WO2017045982A1 - Dispositif et procédé pour l'analyse confocale chromatique d'un échantillon - Google Patents

Dispositif et procédé pour l'analyse confocale chromatique d'un échantillon Download PDF

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Publication number
WO2017045982A1
WO2017045982A1 PCT/EP2016/071056 EP2016071056W WO2017045982A1 WO 2017045982 A1 WO2017045982 A1 WO 2017045982A1 EP 2016071056 W EP2016071056 W EP 2016071056W WO 2017045982 A1 WO2017045982 A1 WO 2017045982A1
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Prior art keywords
light
sample
reflected
beam splitter
light source
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PCT/EP2016/071056
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German (de)
English (en)
Inventor
Anton Tremmel
Markus Stefan Rauscher
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Technische Universität München
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Publication of WO2017045982A1 publication Critical patent/WO2017045982A1/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
    • G01B11/02—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
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/04—Measuring microscopes
    • 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
    • G02B21/0032—Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers
    • 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
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/02—Objectives
    • G02B21/04—Objectives involving mirrors
    • 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

Definitions

  • the application relates to a device and method for chromatic-confocal examination of a sample.
  • Optically thin films are now used in many applications and fulfill a broad spectrum of functionality. Possible applications include, for example, antireflection coating in the manufacture of glasses, electrical conductivity in the semiconductor industry or isolation in biochemistry.
  • a very promising new application of thin-film technologies is currently opening up in the field of polymer electronics.
  • a variety of new products are being developed, as besides the aspect of extremely economical production by means of print processes, further advantages such as flexible carrier materials are possible.
  • very cheap new innovative products such.
  • B. printed circuits or display products are produced under this area also fall Produlcte as organic solar cells, which have enormous potential z.
  • the layer thickness of the individual layers is decisive.
  • the thickness ie the geometry of the applied layer, determines, for example, the conductivity or reactivity of the applied chemical layer. If the geometry of this layer is incorrect, components will show a defect or behavior that is not useful for proper operation. That's why monitoring the print process is essential. Process monitoring must be non-invasive, so visual inspection is the first choice.
  • a constant homogeneous layer thickness on the measurement object is decisive for a functional end product. It is not sufficient to perform only discrete point measurements, as undetected defects can lead to failure of the product. Therefore, it is desirable to have a technology which instead of discrete measuring points can determine entire measuring surfaces on their layer thickness behavior.
  • a widely used method is x-ray reflectometry (x-ray reflectometry, XRR), in which the reflectivity of x-ray radiation makes it possible to make statements about the layer thickness.
  • XRR x-ray reflectometry
  • layer thicknesses from 2 nm to 1000 nm can be determined with a resolution of less than one nanometer.
  • the long measurement duration of more than 10 s also has a disadvantageous effect. Since the X-rays are only allowed to strike the test object at an angle of a few degrees, a large influence of the measuring distance on the layer thickness measurement and a low lateral resolution are the result. Due to the low lateral resolution, fine structures on the measuring surface can not be distinguished.
  • X-ray-based measurement method is x-ray fluorescence spectroscopy (XRF).
  • XRF x-ray fluorescence spectroscopy
  • Measurable layer thicknesses are in the range of 2 nm to 10 ⁇ m.
  • an ultraviolet light source can also be used for excitation.
  • the problem with this method is that the layers may need to be provided with markers and the measurement of multi-layer systems is complex. For calibration, a reference measurement object is also required.
  • SE spectral ellipsometry
  • TFR thin-film reflectometry
  • the coated surface of the test object is irradiated with polychromatic light and a reflectance spectrum is measured. Due to thin-layer interference in the layer system of the measurement object, the reflection spectrum exhibits extremes whose periodicity allows conclusions to be drawn about the layer thickness. The advantages of this process are above all the robust construction and the short measuring time. Depending on the spectral bandwidth and evaluation method of the measured data, the minimum measurable layer thickness is limited to approximately 30 nm.
  • a widely used method of surface metrology is laser triangulation.
  • the measurement object is illuminated with a laser line which is observed by a camera at a known triangulation angle. Structures on the measurement object deform the line from the perspective of the camera, from which the surface profile can be calculated.
  • the advantages of the method are the great robustness against environmental influences and the simple scalability of the lateral measuring range.
  • the measuring surfaces are too rough or heavily reflective, the result of the measurement will be increasingly distorted.
  • Common devices offer a resolution of a few micrometers, depending on the size of the measuring range.
  • Speckle interferometry exploits the formation of speckles when irradiating a rough surface with coherent light to determine the topography.
  • the specimen pattern is due to interference of the reflected radiation at the structured surface. Due to the interferometric measuring principle, high resolution, short measuring times and a long working distance are possible.
  • a disadvantage for use in an industrial environment is the high sensitivity to shocks.
  • WLT White light interferometry
  • OCT optical coherence tomography
  • Another measuring device for distance determination is the autofocus microscope. The sample is thereby moved stepwise perpendicular to the focal plane of a microscope. At each step, a picture is taken by a camera. The surface topography is then calculated from the sharpness information of the images.
  • the size of the lateral measuring range is determined by the magnification of the microscope and the size of the camera sensor.
  • the achievable distance resolution of common devices is about 20 nm.
  • a confocal proximity sensor is similar to that of the autofocus microscope.
  • a point light source is imaged by a lens on the surface of the measurement object, reflected from there and then focused on a pinhole, behind which a photodiode is mounted.
  • the light intensity at the photodiode is maximum when the measurement object is in the focal plane of the objective.
  • the gradual shifting of the objective for distance measurement is omitted if the dispersion of the optics is utilized and a spectrometer is used instead of the photodiode (chromatic-confocal sensor).
  • the system can either be moved translationally or with a Nipkow Slice, a mirror scanner or be expanded with slit.
  • the advantages of the confocal technique are above all the simple optical design and the short measuring time.
  • the document US 8,654,352 Bl discloses a chromatic-confocal line scanner with a multispectral point light source and a collimator for generating a parallel beam.
  • the collimated light beam is focused via a beam splitter and a hyperchromatic cylindrical lens on an object to be measured.
  • a slot-shaped detection diaphragm, a downstream spectrometer and an image acquisition unit are provided.
  • the document US 2010/0188742 Al describes another chromatic-confocal line scanner with a multispectral point light source.
  • a beam forming into a line already takes place during the collimation via a cylindrical lens, which is arranged directly behind the fiber end.
  • a fan-shaped light measurement line is generated.
  • a multispectral line is projected onto the object and evaluated confocally.
  • the document US 2010/0097693 A1 discloses another embodiment of a chromatic-confocal line scanner.
  • a multispectral line is formed by a slit in front of the multispectral point light source.
  • a slit diaphragm is imaged onto the object.
  • a chromatic aberration is already introduced into the system during the beam shaping in order to generate a parallel beam through a lens.
  • the task is to specify improved technologies for examining a sample, in particular for the optical examination of a sample.
  • the device has a multispectral light source which is arranged in a focal point of a concave mirror. Light emitted by the light source is at least partially reflected by the concave mirror as parallel light rays.
  • the device still has a steel divider arranged in the beam path of the light beams and configured to at least partially direct the light beams to a sample and to transmit light reflected from the sample to a detector means.
  • a first focusing device is provided, which is arranged between the steel divider and the sample and which is configured to focus the light emerging from the beam splitter into a line, so that a first focus light line is generated.
  • the device comprises a second focusing device, which is arranged between the beam splitter and the Detelrtor planted and which is configured to focus the light reflected from the sample to a line, so that a second focus light line is generated, a slit is between the second Focusing rectification and the detector device arranged.
  • the detector device is configured to spectrally evaluate light reflected from the sample.
  • a method comprising the steps of: providing reference data, the reference data including reflectance curves of a material of the sample at different layer thicknesses and a chromatic reference characteristic, comparing a reflectance curve reflected from the sample and detected by a detector means Reference data and determining a layer thickness of the sample and a distance of the sample from the detector device based on the comparison.
  • the method can be carried out, for example, with the device disclosed in the application.
  • a thin layer can be used as a sample, the surface of which is illuminated in order to determine properties of the layer (thin-layer measurement).
  • the sample may comprise one or more materials.
  • the sample may be provided as a layer of a single material.
  • the sample may be provided as a multilayer system with various materials arranged in layers.
  • the sample may contain organic and / or inorganic materials.
  • the sample can be produced, for example, by means of a printing process.
  • the thickness of the sample can be between 30 nm and 3.5 ⁇ .
  • the concave mirror can be designed as a parabolic mirror, for example as an off-axis parabolic mirror.
  • a spherical concave mirror may be provided.
  • the light source may be approximately a point light source. The closer the light source comes to the ideal of the point light source, the better the resolution of the device.
  • the light source may be provided by means of an optical fiber, wherein in one end of the optical fiber light is emitted, which emerges at another end of the optical fiber, and wherein the other end of the optical fiber is arranged in the focal point of the concave mirror.
  • the other end of the optical fiber may also be referred to as an open end.
  • the optical fiber may be a glass fiber.
  • the glass fiber may have a core diameter of at least 50 ⁇ .
  • the core diameter may alternatively be at least 200 ⁇ . It can also glass fibers with a core diameter of less than 50 ⁇ be used, for example, 30 ⁇ , 20 ⁇ or 10 ⁇ . A smaller core diameter can lead to better local resolution.
  • the optical fiber may be designed as a single mode fiber, for example with a core diameter of 9 ⁇ m.
  • the fiber may be implemented as a step index multimode fiber or as a graded index multimode fiber.
  • the use of an optical fiber increases the flexibility of the device. Light from a luminaire can be fed into the device by means of the optical fiber, wherein the arrangement of the luminaire can take place outside the device. As a light, for example, an LED (light emitting diode) can be used.
  • the light source may be provided as a single LED, as a plurality of individual LEDs, or as an LED array. For example, a white light LED can be used. By combining different colored LEDs, for example in an array, a specific spectral distribution of the light source can be set.
  • the light source may be configured to emit light in one of the following spectral ranges: UV (ultraviolet), VIS (visible light), NIR (near infrared), IR (infrared), and a combination thereof.
  • the detector device can be configured to receive and evaluate light in the abovementioned spectral ranges. In particular, the spectral range of the light source can be adapted to the spectral range of the detector device.
  • the light source may be provided as a pulsed light source.
  • a light source controller configured to generate light pulses having a particular pulse length may be provided. When using an LED (individually, several LEDs or in an LED array), a minimum pulse duration of 500 ⁇ can be achieved. With a pulsable broadband light source with sufficiently high power, exposure times in the nanosecond range are also possible.
  • a pulse generating device may be provided, for example an optical shutter (eg a Pockels cell). The pulse generator may be configured to generate pulses having a length of 40 or shorter.
  • the components of the device may be arranged and / or configured such that light rays are incident solely perpendicular to the sample.
  • the device additionally comprises the following components: a first shielding device arranged in a loss path emerging from the beam splitter, the loss path comprising light emitted by the light source and passing through the beam splitter, without being directed in the direction of Sample is deflected, wherein the first shielding means is disposed in the loss path such that a part of the light in the loss path hits the first shielding means and another part of the light in the loss path passes the first shielding means, a mirror behind the first one Shielding device is arranged so that the mirror reflects the past the first shielding light, such that the reflected light to the beam splitter back and is deflected by the beam splitter as a reference light to the detector means, and a second shielding device, the un between the beam splitter d of the first focusing means is arranged in a light path toward the sample such that light having a width corresponding to a width of the light passing the first shield means and reflected by the mirror in the leakage path is shielded in the light path to the sample
  • An attenuation device for attenuating the light may be arranged in the beam path of the reference light, for example in front of the mirror.
  • the light output at the Detel gate device can be controlled (dynamic adaptation). With different measuring objects different amounts of light can be reflected. A worse reflection can be compensated by a higher light output of the light source. However, then the range of the reference path at the detector device can saturate. By means of the dampening device, the reference light can be attenuated in order to avoid saturation.
  • the Abdämpf worn can be designed as a filter. For example, a magazine with different (two or more) grayscale filters may be placed directly in front of the mirror of the reference path to reduce the amount of light in the path.
  • the Detel tor worn can be designed as Hyperspectral detector (Hyperspectral Imager - HSI).
  • HSI have the property of breaking up coupled light into spectral components. Usually, transmissive or reflective optical gratings are used for this purpose.
  • an HSI can not only spectrally resolve a spot, but also a line. Depending on the attached surface camera, it is scanned laterally. Instead of a one-dimensional measurement, an HSI allows a two-dimensional representation.
  • the imaging properties of the gratings used have the consequence that not so high resolutions are achieved in the spectral resolution.
  • the device may have an HSI with reflel tive Konkavgitterianan, for example, a device from the company Headwall, Model Series A.
  • the spectral resolution is given with 2-3 nm at a 25 ⁇ entrance gap.
  • the resolution is high enough to allow layer thickness measurement.
  • the detector device can have a plurality of detector units which have different spectral pickup ranges and / or spectral resolutions. As a result, the measuring range and / or the measurement resolution can be adjusted.
  • the first focusing means may be formed as a cylindrical lens having a chromatic aberration, wherein a change in the focal length of the light is linearly dependent on the wavelength of the light. It is also possible to use a cylindrical lens with a nonlinear characteristic as the first focusing device.
  • the first focusing device may be a cylindrical lens with a non-linear monotone characteristic.
  • the second focusing device can be designed as a cylindrical lens or as a parabolic trough mirror.
  • the first focusing means and / or the second focusing means may comprise an array of a plurality of cylindrical lenses (e.g., a lens).
  • the plurality of cylindrical lenses may be combined such that a linear characteristic of the first focusing device and / or the second focusing device is achieved.
  • the method may further comprise: detecting a reference light of a light source and correcting the reflectance curve in consideration of the reference light.
  • the device allows a line scan of the sample.
  • the device and the sample can be moved relative to one another, for example with a drive device coupled to the device and / or the sample. This allows the determination of a surface.
  • the detector device can be coupled to an evaluation device.
  • the evaluation device can be integrated into the detector device or be formed separately therefrom.
  • the evaluation device can be executed as a data processing device.
  • the evaluation device can have, for example, one or more processors as well as a memory with a volatile (eg main memory) and / or a non-volatile (eg a hard disk and / or a flash memory) memory area.
  • the evaluation device can have communication devices for receiving and / or transmitting data and / or data streams, for example a network connection (LAN), a connection for a wireless network (WLAN), a mobile radio module (eg 2G, 3G and / or 4G), a USB port (USB - universal serial bus), a Bluetooth adapter and / or a Firewire port (IEEE 1394).
  • the evaluation device can have a device for detecting a user input, for example a keyboard, a mouse and / or a touchpad.
  • the evaluation device can be connected to a display device.
  • a display device can be integrated in the evaluation device.
  • the display device may include a touch-sensitive screen for detecting user input.
  • the evaluation device may be configured to execute the method disclosed in the application.
  • the evaluation device can be, for example, a personal computer or a tablet.
  • the device and the method can enable a layer thickness determination on measuring surfaces of a sample. This is done, for example, by means of a hyperspectral imager, which can be used as a detector device.
  • the device may generate a measurement line that is orthogonal to the sample, for example.
  • the reflections of the light from the sample can in turn be formed into a line and focused on the slit (entrance slit) of the hyperspectral imager.
  • the functionality of a hyperspectral imager allows a spectrum to be obtained for each laterally resolvable position, which enables a calculation of the layer thickness.
  • the device makes it possible, for example, to implement the reflectometric measurement principle on hyperspectral images. If the hyper- spectral image or the sample linearly uniform in one direction, such. B. in continuous web printing, the full-surface measurement of layers can be guaranteed.
  • FIG. 3 shows a schematic representation of a further embodiment of the device
  • FIG. 4 shows a construction drawing of an embodiment of the device
  • Fig. 1 shows a schematic representation of an embodiment of the device, on the left side of Fig. 1, the device with the measuring concept is shown along the measuring line (longitudinal measuring range 9) and on the right side of Fig. 1, the device with the measuring concept shown transverse to the measuring line (lateral measuring range 10).
  • the starting point is a punctiform light source 5.
  • the property of the point fidelity is of great importance for the achievable lateral resolving power of the device.
  • the (approximate) polarity of the light source is generated using a multimode fiber.
  • An open end of a multimode fiber models a punctiform light source 5, with the additional advantage that the feeding of light into the measuring system can be done flexibly.
  • the punctiform light source 5 is collimated by means of an off-axis parabolic mirror 7 without chromatic aberration and fed through a 50/50 beam splitter 4 in a measuring path.
  • a rectangular aperture 6 is arranged in front of the beam splitter 4 .
  • Cylindrical lenses 8a, 8b focus the parallelized steel to a flat focal line orthogonal to the measuring object 11.
  • the incident light reflects at the various interfaces of the thin layers on the measuring object 11.
  • the reflected components interfere with each other according to the law of multi-beam interference and thus produce a characteristic spectral course.
  • the reflected components are in turn fed back into the measurement path.
  • the reflected radiation passes through the beam splitter 4 again and is imaged by another cylindrical lens 3 to a line.
  • This line is focused on an input slit 2 of a hyperspectral imager (HSI) 1, which is configured to split the line both laterally and spectrally.
  • the resolution of the HSI 1 determines how finely the measurement line can be subdivided. That is, with increasing resolution of the imager 1, the lateral resolution of the measuring unit also increases. Due to the system, the HSI 1 offers a number of spectral pixels for each lateral pixel. Here it applies that a higher spectral resolution allows a more exact thickness determination.
  • a parabolic trough mirror can also be used instead of the cylindrical lens 3, a parabolic trough mirror can also be used. This mirror has the advantage of not introducing any additional chromatic aberration into the system.
  • the spectra can be used to analyze the layer structure and thickness. In doing so one uses the optical modeling of the examined layers.
  • the reflectance response can be simulated using physical laws. If one simulates all the layer thicknesses of the examined material, a database of different reflectance curves at certain layer thicknesses is created. The measured reflectance curve is then compared to the curves of the database. The layer thickness is the value at which the curves best overlap.
  • the cylindrical lens 19 also has dispersion, whereby in the case of broadband light the focus is wavelength-dependent and therefore not localized.
  • the dispersive properties of the lens 19 produce shorter focal lengths with short-wave light than with long-wave light.
  • the parallel light beams 17 are directed by the beam splitter 4 to the measurement object 11. The parallel beam path is retained here.
  • the cylindrical lens 19 the light beams are refracted, whereby different wavelengths undergo a different refraction.
  • the cylindrical lens may be configured such that the dependence of the focal length on the wavelength is linear.
  • the rays reflected by the measuring object 11 are transmitted through the beam splitter 4.
  • the cylindrical lens 18 refocuses the beams and directs them to the entrance slit 21 presented to the detector (HSI). If portions of the incident radiation, which are not in focus, are cut out at the detector, the height of the measurement object 11 can be determined. This happens at the entrance slit 21. of the HSI. Only those wavelengths that are sufficiently focused can pass through the gap 21. If the spectrum obtained is evaluated according to the colored components, it can be determined in which height the measuring object 11 is located. In addition to the area-based analysis of layer thicknesses, this also enables the direct detection of the topography of the surface.
  • the method is based on thin-layer spectroscopy or spectral reflectometry.
  • the use of an intense, pulsed light source allows a measurement on fixed or moving objects.
  • the reflections of the light pulse at the boundary layers of the measurement object interfere. These interferences are evaluated spectrally.
  • the measurement object can move under the sensor head.
  • the evaluation is carried out by means of a model-based estimator (process- and material-optimized model)
  • the estimator's free parameters represent the quantities to be measured.
  • the evaluation follows the principle of spectral thin-layer interferometry. This measuring method is well known and utilizes the physical effect that measuring light at the boundary layers or at the surface of transparent Thin films is reflected, with the reflected measuring light interferences occur, which can be evaluated with respect to the layer properties. be evaluated to obtain statements about the properties of the investigated layer. These statements may refer to the transparent layer on the surface of the layer and possibly to further transparent layers below the transparent layer on the surface. As transparent layers are considered, which are permeable at least for a part of the measuring light.
  • the evaluation of the measurement result is carried out by comparing the measured data or the merlanale of the layer obtained therefrom, from which a feature space results.
  • Fit-based means the following: Using physical models of the layer sequence and the measuring apparatus, a spectrum is calculated, as measured for the layer thicknesses and optical layer properties incorporated into the model would. This simulated spelctram is compared to the actual measured spectrum. The parameters of the simulation are adjusted until the simulation and the real measured value match.
  • a chromatic detuning ie a spectral dependence of the focus wavelength is used to determine the height or position of the measurement object.
  • This detuning is introduced by the focus lens and ideally has an approximately linear course over the spectral width.
  • the measured reflectance curve is modulated by the chromatic detuning of the lens.
  • the distance of the measurement object to the sensor head can be determined from the measurement data set.
  • the analysis of each measurement point results in a topographical surface map.
  • Reflectometric thin-layer measurements are subject to the fluctuations of a source, as a result of which the determined layer thicknesses are likewise subject to these fluctuations.
  • the source spectrum can be co-determined in order to measure the swelling be able to compensate.
  • Fig. 3 shows this by way of example.
  • the beam splitter 4 entering collimated light 16 is deflected to a part in the direction of the measuring object 11. Another part of the light passes through the beam splitter 4 without deflection. This is the so-called loss light in the loss path.
  • a diaphragm 13a is arranged, which absorbs a portion of the loss light. Another portion of the loss light passes the aperture 13 a and is reflected by a mirror 12.
  • the reflected portion of the loss of light is deflected by the beam splitter 4 to the input gap 2.
  • An aperture 13b in the measuring path ensures that there are no overlappings at the entrance slit 2.
  • measuring light 15 reflected by the measuring object 11 and reference light 12 reflected by the mirror 12 arrive at the entrance slit 2.
  • the separation of the measured data from the source can be implemented by means of software in the evaluation device.
  • a reference measurement of the light source before or during the measurements may be necessary to determine the reflectivity of the measurement object. This reference measurement can be made possible in particular via the reference beam path.
  • a reference measurement parallel to each measurement allows the use of time-variant light sources, i. a light source whose intensity and spectrum can vary from measuring pulse to measuring pulse. Reference measurements during or between the measurement pulses allow control of the light source. This can e.g. necessary to compensate for environmental influences.
  • FIG. 4 shows the construction drawing of the device.
  • the device comprises a fiber connector 30, a collimator unit 31, a beam splitter holder 32, a lens 33, diaphragm holder 34, a reference mirror holder 35, an M42 connection for a hyperspectral imager 36 and a detector lens adjustment unit 37.
  • the components were attached to a Headwall VNIR A-Series Hyperspectral Imager.
  • the data of the hyperspectral imager were led by means of a frame grabber to a commercial PC on which the data processing took place.
  • the device and method have several advantages.
  • One advantage lies in the possibility of combining reflectometric thin-film measurement and chromatic-confocal distance measurement, which makes it possible to determine both the layer thickness and the surface profile by means of a single measuring system.
  • the measuring device is also in the ge to measure a line several millimeters long on the measuring surface in one step.
  • the measuring time is considerably reduced when measuring two-dimensional objects. While with point sensors a sampling of the measurement surface must take place in two dimensions, a scan in one dimension perpendicular to the measurement line is sufficient for the presented line sensor.
  • a fiber as an optical connection between the light source and imaging optics, a high degree of flexibility in the use of the measuring device is achieved.
  • the spatial separation between the measuring head and light source can be achieved, which greatly simplifies the integration of the measuring system in production facilities.
  • the fiber can be dispensed with by the use of the fiber as a point light source on the illumination of a light source gap, whereby the optical design requires fewer components.
  • the longitudinal measuring range is determined by changing the focal length of the objective over the observed wavelength range and determines the maximum height of the structures to be measured on the measurement surface.
  • the lateral measuring range describes the length of the line, which can be scanned in one step on the measuring surface.
  • the size of the lateral measurement region depends exclusively on the length of the input gap of the hyperspectral imager and the aperture of the cylindrical lenses.
  • the ability to co-determine fluctuations in the spectrum of the light source and to apply it instantaneously to the measurement is not possible in the prior art.
  • the reference spectrum could be co-determined instantaneously only with considerable effort, for example with a further spectrometer.
  • a distance or thin film measurement is subject to the fluctuations of the light source and thus reduces the achievable accuracy.
  • the hyperspectral imager requires very high light intensities at the input slit because the light within the device must be spectrally decomposed. In combination with the refielctometric thin-film measurement technique, this can be disadvantageous since only small intensities are reflected depending on the measurement object. Decisive for a successful measurement is therefore an efficient light coupling into the glass fiber.
  • the choice of fiber diameter also plays a decisive role here. The light power that can be coupled into the system depends on the square of the radius of the glass fiber. Due to a deterioration of the achievable lateral and longitudinal resolution with increasing fiber diameter, a compromise between the required light output and the desired resolution must be found.
  • the lateral resolution was investigated as a function of the fiber diameter.
  • the beam path in the measurement path must be very well collimated. This succeeds only with very point sources.
  • the quality of collimation increases with my expectant fiber end.
  • the simulation in FIG. 6 shows what influence the fiber diameter has on the lateral resolution.
  • a sharp edge was considered at the position 0 ⁇ at different fiber diameters. As can be seen, the sharp edge is mapped at a fiber diameter 200 ⁇ to a range of 400 ⁇ . Small fiber diameter laterally solve up to 20 ⁇ .
  • the test object is a silicon wafer with glass layers of different heights. Thus, two different layer thicknesses in certain areas are available on the test object. These layers were applied to the support in the form of a reactor. An electronic translation stage allows the sample to move under the measurement line. This creates a complete record of the layer constellation.
  • FIGS. 7 and 8 show a microreactor of the test object, once recorded with a microscope (FIG. 7) and once taken with the device according to the invention (FIG. 8).
  • the measuring system is also suitable for determining thinner layers up to approx. 30 nm.
  • the device makes it possible to generate spectroscopic data of surfaces. The focus is on the application to thin-film technologies. With the device, the reflectometric measuring principle in combination with the confocal technique is applied to hyper-spectral images. Thus, layer heights of single-layer and multi-layer systems down to the nanometer range can be measured. The technology allows topographical maps of the measured surfaces to be generated and visualized. If it is known which layer thickness the examined object has, the refractive index can, conversely, be determined as a function of location. To emphasize is the very high measuring speed and performance of the device. Another advantage is the ability to attach the device as an attachment to almost any hyperspectral imager. Almost all manufacturers of imagers have a standard optical connection on their devices, such as a C-mount or M42. These connections are standardized and guarantee faultless installation.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Optics & Photonics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

L'invention concerne un dispositif pour l'analyse confocale chromatique d'un échantillon, comprenant une source de lumière multispectrale qui est disposée dans un foyer d'un miroir creux de sorte que la lumière émise par la source de lumière est réfléchie par le miroir creux au moins en partie sous forme de rayons de lumière parallèles, un séparateur de faisceaux, disposé dans la trajectoire des rayons de lumière et conçu pour dévier les rayons de lumière au moins en partie vers un échantillon et pour laisser passer la lumière réfléchie par l'échantillon vers un dispositif détecteur, un premier dispositif de focalisation qui est disposé entre le séparateur de faisceaux et l'échantillon et qui est conçu pour focaliser la lumière sortant du séparateur de faisceaux en direction de l'échantillon en une ligne, de sorte à générer une première ligne de lumière focalisée, un second dispositif de focalisation qui est disposé entre le séparateur de faisceaux et le dispositif détecteur et qui est conçu pour focaliser la lumière réfléchie par l'échantillon en une ligne, de sorte à générer une seconde ligne de lumière focalisée, et un diaphragme à fente qui est disposé entre le second dispositif de focalisation et le dispositif détecteur. Selon l'invention, le dispositif détecteur est conçu pour effectuer une évaluation spectrale de la lumière réfléchie par l'échantillon.
PCT/EP2016/071056 2015-09-16 2016-09-07 Dispositif et procédé pour l'analyse confocale chromatique d'un échantillon WO2017045982A1 (fr)

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DE102017009804A1 (de) * 2017-10-20 2019-04-25 Vermicon Ag Verfahren zur Bewertung von mikroskopischen Proben und Vorrichtung zur Ausführung dieses Verfahrens
DE102020200214A1 (de) * 2020-01-09 2021-07-15 Hochschule für angewandte Wissenschaften Kempten Körperschaft des öffentlichen Rechts Konfokale Messvorrichtung zur 3D-Vermessung einer Objektoberfläche
CN113189102A (zh) * 2021-04-29 2021-07-30 中国工程物理研究院激光聚变研究中心 双波长双共焦激光显微测量装置与测量方法

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US20080231961A1 (en) * 2007-03-23 2008-09-25 General Electric Company Enhanced parfocality
DE102010016462A1 (de) * 2010-04-15 2011-10-20 Technische Universität München Schichtmessverfahren und Messvorrichtung
US20150131137A1 (en) * 2012-05-21 2015-05-14 Unitechologies SA Chromatic Converter for Altimetry

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US20100097693A1 (en) 2008-10-16 2010-04-22 Kazunori Koga Confocal microscope
TWI490444B (zh) 2009-01-23 2015-07-01 Univ Nat Taipei Technology 線型多波長共焦顯微方法與系統
US8654352B1 (en) 2012-08-08 2014-02-18 Asm Technology Singapore Pte Ltd Chromatic confocal scanning apparatus

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US20080231961A1 (en) * 2007-03-23 2008-09-25 General Electric Company Enhanced parfocality
DE102010016462A1 (de) * 2010-04-15 2011-10-20 Technische Universität München Schichtmessverfahren und Messvorrichtung
US20150131137A1 (en) * 2012-05-21 2015-05-14 Unitechologies SA Chromatic Converter for Altimetry

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