Micro light emitting diode

Abstract

The present application provides a micro light emitting diode and its manufacturing method and transfer method. The micro light emitting diode at least comprises: an epitaxial structure having opposite first and second surfaces, the longitudinal section of the first surface is a plane, and the longitudinal section of the second surface comprises 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. A connecting electrode is located above the epitaxial structure and is electrically connected with the epitaxial structure. A roughening area is located below the epitaxial structure and on a part of the surface of the second surface away from the first surface. The roughening part can be used as a connecting surface or a contact surface of the epitaxial structure to connect with other hierarchical structures.

Description

[0001] This application is a divisional application of application number 2022112832304 (Invention title: Miniature light-emitting diode and its preparation and transfer method, application date: October 20, 2022). Technical Field

[0002] This invention relates to the field of semiconductor light-emitting device technology, and in particular to a micro light-emitting diode and its fabrication and transfer methods. Background Technology

[0003] Micro LED (micro-light-emitting diode) display technology uses self-emissive, micrometer-sized LEDs as light-emitting pixel units, assembling them onto a driving panel to form a high-density LED array. Micro LED has advantages such as low power consumption, high brightness, ultra-high resolution, ultra-high color saturation, fast response speed, low energy consumption, and long lifespan. In terms of display, it has greater advantages than LCD and OLED in terms of brightness, resolution, contrast ratio, energy consumption, lifespan, response speed, and thermal stability.

[0004] The applications of Micro LED will expand from flat panel displays to numerous fields such as AR / VR / MR, spatial displays, flexible transparent displays, wearable / implantable optoelectronic devices, optical communication / optical interconnection, medical detection, and smart automotive lighting. Micro LED display technology is gradually entering mass production and being used in practical commercial applications. The efficiency and yield of Micro LED mass transfer significantly impact the rapid advancement of Micro LED display technology's mass production process. Currently, the mainstream technology for Micro LED mass transfer is laser transfer technology. Laser transfer technology uses a specific wavelength of laser light to act on the interface between the adhesive and the substrate at the bottom of the chip, thereby generating a thermochemical reaction that separates the adhesive and substrate at the interface, thus transferring the chip.

[0005] Micro LEDs are smaller than conventional LEDs, and the spacing between chips is also much smaller. During the mass transfer of Micro LEDs using laser transfer technology, misalignment can occur when the laser irradiates the bottom of the chip for alignment, affecting the transfer yield. Alternatively, the laser may irradiate chips that don't need to be transferred, causing mis-transfer and impacting the efficiency of the mass transfer. Furthermore, the sidewalls of conventional Micro LED chips are designed with near-right angles, reducing the light output from these areas and thus lowering the light extraction efficiency of the Micro LED chips.

[0006] Therefore, improving the design of the chip sidewall region in micro LEDs to enhance their light extraction efficiency, while simultaneously improving the efficiency and yield of laser mass transfer in micro LEDs, has become one of the technical challenges that urgently need to be addressed by those skilled in the art. Summary of the Invention

[0007] An embodiment of the present invention provides a miniature light-emitting diode, which may include at least: an epitaxial structure having opposing first and second surfaces, the longitudinal section of the first surface being planar, and the longitudinal section of the second surface including a continuous first portion, a second portion, and a third portion, the first and third portions being curved surfaces, and the second portion being planar; 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 the side of the second surface away from the first surface. The roughened portion can serve as the main contact surface of the epitaxial structure, reducing the contact area between the epitaxial structure and components such as a substrate.

[0008] In some embodiments, in the epitaxial structure, one end of the first portion and the third portion are respectively connected to the two ends of the first surface, and the other end is respectively connected to the two ends of the second portion.

[0009] In some embodiments, the roughened portion is located on the second part of the second surface, on the side away from the first surface. The epitaxial structure achieves small-area contact through the planar region (second part) in the second surface.

[0010] In some embodiments, the length of the first surface in the horizontal direction is less than 50 micrometers, and the length of the second portion in the second surface in the horizontal direction is less than 20 micrometers.

[0011] In some embodiments, the first and third portions of the second surface are respectively convex arc-shaped surfaces extending from the first surface toward the second surface, and the horizontal projection lengths of the two ends of the first portion and the two ends of the third portion are respectively greater than or equal to 5 micrometers and less than or equal to 20 micrometers. The arc-shaped surface configuration of the first and third portions of the second surface can increase the light extraction efficiency of the epitaxial structure sidewalls and improve the luminous brightness of the micro LED.

[0012] In some embodiments, the angle between the tangent at the junction of the arcuate surface in the first and third portions and the second portion and the horizontal direction is 30° to 75°.

[0013] In some embodiments, the distance between the upper surface of the connecting electrode and the second portion of the second surface is 10 micrometers to 12 micrometers.

[0014] In some embodiments, the micro-photodiode may further include a substrate, which is connected to the roughened portion via a colloid.

[0015] In some embodiments, the size of at least one side of the micro LED chip is less than or equal to 50 micrometers.

[0016] An embodiment of the present invention provides a method for fabricating a micro light-emitting diode (LED), which can be used to manufacture a micro LED having the aforementioned structure, comprising at least the following steps: transfer and roughening of a sheet-like epitaxial structure, bonding a sheet-like epitaxial structure on a growth substrate to a transfer substrate and removing the growth substrate, roughening the surface of the sheet-like epitaxial structure away from the transfer substrate to form a roughened portion; segmentation of the sheet-like epitaxial structure, developing and etching the roughened sheet-like epitaxial structure on the transfer substrate to segment the sheet-like epitaxial structure into several mutually spaced epitaxial structures; sidewall etching of the epitaxial structure, etching several epitaxial structures on the transfer substrate so that the surface of the sidewall region of the epitaxial structure away from the transfer substrate is curved; and transfer of the epitaxial structure, bonding several epitaxial structures to a substrate, wherein the roughened portion of the epitaxial structure is bonded to the substrate by a colloid, thereby obtaining several micro LEDs distributed in an array on the substrate.

[0017] In some embodiments, the roughened portion is protruding, and a connection electrode is provided on the surface of the micro LED away from the substrate.

[0018] An embodiment of the present invention provides a method for transferring a micro light-emitting diode (LED), which can transfer a micro LED having the aforementioned structure, and includes at least the following steps: providing a substrate on which a plurality of micro LEDs are arranged in an array by means of an adhesive; providing a laser source located on the side of the substrate away from the micro LEDs; laser peeling and transfer, activating the laser source, wherein the laser emitted by the laser source irradiates at least the area on the substrate where the adhesive is provided, so that the micro LEDs are peeled off from the substrate and transferred to a driving substrate.

[0019] In some embodiments, the spacing between two adjacent micro-light-emitting diodes on the substrate is 2 micrometers to 5 micrometers.

[0020] In some embodiments, the irradiation area of ​​the laser emitted by the laser source within the projection surface of the substrate is smaller than the projection area of ​​the micro light-emitting diode.

[0021] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram illustrating the transfer of an existing miniature light-emitting diode; Figure 2 This is a cross-sectional schematic diagram of an embodiment of the miniature light-emitting diode in this invention; Figure 3 This is a cross-sectional schematic diagram of another embodiment of the miniature light-emitting diode in this invention; Figure 4 for Figure 2 The diagram shows the light emission of a miniature light-emitting diode. Figure 5 This is a schematic diagram of the fabrication method of a miniature light-emitting diode according to an embodiment of the present invention; Figures 6 to 10 This is a schematic diagram illustrating the process of one embodiment of the fabrication method of the miniature light-emitting diode in this invention; and Figure 11 This is a schematic diagram of a transfer method for a micro light-emitting diode according to an embodiment of the present invention.

[0024] Reference numerals: 1, 3 - micro light-emitting diodes; 2, 10 - substrate; 20 - epitaxial structure; 21 - first surface; 22 - second surface; 22a - first part; 22b - second part; 22c - third part; 23a - first connection region; 23c - second connection region; 30 - connection electrode; 40 - roughened part; 4, 50 - colloid; 5, 60 - laser source; L1, L2, L3 - length; H1, H2 - spacing; S1, S2 - irradiation area; 00 - growth substrate; 20' - sheet-like epitaxial structure; 01 - transfer substrate; 02 - bonding layer; a - included angle. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Please see Figure 1 , Figure 1 This is a schematic diagram of the transfer of an existing miniature light-emitting diode. Figure 1This is a schematic diagram illustrating the implementation of mass transfer of existing micro-LEDs 3 using laser transfer technology. A plurality of micro-LEDs 3 are arrayed on a substrate 2, and the micro-LEDs 3 are attached to the substrate 2 via a colloid 4. One entire surface of each micro-LED 3 is bonded to the substrate 2 via the colloid 4. A laser source 5 is located on the side of the substrate 2 away from the micro-LEDs 3. When the laser source 5 is activated, the laser beam emitted by the laser source 5 covers the bonding surface between the micro-LEDs 3 and the substrate 2. The heat generated by the laser irradiation melts the colloid 4, thereby separating the micro-LEDs 3 from the substrate 2, thus transferring the micro-LEDs 3.

[0027] Figure 1 In the example, the faces of the micro-LEDs 3 are arranged in a regular shape, and the spacing between two adjacent micro-LEDs 3 is less than 10 micrometers and smaller than the side length of each face of the micro-LED 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 projected area of ​​the micro-LEDs 3. In this case, because the spacing between two adjacent micro-LEDs 3 is very small, the laser can easily irradiate the bonding colloid 4 between the micro-LEDs 3 that do not need to be transferred and the substrate 2, causing the micro-LEDs 3 to separate from the substrate 2, thereby affecting the yield and efficiency of the mass transfer of micro-LEDs 3, or causing mis-transfer of micro-LEDs 3.

[0028] Please see Figure 2 , Figure 2 This is a cross-sectional schematic diagram of an embodiment of a micro light-emitting diode according to the present invention. To achieve at least one or more of the aforementioned advantages, an embodiment of the present invention provides a micro light-emitting diode 1, which may include at least: an epitaxial structure 20 and a connecting electrode 30 and a roughened portion 40 disposed on the epitaxial structure 20.

[0029] The epitaxial structure 20 has a first surface 21 and a second surface 22, with the second surface 22 being the primary light-emitting surface. The longitudinal section of the first surface 21 is planar, and the longitudinal section of the second surface 22 includes a continuous first portion 22a, a second portion 22b, and a third portion 22c. The contour lines of the first portion 22a and the third portion 22c facing outwards from the light-emitting area of ​​the epitaxial structure 20 are curved, while the second portion 22b is planar. The connecting electrode 30 is located above the epitaxial structure 20 and is electrically connected to the epitaxial structure 20. Figure 2 In the example, the connecting electrode 30 is located on the surface of the first surface 21 of the epitaxial structure 20 away from the second surface 22, and is directly connected to and attached to the first surface 21. The roughened portion 40 is located below the epitaxial structure 20 and is located on a portion of the second surface 22 away from the first surface 21. The roughened portion 40 can serve as a connecting surface or contact surface of the epitaxial structure 20 to connect with other hierarchical structures.

[0030] One end of the first part 22a and the third part 22c are respectively connected to both ends of the first surface 21, and the other ends of the first part 22a and the third part 22c are respectively connected to both ends of the second part 22b. Figure 2 and Figure 3 Further explanation is needed. Figure 2 The diagram shown is a structural schematic of the miniature light-emitting diode 1 during the design phase. The shapes of each layer of the structure are closer to the ideal state. Figure 3 This is a cross-sectional view of another embodiment of the miniature light-emitting diode 1 of the present invention, which is a longitudinal cross-sectional view of the miniature light-emitting diode 1 closer to an actual product. The first part 22a is a first connection region 23a between one end of the first surface 21 and one end of the second part 22b of the second surface 22, and the third part 22c is a second connection region 23c between the other end of the first surface 21 and the other end of the second part 22b of the second surface 22. Figure 3 As shown, in the miniature light-emitting diode 1, the first connection region 23a and the second connection region 23c have stepped surfaces formed by etching, so that the surfaces of the first connection region 23a and the second connection region 23c facing the outer side of the light-emitting area of ​​the epitaxial structure 20 do not present an ideal smooth arc surface or curved surface. However, from Figure 3 It can be seen that the outline of the longitudinal section of the first connecting region 23a facing the outside of the light-emitting area of ​​the epitaxial structure 20 is curved, and the outline of the longitudinal section of the second connecting region facing the outside of the light-emitting area of ​​the epitaxial structure 20 is also curved.

[0031] like Figure 2 As shown, the longitudinal cross-section of the extensional structure 20 is approximately an inverted trapezoid, with two curved sides, unlike the two straight sides of a typical trapezoid. Specifically, the first surface 21 of the extensional structure 20 is the long side of the inverted trapezoid, the second portion 22b of the second surface 22 is the short side of the inverted trapezoid, and the first portion 22a and the third portion 22c of the second surface 22 are the two curved sides of the inverted trapezoid. The roughened portion 40 is located on the side of the second portion 22b of the second surface 22 of the extensional structure 20 that is away from the first surface 21. This can be understood as the roughened portion 40 extending outward from the surface of the second portion 22b of the second surface 22.

[0032] In some illustrated examples, the roughened portions 40 are of a regular shape and evenly spaced, which is a design schematic of the micro LED 1. However, in the actual finished product of the micro LED 1, due to the influence of various factors during the manufacturing process, the roughened portions 40 actually formed are convex, extending a certain length from the surface of the second part 22b on the second surface 22 towards the outside of the epitaxial structure 20. The roughened portions 40 can be distributed in various different shapes, and the shape can also be irregular.

[0033] 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.

[0034] 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 sides. Figure 4 In the example, the two sides of the epitaxial structure 20 in the micro LED 1 ( Figure 4 The longitudinal cross-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.

[0035] 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.

[0036] 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 part 22b of the second surface 22 is 10 micrometers to 12 micrometers.

[0037] 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 these arc-shaped surfaces are smooth. In other words, the roughened portion 40 is not provided on the side of the first portion 22a and the third portion 22c away from the first surface 21; the roughened portion 40 is only provided in the region of the second portion 22b, and can serve as an extension of the main contact surface of the second portion 22b. The first portion 22a and the third portion 22c can serve as the light-emitting surface of the region of the second surface 22. The horizontal projection length L3 of the two ends of the first portion 22a is greater than or equal to 5 micrometers and less than or equal to 20 micrometers. The horizontal projection length L3 of the two ends of the third portion 22c is greater than or equal to 5 micrometers and less than or equal to 20 micrometers. Figure 1 Compared to the existing miniature light-emitting diode 3 shown, Figure 2 In the micro light-emitting diode 1 shown, the main contact surface of the second surface 22 region of the epitaxial structure 20 is reduced, and the light-emitting surface of the two side regions is increased, thereby increasing the side light-emitting efficiency of the light-emitting region of the epitaxial structure 20 and thus improving the light-emitting efficiency and luminous brightness of the micro light-emitting diode 1.

[0038] 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 with respect to the second portion 22b. The first portion 22a and the third portion 22c are smooth arc-shaped surfaces or curved surfaces, and the angle α between the tangent at the connection between the arc-shaped surface or curved surface and the second portion 22b and the horizontal direction is 30° to 75°. This reduces the number of light-emitting surfaces of the second surface 22 used as contact surfaces and increases the area of ​​the light-emitting surface, thereby improving the light extraction efficiency and luminous brightness of the micro light-emitting diode 1.

[0039] The miniature photodiode 1 may also include a substrate 10, which can be connected or bonded to the roughened portion 40 via a colloid 50. Depending on the manufacturing process or application of the miniature photodiode 1, the substrate 10 may be a temporary substrate, a transfer substrate, a driving substrate, a conductive substrate, a driving circuit board, a metal substrate, etc. In some embodiments, the conductive substrate may be an insulating substrate, such as an AlN substrate. Figure 1 In the miniature photodiode 3 shown, the substrate 2 is fully contact-bonded or bonded to the surface of the miniature photodiode 3 facing the substrate 2 via a colloid 4. Figure 2 In this example, the substrate 10 is only in contact with or bonded to the second portion 22b of the second surface 22 of the epitaxial structure 20 via the colloid 50. In this case, the contact area between the micro-photodiode 1 and the substrate 10 is reduced, which ensures the adhesion and fixation of the micro-photodiode 1 on the substrate 10. In the subsequent transfer process, the etching surface between the micro-photodiode 1 and the substrate 10 can be reduced, the damage to the light-emitting area of ​​the epitaxial structure 20 during the transfer process can be reduced, the light extraction efficiency can be increased, and the light output brightness of the micro-photodiode 1 can be improved.

[0040] The micro LED 1 has a chip with at least one side having a size of 50 micrometers or less. The micro LED 1 can be a Mini LED or a Micro LED. Figure 2 In the epitaxial structure 20, the side length of the first surface 21 is less than or equal to 50 micrometers. The chip size of the micro-LED 1 can be 50 micrometers × N micrometers, where N is 50-300. For example, the chip size of the micro-LED 1 is 50 micrometers × 50 micrometers or 50 micrometers × 200 micrometers.

[0041] One embodiment of the present invention provides a method for fabricating a miniature light-emitting diode 1, which can be used to manufacture a miniature light-emitting diode 1 having the structure described above. Figure 5 This is a schematic diagram of the fabrication method of a preferred embodiment of the miniature light-emitting diode 1 in this invention. However, the fabrication method and process of the miniature light-emitting diode 1 in this invention are not limited to... Figure 5 As shown.

[0042] Combination Figure 2 and Figure 5 See Figures 6 to 10 , Figures 6 to 10 This is a schematic diagram illustrating a preferred embodiment of the fabrication method of the miniature light-emitting diode 1 in this invention. The method employs, as follows: Figure 5 The method for fabricating the miniature light-emitting diode 1 shown is as follows: Figure 2 The fabrication process of the micro LED 1 shown is described below.

[0043] The fabrication method of the miniature light-emitting diode 1 may include at least the following steps: transfer and roughening of the wafer-like epitaxial structure 20', segmentation of the wafer-like epitaxial structure, sidewall etching of the epitaxial structure, and transfer of the epitaxial structure. The specific implementation process of each step is described below.

[0044] Step S11: Transfer and coarsening of the lamellar epitaxial structure See Figure 6 A sheet-like epitaxial structure 20' is grown on a growth substrate 00. The growth substrate 00 is located below the sheet-like epitaxial structure 20', and a connecting electrode 30 is provided above the sheet-like epitaxial structure 20'. Figure 6 See 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.

[0045] 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.

[0046] Step S12: Segmentation of the sheet-like epitaxial structure 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 it 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.

[0047] Step S13: Etching of the sidewalls of the epitaxial structure See Figure 9After 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 a bonding layer 02, and the roughened portion 40 is located on the surface of the epitaxial structure 20 away from the transfer substrate 01. Each epitaxial structure 20 is etched to make the surface of the sidewall region of the epitaxial structure 20 away from the transfer substrate 01 curved, and the roughened portion 40 of the sidewall region of the epitaxial structure 20 is etched away. After this etching step, there is a certain gap between the bonding layer 02 and the epitaxial structure 20, which can prevent over-etching or accidental etching of the epitaxial structure 20 during subsequent transfer or removal from the transfer substrate 01. Figure 9 As shown, the sidewall region of the epitaxial structure 20 is a convex arc-shaped surface that extends from the transfer substrate 01 side toward the roughened portion 40 side.

[0048] Step S14: Transfer of epitaxial structure See Figure 10 A bonding layer or colloid 50 is provided above the roughened portion 40 in the epitaxial structure 20. The epitaxial structure 20 is bonded or connected to the substrate 10 through the roughened portion 40 and the bonding layer or colloid 50, thereby removing the transfer substrate 01 and the bonding layer 02, and thus fabricating a plurality of micro light-emitting diodes 1 arranged in an array on the substrate 10. The connecting electrode 30 is located on the surface of the micro light-emitting diode 1 away from the substrate 10.

[0049] Figure 11 This is a schematic diagram of a transfer method for a miniature light-emitting diode according to an embodiment of the present invention. To achieve at least one or more of the aforementioned advantages, an embodiment of the present invention provides a transfer method for a miniature light-emitting diode, which can transfer... Figure 2 The miniature LED 1 shown is transferred or mass-transferred. Please refer to... Figure 2 , Figure 10 See Figure 11 In this embodiment, laser transfer technology is used to perform mass transfer of the miniature light-emitting diode 1.

[0050] like Figure 11 As shown, a plurality of miniature light-emitting diodes 1 are arranged in an array on the substrate 10. The miniature light-emitting diodes 1 can be connected to the substrate 10 by means of colloid 40 or bonding. Figure 11 In the micro-LED 1, the epitaxial structure 20 is connected and bonded to the substrate 10 via the roughened portion 40 and the colloid 50. The substrate 10 can be an adapter substrate, a transfer substrate, etc. The laser source 60 is located below the substrate 10. Figure 11 In this configuration, the laser source 60 is located on the side of the substrate 10 away from the micro-light-emitting diode 1, and facing the surface of the epitaxial structure 20 with the roughened portion 40. When the laser source 60 is activated, the laser emitted by the laser source 60 (… Figure 10(As indicated by the middle arrow) At least the area on the substrate 10 where the colloid 50 is provided is irradiated. When the laser is irradiated, the heat generated causes the colloid 50 to melt, thereby causing the micro light-emitting diode 1 to peel off from the substrate 10, so as to transfer the micro light-emitting diode 1 to the driving substrate (not shown in the figure) or the circuit board.

[0051] Combination Figure 1 See Figure 11 . Figure 1 The spacing between the micro-light-emitting diodes 3 arrayed on the existing substrate 2 is less than 10 micrometers. 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 diodes 3. Figure 11 In the example, on the substrate 10, the spacing H2 between two adjacent micro-LEDs 1 is 2 micrometers to 5 micrometers. This can be understood as the numerous micro-LEDs 1 arrayed on the substrate 10 being densely packed with very small spacing between adjacent ones. In this case, if like... Figure 1 Similarly, the laser emitted by the laser source 60 still irradiates the entire surface of the epitaxial structure 20 facing the substrate 10, which can easily cause adjacent micro-light-emitting diodes 1 that do not need to be transferred to separate from the substrate 10, resulting in mis-transfer or affecting the connection stability with the substrate 10.

[0052] Figure 11 In the example, within the projection plane of the substrate 10, the irradiation area S2 of the laser emitted by the laser source 60 is smaller than the projection area of ​​the micro-LED 1. The roughened portion 40 provided on the second portion 22b of the second surface 22 of the epitaxial structure 20 in the micro-LED 1 serves as a contact surface, connecting and adhering to the substrate 10. When the laser emitted by the laser source 60 irradiates the substrate 10 and the epitaxial structure 20, it primarily irradiates the connection area between the roughened portion 40 of the epitaxial structure 20 and the substrate 10. Within the projection plane of the substrate 10, the projected area of ​​the contact surface between the epitaxial structure 20 and the substrate 10 irradiated by the laser is smaller than the projected area of ​​the epitaxial structure 20. Figure 11 The irradiation area S2 of the laser is less than Figure 1 The irradiation area S1 of the laser. Additionally... Figure 11 In the example, the laser emitted by the laser source 60 will not illuminate the sidewall region of the epitaxial structure 20 or the gap region between two adjacent micro-light-emitting diodes 1, resulting in mis-displacement of the micro-light-emitting diodes 1 or poor contact between the micro-light-emitting diodes 1 and the substrate 10.

[0053] The present invention provides a miniature light-emitting diode 1 (such as...) Figure 2As shown in the figure, compared with existing micro-light-emitting diodes, the sidewall region of the epitaxial structure 20 is not set with a conventional vertical structure with a regular shape, but with a curved or arc-shaped structure, which can increase the light extraction efficiency and improve the luminous brightness of the sidewall region of the epitaxial structure. 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 micro-light-emitting diode 1 is transferred using laser transfer technology, the irradiation area of ​​the laser on the micro-light-emitting diode 1 (or the laser spot projection area) is reduced. This can both peel off and transfer the micro-light-emitting diode 1 that needs to be transferred, and prevent the micro-light-emitting diode 1 that does not need to be transferred from being mistakenly transferred or having poor contact with the substrate 10 due to an excessively large irradiation area of ​​the laser. The micro-light-emitting diode 1 provided by the present invention (as shown in the figure) Figure 2 As shown, it can have a higher overall light output rate and achieve high brightness emission; in addition, when the spacing of the micro light-emitting diode 1 array is small, the micro light-emitting diode 1 that needs to be transferred can be precisely aligned, stripped and transferred in the laser transfer process, thereby improving the transfer yield and efficiency of the mass transfer of micro light-emitting diode 1.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A miniature light-emitting diode, characterized in that: At least including: The epitaxial structure has a first surface and a second surface opposite to each other. The first surface is the surface on one side of the electrode. The longitudinal section of the second surface includes a first part, a second part and a third part. The contour lines of the first part and the third part toward the outside of the epitaxial structure are curves. The longitudinal section of the second part away from the first surface is a roughened surface. Connecting electrodes are electrically connected to the epitaxial structure; as well as The roughened portion is located on the surface of the second part of the second surface away from the first surface; the connecting electrode and the roughened portion are located on both sides of the epitaxial structure and are disposed opposite to each other; The first part and the third part of the second surface are respectively outwardly convex arcs from the first surface toward the second surface, and the lengths of the two ends of the first part and the two ends of the third part projected in the horizontal direction are less than or equal to 20 micrometers. The light-emitting surface of the second surface region includes the first part and the third part.

2. The miniature light-emitting diode according to claim 1, characterized in that: The lengths of the two ends of the first part and the two ends of the third part projected in the horizontal direction are greater than or equal to 5 micrometers.

3. The miniature light-emitting diode according to claim 1, characterized in that: The angle between the tangent at the connection point between the arcuate surface in the first part and the second part and the horizontal direction is 30° to 75°.

4. The miniature light-emitting diode according to claim 1, characterized in that: In the epitaxial structure, one end of the first part and the third part are respectively connected to the two ends of the first surface, and the other end is respectively connected to the two ends of the second part.

5. The miniature light-emitting diode according to claim 1, characterized in that: The first surface has a horizontal length of less than 50 micrometers, and the second portion of the second surface has a horizontal length of less than 20 micrometers.

6. The miniature light-emitting diode according to claim 1, characterized in that: The distance between the upper surface of the connecting electrode and the second portion of the second surface is 10 micrometers to 12 micrometers.

7. The miniature light-emitting diode according to claim 1, characterized in that: The size of at least one side of the chip of the micro light-emitting diode is less than or equal to 50 micrometers.

8. The miniature light-emitting diode according to claim 1, characterized in that: The first surface is provided with at least two connecting electrodes, and along the projection direction toward the second surface, the projection surfaces of the two connecting electrodes are mainly located in the regions where the first part and the third part of the second surface are located, respectively.

9. The miniature light-emitting diode according to claim 8, characterized in that: Along the projection direction toward the second surface, the projection surfaces of the two connecting electrodes on opposite sides respectively coincide with the projection surface portion of the side of the second surface where the second part is connected to the first part and the third part.

10. The miniature light-emitting diode according to any one of claims 1 to 9, characterized in that: The micro light-emitting diode also includes a substrate, which is connected to the roughened portion via a colloid.

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