Image sensor

Abstract

Image Sensor This description relates to an image sensor (100) comprising a plurality of organic photodetectors (OPDs) formed on a substrate (101) transparent to radiation of interest to the organic photodetectors, each organic photodetector having an active region whose flanks are coated with a region opaque (109) to the radiation of interest of the organic photodetector. Figure for the abstract: Fig. 1

Description

Title of the invention: Image sensor Technical field

[0001] The present description relates generally to electronic devices, and more particularly to image sensors. Prior art

[0002] Image sensors suitable for forming an image of a scene have been proposed. Among these sensors, there are in particular so-called "semi-transparent" image sensors comprising a plurality of photodetectors formed on a substrate transparent to visible light, the radiation of interest of the photodetectors being able to be located outside the visible range, for example in the near infrared.

[0003] However, existing image sensors have various drawbacks. In particular, the operation of existing semi-transparent image sensors comprising a plurality of photodetectors formed on a substrate transparent to visible light is affected by stray radiation from the side of a rear face of the image sensor. Summary of the invention

[0004] There is a need to improve existing image sensors. In particular, it would be desirable to overcome all or part of the disadvantages of existing semi-transparent image sensors comprising a plurality of photodetectors formed on a substrate transparent to visible light.

[0005] For this, one embodiment provides an image sensor comprising a plurality of organic photodetectors formed on a substrate transparent to a radiation of interest from the organic photodetectors, each organic photodetector comprising an active region whose sides are coated with a region opaque to the radiation of interest from the organic photodetector.

[0006] According to one embodiment, the opaque region has, in top view, an annular shape surrounding the active region.

[0007] According to one embodiment, the opaque region is located on and in contact with the sides of the active region.

[0008] According to one embodiment, each organic photodetector further comprises an insulating layer interposed between the sides of the active region and the opaque region.

[0009] According to one embodiment, the opaque region comprises first parts covering the sides of the active region and a second part extending over an upper face of the active region.

[0010] According to one embodiment, the first parts of the opaque region have each having a width strictly greater, preferably at least five times greater, more preferably at least ten times greater, than a thickness of the second part of the opaque region.

[0011] According to one embodiment, the sensor further comprises, for each organic photodetector, an optical filter located directly above the active region of the organic photodetector.

[0012] According to one embodiment, the active region is located on and in contact with a lower electrode of the organic photodetector.

[0013] According to one embodiment, each organic photodetector comprises an active stack comprising the active region interposed between an electron injection layer and a hole injection layer, the hole injection layer being common to all the organic photodetectors of the sensor.

[0014] According to one embodiment, the substrate is further transparent to visible light.

[0015] According to one embodiment, the region opaque to the radiation of interest of the photo organic detector is furthermore opaque to visible light.

[0016] According to one embodiment, the active region is adapted to detect near infrared radiation.

[0017] One embodiment provides a method of manufacturing an image sensor comprising the following steps: (a) provide a substrate; and b) forming, on the substrate, a plurality of organic photodetectors, each organic photodetector comprising an active region whose walls are coated with a region opaque to the radiation of interest of the organic photodetector, in which the substrate is transparent to radiation of interest from organic photodetectors.

[0018] According to one embodiment, the active region is produced before the opaque region.

[0019] According to one embodiment, the active region is produced after the opaque region. Brief description of the drawings

[0020] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0021] [Fig.l] is a schematic and partial sectional view of an image sensor according to one embodiment;

[0022] [Fig.2A], [Fig.2B], [Fig.2C] and [Fig.2D] illustrate, by means of top views and sectional views, schematic and partial, successive steps of a method of manufacturing the image sensor of [Fig.1] according to one embodiment;

[0023] [Fig.3A], [Fig.3B], [Fig.3C], [Fig.3D], [Fig.3E] and [Fig.3F] illustrate, by top views and sectional views, schematic and partial, of the successive steps of a method of manufacturing an image sensor according to one embodiment; and

[0024] [Fig.4A], [Fig.4B] and [Fig.4C] illustrate, by a top view and schematic and partial sectional views, successive steps of a variant of the manufacturing method of the image sensor of FIGS. 3A to 3F. Description of the embodiments

[0025] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0026] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the applications of the described image sensors have not been detailed, the described embodiments being compatible with all or most of the usual applications of image sensors, possibly subject to adaptations within the scope of the person skilled in the art upon reading this description.

[0027] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0028] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0029] Unless otherwise specified, the expressions “about”, “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably to within 5%.

[0030] In the following description, the terms “insulator” and “conductor” mean respectively, unless otherwise specified, electrically insulating and electrically conductive.

[0031] The expression "transmittance of a layer" designates a ratio between an intensity of radiation leaving the layer and an intensity of radiation entering the layer. In the remainder of the description, a layer is said to be opaque to radiation when its transmittance is, for this radiation, strictly less than 40%, of preferably less than or equal to 25%, more preferably less than or equal to 10%. Furthermore, a layer is said to be transparent to radiation when its transmittance is, for this radiation, greater than or equal to 40%, preferably greater than or equal to 75%, more preferably greater than or equal to 90%. The definition of the qualifiers opaque and transparent above is not limited to the case of a layer, but applies more generally to any element likely to be exposed to radiation, for example a substrate, a region, a stack of several layers, etc.

[0032] Furthermore, the expression “radiation of interest” designates, in the description which follows, radiation having a wavelength corresponding substantially to a maximum absorption peak of a photosensitive element, for example a photodetector or an image sensor pixel.

[0033] A pixel of an image corresponds to the unit element of the image captured by an image sensor. When the sensor is a color image sensor, it generally comprises, for each pixel of the color image to be acquired, at least three components. These three components each acquire light radiation substantially in a single color, that is to say in a wavelength range of less than 100 nm (for example, red, green and blue). Each component may comprise at least one photodetector.

[0034] In the present description, the expression "active region" designates a region from which the majority of electromagnetic radiation received by an optoelectronic component is captured. In the remainder of the description, an optoelectronic component, in particular a photodetector or an image sensor pixel, is said to be organic when the active region of the optoelectronic component is predominantly, preferably entirely, made of at least one organic material or a mixture of organic materials.

[0035] In the present description, the expression "visible light" designates electromagnetic radiation whose wavelength is between 400 nm and 700 nm and the expression "infrared radiation" designates electromagnetic radiation whose wavelength is between 700 nm and 1 mm. In the infrared range, near infrared radiation has a wavelength between 700 nm and 1.7 pm.

[0036] [Fig.l] is a schematic and partial sectional view of an image sensor 100 according to one embodiment.

[0037] In the example shown, the image sensor 100 comprises a plurality of pixels PIX formed in and on a substrate 101. The substrate 101 is for example transparent to visible light. For example, the substrate 101 is made of glass.

[0038] In the illustrated example, control transistors 103 of the pixels PIX are formed in the substrate 101. Each control transistor 103 comprises, for example, two separate semiconductor regions 103S and 103D flush with a face 101T of the substrate 101 (the upper face of the substrate 101, in the orientation of [Fig.l]) corresponding to an illumination face of the image sensor 100. Each control transistor 103 further comprises, in this example, a semiconductor region 103G located directly above the semiconductor regions 103S and 103D and separate from the regions 103S and 103D. The regions 103S, 103D and 103G are, for example, respectively source, drain and gate regions of the control transistor 103.

[0039] For the sake of readability, only two PIX pixels have been shown in [Fig.l]. However, the image sensor 100 may of course comprise a number of PIX pixels greater than two, for example several thousand or several million PIX pixels. For example, the PIX pixels of the image sensor 100 may be organized in the form of a matrix, the PIX pixels being for example then arranged regularly, at a substantially constant pitch, according to rows and columns.

[0040] In the example illustrated in [Fig.l], each pixel PIX of the image sensor 100 further comprises an organic photodetector (OPD) formed on the substrate 101. Each organic photodetector OPD is for example sensitive to near infrared radiation. The substrate 101 is for example transparent to the radiation of interest of the organic photodetectors OPD, for example transparent to the near infrared.

[0041] In the example shown, each organic photodetector OPD comprises a conductive region 105 extending laterally over and in contact with a portion of the face of the semiconductor region 103D flush with the face 101T of the substrate 101 (the upper face of the semiconductor region 103D, in the orientation of [Fig. 1]). In the example shown, the conductive region 105 further extends laterally over and in contact with a portion of the face 101T of the substrate 101. This example is however not limiting, the conductive region 105 being able, as a variant, to extend over and in contact with the entire upper face of the region 103D and / or not to extend over and in contact with the face 101T of the substrate 101.

[0042] The conductive region 105 constitutes for example a lower electrode of the OPD photodetector. For example, the conductive region 105 is made of a conductive oxide, for example tungsten oxide (WO3), nickel oxide (NiO), vanadium oxide (V2O5) or molybdenum oxide (MoO3). The conductive region 105 is for example more precisely made of a conductive and transparent oxide (“Transparent Conductive Oxide” - TCO, in English), for example indium-tin oxide (“Indium Tin Oxide” - ITO, in English), aluminum-zinc oxide (“Aluminum Zinc Oxide” - AZO, in English) or gallium-zinc oxide (“Gallium Zinc Oxide” - GZO, in English). Alternatively, the conductive region 105 is made of a metal, for example selected from silver, aluminum, gold, copper, nickel, titanium, chromium, tungsten, lead, palladium, molybdenum, magnesium and platinum, or of a metal alloy, for example an alloy of at least two of the aforementioned metals, for example an alloy of magnesium and silver (MgAg). Alternatively, the conductive region 105 is made of a nitride, for example a nitride of at least one of the aforementioned metals, for example titanium nitride (TiN). Furthermore, the conductive region 105 may have a single-layer or multi-layer structure, for example an ITO / Ag / ITO, AZO / Ag / AZO, or ZnO / Ag / ZnO multi-layer structure.

[0043] In the example shown, each OPD photodetector further comprises an active stack 107, for example an active diode stack, located on and in contact with a portion of the face of the conductive region 105 opposite the face 101T of the substrate 101 (the upper face of the conductive region 105, in the orientation of [Fig. 1]). Although this has not been detailed in [Fig. 1], the active stack 107 comprises, for example, in order from the conductive region 105, an electron injection layer (EIL), an active region or layer, and a hole injection layer (HIL). For example, the electron injection layer is located on and in contact with the conductive region 105, the active region is located on and in contact with the electron injection layer, and the hole injection layer is located on and in contact with the active region.

[0044] For example, the electron injection layer is made of: - a metal oxide, for example a titanium oxide or a zinc oxide; - a molecular host / dopant system, for example one of the products marketed by the company Novaled under the names NET-5 / NDN-1 or NET-8 / MDN-26; - a doped conductive or semiconductive polymer chosen for example from the polymer PEDOT:Tosylate, which is a mixture of poly(3,4)-ethylenedioxythiophene and tosylate, polyethyleneimine (PEI) or an ethoxylated, propoxylated and / or butoxylated polyethyleneimine (PEIE); - a carbonate, for example caesium carbonate (CsCO3); - a polyelectrolyte, for example poly[9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene-alt-2,7-(9,9-dioctyfluorene)] (PFN), poly[3-(6-trimethylammoniumhexyl)thiophene] (P3TMAHT) or poly[9,9-bis(2-ethylhexyl)fluorene]-b-poly[3-(6-trimethylammoniumhexyl]thiophene (PF2 / 6-b-P3TMAHT); or - a mixture of at least two of these materials.

[0045] The electron injection layer has, for example, a thickness of the order of a few nanometers, for example between 2 and 10 nm, in the case where the layer is made of a polymer such as PEI or PEIE, or a few tens of nanometers, in the case where the layer is made of a metal oxide.

[0046] By way of example, the active region and the electron injection layer of each organic photodetector OPD form a stack having a thickness of the order of several hundred nanometers, for example between 200 nm and 1 μm.

[0047] The active region of each OPD photodetector is for example adapted to detect near infrared radiation. The active region has for example a thickness of the order of several hundred nanometers, for example between 300 and 600 nm, for example equal to approximately 350 nm. By way of example, the active region may comprise small molecules, oligomers or polymers. These may be organic or inorganic materials, in particular quantum dots. The active region may comprise an ambipolar semiconductor material, or a mixture of an N-type semiconductor material and a P-type semiconductor material, for example in the form of superimposed layers or an intimate mixture at the nanometric scale so as to form a bulk heterojunction.

[0048] Examples of P-type semiconductor polymers suitable for producing the active region of OPD organic photodetectors are poly(3-hexylthiophene) (P3HT), poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2',l',3'-benzothiadiazo le)] (PCDTBT), poly[(4,8-bis-(2-ethylhexyloxy)-benzo[l,2-b;4,5-b'] di-thiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b] thiophene))-2,6-diyl] (PBDTTT-C), poly[2-methoxy-5-(2-ethyl-hexyloxy)-l,4-phenylene-vinylene] (MEH-PPV) or poly[2,6-(4,4-bis-(2-ethylhexyl)-4 / / -cyclopenta [2,1-Z?;3,4-Z? ']dithiophene)-aZt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT).

[0049] Examples of N-type semiconductor materials suitable for producing the active region are fullerenes, including C60, [6,6]-phenyl-C6i-methyl butanoate (

[60] PCBM), [6,6]-phenyl-C7i-methyl butanoate (

[70] PCBM), perylene diimide, zinc oxide (ZnO), nanocrystals for forming quantum dots, or small non-fullerene molecules (Non-Fullerene Acceptor - NFA), for example Y5 (2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro[l,2,5]thiadiazo lo[3,4e]thieno[2' ' ,3”:4',5'] thieno[2',3':4.5]pyrrolo[3,2-g] thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(3-oxo-2,3-dih ydro 1 H-indene-2,1 -diylidene))dimalononitrile).

[0050] The hole injection layer has, for example, a thickness of the order of one or several hundred nanometers, for example between 80 nm and 1 μm, for example equal to approximately 100 nm. By way of example, the hole injection layer is made of a material transparent to the radiation it receives. The hole injection layer can be made of: - a doped conductive or semiconductive polymer, for example the material marketed by the company Sigma-Aldrich under the name “Plexcore OC RG-1100” or “Plexcore OC RG-1200”, the polymer PEDOT:PSS or a polyaniline; - a molecular host / dopant system, for example the product marketed by the company Novaled under the name NHT-5 / NDP-2 or NHT-18 / NDP-9; - a polyelectrolyte, for example Nafion; - a metal oxide, for example a molybdenum oxide, a vanadium oxide, ITO, or a nickel oxide; or - a mixture of two or more of these materials.

[0051] The hole injection layer may have a single-layer or multi-layer structure, for example a MoOx / Ag or MoOx / ITO structure.

[0052] Examples of transparent conductive oxides suitable for producing the hole injection layer are indium tin oxide (ITO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), titanium nitride (TiN), molybdenum oxide (MoO3) and tungsten oxide (WO3). An example of a conductive polymer suitable for producing the hole injection layer is the polymer known as PEDOT:PSS, which is a mixture of poly(3,4)-ethylenedioxythiophene and sodium polystyrene sulfonate and polyaniline, also called PAni. An example of a multilayer structure suitable for the realization of the hole injection layer is a multilayer structure of AZO and silver of the AZO / Ag / AZO type.

[0053] Although this has not been shown, an electron transport layer (ETL), interposed between the electron injection layer and the active region, and / or a hole transport layer (HTL), interposed between the active region and the hole injection layer, may further be provided in the active stack 107 of each organic photodetector OPD.

[0054] According to one embodiment, each organic photodetector OPD of the image sensor 100 further comprises a region 109 coating the flanks, or side walls, of the active region of the photodetector. The flanks of the active region of the photodetector are preferably fully coated with the region 109. In the example shown, the region 109 fully coats the flanks of the active stack 107 of the OPD photodetector. Each region 109, symbolized by two hatched rectangles located on either side of the active stack 107 of one of the organic photodetectors OPD, is opaque to the radiation of interest from the photodetector. Each region 109 is by example further opaque to visible light. In the example illustrated, the opaque region 109 has a height, or thickness, substantially equal to that of the active stack 107 of the OPD photodetector whose sides it covers. This example is however not limiting, the opaque region 109 being able, as a variant, to have a height, or thickness, strictly greater than that of the active stack 107. In the example shown, the opaque region 109 of each organic OPD photodetector is located on and in contact with a part of the face of the conductive region 105 opposite the substrate 101 (the upper face of the conductive region 105, in the orientation of [Fig.l]).

[0055] In the example illustrated in [Fig.l], the side walls, or flanks, of the opaque region 109 are aligned vertically relative to the side walls, or flanks, of the underlying conductive region 105. This example is however not limiting, the flanks of the opaque region 109 being able, as a variant, to be offset laterally relative to the vertical alignment of the flanks of the conductive region 105. In this case, the opaque region 109 can: be entirely located on and in contact with the conductive region 105; or extend laterally on and in contact with a portion of the face 101T of the substrate 101, the opaque region 109 being, in this case, located on and in contact with the sides of the conductive region 105.

[0056] The opaque region 109 of each OPD photodetector has, for example, a height, or thickness, of between 500 nm and 2 μm, for example equal to approximately 1 μm. Furthermore, the opaque region 109 has, for example, a width of between a few nanometers and a few tens of nanometers, for example equal to approximately 10 nm. By way of example, the opaque region 109 is made of a colored resin, for example a colored or black SU-8 resin. The opaque region 109 is, for example, made of a black resin absorbing in the visible and near infrared ranges.

[0057] In the example shown, the image sensor 100 further comprises an insulating layer 111 coating the side walls, or flanks, of the organic photodetectors OPD and the face of the organic photodetectors OPD opposite the substrate 101 (the upper face of the organic photodetectors OPD, in the orientation of [Fig.l]). More specifically, in the example shown, the insulating layer 111 is located on and in contact with: portions of the face 101T of the substrate 101 not coated with the insulating layers 105 and the opaque regions 109, in the case where the opaque regions 109 extend laterally on and in contact with the face 101T of the substrate 101; the sides of the conductive regions 105, in the case where the opaque regions 109 do not extend laterally on and in contact with the face 101T of the substrate 101; the flanks of the opaque regions 109; and the faces of the opaque regions 109 and the active stacks 107 opposite the substrate 101 (the upper faces of the opaque regions 109 and the active stacks 107, in the orientation of [Fig.l]).

[0058] The insulating layer 111 is for example transparent to the radiation of interest from the organic photodetectors OPD of the image sensor 100. By way of example, the insulating layer 111 is made of an epoxy glue, an organic dielectric, polystyrene, an acrylate resin, a resin known under the trade name SU8 or a combination of at least two of these materials.

[0059] In the example illustrated, each pixel PIX further comprises an optical filter 113 surmounting the underlying organic photodetector OPD. In the example shown, each optical filter 113 is more precisely located directly above the active stack 107 and the opaque region 109 of one of the organic photodetectors OPD. The sides of each optical filter 113 are for example, as illustrated in [Fig.l], substantially aligned vertically with respect to the sides of the opaque region 109 of the underlying organic photodetector OPD. In this case, the optical filter 113 is substantially centered laterally with respect to the underlying organic photodetector OPD and has, in top view, a surface area substantially equal to the sum of the surfaces of the active stack 107 and the opaque region 109 of the photodetector.This example is however not limiting, the flanks of each optical filter 113 may, as a variant, not be aligned vertically with respect to the flanks of the opaque region 109 of the underlying organic photodetector OPD. In this case, the optical filter 113 is for example laterally off-center with respect to the underlying organic photodetector OPD and / or has, in top view, a surface strictly greater than the sum of the surfaces of the active stack 107 and the opaque region 109 of the photodetector. Preferably, each optical filter 113 extends laterally beyond the vertical line of the underlying active stack 107. This allows optimal filtering of the incident radiation.

[0060] In the example shown, each optical filter 113 is separated from the underlying organic photodetector OPD by a portion of the insulating layer 111. This example is however not limiting, each optical filter 113 being able, as a variant, to be located on and in contact with the underlying opaque region 109 and with the underlying active stack 107, in the case where the active stack 107 and the opaque region 109 have substantially identical thicknesses.

[0061] The optical filters 113 transmit mainly the radiation of interest from the underlying organic photodetector OPD and absorb the other radiation. For example, each optical filter 113 is a filter absorbing visible light and transmitting infrared radiation (“IR pass filter”, in English), for example in a case where the image sensor 100 is an infrared sensor. As a variant, each optical filter 113 is for example a color filter, for example in a case where the image sensor 100 is a color image sensor.

[0062] An advantage of the image sensor 100 lies in the fact that the presence of the opaque regions 109 covering the active regions of the organic photodetectors OPD makes it possible to avoid, or limit, the fact that parasitic radiation, coming from the side of a face of the substrate 101 opposite the face 101T (the lower face of the substrate 101, in the orientation of [Fig. 1]), does not disturb the operation of the organic photodetectors OPD of the image sensor 100. The parasitic radiation, which does not pass through the optical filters 113, comprises for example infrared radiation and / or visible light. In particular, the opaque regions 109 advantageously make it possible to avoid, or limit, phenomena of photogeneration of undesirable charges in the active region of the organic photodetectors OPD during exposure phases of the image sensor 100.The image sensor 100 has, for example, a signal-to-noise ratio higher than that of an image sensor lacking the opaque regions 109.

[0063] [Fig.2A], [Fig.2B], [Fig.2C] and [Fig.2D] illustrate, by means of top views and sectional views, schematic and partial, successive steps of a method for manufacturing the image sensor 100 of [Fig.1] according to one embodiment. In this method, the opaque region 109 of each organic photodetector OPD is formed prior to the production of the active stack 107.

[0064] Figures 2A and 2B illustrate more precisely, respectively by a top view and a sectional view along plane BB of [Fig.2A], a structure obtained at the end of a step of forming the opaque regions 109.

[0065] By way of example, a layer of the material intended to form the opaque regions 109 is deposited on the side of the face 101T of the substrate 101, the layer thus coating the upper and lateral faces of the conductive regions 105 and the parts of the face 101T of the substrate 101 not coated with the conductive regions 105. The layer is for example then structured, for example by photolithography, so as to retain only the opaque regions 109. The photolithography step may be followed by an etching step, for example in a case where the layer of the material intended to form the opaque regions 109 is not photosensitive.

[0066] In the example shown, each opaque region 109 has, in top view, a rectangular annular shape. This example is however not limiting, each opaque region 109 being able, as a variant, to have, in top view, any annular shape, for example oval, circular, square, etc. The opaque region 109 has, for example, a periphery of a shape substantially identical to that of the underlying conductive region 105.

[0067] In the illustrated example, a conductive track 203G interconnects the regions 103G control transistors 103 of the PIX pixels of the same row. The conductive tracks 203G are for example parallel to each other and isolated from each other. In this example, a conductive track 203S interconnects the regions 103S of the control transistors 103 of the PIX pixels of the same column. The conductive tracks 203S are for example parallel to each other and isolated from each other. By way of example, the conductive tracks 203S are substantially orthogonal to the conductive tracks 203G and isolated from the conductive tracks 203G.

[0068] Although this has not been detailed in the figures, the conductive tracks 203G and 203S are for example connected respectively to control and reading circuits of the image sensor 100. The control and reading circuits of the image sensor 100 are for example adapted to implement successive steps of resetting, exposure and acquisition. The production of these circuits and the implementation of these steps is within the ability of a person skilled in the art from the indications of the present description.

[0069] Figures 2C and 2D illustrate more precisely, respectively by a top view and a sectional view along plane BB of [Fig.2C], a structure obtained at the end of a step of forming the active stacks 107.

[0070] By way of example, first, second and third layers, intended respectively to form the electron injection layer, the active region and the hole injection layer, are successively deposited on the side of the face 101T of the substrate 101 during this step. The stack consisting of the first, second and third layers is for example then structured, for example by photolithography then etching, so as to keep parts of the first, second and third layers surrounded, or bordered, by the opaque regions 109. These parts of the first, second and third layers are intended to form the active stacks 107 of the organic photodetectors OPD of the image sensor 100.

[0071] In the example shown, parts of the first, second and third layers extending laterally outside the spaces delimited by the opaque regions 109 are furthermore preserved at the end of the structuring. In the example illustrated in [Fig.2C], these parts of the first, second and third layers form, in top view, a grid connecting all the active stacks 107 together. This makes it possible, for example, to form an upper electrode common to all the active stacks 107 of the image sensor 100, the common upper electrode corresponding in this case to the third layer of the stack, that is to say to the layer intended to form the hole injection layers of the organic photodetectors OPD.

[0072] Although this has not been illustrated, the insulating layer 111 is for example then deposited on the side of the face 101T of the substrate 101, then the optical filters 113 are produced. By way of example, the optical filters 113 are formed by depositing a layer on the side of the face 101T of the substrate 101 then structuring of the layer, for example by photolithography. The photolithography step can be followed by an etching step, for example in a case where the layer of the material intended to form the optical filters 113 is not photosensitive. A structure identical or similar to that illustrated in [Fig.l] is thus obtained.

[0073] [Fig.3A], [Fig.3B], [Fig.3C], [Fig.3D], [Fig.3E] and [Fig.3F] illustrate, by means of top views and sectional views, schematic and partial, successive steps of a method of manufacturing an image sensor 300 according to one embodiment. The method of manufacturing the image sensor 300 described below in relation to FIGS. 3A to 3F differs for example from the method of manufacturing the image sensor 100 mainly in that, in the case of the image sensor 300, the opaque regions 109 are formed after the active stacks 107.

[0074] Figures 3A and 3B illustrate more precisely, respectively by a top view and a sectional view along plane BB of [Fig.3A], a structure obtained at the end of a step of forming the active stacks 107.

[0075] By way of example, first, second and third layers, intended respectively to form the electron injection layer, the active region and the hole injection layer, are successively deposited on the side of the face 101T of the substrate 101. The stack consisting of the first, second and third layers is for example then structured, for example by photolithography then etching, so as to retain parts of the first, second and third layers located directly above the conductive regions 105. These parts of the first, second and third layers are intended to form the active stacks 107 of the organic photodetectors OPD of the image sensor 100.

[0076] In a manner similar to what was previously explained for the image sensor 100 in relation to FIGS. 2C and 2D, parts of the first, second and third layers extending laterally beyond the vertical line of the conductive regions 105 are furthermore retained at the end of the structuring. In the example illustrated in [Fig.3A], these parts of the first, second and third layers form, in top view, a grid connecting all the active stacks 107 together. This makes it possible, for example, to form an upper electrode common to all the active stacks 107, the common upper electrode corresponding in this case to the third layer of the stack, i.e. to the layer intended to form the hole injection layers of the organic photodetectors OPD.

[0077] Figures 3C and 3D illustrate more precisely, respectively by a top view and a sectional view along plane BB of [Fig.3C], a structure obtained at the end of a step of forming the opaque regions 109.

[0078] As an example, a buffer layer 301 is deposited on the side of the face 101T of the substrate 101, the buffer layer 301 thus coating the upper and lateral faces of the active stacks 107, the lateral faces and parts of the upper faces of the conductive regions 105 not coated with the active stacks 107, and the parts of the face 101T of the substrate 101 not coated with the conductive regions 105. The buffer layer 301 is for example then structured, for example by photolithography then possibly etching, so as to retain only parts of the buffer layer 301 coating the lateral and upper faces of the active stacks 107. For example, in the case where the buffer layer 301 is made of SU-8 resin, the structuring of the layer is carried out by development.

[0079] By way of example, the buffer layer 301 is an insulating layer, for example a layer made of the same material as the insulating layer 111 of the image sensor 100. The buffer layer 301 is for example intended to protect the opaque regions 109 with respect to the active stacks 107, for example in a case where the material of the opaque regions 109 is not compatible with at least one of the materials of the active stacks 107. The buffer layer 301 has for example a thickness of between 1 and 2 μm, for example equal to approximately 1.2 μm.

[0080] As a variant, for example in a case where the materials and solvents used in the method of depositing and structuring the opaque regions 109 are compatible with the materials of the active stacks 107, the buffer layer 301 can be omitted.

[0081] By way of example, a layer of the material intended to form the opaque regions 109 is then deposited on the side of the face 101T of the substrate 101, the layer thus coating the parts of the buffer layer 301, parts of the upper faces of the conductive regions 105 not coated with the active stacks 107 or parts of the buffer layer 301, and the parts of the face 101T of the substrate 101 not coated with the conductive regions 105. The layer is for example then structured, for example by photolithography then possibly etching, so as to retain only the opaque regions 109.

[0082] In the example shown, each opaque region 109 has, in top view, a rectangular annular shape. This example is however not limiting, each opaque region 109 being able, as a variant, to have, in top view, any annular shape, for example oval, circular, square, etc. The opaque region 109 has, for example, a periphery of a shape substantially identical to that of the underlying conductive region 105.

[0083] Figures 3E and 3F illustrate more precisely, respectively by a top view and a sectional view along plane BB of [Fig.3E], a structure obtained at the end of a step of forming the optical filters 113.

[0084] As an example, a layer of the material of the optical filters 113 is deposited on the side of the face 101T of the substrate 101. The layer is then for example structured, for example by photolithography then possibly etching, so as to retain only parts of the layer located on the upper faces of the buffer layer 301 and opaque regions 109.

[0085] Figures 3E and 3F illustrate an example in which each optical filter 113 has lateral dimensions substantially equal to those of a structure formed by the opaque regions 109 and the underlying buffer layer 301. This example is however not limiting, each optical filter 113 being able, as a variant, to have lateral dimensions strictly greater than those of this structure. Preferably, each optical filter 113 is substantially centered relative to the underlying active stack 107, and has lateral dimensions strictly greater than those of the underlying active stack 107. This makes it possible to ensure that all of the radiation coming from the side of the face 101T of the substrate 101 passes through the optical filter 113 before reaching the active stack 107.

[0086] Although not shown, another buffer layer may be interposed between the insulating regions 109 and the optical filters 113.

[0087] [Fig.4A], [Fig.4B] and [Fig.4C] illustrate, by a top view and schematic and partial sectional views, successive steps of a variant of the method for manufacturing the image sensor 300 of FIGS. 3A to 3F. According to this variant, the opaque regions 109 extend laterally over the active stacks 107 of the organic photodetectors OPD. The opaque region 109 of each organic photodetector OPD extends over and in contact with the upper face of the underlying buffer layer 301, or over and in contact with the upper face of the active stack 107, in the case where the buffer layer 301 is omitted.

[0088] Figures 4A and 4B illustrate more precisely, respectively by a top view and a sectional view along the plane BB of [Fig.4A], a structure obtained at the end of a step of forming the opaque regions 109, for example from the structure previously described in relation to Figures 3A and 3B.

[0089] The parts of the buffer layer 301 are for example formed as described above in relation to FIGS. 3C and 3D.

[0090] By way of example, a layer of the material intended to form the opaque regions 109 is then deposited on the side of the face 101T of the substrate 101, the layer thus coating the parts of the buffer layer 301, parts of the upper faces of the conductive regions 105 not coated with the active stacks 107 or parts of the buffer layer 301, and the parts of the face 101T of the substrate 101 not coated with the conductive regions 105. The layer is for example then structured, for example by photolithography then possibly etching, so as to retain only the opaque regions 109.

[0091] In the example shown, each opaque region 109 comprises vertical portions covering the sides of the active stack 107 and a horizontal portion, or upper portion, covering the upper face of the underlying active stack 107. In this example, each opaque region 109 in particular covers a face of the active region of the underlying organic photodetector OPD substantially parallel to the face 101T of the substrate 101 (the upper face of the active region, in the orientation of [Fig. 4B]). The vertical portions of each opaque region 109 are, in the example shown, substantially orthogonal to the face 101T of the substrate 101. The horizontal portion of each opaque region 109, surmounting the active region, makes it possible to act as a global filter for the organic photodetectors OPD.

[0092] In the example shown, the horizontal parts of the opaque regions 109 have a thickness e, or height, strictly less than a width W of the vertical parts of the opaque regions 109. By way of example, the width W of the vertical parts of the opaque regions 109 is equal to approximately 10 μm. By way of example, the width W of the vertical parts of the opaque regions 109 is at least five times less, preferably at least ten times less, than the thickness e of the horizontal parts of the opaque regions 109.

[0093] [Fig.4C] illustrates more precisely, by a sectional view along the plane BB of [Fig.4A], a structure obtained at the end of a step of depositing the insulating layer 111 and forming the optical filters 113. An image sensor 400 similar to the image sensor 300 is thus obtained.

[0094] The insulating layer 111 and the optical filters 113 of the image sensor 400 are for example produced as described previously for the image sensor 100.

[0095] The image sensors 300 and 400 have advantages similar to those of the image sensor 100. In particular, the presence of the opaque regions 109 allows the image sensors 300 and 400 to have reduced sensitivity to radiation coming from one side of the substrate 101 opposite the face 101T.

[0096] Depending on the materials considered, the method for forming at least some layers or regions of the image sensors 100, 300 and 400 may correspond to a so-called additive method, for example by direct printing of the material composing the organic layers or regions at the desired locations, in particular in sol-gel form, for example by inkjet printing, heliography, screen printing, flexography, spray coating or drop casting. Depending on the materials considered, the method for forming the layers or regions of the image sensors may correspond to a so-called subtractive method, in which the material composing the organic layers or regions is deposited over the entire structure and in which the unused portions are then removed, for example by photolithography or laser ablation. may include processes such as spin coating, spray coating, heliography, slot-die coating, blade-coating, flexography or screen printing. When the layers or regions are metallic, the metal is, for example, deposited by evaporation or sputtering over the entire substrate and the metallic layers or regions are delimited by etching.

[0097] Advantageously, at least some of the layers or regions of the image sensors 100, 300 and 400 may be produced by printing techniques. The materials of these layers or regions described above may be deposited in liquid form, for example in the form of conductive and semiconducting inks using inkjet printers or spin-coating, blade coating or die coating devices. By materials in liquid form is meant here also gel materials depositable by printing techniques. Annealing steps are optionally provided between the depositions of the different layers or regions, but the annealing temperatures may not exceed 150°C, and the deposition and any annealing may be carried out at atmospheric pressure.

[0098] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, adaptation of the described embodiments to the case where the buffer layer 301 is omitted is within the ability of those skilled in the art from the indications of the present description.

[0099] Finally, the practical implementation of the described embodiments and variants is within the reach of those skilled in the art from the functional indications given above. In particular, the described embodiments are not limited to the particular examples of materials and dimensions mentioned in the present description.

Claims

Claims

1. Image sensor (100; 300; 400) comprising a plurality of organic photodetectors (OPD) formed on a substrate (101) transparent to radiation of interest from the organic photodetectors, each organic photodetector comprising an active region whose sides are coated with a region opaque (109) to the radiation of interest from the organic photodetector.

2. Sensor (100; 300; 400) according to claim 1, in which the opaque region (109) has, in top view, an annular shape surrounding the active region.

3. A sensor (100; 400) according to claim 1 or 2, wherein the opaque region (107) is located on and in contact with the flanks of the active region.

4. Sensor (300; 400) according to claim 1 or 2, wherein each organic photodetector (OPD) further comprises an insulating layer (301) interposed between the sides of the active region and the opaque region (109).

5. A sensor (400) according to any one of claims 1 to 4, wherein the opaque region (109) comprises first portions covering the flanks of the active region and a second portion extending over an upper face of the active region.

6. Sensor (400) according to claim 5, in which the first parts of the opaque region (109) each have a width (W) strictly greater, preferably at least five times greater, more preferably at least ten times greater, than a thickness (e) of the second part of the opaque region.

7. Sensor (100; 300; 400) according to any one of claims 1 to 6, further comprising, for each organic photodetector (OPD), an optical filter (113) located directly above the active region of the organic photodetector.

8. A sensor (100; 300; 400) according to any one of claims 1 to 7, wherein the active region is located on and in contact with a lower electrode (105) of the organic photodetector (OPD).

9. A sensor (100; 300; 400) according to any one of claims 1 to 8, wherein each organic photodetector (OPD) comprises an active stack (107) comprising the active region interposed between an electron injection layer and a hole injection layer, the hole injection layer being common to all organic photodetectors of the sensor.

10. A sensor (100; 300; 400) according to any one of claims 1 to 9, wherein the substrate (101) is further transparent to visible light.

11. A sensor according to any one of claims 1 to 10, wherein the region (109) opaque to the radiation of interest of the organic photodetector (OPD) is further opaque to visible light.

12. A sensor (100; 300; 400) according to any one of claims 1 to 11, wherein the active region is adapted to detect near infrared radiation.

13. A method of manufacturing an image sensor (100; 300; 400) comprising the following steps: a) providing a substrate (101); and b) forming, on the substrate, a plurality of organic photodetectors (OPD), each organic photodetector comprising an active region whose walls are coated with an opaque region (109) to the radiation of interest of the organic photodetector, wherein the substrate is transparent to radiation of interest from the organic photodetectors.

14. The method of claim 13, wherein the active region is formed before the opaque region (109).

15. The method of claim 13, wherein the active region is formed after the opaque region (109).

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