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 driving chip; the light-emitting chip is bonded with the driving chip, the light-emitting chip comprises a substrate and an epitaxial lamination layer, the epitaxial lamination layer is arranged on one side of the driving chip, the substrate is arranged on one side, deviating from the driving chip, of the epitaxial lamination layer, and one side, facing the epitaxial lamination layer, of the substrate comprises a plurality of pits with preset curved surface shapes; the epitaxial laminated layer comprises a plurality of convex structures in preset curved surface shapes and a plurality of pixel units, the convex structures are arranged on the opposite sides of the pixel units, the number of the convex structures is the same as that of the pixel units, the convex structures are embedded into the pits one by one, the shape of the pixel units projected to the substrate is the same as the shape of the convex structures projected to the substrate, and the convex structures are embedded into the pits one by one. The positions where the pixel units are projected to the substrate are the same as the positions where the protruding structures are projected to the substrate.

Description

Technical Field

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

[0002] Micro-LED (Micro Light-Emitting Diode) chip arrays 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, Micro-LED manufacturing processes suffer from problems such as low yield, low luminous efficiency, and crosstalk between pixels. Summary of the Invention

[0004] This application provides a miniature light-emitting device, which includes: Driver chip; A light-emitting chip is bonded to a driving chip. The light-emitting chip includes a substrate and an epitaxial stack. The epitaxial stack is disposed on one side of the driving chip, and the substrate is disposed on the side of the epitaxial stack facing away from the driving chip. The side of the substrate facing the epitaxial stack includes multiple recesses with preset curved shapes. The epitaxial stack includes multiple protrusions with preset curved shapes and multiple pixel units. The protrusions are disposed on the opposite side of the pixel units. The number of protrusions is the same as the number of pixel units. Each protrusion is embedded in a recess. The shape of the pixel unit projected onto the substrate is the same as the shape of the protrusion projected onto the substrate. The position of the pixel unit projected onto the substrate is the same as the position of the protrusion projected onto the substrate.

[0005] The light-emitting chip further includes: A light-shielding layer is disposed on the side of the substrate away from the epitaxial stack. The light-shielding layer includes multiple light-transmitting areas and light-shielding areas surrounding the light-transmitting areas. The number of light-transmitting areas is the same as the number of protrusions. The shape of the light-transmitting areas projected onto the substrate is the same as the shape of the protrusions projected onto the substrate. The position of the light-transmitting areas projected onto the substrate is the same as the position of the protrusions projected onto the substrate.

[0006] The light-shielding layer includes a reflective layer, a light-absorbing layer, and an anti-reflective layer. The reflective layer is disposed on the side of the substrate opposite to the epitaxial stack, the light-absorbing layer is disposed on the side of the reflective layer opposite to the substrate, and the anti-reflective layer is disposed on the side of the light-absorbing layer opposite to the reflective layer.

[0007] The substrate has marking points on the side facing the epitaxial stack. The marking points include a first marking point and a second marking point. The first marking point surrounds the plurality of pits, and the second marking point is disposed between two adjacent pixel units.

[0008] Wherein, the preset curved surface is hemispherical, the diameter of the pit is greater than or equal to the diameter of the pixel unit, and the radius of curvature of the pit is a preset multiple of the diameter of the pixel unit.

[0009] The epitaxial stack includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer. The first semiconductor layer is disposed on one side of the substrate, the light-emitting layer is disposed on the side of the first semiconductor layer away from the substrate, and the second semiconductor layer is disposed on the side of the light-emitting layer away from the first semiconductor layer. The peripheral area of ​​the first semiconductor layer is exposed, and the surface of the pixel unit is the second semiconductor layer. The light-emitting chip further includes a cathode electrode and an anode electrode. The cathode electrode is electrically connected to the peripheral region of the first semiconductor layer, and the anode electrode is electrically connected to the surface of the pixel unit.

[0010] The cathode electrode is located away from the surface of the first semiconductor layer, and is at the same horizontal position as the anode electrode, which is located away from the surface of the pixel unit.

[0011] The driving chip includes a driving circuit and a driving substrate, wherein the driving circuit is disposed on one side of the driving substrate; The micro light-emitting device further includes a bonding layer, a portion of which is disposed between the cathode electrode and the driving circuit, and a portion of which is disposed between the anode electrode and the driving circuit.

[0012] The micro light-emitting device further includes a transition layer, which is disposed between the cathode electrode and the bonding layer, and between the anode electrode and the bonding layer.

[0013] This application also provides a method for fabricating a micro light-emitting device, the method comprising: Provide driver chips; A substrate is provided, and a plurality of recesses with a predetermined curved shape are formed on one side of the substrate; An epitaxial stack is formed on one side of the recess, and the epitaxial stack is etched to form a light-emitting chip. The epitaxial stack includes multiple protrusion structures with preset curved shapes and multiple pixel units. The protrusion structures are disposed on the opposite side of the pixel units. The number of protrusion structures is the same as the number of pixel units. The protrusion structures are embedded in the recess one by one. The shape of the pixel unit projected onto the substrate is the same as the shape of the protrusion structure projected onto the substrate. The position of the pixel unit projected onto the substrate is the same as the position of the protrusion structure projected onto the substrate. On the side of the epitaxial stack facing away from the substrate, the driving chip and the light-emitting chip are bonded to obtain a micro light-emitting device.

[0014] The beneficial effects of this application are: In the current process of LED light-emitting array fabrication, the LED light-emitting layer and IC driving layer are ground thinner, and after the wafer formed by bonding the LED light-emitting layer and IC driving layer is cut into grains, the LED light-emitting layer and IC driving layer will warp; In addition, after the LED light-emitting layer and IC driving layer are bonded, the sapphire substrate of the LED light-emitting layer needs to be removed to reduce optical crosstalk, but LLO of the sapphire substrate will cause sapphire fragments to affect subsequent packaging. In this embodiment, the micro-light-emitting device retains the substrate of the light-emitting chip and eliminates the need for the LLO process that removes the substrate in existing technologies. This fundamentally avoids the problems of sapphire residue and GaN film damage caused by the LLO process. At the same time, the epitaxial stack of the light-emitting chip is embedded into the substrate pits one by one through the protrusion structure. This can effectively disperse stress during the bonding of the driver chip and the light-emitting chip and subsequent processing, reduce the warping phenomenon after the wafer is cut into dies, and significantly improve the fabrication yield. The pre-curved surface shape of the pits on the substrate corresponds one-to-one with the pre-curved surface shape of the protrusion structure of the epitaxial stack, and is completely consistent with the projection shape and position of the pixel unit on the substrate. The curved surface structure can optimize the light propagation path, reduce the total internal reflection loss of light at the interface between the substrate and the epitaxial stack, improve the effective emission rate of the light from the light-emitting layer, and solve the problem of low light efficiency. The protrusion structure corresponds one-to-one with the pit and matches the pixel unit, which can form a physical constraint on the light generated by each pixel unit, restrict the light from spreading to adjacent pixel units, thereby reducing optical crosstalk between pixels and improving the pixel crosstalk problem. Attached Figure Description

[0015] 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.

[0016] Figure 1This is a schematic cross-sectional view of the micro light-emitting device provided in the embodiments of this application; Figure 2 This is a top view schematic diagram of the micro light-emitting device provided in the embodiments of this application; Figure 3 This is a schematic flowchart of the fabrication method of the micro light-emitting device provided in the embodiments of this application. Detailed Implementation

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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, a micro light-emitting device includes: a driver chip 100; and a light-emitting chip 200, which is bonded to the driver chip 100. The light-emitting chip 200 includes a substrate 210 and an epitaxial stack 220. The epitaxial stack 220 is disposed on one side of the driver chip 100, and the substrate 210 is disposed on the side of the epitaxial stack 220 away from the driver chip 100. The side of the substrate 210 facing the epitaxial stack 220 includes a plurality of recesses with a preset curved shape. The epitaxial stack 220 includes a plurality of preset curved... The device comprises a surface-shaped protrusion structure 221 and a plurality of pixel units 222. The protrusion structure 221 is disposed on the opposite side of the pixel unit 222. The number of protrusion structures 221 is the same as the number of pixel units 222. The protrusion structures 221 are embedded in the recesses. The shape of the pixel unit 222 projected onto the substrate 210 is the same as the shape of the protrusion structure 221 projected onto the substrate 210. The position of the pixel unit 222 projected onto the substrate 210 is the same as the position of the protrusion structure 221 projected onto the substrate 210.

[0022] In the semiconductor field, micro-light-emitting devices (LEDs) refer to functional devices with dimensions in the micrometer range that can convert electro-optical signals and emit light of a specific wavelength. They are typically used in applications such as micro-displays and high-density lighting. In this embodiment, the micro-light-emitting device uses a Micro-LED as its core and achieves precise light emission through the synergistic effect of a driver chip and a light-emitting chip. It is a miniaturized optoelectronic device that integrates driving and light-emitting functions.

[0023] In this context, the driver chip is a dedicated chip in the semiconductor field used to provide electrical signals to drive a load. It typically includes CMOS circuits, driver transistors, and other structures. In this embodiment, the core function of the driver chip is to provide stable driving current and control signals to the pixel units of the light-emitting chip, enabling independent lighting or extinguishing control of each pixel unit.

[0024] Among them, the light-emitting chip is the core chip in the semiconductor field that can directly convert electrical energy into light energy. Its core structure typically includes a substrate and an epitaxial stack, and light emission is achieved through the recombination of electrons and holes in the semiconductor material of the epitaxial stack. In this embodiment, the light-emitting chip is the light-emitting body of the micro light-emitting device. It obtains a driving signal by bonding with a driving chip, thereby realizing light output.

[0025] In this process, bonding the light-emitting chip and the driver chip involves physically connecting two or more chips to achieve electrical connection and structural fixation. Common bonding methods include flip-chip bonding and thermo-press bonding. In this embodiment, the purpose of this bonding structure is to establish an electrical path between the light-emitting chip and the driver chip, enabling the control signals and current from the driver chip to be accurately transmitted to the pixel units of the light-emitting chip, while ensuring the structural stability between the two.

[0026] The substrate is the base material used to support the epitaxial layer. It needs to have good crystal compatibility, thermal stability, and mechanical strength. Common substrate materials include sapphire, silicon carbide, and silicon. In this embodiment, the substrate is made of sapphire and is disposed on the side of the epitaxial stack away from the driver chip. It provides a growth substrate and mechanical support for the epitaxial stack, and also enables optical control through the pit structure on its surface.

[0027] The epitaxial stack is a multilayer semiconductor thin film structure grown on a substrate using epitaxial growth technology. It typically includes an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, and is the core region for electro-optical conversion. In this embodiment, the epitaxial stack not only carries the light-emitting function but also integrates a raised structure that cooperates with the substrate pits, thus combining light emission and structural cooperation functions. The epitaxial stack is located on one side of the driver chip, which shortens the electrical signal transmission path between the light-emitting chip and the driver chip, reduces signal delay, and facilitates bonding processes, ensuring a tight connection between the two. The substrate is located on the side of the epitaxial stack away from the driver chip, placing it on the outside of the device. This avoids interference from the substrate with the electrical connection between the driver chip and the epitaxial stack, and allows for the modulation of the light emitted by the light-emitting layer through the pit structure on the substrate surface, without requiring substrate removal.

[0028] The preset surface shape is a surface form determined in advance according to optical performance requirements. Common shapes include hemispheres, parabolic surfaces, and ellipsoids. Its core function is to optimize the propagation path of light. In this embodiment, the preset surface shape is preferably hemispheres to match the light-emitting characteristics of pixel units and improve light extraction efficiency.

[0029] In this context, a pit is a recessed structure formed on the substrate surface through an etching process. In the semiconductor field, it is commonly used for positioning, structural enhancement, or optical manipulation. In this embodiment, the pit is a key structure on the side of the substrate facing the epitaxial stack, used to cooperate with the raised structures of the epitaxial stack, and simultaneously guiding light propagation through its curved shape. The side of the substrate facing the epitaxial stack includes multiple pits with preset curved shapes, so that each pit corresponds to the raised structure of a pixel unit, providing space for subsequent embedding. Furthermore, the array distribution of multiple pits matches the array layout of the pixel units.

[0030] In this context, a raised structure is a protruding shape formed on the surface of an epitaxial stack through epitaxial growth or etching processes. In the semiconductor field, it is often used in conjunction with recessed structures to achieve precise positioning or optimize interface contact performance. In this embodiment, the raised structure is a key structure on the side of the epitaxial stack facing the substrate. Its shape and size perfectly match the recesses on the substrate, and it is used to embed into the recesses to achieve structural fixation and optical control.

[0031] In this context, a pixel unit is the smallest functional unit in a light-emitting chip capable of independently emitting light. In the semiconductor field, each pixel unit corresponds to a micro-light-emitting point, and multiple pixel units arranged in an array can form a display or illumination surface. In this embodiment, the pixel unit is the core part of the epitaxial stack that realizes electro-optic conversion. It consists of an n-type layer, a light-emitting layer, and a p-type layer of the epitaxial stack. Each pixel unit can independently receive signals from the driver chip and emit light. The epitaxial stack includes multiple raised structures with preset curved shapes and multiple pixel units, enabling the epitaxial stack to simultaneously possess light-emitting and structural adaptation capabilities, achieving precise matching with the substrate without the need for additional structures. The raised structures are located on the opposite side of the pixel units, ensuring that the raised structures and pixel units do not overlap spatially or interfere with each other functionally. At the same time, the light from the pixel units can be directly transmitted to the raised structures, and then the light path is optimized through the curved surface of the recesses. The number of protrusions is the same as the number of pixel units, ensuring that each pixel unit can be matched with a protrusion. This, in turn, allows for independent control of light from each pixel unit through the cooperation of the protrusions and recesses, avoiding the problem of some pixel units lacking optical control structures due to a mismatch in the number of protrusions. The protrusions are embedded one-to-one into the recesses, achieving precise positioning of the epitaxial stack and the substrate, preventing relative displacement during bonding or use. Simultaneously, the protrusions and recesses form a closed optical structure, constraining the light propagation range.

[0032] Specifically, the shape of the pixel unit projected onto the substrate is the same as the shape of the protrusion structure projected onto the substrate. This identical projection shape ensures that the light emitted from the pixel unit completely covers the protrusion structure, and then propagates uniformly through the curved surfaces of the protrusion and recess, avoiding the problem of some light rays being uncontrollable by the optical structure due to shape mismatch. The position of the pixel unit projected onto the substrate is the same as the position of the protrusion structure projected onto the substrate. This identical projection position ensures that the light from the pixel unit is accurately incident on the corresponding protrusion-recess structure, avoiding optical crosstalk between adjacent pixel units caused by light deviation, and ensuring consistent light control effect for each pixel unit.

[0033] In some implementations, such as Figure 1 As shown, the light-emitting chip further includes a light-shielding layer 230, which is disposed on the side of the substrate 210 away from the epitaxial stack 220.

[0034] Please see Figure 2 , Figure 2 This is a top view schematic diagram of the micro light-emitting device provided in the embodiments of this application. For example... Figure 2As shown, the light-shielding layer 230 includes a plurality of light-transmitting areas 231 and a light-shielding area 232 surrounding the light-transmitting areas 231. The number of light-transmitting areas 231 is the same as the number of protrusions 221. The shape of the light-transmitting areas 231 projected onto the substrate 210 is the same as the shape of the protrusions 221 projected onto the substrate 210. The position of the light-transmitting areas 231 projected onto the substrate 210 is the same as the position of the protrusions 221 projected onto the substrate 210.

[0035] The light-shielding layer is a functional film layer used to control the light propagation path and block stray light leakage or intrusion. It is usually made of materials with high reflectivity, high absorbance, or specific optical blocking properties, and its function is to optimize the optical performance of the device and reduce light interference. In this embodiment, the light-shielding layer, through a partitioned design of light-transmitting and light-shielding areas, precisely controls the emitted light from the pixel unit on the outside of the substrate, further improving light efficiency and suppressing pixel crosstalk. The light-shielding layer is disposed on the side of the substrate away from the epitaxial stack, which can perform the final optical constraint on the emitted light transmitted through the substrate without interfering with the bonding structure of the light-emitting chip and the driving chip, or affecting the light-emitting function of the epitaxial stack, while avoiding physical or chemical interference between the light-shielding layer and the internal core structure.

[0036] The light-transmitting area is a specific region within the light-shielding layer that allows selective light transmission. Its size and shape must match the light-emitting unit of the device to ensure unobstructed output of the effective light generated by the light-emitting unit. In this embodiment, the light-transmitting area is a dedicated light-emission channel for the pixel unit, allowing only the light from the corresponding pixel unit, regulated by the raised and recessed structures, to pass through. It does not allow side leakage light from adjacent pixels or external stray light to enter, making it the core area for ensuring light efficiency. The light-shielding areas are distributed around the light-transmitting areas, forming an isolation zone. Its core function is to intercept side leakage light from pixel units diffusing to adjacent areas, while simultaneously blocking external stray light from entering the device, thus optically cutting off the path of pixel crosstalk. The light-shielding layer includes multiple light-transmitting areas and light-shielding areas surrounding them. Multiple light-transmitting areas correspond to multiple pixel units, and the surrounding light-shielding areas isolate adjacent light-transmitting areas, forming an arrayed, partitioned light-shielding structure. This confines the light from each pixel unit to an independent light-transmitting area, spatially preventing light crosstalk.

[0037] The number of light-transmitting areas is the same as the number of raised structures. Since each raised structure directly corresponds to a pixel unit, the identical number of light-transmitting areas ensures that each pixel unit has a unique light-emitting channel. This avoids situations where some pixel units lack a dedicated light-transmitting area or multiple pixel units share a single light-transmitting area due to a mismatch in the number of areas. The shape of the light-transmitting area projected onto the substrate is the same as the shape of the raised structure projected onto the substrate. If the projected shapes are inconsistent, the light transmitted from the raised structure to the substrate will be partially blocked by the light-shielding area due to shape misalignment, resulting in light loss. The identical projection shapes ensure that the light output from the raised structure completely covers the light-transmitting area, minimizing the loss of effective light and improving light extraction efficiency. The position of the light-transmitting area projected onto the substrate is the same as the position of the protrusion structure projected onto the substrate. If the position is offset, the light output by the protrusion structure will deviate from the light-transmitting area, and some light will illuminate the light-blocking area or the adjacent light-transmitting area. Since the two projection positions are the same, the light is accurately guided, ensuring that the light from the pixel unit can pass through the light-transmitting area vertically and completely after being controlled by the protrusion-dimple, further suppressing crosstalk and improving the stability of light efficiency.

[0038] In this embodiment, the light-shielding area of ​​the light-shielding layer can efficiently intercept side leakage light diffused from the pixel unit to adjacent areas, while blocking stray light from the external environment. It suppresses pixel crosstalk from both active light shielding and passive stray light prevention dimensions. The shape and position of the light-transmitting area are perfectly matched with the protrusion structure, ensuring that the light from the pixel unit after protrusion-recession control can pass through the light-transmitting area completely and accurately, avoiding edge light loss caused by shape misalignment or position shift, and further improving light extraction efficiency. The light-shielding layer is set on the outside of the substrate and does not need to directly contact the bonding structure of the epitaxial stack and the driver chip. It will not interfere with the bonding process or the stability of the epitaxial stack, and at the same time avoids the problem of increased process complexity that may be caused by adding a light-shielding structure inside the device. It indirectly ensures the fabrication yield of the device and provides more reliable structural support for high-resolution, high-brightness Micro-LED display applications.

[0039] In some implementations, such as Figure 1 As shown, the light-shielding layer 230 includes a reflective layer 233, a light-absorbing layer 234, and an anti-reflective layer 235. The reflective layer 233 is disposed on the side of the substrate 210 opposite to the epitaxial stack 220, the light-absorbing layer 234 is disposed on the side of the reflective layer 233 opposite to the substrate 210, and the anti-reflective layer 235 is disposed on the side of the light-absorbing layer 234 opposite to the reflective layer 233.

[0040] The reflective layer is a functional film made of highly reflective material. Its function is to reflect light in a specific direction, changing the light propagation path to reduce light loss or suppress interference. In this embodiment, the reflective layer is the first light-shielding barrier of the light-shielding layer, directly attached to the outer side of the substrate. It is mainly used to reflect lateral light leakage from the pixel unit to adjacent areas. When light propagates outward from the epitaxial stack through the substrate, if lateral deviation occurs, it will first be reflected back into the substrate by the reflective layer and redirected to the light-transmitting area, thus reducing stray light interference and minimizing the waste of effective light.

[0041] The light-absorbing layer is a film made of a material with a high light absorption coefficient. It absorbs incident light and prevents secondary reflection of residual stray light that has not been reflected. If only a reflective layer is used, some stray light may be reflected and then deflected to other pixel areas, still causing crosstalk. In this embodiment, the light-absorbing layer is disposed outside the reflective layer as a second light-shielding barrier to absorb residual stray light that has not been controlled after being reflected by the reflective layer. For example, the reflective layer may have a small amount of leaked stray light due to surface flatness or material properties. The light-absorbing layer can completely absorb this stray light, fundamentally cutting off the propagation path of the stray light and further enhancing the light-shielding effect.

[0042] The anti-reflection layer is a film made of transparent material. By adjusting the thickness and refractive index of the film, the reflected light at the interface of the incident light is destructively interfered, thereby reducing reflection loss and improving light transmittance. In this embodiment, the anti-reflection layer is the outermost layer of the light-shielding layer and only acts on the position corresponding to the light-transmitting area. When the effective light from the pixel unit propagates through the substrate, reflective layer, and light-absorbing layer to the anti-reflection layer, the anti-reflection layer can significantly reduce the reflection loss of light at the interface between the air and the anti-reflection layer, allowing more effective light to escape from the light-transmitting area and directly improving the light extraction efficiency of the device.

[0043] The reflective layer is disposed on the side of the substrate away from the epitaxial stack, the light-absorbing layer is disposed on the side of the reflective layer away from the substrate, and the anti-reflective layer is disposed on the side of the light-absorbing layer away from the reflective layer. The reflective layer, being closest to the substrate, preferentially intercepts side-leaking light just emanating from the substrate; the light-absorbing layer, in the middle, handles stray light that has leaked through the mesh; and the anti-reflective layer, on the outermost layer, optimizes only the emission of effective light. This arrangement also avoids direct contact between the anti-reflective layer and the substrate, and prevents the light-absorbing layer from directly contacting the air.

[0044] In this embodiment, the reflective layer preferentially intercepts lateral side leakage light, while the light-absorbing layer absorbs the remaining residual stray light. Compared to a single light-shielding layer, the stray light suppression efficiency is improved, significantly reducing optical crosstalk between pixels, making it particularly suitable for high-resolution Micro-LED display scenarios. The anti-reflective layer optimizes the emission interface of effective light, reducing light reflection loss in the light-transmitting area. Combined with the reflective layer's recovery and reflection of side leakage light, the overall light extraction efficiency of the device is improved. All three film layers are prepared using mature semiconductor sputtering and PECVD processes, exhibiting good compatibility with the substrate and existing device structures. This avoids adding additional process complexity or yield risks, balancing performance optimization and fabrication feasibility.

[0045] In some implementations, such as Figure 2 As shown, the substrate has marking points on the side facing the epitaxial stack, wherein the marking points include a first marking point 211 and a second marking point 212, the first marking point surrounds the plurality of pits, and the second marking point is disposed between two adjacent pixel units.

[0046] In this context, marker points refer to reference structures used for precise positioning and alignment in processes such as photolithography and etching. They are typically made of materials with high contrast to the substrate or epitaxial layer material and can be identified by optical inspection equipment. Their core function is to ensure precise matching of pattern positions across multiple process steps, reducing process defects caused by alignment deviations. In this embodiment, marker points are a key reference for achieving precise coordination between substrate pit fabrication and epitaxial stack pixel unit fabrication, directly determining the positional matching degree between the pits and pixel units, and avoiding light efficiency loss or crosstalk caused by process misalignment. Marker points are provided on the side of the substrate facing the epitaxial stack, where the epitaxial stack is grown. If the marker points were located on the other side of the substrate, they would be obscured by the substrate itself after epitaxial growth, making them unusable for subsequent photolithographic alignment of the epitaxial layer. In this embodiment, the marker points are located at the interface between the substrate and the epitaxial stack. Marker point fabrication can be completed before epitaxial growth, and the marker points can still be identified through the epitaxial layer by optical equipment after epitaxial growth, providing a direct alignment reference for subsequent photolithographic pits and pixel units, simplifying the process flow and improving alignment accuracy.

[0047] In this embodiment, the first marker point is positioned at the overall region level, meaning it defines the entire array area of ​​the pits to be fabricated on the substrate, rather than the location of a single pit. This prevents the process pattern from exceeding the effective area or deviating from the substrate center, ensuring the integrity and consistency of the overall array. The core function of the first marker point in this embodiment is to define the boundary of the pit array, ensuring that subsequent photolithography of the pits does not process in invalid areas of the substrate, while also providing a reference for the overall position calibration of the pit array.

[0048] The second marker point positioning level is at the single-unit level, meaning it's used to precisely locate the position of each pixel unit, ensuring uniform spacing and alignment between adjacent pixel units. Region-level marker points alone cannot guarantee the positional accuracy of a single unit; pixel-by-pixel alignment is achieved through inter-unit marker points. In this embodiment, the second marker point directly corresponds to the pixel unit array, providing an independent alignment reference for the photolithography of each pixel unit. This ensures that the projection position of a single pixel unit completely coincides with the corresponding pit's projection position, avoiding light offset caused by misalignment of a single pixel.

[0049] In this design, the first marker point surrounds multiple pits, defining the array area composed of all the pits in a circumferential manner, rather than surrounding a single pit. For example, if the pits are distributed in a 100×100 array, the first marker point will form a closed frame around the array, with the inner boundary of the frame maintaining a preset distance from the outermost pit of the pit array. In this embodiment, this layout allows for rapid identification of the overall range of the pit array using an optical alignment device. Before photolithography of the pits, the process field of view of the photolithography machine is aligned with the first marker point frame to ensure that the pit array falls entirely within the effective epitaxial growth area of ​​the substrate, while avoiding the edges of the pit array being too close to the edges of the substrate.

[0050] In this embodiment, the second marker point is located in the gap between two adjacent pixel units and does not occupy the effective area of ​​the pixel unit or the pit. The size of the second marker point needs to be much smaller than the pixel unit spacing to avoid blocking the light-emitting area of ​​the pixel unit or the optical control area of ​​the pit. In this embodiment, when photolithographically ... In this embodiment, the first marker point, by surrounding the pit array, ensures that the pit fabrication range precisely matches the effective epitaxial region of the substrate, avoiding ineffective processes. Simultaneously, it provides a rapid alignment reference for the overall photolithography of the pit array, improving process efficiency. The second marker point, through a grid-like distribution between pixel units, achieves precise alignment of individual pixel units, controlling the positional deviation between the pixel unit and the corresponding pit to the nanometer level. This prevents misalignment from causing the protrusion structure to fail to fully embed into the pit or for light to deflect to adjacent pixels, significantly reducing the process defect rate. The synergistic effect of the two marker points improves the alignment accuracy of the three core processes: substrate pit fabrication, epitaxial layer growth, and pixel unit photolithography. Compared to processes without marker points, device yield is improved, while ensuring consistent optical control effects for each pixel unit. This provides crucial process assurance for the mass production of high-resolution, high-uniformity Micro-LED display devices.

[0051] In some embodiments, the preset surface is hemispherical, the diameter of the pit is greater than or equal to the diameter of the pixel unit 222, and the radius of curvature of the pit is a preset multiple of the diameter of the pixel unit 222.

[0052] Among them, the hemispherical shape is a classic curved surface shape that combines light-gathering function and low light loss. The normal direction of the hemispherical surface is distributed radially, which allows the incident light to be emitted uniformly along the normal direction, reducing total internal reflection of light at the surface interface. At the same time, the hemispherical structure is easy to realize in semiconductor processes through dry etching combined with surface polishing, with high process maturity and stable yield. In this embodiment, the preset curved surfaces of the pit and the protrusion structure are set as hemispherical. On the one hand, it can achieve seamless bonding between the protrusion structure and the pit. The curvature of the hemispherical surface is consistent everywhere, and the stress distribution is uniform during bonding, avoiding film damage caused by local stress concentration. On the other hand, the light-gathering effect of the hemispherical shape can concentrate the divergent light of the pixel unit and transmit it to the outside of the substrate, reducing the light propagation loss within the substrate.

[0053] In this case, the diameter of the pit is greater than or equal to the diameter of the pixel unit. If the diameter of the pit is less than the diameter of the pixel unit, the light emitted from the edge of the pixel unit will exceed the pit range and directly illuminate the planar area of ​​the substrate. This light is prone to lateral diffusion or absorption by the substrate due to total internal reflection. When the diameter of the pit is greater than or equal to the diameter of the pixel unit, the light-emitting area of ​​the pixel unit can be completely covered by the pit, ensuring that all the light from the pixel unit can enter the pit-protrusion structure for optical control.

[0054] The radius of curvature directly determines the light-gathering ability and total internal reflection suppression effect of the hemispherical recess. If the radius of curvature is too small, the recess surface is too steep, and light is prone to secondary reflection inside the surface. If the radius of curvature is too large, the recess is close to a plane, and the light-gathering and anti-total internal reflection effects are weakened. In this embodiment, the preset multiplier can be 1.2-1.5 times. This range can reduce the total internal reflection rate of the light from the pixel unit in the recess to below 10%, while avoiding excessive light gathering that results in an excessively small light output angle, thus achieving a balance between high light efficiency and wide viewing angle.

[0055] In this embodiment, the hemispherical curved surface utilizes a radial normal distribution to significantly reduce the total internal reflection loss of light at the pit-protrusion interface, ensuring that all light rays of the pixel unit can be controlled by the optical structure and avoiding crosstalk caused by edge light leakage; the radius of curvature is 1.2-1.5 times the pixel diameter, which ensures high light-gathering effect while taking into account a wide viewing angle, thus solving the contradiction of "high light efficiency but narrow viewing angle" in traditional curved surface structures.

[0056] In some implementations, such as Figure 1As shown, the epitaxial stack 220 includes a first semiconductor layer 223, a light-emitting layer 224, and a second semiconductor layer 225. The first semiconductor layer 223 is disposed on one side of the substrate 210, the light-emitting layer 224 is disposed on the side of the first semiconductor layer 223 away from the substrate 210, and the second semiconductor layer 225 is disposed on the side of the light-emitting layer 224 away from the first semiconductor layer 223. The peripheral area of ​​the first semiconductor layer 223 is exposed, and the surface of the pixel unit 222 is the second semiconductor layer 225. The light-emitting chip 200 further includes a cathode electrode 240 and an anode electrode 250. The cathode electrode 240 is electrically connected to the peripheral region of the first semiconductor layer 223, and the anode electrode 250 is electrically connected to the surface of the pixel unit 222.

[0057] In this embodiment, the first semiconductor layer refers to an n-type semiconductor layer used to provide electrons. It typically uses n-type GaN as the core material, achieving a high electron concentration through silicon doping. This layer serves as an electron transport channel, introducing external current into the light-emitting layer. In this example, the first semiconductor layer is the bottom layer of the epitaxial stack, providing a lattice-matched substrate for the subsequent epitaxial growth of the light-emitting layer and the second semiconductor layer. Common cathode connection is achieved through peripheral region exposure, simplifying electrode wiring.

[0058] In this context, the light-emitting layer refers to the region where electrons and holes recombine and release photons. GaN-based LEDs typically employ an InGaN / GaN multi-quantum-well structure, with a well layer thickness of 2-3 nm and a barrier layer thickness of 5-10 nm. Electrons from the first semiconductor layer and holes from the second semiconductor layer cross the potential barrier and enter the quantum well. Upon recombination within the well, photons of a specific wavelength are released according to energy conservation. In this embodiment, the light-emitting layer is the core of the pixel unit's electro-optic conversion, and its quantum well period and In composition determine the device's emission wavelength.

[0059] The second semiconductor layer is a p-type semiconductor layer corresponding to the first semiconductor layer. It is typically made of p-type GaN, with magnesium doping to achieve the required hole concentration. This serves as a hole transport channel, introducing external current into the light-emitting layer and forming a PN junction with the first semiconductor layer. Because the hole mobility of p-type GaN is lower than that of n-type GaN, the second semiconductor layer is usually thinner and requires an annealing process to activate the Mg impurities. In this embodiment, the second semiconductor layer is the surface structure of the pixel unit, and its surface directly serves as the current input interface for the pixel unit, facilitating connection to the anode electrode.

[0060] In this embodiment, a first semiconductor layer is disposed on one side of the substrate, a light-emitting layer is disposed on the side of the first semiconductor layer facing away from the substrate, and a second semiconductor layer is disposed on the side of the light-emitting layer facing away from the first semiconductor layer. The sapphire substrate first grows n-GaN, then the light-emitting layer, and finally p-GaN. This stacking ensures efficient recombination of electrons from n-GaN to the light-emitting layer and holes from p-GaN to the light-emitting layer within the light-emitting layer. In this embodiment, this sequence also matches the substrate pit-epitaxy protrusion structure. The protrusion structure is composed of n-GaN, the light-emitting layer, and p-GaN, ensuring that when the protrusion is attached to the pit, the light-emitting layer remains between the n / p layers, without affecting the light-emitting function.

[0061] When the peripheral region of the first semiconductor layer is exposed, the light-emitting layer and the second semiconductor layer in the peripheral region of the substrate are removed through photolithography and etching processes, exposing the underlying first semiconductor layer. If each pixel unit were to have its own individual n-electrode, the wiring complexity and device area would increase significantly. However, exposing the peripheral n-GaN allows for the fabrication of a ring-shaped common cathode electrode, where all pixel units share the same cathode through the n-GaN layer, simplifying the electrode structure. In this embodiment, the peripheral exposed region is typically located at the edge of the substrate to avoid short-circuiting with the anode electrode of the pixel unit.

[0062] In this embodiment, the surface of the pixel unit is the second semiconductor layer. Since p-GaN is the top layer of the pixel unit, using it directly as the surface avoids light loss caused by adding an additional conductive layer. While adding an ITO transparent electrode could improve current diffusion, it would absorb some light. In this embodiment, the surface of the pixel unit is connected one-to-one with the anode electrode, allowing the current from the driving chip to be directly input into the p-GaN through the anode electrode and then transmitted to the light-emitting layer, thus achieving independent current control for each pixel unit.

[0063] The cathode electrode is a metal electrode used to introduce external driving current into the first semiconductor layer. It needs to meet the requirements of low contact resistance, high conductivity, and strong GaN adhesion. GaN-based LEDs commonly use a Ti / Al / Ni / Au multilayer metal structure. In this embodiment, the cathode electrode is a common electrode. By covering the exposed peripheral area of ​​the first semiconductor layer, it provides a unified electronic input channel for all pixel units, reducing the number of electrodes and wiring complexity.

[0064] The anode electrode is a metal electrode used to introduce external driving current into the second semiconductor layer. Since it needs to correspond to each pixel unit, its size must match the pixel unit, and the material commonly used is Cr / Au or a transparent conductive material. In this embodiment, the anode electrode is an independent electrode, with one anode corresponding to each pixel unit. This ensures that the driving chip can individually control the current magnitude or on / off state of each pixel, making it a core structure for high-resolution displays.

[0065] In this embodiment, the cathode electrode is electrically connected to the peripheral region of the first semiconductor layer. Through metal evaporation and annealing processes, the cathode electrode is directly deposited in the exposed peripheral region of the first semiconductor layer, forming an ohmic contact. This allows the negative current of the driving chip to rapidly diffuse through the cathode electrode to the entire first semiconductor layer and then be evenly distributed to the n-type region of each pixel unit, avoiding pixel brightness differences caused by uneven current distribution. In this embodiment, the cathode electrode is typically designed as a ring to ensure that the current diffuses evenly from the periphery to the center, reducing the current deviation between edge pixels and center pixels.

[0066] In this embodiment, the anode electrode is electrically connected to the surface of the pixel unit. The anode electrode is directly deposited on the surface of the second semiconductor layer of each pixel unit, forming an ohmic contact. Since each anode corresponds to only one pixel unit, the positive current of the driving chip can be precisely input to the p-type region of the corresponding pixel through the independent anode, and then transmitted to the light-emitting layer for electron recombination. In this embodiment, the center of the anode electrode is perfectly aligned with the center of the pixel unit, ensuring that the current is evenly distributed within the pixel unit and avoiding localized light emission caused by electrode misalignment.

[0067] In this embodiment, the first semiconductor layer is exposed on the periphery and the annular common cathode design significantly reduces the number of electrodes, simplifies wiring complexity, and avoids the risk of short circuits caused by multiple electrode crossings, thus improving device yield. The one-to-one connection between the independent anode and the pixel unit surface enables the driver chip to precisely control the current of each pixel, achieving 256 levels of grayscale display and meeting the requirements of high-resolution display. The low-resistance ohmic contact between the electrode and the semiconductor layer reduces current transmission loss, lowers the device operating voltage, improves energy efficiency, and avoids electrode overheating due to excessive contact resistance, thus extending service life.

[0068] In some implementations, such as Figure 1 As shown, the cathode electrode 240 is away from the surface of the first semiconductor layer 223, and is at the same horizontal position as the anode electrode 250, which is away from the surface of the pixel unit 222.

[0069] In this design, the surface of the cathode electrode facing away from the first semiconductor layer and the surface of the anode electrode facing away from the pixel unit are at the same horizontal level. This ensures uniform contact between the cathode and anode electrodes and the subsequently bonded driver chip, avoiding poor local contact or intermittent connections caused by height differences between the two electrode surfaces. This improves the stability and reliability of the electrical connection, ensuring smooth and uniform current transmission to all areas of the light-emitting chip, reducing the risk of electrode overheating and burn-out caused by localized current concentration, and extending the lifespan of the micro-light-emitting device. Simultaneously, the flush surface of the two electrodes ensures uniform force during bonding, preventing cracking and deformation of the epitaxial stack, electrodes, and substrate due to uneven force, thus ensuring the overall structural integrity of the device and reducing the defect rate during fabrication. Furthermore, uniform current transmission promotes consistent brightness across all pixel units, improving the uniformity of the display effect and avoiding uneven brightness. The flush electrode surfaces also simplify the alignment and bonding process during bonding with the driver chip, eliminating the need for additional adjustments to the electrode height difference, improving device fabrication efficiency, and ensuring overall device flatness after bonding, laying a solid foundation for subsequent packaging and other processes.

[0070] In some implementations, such as Figure 1 As shown, the driving chip 100 includes a driving circuit 110 and a driving substrate 120, with the driving circuit 110 disposed on one side of the driving substrate 120. The micro light-emitting device further includes a bonding layer 300, a portion of which is disposed between the cathode electrode 240 and the driving circuit 110, and a portion of which is disposed between the anode electrode 250 and the driving circuit 110.

[0071] The driver chip includes a driver circuit and a driver substrate. The driver circuit is disposed on one side of the driver substrate, which is the base structure supporting the driver circuit. Its core functions are to provide mechanical support, electrical insulation, and heat dissipation channels. Common materials include glass substrates, silicon substrates, or flexible substrates. The driver circuit is the functional core of the driver chip, typically a CMOS circuit, containing units such as driver transistors, signal latches, and current sources. It is used to convert externally input control signals into precise drive currents and output them to the light-emitting chip. The driver circuit being disposed on one side of the driver substrate ensures close connection between the driver circuit and the electrodes of the light-emitting chip, and also allows the heat generated during circuit operation to be dissipated through the substrate's heat dissipation function, preventing performance degradation due to overheating. In this embodiment, the driver substrate and driver circuit provide a one-to-one drive signal to the array pixel units, achieving a high-resolution Micro-LED display.

[0072] The bonding layer is a functional layer used to achieve electrical connection and structural fixation between two chips. It must simultaneously meet three major requirements: low contact resistance, high mechanical strength, and good compatibility with electrode materials. Common materials include indium, tin-silver alloy, and copper bumps. Compared with traditional wire bonding, the bonding layer does not require leads, which can significantly reduce the device size and reduce signal transmission paths.

[0073] A portion of the bonding layer is disposed between the cathode electrode and the driving circuit, corresponding to the common cathode electrode of the light-emitting chip. This portion of the bonding layer must perfectly match the shape and position of the cathode electrode. The common negative terminal of the driving circuit is connected to the common cathode electrode of the light-emitting chip through this portion of the bonding layer, providing a unified electron return path for all pixel units. In this embodiment, this portion of the bonding layer adopts a ring-shaped continuous distribution design to ensure that the current from the common cathode electrode can be uniformly transmitted to the driving circuit, avoiding insufficient electron supply to some pixel units due to poor local contact.

[0074] In this embodiment, a portion of the bonding layer is disposed between the anode electrode and the driving circuit, corresponding to the independent anode electrode of the light-emitting chip. This portion of the bonding layer needs to form a one-to-one discrete bump structure with the anode electrode. The independent positive electrode driving unit of the driving circuit uses this portion of the bonding layer to input precisely controlled current into the anode electrode of the corresponding pixel unit, realizing independent brightness or grayscale adjustment for each pixel. In this embodiment, the bump size and position of this portion of the bonding layer need to be completely aligned with the anode electrode to avoid short circuits or bump misalignment between adjacent bumps.

[0075] In this embodiment, the integrated driver chip provides one-to-one precise current control for the array pixels, improving current regulation accuracy and avoiding signal delay caused by traditional discrete driver circuits, thus meeting the requirements of high refresh rate Micro-LED displays. The partitioned bonding layer ensures uniform current transmission in the common cathode and enables independent and precise connection of the anode. At the same time, the low-temperature bonding characteristics of the indium bonding layer prevent high-temperature damage to the light-emitting layer. The flip-chip bonding layer does not require leads, reducing the overall thickness of the device. Furthermore, the In metal in the bonding layer has good ductility, which can alleviate the thermal stress caused by the difference in thermal expansion coefficients between the light-emitting chip and the driver chip, reducing the risk of bonding failure during long-term use of the device.

[0076] In some implementations, such as Figure 1 As shown, the micro light-emitting device further includes a transition layer 400, which is disposed between the cathode electrode 240 and the bonding layer 300, and between the anode electrode 250 and the bonding layer 300.

[0077] The transition layer is a functional intermediate film layer disposed between the electrode and the bonding layer to improve interface performance. It can solve compatibility issues between the electrode and the bonding layer, enhance interfacial adhesion, block interdiffusion of metal atoms, and reduce contact resistance. Commonly used materials are metals or alloys with high chemical stability and suitable coefficients of thermal expansion. For example, the transition layer material can be nickel, titanium, or platinum, etc. In this embodiment, the bonding layer uses indium metal, and the electrodes are a Ti / Al / Ni / Au multilayer metal for the cathode and a Cr / Au for the anode. Therefore, the transition layer must simultaneously achieve the dual functions of diffusion blocking and adhesion enhancement, and is a key intermediate structure to ensure bonding reliability.

[0078] The transition layer is disposed between the cathode electrode and the bonding layer, and between the anode electrode and the bonding layer, covering all contact areas between the electrodes and the bonding layers of the light-emitting chip, and must precisely match the morphology of the electrodes and bonding layers. At the interface between the cathode electrode and the bonding layer, the transition layer needs to block the diffusion of In and Al from the cathode electrode; at the interface between the anode electrode and the bonding layer, the transition layer needs to enhance the bonding force between Cr and In. In this embodiment, this arrangement ensures that the performance of all electrical connection interfaces is optimized, avoiding the failure of the entire device due to the failure of a single interface. At the same time, the transition layer exists only between the electrodes and the bonding layer, does not occupy other functional areas, and does not affect the core optical performance of the device.

[0079] In this embodiment, the transition layer significantly improves the interfacial bonding force between the electrode and the bonding layer, enhancing both the cathode and anode bonding forces. This effectively prevents bonding delamination caused by vibration and thermal cycling during packaging, transportation, or use. The diffusion barrier effect of the transition layer prevents the interdiffusion of Al and In, avoiding the formation of a brittle Al-In alloy and preventing sudden changes in contact resistance caused by cracking in the bonding area. The transition layer reduces the contact resistance between the electrode and the bonding layer, reducing current transmission losses and improving the stability of the device's operating current. At the same time, the coefficient of thermal expansion of the Ni material in the transition layer is between that of the electrode material and In, which can alleviate interfacial thermal stress and further extend the device's service life.

[0080] In some embodiments, the inner wall of the pit includes a grating texture with a period of 200-300 nm and a depth of 50-80 nm.

[0081] In this context, grating texture refers to a periodic uneven structure formed on the surface of a material using micro-nano fabrication processes. It utilizes the diffraction and interference effects of light to control the direction of light propagation. When light passes through or is reflected by the grating texture, its direction is deflected due to the change in refractive index of the periodic structure, effectively breaking the condition for total internal reflection. In this embodiment, the grating texture is a supplementary and optimized structure to the light-gathering function of the hemispherical pits. Through micro-nano-level periodic design, it works synergistically with the macroscopic curved surface of the pits to further improve light extraction efficiency and optimize the light emission angle.

[0082] The inner wall of the pit includes a grating texture. The inner wall of the substrate pit is a critical propagation path for light entering the substrate from the epitaxial stack. Although the light at the GaN-sapphire interface has reduced total internal reflection by passing through the hemispherical pit, some light still cannot escape due to the excessive incident angle. In this embodiment, the grating texture is set on the inner wall of the pit, which allows the light near these critical angles to be deflected by grating diffraction to a direction smaller than the critical angle, thereby escaping from the substrate. At the same time, the grating texture is avoided from affecting the adhesion stability between the protrusion structure and the pit.

[0083] In this embodiment, the grating texture effectively breaks the total internal reflection condition of light at the GaN-sapphire interface. For light with an incident angle close to the critical angle, the diffraction effect of the 200-300nm period can deflect more than 70% of the critical angle light into the emission angle range. Combined with the light-gathering function of the pit, the overall light extraction efficiency of the device is improved compared with the structure without grating texture. The periodic structure of the grating texture makes the light emission angle more uniform. Without grating, the light-gathering of the pit tends to cause the light emission angle to be concentrated in front, while grating diffraction can expand the half-angle of light emission, meeting the wide viewing angle requirements of micro-display devices. The directional control of light by the grating texture further reduces pixel crosstalk. Through diffraction, the side leakage light propagating laterally is deflected to the outside of the substrate, thereby reducing the pixel crosstalk coefficient. The parameters of 200-300nm period and 50-80nm depth can be achieved by existing semiconductor nanofabrication processes without introducing new equipment. The process yield is stable, taking into account both performance improvement and mass production feasibility.

[0084] As can be seen from the above, the micro-light-emitting device provided in this application retains the substrate of the light-emitting chip and does not require the LLO process that removes the substrate in the prior art. This fundamentally avoids the problems of sapphire residue and GaN film damage caused by the LLO process. At the same time, the epitaxial stack of the light-emitting chip is embedded into the substrate pits one by one through the protrusion structure. This can effectively disperse stress during the bonding of the driving chip and the light-emitting chip and subsequent processing, reduce the warping phenomenon after the wafer is cut into dies, and significantly improve the preparation yield. The pre-curved surface shape of the pits on the substrate corresponds one-to-one with the pre-curved surface shape of the protrusion structure of the epitaxial stack, and is completely consistent with the projection shape and position of the pixel unit on the substrate. The curved surface structure can optimize the light propagation path, reduce the total internal reflection loss of light at the interface between the substrate and the epitaxial stack, improve the effective emission rate of the light from the light-emitting layer, and solve the problem of low light efficiency. The protrusion structure corresponds one-to-one with the pit and matches the pixel unit, which can form a physical constraint on the light generated by each pixel unit, restrict the light from spreading to adjacent pixel units, thereby reducing the optical crosstalk between pixels and improving the pixel crosstalk problem.

[0085] Please see Figure 3 , Figure 3This 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 S31: Provide a driver chip.

[0086] For example, a driver chip adapted to a micro light-emitting device is provided. The driver chip includes a driver substrate and a driver circuit disposed on one side of the driver substrate. The driver substrate is made of silicon-based material, and the driver circuit has an array structure. Each driver circuit unit corresponds to a subsequent pixel unit, which can precisely control the light-emitting switch and brightness of the pixel unit. The surface of the driver chip is cleaned to completely remove the surface oxide layer and impurity particles, ensuring the electrical connection stability of the subsequent bonding process. It serves as a backup core driver component for the micro light-emitting device.

[0087] Step S32: Provide a substrate and form a plurality of recesses with a preset curved shape on one side of the substrate.

[0088] For example, a substrate is provided, the surface of which is polished to a mirror-like flat state. A hemispherical shape is selected as the preset curved surface shape. Multiple pits are prepared on the side of the substrate facing the subsequent epitaxial stack using photolithography and wet etching processes. First, photoresist is coated on the substrate surface using photolithography. After exposure and development, the array pattern of pits is defined. Then, wet etching is performed using a special etching solution. The etching time and temperature are controlled to prepare an array of hemispherical pits. The arrangement spacing of the pit array is consistent with the arrangement spacing of the subsequent pixel units. After etching, the remaining photoresist is removed and the substrate surface is cleaned to obtain a substrate with a hemispherical pit array. At the same time, marker points are prepared on the side of the substrate facing the epitaxial stack. The marker points include a first marker point surrounding the multiple pits and a second marker point reserved between adjacent pixel units.

[0089] Step S33: An epitaxial stack is formed on one side of the pit, and the epitaxial stack is etched to form a light-emitting chip. The epitaxial stack includes multiple protrusion structures with preset curved shapes and multiple pixel units. The protrusion structures are disposed on the opposite side of the pixel units. The number of protrusion structures is the same as the number of pixel units. The protrusion structures are embedded in the pit one by one. The shape of the pixel unit projected onto the substrate is the same as the shape of the protrusion structure projected onto the substrate. The position of the pixel unit projected onto the substrate is the same as the position of the protrusion structure projected onto the substrate.

[0090] For example, using a vapor deposition process, an epitaxial stack is sequentially grown on one side of a substrate with pits. The epitaxial stack, from the substrate side to the side away from the substrate, consists of a first semiconductor layer, a light-emitting layer, and a second semiconductor layer. Subsequently, a plasma etching process is used to pattern the epitaxial stack, resulting in an etched epitaxial stack. During the etching process, markers on the substrate are used for positioning, and the epitaxial stack is etched to form multiple independent pixel units. Simultaneously, on the side of each pixel unit away from the driver chip, a hemispherical protrusion structure matching the pit is retained. The number of protrusion structures is the same as the number of pixel units, corresponding one-to-one, and the protrusion structures are precisely positioned. The pixel is embedded in a pit in the substrate. During etching, the peripheral area of ​​the first semiconductor layer is exposed, and the surface of the pixel unit is the second semiconductor layer. After inspection, the shape of each pixel unit projected onto the substrate is exactly the same as the shape of the protrusion structure projected onto the substrate, and the projection positions are also completely coincident. Subsequently, a cathode electrode and an anode electrode are fabricated on the epitaxial stack after etching. The cathode electrode is electrically connected to the peripheral area of ​​the first semiconductor layer, and the anode electrode is electrically connected to the surface of the pixel unit. This ensures that the surface of the cathode electrode away from the first semiconductor layer and the surface of the anode electrode away from the pixel unit are at the same horizontal position, and finally a complete light-emitting chip is obtained.

[0091] Step S34: On the side of the epitaxial stack facing away from the substrate, the driving chip and the light-emitting chip are bonded to obtain a micro light-emitting device.

[0092] For example, on the side of the epitaxial stack of the light-emitting chip facing away from the substrate, transition layers are prepared on the surfaces of the cathode and anode electrodes, respectively. The transition layers can be made of metals such as nickel, titanium, or platinum, and are used to enhance the adhesion between the electrodes and the bonding layers. Subsequently, bonding layers are prepared, with some layers positioned between the cathode electrode and the driving circuit, and others between the anode electrode and the driving circuit. Using flip-chip bonding, the driving chip and the light-emitting chip are aligned and bonded, ensuring precise electrical connection between the driving circuit of the driving chip and the cathode and anode electrodes of the light-emitting chip. The bonding process controls appropriate temperature and pressure to ensure stable electrical connection and mechanical fixation of the bonding layers. After bonding, the device is cleaned and cured to remove residual impurities generated during the bonding process. A light-shielding layer, including a reflective layer, a light-absorbing layer, and an anti-reflective layer, can then be prepared on the side of the substrate facing away from the epitaxial stack. After electrical and luminescent performance testing, the device is confirmed to be able to drive normally and the pixel units emit light uniformly, ultimately yielding a qualified micro-light-emitting device.

[0093] It should be noted that the aforementioned micro-light-emitting devices can be applied not only to the projection parts of electronic devices such as optical projectors and head-up displays (HUDs), but also to the display parts of electronic devices, such as smartphones, smartwatches, laptops, tablets, dashcams, navigators, head-mounted devices, and any other devices with a display screen. They can also be applied to the lighting parts of electronic devices, such as vehicles, streetlights, and any other devices with lighting components.

[0094] 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.

[0095] 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 miniature light-emitting device, characterized in that, include: Driver chip; A light-emitting chip is bonded to a driving chip. The light-emitting chip includes a substrate and an epitaxial stack. The epitaxial stack is disposed on one side of the driving chip, and the substrate is disposed on the side of the epitaxial stack facing away from the driving chip. The side of the substrate facing the epitaxial stack includes multiple recesses with preset curved shapes. The epitaxial stack includes multiple protrusions with preset curved shapes and multiple pixel units. The protrusions are disposed on the opposite side of the pixel units. The number of protrusions is the same as the number of pixel units. Each protrusion is embedded in a recess. The shape of the pixel unit projected onto the substrate is the same as the shape of the protrusion projected onto the substrate. The position of the pixel unit projected onto the substrate is the same as the position of the protrusion projected onto the substrate.

2. The micro light-emitting device according to claim 1, characterized in that, The light-emitting chip also includes: A light-shielding layer is disposed on the side of the substrate away from the epitaxial stack. The light-shielding layer includes multiple light-transmitting areas and light-shielding areas surrounding the light-transmitting areas. The number of light-transmitting areas is the same as the number of protrusions. The shape of the light-transmitting areas projected onto the substrate is the same as the shape of the protrusions projected onto the substrate. The position of the light-transmitting areas projected onto the substrate is the same as the position of the protrusions projected onto the substrate.

3. The micro light-emitting device according to claim 2, characterized in that, The light-shielding layer includes a reflective layer, a light-absorbing layer, and an anti-reflective layer. The reflective layer is disposed on the side of the substrate opposite to the epitaxial stack, the light-absorbing layer is disposed on the side of the reflective layer opposite to the substrate, and the anti-reflective layer is disposed on the side of the light-absorbing layer opposite to the reflective layer.

4. The micro light-emitting device according to claim 1, characterized in that, The substrate has marking points on the side facing the epitaxial stack. The marking points include a first marking point and a second marking point. The first marking point surrounds the plurality of pits, and the second marking point is disposed between two adjacent pixel units.

5. The micro light-emitting device according to claim 1, characterized in that, The preset curved surface is hemispherical, the diameter of the pit is greater than or equal to the diameter of the pixel unit, and the radius of curvature of the pit is a preset multiple of the diameter of the pixel unit.

6. The micro light-emitting device according to claim 1, characterized in that: The epitaxial stack includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer. The first semiconductor layer is disposed on one side of the substrate, the light-emitting layer is disposed on the side of the first semiconductor layer away from the substrate, and the second semiconductor layer is disposed on the side of the light-emitting layer away from the first semiconductor layer. The peripheral region of the first semiconductor layer is exposed, and the surface of the pixel unit is the second semiconductor layer. The light-emitting chip further includes a cathode electrode and an anode electrode. The cathode electrode is electrically connected to the peripheral region of the first semiconductor layer, and the anode electrode is electrically connected to the surface of the pixel unit.

7. The micro light-emitting device according to claim 6, characterized in that, The cathode electrode is located away from the surface of the first semiconductor layer, and is at the same horizontal position as the anode electrode, which is located away from the surface of the pixel unit.

8. The micro light-emitting device according to claim 6, characterized in that: The driving chip includes a driving circuit and a driving substrate, with the driving circuit disposed on one side of the driving substrate. The micro light-emitting device further includes a bonding layer, a portion of which is disposed between the cathode electrode and the driving circuit, and a portion of which is disposed between the anode electrode and the driving circuit.

9. The micro light-emitting device according to claim 8, characterized in that, The micro light-emitting device further includes a transition layer disposed between the cathode electrode and the bonding layer, and between the anode electrode and the bonding layer.

10. A method for fabricating a micro light-emitting device, characterized in that, include: Provide driver chips; A substrate is provided, and a plurality of recesses with a predetermined curved shape are formed on one side of the substrate; An epitaxial stack is formed on one side of the recess, and the epitaxial stack is etched to form a light-emitting chip. The epitaxial stack includes multiple protrusion structures with preset curved shapes and multiple pixel units. The protrusion structures are disposed on the opposite side of the pixel units. The number of protrusion structures is the same as the number of pixel units. The protrusion structures are embedded in the recess one by one. The shape of the pixel unit projected onto the substrate is the same as the shape of the protrusion structure projected onto the substrate. The position of the pixel unit projected onto the substrate is the same as the position of the protrusion structure projected onto the substrate. On the side of the epitaxial stack facing away from the substrate, the driving chip and the light-emitting chip are bonded to obtain a micro light-emitting device.

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