Micro light emitting diode and preparation method and transfer method thereof

Abstract

The present application provides a micro light emitting diode and its manufacturing method and transfer method. The micro light emitting diode at least includes an epitaxial structure, a connecting electrode and a roughening part on the epitaxial structure. The epitaxial structure has opposite first and second surfaces, the longitudinal section of the first surface is a plane, and the longitudinal section of the second surface includes a continuous first part, a second part and a third part, the first and third parts are curved towards the profile line outside the light emitting area of the epitaxial structure, and the second part is a plane. The connecting electrode is above the epitaxial structure and electrically connected with the epitaxial structure. The roughening area is below the epitaxial structure and on the part of the surface of the second surface away from the first surface. The roughening part can be a connecting surface or a contact surface of the epitaxial structure to connect with other hierarchical structures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor light-emitting devices, in particular to a micro light-emitting diode and a preparation method and a transfer method thereof. BACKGROUND

[0002] Micro LED display technology uses micron-scale LEDs as light-emitting pixel units, which are assembled onto a driving panel to form a high-density LED array display technology. Micro LED has the advantages of low power consumption, high brightness, ultra-high resolution, ultra-high color saturation, fast response speed, low energy consumption, long service life, etc. In the display aspect, compared with LCD and OLED, it has greater advantages in brightness, resolution, contrast, energy consumption, service life, response speed and thermal stability.

[0003] The application of Micro LED will expand from flat panel display to AR / VR / MR, spatial display, flexible transparent display, wearable / implantable optoelectronic devices, optical communication / optical interconnection, medical detection, intelligent car lights and many other fields. Micro LED display technology has been gradually mass-produced and put into practical commercial applications, and the efficiency and yield of Micro LED mass transfer greatly affect the progress of the mass production process of Micro LED display technology. At present, the mainstream technology of Micro LED mass transfer is laser transfer technology. Laser transfer technology uses a specific wavelength of laser to act on the interface between the glue at the bottom of the chip and the substrate, and then generates a thermal chemical reaction to separate the interface between the glue and the substrate, thereby transferring the chip.

[0004] The size of Micro LED is smaller than that of conventional LED, and the spacing between chips also becomes very small. In the process of Micro LED mass transfer using laser transfer technology, when the laser irradiates the bottom of the chip for alignment, alignment deviation may occur, which affects the transfer yield of the chip, or the laser irradiates the chip that does not need to be transferred, resulting in mistransfer, thereby affecting the efficiency of Micro LED mass transfer. In addition, the design angle of the sidewall region of the conventional Micro LED chip is nearly a right angle, which reduces the light output of the sidewall region of the chip, resulting in a decrease in the light output efficiency of the Micro LED chip.

[0005] Therefore, in the micro light-emitting diode, how to improve the design of the chip sidewall region to improve the light output efficiency of the micro light-emitting diode, and at the same time improve the efficiency and yield in the laser mass transfer of the micro light-emitting diode, has become one of the technical problems to be solved by the technical personnel in the field. SUMMARY

[0006] An embodiment of the present application provides a micro light emitting diode, which at least comprises: an epitaxial structure, having opposite first and second surfaces, a longitudinal section of the first surface being a plane, and a longitudinal section of the second surface comprising a continuous first part, a second part and a third part, the first and third parts being curved surfaces, and the second part being a plane; a connecting electrode, located above the epitaxial structure and electrically connected with the epitaxial structure; and a roughened part, located below the epitaxial structure and on a side of the second surface away from the first surface. The roughened part can serve as a main contact surface of the epitaxial structure, thereby reducing the contact area between the epitaxial structure and components such as a substrate.

[0007] In some embodiments, in the epitaxial structure, one end of each of the first and third parts is connected with one end of the first surface, and the other end of each of the first and third parts is connected with one end of the second part.

[0008] In some embodiments, the roughened part is located in a region of the second surface on a side of the second part away from the first surface. The epitaxial structure realizes small-area contact through the planar region (the second part) of the second surface.

[0009] In some embodiments, the length of the first surface along a horizontal direction is less than 50 microns, and the length of the second part of the second surface along the horizontal direction is less than 20 microns.

[0010] In some embodiments, the first and third parts of the second surface are respectively convex arc surfaces from the first surface to the second surface, and the length of each of the two ends of the first part and the two ends of the third part projected in the horizontal direction is greater than or equal to 5 microns and less than or equal to 20 microns. The arc surfaces of the first and third parts of the second surface are arranged to increase the light extraction rate of the sidewall of the epitaxial structure and improve the luminous brightness of the micro light emitting diode.

[0011] In some embodiments, the angle between the tangent line at the junction of the arc surface of each of the first and third parts and the second part and the horizontal direction is 30° to 75°.

[0012] In some embodiments, the distance between the upper surface of the connecting electrode and the second part of the second surface is 10 microns to 12 microns.

[0013] In some embodiments, the micro light emitting diode further comprises a substrate, and the substrate is connected with the roughened part through a colloid.

[0014] In some embodiments, the size of at least one side of the core particle of the micro light emitting diode is less than or equal to 50 microns.

[0015] The preparation method of the micro light emitting diode provided by the embodiment of the present application can be used to manufacture the micro light emitting diode with the foregoing structure, and at least includes the following steps: transferring and roughening the sheet-shaped epitaxial structure, bonding the sheet-shaped epitaxial structure on the growth substrate to the transfer substrate and removing the growth substrate, roughening the surface of the sheet-shaped epitaxial structure away from the transfer substrate to form a roughened part; segmenting the sheet-shaped epitaxial structure, performing development etching on the sheet-shaped epitaxial structure on the transfer substrate to segment the sheet-shaped epitaxial structure into a plurality of epitaxial structures spaced from each other; sidewall etching of the epitaxial structure, etching the plurality of epitaxial structures on the transfer substrate to make the surface of the sidewall region of the epitaxial structure away from the transfer substrate be a curved surface; and transferring the epitaxial structure, bonding the plurality of epitaxial structures to the substrate, and bonding the roughened part of the epitaxial structure to the substrate through the colloid, so as to manufacture a plurality of array-distributed micro light emitting diodes on the substrate.

[0016] In some embodiments, the roughened part is convex, and the micro light emitting diode is provided with a connecting electrode on the surface away from the substrate.

[0017] The transferring method of the micro light emitting diode provided by the embodiment of the present application can be used to transfer the micro light emitting diode with the foregoing structure, and at least includes the following steps: providing a substrate, the substrate being provided with a plurality of array-distributed micro light emitting diodes through the colloid; providing a laser source, the laser source being located on the side of the substrate away from the micro light emitting diode; laser peeling and transferring, starting the laser source, and making the laser emitted by the laser source at least irradiate the area of the substrate provided with the colloid, so as to peel the micro light emitting diode from the substrate and transfer to the driving substrate.

[0018] In some embodiments, the interval between the two adjacent micro light emitting diodes on the substrate is 2-5 microns.

[0019] In some embodiments, the irradiation area of the laser emitted by the laser source is smaller than the projection area of the micro light emitting diode in the projection plane of the substrate.

[0020] Other features and advantages of the present application will be described in the following description and, in part, will become apparent from the description or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without any creative effort.

[0022] Figure 1Figure 1 is a schematic diagram of a conventional micro-LED.

[0023] Figure 2 Figure 2 is a schematic diagram of a cross section of an embodiment of the micro-LED.

[0024] Figure 3 Figure 3 is a schematic diagram of a cross section of another embodiment of the micro-LED.

[0025] Figure 4 Figure 4 is a schematic diagram of a light emitting micro-LED. Figure 2

[0026] Figure 5 Figure 5 is a schematic diagram of a process for manufacturing the micro-LED.

[0027] Figures 6 to 10 Figure 6 is a schematic diagram of a process for manufacturing the micro-LED.

[0028] Figure 11 Figure 7 is a schematic diagram of a transfer method for the micro-LED.

[0029] Reference numerals: 1, 3 - micro-LED; 2, 10 - substrate; 20 - epitaxial structure; 21 - first surface; 22 - second surface; 22a - first portion; 22b - second portion; 22c - third portion; 23a - first connection region; 23c - second connection region; 30 - connection electrode; 40 - roughened portion; 4, 50 - colloid; 5, 60 - laser source; L1, L2, L3 - length; H1, H2 - spacing; S1, S2 - irradiation area; 00 - growth substrate; 20' - sheet-shaped epitaxial structure; 01 - transfer substrate; 02 - bonding layer; a - included angle. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The technical features designed in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0031] Please refer to Figure 1 , Figure 1 Figure 1 is a schematic diagram of a conventional micro-LED. Figure 1 ​Figure 1 is a schematic diagram of an embodiment of the present application. The laser transfer technology is used for mass transfer of the existing micro light emitting diode 3. The substrate 2 is provided with a plurality of arrayed micro light emitting diodes 3. The micro light emitting diodes 3 are arranged on the substrate 2 by the adhesive 4. The whole side surface of the micro light emitting diode 3 is bonded to the substrate 2 by the adhesive 4. The laser source 5 is arranged on the side of the substrate 2 away from the micro light emitting diode 3. The laser source 5 is started. The laser emitted by the laser source 5 irradiates the bonding surface between the micro light emitting diode 3 and the substrate 2. The laser irradiation generates heat to melt the adhesive 4, so that the micro light emitting diode 3 is separated from the substrate 2, thereby transferring the micro light emitting diode 3.

[0032] Figure 1 In the example, each surface of the micro light emitting diode 3 is regularly shaped. The spacing between the adjacent two micro light emitting diodes 3 is less than 10 microns and less than the length of each surface of the micro light emitting diode 3. In the projection surface of the substrate 2, the irradiation area S1 of the laser emitted by the laser source 5 is greater than or equal to the projection area of the micro light emitting diode 3. In this case, because the spacing between the adjacent two micro light emitting diodes 3 is very small, the laser is easily irradiated on the bonding adhesive 4 of the micro light emitting diode 3 and the substrate 2 which is not required to be transferred, so that the micro light emitting diode 3 is separated from the substrate 2, thereby affecting the yield and efficiency of the mass transfer of the micro light emitting diode 3, or causing the micro light emitting diode 3 to be mis-transferred.

[0033] Please refer to Figure 2 , Figure 2 Figure 2 is a schematic diagram of a cross section of an embodiment of the micro light emitting diode in the present application. In order to achieve at least one of the advantages or other advantages, an embodiment of the present application provides a micro light emitting diode 1, which at least includes: an epitaxial structure 20, a connecting electrode 30 and a roughened portion 40 arranged on the epitaxial structure 20.

[0034] The epitaxial structure 20 has opposite first and second surfaces 21 and 22. The second surface 22 is the main light emitting surface. The longitudinal section of the first surface 21 is a plane. The longitudinal section of the second surface 22 includes a continuous first portion 22a, a second portion 22b and a third portion 22c. The first and third portions 22a and 22c have curved profiles towards the outside of the light emitting area of the epitaxial structure 20. The second portion 22b is a plane. The connecting electrode 30 is arranged above the epitaxial structure 20 and is electrically connected to the epitaxial structure 20. Figure 2 In the example, the connecting electrode 30 is arranged on the surface of the first surface 21 of the epitaxial structure 20 away from the second surface 22 and directly connected to and adhered to the first surface 21. The roughened portion 40 is arranged below the epitaxial structure 20 and on the part of the surface of the second surface 22 away from the first surface 21. The roughened portion 40 can be used as a connecting surface or a contact surface of the epitaxial structure 20 to connect to other hierarchical structures.

[0035] The first portion 22a and the third portion 22c are connected to two ends of the first surface 21 respectively, and the other ends of the first portion 22a and the third portion 22c are connected to two ends of the second portion 22b respectively. In combination Figure 2 and Figure 3 Further description is made. Figure 2 The structure of the micro light emitting diode 1 in the design stage is shown in the schematic diagram, and the shape of each level structure is closer to the ideal state. Figure 3 The cross-sectional schematic diagram of another embodiment of the micro light emitting diode 1 in the present application is shown, which is a longitudinal cross-sectional view of the micro light emitting diode 1 closer to the actual product. The first portion 22a is a first connecting area 23a between one end of the first surface 21 and one end of the second portion 22b in the second surface 22, and the third portion 22c is a second connecting area 23c between the other end of the first surface 21 and the other end of the second portion 22b in the second surface 22. As Figure 3 It can be seen that the first connecting area 23a and the second connecting area 23c have etched step surfaces in the micro light emitting diode 1, so that the surface of the first connecting area 23a and the second connecting area 23c towards the outside of the light emitting area of the epitaxial structure 20 does not present an ideal smooth arc surface or curved surface. However, from Figure 3 It can be seen that the first connecting area 23a and the second connecting area 23c have etched step surfaces in the micro light emitting diode 1, so that the surface of the first connecting area 23a and the second connecting area 23c towards the outside of the light emitting area of the epitaxial structure 20 does not present an ideal smooth arc surface or curved surface. However, from

[0036] As Figure 2 It can be seen that the first connecting area 23a and the second connecting area 23c have etched step surfaces in the micro light emitting diode 1, so that the surface of the first connecting area 23a and the second connecting area 23c towards the outside of the light emitting area of the epitaxial structure 20 does not present an ideal smooth arc surface or curved surface. However, from

[0037] In some diagram examples, the roughening part 40 is regularly shaped and equally spaced, which is a design schematic diagram of the micro light emitting diode 1. However, in the actual finished product of the micro light emitting diode 1, due to the influence of various factors in the process, the actually formed roughening part 40 is convex, extending a certain length from the surface of the second portion 22b side of the second surface 22 to the outside of the epitaxial structure 20. The roughening part 40 can be cross-distributed in various shapes, and the shape can also be irregular.

[0038] Figure 2 In the example, the longitudinal cross-section of the roughened portion 40 is serrated and wavy, and these shapes are irregularly distributed. The protruding configuration of the roughened portion 40 ensures that the epitaxial structure 20 has sufficient contact surface to connect or adhere to other components such as the substrate and substrate. At the same time, when removing the substrate or substrate connected to the epitaxial structure 20, the roughened portion 40 can serve as an etching surface for the epitaxial structure 20, preventing the influence of accidental etching of the light-emitting area of ​​the epitaxial structure 20 during etching, thereby ensuring the light-emitting performance of the light-emitting area of ​​the epitaxial structure 20 after transfer.

[0039] Combination Figure 1 See Figure 4 , Figure 4 for Figure 2 The diagram shows the light emission of the miniature LED 1. Figure 1 In the existing micro light-emitting diode 3 shown, the two sides (which can be understood as the sides of the epitaxial structure) in the longitudinal section of the micro light-emitting diode 3 are planes, and the light emitted from the micro light-emitting diode 3 is emitted in a direction perpendicular to the sides and parallel to the outward direction. Figure 4 In the example, the two sides of the epitaxial structure 20 in the miniature light-emitting diode 1 ( Figure 4 The longitudinal sections of the first part 22a and the third part 22c) are curved surfaces. When the light emitted from the micro LED 1 passes through the curved side, the light emission direction is changed, increasing the light emission towards the second surface 22 of the epitaxial structure 20, increasing the edge light emission rate of the light-emitting area of ​​the epitaxial structure 20, and thus improving the light emission rate and luminous brightness of the micro LED 1.

[0040] See again Figure 2 In the epitaxial structure 20, the longitudinal section of the first surface 21 is planar, and the length L1 of the first surface 21 in the horizontal direction is less than 50 micrometers. In the second surface 22, the first portion 22a and the third portion 22c are curved surfaces, while the second portion 22b is planar. The length L2 of the second portion 22b in the horizontal direction is less than 20 micrometers. The second portion 22b serves as the main contact surface of the second surface 22, and is also the main contact surface or connecting surface on one side of the second surface 22 in the epitaxial structure 20.

[0041] The connecting electrode 30 is located above the first surface 21, and the bottom surface of the connecting electrode 30 is directly connected and attached to the top surface (or upper surface) of the first surface 21. The distance H1 between the upper surface of the connecting electrode 30 and the second portion 22b of the second surface 22 is 10 micrometers to 12 micrometers.

[0042] The first portion 22a and the third portion 22c of the second surface 22 are arc-shaped surfaces protruding from the first surface 21 toward the second surface 22, and the arc-shaped surfaces are smooth surfaces. In other words, the first portion 22a and the third portion 22c are not provided with the roughened portion 40 on the side away from the first surface 21, and the roughened portion 40 is only provided in the region of the second portion 22b, which can serve as an extended contact surface of the main contact surface of the second portion 22b. The first portion 22a and the third portion 22c can serve as light exit surfaces of the region of the second surface 22. The length L3 of the two ends of the first portion 22a projected in the horizontal direction is greater than or equal to 5 microns and less than or equal to 20 microns. The length L3 of the two ends of the third portion 22c projected in the horizontal direction is greater than or equal to 5 microns and less than or equal to 20 microns. With Figure 1 Compared with the existing micro light-emitting diode 3 shown in the prior art, Figure 2 In the micro light-emitting diode 1 shown in the prior art, the main contact surface of the region of the second surface 22 of the epitaxial structure 20 is reduced, and the light exit surfaces of the two side regions are increased, thereby increasing the side light exit rate of the light-emitting region of the epitaxial structure 20 and improving the light exit rate and light-emitting brightness of the micro light-emitting diode 1.

[0043] In a preferred embodiment, the first portion 22a and the third portion 22c of the second surface 22 of the epitaxial structure 20 are symmetrically arranged relative to the second portion 22b. The first portion 22a and the third portion 22c are smooth arc-shaped surfaces or curved surfaces, and the tangent line at the junction of the arc-shaped surface or curved surface and the second portion 22b has an included angle a of 30° to 75° with the horizontal direction, thereby reducing the light exit surface of the second surface 22 as a contact surface, increasing the area of the light exit surface, and improving the light exit rate and light-emitting brightness of the micro light-emitting diode 1.

[0044] The micro light-emitting diode 1 can further include a substrate 10, which can be connected or bonded to the roughened portion 40 through the adhesive 50. Depending on the process of the micro light-emitting diode 1 or the use scenario, the substrate 10 can be a temporary substrate, or a transfer substrate, or a driving substrate, or a conductive substrate, a driving circuit board, a metal substrate, etc. In some embodiments, the conductive substrate can be an insulating substrate, such as an AlN substrate. In Figure 1 In the micro light-emitting diode 3 shown in the prior art, the substrate 2 is connected or bonded to the surface of the micro light-emitting diode 3 facing the substrate 2 through the adhesive 4. In Figure 2 In the example, the substrate 10 is connected or bonded to only the second portion 22b of the second surface 22 of the epitaxial structure 20 through the adhesive 50. In this case, the contact surface of the micro light-emitting diode 1 and the substrate 10 is reduced, which can ensure the adhesion and fixation of the micro light-emitting diode 1 on the substrate 10, reduce the etching surface between the micro light-emitting diode 1 and the substrate 10 in the subsequent transfer process, reduce the damage to the light-emitting region of the epitaxial structure 20 in the transfer process, increase the light exit rate, and improve the light exit brightness of the micro light-emitting diode 1.

[0045] The size of at least one side of the core particle of the micro light emitting diode 1 is less than or equal to 50 microns. The micro light emitting diode 1 can be a Mini LED, or a Micro LED. In Figure 2 In the embodiment, the side length of the side where the first surface 21 of the epitaxial structure 20 is located is less than or equal to 50 microns. The size of the core particle of the micro light emitting diode 1 can be 50 microns x N microns, where N is 50-300. For example, the size of the core particle of the micro light emitting diode 1 is 50 microns x 50 microns, 50 microns x 200 microns.

[0046] An embodiment of the present application provides a preparation method of a micro light emitting diode 1, which can be used to manufacture the micro light emitting diode 1 having the structure as described above. Figure 5 The flowchart of the preparation method of a preferred embodiment of the micro light emitting diode 1 in the present application is shown in FIG. 1. However, the preparation method and flow of the micro light emitting diode 1 in the present application are not limited to Figure 5 as shown in FIG. 1.

[0047] In combination with Figure 2 and Figure 5 Referring to Figures 6 to 10 , Figures 6 to 10 The flowchart of the preparation method of a preferred embodiment of the micro light emitting diode 1 in the present application is shown in FIG. 1. However, the preparation method and flow of the micro light emitting diode 1 in the present application are not limited to Figure 5 as shown in FIG. 1. Figure 2 The flowchart of the preparation method of a preferred embodiment of the micro light emitting diode 1 in the present application is shown in FIG. 1. However, the preparation method and flow of the micro light emitting diode 1 in the present application are not limited to

[0048] The preparation method of the micro light emitting diode 1 can at least include the following steps: transfer and roughening of the sheet-shaped epitaxial structure 20', segmentation of the sheet-shaped epitaxial structure, sidewall etching of the epitaxial structure, and transfer of the epitaxial structure. The specific implementation process of each step is described as follows.

[0049] Step S11: Transfer and roughening of the sheet-shaped epitaxial structure

[0050] Referring to Figure 6 , a sheet-shaped epitaxial structure 20' is grown on a growth substrate 00. The growth substrate 00 is located below the sheet-shaped epitaxial structure 20', and a connecting electrode 30 is provided above the sheet-shaped epitaxial structure 20'. In combination with Figure 6 Referring to Figure 7The epitaxial structure 20' on the growth substrate 00 is bonded to the transfer substrate 01, and the growth substrate 00 is then removed. A bonding layer 02 is provided above the connecting electrode 30 in the epitaxial structure 20'. The epitaxial structure 20' is bonded to the transfer substrate 01 through the bonding layer 02, thereby separating it from the growth substrate 00 and allowing for its removal. After the epitaxial structure 20' is bonded to the transfer substrate 01, the surface of the epitaxial structure 20' away from the transfer substrate 01 is roughened to form a roughened portion 40. The roughened portion 40 can serve as the main contact surface of the epitaxial structure 20', and can be connected or bonded to other structural layers in subsequent processes.

[0051] In a preferred embodiment, the roughened portion 40 is protruding and extends outward from the surface of the sheet-like epitaxial structure 20'. Figure 6 In the example, the longitudinal cross-section of the roughened portion 40 is toothed. The protruding shape of the roughened portion 40 ensures that the sheet-like epitaxial structure 20' has sufficient contact surface to connect or adhere to other components such as the substrate and substrate. At the same time, in subsequent processes, the roughened portion 40 can serve as the etching surface of the sheet-like epitaxial structure 20', preventing accidental etching of the sheet-like epitaxial structure 20' during etching, thereby ensuring that the sheet-like epitaxial structure 20' has good light-emitting performance after the subsequent processes are completed.

[0052] Step S12: Segmentation of the sheet-like epitaxial structure

[0053] See Figure 8 For example Figure 7 The sheet-like epitaxial structure 20' containing the roughened portion 40 shown is segmented to obtain individual, independent epitaxial structures 20. Specifically, the sheet-like epitaxial structure 20' can be developed and etched above the roughened portion 40 using photolithography to segment the sheet-like epitaxial structure 20' into several mutually spaced epitaxial structures 20. In some embodiments, a conductivity-coupled plasma etching (ICP) machine can be used to etch and segment the sheet-like epitaxial structure 20' during photolithography.

[0054] Step S13: Etching of the sidewalls of the epitaxial structure

[0055] See Figure 9, after step S12, the transfer substrate 01 has a plurality of epitaxial structures 20 arranged in an array. The connecting electrodes 30 in the epitaxial structures 20 are bonded to the transfer substrate 01 through the bonding layer 02, and the roughened portions 40 are on the surface of the epitaxial structures 20 away from the transfer substrate 01. Each epitaxial structure 20 is etched so that the sidewall region of the epitaxial structure 20 away from the surface of the transfer substrate 01 is curved, and the roughened portions 40 of the sidewall region of the epitaxial structure 20 are etched away. After the etching, the bonding layer 02 has a certain spacing with the epitaxial structure 20, and in the subsequent process of transferring or moving the epitaxial structure 20 out of the transfer substrate 01, the epitaxial structure 20 can be prevented from being etched too much or mis-etched. As shown in Figure 9 , the sidewall region of the epitaxial structure 20 is a convex arc surface from the side of the transfer substrate 01 to the side of the roughened portion 40.

[0056] Step S14: Transfer of the epitaxial structure

[0057] Referring to Figure 10 , the bonding layer or the adhesive 50 is arranged above the roughened portion 40 in the epitaxial structure 20. The epitaxial structure 20 is bonded or attached to the substrate 10 through the roughened portion 40 and the bonding layer or the adhesive 50, and the transfer substrate 01 and the bonding layer 02 are removed, thereby obtaining a plurality of micro light emitting diodes 1 arranged in an array on the substrate 10. The connecting electrodes 30 are on the surface of the micro light emitting diode 1 away from the substrate 10.

[0058] Figure 11 A schematic diagram of a transfer method of a micro light emitting diode according to an embodiment of the present application is shown. To achieve at least one of the advantages or other advantages, an embodiment of the present application provides a transfer method of a micro light emitting diode, which can transfer or mass transfer the micro light emitting diode 1 as shown in Figure 2 . Please refer to Figure 2 , Figure 10 Referring to Figure 11 , the laser transfer technology is used to mass transfer the micro light emitting diode 1 in this embodiment.

[0059] As shown in Figure 11 , the substrate 10 has a plurality of micro light emitting diodes 1 arranged in an array, and the micro light emitting diodes 1 can be attached or bonded to the substrate 10 through the adhesive 40 or the bonding. Figure 11 In the embodiment, the epitaxial structure 20 in the micro light emitting diode 1 is attached or bonded to the substrate 10 through the roughened portion 40 and the adhesive 50. The substrate 10 can be a transfer substrate or a transfer substrate. Figure 11 In the embodiment, the laser source 60 is located on the side of the substrate 10 away from the micro light emitting diode 1 and faces the side surface of the epitaxial structure 20 having the roughened portion 40. The laser source 60 is started, and the laser emitted by the laser source 60Figure 10 The laser source 60 is arranged to irradiate the laser light on the area of the substrate 10 where the micro light emitting diode 1 is arranged. The irradiation area S1 of the laser light is greater than or equal to the projection area of the micro light emitting diode 1 on the projection plane of the substrate 10. The irradiation area S1 of the laser light is less than or equal to the projection area of the micro light emitting diode 1 on the projection plane of the substrate 10.

[0060] In combination Figure 1 Referring to Figure 11 . Figure 1 The interval between the micro light emitting diodes 3 arranged on the substrate 2 is less than or equal to 10 microns. The irradiation area S1 of the laser light emitted by the laser source 5 is greater than or equal to the projection area of the micro light emitting diode 3 on the projection plane of the substrate 2. Figure 11 In the example, the interval H2 between the adjacent two micro light emitting diodes 1 arranged on the substrate 10 is 2 microns to 5 microns. It can be understood that the micro light emitting diodes 1 arranged on the substrate 10 are densely arranged and the interval between the adjacent two micro light emitting diodes 1 is very small. In this case, if the laser light emitted by the laser source 60 is irradiated on the entire surface of the epitaxial structure 20 facing the substrate 10 as in the prior art, the adjacent micro light emitting diode 1 which is not required to be transferred will be separated from the substrate 10 and the connection stability of the micro light emitting diode 1 and the substrate 10 will be affected. Figure 1 In the example, the interval H2 between the adjacent two micro light emitting diodes 1 arranged on the substrate 10 is 2 microns to 5 microns. It can be understood that the micro light emitting diodes 1 arranged on the substrate 10 are densely arranged and the interval between the adjacent two micro light emitting diodes 1 is very small. In this case, if the laser light emitted by the laser source 60 is irradiated on the entire surface of the epitaxial structure 20 facing the substrate 10 as in the prior art, the adjacent micro light emitting diode 1 which is not required to be transferred will be separated from the substrate 10 and the connection stability of the micro light emitting diode 1 and the substrate 10 will be affected.

[0061] Figure 11 In the example, the irradiation area S2 of the laser light emitted by the laser source 60 is less than the projection area of the micro light emitting diode 1 on the projection plane of the substrate 10. The roughened portion 40 arranged on the second portion 22b of the second surface 22 of the epitaxial structure 20 of the micro light emitting diode 1 serves as a contact surface and is connected and adhered to the substrate 10. When the laser light emitted by the laser source 60 is irradiated on the substrate 10 and the epitaxial structure 20, the laser light is mainly irradiated on the connection area of the roughened portion 40 of the epitaxial structure 20 and the substrate 10. The projection area of the contact surface of the epitaxial structure 20 and the substrate 10 irradiated by the laser light on the projection plane of the substrate 10 is less than the projection area of the epitaxial structure 20. Figure 11 In the example, the irradiation area S2 of the laser light emitted by the laser source 60 is less than the projection area of the micro light emitting diode 1 on the projection plane of the substrate 10. The roughened portion 40 arranged on the second portion 22b of the second surface 22 of the epitaxial structure 20 of the micro light emitting diode 1 serves as a contact surface and is connected and adhered to the substrate 10. When the laser light emitted by the laser source 60 is irradiated on the substrate 10 and the epitaxial structure 20, the laser light is mainly irradiated on the connection area of the roughened portion 40 of the epitaxial structure 20 and the substrate 10. The projection area of the contact surface of the epitaxial structure 20 and the substrate 10 irradiated by the laser light on the projection plane of the substrate 10 is less than the projection area of the epitaxial structure 20. Figure 1 In the example, the irradiation area S2 of the laser light emitted by the laser source 60 is less than the projection area of the micro light emitting diode 1 on the projection plane of the substrate 10. The roughened portion 40 arranged on the second portion 22b of the second surface 22 of the epitaxial structure 20 of the micro light emitting diode 1 serves as a contact surface and is connected and adhered to the substrate 10. When the laser light emitted by the laser source 60 is irradiated on the substrate 10 and the epitaxial structure 20, the laser light is mainly irradiated on the connection area of the roughened portion 40 of the epitaxial structure 20 and the substrate 10. The projection area of the contact surface of the epitaxial structure 20 and the substrate 10 irradiated by the laser light on the projection plane of the substrate 10 is less than the projection area of the epitaxial structure 20. Figure 11 In the example, the laser light emitted by the laser source 60 will not irradiate the side wall area of the epitaxial structure 20 or the interval area between the adjacent two micro light emitting diodes 1 and the micro light emitting diode 1 will not be transferred or the contact between the micro light emitting diode 1 and the substrate 10 will be poor.

[0062] The micro light emitting diode 1 provided by the present application is arranged on the substrate 10. Figure 2Compared with the existing micro light emitting diode, the side wall region of the epitaxial structure 20 is not arranged in a regular shape of a conventional vertical structure, but arranged in a curved or arc surface structure, which can increase the light extraction efficiency of the epitaxial structure side wall region and improve the light emitting brightness. In addition, the contact area between the epitaxial structure 20 and the substrate 10 in the micro light emitting diode 1 is reduced. When the laser transfer technology is used to transfer the micro light emitting diode 1, the irradiation area of the laser on the micro light emitting diode 1 (or the spot projection area of the laser) is smaller. The micro light emitting diode 1 that needs to be transferred can be peeled off and transferred, and the irradiation area of the laser is prevented from being too large to cause the micro light emitting diode 1 that does not need to be transferred to be mis-transferred or to have poor contact with the substrate 10. The micro light emitting diode 1 (as shown in Figure 2 The micro light emitting diode 1 provided by the present application can have a higher overall light extraction efficiency and achieve high-brightness light emission. In addition, when the pitch of the micro light emitting diode 1 array is small, the micro light emitting diode 1 that needs to be transferred can be accurately aligned, peeled off and transferred in the laser transfer, which improves the transfer yield and efficiency of the micro light emitting diode 1 mass transfer.

[0063] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the above embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A micro light emitting diode, characterized by: At least comprising: An epitaxial structure having opposite first and second surfaces, a longitudinal section of the first surface being a plane, a longitudinal section of the second surface comprising a continuous first portion, a second portion and a third portion, the first and third portions being curved towards a profile line outside a light emitting region of the epitaxial structure, and the second portion being a plane; A connecting electrode located above the epitaxial structure and electrically connected to the epitaxial structure; and A roughened portion located below the epitaxial structure and on a portion of the second surface away from the first surface; The first and third portions are respectively convex arc surfaces from the first surface towards the second surface, and a length of a horizontal projection of both ends of the first portion and both ends of the third portion is greater than or equal to 5 microns and less than or equal to 20 microns; An included angle between a tangent line at a junction of the arc surfaces in the first and third portions and the second portion and a horizontal direction is 30° to 75°, and a light emitting surface of the second surface region comprises the first and third portions. In the epitaxial structure, one end of the first and third portions is connected to both ends of the first surface, and the other end is connected to both ends of the second portion.

2. The micro light emitting diode of claim 1, wherein: A length of the first surface along a horizontal direction is less than 50 microns, and a length of the second portion of the second surface along a horizontal direction is less than 20 microns.

3. The micro light emitting diode of claim 1, wherein: A distance between an upper surface of the connecting electrode and the second portion of the second surface is 10 microns to 12 microns.

4. The micro light emitting diode of claim 1, wherein: The micro light emitting diode further comprises a substrate connected to the roughened portion through a colloid.

5. The micro light emitting diode according to any one of claims 1 to 4, wherein: At least one side of a core particle of the micro light emitting diode has a size less than or equal to 50 microns.

6. The micro light emitting diode of claim 1, wherein: At least comprising the following steps:

7. A method of fabricating a micro light emitting diode, characterized by: Transfer and roughening of a sheet-shaped epitaxial structure, bonding a sheet-shaped epitaxial structure on a growth substrate to a transfer substrate and removing the growth substrate, roughening a surface of the sheet-shaped epitaxial structure away from the transfer substrate to form a roughened portion; Segmentation of the sheet-shaped epitaxial structure, developing and etching the sheet-shaped epitaxial structure on the transfer substrate to segment the sheet-shaped epitaxial structure into a plurality of epitaxial structures spaced apart from each other; Side wall etching of the epitaxial structure, etching the plurality of epitaxial structures on the transfer substrate so that a surface of a side wall region of the epitaxial structure away from the transfer substrate is curved; And Transfer of the epitaxial structure, bonding the plurality of epitaxial structures to a substrate, and bonding the roughened portion of the epitaxial structure to the substrate through a colloid, thereby obtaining a plurality of micro light emitting diodes arrayed on the substrate, the micro light emitting diode being the micro light emitting diode according to any one of claims 1 to 6. The roughened portion is convex, and the micro light emitting diode is provided with a connecting electrode on a surface away from the substrate.

8. The method of claim 7, wherein the method further comprises: At least comprising the following steps:

9. A method of transferring micro light emitting diodes, characterized by: ​ A substrate is provided, wherein a plurality of arrayed micro light emitting diodes are arranged on the substrate by a colloid, and the micro light emitting diodes are as claimed in any one of claims 1 to 6. A laser source is provided, wherein the laser source is located on a side of the substrate away from the micro light emitting diodes. Laser peeling and transferring, starting the laser source, and the laser emitted by the laser source at least irradiates the area on the substrate provided with the colloid, so that the micro light emitting diodes are peeled off from the substrate and transferred to a driving substrate.

10. The method of claim 9, wherein: The spacing between two adjacent micro light emitting diodes is 2-5 microns.

11. The method of claim 10, wherein: In the projection plane of the substrate, the irradiation area of the laser emitted by the laser source is smaller than the projection area of the micro light emitting diodes.

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