Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14643—Photodiode arrays; MOS imagers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/1462—Coatings
  • H01L27/14621—Colour filter arrangements
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
  • H04N23/10—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths
  • H04N23/11—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths for generating image signals from visible and infrared light wavelengths
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/14625—Optical elements or arrangements associated with the device
  • H01L27/14627—Microlenses
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14643—Photodiode arrays; MOS imagers
  • H01L27/14645—Colour imagers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14665—Imagers using a photoconductor layer
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K39/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic radiation-sensitive element covered by group H10K30/00
  • H10K39/30—Devices controlled by radiation
  • H10K39/32—Organic image sensors

Definitions

• the present application relates to an image sensor or electronic imager.
• Image sensors are used in many fields, in particular in electronic devices thanks to their miniaturization. Image sensors are found either in human-machine interface applications or in image-taking applications.
• an image sensor allowing simultaneous acquisition of a color image and an infrared image.
• Such an image sensor is called a color and infrared image sensor in the remainder of the description.
• An example of application of a color and infrared image sensor relates to the acquisition of an infrared image of an object on which is projected a structured infrared pattern. Areas of use for such image sensors include automobiles, drones, smartphones, robotics and augmented reality systems.
• the phase during which the pixel collects charges under the action of incident radiation is called the integration phase of a pixel.
• the integration phase is generally followed by a reading phase during which a measurement of the quantity of charges collected by the pixel is carried out.
• Several constraints are to be taken into account for the design of a color and infrared image sensor. First, the resolution of the acquired color images should not be lower than that obtained with a conventional color image sensor.
• the image sensor may be of the global shutter type, also called Global Shutter, that is to say implementing an image acquisition process in in which the beginnings and ends of the pixel integration phases are simultaneous. This may be the case in particular for the acquisition of an infrared image of an object onto which a structured infrared pattern is projected.
• Global Shutter global shutter type
• the size of the pixels of the image sensor is as small as possible.
• the fill factor of each pixel which corresponds to the ratio between the area, in top view, of the area of the pixel actively participating in the capture of the incident radiation and the total area, with a view to above, of the pixel, or as large as possible.
• One embodiment overcomes all or part of the drawbacks of the color and infrared image sensors described above.
• the resolution of the color images acquired by the color and infrared image sensor is greater than 2560 ppi, preferably greater than 8530 ppi.
• the method for acquiring an infrared image is of the Global Shutter type.
• the size of the pixels of the color and infrared image sensor is less than 10 ⁇ m, preferably less than 3 ⁇ m.
• the fill factor of each pixel of the color and infrared image sensor is greater than 50%, preferably greater than 80%.
• One embodiment provides a color and infrared image sensor comprising a silicon substrate, MOS transistors formed in the substrate and on the substrate, first photodiodes formed at least in part in the substrate, disjoint photosensitive blocks covering the substrate and color filters covering the substrate, the image sensor further comprising first and second electrodes on either side of each photosensitive block and delimiting a second photodiode in each photosensitive block, the first photodiodes being configured for absorbing electromagnetic waves of the visible spectrum and each photosensitive block being configured to absorb electromagnetic waves of the visible spectrum and a first part of the infrared spectrum.
• the image sensor further comprises an infrared filter, the color filters being interposed between the substrate and the infrared filter, the infrared filter being configured to pass the electromagnetic waves of the visible spectrum, to allow electromagnetic waves of said first part of the infrared spectrum to pass and to block electromagnetic waves of at least a second part of the infrared spectrum between the visible spectrum and the first part of the infrared spectrum.
• the photosensitive blocks and the color filters are at the same distance from the substrate.
• the photosensitive blocks are closer to the substrate than the color filters.
• each photosensitive block is covered with a visible light filter made of organic materials.
• the image sensor further comprises a matrix of lenses interposed between the substrate and the infrared filter.
• the image sensor further comprises, for each pixel of the color image to be acquired, at least first, second and third subpixels each comprising one of the first photodiodes and l one of the color filters, the color filters of the first, second and third subpixels allowing electromagnetic waves to pass in different frequency ranges of the visible spectrum, and a fourth subpixel comprising one of the second photodiodes.
• the image sensor further comprises, for each first, second and third sub-pixel, a first read circuit connected to the first photodiode and, for the fourth sub-pixel, a second read circuit connected to the second photodiode.
• the first read circuits are configured to transfer first electrical charges generated in the first photodiodes to a first electrically conductive track and the second read circuit is configured to transfer second charges generated in the second photodiode to the first electrically conductive track or a second electrically conductive track.
• the first photodiodes are arranged in rows and columns and the first read circuits are configured to control the generation of the first charges during the first simultaneous time intervals for all the first photodiodes of the sensor. images, or shifted in time from one row of first photodiodes to another, or, for each pixel of the color image to be acquired, shifted in time for the first, second and third sub-pixels.
• the second photodiodes are arranged in rows and columns and the second read circuits are configured to control the generation of the second charges during second simultaneous time intervals for all of the second photodiodes of the sensor. images.
• the photosensitive layer is made of organic materials.
• FIG. 1 is an exploded perspective view, partial and schematic, of an embodiment of a color and infrared image sensor
• Figure 2 is a sectional view, partial and schematic, of the image sensor of Figure 1;
• FIG. 3 is an exploded perspective view, partial and schematic, of another embodiment of a color and infrared image sensor;
• Figure 4 is a sectional view, partial and schematic, of the image sensor of Figure 3;
• FIG. 5 is an electric diagram of an embodiment of a circuit for reading a sub-pixel of the image sensor of FIG. 1;
• FIG. 6 is a timing diagram of signals of an embodiment of an operating method of the image sensor having the read circuit of FIG. 5.
• a signal is called “binary signal” which alternates between a first constant state, for example a low state, denoted "0", and a second constant state, for example a high state, denoted "1".
• the high and low states of different binary signals of the same electronic circuit can be different.
• the binary signals may correspond to voltages or currents which may not be perfectly constant in the high or low state.
• the terms "insulator” and “conductor” mean respectively “electrically insulating” and “electrically conductive”.
• the transmittance of a layer corresponds to the ratio between the intensity of the radiation leaving the layer and the intensity of the radiation entering the layer.
• a layer or a film is said to be opaque to radiation when the transmittance of the radiation through the layer or the film is less than 10%.
• a layer or a film is said to be transparent to radiation when the transmittance of the radiation through the layer or the film is greater than 10%.
• the refractive index of a material corresponds to the refractive index of the material for the range of wavelengths of the radiation picked up by the image sensor. Unless otherwise indicated, the refractive index is considered to be substantially constant over the wavelength range of the useful radiation, for example equal to the average of the refractive index over the range. range of wavelengths of radiation picked up by the image sensor.
• visible light is called electromagnetic radiation whose wavelength is between 400 nm and 700 nm and infrared radiation is called electromagnetic radiation whose wavelength is between 700 nm and 1 mm.
• infrared radiation one distinguishes in particular the near infrared radiation, the wavelength of which is between 700 nm and 1.4 ⁇ m.
• One pixel of an image corresponds to the unitary element of the image captured by an image sensor.
• the optoelectronic device is a color image sensor, it generally comprises for each pixel of the color image to be acquired at least three components which each acquire a light radiation substantially in a single color, that is, that is, in a wavelength range less than 100nm (eg, red, green and blue).
• Each component can in particular comprise at least one photodetector.
• Figure 1 is an exploded perspective view, partial and schematic, and Figure 2 is a sectional view, partial and schematic, of an embodiment of a color and infrared image sensor 1.
• the image sensor 1 comprises a matrix of first photon sensors 2, also called photodetectors, suitable for capturing an infrared image, and a matrix of second photodetectors 4, suitable for capturing a color image.
• the matrices of photodetectors 2 and 4 are associated with a matrix of read circuits 6 carrying out the measurement of the signals picked up by the photodetectors 2 and 4.
• read circuit is meant a set of read, address and transistors. for controlling the pixel or sub-pixel defined by the corresponding photodetectors 2 and 4.
• the RGB-SPix color sub-pixel of the image sensor 1 is called the part of the image sensor 1 comprising the color photodetector 4 allowing the '' acquisition of light radiation in a restricted part of the visible radiation of the image and the infrared pixel IR-Pix is called the part of the image sensor 1 comprising the infrared photodetector 2 allowing the acquisition of the infrared radiation of the pixel of the image infrared.
• FIG. 1 and 2 There is shown in Figures 1 and 2 three color sub-pixels RGB-SPix and an infrared pixel IR-Pix associated with a pixel of the color and infrared images.
• the color image and the acquired infrared image have the same resolution so that the infrared pixel IR-Pix can also be considered as another sub-pixel of the pixel of the acquired color image.
• the image sensor 1 comprises from bottom to top in figure 2:
• a semiconductor substrate 10 comprising an upper face 12, preferably planar;
• each RGB-SPix color sub-pixel and the IR-Pix infrared pixels can be divided into rows and columns.
• each RGB-SPix color sub-pixel and each infrared IR-Pix pixel has, in a direction perpendicular to the face 12, a square or rectangular base with sides varying from 0.1 ⁇ m to 100 ⁇ m, for example equal to about 3 ⁇ m.
• each SPix subpixel can have a base of a different shape, for example hexagonal.
• the active layer 26 is present only at the level of the infrared pixels IR-Pix of the image sensor 1.
• the active zone of each infrared photodetector 2 corresponds to the zone in which the majority of the radiation
• the incident useful infrared is absorbed and converted into an electrical signal by the infrared photodetector 2 and corresponds substantially to the part of the active layer 26 situated between the lower electrode 22 and the upper electrode 28.
• the active layer 26 is adapted to capture electromagnetic radiation in a range of wavelengths between 400 nm and 1100 nm.
• the infrared photodetectors 2 can be made of organic materials.
• the photodetectors can correspond to organic photodiodes (OPD, standing for Organic Photodiode) or to organic photoresistors. In the remainder of the description, it is considered that the photodetectors 2 correspond to photodiodes.
• the filter 42 is adapted to allow visible light to pass, to allow part of the infrared radiation to pass over the range of infrared wavelengths of interest for the acquisition of the infrared image and to block the rest of the incident radiation and in particular the rest of the infrared radiation outside the wavelength range infrared of interest.
• the range of infrared wavelengths of interest may correspond to a range of 50 nm centered on the expected wavelength of infrared radiation, for example centered on the wavelength of 940 nm or centered on the 850 nm wavelength.
• the filter 42 can be an interference filter and / or include absorbent and / or reflective layers.
• the color filters 34 can correspond to blocks of colored resin. Each color filter 34 is adapted to pass a range of wavelengths of visible light.
• the image sensor may comprise an RGB-SPix color sub-pixel whose color filter 34 is adapted to allow only blue light to pass, for example in the length range. from 430 nm to 490 nm, an RGB-SPix color subpixel whose color filter 34 is adapted to pass only green light, for example in the wavelength range of 510 nm to 570 nm and an RGB-SPix color subpixel whose color filter 34 is adapted to allow only red light to pass, for example in the wavelength range of 600 nm to 720 nm.
• the transparent block 36 is adapted to pass infrared radiation and to pass visible light.
• the transparent block 36 can then correspond to a block of transparent resin.
• the transparent block 36 is adapted to allow infrared radiation to pass and to block visible light.
• the transparent block 36 can then correspond to a block of black resin or to an active layer, having for example a structure similar to that of the active layer 26 and adapted to absorb only the radiation in the target spectrum.
• the active layer 26 only receives the part of the infrared radiation useful in the case where the transparent block 36 is adapted to allow infrared radiation to pass and to block visible light. This advantageously makes it possible to facilitate the design of the active layer 26, the absorption range of which can be extended and in particular include visible light.
• the active layer 26 of the infrared photodiode 2 will capture both infrared radiation and visible light.
• the determination of a signal representative only of the infrared radiation picked up by the infrared photodiode 2 can then be carried out by linear combination of the signal supplied by the infrared photodiode 2 and the color photodiodes 4 of the pixel.
• the semiconductor substrate 10 is made of silicon, preferably of monocrystalline silicon.
• the electronic components 16 comprise transistors, in particular metal-oxide gate field effect transistors, also called MOS transistors.
• Color photodiodes 4 are inorganic photodiodes, preferably made of silicon. Each color photodiode 4 comprises at least the doped silicon region 14 which extends into the substrate 10 from the face 12.
• the substrate 10 is undoped or lightly doped with a first type of conductivity, for example example of type P and each region 14 is a doped region, of the type of conductivity opposite to the substrate 10, for example of type N.
• the depth of each region 14, measured from the face 12, may be between 500 nm and 6 ⁇ m .
• the color photodiode 4 can correspond to a pinched photodiode. Examples of pinched photodiodes are described in particular in US Pat. No. 6,677,656.
• the conductive tracks 20, the conductive vias 24, 30 and the electrodes 22 can be made of a metallic material, for example silver (Ag), aluminum (Al), gold (Au), copper (Cu), nickel (Ni), titanium (Ti) and chromium (Cr).
• the conductive tracks 20, the conductive vias 24, 30 and the electrodes 22 can have a monolayer or multilayer structure.
• Each insulating layer of the stack 18 can be made of an inorganic material, for example of silicon oxide (SiCy) or a silicon nitride (SiN).
• Each electrode 28 is at least partially transparent to the light radiation it receives.
• Each electrode 28 may be of a conductive and transparent material, for example of conductive and transparent oxide or TCO (English acronym for Transparent Conductive Oxide), of carbon nanotubes, of graphene, of a conductive polymer, of a metal, or of a mixture or an alloy of at least two of these compounds.
• TCO Transparent Conductive Oxide
• Each electrode 28 can have a single or multi-layered structure.
• ITO indium-tin oxide
• AZO aluminum-zinc oxide
• GZO gallium-zinc oxide
• TiN titanium nitride
• Molybdenum oxide M0O 3
• tungsten oxide WO 3
• PEDOT PEDOT: PSS, which is a mixture of poly (3, 4) -ethylene-dioxythiophene and of sodium polystyrene sulfonate and polyaniline, also called PAni.
• each electrode 28 examples include silver, aluminum, gold, copper, nickel, titanium and chromium.
• An example of a multilayer structure suitable for embodiment of each electrode 28 is a multilayer structure of AZO and silver of the AZO / Ag / AZO type.
• each electrode 28 may be between 10 nm and 5 ⁇ m, for example of the order of 30 nm. In the case where the electrode 28 is metallic, the thickness of the electrode 28 is less than or equal to 20 nm, preferably less than or equal to 10 nm.
• Each insulating layer 27, 32, 40 can be made of fluoropolymer, in particular the fluoropolymer sold under the name Cytop by the company Bellex, of polyvinylpyrrolidone (PVP), of polymethyl methacrylate (PMMA), of polystyrene ( PS), parylene, polyimide (PI), acrylonitrile butadiene styrene (ABS), poly (ethylene terephthalate) (PET, abbreviation polyethylene terephthalate), poly (ethylene naphthalate) (PEN, English acronym) for polyethylene naphthalate), in cyclic olefin polymers (COP, acronym for Cyclo Olefin Polymer), in polydimethylsiloxane (PDMS), in a photolithography resin, in epoxy resin, in acrylate resin or in a mixture of at least two of these compounds.
• PVP polyvinylpyrrolidone
• PMMA polymethyl methacrylate
• PS polystyren
• each insulating layer 27, 32, 40 can be made of an inorganic dielectric, in particular of silicon nitride, of silicon oxide or of aluminum oxide (Al 2 O 3) .
• Aluminum oxide can be deposited by depositing thin atomic layers (ALD, acronym for Atomic Layer Deposition).
• ALD acronym for Atomic Layer Deposition
• the maximum thickness of each insulating layer 27, 32, 40 can be between 50 nm and 2 ⁇ m, for example of the order of 100 nm.
• the active layer 26 of each infrared IR-Pix pixel can comprise small molecules, oligomers or polymers. They can be organic or inorganic materials, in particular quantum dots.
• the active layer 26 may comprise a semiconductor material ambipolar, or a mixture of an N-type semiconductor material and a P-type semiconductor material, for example in the form of superimposed layers or of an intimate mixture at the nanometric scale so as to form a volume heterojunction .
• the thickness of the active layer 26 may be between 50 nm and 2 ⁇ m, for example of the order of 200 nm
• P-type semiconductor polymers suitable for producing the active layer 26 are poly (3-hexylthiophene) (P3HT), poly [N-9 '-heptadecanyl- 2, 7-carbazole-alt- 5, 5- (4, 7-di-2-thienyl-2 ', l', 3 '- benzothiadiazole)] (PCDTBT), poly [(4, 8-bis- (2-ethylhexyloxy) -benzo [1 , 2-b; 4, 5-b '] dithiophene) -2, 6-diyl- alt- (4- (2-ethylhexanoyl) -thieno [3, 4-b] thiophene)) -2, 6-diyl] (PBDTTT-C), poly [2-methoxy-5- (2-ethyl-hexyloxy) -1, 4-phenylene-vinylene] (MEH-PPV) or poly [2, 6- (4, 4-bis - (2-ethyl
• N-type semiconductor materials suitable for producing the active layer 26 are fullerenes, in particular C60, [6, 6] -phenyl-C 6i- methylbutanoate ([60] PCBM), [6, 6] -phenyl-C 7i methyl butanoate ([70] PCBM), the diimide perylene, zinc oxide (ZnO) or nanocrystals allow the formation of quantum dots (English quantum dots).
• each infrared IR-Pix pixel can be interposed between first and second interface layers, not shown.
• the interface layers facilitate the collection, the injection or the blocking of the charges from the electrodes in the active layer 26.
• the thickness of each interface layer is preferably between 0 , 1 nm and 1 ym.
• the first interface layer helps align the output work of the adjacent electrode with the electronic affinity of the acceptor material used in the active layer 26.
• the first interface layer can be made of cesium carbonate (CSCO3), of metal oxide, in particular of zinc oxide (ZnO), or of a mixture of at least two of these compounds.
• the first interface layer may comprise a self-assembled monomolecular layer or a polymer, for example polyethyleneimine, ethoxylated polyethyleneimine, poly [(9, 9-bis (3 '- (N, N-dimethylamino) propyl) -2, 7 -fluorene) -alt-2, 7- (9, 9-dioctylfluorene)].
• the second interface layer makes it possible to align the output work of the other electrode with the ionization potential of the donor material used in the active layer 26.
• the second interface layer can be made of copper oxide (CuO ), nickel oxide (NiO), vanadium oxide (V 2 O 5 ), magnesium oxide (MgO), tungsten oxide (WO 3 ), molybdenum oxide (M0O3), PEDOT: PSS or in a mixture of at least two of these compounds.
• the microlenses 38 are of micrometric size.
• each RGB-SPix color subpixel and each IR-Pix infrared pixel includes a microlens 38.
• each microlens 38 can be replaced with another type of micrometric-sized optical element, in particular a micrometric-sized Fresnel lens, a micrometric-sized gradient-index lens or a micrometric-sized diffraction grating.
• the microlenses 38 are convergent lenses each having a focal length f of between 1 ⁇ m and 100 ⁇ m, preferably between 1 ⁇ m and 10 ⁇ m. According to one embodiment, all of the microlenses 38 are substantially identical.
• the microlenses 38 can be made of silica, PMMA, a positive photosensitive resin, PET, PEN, COP, PDMS / silicone, or epoxy resin.
• the microlenses 38 can be formed by creeping blocks of a photosensitive resin.
• the microlenses 38 may further be formed by molding on a layer of PET, PEN, COP, PDMS / silicone or epoxy resin.
• the layer 40 is a layer which follows the shape of the microlenses 38.
• the layer 40 can be obtained from an optically transparent adhesive (OCA, acronym for Optically Clear Adhesive), in particular a liquid optically transparent adhesive (LOCA, acronym for Liquid Optically Clear Adhesive), or a material with a low refractive index, or an epoxy / acrylate glue, or a film of a gas or a gas mixture, for example of l 'air.
• OCA optically transparent adhesive
• LOCA liquid optically transparent adhesive
• the layer 40 is of a material having a low refractive index, lower than that of the material of the microlenses 38.
• the layer 40 may be of a filling material which is a transparent non-adhesive material.
• the layer 40 corresponds to a film which is applied against the array of microlenses 38, for example an OCA film.
• the contact zone between the layer 40 and the microlenses 38 can be reduced, for example limited to the tops of the microlenses.
• the layer 40 can then be composed of a material having a higher refractive index than in the case where the layer 40 conforms to the microlenses 38.
• the layer 40 corresponds to an OCA film which is applied against. the array of microlenses 38, the adhesive having properties which allow the film 40 to completely or substantially completely conform to the surface of the microlenses.
• the method of forming at least some layers of the image sensor 1 may correspond to a so-called additive method, for example by direct printing of the material composing the organic layers at the desired locations, in particular in the form of a sol-gel, for example by inkjet printing, heliography, screen printing, flexography, spray coating (in English spray coating) or deposit of drops (in English drop-casting).
• the process for forming the layers of the image sensor 1 may correspond to a so-called subtractive process, in which the material composing the organic layers is deposited on the entire structure and in which the unused portions are then removed, for example by photolithography or laser ablation.
• the layers may in particular be processes of the spin coating, spray coating, heliography, slot-die coating, blade coating, flexography or screen printing type.
• the layers are metallic, the metal is, for example, deposited by evaporation or by cathodic sputtering on the whole of the support and the metallic layers are delimited by etching.
• the layers of the image sensor 1 can be produced by printing techniques.
• the materials of these layers described above can be deposited in liquid form, for example in the form of conductive and semiconductor inks using inkjet printers.
• the term “materials in liquid form” is understood here also to mean gel materials which can be deposited by printing techniques.
• Annealing steps are optionally provided between the depositions of the different layers, but the annealing temperatures may not exceed 150 ° C., and the deposition and any annealing may be carried out at atmospheric pressure.
• the electrode 28 can extend over all the RGB-SPix color sub-pixels and over the infrared IR pixel.
• the -Pix and via 30 is provided in areas that do not correspond to sub-pixels, for example at the periphery of the pixel.
• the electrode 28 may be common to all of the pixels of a same row and / or to all of the pixels of the image sensor.
• the via 30 may be provided at the periphery of the image sensor 1.
• the electrode 28 may extend only over the active layer 26 and the via 30 may be provided at the level of the. IR-Pix infrared pixel.
• Figures 3 and 4 are figures of another embodiment of an image sensor 50 respectively similar to Figures 1 and 2.
• the image sensor 50 comprises all the elements of the image sensor 1 shown in Figures 1 and 2 with the difference that the insulating layer 32 is interposed between the microlenses 38 and the color filters 34, that the active layer 26 is arranged in place of the block 36 which is not present, that is to say at the same level as the color filters 34, and that the insulating layer 27 is not present.
• the electrode 28 extends only over the active layer 26 and the via 30 is provided at the level of the infrared pixel IR-Pix. In this case, the active layer 26 of the infrared photodiode 2 will capture both infrared radiation and visible light.
• the determination of a signal representative only of the infrared radiation picked up by the infrared photodiode 2 can then be carried out by linear combination of the signal supplied by the infrared photodiode 2 and the color photodiodes 4 of the pixel.
• FIG. 5 represents the simplified electrical diagram of an embodiment of the read circuits 6_R, 6_G, 6_B, associated with the color photodiode 4 of color sub-pixels.
• the read circuits 6_R, 6_G, 6_B and 6_IR have similar structures.
• the suffix "_R” is added to the reference designating a component of the read circuit 6_R
• the suffix "_G” to the reference designating the same component of the read circuit 6_G
• the suffix "_B” to the reference designating the same component of the read circuit 6_B
• the suffix "_IR” to the reference designating the same component for the read circuit 6_IR.
• Each read circuit 6_R, 6_G, 6_B, 6_IR comprises a MOS transistor in 60_R, 60_G, 60_B, 60_IR follower assembly, in series with a selection MOS transistor 62_R, 62_G, 62_B, 62_IR between a first terminal 64_R, 64_G, 64_B, 64_IR and a second terminal 66_R, 66_G, 66_B, 66_IR. Terminal 64_R, 64_G,
• 64_B, 64_IR is connected to a source of a high reference potential VDD in the case where the transistors making up the read circuit are N-channel MOS transistors, or of a low reference potential, for example ground, in the case where the transistors making up the read circuit are P-channel MOS transistors.
• Terminal 66_R, 66_G, 66_B, 66_IR is connected to a conductive track 68.
• the conductive track 68 can be connected to all the color sub-pixels and all the infrared pixels of the same column and be connected to a current source 69 which is not part of the read circuits 6_R, 6_G, 6_B, 6_IR.
• the gate of transistor 62_R, 62_G, 62_B, 62_IR is intended to receive a signal SEL_R, SEL_G, SEL_B, SEL_IR for selecting the color sub-pixel / infrared pixel.
• the gate of transistor 60_R, 60_G, 60_B and 60_IR is connected to a node FD_R, FD_G, FD_B, FR_IR.
• the FD_R, FD_G, FD_B, FR_IR node is connected, by a MOS 70 R, 70 G, 70 B, 70 IR reset transistor, to a terminal application of a reset potential Vrst_R, Vrst_G, Vrst_B, Vrst_IR, this potential possibly being VDD.
• the gate of transistor 70_R, 70_G, 70_B, 70_IR is intended to receive a signal RST_R, RST_G, RST_B, RST_IR to reset the color sub-pixel / infrared pixel, making it possible in particular to reset the node FD substantially to the potential Vrst.
• the node FD_R, FD_G, FD_B is connected to the cathode electrode of the color photodiode 4 of the color sub-pixel.
• the anode electrode of the color photodiode 4 is connected to a source of a low reference potential GND, for example ground.
• the FD_IR node is connected to the cathode electrode 22 of the infrared photodiode 2.
• the anode electrode 28 of the infrared photodiode 4 is connected to a source of a reference potential V_IR.
• a capacitor not shown, can be provided, one electrode of which is connected to the node FD_R, FD_G, FD_B, FD_IR and the other electrode of which is connected to the source of the low reference potential GND.
• the role of this capacitor can be fulfilled by the parasitic capacitances present at the node FD_R, FD_G, FD_B, FD_IR.
• the signals SEL_R, SEL_G, SEL_B, RST_R, RST_G, RST_B can be transmitted to all the color sub-pixels of the row.
• the signals SEL_IR, RST_IRB and the potential V_IR can be transmitted to all the infrared pixels of the row.
• the signals Vrst_R, Vrst_G, Vrst_B, Vrst_IR can be identical or different.
• the signals Vrst_R, Vrst_G, Vrst_B are identical and the signal Vrst_IR is different from the signals Vrst_R, Vrst_G, Vrst_B.
• FIG. 6 is a timing diagram of the binary signals RST IR, SEL IR, RST R, SEL R, RST G, SEL G, RST B, SEL B and of the potential V_IR during an embodiment of a method of operating the read circuits 6_R, 6_G,
• 6_B, 6_IR represented in FIG. 5.
• t0 to t10 successive instants of an operating cycle.
• the timing diagram was established by considering that the MOS transistors of the read circuits 6_R, 6_G, 6_B, 6_IR are N channel transistors.
• the signals SEL_IR, SEL_R, SEL_G and SEL_B are in the low state so that the selection transistors 62_IR, 62_R, 62_G and 62_B are blocked.
• the cycle includes a phase of reinitializing the infrared pixel and the color sub-pixel associated with the red color.
• the signals RST_IR and RST_R are high so that the reset transistors 70_IR and 70_R are on.
• the charges accumulated in the infrared photodiode 2 are then discharged to the source of the potential Vrst_IR and the charges accumulated in the color photodiode 4 of the color sub-pixel associated with the red color are then discharged to the source of the potential Vrst_R.
• V_IR is set to a low level.
• signal RST_IR is set low so that transistor 70_IR is off and signal RST_R is set low so that transistor 70_R is blocked.
• An integration phase then begins for infrared photodiode 2 during which charges are generated and collected in photodiode 2 and for photodiode 4 of the color sub-pixel associated with the color red during which charges are generated and collected in the photodiode. 4.
• the signal RST_G is set low so that the transistor 70_G is blocked.
• An integration phase then begins for the photodiode 4 of the color sub-pixel associated with the green color during which charges are generated and collected in photodiode 4.
• signal RST_B is set low so that transistor 70_B is off.
• An integration phase then begins for the photodiode 4 of the color sub-pixel associated with the blue color during which charges are generated and collected in the photodiode 4.
• the potential V_IR is set to a high level, which stops the collection of charges in the infrared photodiode.
• the integration phase of the infrared photodiode 2 therefore stops.
• the signal SEL_R is temporarily placed in a high state, so that the potential of the conductive track 68 reaches a value representative of the voltage at the FD_R node and therefore of the quantity of charges stored in the photodiode 4 of the color sub-pixel associated with the color red.
• the integration phase of the photodiode 4 of the color subpixel associated with the red color therefore extends from the instant t1 to the instant t5.
• the signal SEL_G is temporarily set to a high state, so that the potential of the conductive track 68 reaches a value representative of the voltage at the node FD_G and therefore of the quantity of charges stored in the photodiode 4 of the color sub-pixel associated with the color green.
• the integration phase of the photodiode 4 of the color sub-pixel associated with the color green therefore extends from the instant t2 to the instant t6.
• the signal SEL_B is temporarily set to a high state, so that the potential of the conductive track 68 reaches a value representative of the voltage at the node FD_B and therefore of the quantity of charges stored in the photodiode 4 of the color sub-pixel associated with the color blue.
• the integration phase of the photodiode 4 of the color sub-pixel associated with the blue color therefore extends from the instant t3 to the instant t7.
• the signal SEL_IR is temporarily set to a high state, so that the potential of the conductive track 68 reaches a value representative of the voltage at the FD_IR node and therefore of the quantity of charges stored in the infrared photodiode 2.
• the signals RST_IR and RST_R are set high. The instant t10 marks the end of the cycle and corresponds to the instant tl of the following cycle.
• the integration phases of the color photodiodes of the sub-pixels associated with the same pixel of the color image to be acquired are shifted in time.
• the integration phase of the infrared photodiode 2 is controlled by the V-IR signal
• the present embodiment advantageously makes it possible to carry out a reading method of the Global Shutter type for the acquisition of the image. infrared, in which the integration phases of all the infrared photodiodes are carried out simultaneously.
• the infrared photodiode 4 can absorb near infrared radiation and also visible light. In this case, to determine the quantity of charges generated during an integration phase of the infrared photodiode due only to infrared radiation, it can be subtracted from the signal supplied by the infrared photodiode 2, the signals supplied by the color photodiodes 4 of the sub - pixels associated with the same image pixel. However, it is then preferable that the integration phases of the color sub-pixels are simultaneous with the integration phase of the infrared photodiode 2.
• Each read circuit 6_R, 6_G, 6_B, 6_IR, shown in FIG. 5, can then further comprise a transistor Transfer MOS between the node FD_R, FR_G, FD_B, FD_IR and the cathode electrode of photodiode 4, 2.
• the transfer transistor controls the start and end of the integration phase of the color photodiodes so that A Global Shutter type reading method for acquiring the color image can be implemented.
• a transfer MOS transistor between the node FD_R, FR_G, FD_B, FD_IR and the cathode electrode of the photodiode 4, 2, it can be provided a method of reading in which a reading of a first value VI representative of the potential of the node FD_R, FD_G, FD_B, FD_IR can be carried out just after the closing of the reset transistor 70_R, 70_G, 70_B, 70_IR and a reading of a second value V2 representative of the potential of the node FD_R, FD_G, FD_B, FD_IR can be realized just after the closing of the transfer transistor.
• the difference between the values V2 and VI is representative of the quantity of charges stored in the photodiode while suppressing the thermal noise due to the reset transistor 70_R, 70_G, 70_B, 70_IR.

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• 2019
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