ELECTROLUMINESCENT DISPLAY DEVICE, METHOD FOR MANUFACTURING SUCH A DEVICE AND ELECTROLUMINESCENT DISPLAY SYSTEM

Abstract

ELECTROLUMINESCENT DISPLAY DEVICE, METHOD FOR MANUFACTURING SUCH A DEVICE AND ELECTROLUMINESCENT DISPLAY SYSTEM One aspect of the invention relates to a method for manufacturing an electroluminescent display device from islands separated by a trench, the method comprising: filling the trench with an insulating structural element; forming a protective tape (108) covering, only partially, each of the islands and overlapping the structural element; partially etching the structural element so as to form a pillar (109) under the protective tape so that the latter has cantilevered parts (110a, 110b); and depositing an organic layer resulting in two distinct and separate portions, a first portion extending continuously over each island and over the protective tape, and a second portion extending over the substrate. Figure to be published with the abbreviation: Figure 15

Description

Title of the invention: ELECTROLUMINESCENT DISPLAY DEVICE, METHOD FOR MANUFACTURING SUCH A DEVICE AND ELECTROLUMINESCENT DISPLAY SYSTEM TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of optoelectronic devices and more particularly that of matrix display devices with organic electroluminescent layers.

[0002] The present invention relates to a method for an OLED (Organic Light-Emitting Diode) type electroluminescent display device and a method for manufacturing such a device.

[0003] The present invention finds advantageous application in the realization display screens for electronic devices, and in particular for the production of high-resolution color display screens such as AMOLED (Active Matrix Organic Light-Emitting Diode) displays. The term "high resolution" refers to pixels smaller than 15 µm. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] In the field of matrix display devices with organic light-emitting layers, OLED type matrix micro-displays (called "microdisplay" in English) are known, which have pixels arranged in a step of less than 20 pm, typically between 4 pm and 12 pm.

[0005] When this type of matrix display is in color, each pixel is subdivided into sub-pixels of different colors (typically three, with red, green, and blue as their colors) which cooperate so that the pixel emits the desired color. The surface of the sub-pixels can be rectangular, square, or other (for example, octagonal) and their size can depend on the color. The typical size of the sub-pixels can vary from 1 µm to 20 µm.

[0006] Each sub-pixel is generally formed by several superimposed layers, including a lower electrode (the anode) deposited on a common substrate, several organic layers (at least one of which is emissive) forming an OLED stack on each lower electrode, and an upper electrode (the cathode).

[0007] Documents FR3079909A1 and US2023 / 0041252Al describe structures enabling the formation of OLED pixels (or OLED sub-pixels) of such small size with improved industrial reliability.

[0008] These structures have the common advantage of allowing soft discretization of the OLED stack and the cathode to form the pixels (or sub-pixels). The expression "soft discretization" refers to a structuring process that preserves the performance of the OLED stack.

[0009] In particular, the proposed solutions consist of carrying out the discretization of the OLED stack other than with masking and removal steps which generally require environments (humidity, temperature above 90°C, solvents, ultraviolet, etc.) which are detrimental to organic materials.

[0010] Document FR3079909 A1 describes a first OLED display device in which the lower electrodes of each subpixel are separated from each other by an insulating wall rising vertically from the substrate. Each wall acts as a separator between two neighboring subpixels.

[0011] This same document FR3079909 describes a second device in which the insulating walls are replaced by trenches in which an insulating layer is deposited.

[0012] The insulating walls and trenches are formed before the OLED stack is deposited by thermal evaporation and serve the same purpose. Since the evaporation deposition technique is predominantly directional, the OLED stack is preferentially deposited on the horizontal walls of the device, and not on the lateral walls of the insulating walls or trenches. The OLED stack is thus broken (or discretized) at the insulating walls or trenches.

[0013] However, in practice, the directivity of the OLED stack deposition is never absolute. Organic particles can thus also be deposited on the side walls of insulating walls or trenches. These particles are undesirable because they degrade the (electrical, optical) insulation between sub-pixels. Neighboring sub-pixels can then interact with each other, for example through capacitive coupling or parasitic currents. These phenomena, known as crosstalk, lead to a degradation of the display device's performance. These phenomena are exacerbated when the sub-pixels are so-called "tandem" organic light-emitting diodes, that is, when the sub-pixels comprise several stacked OLEDs connected in series by means of interconnect layers.

[0014] Document US2023 / 0041252A1 offers a solution to this problem by describing subpixel separators that are arranged on a substrate and have a mushroom-shaped (or "hang-over" according to the English terminology used in this document) structure. More specifically, this mushroom-shaped structure comprises a lower part having oblique faces, forming the stem of the mushroom. It also comprises an upper part, wider than the lower part. The lower part, which hides a region of the substrate, is the upper part that forms the cap of the mushroom.

[0015] The sub-pixels are formed once the mushroom-shaped structures are in place. The OLED stack is then deposited onto these structures and broken at the upper parts. The OLED stack is broken with satisfactory reliability since the organic material cannot be deposited on the region of the substrate masked by the upper part or on the lateral walls of the mushroom-shaped structure (the lower part is not accessible from above because it is hidden by the upper part). Thus, the degree of directivity of the OLED stack deposition is of little importance.

[0016] These mushroom-shaped structures are, however, particularly complex to manufacture and not very compact (vertically, they have a height of approximately 1 µm). Furthermore, manufacturing a common upper electrode (cathode) requires the use of specific equipment to perform oriented deposition at the desired angle. This involves depositing a conductive layer under the upper part of the mushroom-shaped structures at a very specific angle determined by the inclination of the surfaces of the lower parts. Therefore, deploying such a manufacturing process is neither easy nor economically advantageous.

[0017] There is therefore still a need for a manufacturing process for OLED display devices with improved resolution that is less expensive and simpler to implement. Summary of the invention

[0018] The invention provides a solution to the problems mentioned above by enabling the formation of a common upper electrode between several pixels (the upper electrode generally being the common cathode) using separation structures integrated into the lower electrodes of the pixels (these often being the anodes of these pixels). To this end, the invention allows the lower portions of two adjacent pixels to be discretized by providing a continuous surface between these two pixels to form a layer of organic material and a continuous upper electrode.

[0019] One aspect of the invention relates to a method for manufacturing an electroluminescent display device from a precursor, said precursor comprising a plurality of islands arranged on a substrate, each island comprising a support layer extending over the substrate and a conductive layer extending over the support layer, the islands being separated in pairs by a trench, the method comprising: • filling each trench separating the islands with a structural element electrically insulating the islands, for each trench, the filling being carried out until said structural element reaches the top of the islets separated by said trench; • a formation of at least one protective strip, each protective strip connecting two islands together by overlapping the trench separating said two islands and covering the structural element extending into the trench, each protective strip covering, only partially, each of the two islands it connects; • a partial etching of the structural element selectively with respect to each protective tape and with respect to the conductive layers of the islands, the partial etching comprising at least one isotropic etching phase, the partial etching being carried out so as to retain only a portion of the structural element disposed under each protective tape and said portion forming a pillar for each protective tape, the partial etching being further carried out so that at least a portion of each protective tape extends cantilevered beyond the pillar that supports it; and • a deposition of an organic layer in an anisotropic manner at an angle substantially perpendicular to the substrate, resulting in two distinct and separate portions of the organic layer, a first portion extending continuously over each island and over each protective strip, and a second portion extending over the substrate, a deposition thickness of the organic layer being chosen so that the second portion of the organic layer does not reach said at least an overhanging part of each protective strip.

[0020] Each island comprises a conductive layer that can form a lower electrode. The use of a support layer for each island allows this conductive layer to be raised above the substrate. The protective tape extends from one island to the next and is supported by the insulating element. Each protective tape forms a bridge between two islands. This bridge allows for the formation of a continuous organic layer on the islands without any gaps between them. An additional conductive layer can then be deposited on this organic layer to form a continuous upper electrode without any gaps between the islands. This allows for the formation of a common upper electrode (for example, a common cathode) for all the islands.

[0021] Removing a portion of the structural element beneath each protective strip allows for the formation of a bridge with cantilevered sections extending over the substrate in the trench. A "cantilevered section" is defined as a suspended or unsupported section. There is therefore a discontinuity between the edge of the bridge and the substrate. Consequently, depositing an organic material on the islands and bridges creates two distinct portions of said organic material, without electrical contact between them. During the deposition process, a portion of the organic material is deposited on each protective strip, particularly on the cantilevered sections of each strip, while another portion falls between the islands, onto the substrate. The presence of these cantilevered sections breaks the continuity between the protective strips and the substrate. As long as the thickness of the deposited organic material does not allow the portion extending onto the substrate to reach the cantilevered sections, the two portions of the organic material (that on the bridges and islands, and that on the substrate) remain distinct and without physical or electrical continuity.

[0022] Thus, it is possible to form an organic layer and a common electrode for several islands, without risk of short-circuiting with the lower electrodes and without risk of electrical contact with surrounding elements (such as an additional island not intended to be connected to these islands). This makes it possible to create a higher-quality display device and also to simplify its manufacture. Indeed, a full-plate deposition, even if imperfectly directional, can be used to form the active elements and the upper electrodes of the final pixels.

[0023] Furthermore, when the device comprises more than two islands, separated from each other by trenches, it is then possible to connect the islands in pairs with a bridge as previously proposed, to form a common organic layer and / or a common cathode. It is not necessary to provide additional separating elements to ensure electrical isolation between the final pixels. It is then possible to form separate pixel chains, each chain having a common cathode. This reduces the number of steps required compared to prior art solutions. The manufacturing process is thus simpler and faster to implement.

[0024] Advantageously, the partial engraving of the structural element is carried out so that the lateral deviation of said at least one cantilevered part of each protective strip relative to the pillar which supports it is strictly greater than 100 nm.

[0025] Advantageously, for each trench, the filling is carried out until the structural element exceeds the conductive layers of the two islands separated by said trench by a height of between 10 nm and 100 nm.

[0026] Advantageously, each island comprises, before the filling of each trench, a sacrificial layer extending over the conductive layer, the filling of each trench with the structural element being carried out so that the structural element reaches the top of the sacrificial layers extending over the islands.

[0027] Advantageously, the method further comprises, after filling each trench and before forming each protective strip, engraving the sacrificial layer of each island selectively with respect to the structural element, the engraving being carried out with a stop on said conductive layer of said island.

[0028] Advantageously, for each trench, the backfilling with the structural element comprises: • a deposit of a layer of electrically insulating material so as to completely fill said trench; • polishing of the layer in electrically insulating material with a stop on the sacrificial layer of each island.

[0029] Advantageously, for each trench, the filling with the structural element comprises the following steps: • a deposit of a dielectric layer in a conforming manner in said trench; • a deposit of a layer of filler material on the dielectric layer so as to completely fill said trench; • polishing of the dielectric layer and the filling layer with a stop on the sacrificial layer of each island.

[0030] Advantageously, the filling material is amorphous silicon or polycrystalline silicon.

[0031] Advantageously, the process includes, before the formation of each protective strip, a thinning or swelling of the structural element so that it overflows onto a portion of the conductive layer of each island, forming at least one continuous and edgeless free surface extending from the conductive layer of one of the islands to the conductive layer of another island, each free surface having a slope, measured with respect to the substrate, of between -45 degrees and 45 degrees and preferably between -20 degrees and +20 degrees.

[0032] Advantageously, each protective tape is electrically insulating.

[0033] Advantageously, the partial etching of the structural element comprises at least one anisotropic etching phase and at least one isotropic etching phase, for example in alternation, each anisotropic etching phase being carried out with a directivity substantially perpendicular to the substrate.

[0034] Advantageously, the process comprises, after the deposition of the organic layer, the deposition of an additional conductive layer in an anisotropic manner, resulting in two distinct and separate portions of the additional conductive layer, of which a first portion of the additional conductive layer extends continuously over the first portion of the organic material layer, and a second portion of the additional conductive layer extends over the second portion of the organic layer, a deposition thickness of the additional conductive layer being chosen such that the second portion of the additional conductive layer does not reach said at least an overhanging part of each protective tape.

[0035] Advantageously, the partial etching of the structural element is further carried out in such a way as to partially etch the support layer of each island so that, for each island, at least a part of the conductive layer of said island extends cantilevered beyond the support layer of said island.

[0036] Another aspect of the invention relates to an electroluminescent display device comprising a plurality of islands, arranged on a substrate, each island comprising a support layer extending over the substrate and a conductive layer extending over the support layer, the device comprising: • at least one trench separating the islets in pairs; • at least one protective tape, each protective tape connecting two islands together by overlapping the trench separating said two islands and covering the pillar extending into the trench, each protective tape covering, only partially, each of the two islands; • at least one pillar filling at least part of a trench and electrically insulating the islands separated by said trench, each pillar reaching or exceeding the top of the two islands separated by said trench, each pillar being positioned under a protective tape to support said protective tape such that at least a portion of said protective tape extends cantilevered beyond said pillar; and • an organic layer having two distinct portions separate from each other, of which, a first portion extending continuously over each island and over each protective strip, and a second portion extending over the substrate without reaching said at least an overhanging part of each protective strip.

[0037] Advantageously, the lateral deviation of said at least one cantilevered part of each protective strip relative to the pillar that supports it is strictly greater than 100 nm.

[0038] Advantageously, said at least one pillar is made from an electrically insulating material.

[0039] Advantageously, said at least one pillar comprises a dielectric layer, allowing to electrically isolate the islands separated by said at least one pillar; and a filling material, insulating or not, providing a support for the protective tape, the dielectric layer of said at least one pillar separates the filling material of said at least one pillar from each island.

[0040] Advantageously, said at least one pillar has a continuous, edgeless surface over which the protective tape extends, said continuous, edgeless surface extending from the conductive layer of one of the islands to the conductive layer of another island, each continuous and without edge presenting a slope, measured in relation to the substrate, between -45 degrees and 45 degrees and preferably between -20 degrees and +20 degrees.

[0041] The invention further relates to an electroluminescent display system, comprising: • a device according to the invention; and • an active addressing matrix comprising a plurality of transistors, each transistor of the plurality of transistors being connected to the conductive layer of one of the islands of said device.

[0042] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0043] The figures are shown for illustrative purposes only and are not intended to limit the invention. Unless otherwise specified, the same element appearing in different figures has a unique reference numeral.

[0044] [Fig.1], [Fig.2] and [Fig.3] schematically show, according to three views, an embodiment of a precursor of a display device according to the invention.

[0045] [Fig.4], [Fig.5] and [Fig.6] schematically show, according to three views, a first step in a manufacturing process for the display device according to the invention.

[0046] [Fig.7], [Fig.8] and [Fig.9] schematically show, according to three views, a second step in the manufacturing process of the display device according to the invention.

[0047] [Fig. 10] and [Fig. 11] schematically show, from two views, examples of protective tapes according to the invention.

[0048] [Fig. 12] and [Fig. 13] schematically show two other examples of protective tapes according to the invention.

[0049] [Fig. 14], [Fig. 15], [Fig. 16] and [Fig. 17] show schematically, according to three views, a third step in the manufacturing process of the display device according to the invention.

[0050] [Fig. 18], [Fig. 19] and [Fig. 20] schematically show, according to three views, a fourth step in the manufacturing process of the display device according to the invention.

[0051] [Fig.21], [Fig.22] and [Fig.23] schematically show, according to three views, a fifth step of the manufacturing process of the display device according to the invention.

[0052] [Fig.24], [Fig.25], [Fig.26], [Fig.27] and [Fig.28] schematically show four steps of a variant of the manufacturing process according to the invention. DETAILED DESCRIPTION

[0053] The present invention aims to improve the manufacture of organic electroluminescent display devices with improved resolution, also called OLED micro-displays (for "Organic Light-Emitting Diodes" in English).

[0054] In the following description, the term "pixel" refers to a sub-pixel, that is, the smallest element composing a pixel of an electroluminescent display device 200.

[0055] The pixels preferably have lateral dimensions less than 20 pm, or even less than 10 pm, preferably between 5 pm and 1 pm, for example, equal to 3 pm. They are arranged, for example, with a spacing of less than 20 pm, for example, between 4 pm and 12 pm. In top view, they have, for example, a rectangular shape, with a length-to-width ratio of approximately 3:1. The size of the pixels will hereafter be referred to as the side of the square.

[0056] The present invention thus relates to a method of manufacturing an electroluminescent display device from a precursor 100. An example of precursor 100 is shown in figures 1 to 3. These figures show in particular the precursor 100 in a top view ([Fig.1]), and in two sections (figures 2 and 3) corresponding to the X and Y directions shown in [Fig.1].

[0057] In this example, the precursor comprises a substrate 102 and a plurality of islands 101. The islands 101 are intended to form the final pixels of the display device 200. Viewed from above, they have a rectangular shape. Alternatively, they could have a square, triangular, hexagonal, circular, or any other shape. They are arranged on the substrate 101 in groups of two, in this case three groups of two islands. Each group of two islands forms a column and is, for example, aligned parallel to the Y direction. A cross-section of one of the groups of two islands 101 corresponds to the cross-section of [Fig. 3]. The three columns (i.e., the three groups of two islands 101) are distributed along the orthogonal X direction. The islands 101 can, for example, also be aligned along the X direction to form rows of islands 101.The 101 islands can be arranged along the X or Y directions with a spacing of less than 20 pm, for example, between 4 pm and 12 pm. Thus, groups of islands can also be arranged with a spacing of less than 20 pm, for example, between 4 pm and 12 pm. Alternatively, the islands can be arranged differently. For example, islands within a group can be arranged in a hexagonal lattice (also called a "honeycomb lattice"). The spacing is then adjusted to correspond to a hexagonal arrangement with a spacing of less than 20 pm, for example, between 4 pm and 12 pm.

[0058] The substrate 102 is advantageously a specialized circuit or ASIC (for "Application Specified Integrated Circuit") of the CMOS (for "Complementary Metal Oxide Semiconductor") type. In this case, the substrate 102 is opaque and therefore advantageously suitable for manufacturing a top-emitting electroluminescent display device. In the following description, the terms "transparent" and "opaque" refer to an element that, for at minus one wavelength of the spectral band [400 nm; 1000 nm], or even [400 nm; 2000 nm], an optical transmission coefficient respectively greater than 60%, and less than or equal to 60%.

[0059] Note that the substrate 102 can alternatively be made of amorphous silicon, polycrystalline silicon and / or deposited on a glass plate. In the latter case, the substrate 102 can be transparent and therefore suitable for manufacturing a bottom-emitting electroluminescent display device.

[0060] The substrate 102 includes an addressing circuit (not shown) configured to address the output pixels of the display device 200. The substrate 102 may also include an electrically insulating layer, which may be an oxide, a nitride, or an oxynitride. This insulating layer is, for example, made of silicon nitride (SiN). The substrate 102 may further include a plurality of contact pads arranged through the insulating layer to establish electrical contact with the output pixels of the device 200.

[0061] All the islets 101 are separated from each other by at least 106 trenches. Trenches 106 separate columns of islands 101 and rows of islands 101. In other words, within a group of islands 101, the islands 101 are separated by a trench 106. Each trench 106 is excavated from the top of the islands 101 down to the substrate 102. Trenches 106 can partially separate the islands 101, for example, by excavating only part of the height of the islands (the islands 101 share, for example, a lower section). Trenches 106 can also be excavated within the substrate 102 to improve the isolation of the islands 101. The islands 101 can be arranged with a spacing of less than 20 pm, for example, between 4 pm and 12 pm. The width of a trench 106 separating two adjacent islands 101 is for example between 0.3 pm and 1.5 pm.

[0062] The islands 101 of the same group (for example, of the same column) are intended, for example, to form pixels that will emit the same range of wavelengths. The three columns of islands 101 illustrated correspond, for example, to different wavelengths, such as the lengths corresponding respectively to blue, green, and red.

[0063] Each island 101 has a mesa shape. That is to say, it is delimited by a single flank 112, extending from the substrate 101 to the top of the island 101. The flanks 112 of the islands also form the edges of the trenches 106. In top view, the islands 101 may have a rectangular shape with a height-to-width ratio of 3:1 to within 10%. The islands 101 may have square, hexagonal, circular, or similar shapes. Each of them has a surface area, in top view ([Fig. 1]), advantageously less than 40 pm², preferably between 30 pm² and 1 pm², for example, 5 pm².

[0064] Each island 101 comprises a support layer 104, extending over the substrate 102. It extends directly against the substrate 102 or may be separated from it by another layer (for example, a diffusion barrier or a layer promoting a particular crystallographic growth). The support layer 104 has a thickness H104 that can be between 150 nm and 1000 nm. The support layer 104 may be conductive, in which case it may be made from aluminum Al, a copper-aluminum alloy AlCu, chromium Cr, or silver Ag. Alternatively, it may be electrically insulating and in this case made from a dielectric such as silicon dioxide SiO2, silicon nitride SiN, or aluminum oxide Al2O3.

[0065] Each island 101 also includes a conductive layer 103. The conductive layer 103 is intended to form an electrode of the final pixel, and in this case, a bottom electrode. In the following description, the conductive layer 103 may be referred to interchangeably as the "bottom electrode." The bottom electrode 103 extends over the support layer 104. It extends directly against the support layer 104 or it may be separated from it by another layer (such as a diffusion barrier or a layer promoting a particular crystallographic growth). The bottom electrode 103 is preferably parallel to the substrate 102.

[0066] The lower electrode 103 can be reflective, for example, for a top-emitting electroluminescent display. The support layer 104 is advantageously reflective or opaque. In top-emitting configurations, all or part of the support layer 104 can also be conductive. The support layer 104 includes, for example, an insulating portion (surrounding, for example, contact means with a via located below the island). It can also be conductive. The term "reflective" refers to a surface or element that exhibits, for at least one wavelength in the spectral band [400 nm; 1000 nm], or even [400 nm; 2000 nm], an optical reflection coefficient greater than 60%. The lower electrode 103 can be transparent, for a bottom-emitting electroluminescent display. In this case, the support layer 104 is advantageously transparent.It includes, for example, an insulating portion (surrounding, for example, means of contact with a via located below the island) made of transparent dielectric. The support layer 104 is, however, advantageously conductive. It includes, for example, a means of connecting the islands with a via located in the substrate 102 (see the conductive pillars 116 described below). It can also be entirely conductive.

[0067] The lower electrode 103 may alternatively comprise several stacked sublayers. Each sublayer is then formed of a metallic material or a different metallic alloy. The metallic material(s) (or metallic alloy(s) used to form the first conductive layer 103 preferably all have the property of being resistant to the etching chemistry of the support layer 104 and / or the structural element 107.

[0068] When the support layer 104 is insulating and comprises, for example, a dielectric such as SiO2, the lower electrode 103 can be formed from a metallic material or a conductive alloy. The lower electrode 103 comprises, for example, a stack of conductive sublayers such as Ti / TiN / SnO2. In this case, the thickness of the lower electrode 103 is preferably greater than 20 nm, and preferably between 40 nm and 100 nm. Alternatively, the lower electrode 103 can be formed from a transparent conductive oxide (TCO) to create a bottom-emitting electroluminescent display device.

[0069] When the support layer 104 is conductive, the lower electrode 103 is preferably formed from a transparent conductive oxide, for example from indium tin oxide (or ITO for "Indium Tin Oxide" according to the commonly used Anglo-Saxon terminology), or from zinc oxide (ZnO) or from aluminum-doped zinc oxide (or "AZO" for "Aluminum Zinc Oxide" in English) or from tin oxide SnO2.

[0070] When the lower electrode 103 is a stack of conductive sublayers, these sublayers can be formed from titanium nitride (TiN), tin oxide (SnO2), poly(3,4-ethylenedioxythiophene) (or PEDOT), ITO, zinc oxide (ZnO), or AZO. Preferably, the sublayer intended to be in contact with an organic layer is made of tin oxide (SnO2), while the sublayer in contact with the support layer 104 is made of titanium nitride (TiN).

[0071] The lower electrode 103 preferably has a thickness between 4 nm and 20 nm. When it comprises a stack of sublayers, the thicknesses may vary depending on the materials. For example, a TCO sublayer has a thickness between 10 nm and 20 nm. A TiN sublayer, for example, has a thickness of less than 10 nm, preferably between 4 nm and 8 nm.

[0072] The support layer 104 is intended to support the lower electrode 103. In other words, the support layer 104 is a linking element between the substrate 102 and the lower electrode 103, which ensures that the lower electrode 103 is held on the substrate 102. The lower electrode 103 is therefore not in direct contact with the substrate 102.

[0073] The support layer 104 is at least partly conductive, so that it also serves to establish an electrical connection between the lower electrode 103 and a contact pad or a via located below the island (and therefore the final pixel). For Each island 101, if the support layer 104 is not conductive, may include a conductive pillar 116 (for example, the pillars are only shown in Figures 2 and 3), in contact with the lower electrode 103, and surrounded by a dielectric material (such as those mentioned previously). The presence of the dielectric material in this layer 104 provides or improves the mechanical support of the lower electrode 103.

[0074] To simplify the description, in the following description, and unless otherwise stated, only two neighboring islands 101 in the same column are considered. These correspond, for example, to the islands in Figures 3, 6, 9, 12, 13, 16, 19, 22, 24, 25, 26, 27, and 28. In other words, two neighboring islands 101, separated by the same trench 106, are considered. The principles described below can be applied to a column of more than two islands 101; it suffices to consider the islands 101 two at a time.

[0075] Figures 4 to 9 show a step in filling the trench 106, separating the two islands 101, by means of a structural element 107. This structural element 107 thus separates the two islands 101 while ensuring electrical insulation between them. The structural element 107 preferentially fills the entire trench 106 and is in direct contact with the two islands 101.

[0076] At the end of the filling, the structural element 107 reaches the top of the two islands 101. In other words, the structural element 107 has a height H107, measured perpendicularly to the substrate 102 and from this substrate, greater than or equal to, and preferably equal to, the heights H101 of the islands 101. The height H101 is for example measured from the substrate 102 to the top of each island 101.

[0077] In one embodiment, the trench 106 is filled until the conductive layers 103 are reached. By "reaching the conductive layers," it is meant that the structural element 107 has a height, measured from the substrate 102, that allows it to be in direct contact with the conductive layers 103. In other words, the structural element 107 is flush with the conductive layers 103 or extends beyond them. Preferably, the structural element 107 is flush with the conductive layers 103.

[0078] In a variant of the process, detailed below, the islands 101 can include sacrificial layers 105, increasing the total height H101 of each island 101. In the presence of the sacrificial layers 105, the filling of the trench 106 is carried out until reaching the top of the islands 101, i.e. the top of the sacrificial layers 105. From then on, the structural element 107 exceeds the conductive layers 103.

[0079] According to this variance, the height difference between the structural element 107 and the conductive layers 103, H73 = H107 - H103, is greater than or equal to zero. The conductive layers 103 could be non-planar and have heights different. In this case, the heights are compared to the vertical of the side 112 of the islets 101 and in particular, to the vertical of the portion in contact with the structural element 107.

[0080] Figures 10 to 13 illustrate a protective tape 108. The protective tape 108 forms a bridge between the two islands 101 of the same column. It thus supports a layer of organic material extending continuously and in one piece over the two islands 101.

[0081] The protective tape 108 is therefore a single-piece layer, i.e. continuous, without cut or break, extending from one of the islands 101 to the other island 101. The protective tape 108 covers only a part of each island 101. In this way, the layer of organic material can be in direct contact with the rest of each lower electrode 103.

[0082] The protective tape 108 also extends over the structural element 107 separating the two islands so as to cover at least a portion of it. In [Fig. 10], three examples of protective tape 108 are illustrated. According to a first, preferred example, in a first column (left column), the protective tape 108 extends over a portion of the lower electrode 103 of one island 101 and continues in the Y direction to the other island 101 in the column. The mask 108 covers only a small portion of each island 101 and a small portion of the structural element 107. According to a second example, in a second (central) column, the protective tape 108 extends over a larger portion of each lower electrode 103, partially crossing the surfaces of these electrodes.According to a third example, in a third column (on the right), the protective strip 108 extends in line with the two islands 101, completely covering the structural element 107 which separates the two islands 101. Figure 11 shows a cross-section of these different examples.

[0083] The protective tape 108 allows for the formation of a bridge enabling the deposition of continuous layers of material on two adjacent islands 101. It may be necessary to form a continuous layer on more than two islands 101, for example, to connect all the islands belonging to the same column of islands 101. In this case, several protective tapes 108 can be formed, each covering two adjacent islands 101 as well as the structural element 107 that separates them.

[0084] It may be advantageous for each protective strip 108 to be limited to only two adjacent islands 101 (as well as the associated structural element 107). However, to form a continuous layer over more than two islands 101, the protective strip can be formed so as to cover each of these islands 101 while maintaining a continuous, single-piece layer. Alternatively, it may be preferable for each protective strip 108 to be limited to only two islands 101 (and the associated structural element 107) and strictly to these two islands 101.

[0085] Figure 12 shows an example of a protective tape 108. This tape 108 corresponds, for example, to the example on the left in Figure 10. The protective tape 108 covers part of each lower electrode 103 while spanning the structural element 107 separating these islands 101.

[0086] Figure 13 shows another example of a protective tape 108. This tape 108 can also correspond to the example on the left in Figure 10. In this example, the structural element 107 partially overlaps each island 101. In particular, it has an upper surface extending from one lower electrode 103 to the other and forming a gentle slope. By "gentle slope" is meant a slope, measured with respect to the substrate 102, of between -45 degrees and 45 degrees and preferably between -20 degrees and +20 degrees and even more preferably between -5 degrees and +5 degrees. The protective tape 108 covers a portion of each lower electrode 103 and the structural element 107, also exhibiting a gentle slope.

[0087] The protective tape 108 is preferably electrically insulating to prevent a short circuit between the lower electrodes 103 of the islands 101 joined by this tape 108. It is, for example, made of aluminum oxide Al2O3, SiO2, or SiN. It is preferably resistant to the etching chemistries of the structural element 107.

[0088] Figures 14 to 16 show the result of a partial etching of the structural element 107. The etching is carried out selectively with respect to the protective tape 108. It also includes at least one phase during which the etching is isotropic. The isotropic etching phase removes all parts of the structural element 107 that are not protected, in particular by the protective tape 108. The trenches 106 are thus partially exposed. The etching, and in particular its speed and duration, are designed so as to retain only a portion 109 of the structural element 107 under each protective tape 108, said portion 109 forming a pillar. [Fig. 15] shows the result of the partial etching with respect to [Fig. 11]. In [Fig.11] (which corresponds to a section along a trench 106) the structural element 107 occupies the entire trench 106. In [Fig.

[15] , there are only three pillars 109, placed under each protective tape 108, that remain in the trench 106. The rest of the trench 106 is free. The partial etching may consist of only one etching phase, in this case, an isotropic etching phase. However, under certain conditions, an isotropic etch may remove too quickly the parts of the structural element 107 that are masked by the protective tape 108. In order to remove the unmasked parts (for example, the parts exposed in the trench) more quickly, leaving only the pillar 109 under the tape 108, the etching may include several etching phases. For example, it may include at least one anisotropic etching phase and at least one isotropic etching phase, for example, alternating them (e.g., anisotropic / isotropic / anisotropic / ...). An etching phase. An isotropic etching preferentially follows an anisotropic etching phase. Anisotropic etching phases are performed with a directionality substantially perpendicular to the substrate. Thus, during these phases, only the exposed (i.e., unmasked by the ribbon) portions of the structural element 107 are etched. During isotropic phases, all portions of the structural element 107, even those positioned beneath the ribbon 108, are etched. Exposed portions are therefore etched during both phases, while masked portions are etched only during the isotropic phase. The etching speed of exposed portions is thus increased compared to the etching speed of masked portions.

[0089] The isotropic phase of the partial etching can be carried out in a humid environment, for example, using hydrofluoric acid (HF) with an HF concentration between 0.1% and 2% and at room temperature. The isotropic phase can also be carried out by isotropic dry etching, for example, using SF6 (to etch amorphous silicon) or HF (to etch Al2O3 without etching the amorphous silicon).

[0090] The partial engraving leaves a pillar 109 under each strip 108. Each pillar 109 of the structural element 107 is delimited by a peripheral lateral surface, also referred to as the "flank". Each pillar 109 is completely delimited by a flank. In the example of Figures 4 to 16, the flank comprises four consecutive surfaces, including: • two surfaces opposite each other and perpendicular to the Y-axis; and • two other surfaces 109a, 109b, called “sides of the pillar”, also opposite each other and perpendicular to the axis X' (and X).

[0091] The two sides 109a, 109b of the pillar are perpendicular to the trench 106, the latter extending along the X' direction. As the structural element 107 initially fills the trench 106 separating the two islands, the surfaces perpendicular to Y are in contact with the islands 101. Conversely, the sides of the pillar 109a, 109b, perpendicular to X' and therefore to the trench 106, are free because they face the portions of trench 106 that were exposed by the engraving. Due to the isotropic engraving effect, the sides of the pillar 109a, 109b may have a concave shape, slightly intruding into the pillar 109.

[0092] Each protective strip 108 also has edges 108a, 108b extending perpendicularly to the direction X', that is, perpendicularly to the trench 106 which it straddles. The sides 109a, 109b of the pillar 109 are substantially perpendicular to the edges 108a, 108b of the protective strip 108 supported by said pillar 109.

[0093] Since the engraving is performed selectively with respect to each protective strip 108, the edges of the strip 108a, 108b remain intact (or change very little). The Partial engraving is carried out so as to set back the sides 109a, 109b of each pillar 109 from the edges 108a, 108b of the protective strip 108. Thus, for each strip 108, the sides 109a, 109b of the pillar 109 supporting said strip 108 are set back from the edges 108a, 108b of said strip 108. In this way, the protective strip 108 has two cantilevered parts 110a, 110b extending beyond the pillar 109. The cantilevered parts 110a, 110b of the strip 108 thus overhang the trench 106 and more particularly the substrate 102 exposed in the trench 106 during the engraving.

[0094] By "retraction" is meant a lateral distance, measured along a direction X' and parallel to the substrate 102, between one of the edges 108a, 108b of the protective tape 108 and the nearest side 109a, 109b of the pillar 109. This retraction corresponds to the advancement of the cantilevered part 110a, 110b of the protective tape 108. The retraction is preferably greater than 100 nm.

[0095] The partial engraving of the structural element 107 also has the effect of centering each pillar 109 under the protective strip 108 that it supports. Thus, each pillar 109 effectively supports the protective strip 108. Retracting the structural element 107 under the protective strip 108 makes it possible to form a bridge joining the two islands 101 and having cantilevered portions 110a, 110b, overhanging the substrate 102.

[0096] Figures 18 to 20 show the result of a deposition step, for example by evaporation, of an organic layer 201 intended to form an active element of the final pixel of the display 200. The deposited organic material is configured to generate electromagnetic radiation when an electric current passes through it. The emitted radiation can be white or an equivalent color of red, green, or blue. The organic layer 201 can comprise a single layer configured to emit radiation having a spectrum located, for example, primarily in the blue, i.e., a spectrum extending over a wavelength range between 430 nm and 490 nm. The active layer 201 can alternatively comprise several emissive sublayers allowing the formation of a so-called "tandem" OLED structure (not shown).In this case, the organic layer 201 comprises several organometallic sublayers, typically consisting of two emissive organic sublayers arranged one on top of the other and separated by functional organic layers of the charge transport, charge injection, and / or charge generation type. In the following description, for the sake of simplicity, the term "organic layer" will refer to a homogeneous layer, a stack of organic sublayers, or a stack of organometallic sublayers.

[0097] The organic layer 201 is preferentially deposited anisotropically in a direction substantially perpendicular to the substrate 102. By "substantially perpendicular," we mean perpendicular to within + / - 20 degrees. The deposit is full-plate. Thanks to the removal of the pillar 109 supporting the protective tape, the layer Organic 201 is split into two distinct portions 201-1, 201-2. A first portion 201-1 extends over each island 101 and over the protective strip 108, acting as a bridge and connecting these islands 101. A second portion 201-2 of the organic layer 201 extends over the substrate 102, in the trenches 106 exposed by the partial engraving of the structural element 107. Since the sides 109a, 109b of the pillars 109 are recessed, there is no organic material accumulating against these sides. Sides 109a, 109b are protected by the cantilevered parts 110a, 110b of the protective tape 108. Therefore, there is no deposit of organic matter that could form a bond between the two portions 201-1, 201-2 of the organic layer 201. The cantilevered parts 110a, 110b of the protective tape 108, overhanging the substrate 102, cause the excess organic material to fall into the center of the trenches 106 and away from sides 109a, 109b of the pillar 109.

[0098] The organic layer 201 may slightly overhang the overhanging parts 110a, 110b of the protective tape 108, forming a cap which covers the upper part of the tape 108 as well as the edges 108a, 108b of the tape 108.

[0099] To ensure separation of portions 201-1, 201-2 of the organic layer 201, the thickness H201 of the organic layer 201 is preferably less than the height H109 of the pillar 109. In this way, the second portion 201-2 of the organic layer 201, extending over the substrate 102, does not reach the protective strip 108, and in particular its portions 110a, 110b, which cantilever over the second portion 201-2. Indeed, if the thickness reaches the height H109 of the pillar 109, the organic layer 201 would then reach the edge of the protective strip 108. Since the organic material can cover the edges of the strip 108, there is a high probability that continuity could be established between the two portions 201-1, 201-2.To ensure a sufficient margin, the height H109 of the pillar 109 is preferably greater than 1.2 times the deposit thickness H201 of the organic layer 201, and even more preferably greater than 1.4 times, or even greater than 2 times, the deposit thickness H201 of the organic layer 201. The deposit thickness H201 is considered equal for the two portions 201-1 and 201-2 of the organic layer 201, since these two portions 201-1 and 201-2 are deposited in the same step. The deposit thickness H201 is preferably measured at a location where this thickness varies little, for example, far from the edges. The organic layer 201 preferably has a deposit thickness H201 between 100 nm and 200 nm.

[0100] The steps described above thus make it possible to form an electroluminescent display device 200. In the example of Figures 18 to 20, the device 200 comprises columns of pixels, each column of pixels being formed from a column of islands 101. The pixels are arranged on the substrate 102 and each comprises a support layer 104, a lower electrode 103, and an organic layer 201, extending continuously over the entire pixel column. In particular, considering only two pixels in the same pixel column, the device 200 comprises a trench 106 separating the two pixels and a pillar 109 disposed in this trench 106 and electrically insulating the two lower electrodes 103 of the pixels. An organic layer 201 extends over each lower electrode 103. A protective strip 108, forming a bridge joining the lower electrodes 103 of the two islands 101, and supported by the pillar 109, thus provides support for the organic layer 201, which extends along its entire length over the lower electrodes 103 of each pixel.

[0101] The different pixel columns of the device 200 are separated from each other by trenches 106.The cantilevered sections 110a, 110b of the 108 ribbon allow the organic layer to be split into two separate portions 201-1, 201-2 so that the portion 201-2 extending into the trench 106 is electrically isolated from the portion 201-1 extending over the islands 101.

[0102] To improve the device 200, a further step of depositing an additional conductive layer 204 can be carried out. This additional conductive layer 204 can form an upper electrode for the final pixels. This upper electrode is preferably transparent or semi-transparent, whether the lower electrode 103 is opaque or reflective. By "semi-transparent," we mean an element which, for at least one wavelength in the spectral band [400 nm; 1000 nm], or even [400 nm; 2000 nm], has an optical transmission coefficient of between 40% and 60%.

[0103] Figures 21 and 23 show the outcome of this additional step. The additional conductive layer 204 is made so as to have at least one portion 204-1 completely covering the first portion 201-1 of the organic layer 201. Thus, this portion 204-1 of the additional conductive layer 204 forms an upper electrode of the device 200 and in particular a common upper electrode for the island column 101. Thus, applying an electrical potential between the upper electrode 204-1 and one of the lower electrodes 103 makes it possible to apply an electric field to a part of the organic layer disposed between these two electrodes 204-1, 103. The additional conductive layer 204 is formed, for example, from a transparent conductive oxide (or TCO), or from a thin semi-transparent silver film, or from a thin semi-transparent aluminum film.

[0104] The deposition of the additional conductive layer 204 is preferably carried out anisotropically with a direction substantially perpendicular to the substrate 102. Similar to the organic layer 201, the additional conductive layer 204 is split into two distinct portions 204-1, 204-2, separated from each other. A first portion 204-1 extends continuously over the first portion 202 of the organic layer 201 and forms the upper electrode. A second portion 204-2 of the additional conductive layer 204 extends into the trench 106 separating the island columns 101, and over the second portion 203 of the organic layer 201.

[0105] In order to ensure electrical insulation between these two portions 204-1, 204-2, the deposit of the additional conductive layer 204 is carried out with a deposit thickness H204 such that the additional conductive layer 204 does not reach the protective tape 108 and in particular the overhanging parts 110 of the tape 108. For example, the sum of the deposit thickness H201 of the organic layer 201 and the deposit thickness H204 of the additional conductive layer 204 is strictly less than the height H109 of the pillar 109 supporting the protective tape 108. To ensure a sufficient margin, the height H109 of the pillar 109 is preferably greater than 1.2 times the sum of the thickness H201 of the organic layer 201 and the thickness H204 of the additional conductive layer 204, and even more preferably greater than 1.5 times, or even greater than 2 times, the sum of these thicknesses H201, H204.In other words, H109 > l,2x(H201 + H204), and preferably H109 > l,5x(H201 + H204).

[0106] In addition, the finalization of the device 200 may include the deposition of one or more encapsulation layers to protect the oxidizable materials. This could involve, for example, protecting layers made of aluminum oxide, silica, or nitride. The encapsulation layer or layers may be formed, for example, by atomic layer deposition (ALD) or by chemical vapor deposition (CVD).

[0107] Figures 12 and 13 show two examples of protective tape 108 that can be obtained at the end of the step of forming said tape 108. Figures 12 and 13 present a section made along a column of islands 101 thus showing the profile of the tape 108 for each example.

[0108] In the case of [Fig. 12], the structural element 107 underlying the ribbon 108 has a rectangular cross-section. The structural element 107 includes, in particular, two flanks 107a, 107b, each of which is in contact with one of the two islands 101 to be separated. These flanks 107a, 107b extend perpendicularly to the substrate 102 until they exceed the tops of the islands 101. The portion of the structural element 107 extending beyond the islands 101 thus has a step-like shape with sharp edges. These edges prevent the formation of the organic layer 201. Indeed, the deposition of organic material on sharp edges tends to break the resulting layer. It therefore no longer forms a continuous layer extending from one island 101 to the other. To reduce this risk, the organic layer can be formed very thick to mask the presence of sharp edges and breaks or fractures. However, an excessively thick organic layer tends to reduce the effectiveness of the resulting device.

[0109] The protective strip 108 covers the structural element 107, smoothing, at least partially, its sharp edges. The protective strip 108 is, for example, produced by lithography, notably involving a step of depositing a material. This deposit covers the sharp edges and forms a bridge overlapping the structural element 107. The free surface of this bridge is sufficiently "smooth" to allow the organic layer 201 to extend continuously, without breakage or interruption. By "smooth," it is understood that the free surface has a tangent to the substrate (also called the "slope" and represented by the symbol Al in [Fig. 12]) between -45° and 45°, and preferably between -20° and 20°, and even more preferably between -5° and 5°.

[0110] Figure 13 shows an embodiment in which the structural element 107 is modified so as to eliminate sharp edges. Thus, the ribbon 108, extending directly against the structural element 107, has a free surface extending continuously from one island 101 to the other, without any edges or discontinuities. This embodiment is the most likely to provide a bridge between the two islands, allowing the formation of a defect-free organic layer. To obtain this ribbon 108, the structural element 107 undergoes a thinning or swelling process to cause the portion of the element 107 extending beyond the islands to overhang the edge of these islands 101. This thinning or swelling step thus softens, or even eliminates, the sharp edges. The structural element 107 thus has a gentle slope, allowing for the formation of a protective strip 108, also with a gentle slope. The thinning or swelling can be achieved by heat treatment of the structural element 107.The structural element 107 is, for example, heat-treated at 200°C for 30 minutes followed by drying in order to irreversibly fix the deformation. The ribbon 108 can be formed in a second step, for example by lithography.

[0111] Figures 1 to 3 show a variant of the precursor 100 from which the display device 200 is formed. In this variant, each island 101 comprises a sacrificial layer 105 extending over the lower electrode 103. It is, for example, formed from a dielectric material such as silicon dioxide SiO2, aluminum oxide Al2O3, and preferably silicon nitride SiN. The silicon nitride SiN forms an effective stopping layer for performing a polishing step.

[0112] In the presence of sacrificial layers 105, the trench 106 is filled with the structural element 107 (as illustrated in Figures 4 to 6) so that the structural element 107 reaches the top of the sacrificial layers 105. For example, the material intended to form the structural element 107 is deposited in full slab form by filling the trenches 106 and covering the islands 101. A planarization Chemical and Physical Planarisation (CMP), stopping at the sacrificial layers 105, exposes the tops of the islands 101. Following CMP, etching the sacrificial layer 105 exposes the lower electrodes 103. This etching of the sacrificial layers 105 is preferentially performed selectively with respect to the structural element 107, stopping at the conductive layers 103. However, this etching retains a portion of the structural element 107, extending beyond the islands 101 and, in particular, the conductive layers 103.

[0113] The thickness of the sacrificial layers determines the height H73 of the structural element 107 extending beyond the lower conductive layers 103. For each island, the sacrificial layer 105 has, for example, a thickness between 10 nm and 100 nm, in order to properly ensure its role as a stop layer for a CMP step. Thus, the height H73 can be between 10 nm and 100 nm.

[0114] It is clearly advantageous that the structural element 107 does not extend beyond the lower electrodes 103. Thus, there are no seams to erase and the fabrication of the ribbon 108 is simplified. The extension of the structural element 107 beyond the lower electrodes 103 is a consequence of the etching of the sacrificial layers 105.

[0115] It is, however, possible to etch the sacrificial layers 105 in a non-selective manner with respect to the structural element 107. In this case, a greater or lesser portion of the structural element 107 is removed along with the sacrificial layers 105. When the etching rate of the structural element 107 is equal to the etching rate of the sacrificial layers 105, for example within 10%, the step of the structural element 107 (the portion protruding from the conductive layers 103) is removed along with the sacrificial layers 105. A step of reduced height may remain. However, if its height H73 is less than 30 nm, it has no effect on the formation of the organic layer 201.

[0116] In one embodiment, the conductive layer 103 is sufficiently hard to act as a stop layer for a CMP. Therefore, the sacrificial layer 105 is unnecessary, and the structural element 107 reaches the conductive layers 103 without exceeding them. The sacrificial layers 105 may also be sufficiently conductive that they do not need to be removed. They can thus be integrated into the final pixels, as if they were part of the conductive layers 103.

[0117] In Figures 4 to 9, the structural element 107 is made from an electrically insulating material. For example, silicon dioxide SiO2, silicon nitride SiN, or aluminum oxide Al2O3. Alternatively, the structural element 107 can be a polymer-based material such as a resin (particularly for a finishing or swelling step of the structural element 107). The element structural 107 is even preferentially composed solely of an electrically insulating material such as those mentioned above.

[0118] The filling is carried out, for example, by depositing the insulating material so as to completely fill the trench 106. The filling is carried out, for example, by full-plate deposition of the electrically insulating material (or polymer) followed by polishing (also called "planarization") stopping at the sacrificial layers 105 (preferably made of SiN). Before forming the protective tape 108, and assuming that the sacrificial layers 105 are insulating, said sacrificial layers 105 are preferably removed according to the procedure described above.

[0119] Figures 24 to 27 show a variant of the manufacturing process and in particular of the structural element 107. The latter is not made of a homogeneous and electrically insulating material. It comprises two materials: a first dielectric material, which provides electrical insulation between the islands; and a second material, called the "filler," which may or may not be insulating, and whose role is to fill the trench 106 to provide support for the protective tape 108. The first dielectric material extends, for example, against each of the islands separated by the structural element.

[0120] Figure 24 shows, for example, a passivation of the precursor 100 of Figures 1 to 3. The passivation layer 112 extends continuously over the islands 101 and in the trench 106 separating these islands 101. The passivation layer 112 notably covers the sacrificial layers 105 extending over the lower electrodes 103.

[0121] Figure 25 shows the backfilling of the passivated trench 106. The backfilling material 113 is deposited in full slab so as to completely fill the trench 106 and exceed its limits.

[0122] Figure 26 shows the polishing of the stack of Figure 25, stopping at the sacrificial layers 105. The filler material 113 and the passivation layer 112 outside the trench 106 are thus removed. The resulting structural element 107 then comprises: a dielectric layer, corresponding to the passivation layer 112 and lining the bottom and sides of the trench 106; and a filler material 113 filling the remainder of the trench 106.

[0123] Unlike the structural element 107 in Figures 4 to 6, the structural element 107 is not necessarily entirely electrically insulating. Indeed, the passivation layer 112 is sufficient to provide electrical insulation between the islands 101. The filling material 113 is therefore not necessarily insulating. It may, in fact, be electrically conductive. For example, it may be made of amorphous silicon or polycrystalline silicon.

[0124] The step of removing the sacrificial layers 105 is carried out selectively with respect to the structural element 107 of Figures 7 to 9. This can also be the case with the structural element 107 of [Fig. 26]. However, in a variant illustrated by [Fig. 27], the removal of the sacrificial layers 105 can be carried out selectively with respect to the filling material 113 of the structural element 107. Thus, the passivation layer 112 can be removed, leaving only the filling material 113 exposed. [Fig. 28] shows an example of a protective tape 108 covering the structural element 107 and, in particular, the filling material 113 of this element 107. In the event that the filling material 113 is electrically conductive, then the protective tape 108 is necessarily electrically insulating.

[0125] Figure 17 shows an alternative embodiment of the partial engraving of the element structural element 107. Indeed, the etching of structural element 107 can be carried out isotropically and selectively with respect to the protective tape 108 and the lower electrodes 103. Thus, the lower electrodes 103 remain intact while the exposed portions of the support layers 104 (i.e., those susceptible to isotropic etching) can also be partially etched. Following this etching, each support layer 104 then exhibits a retraction DI 14 relative to the edges 103a, 103b of the lower electrodes. Each lower electrode 103 then presents cantilevered portions 114a, 114b. These cantilevers overhang the substrate 102.

[0126] Figures 20 and 23 show the outcome of the deposition steps of the organic layer 201 and the additional conductive layer 204. Following the same principle as with the protective strips 108, the cantilevered portions 114a, 114b allow the organic layer 201 and the conductive layer 204 to be formed by splitting these layers into two distinct portions. Thus, these layers 201, 204 can be deposited on several columns of islands 101 simultaneously without any electrical contact between the columns. On the other hand, the layers 201, 204 can extend continuously over each column of islands 101. The deposit thicknesses H201, H204 of the layers 201, 204 are constrained so that, when they form a stack in a trench 106, they cannot reach the lower electrodes 103 and in particular the cantilevered parts 114.Thus, the sum of the deposit thicknesses H201, H204 is preferably strictly less than the height of the support layers 104 (the latter being normally less than the height of the pillars 109).

[0127] The display device 200 resulting from the process detailed above thus comprises several pixels, each comprising a lower electrode 103 and an organic layer 201 extending over each lower electrode 103. The device 200 is particular in that the organic layer 201 extends continuously, in a single piece, over the plurality of pixels. This is made possible by one or more protective strips 108 that bridge the pixels. The plurality of pixels may also, at a more advanced stage, have a common upper electrode 204. to all pixels, extending, like the organic layer 201, continuously and in one piece over the plurality of pixels.

[0128] The protective tape(s) 108, or even the lower electrodes 103, have cantilevered peripheral parts, making it possible to minimize the risk of manufacturing defects while relaxing one of the manufacturing constraints, namely the deposition angle of the organic material 201 and the upper electrode 204.

[0129] In the various embodiments presented, the islands 101 have distinct lower electrodes 103. However, some islands could have common lower electrodes 103. For example, in [Fig. 1], the islands 101 can be grouped by color. Islands 101 of the same color are, for example, aligned by column, that is, along the Y direction. In this case, [Fig. 1] shows three columns of pixels that can correspond to three distinct colors. At the end of the process, the upper electrode 204 can be common to several islands 101, for example, the islands in the same column. The upper electrode 204 extends, for example, continuously along the Y direction. This arrangement of pixels is called a "strip arrangement."

[0130] In a development, the lower electrode 103 can be formed to extend over several islands 101. However, in order to address each pixel distinctly, it is advantageous that the common lower electrode 103 does not connect the same islands as the common upper electrode 204. For example, the lower electrode 103 can connect pixels belonging to different columns. For example, in [Fig. 1], the islands could be connected by two lower electrodes 103 extending perpendicularly to the columns, i.e., along X. One of the lower electrodes 103 connects, for example, the three upper islands 101, while the other lower electrode 103 connects the three lower islands 101. Thus, the common lower and upper electrodes 103, 204 form a network of intersecting electrodes, generally called "cross-bar" in English, allowing the pixels to be addressed one by one.

[0131] A device 200 resulting from the method according to the invention can advantageously be integrated into a display system, such as an electronic device screen, comprising an addressing matrix. The addressing matrix is, for example, partially disposed within the substrate 102. It is then configured to address each lower electrode 103 of the pixels. It comprises, for example, electrodes extending into the substrate and opening onto the surface of the substrate 102, layering each support layer 104. The support layer 104, being conductive or comprising at least a conductive portion (such as the portion 116 of Figures 2 and 3), allows the connection between the lower electrodes 103 and the addressing matrix.

[0132] The addressing matrix can be a so-called "passive" matrix. For example, it comprises a plurality of intersecting conductive lines, each pixel being connected at the intersection of two conductive lines. However, in an advantageous development, the intersecting conductive lines can be formed by: the upper electrodes 204, extending for example along a direction (for example Y) and common to several pixels; and the lower electrodes 103, extending perpendicularly to the upper electrodes 204 (for example along X) and common to several pixels.

[0133] The addressing matrix can be an "active" matrix. It enables the formation of an AMOLED (Active Matrix Organic Light-Emitting Diode) display system. The active matrix allows each pixel to be controlled independently. It comprises a plurality of thin-film transistors (TFTs). Each TFT is connected to a lower electrode 103 of the pixel so as to control each pixel independently. In one embodiment, the upper electrodes 204 are connected to a common cathode, for example, at the edge of the matrix.

Claims

Demands

1. A method (300) for manufacturing an electroluminescent display device (200) from a precursor (100), said precursor (100) comprising a plurality of islands (101) arranged on a substrate (102), each island (101) comprising a support layer (104) extending over the substrate (102); and a conductive layer (103) extending over the support layer (104), the islands being separated in pairs by a trench (106), the method (300) comprising: a filling of each trench (106) separating the islands (101) with a structural element (107) electrically insulating the islands (101), for each trench (106), the filling being carried out until said structural element (107) reaches the top of the islands (101) separated by said trench (106); a formation of at least one protective strip (108), each protective strip (108) connecting two islands (101) to each other by overlapping the trench (102) separating said two islands (101) and covering the structural element (107) extending into the trench (106), each protective strip (108) covering, only in part, each of the two islands (101) that it connects; a partial etching of the structural element (107) in a selective manner with respect to each protective tape (108) and with respect to the conductive layers (103) of the islands (101), the partial etching comprising at least one isotropic etching phase, the partial etching being carried out so as to retain only a portion (109) of the structural element (107) disposed under each protective tape (108) and said portion (109) forming a pillar for each protective tape (108), the partial etching being further carried out so that at least a part (110a, 110b) of each protective tape (108) extends cantilevered beyond the pillar (109) which supports it;and a deposition of an organic layer (201) in an anisotropic manner at an angle substantially perpendicular to the substrate (102) resulting in two distinct and separate portions (201-1, 201-2) of the organic layer (201), of which a first portion (201-1) extends continuously over each island (101) and over each protective strip (108), and a second portion (201-2) extends over the substrate (102), a deposition thickness of the organic layer (201) being chosen so that the second portion (203) of the organic layer (201) does not reach said at least a cantilevered part (110a, 110b) of each protective strip (108).;

2. Method (300) according to claim 1, wherein the partial engraving of the structural element (107) is carried out such that the lateral deviation (DI 10) of said at least one cantilevered part (110a, 110b) of each protective strip (108) with respect to the pillar (109) which supports it is strictly greater than 100 nm.

3. Method (300) according to any one of claims 1 or 2, wherein for each trench (106), the filling is carried out until the structural element (107) exceeds the conductive layers (103) of the two islands (101) separated by said trench (106) by a height of between 10 nm and 100 nm.

4. Method (300) according to claim 3, wherein each island (101) comprises, prior to the filling of each trench (106), a sacrificial layer (105) extending over the conductive layer (103), the filling of each trench (106) with the structural element (107) being carried out so that the structural element (107) reaches the top of the sacrificial layers (105) extending over the islands (101).

5. Method (300) according to claim 4, further comprising, after filling each trench (106) and before forming each protective strip (108), an engraving of the sacrificial layer (105) of each island (101) in a selective manner with respect to the structural element (107), the engraving being carried out with a stop on said conductive layer (103) of said island (101).

6. A method (300) according to any one of claims 4 or 5, wherein, for each trench (106), the filling with the structural element (107) comprises: - a deposit of a layer of electrically insulating material so as to completely fill said trench (106); - a polishing of the layer of electrically insulating material with a stop on the sacrificial layer (105) of each island (101).

7. A method (300) according to any one of claims 4 or 5, wherein, for each trench (106), the filling with the structural element (107) comprises the following steps: - a conforming deposition of a dielectric layer in said trench (106); - a deposition of a layer of filler material on the dielectric layer so as to completely fill said trench (106); - a polishing of the dielectric layer and the filler layer with a stop on the sacrificial layer (105) of each island (101).

8. Method (300) according to claim 7, wherein the filler material is amorphous silicon or polycrystalline silicon.

9. A method (300) according to any one of claims 1 to 8, comprising, prior to the formation of each protective strip (108), a thinning or swelling of the structural element (107) so that it overflows onto a portion of the conductive layer of each island (101) by forming at least one continuous and edgeless free surface, extending from the conductive layer (103) of one of the islands (101) to the conductive layer of another island (101), each free surface having a slope, measured with respect to the substrate (102), of between -45 degrees and 45 degrees and preferably between -20 degrees and +20 degrees.

10. Method (300) according to any one of claims 1 to 9, wherein each protective tape (108) is electrically insulating.

11. A method (300) according to any one of claims 1 to 10, wherein the partial etching of the structural element (107) comprises at least one anisotropic etching phase and at least one isotropic etching phase, for example in alternation, each anisotropic etching phase being carried out with a directivity substantially perpendicular to the substrate (102).

12. A method (300) according to any one of claims 1 to 11, comprising, after deposition of the organic layer (201), an anisotropic deposition of an additional conductive layer (204) resulting in two distinct and separate portions (204-1, 204-2) of the additional conductive layer (204), of which a first portion (204-1) of the additional conductive layer (204) extends continuously over the first portion (201-1) of the organic material layer (201), and a second portion (204-2) of the additional conductive layer (204) extends over the second portion (201-2) of the organic layer (201), a thickness of deposit of the additional conductive layer (204) being chosen so that the second portion (204-2) of the additional conductive layer (204) does not reach said at least one cantilevered portion (110a, 110b) of each protective tape (108).

13. A method (300) according to any one of claims 1 to 12, wherein the partial engraving of the structural element (107) is further carried out so as to partially engrave the support layer (104) of each island (101) so that, for each island (101), at least a portion (114) of the conductive layer (103) of said island (101) extends cantilevered beyond the support layer (104) of said island (101).

14. Electroluminescent display device (200) comprising a plurality of islands (101) arranged on a substrate (102), each island comprising a support layer (104) extending over the substrate (102) and a conductive layer (103) extending over the support layer (104), the device comprising:

15.

16.

17. - at least one trench (106) separating the islets (101) two by two; - at least one protective tape (108), each protective tape (108) connecting two islands (101) to each other by overlapping the trench (102) separating said two islands (101), each protective tape (108) covering, only partially, each of the two islands (101); - at least one pillar (109) filling at least part of a trench and electrically insulating the islands (101) separated by said trench (106), each pillar (109) reaching or exceeding the top of the two islands (101) separated by said trench (106), each pillar being arranged under a protective tape (108) to support said protective tape (108) such that at least a portion (110a, 110b) of said protective tape (108) extends cantilevered beyond said pillar (109); and - an organic layer (201) having two portions (201-1, 201-2) distinct and separated from each other, of which, a first portion (201-1) extends continuously over each island (101) and over each protective strip (108), and a second portion (201-2) extends over the substrate (102) without reaching said at least one cantilevered part (110a, 110b) of each protective strip (108). Display device (200) according to claim 14, wherein the lateral deviation (DI 10) of said at least one cantilevered part (110a, 110b) of each protective strip (108) with respect to the pillar (109) which supports it is strictly greater than 100 nm. Display device (200) according to any one of claims 14 or 15, wherein said at least one pillar (109) is made from an electrically insulating material. Display device (200) according to any one of claims 14 to 16, wherein said at least one pillar (109) comprises a dielectric layer, enabling electrical isolation of the islands (101) separated by said at least one pillar (109); and a filling material, serving as a support for the protective tape (108), the

18.

19. dielectric layer of said at least one pillar separating the filling material of said at least one pillar from each island (101). Display device (200) according to any one of claims 14 to 16, wherein said at least one pillar (109) has a continuous and edgeless surface over which the protective tape (108) extends, said continuous and edgeless surface extending from the conductive layer (103) of one of the islands (101) to the conductive layer of another island (101), each continuous and edgeless surface having a slope, measured with respect to the substrate (102), of between -45 degrees and 45 degrees and preferably between -20 degrees and +20 degrees. Electroluminescent display system, comprising: - a device (200) according to any one of claims 14 to 18; and - an active addressing matrix comprising a plurality of transistors, each transistor of the plurality of transistors being connected to the conductive layer (103) of one of the islands (101) of said device (200).