Micro-LED structure with improved light extraction efficiency and manufacturing method thereof

Abstract

The present invention discloses a Micro-LED structure for improving light extraction efficiency and a manufacturing method thereof, wherein the structure comprises: a driving backplane; a dielectric layer and an electrode connection PAD located on the driving backplane, a plurality of first high-reflectivity anode metals located on the dielectric layer; a second high-reflectivity anode metal located on the electrode connection PAD; the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal; an LED tube core located on the second high-reflectivity anode metal; a passivation layer located on both sides of the LED tube core, on both sides of the second high-reflectivity anode metal, and on the dielectric layer; a reflection ring filling substrate located on the first high-reflectivity anode metal; a reflection ring surface coating located on the cathode electrode at the reflection ring filling substrate; a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the reflection ring surface coating, thereby ultimately achieving improved light extraction efficiency and reduced light crosstalk between pixels.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device manufacturing, and in particular to a Micro-LED structure for improving light extraction efficiency and a manufacturing method thereof. Background Art

[0002] Micro-LED technology based on semiconductor materials is a new type of display technology with the characteristics of high resolution, high brightness, wide color gamut, low power consumption, and high reliability. Compared with LCD and OLED, its brightness, resolution, energy consumption, response speed, thermal stability and other indicators are more advantageous. It is considered to be the next generation of display technology and can be widely used in the metaverse, mobile terminals, and even change the form of electronic consumption. Nitride semiconductors represented by GaN have the advantages of wide adjustable band gap, stable chemical properties, high electron saturation drift velocity and high luminous efficiency, making them the preferred semiconductor materials for Micro-LED devices.

[0003] However, at this stage, the actual luminous efficiency of Micro-LED is far lower than theoretical expectations. On the one hand, it comes from epitaxial defects and electron leakage; on the other hand, since the light of Micro-LED is generated by self-emission, it is not directional. Considering that the light emission of InGaN / GaN quantum wells is caused by the recombination of electrons in the conduction band and holes in the heavy hole band, the light emission mode is TE mode. Therefore, in addition to photon emission from the light-emitting surface of the Micro-LED device, photons are also emitted from the back and sides. This leads to low light extraction efficiency of actual Micro-LED devices, and in the field of micro-display, pixels with extremely small line widths will also have optical crosstalk between pixels, resulting in reduced clarity and contrast of the display. And considering the possibility of total reflection of the light-emitting surface, the design and preparation of device structures that can improve light extraction efficiency are crucial to the development of Micro-LED technology.

[0004] At present, the mainstream solutions to this problem in the industry, such as patterned substrates, DBR reflectors, roughening, aluminum rings, etc., are mostly for flip-chip large-size pixel devices. For near-eye display applications, the pixel pitch of Micro-LED chips should be less than 10μm. At the same time, based on the requirements of production capacity and cost in mass production, vertically structured Micro-LED chips with wafer bonding have excellent prospects. However, there are few reports on solving the problem of improving the light extraction efficiency of Micro-LEDs with tiny pixels under this technical route. Summary of the invention

[0005] Technical purpose: In view of the defects in the prior art, the present invention discloses a Micro-LED structure with improved light extraction efficiency and a manufacturing method thereof, so as to improve the light extraction efficiency and reduce the light crosstalk between pixels.

[0006] Technical solution: In order to achieve the above technical objectives, the present invention adopts the following technical solution.

[0007] A Micro-LED structure for improving light extraction efficiency, comprising:

[0008] Driving backplane; define the plane where the driving backplane is located as the XY plane, the length direction of the device is the X direction, and the Z direction is perpendicular to the XY plane;

[0009] The dielectric layer and the electrode connection PAD located on the driving backplane are arranged at intervals; on the XY plane, there are several electrode connection PADs, which are not connected;

[0010] A plurality of first high reflectivity anode metals located on the dielectric layer; a second high reflectivity anode metal located on the electrode connection PAD; the first high reflectivity anode metals are not in contact with the second high reflectivity anode metals;

[0011] The LED die is located on the anode metal with the second highest reflectivity; the electrode connection PAD corresponds to the LED die one by one, the LED die is in a truncated cone shape on the XZ plane, and in a circular shape on the XY plane; the top of the LED die is a GaN microlens array;

[0012] A passivation layer located on both sides of the LED die, on both sides of the second highest reflectivity anode metal, and on top of the dielectric layer;

[0013] A reflection ring filling substrate located on the first high reflectivity anode metal; in the XZ plane, the reflection ring filling substrate is in a positive trapezoidal shape;

[0014] A cathode electrode is located on both sides and above the reflection ring filling substrate, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and above the passivation layer, and on the top of the LED die; the cathode electrode is in contact with the reflection ring surface coating and the first high reflectivity anode metal, and is not in contact with the second high reflectivity anode metal;

[0015] a reflective ring surface coating on the cathode electrode at the reflective ring filling substrate;

[0016] A protective dielectric layer and a dielectric microlens are located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflective ring. The protective dielectric layer and the dielectric microlens, the LED die, the GaN microlens array, and the electrode connection PAD center are collinear.

[0017] A method for manufacturing a Micro-LED structure with improved light extraction efficiency, used to manufacture the above-mentioned Micro-LED structure with improved light extraction efficiency, comprises the following steps:

[0018] S1. Electrodes are formed on the surface of the driving backplane to connect the PAD and the dielectric layer. The upper surface of the PAD and the dielectric layer are bonded to the GaN-based Micro-LED epitaxial wafer through a highly reflective anode metal;

[0019] S2, etching the GaN-based Micro-LED epitaxial wafer, removing the substrate in the GaN-based Micro-LED epitaxial wafer and forming a GaN microlens array, wherein the center of the GaN microlens array coincides with the center of the electrode connection PAD;

[0020] S3, etching the GaN-based Micro-LED epitaxial wafer, forming LED tube cores corresponding to the electrode connection PADs one by one and a reflection ring filling substrate located between the LED tube cores on the XZ plane, wherein the LED tube cores are not in contact with the reflection ring filling substrate, the LED tube core is in a truncated cone shape, the GaN microlens array is located on the top of the LED tube core, and the reflection ring filling substrate is in a regular trapezoidal shape; etching the high-reflectivity anode metal, forming a second high-reflectivity anode metal located under the LED tube core and a first high-reflectivity anode metal located under the reflection ring filling substrate on the XZ plane; wherein the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal;

[0021] S4, generating a passivation layer located on both sides of the LED tube core, on both sides of the second high reflectivity anode metal, and on the dielectric layer, generating a cathode electrode located on both sides and on the reflection ring filling base, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and on the passivation layer, and on the top of the LED tube core, and generating a reflection ring surface coating located on the cathode electrode at the reflection ring filling base;

[0022] S5. Generate a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflection ring.

[0023] A method for manufacturing a Micro-LED structure with improved light extraction efficiency, used to manufacture the above-mentioned Micro-LED structure with improved light extraction efficiency, comprises the following steps:

[0024] S1. Electrodes are formed on the surface of the driving backplane to connect the PAD and the dielectric layer. The upper surface of the PAD and the dielectric layer are bonded to the GaN-based Micro-LED epitaxial wafer through a highly reflective anode metal;

[0025] S2, etching the GaN-based Micro-LED epitaxial wafer, removing the substrate in the GaN-based Micro-LED epitaxial wafer and forming a GaN microlens array, wherein the center of the GaN microlens array coincides with the center of the electrode connection PAD;

[0026] S3, etching the GaN-based Micro-LED epitaxial wafer, forming LED tube cores corresponding to the electrode connection PADs on the XZ plane, the LED tube cores are truncated, and the GaN microlens array is located on the top of the LED tube core, etching the high-reflectivity anode metal, forming a first high-reflectivity anode metal and a second high-reflectivity anode metal under the LED tube core on the XZ plane; wherein the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal; using PECVD and photolithography processes to etch to form a reflection ring filling substrate located between the LED tube cores; the first high-reflectivity anode metal is located under the reflection ring filling substrate; the reflection ring filling substrate is made of insulating material;

[0027] S4, generating a passivation layer located on both sides of the LED tube core, on both sides of the second high reflectivity anode metal, and on the dielectric layer, generating a cathode electrode located on both sides and on the reflection ring filling base, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and on the passivation layer, and on the top of the LED tube core, and generating a reflection ring surface coating located on the cathode electrode at the reflection ring filling base;

[0028] S5. Generate a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflection ring.

[0029] A method for manufacturing a Micro-LED structure with improved light extraction efficiency, used to manufacture the above-mentioned Micro-LED structure with improved light extraction efficiency, comprises the following steps:

[0030] S1. Forming electrodes on the surface of the driving backplane to connect the PAD and the dielectric layer, and bonding the PAD and the upper surface of the dielectric layer to the GaN-based Micro-LED epitaxial wafer by bonding a highly reflective anode metal;

[0031] S2, etching the GaN-based Micro-LED epitaxial wafer, removing the substrate in the GaN-based Micro-LED epitaxial wafer and forming a GaN microlens array, wherein the center of the GaN microlens array coincides with the center of the electrode connection PAD;

[0032] S3, etching the GaN-based Micro-LED epitaxial wafer to form an LED die corresponding to the electrode connection PAD on the XZ plane, the LED die is in a truncated cone shape, the GaN microlens array is located on the top of the LED die, and etching the high-reflectivity anode metal to form a first high-reflectivity anode metal and a second high-reflectivity anode metal located under the LED die on the XZ plane; wherein the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal;

[0033] S4, generating a passivation layer located on both sides of the LED tube core, on both sides of the second high reflectivity anode metal, and on the dielectric layer, generating a reflection ring filling substrate located between the LED tube cores through evaporation and stripping processes, and the first high reflectivity anode metal is located under the reflection ring filling substrate; the reflection ring filling substrate is made of metal; generating cathode electrodes located on both sides and on the reflection ring filling substrate, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and on the passivation layer, and on the top of the LED tube core, and generating a reflection ring surface coating on the cathode electrode at the reflection ring filling substrate;

[0034] S5. Generate a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflection ring.

[0035] Beneficial effects:

[0036] (1) The device structure for improving the light extraction efficiency of the Micro-LED chip described in the present invention can be achieved by using conventional semiconductor material preparation processes, which are simple and easy to implement;

[0037] (2) The device structure for improving the light extraction efficiency of the Micro-LED chip in the present invention can directly improve the light extraction efficiency of the Micro-LED chip, thereby improving the external quantum efficiency and electro-optical conversion efficiency of the display screen;

[0038] (3) The introduction of the reflective ring and the microlens in the device structure for improving the light extraction efficiency of the Micro-LED chip in the present invention can improve the excessive scattering angle of the pixel's self-luminescence, reduce the light crosstalk between pixels, and utilize the originally wasted TE mode side light emitting portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of Micro-LED structure to improve light extraction efficiency;

[0040] Figure 2 Schematic diagram of the GaN-based Micro-LED epitaxial wafer and driver backplane structure before bonding;

[0041] Figure 3 Schematic diagram of bonding sheet structure;

[0042] Figure 4 Schematic diagram of removing the substrate on one side of the epitaxial wafer and etching to the N-type GaN area for the bonding wafer;

[0043] Figure 5 Schematic diagram of GaN self-etched microlens;

[0044] Figure 6 A schematic diagram of the structure of the Micro-LED die and the reflective ring filling substrate;

[0045] Figure 7for Figure 6 XY plane diagram of the structure shown;

[0046] Figure 8 This is a schematic diagram of the structure after the passivation layer and cathode electrode are prepared;

[0047] Fig. 9 This is a schematic diagram of the structure after the surface coating of the reflection ring is prepared;

[0048] Fig.10 This is a schematic diagram of the structure after the preparation of the protective dielectric layer and dielectric microlens;

[0049] Fig.11 This is a schematic diagram of the simulation structure of light intensity distribution without enhancement structure;

[0050] Fig.12 This is a schematic diagram of the simulation structure of the light intensity distribution of a single lens structure;

[0051] Fig.13 This is a schematic diagram of the simulation structure of the light intensity distribution of the multi-lens structure;

[0052] Fig.14 This is a schematic diagram of the simulation structure of the light intensity distribution of the reflection ring structure;

[0053] Fig.15 The simulation results of light output angle distribution under four conditions are shown in the figure;

[0054] Among them, 101 is a driving backplane, 102 is a dielectric layer, 103 is an electrode connection PAD, 20 is a high-reflectivity anode metal, 201 is a first high-reflectivity anode metal, 202 is a second high-reflectivity anode metal, 30 is a GaN-based Micro-LED epitaxial wafer, 301 is an LED die, 302 is a cathode electrode, 303 is a passivation layer, 304 is a GaN microlens array, 401 is a reflective ring filling substrate, 402 is a reflective ring surface coating, and 501 is a protective dielectric layer and a dielectric microlens. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0056] The existing Micro-LED device structure may result in a large divergence angle, low light extraction efficiency, light crosstalk, etc. In order to solve these problems, the embodiments of the present invention are further explained and illustrated in conjunction with the accompanying drawings.

[0057] Embodiment 1:

[0058] As attached Figure 1 As shown, a Micro-LED structure for improving light extraction efficiency in this embodiment includes:

[0059] The driving backplane 101 is a Si-based CMOS driving circuit; the plane where the driving backplane 101 is located is defined as the XY plane, the device length direction is the X direction, and the Z direction is perpendicular to the XY plane;

[0060] The dielectric layer 102 and the electrode connection PAD 103 are located on the driving backplane 101. The dielectric layer 102 and the electrode connection PAD 103 are arranged at intervals and have the same thickness. The dielectric layer 102 is in contact with the electrode connection PAD 103 and the dielectric layer 102 is located on both sides of the electrode connection PAD 103. On the XY plane, there are several electrode connection PADs 103 that are not connected. The material of the electrode connection PAD 103 includes: metals such as Au and Cu, and the dielectric layer is an insulating medium such as silicon oxide.

[0061] A plurality of first high-reflectivity anode metals 201 located on the dielectric layer 102 , wherein the width of the first high-reflectivity anode metals 201 is smaller than the width of the dielectric layer 102 ;

[0062] A second high reflectivity anode metal 202 located on the electrode connection PAD103, wherein the second high reflectivity anode metal 202 completely covers the electrode connection PAD103; the first high reflectivity anode metal 201 is not in contact with the second high reflectivity anode metal 202;

[0063] The LED die 301 is located on the second high reflectivity anode metal 202, and the pixel line width of the LED die 301 is ≤10μm. In this embodiment, the line width ranges from 0.3μm to 10μm. The electrode connection PAD103 corresponds to the LED die 301 one by one. The LED die 301 is truncated cone-shaped on the XZ plane and circular on the XY plane. The top of the LED die 301 is a GaN microlens array 304.

[0064] The passivation layer 303 located on both sides of the LED core 301, both sides of the second high reflectivity anode metal 202, and on the dielectric layer 102 is used to protect the side wall of the LED core, isolate the positive and negative electrodes, and achieve a good insulation effect.

[0065] A reflection ring filling substrate 401 is located on the first high reflectivity anode metal 201; the angle between the reflection ring filling substrate 401 and the dielectric layer 102 is between 60° and 85°; on the XZ plane, the reflection ring filling substrate 401 is a regular trapezoid;

[0066] The cathode electrode 302 is located on both sides and above the reflection ring filling substrate 401, on both sides of the first high reflectivity anode metal 201, on the dielectric layer 102, on both sides and above the passivation layer 303, and on the top of the LED tube core 301; the cathode electrode 302 is in contact with the reflection ring surface coating 402 and the first high reflectivity anode metal 201 to achieve the current expansion effect between LED pixels, but is not in contact with the second high reflectivity anode metal 202 and achieves good electrical isolation;

[0067] A reflection ring surface coating 402 is located on the cathode electrode 302 at the reflection ring filling substrate 401, and the reflection ring surface coating 402 is only located at the protrusion of the reflection ring filling substrate 401; the reflection ring filling substrate 401 and the reflection ring surface coating 402 constitute a whispering gallery-shaped reflection ring, and the reflection ring filling substrate 401 can be formed by self-etching of a GaN-based epitaxial wafer, an insulating medium, or growth of the same material as the reflection ring surface coating; the reflection ring surface coating 402 materials include Pt, Ag, Rh, and Al.

[0068] Among them, the LED core 301 is made of a GaN-based Micro-LED epitaxial wafer with a light-emitting quantum well. The light-emitting quantum well is an InGaN-based light-emitting quantum well, the In component is between 0.1 and 0.5, and the light emission includes red, green and blue light.

[0069] The LED die 301 is in contact with the second high reflectivity anode metal 202. In the LED die 301, the P-type GaN region forms an ohmic contact with the upper surface of the second high reflectivity anode metal 202. The GaN microlens itself is formed by etching above the N-type GaN region, that is, the GaN microlens array 304 is formed on the top of the LED die 301; the surface of the GaN microlens array 304 is roughened to improve the light transmittance. The material of the N-type GaN region is Si-doped GaN, and the doping concentration is ≥1×10 18 cm -3 , thickness ≥ 800 nm. The P-type GaN region material is hole-conducting Mg-doped GaN, with a doping concentration ≥ 1×10 19 cm -3 , thickness ≥ 200 nm. The ratio of the lens curvature radius of the GaN microlens array 304 to the pixel line width in the LED die 301 is in the range of 0.5 to 2.

[0070] The LED tube core 301 forms an ohmic contact with the cathode electrode 302, and the material of the cathode electrode 302 is ITO;

[0071] In some embodiments, the reflection ring filling substrate 401 and the LED die 301 are formed by etching the GaN-based semiconductor of the same epitaxial wafer;

[0072] The protective dielectric layer and dielectric microlens 501 are located on the dielectric layer 102, on the cathode electrode 302, and on the reflective ring surface coating 402; the materials of the passivation layer 303, the protective dielectric layer and the dielectric microlens 501 are one or more combinations of silicon oxide, silicon oxynitride, silicon nitride, and aluminum oxide, and the refractive index is between 1.4 and 2.5. The protective dielectric layer and dielectric microlens 501 are located at the top of the Micro-LED structure, and the protective dielectric layer and dielectric microlens 501 are convex structures at the corresponding position of the LED tube core 301, which play the role of passivation protection and alignment and focusing. The protective dielectric layer and dielectric microlens 501, the GaN microlens array 304, the LED tube core 301, and the electrode connection PAD103 are collinear in the center.

[0073] The ratio of the lens curvature radius of the protective dielectric layer and the dielectric microlens 501 to the pixel line width in the LED die 301 is in the range of 0.5-3.

[0074] The first high reflectivity anode metal 201 and the second high reflectivity anode metal 202 have the same metal film structure and are formed by etching isolation; the first high reflectivity anode metal 201 and the second high reflectivity anode metal 202 have a surface reflectivity higher than 80%, and a contact resistivity with the P-type GaN region lower than 0.01 The first high reflectivity anode metal 201 and the second high reflectivity anode metal 202 both include an anode ohmic contact film layer, a reflective film layer and a bonding metal film layer arranged from top to bottom, and the anode ohmic contact film layer is one or more combinations of materials such as Ni, ITO, Au, and Ti;

[0075] In the second high reflectivity anode metal 202, the upper surface of the anode ohmic contact film layer contacts the lower surface of the LED tube core 301, specifically, forms an ohmic contact with the P-type GaN region; the upper surface of the reflective film layer contacts the lower surface of the anode ohmic contact film layer, and the reflective film layer material is a high reflectivity metal, such as: Pt, Ag, Rh, Al. The lower surface of the reflective film layer contacts the upper surface of the bonding metal film layer, and the lower surface of the bonding metal film layer contacts the dielectric layer 102 and the electrode connection PAD103.

[0076] In the first high reflectivity anode metal 201, the upper surface of the anode ohmic contact film layer contacts the lower surface of the reflection ring filling substrate 401, the upper surface of the reflection film layer contacts the lower surface of the anode ohmic contact film layer, the lower surface of the reflection film layer contacts the upper surface of the bonding metal film layer, and the lower surface of the bonding metal film layer contacts the dielectric layer 102.

[0077] At the top of the LED die 301, the GaN microlens array 304 serves as the first lens, and the upper surface of the LED die 301, the protective dielectric layer and the dielectric microlens 501 serve as the second lens; the GaN microlens array 304 is concentric with the protective dielectric layer and the dielectric microlens 501, and the spacing between the highest point of the protective dielectric layer and the dielectric microlens 501 and the highest point of the GaN microlens array 304 ranges from 1 μm to 4 μm; the first lens and the second lens are combined to form a double lens structure in this embodiment.

[0078] The upper surface of the whispering gallery-shaped reflection ring formed by the reflection ring filling substrate 401 and the reflection ring surface coating 402 is slightly higher than the upper surface of the LED tube core 301, so that the side light can be better collected.

[0079] In the present invention, each LED die is driven individually by the electrode connection PAD103 on the driving backplane, and the upper surface of the LED die is roughened and self-etched to form a GaN microlens array 304; the high reflectivity anode metal structure mainly refers to the second high reflectivity anode metal 202, and can also be a combination of the first high reflectivity anode metal 201 and the second high reflectivity anode metal 202; the double lens structure refers to the GaN microlens array 304 and the protective dielectric layer and the dielectric microlens 501. The three optimized structures of high reflectivity anode metal structure, whispering gallery-shaped reflection ring, and double lens structure can all achieve high light output efficiency of Micro-LED, and the superposition of the three structures is the best choice. The high reflectivity anode metal structure can utilize the light wasted on the back; the whispering gallery-shaped reflection ring can collect the side light of the TE mode in GaN, and the whispering gallery formed by self-etching has stable properties and simple process; the double lens structure can more effectively collect the light from the main viewing angle. The Micro-LED structure formed by the three structures can improve the collimation and light output efficiency of the light output; and reduce the scattering and crosstalk of light.

[0080] A method for manufacturing a Micro-LED structure with improved light extraction efficiency in this embodiment is used to manufacture the Micro-LED structure with improved light extraction efficiency described above, comprising the following steps:

[0081] S1, forming an electrode connecting PAD103 and dielectric layer 102 on the surface of driving backplane 101, and bonding the electrode connecting PAD103 and the upper surface of dielectric layer 102 with GaN-based Micro-LED epitaxial wafer 30 through high-reflective anode metal 20; Figure 2As shown, an electrode connection PAD103 and a dielectric layer 102 are formed on the surface of the driving backplane 101. The dielectric layer 102 and the electrode connection PAD103 are arranged at intervals, and the two have the same thickness; a bonding metal film layer is formed on the surface of the electrode connection PAD103 and the dielectric layer 102; and an anode ohmic contact film layer and a reflective film layer are formed on the surface of the GaN-based Micro-LED epitaxial wafer 30. The GaN-based Micro-LED epitaxial wafer 30 and the driving backplane 101 are bonded in a high temperature and high pressure environment, with a bonding temperature of 150 to 450°C and a time of about 1 hour. After bonding, a bonding sheet with a composite structure of the GaN-based Micro-LED epitaxial wafer 30, a highly reflective anode metal 20, and a driving backplane 101 arranged in sequence from top to bottom is formed, as shown Figure 3 As shown;

[0082] S2, etching the GaN-based Micro-LED epitaxial wafer 30, removing the substrate in the GaN-based Micro-LED epitaxial wafer 30 and forming a GaN microlens array 304, wherein the center of the GaN microlens array 304 coincides with the center of the electrode connection PAD; Figure 4 and Figure 5 As shown, the GaN-based Micro-LED epitaxial wafer 30 is composed of a P-type GaN region, an InGaN-based light-emitting quantum well, and an N-type GaN region in the direction from the driving backplane 101 to the driving backplane 101. The substrate on one side of the bonding wafer epitaxial wafer, that is, the substrate on the surface of the S1 device, is removed and etched to the N-type GaN region of the epitaxial wafer. Figure 5 As shown, a GaN microlens array 304 is formed on one side of the GaN-based Micro-LED epitaxial wafer 30, and the center of the GaN microlens array coincides with the center of the electrode connection PAD material; after etching, the edge of the GaN microlens array 304 is still N-type GaN, and the thickness from the InGaN-based light-emitting quantum well is ≥200nm.

[0083] S3, such as Figure 6As shown, the plane where the driving backplane 101 is located is defined as the XY plane, the device length direction is the X direction, and the Z direction is perpendicular to the XY plane; the GaN-based Micro-LED epitaxial wafer 30 is etched to form LED tube cores 301 corresponding to the electrode connection PAD103 on the XZ plane and a reflection ring filling substrate 401 located between the LED tube cores 301, wherein the LED tube core 301 is not in contact with the reflection ring filling substrate 401, the LED tube core 301 is in a truncated cone shape, the GaN microlens array 304 is located on the top of the LED tube core 301, the GaN microlens array 304, the LED tube core 301, and the electrode connection PAD103 are collinear in the center, the reflection ring filling substrate 401 is in a positive trapezoidal shape, and the electrode connection PAD103 is used to provide a metal conductive channel for the LED tube core 301. The shape is not limited and can be circular, triangular or other shapes. Adjacent electrodes are connected to PAD103 and are not connected. The high-reflectivity anode metal 20 is etched to form a second high-reflectivity anode metal 202 located under the LED tube core 301 and a first high-reflectivity anode metal 201 located under the reflection ring filling substrate 401 on the XZ plane. The first high-reflectivity anode metal 201 is not in contact with the second high-reflectivity anode metal 202, and the width of the first high-reflectivity anode metal 201 is equal to the bottom width of the LED tube core 301, and the width of the second high-reflectivity anode metal 202 is equal to the bottom width of the reflection ring filling substrate 401.

[0084] like Figure 7 As shown, on the XY plane, the LED die 301 is circular, and the bottom of the LED die 301 is the second high reflectivity anode metal 202 ( Figure 7 The outer periphery of each LED tube core 301 is the first part of the dielectric layer 102, the first part of the dielectric layer 102 is in a circular ring shape, and the first parts of adjacent dielectric layers 102 are not connected; the outer periphery of the first part of the dielectric layer 102 is a reflective ring filling substrate 401, and the reflective ring filling substrate 401 is a connected ring structure; the bottom of the reflective ring filling substrate 401 is a first high reflectivity anode metal 201 ( Figure 7 (not shown); the reflective ring fills the second part of the dielectric layer 102 at the periphery of the substrate 401;

[0085] like Figure 6As shown, ICP is used to etch the GaN-based Micro-LED epitaxial wafer 30 and the high-reflectivity anode metal 20 to form an LED die 301 corresponding to the electrode connection PAD one by one, and the LED die is a Micro-LED die; wherein in the XZ plane, the second high-reflectivity anode metal 202 on the lower surface of the LED die contacts the electrode connection PAD, and a reflective ring filling substrate is formed by ICP etching. The reflective ring filling substrate is made of the same material as the LED die and is also formed by etching the GaN-based Micro-LED epitaxial wafer. The reflective ring filling substrate is located above the dielectric layer and is a positive trapezoid. The slope formed with the lower bottom surface ranges from 60° to 85°, which is approximately 75° in this embodiment, and is electrically isolated from the driving backplane 101 to avoid short circuit.

[0086] S4, generating a passivation layer 303 located on both sides of the LED tube core 301, on both sides of the second high reflectivity anode metal 202, and on the dielectric layer 102, generating a cathode electrode 302 located on both sides and on the reflection ring filling substrate 401, on both sides of the first high reflectivity anode metal 201, on the dielectric layer 102, on both sides and on the passivation layer 303, and on the top of the LED tube core 301, and generating a reflection ring surface coating 402 located on the cathode electrode 302 at the reflection ring filling substrate 401; Figure 8 and Fig. 9 As shown, the entire surface of the device structure formed on S3 by plasma enhanced chemical vapor deposition (PECVD) is covered with a passivation layer 303 of SiO2 of 300 ~ 700 nm; a hole is opened in SiO2 on the upper surface of the LED core 301 and an ITO cathode electrode 302 is formed; a high-reflectivity metal Ag is evaporated on the surface of the reflection ring filling substrate to form a reflection ring surface coating 402; in order to ensure no leakage, the passivation layer located on both sides of the LED core 301 needs to ensure that: the passivation layer fully covers the side wall of the P-type GaN region and the side wall of the InGaN-based light-emitting quantum well.

[0087] S5, generating a protective dielectric layer and a dielectric microlens 501 located on the dielectric layer 102, on the cathode electrode 302, and on the reflective ring surface coating 402; Fig.10 As shown, the entire surface of the device structure formed in S4 is again covered with a SiO2 dielectric layer with a thickness of 1 to 4 μm, and a protective dielectric layer and a dielectric microlens 501 are formed on the upper surface of the pixel area. The protective dielectric layer and the dielectric microlens 501 are consistent with the center of the GaN microlens array 304 on the surface of the LED core.

[0088] The dielectric layer and passivation layer on the driving backplane need to meet good electrical isolation properties, and the maximum leakage current should not exceed the nA level within the operating voltage of the Micro-LED structure.

[0089] Embodiment 2:

[0090] The manufacturing method of a Micro-LED structure for improving light extraction efficiency in this embodiment is different from that in Embodiment 1 in that:

[0091] S3, etching the GaN-based Micro-LED epitaxial wafer 30 to form LED tube cores 301 corresponding to the electrode connection PAD103 on the XZ plane; etching the high-reflectivity anode metal 20 to form a first high-reflectivity anode metal 201 and a second high-reflectivity anode metal 202 located under the LED tube core 301 on the XZ plane; the first high-reflectivity anode metal 201 is not in contact with the second high-reflectivity anode metal 202; using PECVD to grow insulating media such as silicon oxide, silicon nitride, and silicon oxynitride, combined with a photolithography process to etch to form a reflective ring filling substrate 401 located between the LED tube cores 301; the first high-reflectivity anode metal 201 is located under the reflective ring filling substrate 401.

[0092] That is to say, the material of the reflective ring filling substrate 401 in this embodiment is different from that of the LED core 301 and is an insulating material. The material of the reflective ring filling substrate 401 in Example 1 is the same as that of the LED core 301 .

[0093] With respect to the process flow of the reflective ring filling substrate generated by PECVD in Example 2, when etching the high-reflective anode metal 20, only the second high-reflectivity anode metal 202 may be retained, and the first high-reflectivity anode metal may be removed at the same time, thereby simplifying the process steps; at this time, the reflective ring filling substrate is located on the dielectric layer 102.

[0094] Embodiment 3:

[0095] The manufacturing method of a Micro-LED structure for improving light extraction efficiency in this embodiment is different from that in Embodiment 1 in that:

[0096] S3, etching the GaN-based Micro-LED epitaxial wafer 30, forming an LED tube core 301 corresponding to the electrode connection PAD103 on the XZ plane; etching the high-reflectivity anode metal 20, forming a first high-reflectivity anode metal 201 and a second high-reflectivity anode metal 202 located under the LED tube core 301 on the XZ plane; the first high-reflectivity anode metal 201 is not in contact with the second high-reflectivity anode metal 202;

[0097] S4, generating a passivation layer 303 located on both sides of the LED tube core 301, on both sides of the second high reflectivity anode metal 202, and on the dielectric layer 102, generating a reflection ring filling substrate 401 located between the LED tube cores 301 by evaporation and stripping, and the material of the reflection ring filling substrate 401 is metal; generating a cathode electrode 302 located on both sides and on the reflection ring filling substrate 401, on both sides of the first high reflectivity anode metal 201, on the dielectric layer 102, on both sides and on the passivation layer 303, and on the top of the LED tube core 301, and generating a reflection ring surface coating 402 located on the cathode electrode 302 at the reflection ring filling substrate 401;

[0098] That is to say, the material of the reflective ring filling substrate 401 in this embodiment is different from that of the LED core 301 , that is, metal material. The material of the reflective ring filling substrate 401 in Embodiment 1 is the same as that of the LED core 301 .

[0099] With respect to the process flow of the reflective ring filling substrate generated by metal evaporation stripping in Example 3, when etching the high-reflectivity anode metal 20, only the second high-reflectivity anode metal 202 can be retained, and the first high-reflectivity anode metal can be removed at the same time, thereby simplifying the process steps; at this time, the reflective ring filling substrate is located on the dielectric layer 102.

[0100] According to the schemes of the three embodiments of the present invention, the simulation software Lumerical FDTD is used to simulate the light extraction effect of a Micro-LED structure of the present embodiment for improving light extraction efficiency, and the following four conditions are set respectively: a single Micro-LED structure without any lens and reflective ring structure (hereinafter referred to as the non-enhanced structure, also referred to as the Fig.15 ), which is a truncated cone structure with a lower bottom surface radius of 1.65 μm, an upper surface radius of 1.2 μm, and a height of 1.6 μm; a hemispherical lens structure (hereinafter referred to as a single lens structure) is added on the basis of the non-enhanced structure, the lens refractive index is 1.5, and the diameter is 2.5 μm (hereinafter referred to as a single lens); the GaN upper surface is etched into a multi-lens structure with an arc surface (hereinafter referred to as a multi-lens structure); and a reflection ring structure (hereinafter referred to as a reflection ring structure) is added on the basis of the multi-lens, the reflection ring material is Ag, the height is 1.6 μm, the distance between the lower bottom surface and the lower bottom surface of the Micro-LED unit is 0.35 μm, and the slope formed by the reflection ring and the lower bottom surface is 75°.

[0101] Fig.11 , Fig.12 , Fig.13 , Fig.14These are the simulation results of the internal light intensity distribution of the non-enhanced structure, single-lens structure, multi-lens structure, and reflective ring structure when working. By comparing the simulation results, it can be seen that after adding the lens structure, the light output of the device can be effectively converged, but some light still dissipates from the position that the side lens of the lens device cannot cover; after adding the reflective ring structure, the side light can be effectively reflected to the front light output angle, thereby playing a role in focusing and brightening.

[0102] Fig.15 The following are the simulation results of the light output viewing angle distribution under four conditions. According to the simulation results, it can be seen that the reflection ring structure has the highest light output intensity at the main viewing angle. Compared with the multi-lens structure, the addition of the reflection ring increases the brightness at the main viewing angle by about 20%.

[0103] The "first" and "second" in the names such as "first" and "second" (if any) mentioned in the embodiments of the present application are only used as name identifiers and do not represent the first or second in order.

[0104] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A Micro-LED structure for improving light extraction efficiency, characterized in that: include: Driver backplane; Define the plane where the driver backplane is located as the XY plane, the device length direction is the X direction, and the Z direction is perpendicular to the XY plane; The dielectric layer and the electrode connection PAD located on the driving backplane are arranged at intervals; on the XY plane, there are several electrode connection PADs, which are not connected; A plurality of first high reflectivity anode metals located on the dielectric layer; A second high reflectivity anode metal located on the electrode connection PAD; the first high reflectivity anode metal is not in contact with the second high reflectivity anode metal; an LED die positioned on top of a second most reflective anode metal; The electrode connection PAD corresponds to the LED die one by one. The LED die is truncated cone-shaped on the XZ plane and circular on the XY plane. The top of the LED die is a GaN microlens array. A passivation layer located on both sides of the LED die, on both sides of the second highest reflectivity anode metal, and on top of the dielectric layer; A reflection ring filling substrate located on the first high reflectivity anode metal; in the XZ plane, the reflection ring filling substrate is in a positive trapezoidal shape; Cathode electrodes located on both sides and above the reflection ring filling substrate, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and above the passivation layer, and on the top of the LED die; The cathode electrode is in contact with the surface coating of the reflection ring and the first high reflectivity anode metal, and is not in contact with the second high reflectivity anode metal; a reflective ring surface coating on the cathode electrode at the reflective ring filling substrate; A protective dielectric layer and a dielectric microlens are located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflective ring. The protective dielectric layer and the dielectric microlens, the LED die, the GaN microlens array, and the electrode connection PAD center are collinear.

2. A Micro-LED structure for improving light extraction efficiency according to claim 1, characterized in that: The LED die is made of a GaN-based Micro-LED epitaxial wafer with light-emitting quantum wells.

3. A Micro-LED structure for improving light extraction efficiency according to claim 2, characterized in that: The LED die is in contact with the second high-reflectivity anode metal, in which the P-type GaN region forms an ohmic contact with the upper surface of the second high-reflectivity anode metal, and a GaN microlens array is formed above the N-type GaN region by etching; The LED die forms an ohmic contact with the cathode electrode.

4. A Micro-LED structure for improving light extraction efficiency according to claim 3, characterized in that: The N-type GaN region material is Si-doped GaN with a doping concentration of ≥1×10 18 cm -3 , thickness ≥ 800 nm; the P-type GaN region material is hole-conducting Mg-doped GaN, with a doping concentration ≥ 1×10 19 cm -3 , thickness ≥200 nm.

5. The Micro-LED structure for improving light extraction efficiency according to claim 3, characterized in that: The ratio of the lens curvature radius of the GaN microlens array to the pixel line width in the LED die ranges from 0.5 to 2.

6. The Micro-LED structure for improving light extraction efficiency according to claim 1, characterized in that: The first high-reflectivity anode metal and the second high-reflectivity anode metal have the same structure, both including an anode ohmic contact film layer, a reflective film layer and a bonding metal film layer arranged from top to bottom; the upper surface reflectivity of the first high-reflectivity anode metal and the second high-reflectivity anode metal is higher than 80%.

7. The Micro-LED structure for improving light extraction efficiency according to claim 1, characterized in that: The material of the protective dielectric layer and dielectric microlens is one or more combinations of silicon oxide, silicon oxynitride, silicon nitride, and aluminum oxide, with a refractive index between 1.4 and 2.

5. The ratio of the lens curvature radius of the protective dielectric layer and dielectric microlens to the pixel line width in the LED core is in the range of 0.5 to 3.

8. A method for manufacturing a Micro-LED structure with improved light extraction efficiency, for manufacturing a Micro-LED structure with improved light extraction efficiency as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Electrodes are formed on the surface of the driving backplane to connect the PAD and the dielectric layer. The upper surface of the PAD and the dielectric layer are bonded to the GaN-based Micro-LED epitaxial wafer through a highly reflective anode metal; S2, etching the GaN-based Micro-LED epitaxial wafer, removing the substrate in the GaN-based Micro-LED epitaxial wafer and forming a GaN microlens array, wherein the center of the GaN microlens array coincides with the center of the electrode connection PAD; S3, etching the GaN-based Micro-LED epitaxial wafer, forming LED tube cores corresponding to the electrode connection PADs one by one and a reflection ring filling substrate located between the LED tube cores on the XZ plane, wherein the LED tube cores are not in contact with the reflection ring filling substrate, the LED tube core is in a truncated cone shape, the GaN microlens array is located on the top of the LED tube core, and the reflection ring filling substrate is in a regular trapezoid shape; etching the high-reflectivity anode metal, forming a second high-reflectivity anode metal located under the LED tube core and a first high-reflectivity anode metal located under the reflection ring filling substrate on the XZ plane; wherein the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal; S4, generating a passivation layer located on both sides of the LED tube core, on both sides of the second high reflectivity anode metal, and on the dielectric layer, generating a cathode electrode located on both sides and on the reflection ring filling base, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and on the passivation layer, and on the top of the LED tube core, and generating a reflection ring surface coating located on the cathode electrode at the reflection ring filling base; S5. Generate a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflection ring.

9. A method for manufacturing a Micro-LED structure with improved light extraction efficiency, for manufacturing a Micro-LED structure with improved light extraction efficiency as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Electrodes are formed on the surface of the driving backplane to connect the PAD and the dielectric layer. The upper surface of the PAD and the dielectric layer are bonded to the GaN-based Micro-LED epitaxial wafer through a highly reflective anode metal; S2, etching the GaN-based Micro-LED epitaxial wafer, removing the substrate in the GaN-based Micro-LED epitaxial wafer and forming a GaN microlens array, wherein the center of the GaN microlens array coincides with the center of the electrode connection PAD; S3, etching the GaN-based Micro-LED epitaxial wafer, forming LED tube cores corresponding to the electrode connection PADs on the XZ plane, the LED tube cores are truncated, and the GaN microlens array is located on the top of the LED tube core, etching the high-reflectivity anode metal, forming the second high-reflectivity anode metal and the first high-reflectivity anode metal under the LED tube core on the XZ plane; wherein the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal; using PECVD and photolithography processes to etch to form a reflection ring filling substrate located between the LED tube cores; the first high-reflectivity anode metal is located under the reflection ring filling substrate; the reflection ring filling substrate is made of insulating material; S4, generating a passivation layer located on both sides of the LED tube core, on both sides of the second high reflectivity anode metal, and on the dielectric layer, generating a cathode electrode located on both sides and on the reflection ring filling base, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and on the passivation layer, and on the top of the LED tube core, and generating a reflection ring surface coating located on the cathode electrode at the reflection ring filling base; S5. Generate a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflection ring.

10. A method for manufacturing a Micro-LED structure with improved light extraction efficiency, for manufacturing a Micro-LED structure with improved light extraction efficiency as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Electrodes are formed on the surface of the driving backplane to connect the PAD and the dielectric layer. The upper surface of the PAD and the dielectric layer are bonded to the GaN-based Micro-LED epitaxial wafer through a highly reflective anode metal; S2, etching the GaN-based Micro-LED epitaxial wafer, removing the substrate in the GaN-based Micro-LED epitaxial wafer and forming a GaN microlens array, wherein the center of the GaN microlens array coincides with the center of the electrode connection PAD; S3, etching the GaN-based Micro-LED epitaxial wafer, forming an LED die corresponding to the electrode connection PAD on the XZ plane, the LED die is in a truncated cone shape, the GaN microlens array is located on the top of the LED die, etching the high-reflectivity anode metal, forming a second high-reflectivity anode metal and a first high-reflectivity anode metal under the LED die on the XZ plane; wherein the first high-reflectivity anode metal is not in contact with the second high-reflectivity anode metal; S4, generating a passivation layer located on both sides of the LED tube core, on both sides of the second high reflectivity anode metal, and on the dielectric layer, generating a reflection ring filling substrate located between the LED tube cores through evaporation and stripping processes, and the first high reflectivity anode metal is located under the reflection ring filling substrate; the reflection ring filling substrate is made of metal; generating cathode electrodes located on both sides and on the reflection ring filling substrate, on both sides of the first high reflectivity anode metal, on the dielectric layer, on both sides and on the passivation layer, and on the top of the LED tube core, and generating a reflection ring surface coating on the cathode electrode at the reflection ring filling substrate; S5. Generate a protective dielectric layer and a dielectric microlens located on the dielectric layer, on the cathode electrode, and on the surface coating of the reflection ring.

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