WO2009112288A1 - Dispositif et procédé pour déterminer un indice de réfraction d’un objet mesuré - Google Patents

Dispositif et procédé pour déterminer un indice de réfraction d’un objet mesuré Download PDF

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Publication number
WO2009112288A1
WO2009112288A1 PCT/EP2009/001893 EP2009001893W WO2009112288A1 WO 2009112288 A1 WO2009112288 A1 WO 2009112288A1 EP 2009001893 W EP2009001893 W EP 2009001893W WO 2009112288 A1 WO2009112288 A1 WO 2009112288A1
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Prior art keywords
refractive index
sensor
integrated
layer structure
layer
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PCT/EP2009/001893
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German (de)
English (en)
Inventor
Wladimir Tschekalinskij
Norbert Weber
Stephan Junger
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Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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Priority to EP09721047A priority Critical patent/EP2255174A1/fr
Publication of WO2009112288A1 publication Critical patent/WO2009112288A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/4133—Refractometers, e.g. differential
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/55—Specular reflectivity
    • G01N21/552—Attenuated total reflection
    • G01N21/553—Attenuated total reflection and using surface plasmons
    • G01N21/554—Attenuated total reflection and using surface plasmons detecting the surface plasmon resonance of nanostructured metals, e.g. localised surface plasmon resonance
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/002—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials
    • G02B1/005—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of materials engineered to provide properties not available in nature, e.g. metamaterials made of photonic crystals or photonic band gap materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/008—Surface plasmon devices
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1226—Basic optical elements, e.g. light-guiding paths involving surface plasmon interaction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/4133—Refractometers, e.g. differential
    • G01N2021/414—Correcting temperature effect in refractometers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1809—Diffraction gratings with pitch less than or comparable to the wavelength
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/201—Filters in the form of arrays

Definitions

  • the present invention relates to apparatus and methods for determining a refractive index of a measuring object.
  • the refractive index n is a good indicator for many chemical and biological applications.
  • the refractive index n changes, for example, depending on the concentration of substances dissolved in a liquid.
  • a large field of application of refractometers is the determination of the concentration and presence of a particular substance in a chemical solution, such as the original wort of beer or the water or sugar content of honey. Biological investigations of dangerous viruses and bacteria are also applications of refractometers or devices for determining the refractive index.
  • the refractometer 10 comprises a monochromatic light source 11, a measuring prism 12, on which total reflection occurs. stands, a receiving part 13, 14, which registers a position of a reflected light beam and converted into a refractive index n.
  • the refractometer shown in Fig. 1 is generally referred to as Abbe refractometer. From the light source 11 outgoing beam 15, 16, 17 meet an interface 18 of the prism 12 with the refractive index n (l) where a liquid to be examined with a refractive index n (2) is applied. The beam 17 continues in the medium with refractive index n (2), resulting in a beam 17 '. For the beam 16, total reflection occurs. The beam 15 is reflected from the boundary surface 18 of the prism 12 to the object to be measured 19 to a black painted surface 20 (15 ') - Due to this light distribution creates two fields that are light or dark.
  • the image 21 of these fields is viewed using the optical system 13 with the eye 22 or registered with a photoreceiver and further processed with an electronics 14.
  • the main part of the refractometer 10 is therefore a high-resolution optical angle sensor which determines the angle A.
  • a viewing of a working field and the angle measurement through an eyepiece with the eye has a thermostabilization of the measuring range with a digital thermometer and operates with only a measuring wavelength of 590 nm.
  • the measuring range for the refractive index n (2) is between 1.3 and 1.72.
  • a fully automatic refractometer whose measurement process is so automated that no visual channel is needed.
  • the position of the light / dark boundary is automatically evaluated.
  • Such a fully automatic refractometer may, for example, have two thermostats - one for the test sample and a second one to keep the light source, the optics and a photodiode array constant at a certain temperature.
  • a near field microscope which measure changes in the dielectric constant of the samples or objects to be examined.
  • An example of the underlying operating principle is the scanning of an object surface with an optical probe. This comprises a single-mode fiber, at the end of which there is a diaphragm with a hole diameter of about 40 nm. The light emerging from this waveguide strikes the object plane, thereby changing its evanescent field.
  • An evanescent field is generally a non-propagating component of a light field that is close to an object to be examined, the so-called near field. The evanescent field exponentially decays to the surface normal of the radiating body. Each illuminated object thus generates an evanescent and a propagating field.
  • a purely evanescent field can be observed, for example, in the case of total reflection. If an incident light beam is totally reflected at an interface of an optically denser medium to an optically thinner medium, the field may be due to the continuity condition on the side of the optically thinner medium not abruptly zero, but it falls exponentially in the half-space of the optically thinner medium. In general, the evanescent field has already disappeared at a distance of approximately ⁇ / 2 from the interface of the two optical media.
  • a remote receiver with signal processing system can register changes in the evanescent field, from which the refractive index n can be calculated.
  • Various methods for measuring the near field are described, for example, in the dissertation "A high-resolution optical near-field probe for fluorescence measurements on biological samples" by Heinrich Gotthard Frey.
  • Conventional refractometer assemblies based, for example, on the Abbe refractometer, require optical systems of multiple elements that must be positioned very accurately against each other. Furthermore, a very high measurement accuracy is required to measure the critical angle of total reflection. A measurement with several wavelengths at the same time is not possible. Furthermore, it is necessary to thermostatize the measurement object or even the entire optical system from the light source to the receiver.
  • Conventional refractometers measure the refractive index only at a predetermined wavelength, such as 590 nm.
  • the plasmon-polariton resonance is strongly dependent on a light incidence angle.
  • the evanescent field at the interface of two optical media decreases exponentially. This means that the field to be measured soon becomes small after a small distance.
  • the object of the present invention is to provide improved devices and methods for determining a refractive index of, for example, optical media by refractometry, compared with the prior art.
  • the realization of the present invention is that, for constructing a refractometer system, an integrated component with an optoelectronic sensor and structured layers of metal and / or polycrystalline semiconductor material of a layer structure which has a dependence of transmission on electromagnetic shear radiation from the dielectric constant of a test object or material in an environment of the structured layers of metal and / or polycrystalline semiconductor material can be used.
  • the measurement object can be arranged, for example, in direct contact with a surface of the integrated sensor element. That is, a measurement object whose refractive index is to be determined is arranged above the layer structure of the integrated sensor element.
  • the measurement object is arranged directly on a passivation, ie a non-metallic protective layer, of the integrated sensor element or of the sensor chip.
  • a holding device for the measurement object is provided on the sensor chip according to embodiments.
  • the measurement object can be irradiated with monochromatic light of a predetermined wavelength, so that the light can strike the integrated sensor element through the measurement object.
  • the light which has passed through the measurement object with the desired refractive index and which strikes the layer structure of the integrated sensor element can generate electromagnetic fields in the layer structure which can be detected by the optoelectronic sensor located below the layer structure.
  • the detected electromagnetic fields are dependent on the refractive index of the measurement object, which is located on the chip surface of the integrated sensor element. That is, an output signal of the optoelectronic sensor, such as a photocurrent of a photodiode, is dependent on the desired refractive index.
  • an output signal of the optoelectronic sensor such as a photocurrent of a photodiode
  • Embodiments of the present invention provide a system for determining a refractive index of a measurement object, with a light source for emitting light of a predefined wavelength, an integrated sensor element with an opto-electronic sensor and a layer structure with at least one structured layer of metal or polycrystalline semiconductor material, wherein the optoelectronic sensor and the layer structure are integrated together on a semiconductor substrate.
  • the system comprises a device for holding the measurement object between the integrated sensor element and the light source, so that the layer structure is arranged between the measurement object and the optoelectronic sensor, so that an output signal of the optoelectronic sensor is dependent on the refractive index of the measurement object changes.
  • a device for determining the refractive index of the measurement object is also provided based on the output signal of the optoelectronic sensor.
  • the layer structure of the integrated sensor element may have properties of a photonic crystal.
  • a photonic crystal is to be understood below to mean a three-dimensional periodic structure whose periodically arranged structural elements have dimensions and distances from one another which are of the order of a predetermined wavelength range for electromagnetic radiation which transmits through a photonic crystal to an optoelectronic sensor assigned to it can be.
  • Photonic crystals comprise structured metals, semiconductors, glasses or polymers and force electromagnetic radiation, in particular light, by means of their specific structure to propagate in the medium in the manner necessary for a component function.
  • periodic dielectric and / or metallic structures whose structural period length is set such that they influence the propagation of the electromagnetic radiation, in particular light, in a similar manner as the periodic potential in semiconductor crystals influence the propagation of electrons.
  • the spectral filtering effect of photonic crystals has been known for some years and confirmed by experiments. The spectral properties of periodically structured layers of metal and / or polycrystalline semiconductor material are highly dependent on the shape of the individual structural elements.
  • the layer structures have structure or microelements whose dimensions and distances from each other are of the order of the predetermined wavelength, in particular the wavelength of the monochromatic light of the light source, for which the integrated spectral filter structure is in the form of at least one photonic crystal ,
  • the microelements of the structured layers of metal and / or polycrystalline semiconductor material may be periodically arranged three-dimensionally. According to embodiments, adjacent microelements of adjacent layers are formed identically for the predetermined wavelength and lie on a common optical axis.
  • Microelements may according to embodiments be micro-openings with dimensions and distances in the respectively provided transmission wavelength range. According to embodiments, the microelements may comprise so-called split-ring resonators with dimensions and distances in the respective predetermined transmission range.
  • a single sensor element is formed from an optoelectronic sensor and a metal structure covering the optoelectronic sensor, for example one or more structured metal layers which are structured in such a way that for a predetermined wavelength range or a predetermined wavelength can form a plasmon-polariton resonance effect. Due to a sub-wavelength opening in the patterned metal layer may be due to the predetermined wavelength of the plasmon-polariton resonance effect in the vicinity of the opto-electronic sensor form an electromagnetic field concentration, which can then be detected by the opto-electronic sensor.
  • the plasmon-polariton resonance effect leads to a so-called extraordinary optical transmission, which can take place through slots or holes in metals which are smaller than a wavelength of the predefined wavelength range or the predefined resonance wavelength.
  • a surface plasmon is a density sway of charge carriers at the boundary of semiconductors or metals to dielectric media and is one of many interactions between light and a metallic surface, for example.
  • the distance between the optoelectronic sensor and the layer structure is less than 20 ⁇ m and preferably less than 8 ⁇ m.
  • the distance between the optoelectronic sensor and the layer structure is less than 2 ⁇ m.
  • the distance between the opto-electronic sensor and the layer structure is preferably within the range of the electromagnetic near field.
  • the means for holding together with the integrated sensor element is integrated together on the semiconductor substrate.
  • the means for holding may comprise a frame structure on the surface of the integrated sensor element, such that a receptacle results, for example, for a liquid to be analyzed.
  • the frame structure can be formed by the passivation of the chip, so that the passivation with frame a kind of analysis basin for Liquids is formed, in which to be examined fluids can be given.
  • the device for determining the refractive index is designed as evaluation electronics, which is integrated according to preferred embodiments, together with the opto-electronic sensor and the layer structure on the semiconductor substrate is integrated into a single chip.
  • a refractometer system according to the invention thus requires no further optical components except for external illumination.
  • a refractometer system may even be fully integrated into a single chip.
  • an optoelectronic component is additionally provided on the substrate as an exposure source, such as e.g. an LED or a laser, so that no external components are necessary at all.
  • the integrated sensor of the refractometer system is based on three-dimensional sub-wavelength structured metal and / or dielectric layers and photodiodes that are part of the integrated circuit sensor element.
  • the sensor chip may e.g. be manufactured within a CMOS process and requires no adjustment.
  • a measuring device and electronics for signal processing are integrated according to embodiments in a circuit.
  • one or more temperature sensors are integrated in the sensor element and are therefore located in the vicinity of the test object to be examined (typically 3-4 ⁇ m away).
  • the temperature sensors can therefore provide accurate values of the temperature of the liquid to be tested.
  • Embodiments of the present invention further enable simultaneous measurement with multiple monochromatic light sources.
  • a plurality of sensor elements can be used whose layer structures are adapted to the respective wavelength.
  • the number of wavelengths or measuring points can be freely defined in a system design.
  • the light source and the sensor chip are fixed to each other, i. a position between the illumination and the measuring chip does not change. Angular errors between the light source and the measuring chip can thus always be calibrated out.
  • the optoelectronic sensor or the photodiode is arranged very close to the test object to be examined (a few ⁇ m away).
  • transmission losses of evanescent fields can be significantly reduced, which can lead to a considerable increase in a signal-to-noise ratio compared to near-field microscopy.
  • increased measurement accuracy is achievable and allows use of a weaker light source.
  • the integrated sensor element or the integrated sensor chip can be produced for example with a CMOS technology. Such a technology has a high accuracy and repeatability and is ideally suited for mass production. Thus, relatively low prices for end products can be achieved, whereby one-way refractometers can be realized.
  • the integrated sensor chip integrates well into a manufacturing process, so that its surface always has an optical contact with a liquid.
  • embodiments of the present invention provide a means for dynamic analysis of refractive index changes.
  • Fig. 1 is a schematic representation of a conventional refractometer
  • FIG. 2 shows an illustration of a system for determining a refractive index of a test object according to an exemplary embodiment of the present invention
  • FIG. 3 shows a side view of a layer stack of optoelectronic sensor, metal layers and dielectric layers produced by CMOS technology according to one exemplary embodiment of the present invention
  • FIG. 4 shows a schematic perspective view of a sensor element with a receiving frame for liquid according to an exemplary embodiment of the present invention
  • FIG. 5a, 5b representations of an integrated sensor element to illustrate an evanescent field propagation in the integrated sensor chip according to embodiments of the present invention
  • FIG. 6 shows transmission curves of light through a layer structure according to exemplary embodiments of the present invention as a function of a desired refractive index
  • FIG. 7 shows a schematic illustration of an integrated sensor chip with integrated temperature sensor according to an exemplary embodiment of the present invention
  • FIG. 8 shows a plan view of a structured metal layer with split-ring resonators according to an exemplary embodiment of the present invention
  • FIG. 9 shows a schematic representation of a plurality of integrated sensor elements, adapted to different wavelengths of light, according to an exemplary embodiment of the present invention.
  • FIG. 10 shows a schematic structure of a refractometer according to an exemplary embodiment of the present invention
  • FIG. 11 is a perspective view of a structured metal layer according to an embodiment of the present invention.
  • FIG. 12 shows a perspective view of a structured metal layer according to a further exemplary embodiment of the present invention.
  • Fig. 13 is a schematic view of a metal layer having a two-dimensionally periodic arrangement of sub-wavelength openings.
  • FIG. 14 shows a side view of a layer stack made of opto-electronic sensor and layers of metal and polycrystalline semiconductor material produced by CMOS technology according to a further exemplary embodiment of the present invention.
  • FIG. 2 schematically shows a system 30 for determining a refractive index n (object) of a measuring object 31, according to an embodiment of the present invention.
  • the system 30 includes a light source 32 for emitting preferably monochromatic light 33 of a predefined wavelength. Further, an optic 34 may be provided to diffuse the light 33. The optic 34 may be, for example, a telescopic lens. Furthermore, the system 30 has an integrated sensor element 35 with an optoelectronic sensor 36 and a layer structure 37 with at least one structured layer of metal or polycrystalline semiconductor material, wherein the optoelectronic sensor 36 and the layer structure 37 are integrated together on a semiconductor substrate 38 , A device 39 serves to hold the measurement object 31 between the integrated sensor element 35 and the light source 33, so that the layer structure 37 is arranged between the measurement object 31 and the opto-electronic sensor 36, and so that an output signal of the opto-electronic sensor 36 depending on the refractive index n (object) of the measuring object 31 changes.
  • the optoelectronic sensor 36 is coupled to a device 40 for determining the refractive index n (object) of the measuring object 31 based on the output signal of the opt
  • the (metal) layer structure may be designed such that the measuring device output signal of the sensor 36 depends on the refractive index of the measurement object 31 according to a plasmon-polariton effect, for example according to a dependence as described in the publication "Defracted evanescent wave model for enhanced and suppressed optical transmission through subwavelength hole arrays", describing a transmission function measured by a numerical aperture lens NA can be calculated by multiplying a first surface modulation function Ai ( ⁇ ), an intrinsic transmission function D H ( ⁇ ) by a micro-aperture, a second surface modulation function A 2 (A) and a function f c ( ⁇ ) representing a part of the transmitted power through the layer structure, The transmission function D c ( ⁇ ) can then be written as
  • TC ( ⁇ ) AK ⁇ ; n (object); Pl; d ⁇ ) TH ( ⁇ ; r7 H; d; t) A2 ( ⁇ n2; P2; d2) fC ( ⁇ , NA; P2; d2);
  • Pl and P2 give lattice constants or repeat distances of structures around an aperture or nano-opening, dl and d2 lateral dimensions of the nano-openings, NA the numerical aperture, t the layer thickness of the metal layer, n H the refractive index of the medium within the nano-openings.
  • n the refractive index in front of the metal layer, ie the refractive index n (object) of the specimen or of the object or the known refractive index n (reference) of a reference object, such as air
  • n 2 is the refractive index of the medium behind the metal layer
  • ⁇ the wavelength.
  • TC is in turn proportional or at least uniquely dependent on the sensor output of the sensor.
  • Al can be given as wherein ⁇ , the amplitude of CDEW (composite diffracted EVA nescent wave), that is, the composite broken EVA neszenten shaft, n eff indicates the effective refractive index, the CDEW learns and P indicates the Widerholabstand the 2N grooves which surround the slot ,
  • the layer structure 37 may be at least one metal layer having subwavelength structures, e.g. Micro or nano-openings, act.
  • subwavelength structures e.g. Micro or nano-openings, act.
  • Such subwavelength structures allow passage of an electromagnetic field, e.g. in the form of an evanescent field, towards the optoelectronic sensor 36.
  • the layer structure 37 may be a three-dimensional photonic crystal or a periodic arrangement of a plurality of three-dimensional photonic crystals, the layer structure 37 or each of the three-dimensional photonic crystals being formed from a layer stack of dielectric layers and structured metal layers , which will be discussed in more detail below.
  • FIG. 8 represents a schematic plan view of the layer structure 37, which is to be understood below as a photonic crystal or an array of photonic crystals.
  • the layer structure 37 with the at least one photonic crystal 82 for electromagnetic radiation 33 arriving on a side remote from the opto-electronic sensor 36 effects a spectral selection or a spectral filtering of electromagnetic radiation. For this reason, an electromagnetic field concentration predominates near a side of the layer structure 37 facing the optoelectronic sensor or near the optoelectronic sensor 36 for the predefined wavelength range, which is detected by the optoelectronic sensor can.
  • the optoelectronic sensor 36 is a component which can convert electromagnetic radiation, in particular light, into an electrical output signal, such as, for example, a PN junction sensor, which can be designed as a photodiode.
  • the layer structure 37 causes a plasmon-polariton resonance effect to form for the predetermined wavelength range or the predetermined wavelength.
  • a sub-wavelength opening in the layer structure 37 an electromagnetic field concentration can form for the predetermined wavelength due to the plasmon-polariton resonance effect in the vicinity of the optoelectronic sensor 36, which can then be detected by the optoelectronic sensor 36.
  • the layered structure 37 has a sub-wavelength dimension opening 118.
  • the sub-wavelength opening 118 according to exemplary embodiments is surrounded by rotationally symmetrical periodically arranged grooves 142 around the opening. With proper sizing of the opening 118 and the grooves 142, a resonant interaction of the electromagnetic radiation and the surface plasmons of the layered structure 37 may result in the above-mentioned enhanced extraordinary transmission in the predetermined wavelength range.
  • a structure element 140 of the layer structure 37 comprises a region of a metal layer which has a periodically structured surface of the period A with depressions 142 and elevations 144 and a sub-wavelength opening 118 which lies in the center of the structure 140.
  • a predetermined resonant wavelength ⁇ res of an incident on the structure 140 e- lektromagnetician radiation 33
  • the plasmon-polariton resonance effect causes for the resonant wavelength ⁇ res through the sub-wavelength opening 118, for example, more than 15% of the incident electromagnetic radiation, although an area ratio of the opening 118 to the surface of the entire element 140 is very small.
  • the transmission for a predetermined wavelength ⁇ res through the structural element 140 is of the area ratio the area of the opening 118 depends on the area of the entire element 140, as well as the period A of the structured surface or elevations 144 and depressions 142.
  • the period A which allows the highest transmission depends inter alia on the thickness (t + h) of the structured metal layer.
  • the width or diameter b of the aperture 118 could be chosen to be 110 nm
  • the area ratio of the area of the aperture 118 to the area of the entire element 340 could be 0.01
  • A could be to 90 nm and t to 20 nm.
  • A is in a range of 10 nm to 2110 nm.
  • the thickness (t + h) of the metal layer is in embodiments in a range of 30 nm to 2500 nm, preferably in one range from 350 nm to 550 nm.
  • the height h of the recess is of course smaller than the thickness (t + h) of the metal layer and in embodiments is in a range above (t + h) / 2.
  • the area ratio of the area of the opening 118 to the area of the entire element 140 is less than 0.3 in embodiments.
  • non-rotationally symmetric surface structures of the layer structure 37 are also conceivable, which can cause the plasmon-polariton resonance effect, such as a slot-shaped opening with grooves arranged parallel thereto (FIG. 12) or a matrix-like arrangement of sub-wavelength openings, as shown in FIG 13 is shown.
  • the layer structure 37 thus has, for example, according to exemplary embodiments, a structured metal layer with an opening 118 with sub-wavelength dimensions, hereinafter also referred to as sub-wavelength opening, and rotationally symmetrical or parallel grooves or corresponding projections or elevations arranged periodically around the sub-wavelength opening are embedded in a dielectric in order to generate the surface plasmon-polariton resonance effect for the predetermined wavelength range in the layer structure 37.
  • a sub-wavelength opening is a circular or slot-shaped opening having a width or a diameter smaller than the predefined wavelength of the light or the electromagnetic radiation 33.
  • CMOS processes such as a CMOS opto process, without the need for additional process steps or further processing.
  • a method for manufacturing an integrated sensor element on a substrate comprises a step of generating the opto-electronic Sensor 36 on a substrate surface of the substrate 38 and applying a filter or layer structure 37 with at least one photonic crystal on the optoelectronic sensor 36, so that the opto-electronic sensor 36 at a distance d less than 3 microns, preferably less than 2 ⁇ m, of which at least one photonic crystal is located and completely covered by it, the generating and depositing being part of a CMOS process.
  • the application of the at least one photonic crystal 82 comprises depositing a layer stack of dielectric layers and metal layers, the metal layers each having microstructures 84 having dimensions and spacings between two adjacent microstructures 84 that transmit electromagnetic radiation of the predefined wavelength range through the at least one photonic crystal 82 allow.
  • FIG. 3 An intermediate product of an integrated sensor element 35 of a refractometer system according to exemplary embodiments is shown schematically in FIG. 3.
  • the integrated sensor 41 which is not yet completely manufactured, shown in FIG. 3, comprises a substrate 38, in particular a semiconductor substrate, in which an optoelectronic sensor 36 is introduced.
  • the opto-electronic sensor 36 is arranged in a plane 42, a type of focal plane known from classical optics.
  • the unfinished optical structure 41 has a layer stack of metallic layers 44 and dielectric layers 46. 3 merely exemplarily shows four metallic layers 44-1 to 44-4 and three dielectric layers 46-1 to 46-3. Depending on the embodiment, the number of layers may differ from the example shown in FIG. 3. In current CMOS processes, it is possible to pattern the metal layers 44 such that resulting microstructures or microelements 84 are arranged periodically and have dimensions and spacings which are smaller than the wavelength of the light 33 of the light source 32. This makes it possible to produce three-dimensional periodic structures with properties of photonic crystals directly on a chip. As already described above, in embodiments, the individual microelements or microstructures 84 are smaller than 1/10 of the predetermined optical wavelength, so that a three-dimensional photonic crystal is formed.
  • the opto-electronic sensor 36 is preferably placed very close to the last metal layer 44-1 of the layer structure 37, the distance d being dependent on the manufacturing process.
  • the distance d from the last metal layer 44-1 of the filter structure 37 can be adjusted by dimensions and spacings of patterns of the metal layers 44.
  • the distance d is chosen to be less than 20 ⁇ m and preferably less than 8 ⁇ m.
  • the distance between the opto-electronic sensor 36 and the layer structure 37 or the last metal layer 44-1 is less than 2 ⁇ m.
  • the metal layers 44-1 to 44-4 shown by way of example in FIG. 3 are suitably structured in a CMOS process in order to obtain a photonic crystal or a layer structure for the plasmon-polariton effect.
  • An integrated sensor element 35 can thus be realized by utilizing existing metallic and dielectric layers 44, 46.
  • the opto-electronic sensor 36 of the integrated sensor element 35 is preferably in accordance with embodiments of the structured metal layers 44 completely covered.
  • a measuring object 31 is applied to a surface of the integrated sensor element 35, which is formed, for example, by a passivation layer 48 over the uppermost structured metal layer 44-4, then an optical transmission through the layer structure 37 changes as a function of the dielectric constant of FIG Surface of the measured object 31.
  • An output signal of the opto-electronic sensor 36 e.g. a photocurrent of a photodiode, is dependent on the optical transmission of the overlying layer stack 37 of sub-wavelength-structured metal and / or dielectric layers 44, 46.
  • the transmission of the layer stack 37 is in turn dependent on the refractive index n (object) of the measurement object 31, which is arranged above the layer stack 37.
  • a device 39 for holding in accordance with preferred exemplary embodiments together with the integrated sensor element 36 and the layer stack 37 is jointly applied to the semiconductor substrate
  • the means 39 for holding may, for example, comprise a frame structure 49 on the surface of the integrated sensor element 35, so that a receptacle, for example for a liquid to be analyzed, results as the measurement object 31.
  • the frame structure 49 can be formed by the passivation 39 of the chip, so that the passivation with frame forms a kind of analysis basin for liquids into which liquids to be examined can be added.
  • the frame structure 49 is not mandatory. For the For example, other measures could be taken, such as laying a slide on the sample so that the sample forms a monolayer on the passivation of the chip.
  • the change in transmission as a function of the desired refractive index n (object) can be determined by certain properties of the optical microstructures or nanostructures 84 of the layer structure 37.
  • an evanescent field or a resonance change is determined by the optoelectronic sensor 36 and then calculated back to the refractive index n (object) of the test object 31.
  • a measurement object 31 eg, liquid
  • a measurement object 31 having a known refractive index
  • Calibration without a specific calibration measurement object ie calibration with air as the calibration measurement object, is also conceivable. It is essential that during calibration the refractive index of the medium 31 located above the layer structure 37 is known. If a measurement is started, the photodiode 36, which is arranged in the immediate vicinity of the last metal layer 44-1, receives a light field transmitted through the measurement object 31 and the layer structure 37.
  • a value dependent on a change in transmission with respect to the calibration transmission which corresponds to the refractive index changes between the calibration medium and the test object 31 to be examined.
  • a special calibration sensor element may be provided on a chip, which is constructed similarly to sensor elements actually used for refractive index measurements.
  • the calibration sensor element as described above, there is a calibration measurement object with a known refractive index, or simply not just the measurement object but, for example, air or vacuum.
  • a temperature sensor 47 is additionally integrated in the integrated sensor element 35. With this additionally integrated temperature sensor 47 can be accurately determine which temperature the measurement object 31 has to make a corresponding correction of the determined refractive index n (object) depending on the temperature detected by the temperature sensor 47.
  • the above-mentioned calibration procedure only needs to be carried out once for a specific height h of the measurement object 31.
  • the distance between the photoreceptor 36 and the location where the evanescent field 52 is formed is only a few microns or less according to embodiments.
  • the smallest possible distance between the optoelectronic sensor 36 and the layer structure 37 is very important for the dimensioning of the integrated sensor element 35, wherein the intensity of the evanescent field 52 decreases exponentially with increasing distance from the interface.
  • measurement results are much more accurate, because here Distance between the photodiode 36 and the medium to be examined 31 is only in the micron range.
  • the "classical optics" implies that in such a case the whole energy of the electromagnetic radiation is reflected, in reality an evanescent field 52 is created at the boundary between the object to be examined 31 and the glass plate 39.
  • this evanescent field 52 is transmitted to the photodiode 36 through the layer structure 37, which has sub-wavelength-structured metal and / or dielectric layers.
  • the output signal or the photocurrent of the photodiode 36 is ultimately dependent on the refractive index n (object) of the test object 31.
  • a second physical effect that can be used for constructing a refractometer system 30 according to the invention is utilization of resonance wavelengths of the transmission spectrum of the layer structure 37 of the integrated sensor element 35.
  • Resonance wavelengths of a light field passing through the layer structure 37 are dependent on the dielectric constant of the environment Layer Structure 37.
  • a first resonance curve 61 describes a resonance behavior at a first refractive index n (b) of a first test object to be examined (eg calibration object).
  • a second resonance curve 62 results when the first measurement object is replaced by a second measurement object with a refractive index n (unb).
  • FIG. 7 shows another possible structure of an integrated sensor element 35 according to an embodiment of the present invention.
  • the integrated sensor element 35 has a structured metal layer 44 above the photodetector 36, wherein the metal of the structured metal layer 44 has a refractive index n (Me).
  • a dielectric material having a refractive index n (D) is arranged.
  • the refractive index of the measuring object 31 arranged above the structured metal layer 44 is n (unb).
  • the structured metal layer 44 allows, for example, a plasmon-polariton effect, as has already been described above.
  • the resonance wavelengths of a resulting transmission spectrum depend on the refractive index of the measurement object n (unb), the refractive index of the metal n (Me), the metal layer thickness d and the refractive index n (D) of the dielectric material in the openings.
  • n (Me), n (D) and the metal layer thickness d are given and are constant. Only the refractive index n (unb) of the environment or the measuring object 31 is variable. If the refractive index n (b) of a reference measurement object changes to n (unb), then the transmission curve shifts, as shown in FIG. In the case shown here, this means that in monochromatic illumination with a predefined wavelength of light, e.g. ⁇ (l), the resulting transmission T ( ⁇ ) becomes smaller.
  • the photocurrent of the photodiode 36 can first be measured with a reference measurement object having a known refractive index n (b) and corresponding illumination with a monochromatic wavelength ⁇ (l). Subsequently, the measurement is made with a test object 31 to be examined with refractive index n (unb). The difference of the photocurrent can be converted into the desired refractive index n (unb).
  • a transmission function measured by a lens with numerical aperture NA can be calculated by multiplying a first surface modulation function Ai ( ⁇ ), an intrinsic transmission function D H ( ⁇ ) by a micro-aperture, a second surface modulation function ⁇ 2 ( ⁇ ) and a function f c ( ⁇ ) representing a portion of the transmitted power through the layer structure
  • the transmission function D c ( ⁇ ) can then be written as
  • TC ( ⁇ ) A ⁇ ( ⁇ ; n ⁇ ; P ⁇ , d ⁇ ) TH ( ⁇ ; nH; d; t) A2 ( ⁇ n2; P2; d2) fC ( ⁇ , NA; P2; d2);
  • sub-wavelength structure 84 is a circular opening.
  • a microstructure 84 such as e.g. so-called split-ring resonators, as they are shown by way of example in a plan view of a structured metal layer in FIG. 8.
  • such a measuring chip can be mass-produced very inexpensively, even with the necessary electronics 40 for the signal processing, which is located in the device for determining the refractive index of the test object.
  • a sensor chip can for example be installed in a plug-in socket, so that it can be easily replaced after a measurement against a new sensor chip.
  • FIG. 10 shows a schematic structure of a refractometer system based on the sensor chip 90 shown in FIG. 9.
  • Light 33 from one or more monochromatic light sources 32 reaches the chip 90, which has at least one sensor element 35 with opto-electronic sensor 36 and sub-wavelength-structured metal layers 44. After amplification of an output signal of the optoelectronic sensor, signal processing takes place, which can also be integrated in the sensor chip itself by evaluation electronics 40. As a result, a desired refractive index n (object) can be determined.
  • the structure shown in FIG. 10 no additional optical elements, such as a prism or micro-wave, are used. needed in conventional refractometers.
  • the structure shown in Fig. 10 also has no mechanical moving elements.
  • the light source 32 may also be integrated into the sensor chip 90 according to embodiments, so that external illumination is no longer necessary.
  • LEDs that can be manufactured within the framework of a CMOS-compatible process - simultaneously with the opto-electronic sensor 36 and the evaluation electronics 40.
  • the refractive index of solids can be determined with the inventive concept, if the surface of the solid is well polished, so that between the material to be examined 31 and the measuring chip 35 is a good optical contact.
  • An integrated sensor element or an integrated sensor chip 35, 90 can be produced for example with a CMOS technology. Such technology has high accuracy and repeatability and is well suited for mass production. Thus, relatively low prices for end products can be achieved, whereby disposable refractometers can be realized.
  • the integrated sensor chip can be easily integrated into a manufacturing process, so that its surface always has an optical contact with a measured object. Therefore, embodiments of the present invention also provide a means for dynamically analyzing refractive index changes.
  • FIG. 14 shows, like FIG. 3, an exemplary embodiment of an integrated device produced in CMOS technology. ruled sensor element. As can be seen, the same layers as in FIG. 3 exist according to this CMOS technique. However, a polysilicon layer 700 is arranged between the lowermost metal layer 44-1 and the semiconductor substrate 38.
  • an integrated sensor element by combining the optoelectronic sensor 36 with a layer structure which is obtained not only by the metal layers but also by structuring of the polysilicon layer 700, ie in combination with a structuring of one or more of the metal layers 44-1 to 44-4.
  • a combination of multiple polysilicon layers would also be possible if such layers are present in the technology used.
  • the polysilicon layer 700 rests directly on the substrate 38.
  • the polysilicon layer 700 could also be farther from the semiconductor substrate 38, if allowed by a respective CMOS process.
  • a filter structure by structuring only one polysilicon layer.
  • polysilicon instead of the use of polysilicon, it would also be possible to use other polycrystalline semiconductor material.
  • the patterning of layer 700 to obtain a suitable refractive index determining effect as shown above may be performed in the same manner and shapes as described above with respect to the metal layers.
  • CMOS metal layers such as, for example, the CMOS metal layer
  • CMOS metal layer can have electrical connections or interconnects in addition to the openings for forming the layer structures, the electrical connections between circuit elements (eg transistors) of the manufacture integrated sensor element. This also applies to the post shown above. silicon layer. Also, the laterally spaced apart from the actual opto-electronic sensors can be used to form interconnects or components.

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Abstract

L’invention concerne un système (30) pour déterminer un indice de réfraction (n(Objet)) d’un objet mesuré (31), comprenant une source de lumière (32) pour émettre de la lumière (33) à une longueur d’onde prédéfinie, un élément de détection intégré (35) qui comprend un détecteur optoélectronique (36) et une structure stratifiée (37) constituée d’au moins une couche métallique structurée (44). Selon l’invention, le détecteur optoélectronique (36) et la structure stratifiée (37) sont intégrés conjointement sur un substrat en semiconducteur (38). L’objet de l’invention comprend également un dispositif (39) pour maintenir l’objet mesuré (31) entre l’élément de détection intégré (35) et la source de lumière (32), de telle sorte que la structure stratifiée (37) est disposée entre l’objet mesuré (31) et le détecteur optoélectronique (36) et de telle sorte qu’un signal de sortie du détecteur optoélectronique (36) résultant de la lumière (33) ayant la longueur d’onde prédéfinie varie en fonction de l’indice de réfraction (n(Objet)) de l’objet mesuré (31), et un dispositif (40) pour déterminer l’indice de réfraction (n(Objet)) de l’objet mesuré (31) en se basant sur le signal de sortie du détecteur optoélectronique (36).
PCT/EP2009/001893 2008-03-14 2009-03-16 Dispositif et procédé pour déterminer un indice de réfraction d’un objet mesuré WO2009112288A1 (fr)

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DE102013015065A1 (de) * 2013-09-09 2015-03-12 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren und Anordnung zum Erfassen von optischen Brechzahlen oder deren Änderung
DE102017126708A1 (de) 2017-11-14 2019-05-16 Universität Ulm Institut Für Optoelektronik Verfahren und Vorrichtung zur Bestimmung des Brechungsindex eines Mediums

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