WO2021197207A1 - Appareil de mesure de profil de surface - Google Patents

Appareil de mesure de profil de surface Download PDF

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Publication number
WO2021197207A1
WO2021197207A1 PCT/CN2021/083092 CN2021083092W WO2021197207A1 WO 2021197207 A1 WO2021197207 A1 WO 2021197207A1 CN 2021083092 W CN2021083092 W CN 2021083092W WO 2021197207 A1 WO2021197207 A1 WO 2021197207A1
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WIPO (PCT)
Prior art keywords
pinhole
light
pinholes
beam splitter
assembly
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PCT/CN2021/083092
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English (en)
Inventor
Zhongping Fang
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Elementary Optomation Co.Ltd
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Application filed by Elementary Optomation Co.Ltd filed Critical Elementary Optomation Co.Ltd
Priority to CN202180005935.7A priority Critical patent/CN114641667A/zh
Publication of WO2021197207A1 publication Critical patent/WO2021197207A1/fr

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    • 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
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • 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
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/0004—Microscopes specially adapted for specific applications
    • G02B21/0016—Technical microscopes, e.g. for inspection or measuring in industrial production processes
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/0004—Microscopes specially adapted for specific applications
    • G02B21/002—Scanning microscopes
    • G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
    • G02B21/0036—Scanning details, e.g. scanning stages
    • G02B21/0044—Scanning details, e.g. scanning stages moving apertures, e.g. Nipkow disks, rotating lens arrays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/0004—Microscopes specially adapted for specific applications
    • G02B21/002—Scanning microscopes
    • G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
    • G02B21/0052—Optical details of the image generation
    • G02B21/0064—Optical details of the image generation multi-spectral or wavelength-selective arrangements, e.g. wavelength fan-out, chromatic profiling
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
    • G01B2210/50—Using chromatic effects to achieve wavelength-dependent depth resolution
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/0004—Microscopes specially adapted for specific applications
    • G02B21/002—Scanning microscopes
    • G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
    • G02B21/0052—Optical details of the image generation
    • G02B21/006—Optical details of the image generation focusing arrangements; selection of the plane to be imaged

Definitions

  • the present disclosure generally relates to surface profile measurement. More particularly, the present disclosure describes various embodiments of an apparatus for measuring the surface profile of an object.
  • Surface profile of objects is an important property for quality inspection of the objects in many industries.
  • the surface profile of semiconductor devices such as wafers or substrates need to be measured and inspected as part of quality control and assurance processes.
  • One conventional way of measuring the surface profile of an object is by using confocal microscopy techniques. Specifically, confocal sensors are used to measure arbitrary points on the surface of the object to determine their relative heights on the surface. These point-by-point measurements are subsequently combined to estimate the surface profile of the object.
  • measuring of the surface profile is slow because of the time taken for point-by-point measurements of individual points on the surface.
  • the arbitrary points also do not cover all areas of the surface, potentially excluding relevant regions of interest of the surface profile.
  • an apparatus for measuring a surface profile of an object comprising:
  • a light source assembly comprising a broadband light source
  • a confocal microscopy assembly comprising:
  • a beam splitter for directing uniform light from the broadband light source to the object
  • a pinhole device comprising an array of pinholes, the pinhole device configured for passing the uniform light from the beam splitter through the pinholes to the object;
  • a set of incident optical elements for directing the uniform light from the pinhole device to the object and causing chromatic aberration of the uniform light passing through the incident optical elements
  • the pinhole device configured for passing light reflected from the object through the pinholes to the beam splitter, the reflected light comprising spectral information of the surface profile based on the chromatic aberration; and an optical detection assembly comprising:
  • an optical detector for receiving the reflected light from the beam splitter
  • a set of detection optical elements for directing the reflected light from the beam splitter to the optical detector
  • the surface profile of the object is measurable based on spectral information of the reflected light received by the optical detector, the spectral information representing heights across the surface profile.
  • Figure 1 is an illustration of an apparatus for measuring the surface profile of the object, the apparatus having a colour camera, according to some embodiments of the present disclosure.
  • Figure 2 is a flowchart illustration of a method for measuring the surface profile of the object, according to some embodiments of the present disclosure.
  • Figures 3 to 5 are illustrations of a pinhole device of the apparatus, according to some embodiments of the present disclosure.
  • Figure 6 is an illustration of a light source of the apparatus, according to some embodiments of the present disclosure.
  • Figure 7 is an illustration of a spectral image of the object captured by the apparatus, according to some embodiments of the present disclosure.
  • Figure 8 is an illustration of the apparatus in another configuration, according to some embodiments of the present disclosure.
  • Figure 9 is an illustration of another apparatus having a hyperspectral imaging assembly, according to some embodiments of the present disclosure.
  • Figure 10 is an illustration of a hyperspectral image of the object captured by the apparatus, according to some embodiments of the present disclosure.
  • Figure 11 is an illustration of another apparatus having the hyperspectral imaging assembly and configured for line scanning, according to some embodiments of the present disclosure.
  • Figure 12 is an illustration of the hyperspectral image of the object captured by the apparatus using line scanning, according to some embodiments of the present disclosure.
  • Figure 13 is an illustration of another apparatus having the hyperspectral imaging assembly and a Nipkow disk, according to some embodiments of the present disclosure.
  • Figures 14 and 15 are illustrations of the Nipkow disk, according to some embodiments of the present disclosure.
  • Figure 16 is an illustration of another apparatus having the colour camera and Nipkow disk, according to some embodiments of the present disclosure.
  • depiction of a given element or consideration or use of a particular element number in a particular figure or a reference thereto in corresponding descriptive material can encompass the same, an equivalent, or an analogous element or element number identified in another figure or descriptive material associated therewith.
  • the terms “a” and “an” are defined as one or more than one.
  • the use of “/” in a figure or associated text is understood to mean “and/or” unless otherwise indicated.
  • the term “set” is defined as a non-empty finite organization of elements that mathematically exhibits a cardinality of at least one (e.g. a set as defined herein can correspond to a unit, singlet, or single-element set, or a multiple-element set) , in accordance with known mathematical definitions.
  • the recitation of a particular numerical value or value range herein is understood to include or be a recitation of an approximate numerical value or value range.
  • the terms “first” , “second” , etc. are used merely as labels or identifiers and are not intended to impose numerical requirements on their associated terms.
  • an apparatus 20 for measuring a surface profile of an object 30 includes a light source assembly 100, a confocal microscopy assembly 200, and an optical detection assembly 300.
  • the apparatus 20 further includes a table for supporting the object 30 during the measurement.
  • the table may be configured to be displaceable, such as to shift the object 30 to measure different areas of, or the whole of, the surface profile.
  • the light source assembly 100 includes a broadband light source 110 configured for emitting broadband uniform light that spans across a broad continuous range of wavelengths.
  • the broadband uniform light is white light that includes wavelengths that span across the visible colour spectrum and may include wavelengths in the infrared and/or ultraviolet spectra.
  • the confocal microscopy assembly 200 includes a beam splitter 210 configured for directing uniform light from the broadband light source 110 to the object 30.
  • the beam splitter 210 is disposed between the broadband light source 110 and the object 30.
  • the confocal microscopy assembly 200 includes a pinhole device 220 having an array of pinholes 222, the pinhole device 220 configured for passing the uniform light from the beam splitter 210 through the pinholes 222 to the object 30. More specifically, the pinholes 222 are arranged to block out most of the light from the beam splitter 210 and to allow only some of the light to pass through to the object 30, each pinhole 222 acting as a point illumination source of a confocal microscope.
  • the pinholes 222 may be equal-distanced and circular or squarish.
  • the confocal microscopy assembly 200 includes a set of incident optical elements 230, such as lenses and/or mirrors, for directing the uniform light from the pinhole device 220 to the object 30 and causing chromatic aberration of the uniform light passing through the incident optical elements 230.
  • the pinhole device 220 is configured for passing light reflected from the object 30 through the pinholes 222 to the beam splitter 210, the reflected light including spectral information of the surface profile based on the chromatic aberration. More specifically, the pinholes 222 are arranged to allow only light that is focused on and reflected from the object 30 to pass through to the beam splitter 210. The pinhole device 220 blocks all reflected light that is not focused on the object 30 as such reflected light would not be incident on the pinholes 222.
  • the optical detection assembly 300 includes an optical detector 310 for receiving the reflected light from the beam splitter 220.
  • the optical detection assembly 300 includes a set of detection optical elements 320 for directing the reflected light from the beam splitter 210 to the optical detector 310.
  • the surface profile of the object 30 is measurable based on spectral information of the reflected light received by the optical detector 310, the spectral information representing heights across the surface profile.
  • the spectral information includes information about the wavelengths of the reflected light that is focused on the object 30 and reflected to the pinholes 222, wherein the wavelengths can be used to determine the height variation across the surface profile.
  • the method 400 includes a step 402 of directing uniform light from the broadband light source 110 to the object 30 using the beam splitter 210.
  • the method includes a step 404 of passing the uniform light from the beam splitter 210 through the array of pinholes 222 of the pinhole device 220 to the object 30.
  • the method includes a step 406 of directing the uniform light from the pinhole device 220 to the object 30 using the set of incident optical elements 230, the incident optical elements 230 causing chromatic aberration of the uniform light passing through the incident optical elements 230.
  • the method includes a step 408 of passing light reflected from the object 30 through the array of pinholes 222 to the beam splitter 210, the reflected light including spectral information of the surface profile based on the chromatic aberration.
  • the method includes a step 410 of directing the reflected light from the beam splitter 210 to the optical detector 310 using the set of detection optical elements 320.
  • the method includes a step 412 of receiving, by the optical detector 310, the reflected light from the beam splitter 210.
  • the method includes a step 414 of measuring the surface profile of the object 30 based on spectral information in the reflected light received by the optical detector 310, the spectral information representing heights across the surface profile.
  • the incident optical elements 230 cause chromatic aberration of the uniform light propagating from the pinhole device 220 to the object 30, and the reflected light from the object 30 includes spectral information based on the chromatic aberration, such as wavelengths. More specifically, the incident optical elements 230 cause axial or longitudinal chromatic aberration to the light, resulting in different wavelengths of the light focusing along different focal distances from the incident optical elements 230 to the object 30. Due to the chromatic aberration, the different wavelengths of the light focuses on different heights or depths across the surface profile of the object 30 relative to a reference plane along the surface profile.
  • red light having wavelengths such as around 620 to 720 nm
  • blue light having wavelengths such as around 460 to 500 nm
  • green light having wavelengths such as around 500 to 570 nm
  • the wavelengths that are clearly focused on the surface profile of the object 30 reflect from the object 30 to the pinhole device 220, the reflected light reversely following the same propagation paths as the incident light arriving and focused on the surface profile. These wavelengths of the reflected light that are focused on the object 30 are passed through the pinhole device 220 to the beam splitter 210. Other wavelengths of the reflected light that are not focused on the object 30 may be reflected back but they are not aligned with the pinholes 222 and cannot pass through the pinholes 222. In other words, the pinhole device 220 blocks out all reflected light that is not focused on the object 30. Hence, only certain wavelengths of the reflected light are reflected from the object 30 through the pinholes 222 to the beam splitter 210.
  • the reflected light is subsequently imaged on a conjugate plane of the pinhole device 210 and received by the optical detector 310.
  • these wavelengths are representative of the heights and the surface profile can be measured in three dimensions based on these wavelengths.
  • a colour spectral image of the surface profile can hence accurately measure the three-dimensional height contours across the surface profile without vertical scanning or movement of any component of the apparatus 20.
  • the pinhole device 220 may include suitable optical elements to minimize or prevent reflection of light. For example, light incident on the top surface of the pinhole device 220 may reflect back to the beam splitter 210 and merge with the reflected light from the object 30, potentially affecting accuracy of the surface profile measurement. These optical elements may also improve focusing of light into the pinholes 222 which would in turn improve the spectral imaging and measurement of the surface profile.
  • the pinhole device 220 may include one or more arrays of microlenses 224 arranged with the array of pinholes 222.
  • the pinhole device 220 includes a first array of microlenses 224 arranged on top of the pinholes 222, such that each pinhole 222 is associated with a microlens 224 of the first array configured for focusing light from the beam splitter 220 into the respective pinhole 222.
  • the pinhole device 220 may optionally include a second array of microlenses 224 arranged below the pinholes 222, such that each pinhole 222 is associated with a microlens 224 of the second array configured for focusing light reflected from the object 30 into the respective pinhole 222.
  • the pinholes 222 and microlenses 224 arrays may be formed separately and coupled together, or they may be integrated together as a single unit.
  • Each pinhole 222 is paired with at least one microlens 224 and they cooperate to focus light into the centre of the respective pinhole 222.
  • the microlenses 224 are specifically arranged with the pinholes 222 such that their centre focal points are aligned to focus light incident on the microlenses 224 into the pinholes 222. This collects more light energy on one or both sides of the pinhole device 220 and increases the amount of light directed into each pinhole 222, thereby improving the light efficiency because light efficiency is very low for conventional confocal microscopes.
  • the curved surfaces of the microlenses 224 can expel and remove unwanted light incident on them, thereby improving the quality of light passing through the pinholes 222.
  • the microlenses 224 are packed together such that they are in physical contact with each other or with some gap in between.
  • the diameter of the pinholes 222 is smaller than the diameter of the microlenses 224, there are gaps between the pinholes 222.
  • these gaps are represented as pitches P1 and P2 with respect to two perpendicular directions, i.e. along the X-axis and Y-axis, respectively.
  • pinholes 222 An advantage of the pinholes 222 is that the multiple points on the surface profile can be simultaneously measured for their heights.
  • the multiple points are distributed across at least a sample area, or in some cases substantially the whole, of the surface profile, enabling the apparatus 20 to perform quick sampling measurement of the sample area.
  • the number of points is dependent on the number of pinholes 222, so a larger number of pinholes 222 can increase the sample area being measured and/or increase the measurement resolution.
  • the high-speed sampling measurement of multiple points of the sample area can be useful for various practical applications, especially when quick inspection of a batch of objects 30 is required.
  • the confocal microscopy assembly 200 may include an actuation mechanism 240 for planarly moving the pinhole device 220.
  • the actuation mechanism 240 may be configured to planarly move the pinhole device 220 along the X-axis and/or Y-axis.
  • the actuation mechanism 240 may be configured to planarly rotate the pinhole device 220 around the Z-axis such that the pinhole device 220 remains on the XY-plane during the rotations.
  • the actuation mechanism 240 includes actuators such as motors and piezoelectric actuators.
  • the pinhole device 220 moves planarly along the XY-plane, the pinholes 222 and corresponding points on the surface profile are moved across the surface profile, enabling the light to reach and scan a continuous surface area and substantially the whole of the surface profile. Substantially all areas of the surface profile can be scanned and measured without any gaps (or at least minimized) , thereby mitigating risk of excluding relevant regions of interest of the surface profile. A more detailed measurement of the surface profile can hence be obtained, allowing for higher quality inspection of the object 30.
  • the apparatus 20 includes the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 as described above.
  • the light source assembly 100 includes the broadband light source 110 is configured for emitting broadband uniform light such as white light.
  • the broadband light source 110 includes a set of light lamps 112.
  • the light lamps 112 may be incandescent lamps or broadband white light emitting diodes (LEDs) .
  • the incandescent lamps are halogen lamps such as tungsten halogen lamps.
  • the light lamps 112 may be of low power, such as 50 W, to reduce waste heat generated from use of the apparatus 20. Low-powered light lamps 112 would obviate the need for cooling devices such as fans, which would in turn reduce mechanical vibrations and power consumption.
  • the light source assembly 100 may include a small heat sink to remove any heat generated from the broadband light source 110.
  • the broadband light source 110 includes an optical aperture 114 for directing the uniform light emitted from the light lamps 112 out of the broadband light source 110.
  • the optical aperture 114 may be circular and is configured to control the diameter of the light beam emitted out of the broadband light source 110 to the confocal microscopy assembly 200.
  • the broadband light source 110 may include an optical integrating sphere 116 configured to integrate the light energy from the light lamps 112.
  • the optical integrating sphere 116 also known as an Ulbricht sphere, is an optical component having a hollow spherical cavity with an internal reflective coating for uniform scattering of light and to reduce loss of light.
  • the light lamps 112 are arranged around the optical integrating sphere 116 such that light from the light lamps 112 is directed into the cavity towards the internal reflective coating of the optical integrating sphere 116, so that the internal reflective coating reflects the light to the optical aperture 114.
  • the broadband light source 110 may include an optical bandpass filter configured for filtering out light outside of a predefined wavelength range.
  • the optical bandpass filter is disposed between the light lamps 112 and the optical integrating sphere 116, such as at the optical aperture 114.
  • the optical bandpass filter includes a dichroic filter or dielectric mirror.
  • the predefined wavelength range may correspond to the visible colour spectrum, or a region thereof such as from red to blue, and the optical bandpass filter allows all visible light to pass through and exit the optical aperture 114.
  • Undesired light outside of the visible colour spectrum, such as infrared and ultraviolet light are blocked out by the optical bandpass filter.
  • infrared light is hotter than visible light and by blocking out infrared light, less heat is transmitted out of the optical aperture 114, thereby mitigating risk of heat damage to the confocal microscopy assembly 200.
  • the uniform light from the broadband light source 110 may propagate through the optical aperture 114 directly to the confocal microscopy assembly 200.
  • the light source assembly 100 may include a illumination device 120 having one or more lenses disposed between the broadband light source 110 and the confocal microscopy assembly 200.
  • the illumination device 120 provides parallel and uniform light to the confocal microscopy assembly 200.
  • the confocal microscopy assembly 200 includes the beam splitter 210, pinhole device 220, and set of incident optical elements 230 as described above.
  • the incident optical elements 230 include an objective lens 232 for focusing light on the object 30 and a tube lens 234 for focusing the reflected light from the object 30 on the pinhole device 220.
  • the incident optical elements 230 further include a chromatic aberration lens 236 disposed between the objective lens 232 and tube lens 234 for causing the chromatic aberration of the light.
  • the chromatic aberration lens 236 is designed with specific chromatic aberration properties and good linearity. Different chromatic aberration lens 236 may be used depending on the desired measurement range and resolution.
  • the chromatic aberration lens 236 may be integrated with the objective lens 232 as a single lens element. With chromatic aberration, the different wavelengths of the light are more clearly separated, and the different heights of the surface profile can be more clearly distinguished, so that the surface profile can be imaged and measured in 3D.
  • the optical detection assembly 300 includes the optical detector 310 and set of detection optical elements 320 as described above.
  • the detection optical elements 320 may include an imaging lens 322 for directing the reflected light from the beam splitter 210 to the optical detector 310.
  • the optical detector 310 may include a colour camera 312 having image sensors for the red-green-blue (RGB) colours, such as CCD or CMOS image sensors.
  • the imaging lens 322 is configured for focusing the reflected light containing the spectral information on the image sensors of the colour camera 312, thereby imaging on the colour camera 312 the spectral information in the reflected light from the surface profile of the object 30.
  • the working spectrum range of the colour camera 312 may span across the visible colour spectrum and optionally to the infrared and/or ultraviolet spectra.
  • the working wavelength range of the colour camera 312 may be around 380 to 1000 nm.
  • An infrared filter of the colour camera 312 may be added to exclude the infrared /near-infrared spectra.
  • different heights or depths across the surface profile are imaged as different colours according to the precise spectral information and wavelengths of the reflected light, and the captured spectral image of the surface profile can accurately measure the three-dimensional surface profile, wherein different heights across the surface profile are represented as different spectral colours in the spectral image.
  • Figure 7 shows an example of an RGB spectral image 40 including the calibrated RGB curves of the object 30 captured by the colour camera 312.
  • the apparatus 20 can be integrated or coupled with an image processing module to generate the surface topography of the object 30 based on the spectral image 40. More specifically, the image processing module calculates the surface profile of the object 30 based on spectral image 40 received by the optical detector 310, wherein the colours or wavelengths of each point (corresponding to the pinholes 222) represent the height of that point on the surface profile. All the points collectively represent the height variation across the whole surface profile.
  • the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 are arranged as shown in Figure 1.
  • uniform light from the light source assembly 100 passes through the beam splitter 210 to the object 30, reflects from the object 30 back to the beam splitter 210, and the beam splitter 210 reflects the light to the optical detection assembly 300.
  • the beam splitter 210 is configured for both transmission and reflection (preferably in equal ratios) , there may be other configurations of the apparatus 20.
  • light from the light source assembly 100 reaches the beam splitter 210, reflects to the object 30, reflects from the object 30 back to the beam splitter 210, and passes through the beam splitter 210 to the optical detection assembly 300.
  • the apparatus 20 includes the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 configured for measuring the surface profile of the object 30.
  • the light source assembly 100 includes the broadband light source 110 and the illumination device 120.
  • the confocal microscopy assembly 200 includes the beam splitter 210 and the pinhole device 220 having the array of pinholes 222 and one or more arrays of microlenses 224 arranged with the array of pinholes 222.
  • the confocal microscopy assembly 200 further includes the set of incident optical elements 230 and the actuation mechanism 240 for planarly moving the pinhole device 220 along the X-axis and Y-axis.
  • the incident optical elements 230 include the objective lens 232, tube lens 234, and chromatic aberration lens 236.
  • the optical detection assembly 300 includes the optical detector 310 having the colour camera 312, and further includes the set of detection optical elements 320 having the imaging lens 322 for focusing the reflected light on the colour camera 312.
  • the apparatus 20 is substantially similar to the embodiment as shown in Figure 1 except for the optical detection assembly 300. It will be appreciated that various aspects described above for the embodiment of Figure 1 will apply similarly or analogously to the embodiment of Figure 9, and vice versa.
  • the optical detector 310 includes a hyperspectral camera 314 and the optical detection assembly 300 may be referred to as a one-shot hyperspectral imaging assembly 302.
  • the hyperspectral camera 314 may capture the spectral information in the reflected light more precisely and obtain the hyperspectral information of the surface profile.
  • the hyperspectral camera 314 is a one shot or single shot hyperspectral camera that captures only one image to obtain the hyperspectral information of the surface profile.
  • the hyperspectral camera 314 can capture the hyperspectral information in full colour or in monochrome.
  • the hyperspectral camera 314 is a high-resolution full colour or monochrome camera.
  • Normal spectral imaging or multispectral imaging captures and processes images usually in three broad bands of wavelengths corresponding to the RGB colours because the human eye sees colours of visible light in mostly these three bands.
  • Hyperspectral imaging can capture and process images across the electromagnetic spectrum ranging from infrared to ultraviolet spectra or even including the X-ray spectrum.
  • Hyperspectral imaging divides the electromagnetic spectrum into many more bands compared to the usual three RGB bands and covering a wide range of wavelengths with fine wavelength resolution.
  • Hyperspectral imaging measures a multitude of continuous spectral bands, as opposed to normal spectral imaging which measures spaced broad RGB spectral bands.
  • the hyperspectral camera 314 can capture and process images of the object 30 at a very large number of fine wavelengths and the hyperspectral information can be broken down into a very large number of colours corresponding to the fine wavelengths.
  • the one-shot hyperspectral imaging assembly 302 includes an aperture device 330 for passing through the reflected light from beam splitter 210 to the hyperspectral camera 314.
  • the aperture device 330 includes at least one aperture or hole for the light to pass through.
  • the one-shot hyperspectral imaging assembly 302 includes a wavelength differentiation device 340 disposed between the aperture device 330 and the hyperspectral camera 314 for differentiating the reflected light to more clearly distinguish the reflected light by the spectral information i.e. the wavelengths.
  • the wavelength differentiation device 340 may be either an optical grating for diffracting the reflected light or an optical prism for dispersing the reflected light.
  • the set of detection optical elements 320 includes the imaging lens 322 disposed in front of the hyperspectral camera 314 and behind the optical grating 340.
  • the imaging lens 322 is configured for focusing the reflected light from the optical grating 340 on the image sensors of the hyperspectral camera 314, thereby imaging on the hyperspectral camera 314 the spectral information in the reflected light from the surface profile of the object 30.
  • the detection optical elements 320 further include a collimator 324 disposed between the aperture device 330 and the optical grating 340.
  • the collimator 324 is a device, such as a curved lens or mirror, that narrows a light beam and align it to a specific direction.
  • the detection optical elements 320 may further include a relay lens 326 disposed between the beam splitter 210 and the aperture device 330.
  • the relay lens 326 is configured for projecting, on the aperture device 330 via the beam splitter 210, the image of the surface profile formed on the pinhole device 220.
  • the imaging lens 322 projects the refracted wavelengths of the reflected light on the hyperspectral camera 314 as discrete wavelengths according to the spectral information in the reflected light. Due to effects of the microlenses 224 which increase the amount of light directed into the pinholes 222, the image sensitivity is increased and the full spectrum of each point on the surface profile of the object 30 is imaged by the hyperspectral camera 314.
  • Figure 10 shows an example of a hyperspectral image 50 of the object 30 captured using the one-shot hyperspectral imaging assembly 302.
  • the apparatus 20 can be integrated or coupled with an image processing module to generate the surface topography of the object 30 based on the hyperspectral image 50.
  • the subsurface topography and multi-layer thicknesses on the surface of the object 30 can be precisely measured and inspected because of the full hyperspectral spectrum of the 3D surface profile.
  • Hyperspectral imaging can hence measure the full spectrum of the surface profile in high resolution and detail, and the apparatus 20 has broad applications in various fields such as but not limited to online inspection and measurements for semiconductor, electronics, precision engineering, optics, biomedical agriculture, and food industries.
  • the aperture device 330 includes an array of pinholes 332 similar to the pinholes 222 of the pinhole device 220.
  • the aperture device 330 may further include an array of microlenses 334 arranged with the array of pinholes 332, similar to the microlenses 224 of the pinhole device 220.
  • the aperture device 330 includes the array of microlenses 334 arranged in front of the pinholes 332, i.e. between the beam splitter 210 and the pinholes 332, such that each pinhole 332 is associated with a microlens 334 of the array.
  • the pinholes 332 and microlenses 334 arrays may be formed separately and coupled together, or they may be integrated together as a single unit. Each pinhole 332 is paired with one microlens 334 and they cooperate to focus light into the centre of the respective pinhole 332.
  • the apparatus 20 includes the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 being a one-shot hyperspectral imaging assembly 302 configured for measuring the surface profile and subsurface profile including multi-layer film thickness of the object 30.
  • the light source assembly 100 includes the broadband light source 110 and the illumination device 120.
  • the confocal microscopy assembly 200 includes the beam splitter 210 and the pinhole device 220 having the array of pinholes 222 and one or more arrays of microlenses 224 arranged with the array of pinholes 222.
  • the confocal microscopy assembly 200 further includes the set of incident optical elements 230 and the actuation mechanism 240 for planarly moving the pinhole device 220 along the X-axis and Y-axis.
  • the apparatus 20 may exclude or stop the actuation mechanism 240 to perform quick sampling measurement of the object 30.
  • the incident optical elements 230 include the objective lens 232, tube lens 234, and chromatic aberration lens 236.
  • the one-shot hyperspectral imaging assembly 302 includes the optical detector 310 having the hyperspectral camera 314, the aperture device 330 including an array of pinholes 332 and an array of microlenses 334 arranged with the array of pinholes 332, and the wavelength differentiation device 340.
  • the one-shot hyperspectral imaging assembly 302 further includes the set of detection optical elements 320 having the relay lens 326, collimator 324, and imaging lens 322.
  • the apparatus 20 is configured to scan 2D areas of the surface profile of the object 30. Specifically, the array of pinholes 222 of the pinhole device 220 are arranged across a 2D plane. In one embodiment as shown in Figure 11, the apparatus 20 is configured to perform line scanning of the surface profile of the object 30. It will be appreciated that various aspects described above for the embodiments of Figures 1 and 9 will apply similarly or analogously to the embodiment of Figure 11, and vice versa. In the embodiment of Figure 11, instead of a 2D array of pinholes 222, the pinholes 222 and likewise the microlenses 224 are arranged in a single row (1D line) .
  • the pinholes 332 and likewise the microlenses 334 are arranged in a single row (1D line) .
  • the single row of pinholes 332 may be replaced by a 1D slit aperture 336 as shown in Figure 11.
  • the optical aperture 114 of the broadband light source 110 is a line aperture to correspond to the single rows of pinholes 222 /332.
  • the illumination device 120 is also replaced by a cylindrical lens 122 which focuses the broadband light beam to a line light.
  • the actuation mechanism 240 for planarly moving the pinhole device 220 may be configured to move the pinhole device 220 in a direction parallel to the single row of pinholes 222 to cover gaps or pitches between the pinholes 222.
  • the row of pinholes 222 extends along the X-axis across the surface profile and the actuation mechanism 240 is configured to move the pinhole device 220 along the X-axis.
  • the actuation mechanism 240 is cooperative with the displaceable table supporting the object 30 to measure the whole surface profile of the object 30. For example, the actuation mechanism 240 moves the pinholes 222 along the X-axis while the table moves the object 30 along the Y-axis.
  • the optical detector 310 (such as the colour camera 312 or hyperspectral camera 314) captures a row of spectrum at a time as the line light moves across the surface profile.
  • Figure 12 an example of a hyperspectral image 60 of the object 30 captured by the hyperspectral camera 314 in successive rows of spectrum.
  • the apparatus 20 is configured for line scanning the object 30 and includes the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 being the one-shot hyperspectral imaging assembly 302.
  • the light source assembly 100 includes the broadband light source 110 and the cylindrical lens 122 for focusing the uniform light from the broadband light source 110 into a line light for line scanning the object 30.
  • the confocal microscopy assembly 200 includes the beam splitter 210 and the pinhole device 220 having the array of pinholes 222 in a single row for the line scanning and one or more arrays of microlenses 234 arranged with the row of pinholes 222.
  • the confocal microscopy assembly 200 further includes the set of incident optical elements 230 and the actuation mechanism 240 for planarly moving the pinhole device 220 parallel to the row of pinholes 222, e.g. along the X-axis.
  • the incident optical elements 230 include the objective lens 232, tube lens 234, and chromatic aberration lens 236.
  • the one-shot hyperspectral imaging assembly 302 includes the optical detector 310 having the hyperspectral camera 314, the aperture device 330 having the slit aperture 336 for the line scanning, and the wavelength differentiation device 340.
  • the aperture device 330 includes a single row of pinholes 332 for the line scanning and a single row of microlenses 334 arranged with the row of pinholes 332.
  • the one-shot hyperspectral imaging assembly 302 further includes the set of detection optical elements 320 having the relay lens 326, collimator 324, and imaging lens 322.
  • the apparatus 20 is substantially similar to the embodiment as shown in Figure 9 except for the pinhole device 220.
  • the pinhole device 220 is in the form of a Nipkow disk 226.
  • the Nipkow disk 226 is a scanning disk having the pinholes 222 which may be equal-distanced and circular or squarish.
  • the actuation mechanism 240 is configured to planarly rotate the Nipkow disk 226 around the Z-axis.
  • the pinholes 222 are positioned to form a single-turn spiral starting from an external radial point of the Nipkow disk 226 and towards the centre, such that the pinholes 222 trace circular ring patterns when the actuation mechanism 240 rotates the Nipkow disk 226.
  • the pinholes 222 and corresponding points on the surface profile of the object 30 are moved across it, enabling a continuous surface area of the surface profile to be scanned and measured.
  • the Nipkow disk 226 further includes a first array of microlenses 224 arranged on top of the pinholes 222. As shown in Figure 15, the Nipkow disk 226 may further include a second array of microlenses 224 arranged below the pinholes 222, i.e. the array of pinholes 222 is sandwiched between the first and second arrays of microlenses 224. Each pinhole 222 is associated with at least one microlens 224 configured for focusing light into the respective pinhole 222.
  • the apparatus 20 includes the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 being the one-shot hyperspectral imaging assembly 302.
  • the light source assembly 100 includes the broadband light source 110 and the illumination device 120.
  • the confocal microscopy assembly 200 includes the beam splitter 210 and the pinhole device 220 in the form of the Nipkow disk 226 having the array of pinholes 222.
  • the Nipkow disk 226 may further include one or more arrays of microlenses 224 arranged with the array of pinholes 222.
  • the confocal microscopy assembly 200 further includes the set of incident optical elements 230 and the actuation mechanism 240 for rotating the pinhole device 220 along the Z-axis.
  • the incident optical elements 230 include the objective lens 232, tube lens 234, and chromatic aberration lens 236.
  • the one-shot hyperspectral imaging assembly 302 includes the optical detector 310 having the hyperspectral camera 314, the aperture device 330 having an array of pinholes 332 and an array of microlenses 334 arranged with the array of pinholes 332, and the wavelength differentiation device 340.
  • the one-shot hyperspectral imaging assembly 302 further includes the set of detection optical elements 320 having the relay lens 326, collimator 324, and imaging lens 322.
  • the apparatus 20 includes the light source assembly 100, confocal microscopy assembly 200, and optical detection assembly 300 as described above.
  • the light source assembly 100 includes the broadband light source 110 and illumination device 120.
  • the optical detection assembly 300 includes the colour camera 312 and the imaging lens 322, although it will be appreciated that the optical detection assembly 300 can be the one-shot hyperspectral imaging assembly 302.
  • the confocal microscopy assembly 200 includes the beam splitter 210, the pinhole device 220 in the form of the Nipkow disk 226, and the actuation mechanism 240 for rotating the Nipkow disk 226.
  • the confocal microscopy assembly 200 further includes the tube lens 234, chromatic aberration lens 236, and objective lens 232 cooperative for chromatically aberrating and focusing light on the object 30.
  • the object 30 is supported on a table 32 that is configured to be displaceable.
  • the table 32 is coupled to or integrated with actuators, such as motors and piezoelectric actuators, that can displace the table 32 along and/or rotate the table 32 around at least one of the XYZ-axes.
  • the incident optical elements 230 include a first objective lens 232 and a second objective lens 238.
  • the confocal microscopy assembly 200 further includes switching device or turret 250 for supporting the first and second objective lenses 232, 238.
  • the switching device 250 may include actuators, such as motors and piezoelectric actuators, and can be operated to switch between the objective lenses 232, 238.
  • the first objective lens 232 has higher magnification power while the second objective lens 238 has lower magnification power.
  • the incident optical elements 230 may include multiple objective lenses switchable between each other using the turret 250, wherein the objective lenses may be of varying magnification powers so that measurement performance can be selected accordingly.
  • the 3D surface profile measurement apparatus 20 can mainly be used for online high speed measurements and inspection, it can also be used as a standalone measurement system for sampling measurements.
  • the Figure 16 shows a standalone example of the measurement apparatus 20.
  • the apparatus 20 includes the broadband light source 110, illumination device 120, and the beam splitter 210, which directs the uniform illumination light to the surface of the Nipkow disk 226. Some of the light is blocked by the Nipkow disk 226 and some of the light passes through the pinholes 222 of the Nipkow disk 226. The light from the pinholes 222 passes through tube lens 234, chromatic aberration lens 236 and finally is focused by the objective lens 232 on the surface of the object 30 mounted on the mechanical displaceable table 32.
  • An observation device 500 is inserted between the objective lens 232 and tube lens 234 for observation and selecting of the area of the surface profile for inspection.
  • the observation device 500 includes a first beam splitter 510, a second beam splitter 520, an ocular lens or eyepiece 530, an imaging lens 540, and a camera 550.
  • the surface profile of the object 30 is imaged by the objective lens 232 and reflected by the first beam splitter 510 and second beam splitter 520.
  • the image can be imaged by the imaging lens 540 and camera 550.
  • the image of the object 30 is also can be observed directly through the eyepiece 530 by the naked eye.
  • the observation device 500 can moved in for observation and moved out for the 3D surface profile measurements.
  • the apparatus 20 and method 400 can measure the surface profile of the object 30 by capturing a single image of the surface profile and using spectral analysis to generate the surface topography of the object 30.
  • the light source assembly 100 provides uniform broadband light to the confocal microscopy assembly 200 and optical detection assembly 300 to image the object 30.
  • the confocal microscopy assembly 200 generates and collects spectral information of the surface profile, and the optical detection assembly 300 records the spectral information on a spectral image of the surface profile.
  • the apparatus 20 can be integrated or coupled with an image processing module to generate the surface topography of the object 30 based on the spectral image, such as the spectral image 40 or hyperspectral image 50 mentioned above. For example, with the hyperspectral image 50, subsurface topography and surface layer thicknesses of the object 30 can be inspected in addition to the surface topography.
  • the spectral analysis is based on the principle of chromatic aberration of the broadband uniform light as it passes through the confocal microscopy assembly 200.
  • the chromatic aberration of the uniform light creates spectral information with more distinct wavelengths that are representative of the heights across the surface profile, and the surface profile can be measured accurately based on these wavelengths without vertical scanning.
  • the apparatus 20 can achieve high-speed surface profile measurements because of the pinhole device 220, such as the Nipkow disk 226.
  • the whole surface profile can be scanned and measured without any gaps, thereby mitigating risk of excluding relevant regions of interest and allowing for higher quality inspection of the object 30.
  • the apparatus 20 and method 400 can be used for high-speed and accurate measurement of the surface profile, especially if the surface profile is undulating or discontinuous. This would be suitable in various applications, including for high-speed automatic surface topography inspection of semiconductor wafers, integrated circuit wire loops, and precision components.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Microscoopes, Condenser (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

L'invention concerne un appareil (20) pour mesurer un profil de surface d'un objet (30), l'appareil (20) comprenant : un ensemble source de lumière (100) composé d'une source de lumière à large bande (110) ; un ensemble microscopie confocale (200) comprenant : un séparateur de faisceau (210) pour diriger une lumière uniforme de la source de lumière à large bande (110) vers l'objet (30) ; un dispositif à sténopé (220) comprenant un réseau de sténopés (222) et un réseau de microlentilles (224), le dispositif à sténopé (220) étant configuré pour faire passer la lumière uniforme du séparateur de faisceau (210) vers l'objet (30) ; un ensemble d'éléments optiques incidents (230) pour diriger la lumière uniforme du dispositif à sténopé (220) vers l'objet (30) et provoquer une aberration chromatique de la lumière uniforme traversant les éléments optiques incidents (230) ; et le dispositif à sténopé (220) configuré pour faire passer la lumière réfléchie par l'objet (30) vers le séparateur de faisceau (210) ; et un ensemble de détection optique (300) comprenant : un détecteur optique (310) ; et un ensemble d'éléments optiques de détection (320), le profil de surface de l'objet (30) étant mesurable sur la base d'informations spectrales de la lumière réfléchie reçue par le détecteur optique (310), les informations spectrales représentant des hauteurs en travers du profil de surface.
PCT/CN2021/083092 2020-04-02 2021-03-25 Appareil de mesure de profil de surface WO2021197207A1 (fr)

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TWI797787B (zh) * 2021-10-21 2023-04-01 炳碩生醫股份有限公司 用於控制拉曼光譜儀的裝置

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