Miniature light-emitting device and preparation method thereof

Abstract

The invention relates to a miniature light-emitting device and a preparation method thereof, the device comprises a light-emitting structure, the light-emitting structure comprises an epitaxial layer and a first bonding metal layer which are stacked in sequence, a first opening is formed in the first bonding metal layer, and the first opening is filled with a self-repairing material; the self-repairing material is a material which is reduced into metal in an environment with a preset temperature; the driving structure comprises a driving substrate and a second bonding metal layer which are sequentially stacked, a second opening is formed in the second bonding metal layer, the second opening is filled with a self-repairing material, and the second bonding metal layer faces the first bonding metal layer and is bonded with the first bonding metal layer.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a light-emitting structure and its preparation method. Background Technology

[0002] Micro-LED chip arrays (micro light emitting diodes) typically refer to an array of chips formed on an LED epitaxial wafer through processes such as bonding, photolithography, etching, evaporation, and dicing. The array size used in microdisplays is generally from a few millimeters to tens of millimeters. Compared with current LCD and OLED display devices, Micro-LEDs have advantages such as fast response, high color gamut, high PPI, high brightness, and low power consumption, and can be widely used in AR / VR microdisplays, wearable microdisplays, and other fields.

[0003] Currently, conventional LED epitaxy uses sapphire as a substrate. However, after LED sapphire epitaxy is bonded to IC (Integrated Circuit) wafers, the IC is prone to damage and dark cracks. Summary of the Invention

[0004] This application provides a miniature light-emitting device, which includes: The light-emitting structure includes an epitaxial layer and a first bonding metal layer stacked sequentially. The first bonding metal layer has a first opening, and the first opening is filled with a self-healing material, which is a material that is reduced to metal in an environment with a preset temperature. A driving structure includes a driving substrate and a second bonding metal layer stacked sequentially. The second bonding metal layer has a second opening, which is filled with a self-healing material. The second bonding metal layer faces the first bonding metal layer and is bonded to the first bonding metal layer.

[0005] The micro light-emitting device further includes: A buffer adhesive layer is disposed between the first bonding metal layer and the second bonding metal layer; Conductive particles are embedded in the buffer adhesive layer, with one end of the conductive particles contacting the first bonding metal layer and the other end of the conductive particles contacting the second bonding metal layer.

[0006] The first bonding metal layer includes alternating first bumps and first grooves, and the second bonding metal layer includes alternating second bumps and second grooves, wherein the first bumps and the second grooves are correspondingly disposed, and the second bumps and the first grooves are correspondingly disposed.

[0007] The first opening is located on the first protrusion, the second opening is located on the second protrusion, and the surface of the self-healing material is flush with the surfaces of the first and second protrusions.

[0008] In the first bonding metal layer, the surfaces of all the first bumps are on the same horizontal plane, and the surfaces of all the first grooves are on the same horizontal plane. In the second bonding metal layer, the surfaces of all the second bumps are on the same horizontal plane, and the surfaces of all the second grooves are on the same horizontal plane; The surface of the first protrusion is aligned and fitted with the surface of the second groove, and the surface of the second protrusion is aligned and fitted with the surface of the first groove.

[0009] The light-emitting structure further includes a first adhesion layer, which is disposed between the epitaxial layer and the first bonding metal layer. The driving structure further includes a second adhesion layer, which is disposed between the driving substrate and the second bonding metal layer.

[0010] The light-emitting structure further includes a first blocking layer, which is disposed between the first adhesive layer and the first bonding metal layer; The driving structure further includes a second barrier layer disposed between the second adhesion layer and the second bonding metal layer.

[0011] Wherein, the depth of the first opening does not penetrate the first bonded metal layer and does not extend to the surface of the first barrier layer, and the self-healing material in the first opening does not contact the first barrier layer; The depth of the second opening does not penetrate the second bonded metal layer and does not extend to the surface of the second barrier layer, and the self-healing material in the second opening does not contact the second barrier layer.

[0012] This application also provides a method for fabricating a micro light-emitting device, the method comprising: Provide an epitaxial layer; A first bonding metal layer is formed on the epitaxial layer, and a hole is made in the first bonding metal layer to obtain a first opening. A self-healing material is filled into the first opening to obtain a light-emitting chip wafer. The self-healing material is a material that is reduced to metal in an environment with a preset temperature. Provide driving substrate; A second bonding metal layer is formed on the driving substrate, and a hole is made in the second bonding metal layer to obtain a second opening. The self-healing material is then filled into the second opening to obtain a driving wafer. On the side of the first bonding metal layer away from the epitaxial layer, the light-emitting chip wafer and the driving wafer are bonded to obtain a bonding structure; The bonding structure is cut into grains to obtain a micro light-emitting device, wherein the micro light-emitting device includes a light-emitting structure and a driving structure, the light-emitting structure and the driving structure are bonded through a first bonding metal layer and a second bonding metal layer, the second bonding metal layer is oriented toward the first bonding metal layer and bonded to the first bonding metal layer.

[0013] Before bonding the light-emitting chip wafer to the driving wafer, the process further includes: A buffer adhesive layer is formed on the second bonded metal layer; A conductive particle layer is formed on the buffer adhesive layer, wherein the conductive particle layer includes conductive particles. When the light-emitting chip wafer and the driving wafer are bonded, the conductive particles are embedded in the buffer adhesive layer, one end of the conductive particles is in contact with the first bonding metal layer, and the other end of the conductive particles is in contact with the second bonding metal layer.

[0014] Wherein, after forming the first bonding metal layer on the epitaxial layer, the method further includes: The first bonding metal layer is etched to obtain alternating first bumps and first grooves, wherein the surfaces of all the first bumps are on the same horizontal plane and the surfaces of all the first grooves are on the same horizontal plane. After forming the second bonding metal layer on the driving substrate, the method further includes: The second bonding metal layer is etched to obtain alternating second bumps and second grooves, wherein the surfaces of all the second bumps are on the same horizontal plane and the surfaces of all the second grooves are on the same horizontal plane. The bonding of the light-emitting chip wafer to the driving wafer includes: The first protrusion is set to correspond with the second groove, and the second protrusion is set to correspond with the first groove, wherein the surface of the first protrusion is aligned and fitted with the surface of the second groove, and the surface of the second protrusion is aligned and fitted with the surface of the first groove.

[0015] The step of creating an opening in the first bonded metal layer to obtain a first opening, and filling the first opening with a self-healing material, includes: A hole is made in the first protrusion to obtain a first opening, and the self-healing material is filled into the first opening so that the surface of the self-healing material is flush with the surface of the first protrusion. The step of creating a hole in the second bonded metal layer to obtain a second opening, and filling the second opening with the self-healing material, includes: A hole is made in the second protrusion to obtain a second opening, and the self-healing material is filled into the second opening so that the self-healing material is flush with the surface of the second protrusion.

[0016] The formation of the first bonding metal layer on the epitaxial layer includes: A first adhesion layer is formed on the epitaxial layer; A first barrier layer is formed on the side of the first adhesion layer opposite to the epitaxial layer; The first bonding metal layer is formed on the side of the first barrier layer opposite to the first adhesive layer.

[0017] The formation of the second bonding metal layer on the driving substrate includes: A second adhesion layer is formed on the driving substrate; A second barrier layer is formed on the side of the second adhesion layer opposite to the driving substrate; The second bonding metal layer is formed on the side of the second barrier layer opposite to the second adhesion layer.

[0018] The beneficial effects of this application are as follows: The micro light-emitting device and its fabrication method provided by this application have a self-healing material filling the first opening in the first bonding metal layer of the light-emitting structure. The first opening provides a space for the self-healing material. The preset temperature environment can be a high-temperature bonding environment. During the high-temperature bonding process, the self-healing material will be reduced to metal. During this process, the self-healing material can absorb part of the stress generated by the thermal expansion difference on the light-emitting structure side through its own deformation or flow characteristics, thereby avoiding the direct and concentrated transmission of stress on the light-emitting structure side to the bonding interface and the driving substrate, and weakening the stress impact on the driving structure side.

[0019] In addition, the second opening in the second bond and the metal layer of the driving structure is also filled with self-healing material. The second opening reduces the overall rigidity of the second bonded metal layer, so that the second bonded metal layer has a certain deformation margin during thermal expansion and contraction, reducing the risk of the metal layer cracking due to thermal stress and then transferring the stress to the driving substrate. The self-healing material in the second opening and the self-healing material in the first opening form a double-sided stress buffer, which can specifically absorb the local concentrated stress on the driving structure side and avoid stress accumulation inside the driving substrate.

[0020] In addition, the self-healing material is reduced to metal in the high-temperature environment during bonding, which not only ensures the connection reliability of the bonding interface, but also weakens the total cross-interface stress between the epitaxial layer and the driving substrate through the stress absorption capacity of the self-healing materials on both sides. This achieves the dispersion and absorption of stress on both sides of the bonding layer, and blocks the damage of concentrated stress to the driving substrate from the stress transmission path. Finally, it solves the problem that the driving substrate is prone to damage and dark cracks after the light-emitting structure and the driving structure are bonded, and obtains a micro light-emitting device with a complete structure. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic cross-sectional view of the micro light-emitting device provided in the embodiments of this application; Figure 2 This is a schematic flowchart of the fabrication method of the micro light-emitting device provided in the embodiments of this application; Figure 3 This is a schematic diagram of the epitaxial layer provided in an embodiment of this application; Figure 4 This is a schematic diagram of the formation of the first bonding metal layer provided in an embodiment of this application; Figure 5 This is a schematic diagram of etching a first bump and a second groove in a first bonding metal layer, as provided in an embodiment of this application. Figure 6 This is a schematic diagram of opening a hole in the first protrusion and filling it with self-healing material, provided in an embodiment of this application; Figure 7 This is a schematic diagram of forming a second bonding metal layer on a driving substrate according to an embodiment of this application; Figure 8 This is a schematic diagram of etching a second bonding metal layer to obtain a second bump and a second groove, provided in an embodiment of this application. Figure 9 This is a schematic diagram of opening a hole in the second protrusion and filling it with self-healing material, provided in an embodiment of this application; Figure 10 This is a schematic diagram of the formation of a buffer adhesive layer and a conductive particle layer on the second bonded metal layer provided in an embodiment of this application. Detailed Implementation

[0023] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be particularly noted that the following embodiments are only used to illustrate the embodiments of this application and do not limit the scope of the embodiments of this application. Similarly, the following embodiments are only some embodiments of the embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the embodiments of this application.

[0024] When describing the structure of a component, when referring to a layer or region as being located on or above another layer or region, it can mean that it is directly above another layer or region, or that it contains other layers or regions between itself and another layer or region. Furthermore, if the component is flipped, the layer or region will be located below or beneath another layer or region. Additionally, the features, structures, or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0025] Furthermore, the directional terms mentioned in the embodiments of this application, such as [up], [down], [front], [back], [left], [right], [inner], [outer], [side], etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrating and understanding the embodiments of this application, and not for limiting the embodiments of this application. In the various drawings, structurally similar units are represented by the same reference numerals. For clarity, the various parts in the drawings are not drawn to scale. In addition, some related parts may not be shown in the drawings.

[0026] The following detailed description is based on specific embodiments. It should be noted that the embodiments of this application can be presented in various forms, and some examples will be described below.

[0027] Currently, conventional LED epitaxy uses sapphire as the substrate, which is cheaper than silicon LED epitaxy. Conventional driver ICs use silicon. When sapphire-based LED epitaxy is used for wafer bonding with silicon-based driver ICs, the thermal expansion coefficients of sapphire and silicon differ by 2 to 3 times, a significant difference that easily leads to breakage and dark cracking issues in the silicon-based IC after wafer bonding. This solution optimizes the bonding layer structure by introducing a stress-relieving layer, thereby improving the breakage and dark cracking problems of silicon-based ICs.

[0028] The following detailed description is based on specific embodiments. It should be noted that the embodiments of this application can be presented in various forms, and some examples will be described below.

[0029] Please see Figure 1 , Figure 1 This is a cross-sectional structural diagram of the micro light-emitting device provided in the embodiments of this application. For example... Figure 1As shown, the micro light-emitting device 1 includes: a light-emitting structure 100, which includes an epitaxial layer 120 and a first bonding metal layer 150 stacked sequentially, the first bonding metal layer 150 having a first opening filled with a self-healing material 500, the self-healing material 500 being a material that reduces to metal in an environment with a preset temperature; and a driving structure 200, which includes a driving substrate 210 and a second bonding metal layer 240 stacked sequentially, the second bonding metal layer 240 having a second opening filled with the self-healing material 500, wherein the second bonding metal layer 240 faces the first bonding metal layer 150 and is bonded to the first bonding metal layer 150.

[0030] The light-emitting structure is the core functional unit in a semiconductor light-emitting device used to convert electrical energy into light energy. Its core principle is based on the electro-optic effect of the PN junction in semiconductor materials. When an applied current passes through, electrons and holes recombine at the PN junction and release photons, thereby achieving light emission. In this embodiment, the light-emitting structure serves as the light-emitting end of the micro-light-emitting device and is directly bonded to the driving structure. It consists of sequentially stacked epitaxial layers and a first bonding metal layer, and is mechanically connected and electrically conductive to the driving structure through the first bonding metal layer.

[0031] In semiconductor device manufacturing, the epitaxial layer is a semiconductor material layer with a specific doping type and thickness formed on the surface of a substrate through an epitaxial growth process. Its core function is to construct the PN junction, providing the physical basis for electro-optical conversion, and it is commonly found in light-emitting devices such as LEDs and lasers. In this embodiment, the epitaxial layer is a GaN-based epitaxial layer, which is directly stacked below the sapphire substrate and in direct contact with the first bonding metal layer above it. It is one of the main sources of stress caused by the difference in thermal expansion coefficients between sapphire and silicon. The thermal expansion coefficient of sapphire is approximately... Silicon The difference can be as much as 2 to 3 times. For example, in some embodiments, the epitaxial layer 120 may include a first semiconductor layer, a light-emitting layer, and a second semiconductor layer, wherein the first semiconductor layer may be an N-type GaN layer (i.e., N-GaN), the second semiconductor layer may be a P-type GaN layer (i.e., P-GaN), and the light-emitting layer is a quantum well (QW) structure.

[0032] For example, such as Figure 1 As shown, the light-emitting structure 100 also includes a sapphire substrate 110, an epitaxial layer 120 disposed on one side of the sapphire substrate 110, and a first bonding metal layer 150 disposed on the side of the epitaxial layer opposite to the sapphire substrate 110.

[0033] The first bonding metal layer is a functional metal layer used in semiconductor wafer bonding processes to achieve mechanical connection and electrical conduction between the light-emitting structure and the driving structure. It utilizes the high conductivity, good ductility, and interfacial adhesion of the metal material to ensure the electrical performance and mechanical stability of the bonded device. Common materials need to meet the requirements of low resistance, high adhesion, and high temperature resistance. In this embodiment, the first bonding metal layer is directly stacked on top of the epitaxial layer. The material can be metals such as Ti / Cr / Pt / Ni / Ag / Au / Sn / Al / In, and a first opening is formed within the layer. This opening serves both to transmit the current from the epitaxial layer to the driving structure and to achieve stress adjustment through a self-healing material within the opening.

[0034] The first opening is created within the semiconductor metal layer using photolithography and etching processes to provide space for the metal. Simultaneously, by reducing the area of ​​the continuous region of the metal layer, the rigidity of the metal layer is reduced, improving its thermal adaptability and preventing stress concentration at the interface between the metal layer and the epitaxial layer due to thermal expansion differences. In this embodiment, the first opening is located in a designated area of ​​the first bonding metal layer. The depth of the opening does not penetrate the first bonding metal layer, and the opening size is set according to the thickness of the bonding metal layer to ensure that the self-healing material does not protrude from the surface of the metal layer after filling, thus not affecting subsequent bonding.

[0035] Self-healing materials are functional materials in the semiconductor field that can undergo physical / chemical changes under specific process conditions (such as high temperature and vacuum) to achieve stress regulation or structural repair. They absorb interfacial stress or fill micro-defects through the material's own fluidity, phase transition, or chemical reduction reaction. In this embodiment, the self-healing material uses gold nanoparticles encapsulated in an organic protective layer, which fill the first and second openings. During the high-temperature bonding process, the organic protective layer decomposes, and the gold nanoparticles are reduced to metallic gold. On the one hand, the ductility of the metal absorbs the localized stress caused by the difference in thermal expansion between sapphire and silicon; on the other hand, it forms an integrated structure with the bonding metal layer, ensuring the mechanical strength of the bonding interface.

[0036] The driving structure is a functional unit in a micro-light-emitting device that provides precise power supply and controls the operating state of the light-emitting structure. Its core principle is based on silicon-based IC semiconductor circuits, which convert externally input electrical energy into current / voltage signals that meet the requirements of the light-emitting structure, making it crucial for the device to achieve controllable light emission. In this embodiment, the driving structure serves as the power supply end and is bonded to the light-emitting structure. Its specific structure consists of a driving substrate and a second bonding metal layer stacked sequentially. The driving substrate is a silicon-based IC substrate, which is a core part that is prone to damage and dark cracks under stress. It needs to be protected by the synergistic effect of the second bonding metal layer and a self-healing material.

[0037] The driving substrate is a fundamental component in semiconductor IC manufacturing, serving as the carrier of driving circuits, providing mechanical support, and facilitating electrical interconnection. Its core principle utilizes the semiconductor properties of silicon to construct complex circuits through processes such as photolithography, etching, and deposition. Furthermore, silicon-based substrates possess excellent mechanical stability and thermal conductivity, making them the mainstream carrier for ICs. In this embodiment, the driving substrate is a silicon-based IC substrate, with a second bonding metal layer directly stacked on top and the mechanical support base for the device below. Due to the high brittleness of silicon, when subjected to concentrated stress caused by the difference in thermal expansion between sapphire and silicon, micro-cracks are prone to appear and propagate into damage or microcracks. Therefore, it is necessary to weaken the stress through openings in the second bonding metal layer and the use of self-healing materials.

[0038] The second bonding metal layer is a complementary bonding layer to the first bonding metal layer. It also utilizes the conductivity and ductility of the metal material to achieve mechanical bonding with the first bonding metal layer and to transfer the current from the driving substrate to the first bonding metal layer, ultimately supplying the light-emitting structure. In this embodiment, the second bonding metal layer is directly stacked on top of the driving substrate. The material is matched to the first bonding metal layer (e.g., Ti / Au for the first bonding metal layer and Cr / Au for the second bonding metal layer to ensure bonding compatibility). Furthermore, a second opening, corresponding to the position and size of the first opening, is formed within the layer. After being filled with self-healing material, it forms a double-sided stress buffer structure with the first bonding metal layer, preventing stress from being directly transferred to the driving substrate.

[0039] The second opening is a recessed structure with the same structure and principle as the first opening. Its core function is to absorb stress on both sides of the bonding interface through the synergistic design of the double-sided opening and the self-healing material, rather than concentrating it on one side. In this embodiment, the second opening is located in the second bonding metal layer, its position corresponds one-to-one with the first opening, its size matches the first opening, and its opening depth does not penetrate the second bonding metal layer. Through its cooperation with the first opening, it achieves bidirectional stress dispersion.

[0040] In this embodiment, the second bonding metal layer faces and bonds to the first bonding metal layer. This bonding is achieved through mechanical pressure and high temperature, causing the interface atoms of the two metal layers to diffuse and form a metallurgical bond. Simultaneously, the self-healing material is reduced to a metal at high temperature, further enhancing the mechanical strength and electrical conductivity of the bonding interface. In this embodiment, this bonding relationship integrates the light-emitting structure and the driving structure into a single device. During the bonding process, the self-healing material within the openings on both sides reacts synchronously, ensuring bonding reliability and absorbing cross-interface thermal stress through the metal's ductility, thus blocking the transmission of concentrated stress to the driving substrate along the stress transfer path.

[0041] In some implementations, such as Figure 1 As shown, the micro light-emitting device further includes: A buffer adhesive layer 300 is disposed between the first bonding metal layer 150 and the second bonding metal layer 240; Conductive particles 410 are embedded in the buffer adhesive layer 300. One end of the conductive particles 410 is in contact with the first bonding metal layer 150, and the other end of the conductive particles 410 is in contact with the second bonding metal layer 240.

[0042] The buffer adhesive layer is a functional colloidal layer used in semiconductor wafer bonding processes to absorb interfacial mechanical stress and fill minute gaps. Based on the low elastic modulus and good deformation capability of polymer colloidal materials, it absorbs localized stress at the bonding layer interface caused by differences in thermal expansion and mechanical pressure through its own elastic deformation, while simultaneously preventing surface damage caused by direct contact friction between the metal layers. It is commonly used in high-precision semiconductor bonding. In this embodiment, the buffer adhesive layer is a polymer-based functional adhesive layer, preferably an epoxy resin or acrylate film that combines insulation and thermal conductivity. Based on the self-healing materials on both sides, it further increases the stress buffering layers at the bonding interface, forming a dual stress regulation structure of metal layer self-healing and colloidal layer elastic buffering.

[0043] The buffer adhesive layer is positioned between the first bonding metal layer and the second bonding metal layer. This is a positional design based on stress transmission path optimization. The first and second bonding metal layers are the core bearing layers of the bonding interface and also the direct channels for stress transmission from the light-emitting structure side to the driving structure side. Placing the buffer adhesive layer between the two metal layers can directly intercept and absorb the contact stress between the two metal layers, preventing stress from being directly and rigidly transmitted to the driving substrate through the metal layers.

[0044] The buffer layer is formed by vacuum bonding and then heating and pre-curing the adhesive film. This process design is adapted to the high-precision manufacturing of semiconductors. Vacuum bonding can eliminate the air between the adhesive film and the metal layer, avoid the formation of air bubbles, and ensure that the adhesive film evenly covers the surface of the metal layer. The heating and pre-curing process involves heating at low temperature to partially cross-link and cure the adhesive film. This ensures that the adhesive layer has a certain degree of viscosity to fix the relative position of the two metal layers, while retaining some fluidity to prevent the adhesive layer from losing its deformability and failing to play its buffering role after it is fully cured.

[0045] In this embodiment, a buffer adhesive layer is prepared between the first bonded metal layer and the second bonded metal layer. The introduction of the buffer adhesive layer further absorbs the contact stress between the first and second bonded metal layers based on the double-sided self-healing material. Since the elastic modulus of the buffer adhesive layer is much lower than that of the metal bonded layer, when the sapphire and silicon IC generate shear stress due to the difference in thermal expansion, the adhesive layer can disperse the stress into uniform surface stress through elastic deformation, thereby reducing the stress transmitted to the silicon IC and significantly reducing the probability of IC damage and microcracks.

[0046] The conductive particles are functional particles used to achieve electrical connections between two separate conductive structures. Common forms include polymer microspheres coated with highly conductive metals, pure metal microspheres, or metal-coated ceramic microspheres. These particles must possess good conductivity, oxidation resistance, and a certain compressive strength. In this embodiment, the conductive particles must be compatible with the material properties of the buffer adhesive layer, and their particle size must match the thickness of the buffer adhesive layer to ensure they can penetrate the layer and achieve conductivity.

[0047] In this process, when embedding conductive particles into the buffer adhesive layer, a conductive particle layer can be prepared first on the buffer adhesive layer. Then, during the bonding process, pressure is used to embed the conductive particles from the conductive particle layer into the buffer adhesive layer. The conductive particle layer is formed by vacuum-applying and pre-curing a conductive adhesive film, similar to the formation method of the buffer adhesive layer. However, it is necessary to consider the uniformity of the conductive particle dispersion. Vacuum application can eliminate air between the adhesive film and the buffer adhesive layer, avoiding air bubbles that cause uneven distribution of conductive particles and ensuring that the particles are evenly distributed within the adhesive film. Pre-curing involves cross-linking the adhesive base at a low temperature, which both fixes the position of the conductive particles and retains the fluidity of the adhesive base. Under the bonding pressure, the conductive particles in the conductive particle layer will form a tight metal contact with the surface of the first bonded metal layer. At the same time, through the deformation of the buffer adhesive layer, the particles will indirectly contact the second bonded metal layer, ultimately constructing a complete current path between the second bonded metal layer, the buffer adhesive layer, the conductive particle layer, the first bonded metal layer, and the epitaxial layer.

[0048] The purpose of embedding conductive particles in the adhesive layer is to restrict the displacement of the conductive particles through the adhesive force of the adhesive layer, preventing the particles from shifting or agglomerating during device fabrication or use, which could lead to interruption of the conductive path. In this embodiment, after the conductive particles are embedded in the buffer adhesive layer, a stable composite structure of the adhesive layer and particles can be formed in the buffer adhesive layer, ensuring that the particles remain in the preset position during bonding and subsequent use, and do not detach from the connection path of the two bonded metal layers.

[0049] In this process, the conductive particles need to form direct physical contact with the two conductive structures to be connected in order to build an effective conductive path, ensure that a stable current path is formed between the first bonding metal layer and the second bonding metal layer, and ensure the normal electrical performance of the micro light-emitting device.

[0050] In this embodiment, conductive particles are embedded in the buffer adhesive layer and their two ends are in contact with the first and second bonding metal layers, respectively. This not only buffers the stress but also creates a stable conductive path between the light-emitting structure and the driving structure, preventing the device's electrical performance from failing due to the addition of the buffer adhesive layer and ensuring that the micro light-emitting device can normally receive the driving current and emit light.

[0051] In some implementations, such as Figure 1As shown, the first bonding metal layer 150 includes alternating first bumps and first grooves, and the second bonding metal layer 240 includes alternating second bumps and second grooves. The first bumps are correspondingly disposed to the second grooves, and the second bumps are correspondingly disposed to the first grooves.

[0052] The first bonding metal layer features alternating bumps and grooves. These bumps and grooves can be formed on the planar metal layer using photolithography and etching processes to create a three-dimensional structure. The alternating arrangement refers to the periodic alternation of the bumps and grooves along the metal layer surface, rather than a random distribution. From a material perspective, both the bumps and grooves are part of the first bonding metal layer, their convex and concave shapes formed only by differences in etching depth. The bumps are the un-etched metal areas, responsible for precise contact with the second bonding metal layer and current transmission. The grooves are selectively etched recessed areas, primarily used to accommodate the buffer adhesive layer that flows during bonding, preventing adhesive buildup on the metal layer surface and thus ensuring good contact. In semiconductor processes, this structure improves the mechanical bonding strength of the bonding interface and provides dedicated space for the buffer adhesive layer, preventing it from affecting the electrical conductivity between the metal layers.

[0053] The second bonding metal layer features alternating second bumps and second grooves, a complementary design perfectly adapted to the convex and concave structure of the first bonding metal layer. Its principle and structure are identical to the first bump / groove, but its size and distribution period must precisely match the first bonding metal layer. Positionally, the second bumps and second grooves are also periodically distributed along the surface of the second bonding metal layer, with the second bumps corresponding to the positions of the first grooves and vice versa, forming a pre-aligned structure of convex and concave interlocking. This design reduces alignment difficulty in semiconductor bonding while increasing the contact area between metal layers. Materially, the second bumps and second grooves are also part of the second bonding metal layer (e.g., Cr / Au), formed using the same IBE etching process, ensuring structural compatibility with the first bonding metal layer.

[0054] The first protrusion and the second groove are set in a one-to-one correspondence, and the second protrusion and the first groove are set in a one-to-one correspondence. Through the precise fitting of the protrusion and the groove, the first and second bonding metal layers can achieve offset contact. In semiconductor bonding, the alignment deviation between metal layers can lead to poor current transmission path and even local stress concentration. The one-to-one corresponding fitting structure can control the alignment deviation at the micrometer level. At the same time, the bonding pressure is dispersed by the shape of the protrusion embedded in the groove.

[0055] During bonding, the buffer adhesive layer is squeezed into the first and second grooves. After bonding, the buffer adhesive layer fills the first and second grooves. After pre-curing by heat, the buffer adhesive layer retains some fluidity. When pressure is applied by the bonding machine, the buffer adhesive layer is squeezed from the contact area of ​​the first and second bonded metal layers into the groove, rather than accumulating on the surface of the planar metal layer. As the bonding pressure continues to be applied, the adhesive layer fills the entire groove. After bonding is completed, the adhesive layer in the groove is flush with the surface of the protrusion, forming a smooth interface where the protrusion and adhesive layer are integrated. This process utilizes the space of the groove to accommodate the adhesive layer and eliminates the gaps between the protrusions and concavities on the surface of the metal layer by filling the groove with the adhesive layer, avoiding local stress concentration caused by gaps in subsequent processes.

[0056] In this embodiment, the alternating bumps and concave shapes of the first and second bonding metal layers and their one-to-one interlocking structure significantly improve the mechanical stability of the bonding interface. Compared with planar metal layer bonding, the bump-concave interlocking increases the contact area, and the interlocking shape can resist the shear force generated by thermal cycling, avoiding indirect damage to the silicon-based IC caused by bonding interface separation.

[0057] In some implementations, such as Figure 1 As shown, the first opening is disposed on the first protrusion, the second opening is disposed on the second protrusion, and the surface of the self-healing material 500 is flush with the surface of the first protrusion and the surface of the second protrusion.

[0058] In the bump and groove interlocking structure, the first bump is the core area where the first and second bonding metal layers directly contact and transmit pressure and current. The mechanical pressure during bonding and the shear stress generated by the difference in thermal expansion between sapphire and silicon will mainly concentrate at the bump. If the opening is located in the groove or a non-bump area, it cannot directly act on the stress concentration source, resulting in low stress absorption efficiency. In this embodiment, the first opening is located on the first bump, so that the self-healing material filling is directly at the stress concentration point. During high-temperature bonding, after the self-healing material is reduced to metal, it can directly absorb the concentrated stress at the bump through its own ductility, weakening the load transmitted to the driving substrate from the stress source.

[0059] The second opening, located on the second bump, is a complementary design that creates symmetrical stress absorption with the first opening. The second and first bumps are opposing stress areas during bonding, and both bear dual stress from bonding pressure and thermal expansion differences. If the opening were only on the first bump, the stress on the second bump would still be transmitted to the silicon IC through the second bonding metal layer, failing to achieve dual-sided stress control. In this embodiment, the second and first openings correspond one-to-one, allowing the self-healing material to be symmetrically distributed on both sides of the bonding interface. The self-healing material on both sides can simultaneously absorb the concentrated stress of their respective bumps, forming a bidirectional stress buffer and preventing localized damage to the silicon IC caused by excessive stress on one side. In this design, the surface of the self-healing material is flush with the surfaces of the first and second protrusions, respectively. If the surface of the self-healing material is higher than the surface of the protrusion, the protrusion will not be able to make tight contact with the opposing protrusion / groove, resulting in a loose connection, or even cracking of the protrusion due to excessive local pressure at the protrusion. If the surface of the self-healing material is lower than the surface of the protrusion, a depression will be formed, causing the buffer adhesive layer to overfill the depression, resulting in gaps at the interface after bonding. In this embodiment, this flush design is achieved by precisely controlling the opening depth and the quantitative filling of the self-healing material, ensuring the overall flatness of the protrusion surface. This ensures both the tight fit between the first and second protrusions and the second and first protrusions, and avoids the self-healing material affecting the electrical conductivity between the metal layers.

[0060] In some implementations, such as Figure 1 As shown, in the first bonding metal layer 150, the surfaces of all the first bumps are on the same horizontal plane, and the surfaces of all the first grooves are on the same horizontal plane. In the second bonding metal layer 240, the surfaces of all the second bumps are on the same horizontal plane, and the surfaces of all the second grooves are on the same horizontal plane; The surface of the first protrusion is aligned and fitted with the surface of the second groove, and the surface of the second protrusion is aligned and fitted with the surface of the first groove.

[0061] In the first bonding metal layer, the surfaces of all the first bumps are on the same horizontal plane, and the surfaces of all the first grooves are on the same horizontal plane. If the surfaces of the first bumps are not of equal height, the pressure will be concentrated on the higher bumps during bonding, causing the silicon-based IC below to break due to stress overload. If the surface of the first groove is not flat, the buffer adhesive layer will accumulate in the depressions and be empty in the protrusions when filling, resulting in uneven adhesive layer thickness. When the sapphire substrate is subsequently lifted by laser, the uneven adhesive layer will cause stress imbalance in the GaN epitaxial layer, indirectly transferring the stress to the silicon-based IC.

[0062] In this process, the surface of the first protrusion is aligned and fitted with the surface of the second groove, and the surface of the second protrusion is aligned and fitted with the surface of the first groove. The alignment and fitting not only requires the protrusion and groove to be aligned, but also requires the surfaces to be in close contact: from an electrical point of view, close contact can ensure a stable current transmission path and reduce local heat generation; from a mechanical point of view, close contact allows the bonding pressure to be evenly distributed throughout the metal layer through the interface between the protrusion and the groove, rather than being concentrated in a local area.

[0063] In some implementations, such as Figure 1 As shown, the light-emitting structure 100 further includes a first adhesion layer 130, which is disposed between the epitaxial layer 120 and the first bonding metal layer 150. The driving structure 200 further includes a second adhesion layer 220, which is disposed between the driving substrate 210 and the second bonding metal layer 240.

[0064] The first adhesion layer is a transition layer used in the semiconductor metal layer deposition process to improve the interfacial bonding strength between the epitaxial layer and the first bonding metal layer, thus solving the problem of insufficient adhesion between heterogeneous materials. The epitaxial layer is usually a GaN-based semiconductor material, while the first bonding metal layer can be a highly conductive metal such as Au or Ag. Due to differences in their crystal structure and surface energy, direct stacking of these two materials can easily lead to interlayer delamination due to thermal cycling or mechanical stress. In contrast, the first adhesion layer can be made of metals such as Ti, Cr, or Pt, which have good interfacial wettability and chemical bonding ability, enabling the construction of a stable semiconductor-metal transition interface between the two materials.

[0065] In this process, the adhesion layer needs to be in direct contact with the two heterogeneous materials to be bonded in order to function through atomic diffusion or chemical bonding. If it deviates from this position, it cannot form an effective bond with the epitaxial layer and loses its adhesion function. In this embodiment, the first adhesion layer is in close contact with both the upper surface of the GaN epitaxial layer and the lower surface of the first bonding metal layer. On the one hand, it penetrates the extremely thin oxide layer that may exist on the surface of the epitaxial layer and forms a stable connection with the GaN body; on the other hand, it forms an intermetallic compound with the first bonding metal layer, further improving the overall interlayer adhesion and reducing the stress risk caused by interlayer peeling from the source of structural connection.

[0066] The material of the first adhesion layer can be selected from at least one of Ti, Cr, Pt, Ni, Ag, Au, Sn, Al, and In. Different materials are suitable for different epitaxial layer characteristics: Ti and Cr can form strong chemical bonds with GaN and are suitable for GaN-based epitaxial layers; Pt and Ni have excellent corrosion resistance and can avoid the decrease in adhesion caused by oxidation of the adhesion layer during the bonding process; Al and In have low melting points and are suitable for low-temperature bonding processes.

[0067] The second adhesion layer is a transition layer that complements the first adhesion layer. It solves the interfacial adhesion problem between the driving substrate and the second bonding metal layer. The driving substrate is a silicon-based IC substrate, and a natural oxide layer easily forms on the silicon surface. This oxide layer hinders the direct bonding between silicon and metal. The second adhesion layer can be made of metals such as Ti and Cr, which can penetrate the silicon dioxide layer to form a stable bond with the silicon substrate. At the same time, it forms a metallic bond with the second bonding metal layer, eliminating the negative impact of the oxide layer on adhesion.

[0068] In this embodiment, a first adhesion layer is provided between the epitaxial layer and the first bonding metal layer. The first adhesion layer significantly improves the interfacial adhesion between the GaN epitaxial layer and the first bonding metal layer, effectively avoiding localized stress caused by interlayer peeling during thermal cycling, and reducing the breakage rate of silicon-based ICs caused by peeling. A second adhesion layer is provided between the driving substrate and the second bonding metal layer. The second adhesion layer eliminates the negative impact of the silicon dioxide layer on the silicon substrate surface on adhesion. The adhesion is improved after adding the adhesion layer, avoiding direct stress on the silicon-based IC caused by peeling of the second bonding metal layer.

[0069] In some implementations, such as Figure 1 As shown, the light-emitting structure 100 further includes a first blocking layer 140, which is disposed between the first adhesion layer 130 and the first bonding metal layer 150. The drive structure 200 further includes a second barrier layer 230, which is disposed between the second adhesion layer 220 and the second bonding metal layer 240.

[0070] In a semiconductor multilayer metal structure, the first barrier layer is a functional transition layer used to suppress the interdiffusion of metal atoms between the first adhesion layer and the first bonded metal layer. Due to the low diffusion coefficient of metallic materials, during high-temperature bonding or long-term device use, atoms in the first adhesion layer and the first bonded metal layer are prone to interdiffusion due to thermal motion, forming intermetallic compounds. This leads to increased resistance and decreased mechanical strength of the bonded metal layer, and may even cause interlayer delamination. The first barrier layer can be made of metals such as Pt, Ni, and Cr, which have extremely low atomic diffusion coefficients, effectively blocking atomic diffusion paths and maintaining the stability of the metal layer structure and performance.

[0071] In this embodiment, the first adhesion layer and the first bonded metal layer are the main interface where atomic interdiffusion occurs. Placing the barrier layer between them directly intercepts the diffusing atoms, preventing diffusion from extending to outer layers. If the position is deviated from this point, it cannot block the direct diffusion between the adhesion layer and the bonded metal layer, thus losing its barrier function. In this embodiment, the position ensures that the first barrier layer is in close contact with both the first adhesion layer and the first bonded metal layer. This not only blocks interdiffusion through its own low diffusion characteristics but also avoids introducing new interface defects due to its good compatibility with the metals on both sides, ensuring that the interlayer adhesion is not affected.

[0072] The material of the first barrier layer can be selected from at least one of Ti, Cr, Pt, Ni, Ag, Au, Sn, Al, and In. Different materials are suitable for different metal layer combinations: Pt and Ni have the best anti-diffusion performance and are the first choice to block the interdiffusion of Au and Ti / Cr; Cr has the second best anti-diffusion performance, but has better compatibility with GaN epitaxial layers; although Ti has a higher diffusion coefficient than Pt, it is low in cost and easy to form films, making it suitable for cost-sensitive scenarios.

[0073] The second barrier layer complements the first barrier layer, serving as a transition layer to suppress atomic interdiffusion between the second adhesion layer and the second bonding metal layer. It prioritizes the protection of the silicon-based IC substrate. Atomic interdiffusion between the second adhesion layer and the second bonding metal layer not only leads to performance degradation of the bonding metal layer but can also allow diffused metal atoms to penetrate into the circuit regions of the silicon-based IC, causing circuit leakage, threshold voltage drift, and other failures. The second barrier layer can be made of metals such as Pt and Ni, which can block atomic diffusion towards the silicon substrate through their low diffusion characteristics, while also possessing good chemical stability to avoid contaminating the silicon-based circuitry.

[0074] In some implementations, such as Figure 1 As shown, the depth of the first opening does not penetrate the first bonded metal layer 150 and does not extend to the surface of the first barrier layer 140, and the self-healing material 500 in the first opening does not contact the first barrier layer 140. The depth of the second opening does not penetrate the second bonded metal layer 240, nor does it extend to the surface of the second barrier layer 230, and the self-healing material 500 in the second opening does not contact the second barrier layer 230.

[0075] In this device, the first bonding metal layer serves a dual function of electrical conduction and mechanical connection. If the opening depth penetrates the first bonding metal layer, it will cause a fractured gap in the metal layer: on the one hand, the current transmission path is cut off; on the other hand, the mechanical load-bearing capacity is significantly reduced. In this embodiment, the opening depth needs to be controlled within a range less than the total thickness of the metal layer to ensure that the metal layer maintains a continuous layered structure and does not damage its conduction and load-bearing functions.

[0076] The first barrier layer functions to block atomic interdiffusion between the first adhesion layer and the first bonded metal layer. If the opening extends to the surface of the barrier layer, the reduced gold metal from the self-healing material will directly contact the barrier layer. Gold and barrier layer metals such as Pt / Ni are prone to interdiffusion at high temperatures, causing the barrier layer's atomic diffusion barrier function to fail. This leads to interdiffusion between the first adhesion layer and the first bonded metal layer, ultimately resulting in increased metal layer resistance and decreased mechanical strength. Furthermore, contact between the self-healing material and the barrier layer may introduce impurities, contaminating the barrier layer interface and further weakening its anti-diffusion capability.

[0077] As can be seen from the above, in the micro light-emitting device provided in the embodiments of this application, the first opening in the first bonding metal layer of the light-emitting structure is filled with a self-healing material. The first opening provides a space for the self-healing material. The preset temperature environment can be a high-temperature bonding environment. During the high-temperature bonding process, the self-healing material will be reduced to metal. During this process, the self-healing material can absorb part of the stress generated by the thermal expansion difference on the light-emitting structure side through its own deformation or flow characteristics, thereby avoiding the stress on the light-emitting structure side from being directly and concentratedly transmitted to the bonding interface and the driving substrate, and weakening the stress impact on the driving structure side.

[0078] In addition, the second opening in the second bond and the metal layer of the driving structure is also filled with self-healing material. The second opening reduces the overall rigidity of the second bonded metal layer, so that the second bonded metal layer has a certain deformation margin during thermal expansion and contraction, reducing the risk of the metal layer cracking due to thermal stress and then transferring the stress to the driving substrate. The self-healing material in the second opening and the self-healing material in the first opening form a double-sided stress buffer, which can specifically absorb the local concentrated stress on the driving structure side and avoid stress accumulation inside the driving substrate.

[0079] In addition, the self-healing material is reduced to metal in the high-temperature environment during bonding, which not only ensures the connection reliability of the bonding interface, but also weakens the total cross-interface stress between the epitaxial layer and the driving substrate through the stress absorption capacity of the self-healing materials on both sides. This achieves the dispersion and absorption of stress on both sides of the bonding layer, and blocks the damage of concentrated stress to the driving substrate from the stress transmission path. Finally, it solves the problem that the driving substrate is prone to damage and dark cracks after the light-emitting structure and the driving structure are bonded, and obtains a micro light-emitting device with a complete structure.

[0080] Please see Figure 2 , Figure 2 This is a schematic flowchart illustrating the fabrication method of the micro-light-emitting device provided in this application embodiment. This embodiment uses the formation of a micro-light-emitting device according to any of the above embodiments as an example to illustrate the fabrication method. The specific process of the fabrication method of the micro-light-emitting device can be as follows: Step S21: Provide an epitaxial layer.

[0081] Step S22: A first bonding metal layer is formed on the epitaxial layer, a hole is made in the first bonding metal layer to obtain a first opening, and a self-healing material is filled in the first opening to obtain a light-emitting chip wafer. The self-healing material is a material that is reduced to metal in an environment with a preset temperature.

[0082] In this context, wafer-level structure refers to an overall structure containing a large number of arrayed chip units fabricated on a large-size substrate. It can be mass-produced through wafer-level processes, improving production efficiency. In this embodiment, the light-emitting chip wafer is a complete light-emitting wafer formed after epitaxial layer fabrication, first bonding metal layer formation, aperture opening, and self-healing material filling. Its surface contains hundreds or thousands of arrayed light-emitting unit basic structures, providing a wafer-level carrier for subsequent bonding with the driving wafer and mass dicing.

[0083] Step S23: Provide a driving substrate.

[0084] Step S24: A second bonding metal layer is formed on the driving substrate, a hole is made in the second bonding metal layer to obtain a second opening, and the self-healing material is filled into the second opening to obtain a driving wafer.

[0085] The driver wafer and the light-emitting chip wafer share the same wafer-level design logic, forming a complete driver-side wafer based on the driver substrate after the formation of a second bonding metal layer, opening, and filling with self-healing material. In this embodiment, the surface of the driver wafer contains hundreds or thousands of driver unit structures corresponding to the light-emitting chip wafer array. Their size must match that of the light-emitting chip wafer to achieve wafer-level overall bonding and improve production efficiency.

[0086] Step S25: On the side of the first bonding metal layer away from the epitaxial layer, the light-emitting chip wafer and the driving wafer are bonded to obtain a bonding structure.

[0087] In this context, a bonding structure refers to the connection of two or more wafers into an inseparable whole structure through wafer bonding technology, enabling the integration of wafers with different functions. In this embodiment, the bonding structure is a composite of a light-emitting chip wafer and a driver wafer bonded together by first and second bonding metal layers, already possessing the complete functional foundation for both light emission and driving.

[0088] Step S26: Cut the bonding structure into grains to obtain a micro light-emitting device, wherein the micro light-emitting device includes a light-emitting structure and a driving structure, the light-emitting structure and the driving structure are bonded through a first bonding metal layer and a second bonding metal layer, the second bonding metal layer is oriented toward the first bonding metal layer and bonded to the first bonding metal layer.

[0089] In this context, a die refers to the smallest unit containing the complete functionality of a single device, obtained by dividing the wafer-level bonding structure through a dicing process. Dies can range in size from tens to hundreds of micrometers. In this embodiment, the die is an unpackaged unit of a micro-light-emitting device, already possessing complete light-emitting and driving functions. Subsequent packaging is all that is needed to become the final product.

[0090] For wafer-level bonding structures, a high-precision dicing method is required to avoid stress during dicing that could damage the silicon-based IC. In this embodiment, the dicing is performed according to a preset array spacing to ensure that each die contains a light-emitting unit and a driving unit. The diced die is then a miniature light-emitting device that can be subsequently packaged, realizing the transformation from the wafer level to the device level.

[0091] In some embodiments, before bonding the light-emitting chip wafer to the driving wafer, the method further includes: A buffer adhesive layer is formed on the second bonded metal layer; A conductive particle layer is formed on the buffer adhesive layer, wherein the conductive particle layer includes conductive particles. When the light-emitting chip wafer and the driving wafer are bonded, the conductive particles are embedded in the buffer adhesive layer, one end of the conductive particles is in contact with the first bonding metal layer, and the other end of the conductive particles is in contact with the second bonding metal layer.

[0092] In some embodiments, after forming the first bonding metal layer on the epitaxial layer, the method further includes: The first bonding metal layer is etched to obtain alternating first bumps and first grooves, wherein the surfaces of all the first bumps are on the same horizontal plane and the surfaces of all the first grooves are on the same horizontal plane. After forming the second bonding metal layer on the driving substrate, the method further includes: The second bonding metal layer is etched to obtain alternating second bumps and second grooves, wherein the surfaces of all the second bumps are on the same horizontal plane and the surfaces of all the second grooves are on the same horizontal plane. The bonding of the light-emitting chip wafer to the driving wafer includes: The first protrusion is set to correspond with the second groove, and the second protrusion is set to correspond with the first groove, wherein the surface of the first protrusion is aligned and fitted with the surface of the second groove, and the surface of the second protrusion is aligned and fitted with the surface of the first groove.

[0093] In some embodiments, the step of creating an opening in the first bonded metal layer and filling the opening with a self-healing material includes: A hole is made in the first protrusion to obtain a first opening, and the self-healing material is filled into the first opening so that the surface of the self-healing material is flush with the surface of the first protrusion. The step of creating a hole in the second bonded metal layer to obtain a second opening, and filling the second opening with the self-healing material, includes: A hole is made in the second protrusion to obtain a second opening, and the self-healing material is filled into the second opening so that the self-healing material is flush with the surface of the second protrusion.

[0094] In some embodiments, forming the first bonding metal layer on the epitaxial layer includes: forming a first adhesion layer on the epitaxial layer; A first barrier layer is formed on the side of the first adhesion layer opposite to the epitaxial layer; The first bonding metal layer is formed on the side of the first barrier layer opposite to the first adhesive layer.

[0095] In some embodiments, forming a second bonding metal layer on the driving substrate includes: A second adhesion layer is formed on the driving substrate; A second barrier layer is formed on the side of the second adhesion layer opposite to the driving substrate; The second bonding metal layer is formed on the side of the second barrier layer opposite to the second adhesion layer.

[0096] For example, see Figure 3 , Figure 3 This is a schematic diagram of the epitaxial layer provided in the embodiments of this application. Figure 3 The device includes a sapphire substrate 110 and an epitaxial layer 120. The epitaxial layer 120 is disposed on one side of the sapphire substrate 110 and can be grown on the sapphire substrate 110 using MOCVD process. The epitaxial layer 120 includes an N-type GaN layer, an InGaN / GaN quantum well layer, and a P-type GaN layer.

[0097] For example, see Figure 4 , Figure 4 This is a schematic diagram of the formation of the first bonding metal layer provided in the embodiments of this application. Figure 4First, the sapphire substrate 110 and the epitaxial layer 120 are fixed on the stage of the electron beam evaporation equipment, and the environment is evacuated. Then, high-purity Ti is selected as the target material, and the electron beam power and evaporation rate are set to deposit a Ti film on the surface of the P-type GaN layer of the epitaxial layer 120 to obtain the first adhesion layer 130. Then, while keeping the vacuum level of the electron beam evaporation equipment constant, the target material is changed to high-purity Pt, and the electron beam power and evaporation rate are adjusted to deposit a Pt film on the surface of the first adhesion layer 130 away from the epitaxial layer 120 to obtain the first barrier layer 140. Finally, the target material is changed to high-purity Au, and the electron beam power and evaporation rate are adjusted to deposit an Au film on the surface of the first barrier layer 140 away from the first adhesion layer 130 to obtain the first bonding metal layer 150.

[0098] For example, see Figure 5 , Figure 5 This is a schematic diagram of etching a first bump and a second groove in a first bonding metal layer, as provided in an embodiment of this application. Figure 5 In this process, the first bonding metal layer 150 can be processed as follows: a positive photoresist is coated on the side of the first bonding metal layer 150 away from the first barrier layer 140, exposed through a mask, and the photoresist in the bump area is retained after development; an ion beam etching process is used to etch and remove the photoresist to obtain the first bumps and the first grooves distributed in alternating phases, and the top surfaces of all the first bumps are on the same horizontal plane, and the bottom surfaces of all the first grooves are on the same horizontal plane.

[0099] For example, see Figure 6 , Figure 6 This is a schematic diagram of opening a hole in the first protrusion and filling it with self-healing material, provided in an embodiment of this application. Figure 6 In this process, high-precision positive photoresist is coated on the surface of the first bump. A mask with an opening pattern is used to perform overlay exposure with the edge of the first bump as a reference. After development, only the photoresist in the opening area of ​​the first bump surface is retained, exposing the Au layer to be etched. Reactive ion etching is used to etch and remove the photoresist to obtain the first opening. Silicone resin-coated gold nanoparticles are selected as self-healing materials. The materials are injected into the first opening using a high-precision dispensing machine. Then, a low-temperature soft polishing process is used to polish and remove excess materials, making the surface of the self-healing material flush with the plane of the first bump surface.

[0100] For example, see Figure 7 , Figure 7 This is a schematic diagram of forming a second bonding metal layer on a driving substrate according to an embodiment of this application. Figure 7In this process, the driving substrate 210 is fixed on the stage of the magnetron sputtering equipment. The environment is evacuated, and the oil and impurities on the driving substrate 210 are first removed by Ar plasma cleaning. A high-purity Cr target is used to deposit a Cr film on the surface of the driving substrate 210 to obtain the second adhesion layer 220. Keeping the vacuum level of the magnetron sputtering equipment constant, the target is changed to high-purity Ni, and a Ni film is deposited on the surface of the second adhesion layer 220 away from the driving substrate 210 to obtain the second barrier layer 230. The target is changed to high-purity Au, the sputtering power is adjusted, and an Au film is deposited on the surface of the second barrier layer 230 away from the second adhesion layer 220 to obtain the second bonding metal layer 240.

[0101] For example, see Figure 8 , Figure 8 This is a schematic diagram of etching a second bonding metal layer to obtain a second bump and a second groove, as provided in an embodiment of this application. Figure 8 In this process, the second bonding metal layer 240 can be operated as follows: the mask pattern of the second bonding metal layer 240 is matched with the first bonding metal layer 150; the second bonding metal layer 240 is dry etched to obtain alternating second bumps and second grooves, and the top surface of the second bumps and the bottom surface of the second groove are flush.

[0102] For example, see Figure 9 , Figure 9 This is a schematic diagram of opening a hole in the second protrusion and filling it with self-healing material, provided in an embodiment of this application. Figure 9 In the process, photoresist is coated on the surface of the second bump on the driving side. Using the same aperture pattern mask as the first bump, the second bump edge is used as a reference for overlay exposure. After development, the Au layer to be etched is exposed. The second bump is etched using the same etching parameters as the first bump to obtain the second opening. Repair material is injected into the second opening. Since there are circuits on the surface of the silicon-based IC on the driving side, low-temperature plasma planarization is used to remove the protruding material. Finally, the surface of the self-repairing material is flush with the surface of the second bump.

[0103] For example, see Figure 10 , Figure 10 This is a schematic diagram of the formation of a buffer adhesive layer and a conductive particle layer on the second bonded metal layer provided in an embodiment of this application. Figure 10In this process, a high-temperature resistant modified epoxy resin film is selected as the material for the buffer layer 300. The driver wafer is fixed on the stage of a vacuum bonding machine, the environment is evacuated, and the modified epoxy resin film is flatly covered on the surface of the second bonding metal layer 240. After bonding, the driver wafer is transferred to an oven for pre-curing, so that the modified epoxy resin film and the second bonding metal layer 240 are tightly bonded, and the film retains a certain elasticity, thus obtaining the buffer layer 300. Then, a conductive film containing Au-plated polystyrene microspheres (i.e., conductive particles 410) is selected as the conductive particle layer 400. The conductive film is also covered on the surface of the buffer layer 300 using a vacuum bonding machine to ensure that the conductive particles 410 are evenly distributed. Then, it is placed in an oven again for pre-curing to form the conductive particle layer 400 covering the buffer layer 300.

[0104] Finally, the bonding surface of the light-emitting chip wafer is aligned with the conductive particle layer 400 of the driving wafer. After alignment using an alignment machine, it is placed in a vacuum thermosetting bonding machine. During bonding, pressure causes the conductive particles 410 to be completely embedded in the buffer adhesive layer 300. One end of the conductive particle 410 penetrates the buffer adhesive layer 300 and makes close contact with the Au surface of the second bonding metal layer 240, while the other end makes close contact with the Au surface of the first bonding metal layer 150. Simultaneously, the self-healing material is reduced to metallic gold. Subsequently, the bonding structure is cut using an ultraviolet laser to obtain the following... Figure 1 The micro-light-emitting device shown has a chip that simultaneously provides stress buffering and stable electrical connection functions.

[0105] As can be seen from the above, in the fabrication method of the micro light-emitting device provided in this application embodiment, the first opening in the first bonding metal layer of the light-emitting structure is filled with a self-healing material. The first opening provides a space for the self-healing material. The preset temperature environment can be a high-temperature bonding environment. During the high-temperature bonding process, the self-healing material will be reduced to metal. During this process, the self-healing material can absorb part of the stress generated by the thermal expansion difference on the light-emitting structure side through its own deformation or flow characteristics, thereby avoiding the stress on the light-emitting structure side from being directly and concentratedly transmitted to the bonding interface and the driving substrate, and weakening the stress impact on the driving structure side.

[0106] In addition, the second opening in the second bond and the metal layer of the driving structure is also filled with self-healing material. The second opening reduces the overall rigidity of the second bonded metal layer, so that the second bonded metal layer has a certain deformation margin during thermal expansion and contraction, reducing the risk of the metal layer cracking due to thermal stress and then transferring the stress to the driving substrate. The self-healing material in the second opening and the self-healing material in the first opening form a double-sided stress buffer, which can specifically absorb the local concentrated stress on the driving structure side and avoid stress accumulation inside the driving substrate.

[0107] In addition, the self-healing material is reduced to metal in the high-temperature environment during bonding, which not only ensures the connection reliability of the bonding interface, but also weakens the total cross-interface stress between the epitaxial layer and the driving substrate through the stress absorption capacity of the self-healing materials on both sides. This achieves the dispersion and absorption of stress on both sides of the bonding layer, and blocks the damage of concentrated stress to the driving substrate from the stress transmission path. Finally, it solves the problem that the driving substrate is prone to damage and dark cracks after the light-emitting structure and the driving structure are bonded, and obtains a micro light-emitting device with a complete structure.

[0108] In some examples, the aforementioned micro light-emitting device 1 can be applied not only to the projection part of electronic devices such as optical projection and head-up display (HUD), but also to the display part of electronic devices, such as smartphones, smartwatches, laptops, tablets, dashcams, navigators, head-mounted devices, and any other devices with a display screen. It can also be applied to the lighting part of electronic devices, such as vehicles, streetlights, and any other devices with lighting components.

[0109] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The features, structures, or characteristics described above can be combined in any suitable manner in one or more embodiments.

[0110] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A micro light emitting device, characterized by, The micro light emitting device comprises: a light emitting structure, the light emitting structure comprising an epitaxial layer, a first bonding metal layer provided in sequence, the first bonding metal layer being provided with a first opening, the first opening being filled with a self-repairing material, the self-repairing material being a material reduced to metal in a preset temperature environment; a driving structure, the driving structure comprising a driving substrate, a second bonding metal layer provided in sequence, the second bonding metal layer being provided with a second opening, the second opening being filled with a self-repairing material, wherein the second bonding metal layer is bonded to the first bonding metal layer.

2. The micro light emitting device of claim 1, wherein, The micro light emitting device further comprises: a buffer adhesive layer provided between the first bonding metal layer and the second bonding metal layer; a conductive particle embedded in the buffer adhesive layer, one end of the conductive particle being in contact with the first bonding metal layer, the other end of the conductive particle being in contact with the second bonding metal layer.

3. The micro light emitting device according to claim 1, wherein: the first bonding metal layer comprises first protrusions and first grooves distributed alternately, the second bonding metal layer comprises second protrusions and second grooves distributed alternately, the first protrusions are provided correspondingly to the second grooves, and the second protrusions are provided correspondingly to the first grooves.

4. The micro light emitting device according to claim 3, wherein: the first opening is provided on the first protrusion, the second opening is provided on the second protrusion, and the surface of the self-repairing material is flush with the surface of the first protrusion and the surface of the second protrusion.

5. The micro light emitting device according to claim 3, wherein: in the first bonding metal layer, the surfaces of all the first protrusions are in the same horizontal plane, and the surfaces of all the first grooves are in the same horizontal plane; in the second bonding metal layer, the surfaces of all the second protrusions are in the same horizontal plane, and the surfaces of all the second grooves are in the same horizontal plane; the surface of the first protrusion is in registration with the surface of the second groove, and the surface of the second protrusion is in registration with the surface of the first groove.

6. The micro light emitting device according to claim 1, wherein: the light emitting structure further comprises a first adhesive layer provided between the epitaxial layer and the first bonding metal layer; the driving structure further comprises a second adhesive layer provided between the driving substrate and the second bonding metal layer.

7. The micro light emitting device according to claim 6, wherein: the light emitting structure further comprises a first barrier layer provided between the first adhesive layer and the first bonding metal layer; the driving structure further comprises a second barrier layer provided between the second adhesive layer and the second bonding metal layer.

8. The micro light emitting device according to claim 7, wherein: A depth of the first opening does not penetrate the first bonding metal layer and does not extend to a surface of the first barrier layer, and a self-repairing material in the first opening is not in contact with the first barrier layer; A depth of the second opening does not penetrate the second bonding metal layer and does not extend to a surface of the second barrier layer, and a self-repairing material in the second opening is not in contact with the second barrier layer.

9. A method for fabricating a micro light emitting device, comprising the steps of: Comprising: ​ Providing an epitaxial layer; forming a first bonding metal layer on the epitaxial layer, opening the first bonding metal layer to obtain a first opening, and filling a self-repairing material in the first opening to obtain a light-emitting chip wafer, the self-repairing material being a material reduced to metal in a preset temperature environment; Providing a driving substrate; forming a second bonding metal layer on the driving substrate, opening the second bonding metal layer to obtain a second opening, and filling the self-repairing material in the second opening to obtain a driving wafer; bonding the light-emitting chip wafer and the driving wafer on a side of the first bonding metal layer away from the epitaxial layer to obtain a bonding structure; cutting the bonding structure into a die to obtain a micro light-emitting device, wherein the micro light-emitting device comprises a light-emitting structure and a driving structure, and the light-emitting structure and the driving structure are bonded by the first bonding metal layer and the second bonding metal layer, and the second bonding metal layer is toward the first bonding metal layer and is bonded with the first bonding metal layer.

10. The method for fabricating a micro light-emitting device as described in claim 9, characterized in that, Before the bonding of the light-emitting chip wafer and the driving wafer, further comprising: forming a buffer glue layer on the second bonding metal layer; forming a conductive particle layer on the buffer glue layer, wherein the conductive particle layer comprises conductive particles, the conductive particles are embedded in the buffer glue layer when the light-emitting chip wafer and the driving wafer are bonded, one end of the conductive particles is in contact with the first bonding metal layer, and the other end of the conductive particles is in contact with the second bonding metal layer.

11. The preparation method of the micro light-emitting device according to claim 9, wherein: after the forming of the first bonding metal layer on the epitaxial layer, further comprising: etching the first bonding metal layer to obtain first protrusions and first grooves distributed alternately, wherein surfaces of all the first protrusions are in the same horizontal plane, and surfaces of all the first grooves are in the same horizontal plane; after the forming of the second bonding metal layer on the driving substrate, further comprising: etching the second bonding metal layer to obtain second protrusions and second grooves distributed alternately, wherein surfaces of all the second protrusions are in the same horizontal plane, and surfaces of all the second grooves are in the same horizontal plane; the bonding of the light-emitting chip wafer and the driving wafer comprises: correspondingly arranging the first protrusions and the second grooves, and correspondingly arranging the second protrusions and the first grooves, wherein the surface of the first protrusion is in alignment with the surface of the second groove, and the surface of the second protrusion is in alignment with the surface of the first groove.

12. The micro light emitting device manufacturing method of claim 11, wherein: the opening of the first bonding metal layer to obtain a first opening and filling the self-repairing material in the first opening comprises: opening the first bump to obtain a first opening and filling the self-repairing material in the first opening so that the surface of the self-repairing material is flush with the surface of the first bump; the opening of the second bonding metal layer to obtain a second opening and filling the self-repairing material in the second opening comprises: opening the second bump to obtain a second opening and filling the self-repairing material in the second opening so that the surface of the self-repairing material is flush with the surface of the second bump.

13. The method for fabricating a micro light-emitting device as described in claim 9, characterized in that, the forming of the first bonding metal layer on the epitaxial layer comprises: forming a first adhesion layer on the epitaxial layer; forming a first barrier layer on the side of the first adhesion layer away from the epitaxial layer; forming the first bonding metal layer on the side of the first barrier layer away from the first adhesion layer.

14. The method for fabricating a micro light-emitting device as described in claim 9, characterized in that, the forming of the second bonding metal layer on the driving substrate comprises: forming a second adhesion layer on the driving substrate; forming a second barrier layer on the side of the second adhesion layer away from the driving substrate; forming the second bonding metal layer on the side of the second barrier layer away from the second adhesion layer.

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