WO2005083352A1 - Procede et appareil de cartographie d'epaisseur a grande vitesse pour couches minces configurees - Google Patents

Procede et appareil de cartographie d'epaisseur a grande vitesse pour couches minces configurees Download PDF

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Publication number
WO2005083352A1
WO2005083352A1 PCT/US2004/032692 US2004032692W WO2005083352A1 WO 2005083352 A1 WO2005083352 A1 WO 2005083352A1 US 2004032692 W US2004032692 W US 2004032692W WO 2005083352 A1 WO2005083352 A1 WO 2005083352A1
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WIPO (PCT)
Prior art keywords
wafer
light
reflectance
film
image
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PCT/US2004/032692
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English (en)
Inventor
Scott A. Chalmers
Randall S. Geels
Thomas F. A. Bibby
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Filmetrics, Inc.
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Publication of WO2005083352A1 publication Critical patent/WO2005083352A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/211—Ellipsometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
    • G01B11/0625—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of absorption or reflection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
    • G01B11/0641—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of polarization
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0208—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/2823—Imaging spectrometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/30—Measuring the intensity of spectral lines directly on the spectrum itself
    • G01J3/36—Investigating two or more bands of a spectrum by separate detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
    • G01N21/274—Calibration, base line adjustment, drift correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4788—Diffraction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/9501—Semiconductor wafers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/956—Inspecting patterns on the surface of objects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/2803—Investigating the spectrum using photoelectric array detector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/211—Ellipsometry
    • G01N2021/213—Spectrometric ellipsometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N2021/4792—Polarisation of scatter light

Definitions

  • This invention relates generally to the field of film thickness measurement, and more specifically, to the field of film measurement in an environment, such as semiconductor wafer fabrication and processing, on which a layer with an unknown thickness resides on a patterned sample. Many industrial processes require precise control of film thickness.
  • a semiconductor wafer is fabricated in which one or more layers of material from the group comprising metals, metal oxides, insulators, silicon dioxide (SiOj), silicon nitride (SiN), polysilicon or the like, are stacked on top of one another over a substrate, made of a material such as silicon. Often, these layers are added through a process known as chemical vapor deposition (CVD), or removed by etching or removed by polishing through a process known as chemical mechanical polishing (CMP).
  • CVD chemical vapor deposition
  • CMP chemical mechanical polishing
  • the level of precision required can range from 0.0001 ⁇ m (less than an atom thick) to 0.1 ⁇ m (hundreds of atoms thick).
  • each product wafer i.e., on each wafer produced that contains partially processed or fully processed and saleable product
  • each product wafer i.e., on each wafer produced that contains partially processed or fully processed and saleable product
  • features on the order of 0.1 ⁇ m to 10 ⁇ m wide Because the areas covered by these features are generally unsuitable for measurement of film properties, specific measurement sites called "pads" are provided at various locations on the wafer. To minimize the area on the wafer that is taken up by these measurement pads, they are made to be very small, usually about 100 ⁇ m by 100 ⁇ m square.
  • a measurement spot size of an optical system refers to the size of a portion of an object being measured that is imaged onto a single pixel of an imaging detector positioned in an image plane ofthe optical system.
  • Systems exploiting this technique include a light source, a first polarizer to establish the polarization of light, a sample to be tested, a second polarizer (often referred to as an analyzer) that analyzes the polarization of light reflected from the sample, and a detector to record the analyzed light.
  • Companies such as J. A. Woolam, Inc. (Lincoln, NE) and Rudolph Technologies, Inc. (Flanders, NJ) manufacture ellipsometer systems. Accordingly, it is an object of the present invention to provide a method and apparatus for achieving rapid measurement of film thickness and other properties on patterned wafers during, between, or after semiconductor processing steps.
  • An additional object is a method and apparatus for film measurement that is capable of providing an accurate measurement of film thickness and other properties of individual films in a multi-layered or patterned sample.
  • An additional object is a method and apparatus for film measurement that is capable of providing an accurate measurement of film thickness and other properties of individual films in a multi-layered or patterned sample based on image analysis.
  • a further object is an optical method and apparatus for thin-film measurement that overcomes the disadvantages of the prior art. Further objects ofthe subject invention include utilization or achievement of the foregoing objects, alone or in combination. Additional objects and advantages will be set forth in the description which follows, or will be apparent to those of ordinary skill in the art who practice the invention.
  • the invention provides a spectrometer configured to simultaneously capture a reflectance spectrum for each of a plurality of spatial locations on the surface of a sample.
  • the spectrometer includes a wavelength-dispersive element, such as a prism or diffraction grating, for receiving light representative of the plurality of spatial locations, and separating the light for each such location into its constituent wavelength components.
  • the spectrometer further includes an imager for receiving the constituent wavelength components for each ofthe locations, and determining therefrom the reflectance spectrum for each location.
  • the invention also provides a system for measuring one or more properties of a layer of a sample.
  • the system includes a light source for directing light to the surface of the layer at an angle that deviates from the layer normal by a small amount.
  • a sensor for receiving light reflected from and representative of a plurality of spatial locations on the surface of the layer, and simultaneously determining therefrom reflectance spectra for each ofthe plurality of spatial locations on the surface.
  • the system also includes a processor for receiving at least a portion of the data representative of the reflectance spectra for each of the plurality of spatial locations and determining therefrom one or more properties ofthe layer.
  • the invention further includes one or more polarizers to provide for measuring the reflectance spectrum of polarized light.
  • broad spectral light passes through a first polarizer, reflects and mixes with light reflecting from one or more layers at a plurality of locations on the surface of a sample, and passes through a second polarizing element that allows the spectrometer to disperse and image the reflected light according to its polarization for each location.
  • the invention also provides a method for measuring one or more properties of a layer of a sample. The method includes the step of directing light to a surface of the layer. It also includes the step of receiving light at a small angle reflected from the surface of the layer, and determining therefrom reflectance spectra representative of each of a plurality of spatial locations on the surface of the layer.
  • the sample may be relatively translated with respect to the directed and received light until reflectance spectra for all or a substantial portion of the layer have been determined.
  • One or more properties of the layer may be determined from at least a portion ofthe reflectance spectra for all or a substantial portion ofthe layer.
  • the invention further provides a system of and method for measuring at least one film on a sample from light reflected from the sample having a plurality of wavelength components, each having an intensity.
  • a set of successive, spatially contiguous, one-spatial-dimension spectral reflectance images may be obtained by scanning the wafer with a one-spatial-dimension spectroscopic imager.
  • the resulting series of one-spatial-dimension spectral images may be arranged to form a two-spatial-dimension spectral image of the wafer.
  • the spectral data at one or more of the desired measurement locations may then be analyzed to determine a parameter such as film thickness.
  • the invention further provides a system of and method for measuring at least one film on a sample from polarized light reflected from the sample having a plurality of wavelength components, each having an intensity.
  • a set of successive, spatially contiguous, one-spatial-dimension spectral reflectance with s-polarized and/or p-polarized images may be obtained by scanning the wafer with a one-spatial-dimension spectroscopic imager.
  • the resulting series of one-spatial- dimension spectral images may be arranged to form an s-polarized two-spatial- dimension spectral image (s-polarized image) of the wafer and a p-polarized two- spatial-dimension spectral image (p-polarized image) of the wafer, where the s- polarized image and the p-polarized image map in a one-to-one way each of the plurality of spatial locations on the sample.
  • the s-polarized image and the p- polarized image data at one or more of the desired measurement locations may then be analyzed to determine a parameter such as film thickness.
  • FIG. 1 illustrates a first embodiment of a system in accordance with the subject invention.
  • FIG. 2 illustrates in detail the optical subsystem of the embodiment shown in FIG. 1.
  • FIG. 3 illustrates a second embodiment of a system in accordance with the subject invention.
  • FIG. 4 illustrates an embodiment of a method in accordance with the subject invention.
  • FIG. 5A is a top view of an example semiconductor wafer showing desired measurement locations.
  • FIG. 5B is a side view of an example semiconductor wafer showing stacked layers each configured with one or more precise features.
  • FIG. 5A is a top view of an example semiconductor wafer showing desired measurement locations.
  • FIG. 5B is a side view of an example semiconductor wafer showing stacked layers each configured with one or more precise features.
  • FIG. 6A illustrates a commercial embodiment of a system according to the invention.
  • FIG. 6B illustrates aspects ofthe optical path ofthe system of FIG. 6A.
  • FIG. 7 illustrates an example of a reflectance spectrum for a location on the surface of a semiconductor wafer.
  • FIG. 8 illustrates a cross section of the fiber bundle ofthe system of FIG.
  • FIG. 9A depicts the one-spectral, two-spatial dimensional data that is captured for an individual layer in the system of FIG. 6A.
  • FIG. 9B shows the ensemble of one-spectral, two-spatial dimensional data that together forms a hyperspectral image.
  • FIG. 10A illustrates the area surrounding a desired measurement location in which matching is performed in the system of FIG. 6A.
  • FIG. 10B illustrates the corresponding image of the desired measurement location in FIG. 10A.
  • FIG. 11 is a flowchart of an embodiment of a method of operation in the system of FIG. 6A.
  • FIG. 12 illustrates an embodiment of a spectral ellipsometric system in accordance with the subject invention.
  • FIG. 13 illustrates an embodiment of a variable angle spectral ellipsometric system in accordance with the subject invention.
  • FIG. 14A illustrates the illumination of patterned features with broad angle, large numerical aperture light according to the system in accordance with the prior art.
  • FIG. 14B illustrates the illumination of patterned features with shallow angle, small numerical aperture light according to the system in accordance with the subject invention.
  • FIG. 15 shows measurements of erosion using the system in accordance with the subject invention.
  • FIG. 16 is a flowchart showing a method of compensating icy second order spectral overlap using the apparatus ofthe subject invention.
  • FIG. 17 shows the spectral response with and without compensation for second order spectral overlap.
  • FIG. 18 shows the correction factor for compensation for second order spectral overlap.
  • FIG. 19 shows an image of a round wafer undergoing non-uniform motion during the measurement.
  • FIG. 20 shows an example of the Goodness-of-Alignment values as a function of rotational angle ⁇ using the auto-rotate algorithm of the present invention.
  • FIG. 21 illustrates a second embodiment of a spectral ellipsometric system in accordance with the subject invention.
  • FIG. 22 shows measurement spot size for 100% fill factor imaging for (A) optimal wafer orientation, and (B) worst-case wafer orientation.
  • FIG. 23 shows how to mask individual pixels according to the present invention.
  • FIG. 24 shows measurement spot size for ⁇ 100% fill factor imaging resulting from the use of masked pixels for (A) optimal wafer orientation, and (B) worst-case wafer orientation.
  • FIG. 25 illustrates the use of over-sampling to enhance vertical pixel image density using masked pixels according to the present invention.
  • FIG. 26 shows the technique of row staggering based on the use of masked pixels to enhance the horizontal pixel image density according to the present invention.
  • FIG. 27 illustrates another method of enhancing the horizontal pixel image density.
  • FIG.28 shows a wafer paddle motion dampening system.
  • FIG. 29 shows the integration of a process chamber viewport into the optical system ofthe line imaging spectrometer according to the present invention.
  • FIG. 30 shows a dual-Offher imaging system for enhancing the quality of images recorded with the line imaging spectrometer ofthe present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • a 1 st embodiment System for measurements at an angle
  • FIG. 1 A first embodiment of an imaging system 100 in accordance with the subject invention, suitable for use in applications such as measuring the thickness of transparent or semi-transparent films, is illustrated in FIG. 1.
  • the film to be measured ranges in thickness from .001 ⁇ m to 50 ⁇ m, but it should be appreciated that this range is provided by way of example only, and not by way of limitation.
  • This embodiment is advantageously configured for use with a wafer transfer station 1 to facilitate rapid measurement of a cassette of wafers.
  • the station houses a plurality of individual wafers la, lb, lc, and is configured to place a selected one of these wafers, identified with numeral Id in the figure, onto a platform 2.
  • Each of wafers la, lb, lc, Id has a center point and an edge.
  • This embodiment also comprises a light source 3 coupled to an optical fiber 9 or fiber bundle for delivering light from the light source 3 to the wafer Id situated on platform 2.
  • the light source 3 is a white light source.
  • the light source 3 is a tungsten-halogen lamp or the like in which the output is regulated so that it is substantially invariant over time.
  • this embodiment is shown being used to measure the thickness of film on wafer Id, which together comprises a sample, but it should be appreciated that this embodiment can advantageously be employed to measure the thickness of individual films in samples comprising multi-layer stacks of films, whether patterned or not.
  • Light source 3 may optionally include a diffuser disposed between light source 3 and optical fiber 9 to even out light source non- uniformities so that light entering optical fiber 9 is uniform in intensity.
  • the first embodiment of imaging system 100 further includes a line imaging spectrometer 11 comprising a lens assembly 4, a slit 5 having a slit width, a lens assembly 6, a diffraction grating 7, and a two-dimensional imager 8.
  • Line imaging spectrometer 11 has an optical axis 31, and is disposed in imaging system 100 so that optical axis 31 is aligned at a small angle to the wafer Id normal.
  • Lens assembly 4 and lens assembly 6 each have a magnification.
  • Two-dimensional imager 8 has an integration time during which it absorbs light incident upon it to create a detected signal.
  • Angle ⁇ defines near normal incidence, and can be as small as 0 degrees or as large as that given by the Brewster angle of the topmost layer, but preferably the angle ⁇ is approximately 2 degrees.
  • a range of angles from 0 to Brewster angle allows one or more measurements at angle , which provides greater information.
  • the angle ⁇ lies in a measurement plane that, if aligned with an array of conductive metal lines, results in improved measurements. Measurements obtained at such an angle are uniquely capable of determining the thickness of films in finely patterned areas with feature dimensions on the order of the wavelength of the light being used.
  • System 100 further includes a translation mechanism 53 that is mechanically connected to platform 2 and serves to move platform 2 holding wafer Id. In accordance with commands from computer 10, translation mechanism 53 causes platform 2 to move.
  • Computer 10 is also electrically connected to a synchronization circuit 59 via an electrical connector 57. Synchronization circuit 59 in turn is electrically connected to light source 3.
  • synchronization circuit 59 Upon command from computer 10 and propagated via electrical connection 57, synchronization circuit 59 sends one or more synchronization signals to light source 3 that cause light source 3 to emit one or more pulses of light.
  • synchronization circuit 59 By coordinating motion of wafer Id and the synchronization signals sent to synchronization circuit 59, minimally sized illumination spots are formed on wafer Id. In the absence of relative motion of wafer Id, each of the one or more pulses of light forms a small spot on wafer Id, where the size of each spot is determined largely by the specific design configuration of line imaging spectrometer 11 and the pixel dimensions of two-dimensional imager 8. The nominal size of each measurement spot is approximately 50 um.
  • a scan time is defined as the time necessary for system 100 to acquire data from the regions of interest of wafer Id, i.e. by sequentially imaging areas across wafer Id.
  • a scan speed is the scan time divided by the length of the area being measured. For example, if entire wafer Id is the scan area, and 5 seconds is the scan time, then the scan speed is 40 mm/s, assuming a 200 mm diameter wafer.
  • scan speed refers to the speed with which an area on wafer Id is being imaged moves across wafer Id; whether wafer Id or light source 3 or line imaging spectrometer 11 moves does not matter.
  • two-dimensional imager 8 having a 1 ms integration time in the example above, the measurement spot for each measurement sweeps across an additional portion of wafer Id that extends for 40 um. This additional distance causes the detected reflectance spectrum to be a mixture of whatever film stacks the spot passed over during the integration time. However, by using short pulses of light, the additional distance is reduced. For example, a 10 us pulse width means that the additional distance less than 1 um, which is significantly less than the nominal spot size of 50 um. Imaging system 100 operates as follows.
  • Light from source 3 passes through fiber bundle 9, and impinges on a film contained on or in wafer Id.
  • the light reflects off the wafer and is received by lens assembly 4.
  • Lens assembly 4 focuses the light on slit 5.
  • Slit 5 receives the light and produces a line image of a corresponding line on the wafer Id.
  • the line image is arranged along a spatial dimension.
  • the line image is received by second lens assembly 6 and passed through diffraction grating 7.
  • Diffraction grating 7 receives the line image and dissects each subportion thereof into its constituent wavelength components, which are arranged along a spectral dimension. In one implementation, the spectral dimension is perpendicular to the spatial dimension.
  • the result is a two- dimensional spectral line image that is captured by two-dimensional imager 8 during the integration time.
  • the imager is a CCD
  • the spatial dimension is the horizontal dimension
  • the spectral dimension is the vertical dimension.
  • the spectral components at each horizontal CCD pixel location along the slit image are projected along the vertical dimension ofthe CCD array. Additional detail regarding the spectrometer 11 is illustrated in FIG. 2 in which, compared to FIG. 1, like elements are referenced with like identifying numerals.
  • reflected light for purposes of illustration, two rays of reflected light, identified with numerals 13a and 13b are shown separately
  • lens assembly 4 and focused onto slit 5.
  • Slit 5 forms a line image of the light in which the subportions of the line image are arranged along a spatial dimension.
  • the line image is directed to lens assembly 6.
  • Lens assembly 6 in turn directs the line image to diffraction grating 7.
  • Diffraction grating 7 dissects each subportion ofthe line image into its constituent wavelength components.
  • the wavelength components for a subportion of the line image are each arranged along a spectral dimension.
  • Two-dimensional imager 8 individually captures the wavelength components for the subportions of the line image during the integration time.
  • the wavelength components for ray 13a are individually captured by pixels 14a, 14b, and 14c, respectively.
  • the wavelength components for ray 13b are individually captured by pixels 15a, 15b, and 15c, respectively.
  • Imager 8 is preferably designed so that the vast majority of photons landing upon individual pixels wind up storing electrical charge only within the pixels that they land on.
  • common CCD design allows photons with large penetration depths (i.e., photons with long wavelength) to generate electrons far beneath the pixels that they land on, and then allows these electrons to wander up and to be collected by pixels neighboring the pixel that the photons originally entered the CCD through. This causes a reduction in image resolution and an increase in the apparent measurement spot size, but can be substantially reduced by proper CCD design (by reducing the migration length of electrons below the pixels, for example.) With reference to FIG. 1, the light source 3 and the platform 2 are moveable relative to one another.
  • platform 2 and spectrometer 11 are moveable in relation to one another.
  • the light source 3 and spectrometer 11 are stationary, and the platform is moveable in an X direction 12. Since the apparatus ofthe present invention is capable of obtaining a large number of measurements, prodigious quantities of data must be dealt with.
  • One way to limit the extent of such large quantities of data is to move platform 2 in a non-linear fashion. For example, platform 2 can be instructed to execute a large translational step to one particular location, then move in small translational steps over a region of wafer Id where measurements are desired, then make another large translational step to another region of wafer Id where more measurements are desired, and so on.
  • computer 10 sends commands to translation stage 53 that cause wafer Id on platform 2 on wafer station 1 to move.
  • computer 10 sends synchronization commands to synchronization circuit 59, which cause light source 3 to emit pulses of light that propagate fiber bundle 9 to wafer Id.
  • Computer 10 also sends configuration commands to two-dimensional imager 8 that include the integration time and a command to initiate data collection.
  • the pulses of light emitted by light source 3 are short enough compared to the speed of wafer Id that the light collected by one-spatial-dimension imaging spectrometer 11 comes from a minimally sized spot on wafer Id.
  • the pulses of light from light source 3 are synchronized with the integration time and the data acquisition command so that each pulse is emitted only during the integration time.
  • One-spatial-dimension imaging spectrometer 11 in turn communicates the spectral and spatial information to the computer 10 over one or more signal lines or through a wireless interface.
  • Spectral reflectance data is continually taken in this way while the wafer Id is moved under the one-spatial-dimension imaging spectrometer by the platform 2 under the action of translation stage 53 and upon command from computer 10.
  • the computer 10 uses the successively obtained one-dimensional spatial data to generate a two-spatial-dimension image.
  • the plurality of spectral reflectance images comprises a "hyperspectral image".
  • This two-dimensional map or hyperspectral image can be generated by assembling the measured signal intensity at a single wavelength at each location on the wafer into an image, while retaining the spatial relationship between image locations within each scan and from contiguous scan line to the next.
  • This two-dimensional image can then be analyzed to find pixels that correspond to specific locations on the wafer, and then the spectral reflectance data that is associated with these pixels can be analyzed using suitable techniques to arrive at an accurate estimate of the thickness of the film.
  • film thickness is determined by matching the measured spectrum to a theoretically or experimentally determined set of spectra for layers of different thicknesses.
  • a CCD-based one-spatial- dimension imaging spectrometer is illustrated and described as the means for determining the intensity of the reflected light as a function of wavelength, it should be appreciated that other means are possible for performing this function, and other types of one-spatial-dimension imaging spectrometers are possible than the type illustrated in the figure.
  • the foregoing embodiment is described with a preferred way of forming minimally sized spots on each wafer by synchronizing the emission of pulses of light with the integration time of two-dimensional imager 8 and with wafer motion.
  • alternate approaches that compensate for the relative wafer-to- imager motion also achieve the same ends.
  • the electrically actuated mirror includes a piezoelectric element mechanically connected to one edge of the mirror while the center of the mirror is secured to form a hinge that allows rotational motion about the center axis of the mirror so that the focal distance between the imaging system 11 and the wafer Id remains substantially the same.
  • the electrically actuated mirror Upon applying an electrical signal to the piezoelectric element, the electrically actuated mirror then deflects the light between wafer Id and the imaging system 11 such that the imaging system tracks the wafer motion during each integration period. Between integration periods, the mirror position is reset to begin tracking the proper wafer location for the following integration time.
  • Similar "wafer tracking" capabilities may be realized by displacing other optical elements, such as the slit 5.
  • the foregoing embodiment is described in the context of semiconductor wafers, and is illustrated in combination with a wafer transfer station for performing this function, it should be appreciated that it is possible to employ this embodiment in other contexts and in combination with other processing apparatus.
  • Other possible applications include providing thin film scratch resistant and/or antireflective optical coatings to automotive plastics, eyeglass lenses, and the like plastics packaging applications, and applications involving providing appropriate polyimide and resist thicknesses for flat panel display manufacturing.
  • any application or industrial process in which film measurement is desired is possible for use with the subject embodiment.
  • the primary advantages of the foregoing embodiment is that it is particularly well suited for real-time applications.
  • the one-spatial-dimension imaging spectrometer directly provides digitized values of intensity of the incoming light as a function of wavelength without requiring mechanical sweeping steps or the like.
  • digital CCD-based line-scan cameras are available with sufficient numbers of pixels so that resolution of measurement pads is possible.
  • the number of analytical and pattern recognition steps performed by the computer are limited to only a very few. This is because an image of the entire wafer is made, which eliminates complicated pattern recognition routines that are needed when only small areas of the wafers are viewed at any one time, as is the case with microscope-based instruments.
  • FIG. 3 A second embodiment of the subject invention, suitable for measuring transparent or semi-transparent films, such as dielectrics deposited upon patterned semiconductor wafers, is illustrated in FIG. 3 and designated as an imaging system 101 in which, compared to FIG. 1 and FIG. 2, like elements are referenced with like identifying numerals.
  • This embodiment is similar to the previous embodiment, with the exception that the wafer Id is in a vacuum process or transfer chamber 16, and the wafer motion required for scanning is provided by a transfer robotics assembly 17 that are used to move the wafer inside a vacuum chamber 16. Vacuum chamber 16 may be used for processing wafers, or for transferring wafers. Transfer robotics assembly 17 allows the wafer Id to move in the X direction relative to light source 3 and spectrometer 11.
  • a viewport 18 Visual access to the wafer Id is provided by a viewport 18. More specifically, light from light source 3 is directed to impinge upon wafer Id via fiber bundle 9 through viewport 18. In addition, light reflected from wafer Id is received by spectrometer 11 after passage through viewport 18. As transfer robotics assembly 17 moves the wafer Id through the vacuum chamber 16 as part of the CVD process, spectral measurements are successively taken from successive portions of wafer Id and provided to computer 10. Transfer robotics assembly 17 further serves to orient wafer Id so that patterned features such as arrays of conductive lines are oriented to be co-planar with a plane defined by the wafer normal and the optical axis of spectrometer 11, which consequently enhances the precision with which film thickness measurements can be made.
  • the plurality of spectral reflectance images of the patterned semiconductor wafer or portions of the wafer comprises a
  • Computer 10 may successively perform calculations on the data as it is received or may do so after all or a substantial portion ofthe wafer Id has been scanned. As with the previous embodiment, computer 10 may use this data to estimate film thickness.
  • this embodiment has the additional advantage of providing rapid in-line film thickness measurements taken during the normal transfer motion of the wafers between processes. This means that measurements can be made without slowing down the process and thus will not negatively affect throughput. Also, because the unit is compact and can be integrated into existing equipment, very little additional cleanroom space is required. Additionally, because there are no added moving parts, the system is very reliable. Moreover, because this embodiment is disposed entirely outside of vacuum chamber 16, it introduces no particles or contamination to the fabrication process.
  • FIG. 4 An embodiment of a method in accordance with the invention is illustrated in FIG. 4. As illustrated, in step 20, a line image of a corresponding line of a film is formed. The line image has subportions arranged along a spatial dimension.
  • Step 20 is followed by step 21, in which subportions of the line image are individually dissected to their relevant constituent wavelength components.
  • the wavelength components for a subportion are arranged along a spectral dimension.
  • Step 21 is followed by step 22, in which data representative of the wavelength components of the subportions is individually formed.
  • the process may then be repeated for successive lines of the film until all or a selected portion of the film has been scanned. Throughout or at the conclusion of this process, estimates of film thickness or other film properties may be formed from the assembled data.
  • the light source 3 is a tungsten/halogen regulated light source, manufactured by Stocker & Yale, Inc. (Salem, NH).
  • Fiber/fiber bundle 9 in this embodiment is a bundle configured into a line of fibers to provide uniform illumination along the measured surface.
  • Several companies, Stocker & Yale being a prime example, manufacture such a fiber optic "line light”. This example is configured for use with CVD processing system Model
  • the line imaging spectrometer 11 in this example is manufactured by Filmetrics, Inc., San Diego, California, the assignee ofthe subject application.
  • the imager 8 is a CCD imager incorporating a time delay and integration line scan camera manufactured by Dalsa Inc., Part No. CT-E4-2048 that has a CCD imager with 2048 pixels in the system spatial direction and 96 pixels in the system spectral direction.
  • Optometrics (Ayer, MA) manufactures transmission diffraction grating 7 as Part No. 34-1211.
  • the lenses 4 and 6 are standard lenses designed for use with 35 mm-format cameras.
  • the line scan camera is custom-configured to operate in area-scan mode, with only the first 32 rows of pixels read out. This results in a data read rate greater than 1000 frames per second. Thirty-two rows of spectral data are sufficient for measurement of thicknesses in the range required for CVD deposited layers. It has been found that this example embodiment yields a thickness accuracy of +1 nm at a 1000 nm film thickness, at a rate of five seconds per wafer scan.
  • a commercial embodiment of a system according to the invention will now be described.
  • the manufacturers of the components of this system are as identified in the previous exception, with the exception of the lens assembly used in the spectrometer.
  • high quality lenses and mirrors manufactured by Optics 1 Thiand Oaks, CA
  • These lenses and mirrors are such that the modulation transfer function (MTF) for a plurality of alternating black and white line pair having a density of about 40 line pairs/mm. is greater than 70% over the entire wavelength range of interest.
  • MTF modulation transfer function
  • This system is configured to measure the thicknesses of individual layers of a sample, e.g., patterned semiconductor wafer, at desired measurement locations. The coordinates of these desired measurement locations are provided to the system.
  • the thickness of the wafer at each of these desired locations is determined by comparing the actual reflectance spectra for locations in a larger area containing the desired measurement location with a modeled reflectance spectra for the area assuming a particular layer thickness. If the comparison is within a desired tolerance, the assumed thickness is taken to be the actual thickness. If the comparison is not within the desired tolerance, the assumed thickness is varied, and the modeled reflectance spectra re-determined consistent with the newly assumed thickness. This process is continued until a comparison is performed which is within the desired tolerance. This process is repeated for a predetermined number, e.g. 5, of desired measurement locations on a layer ofthe wafer.
  • a predetermined number e.g. 5, of desired measurement locations on a layer ofthe wafer.
  • FIG. 5A illustrates a top view ofthe wafer 500.
  • the wafer 500 may be divided up into individual dies 502a, 502b, and 502c.
  • a plurality of predetermined measurement locations 504a, 504b, and 504c may also be provided. These measurement locations are typically situated in areas on the surface of wafer 500 that are between adjacent dies. The reason is these areas tend to have areas designed for use as measurement locations. This can be seen from an examination of FIG. 5B, which illustrates an example of a cross-section of one of the dies of FIG. 5A.
  • the cross-section has three layers, identified from top to bottom respectively with identifying numerals 506a, 506b, and 506c.
  • a combination of features provided in layers 506b and 506c form field-effect transistors 514a, 514b, and 514c.
  • Layer 506c in this example provides doped regions 506a, 506b, 506c within a silicon substrate, where the doped regions 506a, 506b, 506c serve as the source/drain regions, respectively, of transistors 514a, 514b, and 514c.
  • Layer 506b in this example comprises regions 510a, 510b, 510c which serve at the gates, respectively, of transistors 514a, 514b, and 514c.
  • the topmost layer 506a provides metal contact regions 512a, 512b, 512c, which may be selectively connected to individual ones of gate regions 510a, 510b, 510c during the processing ofthe die.
  • This cross-section is built up layer by layer in the following order: 506c, 506b, and 506a.
  • 506c During or after the process of adding each of the layers, 506a, 506b, 506c, it may be desirable to measure the thickness of the layer at one or more points.
  • each ofthe layers includes features that make it difficult to precisely model the reflectance spectra at those locations.
  • layer 506c has source/drain regions 508a, 508b, and 508c; layer 506b has gate regions 510a, 510b, 510c; and layer 506a has contact regions 512a, 512b, and 512c.
  • predetermined measurement locations are determined in areas where there are typically fewer features present, thereby simplifying the modeling process.
  • examples of these locations are the locations identified with numerals 504a, 504b, and 504c. Most often, open areas approximately 100 ⁇ m x 100 ⁇ m are included in the wafer pattern design to serve as locations for film property measurements.
  • FIG. 6A illustrates an overall view of the commercial embodiment 600 of the system.
  • a wafer 500 is supported on platform 632.
  • a light source 604 directs light 630 to a plurality of locations 634 on the surface of the wafer 500, which, in the current commercial embodiment, is in the form of a line that spans the entire diameter of the wafer 500. It should be appreciated, however, that embodiments are possible where the plurality of locations 634 form an irregular or curved shape other than a line, or form a line which spans less than the full diameter of wafer 500.
  • a sensor 602 receives the reflected light from the one or more locations 634, and determines therefrom the reflectance spectra representative of each ofthe one or more locations.
  • the reflectance spectrum for a location is the spectrum of the intensity ofthe reflected light from the location as a function of wavelength, or some other wavelength-related parameter such as 1/ ⁇ , n/ ⁇ , nd/ ⁇ , or nd (cos ) / ⁇ where n is the index of refraction for the material making up the layer, ⁇ is wavelength, d is the thickness of the layer and ⁇ is the angle that the optical axis of spectrometer 11 makes with respect to the wafer normal.
  • An example of the reflectance spectrum for a location on the surface of wafer 500 may be as illustrated in FIG. 7.
  • the reflectance spectra for the plurality of locations 634 is provided to processor 606 over one or more signal lines 626, which may be implemented as a cable or other wired connection, or as a wireless connection or interface.
  • This data may be provided to the processor concunently with the capture of data from other locations on the surface of wafer 500. Alternatively, this transfer may be deferred until data for all or a substantial portion of the surface of wafer 500 has been captured.
  • a translation mechanism 608 is configured to relatively translate wafer 500 so that the incident light 630 can be scanned across the entirety of the surface of wafer 500.
  • the translation mechanism 608 may be under the control of processor 606 or some other control means.
  • Translation mechanism 608 has the further capability of orienting, under command of processor 606, wafer 500 so that the measurement plane is parallel with features such as parallel conductive lines in wafer 500 that may be present.
  • the wafer 500 need only be moved in the X direction, identified with numeral 636, but it should be appreciated that embodiments are possible in which other directions of scanning, or combinations of directions, are possible.
  • the wafer 500 may be scanned in its entirety by scanning one half of the wafer in the X direction, then translating the wafer in the Y direction (identified with numeral 638) so that the remaining un-scanned portion of the wafer 500 resides under the incident light, and then scanning the second half of the wafer 500 by translating the wafer 500 in the X direction.
  • the light source 604 and sensor 602 are in a fixed relationship relative to one another, and the translation mechanism 608 is configured to achieve relative translation between the sensor 602 and the wafer 500 by successively moving the platform 632 supporting the wafer 500 relative to the light source 604 and sensor 602 in the X direction, identified with numeral 636.
  • the translation mechanism 608 is configured to achieve relative translation between the sensor 602 and the wafer 500 by successively moving the platform 632 supporting the wafer 500 relative to the light source 604 and sensor 602 in the X direction, identified with numeral 636.
  • light source 604 and sensor 602 are moveable relative to the wafer 500 by moving the light source 604 and sensor 602 relative to the platform 632.
  • the light source 604 comprises a white light source 610, or at least a light source having wavelength components over a desired wavelength range.
  • light source 604 also includes a light shaper 612, which may be in the form of a fiber cable bundle where the individual fibers at the outer face 640 of the cable in aggregate form a rectangular shape as shown in FIG. 8.
  • the rectangular shape of outer face 640 serves to project light from source 610 onto the surface of wafer 500 in the form of a line in the Y direction that spans the full diameter of the wafer, which in the case of this example is 100 mm.
  • the sensor 602 in the current commercial embodiment includes a lens assembly 614 situated along the optical path traced by the reflected light 642 from the surface of wafer 500. This lens assembly 614 functions to reduce the size of the reflected light from about a 100 mm line to about a 26 mm line.
  • a slit 616, concave mirror 618, and convex mirror 620 are also included within sensor 602, and are also placed along the optical path traced by the reflected light 642. In the current commercial embodiment, these optical elements are placed after lens assembly 614 in the order shown in FIG. 6A.
  • the slit 616 functions to aperture the light emerging from lens assembly 614 so that it is in the form of a line
  • mirrors 618 and 620 function to direct the light so that it impinges upon transmission diffraction grating 622 which next appears along the optical path.
  • the entire lens/slit/minor assembly is of sufficient quality that the MTF for an alternating black and white line pattern having a density of 40 line pairs/mm is not less than 70%.
  • lens assembly 614, slit 616, and mirrors 618 and 620 are not essential to the invention, and that embodiments are possible where these components are avoided entirely, or where other optical components are included to perform the same or similar functions.
  • the light that impinges on diffraction grating 622 is located close to the CCD imager and is thus close to being focused back into the form of a line.
  • FIG. 6B The situation is as depicted in FIG. 6B in which, relative to FIG. 6A, like elements are identified with like reference numerals.
  • the reflected light 642 is also in the shape of a line, and after various resizing and shaping steps, impinges upon diffraction grating 622.
  • the line 644 is divisible into portions, each of which is representative of conesponding portions of wafer 500 along line
  • portion 644a of the light impinging on diffraction grating 622 is representative of portion 634a of wafer 500
  • portion 644b of the impinging light on diffraction grating 500 is representative of portion 634b of wafer 500.
  • Diffraction grating 622 breaks each of the individual portions of line 644 into their constituent wavelengths.
  • grating 622 breaks portion 644a into n wavelength components, ⁇ o, ..., ⁇ n - ⁇ , identified respectively with numerals 644a(0), . .
  • imager 624 has a resolution of 2048 pixels by 96 pixels, although in the current commercial embodiment, only 32 pixels in the vertical (spectral) dimension are used.
  • the slit 616 in the spectral dimension determines the measurement spot size in the direction perpendicular to the line image, and it was chosen so that the spot size is 50 ⁇ m in this dimension as well, so the resulting measurement spot size is approximately 50 ⁇ m x 50 ⁇ m square over the entire 100 mm line being measured on the wafer.
  • Additional commercial embodiments such as the Filmetrics STMapper, measure larger wafers with the same sensors by simply mounting multiple sensors side-by-side to measure contiguous 100-mm-wide swathes of the wafers simultaneously. For example, the very common 200 mm diameter wafers are measured by mounting two sensors side-by-side, and the larger 300 mm diameter wafers are measured by mounting three sensors side-by-side.
  • the processor 606 has access to the reflectance spectra for all or a substantial portion ofthe entire surface of wafer 500. This data can be depicted as shown in FIG. 9A.
  • Numeral 900a identifies the reflectance data for points on wafer 500 for the first wavelength component, ⁇ 0 ; numeral 900b identifies the reflectance data for the second wavelength component, ⁇ ls and numeral 900c identifies the reflectance data for the (n-l) th wavelength component, ⁇ n - ⁇ .
  • reflectance data 900a in combination with off-wafer data points for the first wavelength component ⁇ o comprises reflection data 910a.
  • Reflectance data 900b in combination with off-wafer data points for the second wavelength component ⁇ 2 comprises reflection data 910b.
  • reflectance data 900c in combination with off-wafer data points for the first wavelength component ⁇ n -i comprises reflection data 910c.
  • the ensemble of reflectance data 910 comprises a hyperspectral image 920, shown in FIG. 9B.
  • the wavelength components identified with numerals 902a, 902b, and 902c collectively constitute the reflectance spectrum for a site on the surface of the wafer 500. Cunently, about 1 Gbyte of data is generated for each layer, so the processor must include a storage device that is capable of storing this quantity of data.
  • processor 606 is configured to analyze the data and determine therefrom the thickness of the layer at one or more desired measurement locations.
  • the coordinates of these measurement locations are known, and accessible to the processor 606.
  • the processor 606 also has access to information that describes the structure of the wafer at the desired measurement locations sufficiently to allow the reflectance spectra at the desired locations, or the immediately sunounding areas, to be accurately modeled.
  • Such information might include the composition of the layer in question and that of any layers below the layer in question, a description of any features, such as metal leads and the like, present in the layer in question and in any layers below the layer in question, and the thicknesses of any layers below the layer in question.
  • the processor 606 For each of the desired measurement locations, the processor 606 is configured to use this information to model the reflectance spectrum of that location, or surrounding areas, assuming a thickness for the layer in question.
  • the processor 606 is further configured to compare the modeled spectrum for a desired measurement location, or sunounding locations, with the actual reflectance spectra for these locations, and if the modeled spectra is within a defined tolerance of the actual spectra, determine that the assumed layer thickness is the actual layer thickness. If the comparison is not within the defined tolerance for the measurement location in question, the processor 606 is configured to vary the assumed layer thickness, remodel the reflectance spectra using the assumed layer thickness, and then re-perform the comparison until the modeled data is within the prescribed tolerance.
  • the processor 606 is configured to repeat this process for each ofthe desired measurement locations on a layer.
  • the processor 606 performs the comparison over a 10 x 10 pixel area centered on the nominal position of the desired measurement location. Analysis of more than one pixel is generally required because there is some uncertainty in the exact location of the desired measurement spot relative to the acquired wafer image, due to image imperfections caused by wafer vibration or other non-idealities.
  • FIG. 10 illustrates the 10 x 10 pixel area sunounding the nominal desired measurement location 1000.
  • FIG. 10 (A) shows a portion 1005 of wafer 500 with the outline of pixels superimposed on portion 1005.
  • FIG. 10 (A) shows a portion 1005 of wafer 500 with the outline of pixels superimposed on portion 1005.
  • FIG. 10 (A) shows bond pad 1020 between die edge 1030 and die edge 1040.
  • a desired measurement site 1000 In the center of bond pad 1020 is a desired measurement site 1000.
  • FIG. 10 (B) shows an image of portion 1055 with the outline of pixels visible. The fill of each pixel represents the spectrum associated with each pixel; like fill indicates like spectra.
  • ⁇ is the difference between the modeled and actual intensities ofthe i th wavelength component for the pixel being analyzed
  • ABS is the absolute value function.
  • pixels conesponding to like spectra can be used to identify high contrast regions such as those found at the edge of die.
  • spectral signatures By looking for spectral signatures, one can identify key features such as bond pads. For example, an examination of a row 1060 leads to the signature of two high contrast regions with five pixels having the signature of streets in between. Likewise, an examination of a row
  • FIG. 11 is a flowchart of the method of operation followed by the cunent commercial embodiment for each layer in the sample being evaluated.
  • the sample may be a semiconductor wafer or some other sample.
  • step 1100 the reflectance spectra for a plurality of spatial locations on the surface of a sample are simultaneously captured.
  • the spatial locations may be in the form of a line, or some other shape, such as a curved shape, although in the cunent commercial embodiment, the locations are in the form of a line.
  • step 1004 an evaluation is made whether all or a substantial portion of the entire surface has been scanned. If not, step 1102 is performed.
  • a relative translation is performed between the surface of the sample and the light source and sensor used to perform the capture process.
  • Step 1100 is then re-performed, and this process repeated until all or a substantial portion ofthe entire surface ofthe layer has been scanned.
  • step 1106 is performed.
  • step 1106 the coordinates of a desired measurement location are used to locate the reflectance data for that location or a location within a sunounding area.
  • step 1108 is then performed.
  • step 1108 the reflectance data for the location or a location within the sunounding area is compared with modeled reflectance data for that location to determine if the modeled data and actual data are within a prescribed tolerance.
  • This modeled data is determined assuming a thickness for that layer at or near the desired measurement location. The closeness of the fit is evaluated in step 1112. If the fit is outside a prescribed tolerance, step 1110 is performed. In step 1110, the reflectance data for the location is re-modeled assuming a different layer thickness and/or the location from which the actual data is taken is varied. Steps 1108 and 1112 are then re-performed. This process then continues until the modeled data is within the prescribed tolerance of the actual data. Step 1114 is then performed. In step 1114, the assumed layer thickness for the modeled data that satisfied the tolerance criteria in step 1112 is taken to be the actual layer thickness at the desired location. Step 1116 is then performed.
  • step 1116 it is determined whether there are additional desired measurement locations for the layer in question. If so, a jump is made back to step 1106, and the process then repeats from that point on for the next location. If not, the process ends.
  • a variation on the method shown in the flowchart in FIG. 11 is insert a step prior to step 1100 that includes a rapid scan of all or part of the sample, and an analysis to assess whether the sensitivity of the detector has been set properly.
  • This analysis involves comparing the intensity recorded by each pixel to the maximum possible, and if the maximum such intensity is within a pre-determined range that optimizes the measurements, then the logic of the method proceeds to step 1100; otherwise the sensitivity is adjusted to ensure that maximum intensity measurements obtained in step 1100 do fall within the pre-determined range at which point the logic ofthe method proceeds to step 1100.
  • FIG. 12 shows system 102, which is identical to system 100 except for the addition of a polarizer 1210 and a rotating analyzer 1220 and software in computer 10 to control rotating polarizer 1220 and to analyze the data obtained with system 102.
  • Polarizer 1210 is a linear polarizer having a polarization axis that defines the polarization angle of maximum transmission.
  • Polarizer 1210 is disposed between light source 3 and optical fiber 9 and serves to ensure that light emitted from light source 3 impinges upon wafer Id linearly polarized.
  • rotating analyzer 1220 has a polarization axis that defines the polarization angle of maximum transmission.
  • Rotating analyzer 1220 further includes a rotation mechanism controllable by computer 10 such that the polarization angle of rotating analyzer 1220 is known.
  • System 102 operates to collect light reflected from wafer Id identically to system 100 except for the effects of using polarized light and the algorithms used to infer film characteristics such as film thickness. Light impinging upon wafer Id is polarized due to polarizer 1210 and the light reflecting from wafer Id undergoes polarization shifts according the film properties on wafer Id.
  • Rotating analyzer 1220 transmits light reflected from wafer Id in accordance with the polarization axis of rotating analyzer 1220.
  • the light continues to propagate through line imaging spectrometer 11 to two-dimensional imager 8 where it forms a polarized line image. Since analyzer 1220 rotates, it alternately passes s- polarized and p-polarized light. By sequentially capturing s-polarized and p- polarized light, spatial maps of ⁇ and ⁇ can be generated from which, using well known methods, film properties such as thickness can be determined for each point and thus for all or portions of wafer Id. It is also important that data acquisition from two-dimensional imager 8 be synchronized with the velocity of wafer Id so that alternating frames of data conesponding to s- and p-polarized light, can be aligned so that rows of s- and p- polarized data overlap.
  • Previously discussed light strobing and/or wafer tracking methods can be used. Ellipsometric measurements can also be made using alternate configurations. If polarizer 1210 and analyzer 1220 are replaced with a rotating polarizer and a fixed analyzer respectively, then a rotating polarizer configuration is obtained. The operation of such a configuration is basically the same except that the polarization of the incident light is modulated before reflecting from the surface of wafer Id and being analyzed by the fixed analyzer and recorded by two-dimensional imager 8. The foregoing embodiment is described such that s- and p-polarized light is sensed in sequentially alternating frames.
  • a dual sensor anangement can be used, as shown in FIG. 21 as imaging system 104.
  • light reflected from wafer Id passes through a non-polarizing beamsplitter 2110 before being analyzed and detected.
  • Beamsplitter 2110 is disposed within system 102 so that light reflected by the beamsplitter remains in the plane defined by angle ⁇ .
  • Line imaging spectrometer 11s Light passing through the beamsplitter is analyzed by a line imaging spectrometer 11s for s-polarized light, where line imaging spectrometer 11s is identical to line imaging spectrometer 11 except that rotating analyzer 1220 is replaced by a fixed analyzer 1220s that is oriented to pass s-polarized light. Light reflected by beamsplitter
  • second line imaging spectrometer lip for p-polarized light is analyzed by a second line imaging spectrometer lip for p-polarized light, where second line imaging spectrometer lip is identical to line imaging spectrometer 11s except that it includes a fixed analyzer 1220p that is oriented to pass p-polarized light.
  • the other elements of second line imaging spectrometer lip (enumerated in FIG. 21 with a suffix 'p') are duplicates of like identified elements of line imaging spectrometer 11s.
  • images captured with the two line imaging spectrometers can be disposed within system 104 so that s-polarized and p- polarized measurements of the same locations on wafer Id are substantially aligned.
  • ellipsometric measurement anangements can also be accomplished using the basic structure of system 100 with suitable modifications.
  • Such ellipsometric measurement anangements are well known in the art and include a rotating compensator ellipsometer (which require a nanow spectrum light source for effective operation), a polarization modulation ellipsometer, and a null ellipsometer.
  • FIG. 13 shows a variable angle spectroscopic ellipsometer 103, which is yet another type of wide-area high-speed, high-resolution imaging ellipsometric imager that can be made.
  • Ellipsometer 103 is identical to ellipsometer 102 except for the addition of angle track 1330.
  • Ellipsometer 103 functions in the same way as ellipsometer 102 except that it allows ⁇ and ⁇ to be measured over a range of angles ⁇ .
  • ellipsometric images are obtained at a fixed angle ⁇ , then ⁇ is adjusted to a different angle and another set of ellipsometric images are collected. This process continues over a range of angles that depends on the materials being measured.
  • the apparatus of the present invention can also be used to rapidly perform measurements to determine erosion, which occurs during CMP.
  • Erosion is the excess removal of material in an anay of metal lines or vias, and involves the removal of both metal and dielectric material though in unequal proportions. If too much metal is removed, then the integrated circuit so formed is subject to numerous performance issues ranging from degraded performance due to increased capacitance affecting RC-time constants to joule-heating failures arising from excessive reduction of the cross sectional area of metal lines (Bret W. Adams, et al., "Full-Wafer Endpoint Detection Improves Process Control in Copper CMP", Semiconductor Fabtech Vol..12, p.283, 2000).
  • the reflectance apparatus of the present invention is used to shine light onto an anay of metal lines following a CMP step, where the incident light is in a plane parallel to the lines and perpendicular to the anay of metal lines. Once such light is incident upon an anay of metal lines, film thickness measurements of the top-most layer can be made at multiple locations on the image of wafer Id adjacent to and including a desired measurement site. These thickness measurements are obtained from between metal lines or vias.
  • FIG. 14 shows an example patterned film structure 1400 that includes an anay of copper lines 1410a - 1410d sunounded by silicon dioxide 1420 over a thin layer of silicon nitride 1430 and a second layer of silicon dioxide 1440 and a silicon substrate 1450.
  • FIG. 14 shows an example patterned film structure 1400 that includes an anay of copper lines 1410a - 1410d sunounded by silicon dioxide 1420 over a thin layer of silicon nitride 1430 and a second layer of silicon dioxide 1440 and a silicon substrate 1450.
  • FIG. 14 (A) shows incident light rays 1460, 1462, and 1464 striking patterned structure 1400 at a range of relatively large incident angles.
  • Incident light rays 1460, 1462, and 1464 strike copper lines 1410a - 1410c at sidewalls 1412a and 1412b and at underside 1412c respectively. For simplicity no refractive or diffractive effects are included though they would be present.
  • light ray 1460 strikes copper line 1410a at sidewall 1412a, and reflects off substrate 1450 before passing between copper line 1410a and 1410b before leaving patterned structure 1400.
  • Light ray 1462 demonstrates different behavior in that after reflecting off sidewall 1412b of copper line 1410b and substrate 1450 it reflects off underside 1412c of copper line 1410c, which leads to a second reflection off substrate 1450 before exiting patterned structure 1400.
  • a multiplicity of reflections between copper lines 1410 and substrate 1450 is possible, each reflection of which introduces increased dependence of the reflectance spectrum upon the copper lines.
  • Light ray 1464 which has a relatively large incident angle, undergoes a single reflection off substrate 1450 before exiting patterned structure 1400.
  • Light rays 1460 and 1462 have optical path lengths that depend significantly upon parameters of the copper lines such as width, thickness, and sidewall angle. Consequently, the overall reflectance signal depends significantly upon these physical parameters.
  • FIG. 14 (B) shows that light with a small NA incident at small angles leads to a high percentage of light passing by copper lines 1410 with reduced deflections off sidewalls 1412, reflecting off substrate 1450, and passing again between copper lines 1410 with substantially reduced reflections off of sidewalls 1412.
  • small NA light rays incident at a small angle the extent of the variation of reflections due to variation of patterned features such as copper lines 1410 is minimized, which leads to significantly reduced sensitivity of the reflectance spectrum to variations in the copper line dimensions. This means that erosion can be measured with this simple system without undue sensitivity or interference from variations in metal line dimensions.
  • the metal lines still have to be accounted for when modeling the wafer structure to determine the thickness of the top oxide layer using well-known methods such as Rigorous Coupled Wave
  • RCWA Integrated Circuit Analysis
  • Normally encountered variations in the metal dimensions are typically not enough to cause inaccuracies in oxide thickness determination.
  • high-NA measurement systems such as those previously mentioned that use microscope objectives to acquire spectral reflectance from a single point, are much more sensitive to variations in metal line dimensions because of the effect such variations have on the overall reflectance.
  • the reflectance of light incident upon an anay of lines such as copper lines 1410 depends in part upon the polarization ofthe incident light and the orientation of copper lines 1410. Copper lines 1410 thus behave like a wire grid polarizer, as described in US 6,532,111.
  • the polarization ofthe light in apparatus 100 may be restricted to one polarization and this effect may be used advantageously in combination with the advantages of the low NA, low incident angle light in analyzing three-dimensional structures. If the incident light in system 102 is linearly polarized as a result of polarizer 1020 so that the light has an electric field nominally perpendicular to copper lines 1410, then the light passes easily into the patterned structure 1400 where it reflects and again passes easily out of patterned structure 1400. If the incident light has an electric field nominally parallel to copper lines 1410, then a greater portion of the light reflects from the patterned structure 1410 compared to the case of light with an electric field perpendicular to copper lines 1410.
  • Anays of conductive lines on a patterned semiconductor wafer are almost always parallel or perpendicular to a notch line extending from the wafer center to the notch.
  • each metallization layer generally has almost all lines oriented in the same direction.
  • platform 2 can be used to rotate wafer Id so that the metal lines are parallel to the electric field ofthe polarized light so the ensuing measurements are more sensitive to light reflecting off of the top of the metal features.
  • FIG. 15 shows an example of how the apparatus ofthe present invention is used to determine erosion.
  • FIG. 15 shows a patterned structure 1500 that has erosion.
  • This structure includes an anay of copper lines 1510 between which is silicon dioxide 1520.
  • the copper lines 1510 are on a layer of silicon nitride 1530 and a second layer of silicon dioxide 1540 on a substrate 1550.
  • a hyperspectral image of patterned structure 1500 includes reflectance due to light ray 1570 and 1575, where light ray 1570 passes between copper lines 1510 where there has been minimal erosion.
  • Light ray 1575 passes between copper lines 1510 where there has been substantial erosion.
  • step 1955 involves determining a first thickness of silicon dioxide 1520 from light ray 1570 and a second thickness value of silicon dioxide 1520 from light ray 1575, and calculating a net difference value between the first thickness value and the second thickness value.
  • the net difference value is the erosion.
  • the apparatus of the present invention can be used to conect for spectral overlap enors that distort the signal detected and cause enors.
  • ⁇ satisfies the grating equation
  • m ⁇ d (sin ⁇ + sin ⁇ )
  • m an integer
  • ⁇ the diffraction angle
  • d the grating period.
  • the number of orders that must be accounted for depends on the diffraction efficiency of diffraction grating 7 for each order, the range of wavelengths of light emitted by light source 3, and the range of wavelengths over which two- dimensional imager 8 is sensitive.
  • diffraction grating 7 scatters second order light from light having a wavelength of 400 nm into the same angle as first order light having a wavelength of 800 nm.
  • a pixel in two-dimensional imager 8 aligned to receive the 400 nm light also receives the 800 nm light.
  • light from wavelengths ranging from 400 nm to 500 nm is scattered onto pixels that receive light ranging from 800 nm to 1000 nm.
  • Method 1600 shown in FIG. 16 can be used. This method involves calibrating the response of two- dimensional imager 8 to second order diffracted light at several calibration wavelengths between the smallest wavelength of light that can be second order light and the upper limit of sensitivity ofthe detector. For example, if light source 3 has a minimum wavelength of 400 nm, and two-dimensional imager 8 has an upper limit of sensitivity of 1000 nm, then wavelengths in the range of 400 nm to 500 nm are selected. Any of a variety of light sources can be used to provide nanow band calibration light including lasers and light emitting diodes.
  • LEDs light emitting diodes
  • lasers can also be used, they suffer the disadvantage of being of such nanow bandwidth that the exact location of light incident upon two-dimensional imager 8 is not known other than that it falls within the pixel the light strikes.
  • LEDs normally have a bandwidth of 10 to 20 nm, which means that when such light strikes two-dimensional imager 8 it covers more than one pixel.
  • curve-fitting algorithms the exact location ofthe peak can be found.
  • FIG. 17 shows the effect of an un-conected spectral response curve and a conected spectral response curve.
  • a spectral response curve 1730 extends from ⁇ m ; n to 2 ⁇ m i n . In this wavelength range there is no spectral overlap. Above 2 ⁇ m j n is a spectral response curve 1770, which extends from 2 ⁇ m j n to ⁇ cut and includes both first and second order diffracted light. From equation (3) and from the figure, a portion ofthe light in this wavelength range must be subtracted from the total light detected to arrive at a conected spectral curve. Equivalently, spectral response curve 1760 results from first order spectral light whereas spectral response curve
  • Step 1610 of method 1600 involves selecting a calibration wavelength to use. Since the contributions due to second order effects tend to vary relatively smoothly over the affected range, it suffices to use approximately four calibration wavelengths in the range between the smallest wavelength and half the maximum wavelength at which the detector is sensitive. These wavelengths, designated as ⁇ i, ⁇ 2 , ⁇ 3 , and ⁇ 4 , are shown in FIG. 17.
  • Step 1620 of method 1600 involves directing the light into system 100 with light source 3 replaced by an LED emitting at a desired calibration wavelength. It should be noted that these calibration measurements can be performed with the angle ⁇ as small as zero degrees. Light at calibration wavelength ⁇ i leads to first order intensity 1705 and second order intensity 1735 at 2 ⁇ ].
  • Step 1630 of method 1600 involves sensing the light, including both first and second order wavelengths, and recording these measurements.
  • diffraction grating 7 is generates first and second order diffracted light that strikes two-dimensional imager 8 at two locations on two-dimensional imager 8. This measurement results in a curve with two sharp peaks, a first peak conesponding first order diffracted light and a second peak conesponding to second order diffracted light.
  • Step 1640 of method 1600 assesses whether sufficient different wavelengths of light have been used. If measurements at sufficient wavelengths have been made, then the logic of method 1600 moves to Step 1650; if not, then the logic of method 1600 moves to Step 1610 and another wavelength is chosen.
  • Step 1650 of method 1600 calculates a system response based on measurements obtained in Step 1630. For each intensity curve, i.e., for each calibration wavelength, the intensity values adjacent to a nominal peak that exceed a threshold value are selected.
  • a peak-finding algorithm is used to determine precisely each peak amplitude and wavelength, one for first order diffracted light and one for second order diffracted light. Such peak-finding algorithms are well known; examples of such algorithms include parabolic fitting and Gaussian fitting.
  • This peak-finding process is repeated for each calibration wavelength. Having obtained precise peak amplitudes and wavelengths for each first and second order calibration wavelengths of light, a ratio of the peak amplitude conesponding to first order diffracted light to the peak amplitude conesponding to second order light is calculated, viz.,
  • Step 1650 concludes by calculating the conection factor C( ⁇ ) by interpolating R;( ⁇ j) for wavelength values between ⁇ i and ⁇ N and extrapolating for wavelength values between 2 ⁇ m j n and ⁇ cut that lie outside the range ⁇ i and ⁇ w.
  • the result is a piece-wise continuous conection factor 1810 shown in FIG. 18.
  • Step 1650 concludes by storing the conection factor C( ⁇ ) in memory.
  • inegularities in the ensuing image may occur that cause image distortion. These inegularities result from non-constant wafer velocity during the measurement process.
  • the resulting image is either a circle (which is good), or an ellipse. Whether the semi-major axis of the ellipse is disposed along the direction of motion or transverse to it depends on the linear velocity. In either case, the streets are straight lines, but they do not intersect at right angles.
  • This distortion can be conected for by a linear remapping of the image using correction factors obtained by determining the length of the semi-major and semi-minor axes of the ellipse.
  • the distinctive character of the streets allows them to be identified.
  • tangents at the intersection of the chord and the streets can be formed. Alternate tangents point in the same direction because of the linear velocity, and they conespond to either horizontal or to vertical rows. These tangents depend only on the linear velocity of the wafer during the measurements, and on the sampling rate.
  • This algorithm is based on extracting information from a single chord. For a wafer moving at a constant velocity, this single measurement applies to the entire wafer. Any chord spanning the wafer thus contains sufficient information to extract the wafer velocity, and therefore to infer how to conect for it. Since this algorithm applies to a single chord, which is obtained in a short measurement time, it can be applied to small areas of the wafer and to situations where the motion is non-uniform. Examples of such motion include the motion that a wafer undergoes if being manipulated by a robot arm on an R- ⁇ stage, or on a CMP tool undergoing orbital, or rotational, or linear motion.
  • FIG. 19 shows reflectance data 1900 at an arbitrary wavelength that includes wafer image 1910 having a plurality of street images 1920, and a wafer edge image 1905. Street images 1920 appear as wavy lines due to non-uniform velocity.
  • the waviness provides a way to infer the precise amount of velocity non-uniformity. More importantly, the waviness in combination with the fact that the streets are actually straight can be used to conect for the non-uniform velocity. To conect for the distortion in wafer images, find selected features in key locations and examine tangent lines to the features at these points. There are two cases to consider: one, where the streets are actually oriented horizontally and vertically (conesponding to rotational angle ⁇ equal to 0°, 90°, 180°, or 270°); and two, where the streets are not so oriented.
  • the first step is to find wafer edge image 1905 by sequentially examining points from the edge of reflectance data 1910, for example by examining the points along the dotted line 1924 in the direction ofthe , line designated by the numeral 1973. Reflectance values conesponding to points off the wafer are less than a threshold value, which facilitates finding an edge point 1950 on wafer edge image 1905. Suitable threshold values range from 0.002 to 0.30, but a prefened value is 0.01. (This technique can be applied in other directions, e.g.
  • a tangent line I960 at edge point 1950 is created.
  • the additional points, in the presence of non-uniform motion, may include some curvature, which can be determined through the use of well- known curve-fitting algorithms.
  • a similar process leads to determining a tangent line 1966 at an edge point 1956.
  • the direction of tangent line 1960 is related to the angle of the edge of wafer 500 and the wafer velocity. This process works for all edge points except at the wafer top, the wafer bottom, and at the midpoints.
  • wafers include a notch to identify crystallographic orientation, the very high resolution of images formed with the apparatus of the present invention render this notch visible in wafer image 1910. Since wafers are usually loaded with the notch in a given position, the image of the notch is likely to be in a conesponding position. (However, the notch position can differ from the alignment ofthe wafer patterning by as much a degree or two).
  • the reflectance data 1900 Begin with the reflectance data 1900, and start from the top of the image and move down until wafer edge image 1905 is detected, as described above. Examine the reflectance at all wavelengths and using the highest reflectance compared to the threshold value.
  • Wafer 500 has a center point whose location is known to within a couple of millimeters, so a wafer image center point 1980 is also known to within a few pixels.
  • To find the wafer image center 1980 of wafer image 1910 use chords across wafer image 1910.
  • the exact location of wafer image center 1980 is at the intersection of first diameter line and the second diameter line. If the first diameter line and the second diameter line are not the same (due to having walked upon the notch), then repeat the process of obtaining diameter lines along + 45 degree lines. Having found the edges of wafer image 1910, the notch is found as follows. After determining the wafer center location, start at the top of wafer image 1910 and move around either clockwise or counter-clockwise. Each step involves moving either one pixel left or right or one pixel up or down, depending on where the center of the wafer is. For example, if starting at the top of wafer image 1910 then the wafer center is directly below.
  • One way to find the notch involves examining the first derivative of the data.
  • the first derivative is highest at the edges ofthe notch, and yields a good approximate location for the notch.
  • To more precisely locate the notch once having found the notch using the first derivative apply well-known curve-fitting algorithms to' the tip ofthe notch.
  • the present invention further includes such a process, which is called an "autorotate" algorithm.
  • This algorithm involves accurately determining the rotational orientation of the hyperspectral image of wafer Id. This algorithm makes no assumption about spatial orientation, so this approach is particularly effective in processes such as CMP where wafers may slip during process. 5/083352
  • the method described here takes advantage of the fact that wafer pattern features align orthogonally due to the step and repeat nature of patterns on partially processed integrated circuits. This effect is especially apparent in the streets regions between the die.
  • a row or column summation preserves a signature indicative of these features.
  • the wafer pattern features are not aligned, then the elements of the resulting row or column summation are more of an average from a much greater variety of areas of the wafer, and thus maintain much less feature differentiation.
  • a single "Goodness-of- Alignment" value for a given orientation ofthe image of wafer Id by: summing all of the reflectance values along each row to form a sequence of row sums; forming a difference column by calculating the difference between adjacent elements ofthe sequence of row sums, and determining the Goodness-of- Alignment value for the given orientation of the image of wafer Id by summing each value in the difference row that exceeds a threshold value.
  • Determining the orientation of the image of wafer Id involves applying the above algorithm to the image of wafer Id over a range of image rotations to generate a series of Goodness-of-Alignment values for different rotational orientations of the image of wafer Id.
  • the rotations are performed by applying the appropriate mathematical transformations to the image of wafer Id.
  • FIG. 20 shows an example of the resultant Goodness-of-Alignment values as a function of rotational angle ⁇ . Notice that the Goodness-of-Alignment values have sharp maxima at ninety-degree intervals, which conespond to alignments between the pattern features and the rows and columns of the image of wafer Id. These peaks are seen in practice.
  • FIG. 20 shows an example of the resultant Goodness-of-Alignment values as a function of rotational angle ⁇ . Notice that the Goodness-of-Alignment values have sharp maxima at ninety-degree intervals, which conespond to alignments between the pattern features and the rows and
  • An alternate approach to orienting the streets in the auto-rotate algorithm involves using light in a single nanow band is used instead of using all of the light.
  • One suitable wavelength is 660 mn.
  • One example is to use a relatively blue wavelength, for example 410 nm, and a relatively red wavelength, e.g. 660 nm.
  • An optional step within the autorotate algorithm is to obtain a die signature.
  • pattern recognition techniques are used to identify in wafer image Id the locations of portions, e.g. quadrants of individual die. Unless each die is exactly symmetric about its center point, the reflectance in different quadrants of each die vary from quadrant to quadrant is asymmetric. These variations from quadrant to quadrant constitute a signature indicative of the orientation of each die.
  • An additional technique is to use the ratio of reflection intensities at different wavelengths as described above.
  • Rotational Auto-rotate method Yet another approach to obtaining an oriented wafer image is to analyze an image of a portion of a patterned wafer, where the portion of the wafer being examined includes a street at the radial distance from the wafer center, but at an unknown angle.
  • the nominal location of the wafer center is known to within tens of microns, but the notch is at an unknown angle albeit at a known radius.
  • the wafer center lies within a center die, and in the second situation a street (either horizontal or vertical) traverses the center of the wafer.
  • This rotational method of orienting wafers involves using system 100 to measure reference wafers and non- reference wafers with the same pattern as the reference wafer.
  • the rotational method includes positioning line imaging spectrometer 11 so that it images a portion of the wafer along a line perpendicular to a radial line extending from the center of wafer Id to the edge of wafer Id.
  • Line imaging spectrometer 11 substantially straddles the radial line. If dealing with the first situation where the center of the wafer falls within the center die, line imaging spectrometer 11 is disposed to image a portion of wafer Id at a half-die width equal to one half of the die height away from the wafer center.
  • the reflectance data pertains to light reflecting substantially from a street portion of wafer Id.
  • line imaging spectrometer 11 is disposed to straddle and to image the center of wafer Id.
  • the rotational method then involves rotating the wafer about its center point with line imaging spectrometer 11 held at the half-die width (situation one) or at the wafer center (situation two).
  • computer 10 records reflectance data sensed by line imaging spectrometer 11.
  • computer 10 forms an orientation signal by summing all the pixels in each row over all wavelengths.
  • a plot of the orientation signal as a function of rotational angle has peaks conesponding to the street being optimally aligned with the portion of wafer Id being imaged. For situation one, two peaks are present, thus providing orientation to within + 180 degrees. For situation two, four peaks are present if the wafer center aligns with the intersection of both vertical and horizontal streets; otherwise only two peaks are present.
  • a reference method is used. The reference method 5/083352 involves using the aforementioned rotational method to obtain a clear orientation signal refened that serves as a reference orientation signal, and is stored in memory.
  • test orientation signal A subsequent measurement on another wafer having the same pattern on it is then measured to obtain a test orientation signal that is compared with the reference orientation signal.
  • the test orientation signal is likely to exhibit a poorer quality indication that line imaging spectrometer 11 are aligned with the streets due to the uncertainty in the location ofthe wafer center.
  • the reference method can be used to determine the proper orientation ofthe wafer. Numerous techniques can be used to compare the test orientation signal with the reference orientation signal. One such technique is to use a one- dimensional cross-conelation function.
  • t(n) and r(n) are the test and reference orientation signals respectively
  • N is the number of pixels in a row
  • ⁇ is the conelation angle.
  • Another comparison technique involves calculating a difference between t(n) and r(n- ⁇ ) and identifying the minimum such difference as conesponding to the desired rotational angle. Additional techniques using the method of least squares can also be used.
  • the process of matching model spectra to measured spectra requires that the measured spectra are conect. It is also advantageous to perform the following calibration procedure to ensure that measured spectra are indeed mapped to the proper wavelengths.
  • the apparatus used for conecting for second order spectral overlap is used.
  • light source 3 of system 100 is replaced with an LED or with broadband light passed through a bandpass filter to produce light with a 10 - 20 nm bandwidth.
  • the spatial dimension is the horizontal dimension
  • the spectral dimension is the vertical dimension.
  • Light from the 10 - 20 nm light source should give a uniform response from two-dimensional imager 8.
  • the row element exhibiting the maximum response along the columns conesponding to the spectral dimension should be the same in each column across the spatial dimension of the anay.
  • Illumination with light having a 10 - 20 nm bandwidth is important so that several pixels sense the light, and well-known curve fitting algorithms can be used to find an exact peak location, thus improving the accuracy of the calibration procedure.
  • the wavelength can be conected by fitting the measured response to a second order polynomial. Repeating this calibration procedure at several wavelengths in the range of sensitivity of two-dimensional imager 8 maximizes the accuracy of the calibration. This calibration process can be done at different wavelengths sequentially, or simultaneously.
  • test sites which are bond-pad like features that are typically large compared to device features. Typically, many such sites are located on each wafer on which ICs are being fabricated. Since most existing tools for measuring test sites involve the time-consuming and hence expensive serial data acquisition, few test sites are measured due to the time-consuming nature of existing metrology techniques.
  • optical systems such as those described in the present invention involve an object (e.g. wafer) and a collection of optical elements disposed to create an image in an image plane that coincides with the sensing portion of a multiple-pixel, two-dimensional imager.
  • object e.g. wafer
  • collection of optical elements disposed to create an image in an image plane that coincides with the sensing portion of a multiple-pixel, two-dimensional imager.
  • Such systems also function in reverse, i.e., the collection of optical elements also images the multiple-pixel, two-dimensional imager (now viewed as an object) onto a second image plane that coincides with the plane of the wafer.
  • a measurement spot size be as small or smaller than the test site, and that one or more measurement spots lie substantially within the test site.
  • the measurement apparatus one uses determines this capability.
  • the minimum test site area that can be measured is determined by the measurement spot size, which is equal to the size ofthe "pixel image" that is imaged onto the wafer surface by the imaging system 100.
  • the pixel image size is primarily determined in the present invention in the horizontal direction by the pixel width multiplied by the product of the magnification of lens assembly 4 and the magnification of lens assembly 6 and in the scan direction by the slit width multiplied by the magnification of lens assembly 4.
  • the ability of a measurement system to measure a test site also depends on the measurement spot density, i.e., the number of measurements made per unit area on wafer Id.
  • the measurement spot density is determined primarily by the density of pixel images in the horizontal direction and the scan speed in the scan direction.
  • the measurement spot size and the measurement spot density are affected by the magnifications of the lenses 4 and 6.
  • the present invention involves performing sufficiently numerous measurements in a very short period of time that the very density of measurements combined with the small measurement spot size of individual measurements ensures that accurate measurements at desired test sites are made.
  • Methods already described in U.S. Patent Application Serial No. 09/899,383, and U.S. Patent Application Serial No. 09/611,219 address the issue of efficiently sifting through measurement data to extract measurements at desired test sites.
  • Standard solid-state imagers have rectangular pixels whose width is equal to the horizontal pixel pitch. This relationship implies a 100% fill factor, i.e., there is no portion ofthe sensing region ofthe imager that is not sensitive to light.
  • improving the measurement spot size requires innovation.
  • the measurement spot size depends in part on the orientation ofthe image of the measurement site compared to the orientation of the pixels in two- dimensional imager 8.
  • FIG. 22 (A) shows a 4x4 portion of a pixel anay 2210 of two-dimensional imager 8 that has a 100% fill factor, and where each pixel has a horizontal dimension 2220 and a vertical dimension 2230. If the measurement sites are optimally oriented, as shown in FIG. 22 (A), then the minimum measurement site image size is twice the pixel size. (Smaller site areas could straddle two pixels so that neither pixel would sense light from a single film stack, thus forming difficult or impossible to decipher measurements.) Pixel anay 2210 moves in a scan direction indicated by an anow designated by the numeral 2270.
  • a measurement site image 2240 Superimposed on anay 2210 is a measurement site image 2240. If the measurement site image size is any less than two times horizontal dimension 2220 or two times vertical dimension 2230 then there is a risk that a measurement will not include at least one pixel that is completely covered by the measurement site image. However, it cannot be assumed that the measurement sites are optimally oriented since there is uncertainty in the orientation of wafer Id on platform 2, even if wafer Id is oriented prior to being placed on platform 2. The worst-case scenario is that the measurement sites are oriented at a 45-degree angle, as shown in FIG. 22 (B), which shows a measurement site image 2250 oriented at a 45- degree angle to the pixels of pixel anay 2210.
  • Measurement site image 2250 has an edge dimension 2260 that has a minimum length of 2V2 times horizontal dimension 2220.
  • To deal with the worst-case scenario, and to meet or exceed the minimum measurement spot size involves reducing the active area of the pixels that receive light.
  • the present invention includes several techniques that provide for this capability. Pixel Masking Decreasing the active area of the pixels that receive light can reduce the measurement spot size. For optimal results, this approach involves reducing the active area in both the horizontal and vertical directions. Masking the pixel area can achieve this reduction in the horizontal dimension.
  • FIG. 23 (A) shows a pixel 2310 to which an opaque material has been applied to form a mask 2320 and a mask 2330 that block light from reaching the active portion of pixel 2310, thus fonning active area 2340 having a width 2345.
  • mask 2320 and mask 2330 near the outer edges of pixel 2310 optimizes the sensitivity of pixel 2310 to light and reduces electrical crosstalk between adjacent pixels, and it reduces resolution degradation caused by non-ideal optics (such as those that may be found in lens assemblies 4 and 6).
  • the opaque material that forms mask 2320 and mask 2330 is deposited during the fabrication of two-dimensional anay 8, using standard IC fabrication methods. Materials such as metals (alummum, gold, silver, etc.) are suitable opaque materials. Advantageously, such materials are anti-reflection (AR) coated to suppress reflections. In the vertical dimension masking can also be used to reduce the pixel area.
  • FIG. 24 (A) shows a 4x4 portion of a pixel anay 2410 of a two-dimensional imager that is identical to two-dimensional imager 8 except for the pixels being masked as shown in FIG. 23. Pixel masking results in a decrease in fill factor to the product of height
  • FIG. 24 (B) shows a measurement site image 2450 oriented at a 45-degree angle to the pixels of pixel anay 2410. Although measurement site image 2450 is nominally the same size as measurement site image 2250, measurement site image
  • FIG. 24 shows the reduction in measurement spot size due to reducing each edge of active pixel area by one half, which leads to a 25% fill factor.
  • a way to increase the probability that a measurement of wafer Id using system 100 actually results in a measurement of a desired measurement site is to increase the measurement spot density by reducing the scan speed relative to the data acquisition rate. Although it is intuitive to set the scan speed to result in a measurement spot density that is equal in directions both parallel to and perpendicular to the scan direction, decreasing the scan speed by a factor of two while maintaining the data acquisition rate increases the measurement spot density by a factor of two.
  • FIG. 25 shows measurement site image 2450 as well as pixel anay 2410 at two sequential integration times.
  • the first integration time conesponds to the dotted lines, and the second integration time conesponds to the solid lines.
  • a pixel 2520 and a pixel 2525 are entirely within measurement site image 2450.
  • a pixel 2510, a pixel 2515, a pixel 2530, and a pixel 2535 are entirely within measurement site image 2450.
  • An ensemble image comprised of images recorded at both the first and second integration times leads to an image that includes six pixels that are covered entirely by measurement site image 2450 measurement site image 2450, which is a significant increase in the probability that a single sweep of measurements across wafer Id results in high quality measurements at desired test sites. Further reducing the scan speed can lead to the case of "overlapping", i.e., where the measurement spots begin to overlay in the scan direction. Overlapping further reduces the minimum measurement site size. The example just described serves to show how a 50% reduction in scan speed doubles the number of measurements made during a single sweep across " wafer Id using system 100, thus increasing the spatial resolution of measurements. Further decreasing the available light sensitive area by scaling each pixel down is one way to obtain additional resolution.
  • Another way to obtain further increases in spatial resolution is to further reduce the active area of pixels by masking more of each pixel. Reducing height 2322 by adjusting blade 2350 and/or a blade 2360 appropriately leads to nominally square light sensitive regions. Further reducing the scan speed results in more measurements on wafer Id. Depending on how much masking is done it may be necessary to increase the intensity of light generated by light source 3. In operation, the scan speed is reduced to one half of its nominal speed. As wafer Id moves, light from light source 3 reflects off wafer Id and enters line imaging spectrometer 11 of system 100, where two-dimensional imager 8 has been replaced with two-dimensional imager 2410. Computer 10 receives spectral data from line imaging spectrometer 11, and generates spectral images of wafer Id from which the film thickness of a film at desired measurement sites is determined, as described in U.S. Patent Application Serial No. 09/899,383, and
  • each pixel is masked on a single side, as described above and using known methods. Adjacent rows are offset by the width of the mask.
  • FIG. 26 An example of a two-dimensional imager with staggered rows is shown in FIG. 26, which shows a portion of two-dimensional imager 2610 having a three-fold increase in measurement spot density in the horizontal direction.
  • pixels disposed along the horizontal direction conespond to a spatial dimension and pixels disposed along the vertical direction conespond to the spectral dimension, as indicated in the figure.
  • Pixels in every third row sense light from the same physical location on wafer Id, but at different wavelengths.
  • two-dimensional imager 2610 includes a pixel row 2620 that includes a pixel 2650 having a width 2637 with a mask 2651 having a width 2647.
  • Two-dimensional imager 2610 further includes pixel rows 2622, 2624, 2626,
  • Pixel rows 2620, 2622, and 2624 form a row group 2670.
  • Pixel rows 2626, 2628, and 2630 form a row group 2672.
  • Pixel rows 2632, 2634, and 2636 form a row group 2674.
  • pixel row 2622 and pixel row 2624 of row group 2670 include a pixel 2652 and a pixel 2654 respectively.
  • Pixel row 2672 include a pixel 2656, a pixel 2658, and a pixel 2660 respectively.
  • Pixel row 2632, pixel row 2634, and pixel row 2636 of row group 2674 include a pixel 2662, a pixel 2664, and a pixel 2666 respectively.
  • Each pixel dimension as well as the dimensions and position of the mask on each pixel of each row is identical to that of pixel 2651 and mask 2647. Width
  • two-dimensional imager 2610 includes 32 row groups. If each row group includes three pixel rows per row group, then 96 rows are needed to provide spectral measurements at 32 distinct wavelengths. Individual pixel rows receive light at slightly a different wavelength than adjacent pixel rows. This difference is small, and even though it does mean that physically adjacent points have 32-point spectra associated with them, there is a slight shift in wavelength from site to adjacent site.
  • Wafer Paddle Motion Damper The process of acquiring high-speed, high-density reflectance data from a patterned wafer involves sensing light reflected from the surface of the patterned wafer. Since the wafer must move relatively to light source 3 and line imaging spectrometer 11, there is opportunity for such relative motion to degrade the sensed reflectance due to increased measurement area. Typically, such unwanted motion is in a direction transverse to the X direction 12. To suppress such undesirable motion the present invention provides for a mechanism that reduces this motion. As shown in FIG. 28 (A), platform 2 of system 100 further includes an arm 2810 to which a wand 2820 is mechanically attached. Wand 2820 serves to secure wafer Id.
  • platform 2 further includes a fixture 2850 that serves to limit unwanted motion while simultaneously allowing wafer Id to be translated in the X direction 12 upon command from computer 10.
  • FIG. 28 shows three exemplary ways limit unwanted motion.
  • FIG. 28 (B) shows fixture 2850 in cross section, and in particular shows a groove 2860 that has been formed in fixture 2850. Groove 2860 is formed to conform to the shape of arm 2810 so that as computer 10 causes translation mechanism 53 to move wafer Id, arm 2810 moves along fixture in the X direction 12. Motion in directipns transverse to the X direction 12 is suppressed by groove 2860 and by slight downward pressure applied by translation mechanism 53 to keep arm 2810 in groove 2860.
  • groove 2860 is shown as being rectangular, a wide variety of other shapes also work provided that they conform to the shape of arm 2810.
  • Example cross-sectional shapes include round, triangular, etc. In practice, only nominal shape conformality is needed: so long as at least two portions of groove 2860 are present that present stable supporting points that limit the transverse motion of arm 2810 in groove 2860, the objective of stabilizing the motion of wafer Id is satisfied.
  • the use of TeflonTM or wheels or bearings can also be used to reduce the sliding friction.
  • FIG. 28 (C) shows a variation on the embodiment shown in FIG. 28 (B) wherein arm 2810 has been modified to include a beveled edge 2852 and a beveled edge 2854, thus forming arm 2810a.
  • Fixture 2850 has been likewise modified to include a beveled edge 2856 and a beveled edge 2858 that match beveled edges 2852 and 2854 respectively.
  • the addition of these beveled edges further restricts translational motion while facilitating the ability of translational mechanism 53 to position arm 2810 within groove 2860 of fixture 2850.
  • FIG. 28 (D) shows yet another way to stabilize transverse motion.
  • An arm 2810b is formed by modifying arm 2810 to include a magnet 2870 disposed substantially within arm 2810c, as shown in FIG. 28 (D). Magnet 2870 is oriented so that one pole, designated with a "+" in FIG. 28 (D), is oriented away from ann 2810b.
  • a fixture 2850b is formed by disposing a magnet 2872 within fixture 2850b so that magnet 2872 is flush with the surface of a groove 2860b, as shown in the figure.
  • Magnet 2872 is oriented so that one pole, designated with a "+" in FIG. 28 (D), is oriented toward arm 2810b.
  • Essential to the operation of this embodiment is that like poles face each other so as to form a magnetic bearing.
  • translation mechanism 53 presses arm 2810b into groove 2860 and the opposing force induced by the close proximity of like poles in magnets 2870 and 1872 along with the structure of groove 2860b suppresses transverse motion.
  • FIG. 28 (C) Considerable variations on the embodiment shown in FIG. 28 (C) are possible.
  • the present invention further provides enhanced visibility of wafer Id when using system 101 in FIG. 3.
  • implementing viewport 18 with a bi-planar glass plate leads to a degraded image due to wavelength dependent optical path length differences (dispersion) as light refracts through viewport 18.
  • Coating viewport 18 with an AR coating is not sufficient to solve the problem.
  • viewport 18 is treated as an integral component of the optical elements used in system 101, and the optical design parameters of lens assembly 4, and lens assembly 6 if necessary, are adjusted to compensate for the dispersion in viewport 18.
  • designing lens assembly 4 so that is takes into account the optical effects of viewport 18 can result in non-degraded images.
  • viewport 18 can be viewed as having a top surface 18t with a curvature Rt, and a bottom surface 18b having a curvature Rb, and the design process can be performed to optimize curvature Rt of top surface 18t, and/or optimizing curvature Rb of bottom surface 18b.
  • FIG. 29 shows system 105, which is identical to system 101 except that lens assembly 4 and viewport 18 have been replaced with lens assembly 4' that combines the functionality of lens assembly 4 and viewport 18 into a single element.
  • Fiber bundle 9 has also been modified so that it is optically and mechanically coupled to transfer chamber 16.
  • Lens assembly 4' includes one or more lenses, each having front and back surfaces having curvature that is optimized to provide a clear image ofthe portion of wafer Id being illuminated by light source 3.
  • the operation of system 105 is identical to that of system 101. Dual-Offner:
  • the need for obtaining measurements on very small measurement sites on wafers drives two conflicting factors.
  • One factor is the need for sensing light from very small areas without optical contamination from nearby areas, and the second factor is the need for simple, low-cost optics.
  • Conventional single-spot microscope-based measurement systems typically use refractive (i.e., transmissive) lens systems to provide a small, well-defined measurement spot.
  • refractive lens systems are complex and expensive because the refractive index ofthe glass materials used to make the lenses varies with wavelength, and to be able to image a small spot over a wide range of wavelengths requires a lens system that consists of numerous (typically five or more) precision lenses that are positioned in a low-tolerance assembly.
  • the optical system for an imaging spectrometer is even more complex and expensive because the size of the area that they must image precisely is several orders of magnitude larger than that of a single-spot system (because each line image consists of thousands ofthe single-spot sized images.)
  • the optical systems of the resolution required for the imaging micron-sized structures such as those found on ICs include three or more concave and convex minors that are set at precise angles to one another, which adds to the parts cost and increases the complexity of assembly due to tight alignment tolerances, which further increases system cost.
  • such systems typically include at least one minor element that is not spherical (i.e., that is aspherical), which adds significantly to the cost.
  • the detector pixel size is comparable to the size of the measurement pads, which means that imaging with a magnification of approximately 1 : 1 is needed.
  • optical systems that use reflection alone eliminate the dispersion associated with refractive optics.
  • the use of reflective surfaces alone is insufficient to address the above problems. Such surfaces must also minimize optical defects such as spherical abenation and coma; otherwise the problem of wavelength dispersion is replaced by another problem, viz., image distortion.
  • An Offher imaging system is a catoptic system with unit magnification with high resolution provided by convex and concave spherical minors ananged with their centers of curvature at a single point.
  • Such systems use reflective optical elements configured to substantially eliminate spherical abenation, coma, and distortion. They are also free from third order astigmatism and field curvature.
  • magnification of approximately 1.2:1 can be used without excessively degrading optical performance.
  • the traditional Offher imaging system simply re-images abenant light from an object.
  • a first Offher system replaces lens 4 of system 100, i.e. it re-images light reflected from a wafer being tested onto a slit that performs a spatial filtering function.
  • a second Offher system replaces lens 6, and serves to re-image the spatially filtered light to the entrance aperture of a one-dimensional imaging system, which then disperses the light into its constituent wavelengths for subsequent analysis.
  • this dual- Offher system provides near defect free image light to the one-dimensional imaging system, thus essentially stripping the recorded image of abenations.
  • FIG. 30 shows a dual Offher imaging system 3100 according to the present invention that includes a folding minor 3170, a first Offher group 3103, a folding minor 3140, a slit 3130, a second Offher group 3105, and a one- dimensional imaging system 3190 having an entrance aperture.
  • Folding minor 3170 and folding minor 3130 are front surface minors that serve to fold the optical path of light emanating from wafer Id to reduce the size of dual Offher imaging system 3100.
  • Slit 3130 is an adjustable mechanical assembly having a pair of straight edges opposing each other and adjustable to maintain a fixed distance between the straight edges.
  • One-dimensional imaging system 3190 has an entrance aperture that receives light.
  • First Offher group 3103 includes a convex minor 3160 and a concave minor 3150, both of which have a radius of curvature and a focal point located at the center of curvature. Convex minor 3160 and concave minor 3150 are disposed within system 3100 so that their focal points are coincident. First Offher group 3103 has a focal point 3180 and a focal point 3182. Second Offher group 3105 includes a convex minor 3120 and a concave minor 3110, both of which have a radius of curvature and a focal point located at the center of curvature.
  • Convex minor 3120 and concave minor 3110 are disposed within. system 3100 so that their focal points are coincident.
  • Second Offher group 3105 has a focal point 3184 and a focal point 3186.
  • Second Offher group 3105 is disposed within system 3100 so that focal point 3182 and focal point 3184 coincide within slit 3140.
  • Focal point 3186 is disposed within system 3100 at the entrance aperture of one-dimensional imaging system 3180.
  • wafer Id is positioned within system 3100 so that portions of wafer Id that include one or more measurement test sites pass through focal point 3180 of first Offher group 3103.
  • Minor 3170 reflects light reflected from wafer Id at focal point 3180 and directs it toward concave minor 3150 whereupon it is reflected toward convex minor 3160. The light then undergoes a reflection back toward concave minor 3150, and in so doing it starts to converge. The light reflects off concave minor 3150 in a second reflection from this minor. Subsequent to this reflection, the light reflects off folding minor 3140, as it converges to focal point 3182.
  • the blades of slit 3130 having been adjusted to approximately 10 um of separation, spatially filter the light passing through slit
  • R- ⁇ stages also allow the overall system footprint of a given embodiment to be reduced compared to the system footprint using linear translation stages.
  • Implementing system 100, system 101, system 102, system 103, system 104, or system 105 with R- ⁇ stages involves moving one or both of optical system 11 wafer Id with the R- ⁇ stage. It should also be clear that the methods and embodiments of the present invention can be used to measure film properties on all or on only a portion of a wafer or other structure having a stack of thin films.

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Abstract

Système (100) permettant la cartographie à grande vitesse et à définition élevée de l'épaisseur (ou d'une autre propriété) de couches se trouvant sur des tranches à semi-conducteurs configurées (1d). Ce système comporte un ou plusieurs spectromètres (11) assurant chacun simultanément l'imagerie de plusieurs emplacements spatiaux. Selon un exemple, le spectromètre (11) comporte un appareil d'imagerie CCD bidimensionnelle (8) dont un axe mesure les données spectrales tandis que l'autre axe mesure les données spatiales. La réflectance spectrale ou la transmission de la tranche configurée (1d) faisant l'objet de l'essai est obtenue par passage de la tranche (1d) sous (ou sur) le ou les spectromètre(s) (11), et par prélèvement d'images séquentielles de réflectance ou d'émission pour plusieurs emplacements spatiaux successifs. La cartographie de réflectance spectrale ou d'émission ainsi obtenue peut ensuite subir une analyse en des emplacements discrets afin de déterminer les épaisseurs ou autres propriétés des couches au niveau de ces emplacements.
PCT/US2004/032692 2004-02-11 2004-09-30 Procede et appareil de cartographie d'epaisseur a grande vitesse pour couches minces configurees WO2005083352A1 (fr)

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WO2008015311A1 (fr) * 2006-08-03 2008-02-07 Chun Ye Procédé et équipement de mesure de fibres de pulpe intacte
EP1947445A1 (fr) * 2007-01-19 2008-07-23 Horiba Jobin Yvon S.A.S. Système et procédé d'analyse d'un échantillon
WO2014118469A1 (fr) * 2013-01-31 2014-08-07 Vit Systeme de determination d'une image tridimensionnelle d'un circuit electronique
WO2017055895A1 (fr) * 2015-09-30 2017-04-06 Arcelormittal Procédé de caractérisation en ligne d'une couche d'oxydes sur un substrat en acier
RU2745856C1 (ru) * 2018-01-18 2021-04-02 ДжФЕ СТИЛ КОРПОРЕЙШН Устройство спектрального анализа, способ спектрального анализа, способ производства стальной полосы и способ обеспечения качества стальной полосы
CN114526680A (zh) * 2022-01-27 2022-05-24 太原理工大学 一种基于反射光斑图像识别的薄冰厚度测量装置和测量方法
US11441893B2 (en) 2018-04-27 2022-09-13 Kla Corporation Multi-spot analysis system with multiple optical probes
US11555996B2 (en) * 2020-05-05 2023-01-17 National Chung Cheng University Method and system for analyzing 2D material thin film

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Cited By (19)

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Publication number Priority date Publication date Assignee Title
WO2008015311A1 (fr) * 2006-08-03 2008-02-07 Chun Ye Procédé et équipement de mesure de fibres de pulpe intacte
EP1947445A1 (fr) * 2007-01-19 2008-07-23 Horiba Jobin Yvon S.A.S. Système et procédé d'analyse d'un échantillon
WO2008087217A1 (fr) * 2007-01-19 2008-07-24 Horiba Jobin Yvon Sas Système et procédé permettant d'analyser un échantillon
US8310675B2 (en) 2007-01-19 2012-11-13 Horiba Jobin Yvon Sas System and process for analyzing a sample
WO2014118469A1 (fr) * 2013-01-31 2014-08-07 Vit Systeme de determination d'une image tridimensionnelle d'un circuit electronique
US20150365651A1 (en) * 2013-01-31 2015-12-17 Vit System for determining a three-dimensional image of an electronic circuit
CN105283732A (zh) * 2013-01-31 2016-01-27 维特公司 用于确定电子电路的三维图像的系统
WO2017056061A1 (fr) * 2015-09-30 2017-04-06 Arcelormittal Procédé pour la fabrication d'un produit en acier comprenant une étape de caractérisation d'une couche d'oxydes sur un substrat en acier en défilement
WO2017055895A1 (fr) * 2015-09-30 2017-04-06 Arcelormittal Procédé de caractérisation en ligne d'une couche d'oxydes sur un substrat en acier
KR20180048794A (ko) * 2015-09-30 2018-05-10 아르셀러미탈 주행하는 강 기재상에 산화물의 층의 특성화 단계를 포함하는 강 제품의 제조 방법
AU2016333018B2 (en) * 2015-09-30 2019-08-22 Arcelormittal Method for the fabrication of a steel product comprising a step of characterization of a layer of oxides on a running steel substrate
KR102116622B1 (ko) * 2015-09-30 2020-05-29 아르셀러미탈 주행하는 강 기재상에 산화물의 층의 특성화 단계를 포함하는 강 제품의 제조 방법
US10859370B2 (en) 2015-09-30 2020-12-08 Arcelormittal Method for the fabrication of a steel product comprising a step of characterization of a layer of oxides on a running steel substrate
RU2745856C1 (ru) * 2018-01-18 2021-04-02 ДжФЕ СТИЛ КОРПОРЕЙШН Устройство спектрального анализа, способ спектрального анализа, способ производства стальной полосы и способ обеспечения качества стальной полосы
US11255778B2 (en) 2018-01-18 2022-02-22 Jfe Steel Corporation Spectroscopic analysis apparatus, spectroscopic analysis method, steel strip production method, and steel strip quality assurance method
US11441893B2 (en) 2018-04-27 2022-09-13 Kla Corporation Multi-spot analysis system with multiple optical probes
US11555996B2 (en) * 2020-05-05 2023-01-17 National Chung Cheng University Method and system for analyzing 2D material thin film
CN114526680A (zh) * 2022-01-27 2022-05-24 太原理工大学 一种基于反射光斑图像识别的薄冰厚度测量装置和测量方法
CN114526680B (zh) * 2022-01-27 2023-07-14 太原理工大学 一种基于反射光斑图像识别的薄冰厚度测量装置和测量方法

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