1 P 1 ′ cos φ B 1 C 1 ɛ 1 + P 2 P 2 ′ cos φ B 1 C 1 ɛ 3 ) ξ 1 ζ 1 ξ 1 ′2  B 1   C 1  - 2 ( P 1 P 1 ′ cos φ B 3 C 3 ɛ 2 + P 2 P 2 ′ cos φ B 3 C 3 ɛ 4 ) ξ 2 ζ 2 ξ 2 ′2  B 3   C 3  + 2 ( P 1 P 1 ′ cos φ B 2 C 2 γ 1 + P 2 P 2 ′ cos φ B 2 C 2 γ 3 ) ξ 1 ζ 1 ξ 1 ′2  B 2   C 2  - 2 ( P 1 P 1 ′ cos φ B 4 C 4 γ 2 + P 2 P 2 ′ cos φ B 4 C 4 γ 4 ) ξ 2 ζ 2 ξ 2 ′2  B 4   C 4  . ( 32 )
The parameters [ (  A 2   A 1  ) (  C 2   C 1  ) ] , ( 33 ) [ (  A 4   A 2  ) (  C 4   C 2  ) ] , ( 34 ) [ (  A 3   A 1  ) (  C 3   C 1  ) ] ( 35 )
need to be determined in order to complete the determination of a conjugated quadratures for certain end use applications. The parameters given by Equations (33), (34), and (35) can for example be measured by procedures analogous to the procedure described for the bi-homodyne detection method with respect to measuring the quantity specified by Equation (15).
There are a number of different ways for producing a pulsed source [see Chapter 11 entitled “Lasers”, Handbook of Optics, 1, 1995 (McGraw-Hill, New York) by W. Silfvast]. There will be a restriction on the duration or “pulse width” of a beam pulse τp1 produced by source 318 as a result of the continuous scanning mode used in the second mode for the acquisition of the electrical interference signal values of the first embodiment. Pulse width τp1 will be a parameter that in part controls the limiting value for spatial resolution in the direction of a scan to a lower bound of
Pulse width τp1 will also determine the minimum frequency difference that can be used in the bi- and quad-homodyne detection methods. In order that there be no contributions to the electrical interference signals from interference between fields of different conjugated quadratures, the minimum frequency spacing Δfmin is expressed as Δ f min ⪢ 1 τ p 1 . ( 38 )
The frequencies of input beam 324 are controlled by signals 374 and 392 from signal processor and controller 380 to correspond to the frequencies from a set of four frequencies that will yield the desired phase shifts between the reference and return measurement beam components of output beam components 330A and 330B. In the first mode for the acquisition of the electrical interference signals 372, each set of four arrays of electrical interference signal values from the sets of arrays of four electrical interference signal values corresponding to the set of four phase shift values are generated by common pixels of detector 370 for single- and bi-homodyne detection methods. In the second mode for the acquisition of electrical interference signals 372, each corresponding set of four electrical interference signal values from the sets of arrays of four electrical interference signal values are generated by a conjugate set of four different pixels of detector 370. Thus in the second mode of acquisition, the differences in pixel efficiency and the differences in sizes of pinholes in pinhole array beam-splitter 312 need to be compensated in the signal processing by signal processor and controller 380 as described in the description of the bi- and quad-homodyne detection methods in cited U.S. Provisional Application No. 60/442,858 (ZI-47) and U.S. patent application 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 joint measurements of conjugated quadratures of fields are generated by electric processor and controller 380 as described in the description of the bi- and quad-homodyne detection methods of the cited U.S. Provisional Application No. 60/442,858 (ZI-47) and corresponding U.S. patent application.
The description of source 318 and beam-conditioner 322 is the same as corresponding portions of the description given for the source and beam conditioner described in cited U.S. Provisional Application No. 60/442,858 (ZI-47) and U.S. patent Application 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.”
Background beam components in return measurement beams may also be eliminated or reduced in the first embodiment when properties of excited antisymmetric guided-wave modes in trenches are measured. The antisymmetric guided-wave modes are preferentially excited when the half-wave phase shifter 356 is used in the first embodiment. The effects of the 90 phase shift between the third components of return measurement beams 142 and 242 are compensated by the half wave phase shifter 356 in the imaging system so that the corresponding images formed are symmetric. However, the effects of the π phase shift introduced by half-wave phase-shifter 356 is not compensated for background beam components generated by scattering of measurement and return measurement beams in catadioptric imaging system 310 with the result that the amplitude of the corresponding background beam components imaged at a respective pinhole in pinhole array beam-splitter 312 is substantially antisymmetric. The resulting electric interference term between the respective symmetric reference beam and substantially antisymmetric background beam is substantially zero. This technique for elimination or reduction of effects of background beams is also 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,” U.S. Pat. No. 6,480,285 entitled “Multiple Layer Confocal Interference Microscopy Using Wavenumber Domain Reflectometry And Background Amplitude Reduction And Compensation,” and U.S. Pat. No. 6,633,388 [ZI-20] entitled “Scanning Interferometric Near-Field Confocal Microscopy with Background Amplitude Reduction and Compensation” wherein each of the three U.S. Patents are by Henry A. Hill. The contents of each of the three cited U.S. patents are herein incorporated in their entirety by reference.
A trench may be filled with a dielectric or transparent medium with an index of refraction nT. The description of the guided wave modes will be the same as described herein when the trench is not filled when nT<nW except that there will be aberrations introduced. The properties of the aberrations will be the same as the properties of aberrations introduced when imaging inside of a substrate. The aberrations can be compensated in a variant of the first embodiment is accomplished by introducing a thin layer (the thin layer has an index of refraction different from lens 352) between lens 352 and pinhole array beam-splitter 312 such as described in commonly owned U.S. Provisional Patent Application No. 60/444,707 filed Feb. 4, 2003 [ZI-44] entitled “Compensation for Effects of Mismatch in Indices of Refraction at a Substrate-Medium Interface in Confocal and Interferometric Confocal Microscopy” by Henry A. Hill the contents of which are herein incorporated in their entirety by reference. The procedure will also work for the case of nT>nW. However, in this case the excited guided-wave modes will not be of the leaky class.
A second embodiment comprises the interferometer system of FIGS. 2 a–2 c with interferometer 310 comprising an interferometric far field confocal microscope such as described in cited U.S. Pat. No. 5,760,901. In the second embodiment, beam-conditioner 322 is configured as the two-frequency generator and phase-shifter.
A third embodiment comprises the interferometer system of FIGS. 2 a–2 c with interferometer 310 comprising an interferometric far field confocal microscope such as described in cited U.S. Pat. No. 5,760,901 wherein the phase masks are removed. In the third embodiment, beam-conditioner 322 is configured as a two-frequency generator and phase-shifter.
A fourth embodiment comprises the interferometer system of FIGS. 2 a–2 c with interferometer 310 comprising an interferometric far field confocal microscope such as described in cited U.S. Pat. No. 6,480,285. In the fourth embodiment, beam-conditioner 322 is configured as a two-frequency generator and phase-shifter.
A fifth embodiment comprises the interferometer system of FIGS. 2 a–2 c with interferometer 310 comprising an interferometric far field confocal microscope such as described in cited U.S. Pat. No. 6,480,285 wherein the phase masks are removed. In the fifth embodiment, beam-conditioner 322 is configured as a two-frequency generator and phase-shifter.
Leaky guided-wave modes in a trench are excited using near-field probe beams such as described in commonly owned U.S. Pat. No. 6,445,453 B1 [ZI-14] entitled “Scanning Interferometric Near-Field Confocal Microscopy” by Henry A. Hill the contents of which are herein incorporated by reference and in commonly owned U.S. Pat. No. 6,633,388 [ZI-20]. In the other embodiments, the subwavelength apertures comprise slits with subwavelength widths.
US5384639 * May 17, 1993 Jan 24, 1995 International Business Machines Corporation Depth measurement of high aspect ratio structures
1 U.S. Appl. No. 09/852,369, filed Jan. 3, 2002, Hill.
2 U.S. Appl. No. 09/917,402, filed Jul. 27, 2001, Hill.
3 U.S. Appl. No. 10/765,254, filed Jan. 27, 2004, Hill.
4 U.S. Appl. No. 10/765,368, filed Jan. 27, 2004, Hill.
5 U.S. Appl. No. 10/886,157, filed Jul. 7, 2004, Hill.
6 U.S. Appl. No. 60/442,858, filed Jul. 27, 2002, Hill.
7 U.S. Appl. No. 60/442,982, filed Jan. 29, 2003, Hill.
8 U.S. Appl. No. 60/443,980, filed Jan. 31, 2003, Hill.
9 U.S. Appl. No. 60/444,707, filed Jan. 4, 2003, Hill.
10 U.S. Appl. No. 60/445,739, filed Feb. 7, 2003, Hill.
11 U.S. Appl. No. 60/447,254, filed Feb. 13, 2003, Hill.
12 U.S. Appl. No. 60/448,250, filed Jan. 19, 2003, Hill.
13 U.S. Appl. No. 60/448,360, filed Feb. 19, 2003, Hill.
15 U.S. Appl. No. 60/459,493, filed Apr. 1, 2003, Hill.
16 U.S. Appl. No. 60/460,129, filed Apr. 3, 2003, Hill.
17 U.S. Appl. No. 60/485,255, filed Jul. 7, 2003, Hill.
18 U.S. Appl. No. 60/485,507, filed Jul. 7, 2003, Hill.
19 U.S. Appl. No. 60/501,666, filed Sep. 10, 2003, Hill.
20 U.S. Appl. No. 60/506,715, filed Sep. 26, 2003, Hill.
US8218152 Dec 3, 2008 Jul 10, 2012 The Board Of Trustees Of The University Of Illinois Group refractive index reconstruction with broadband interferometric confocal microscopy
US9812996 * Nov 17, 2014 Nov 7, 2017 Tokyo Electron Limited Method for calculating distance, method for neutralizing electrostatic chuck, and processing apparatus
US20150162233 * Nov 17, 2014 Jun 11, 2015 Tokyo Electron Limited Method for calculating distance, method for neutralizing electrostatic chuck, and processing apparatus
International Classification G02B27/10, G02B17/08, G01B9/04, A45D8/00, G02B21/00, G01B9/02
Cooperative Classification G02B27/108, G02B21/0056, G02B21/006, G01B9/04, G02B27/143, A45D2008/006
European Classification G01B9/04, G02B21/00M4A7C, G02B27/10S, G02B27/14F, G02B21/00M4A7F
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HILL, HENRY A.;REEL/FRAME:015036/0337