Mirror layer for micro light emitting diode and forming method thereof

Abstract

The invention relates to a reflector layer used for a miniature light emitting diode, the reflector layer is configured to reflect light from a light emitting table top to a light emitting side, the area of the upper surface, facing the light emitting side, of the light emitting table top is larger than that of the lower surface, back to the light emitting side, of the light emitting table top, and the reflector layer comprises a main body part, the cover is arranged to cover the lower surface of the light-emitting table top and surround the side surface of the light-emitting table top; the edge part is connected with the edge of the main body part, an included angle larger than 0 degree is formed between the edge part and the main body part, and the edge parts of the reflecting mirror layers of the adjacent micro light-emitting diodes are disconnected from each other. The invention also relates to a method for producing a mirror layer. Defects of the reflector layer can be reduced, so that the luminous efficiency of the micro light-emitting diode is improved.

Description

Technical Field

[0001] The present invention generally relates to the field of micro light emitting diodes, and more specifically, to a reflector layer for a micro light emitting diode. In addition, the present invention also relates to a micro light emitting diode having such a reflector layer.

[0003] Micro Light Emitting Diode is a new type of LED structure obtained by thin-filming, miniaturizing and arraying the original LED structure. It integrates arrayed micron-sized micro light-emitting diodes on an active addressing drive panel to realize the lighting and individual control of the micro light-emitting diodes, thereby outputting the desired display image. The core structure of the micro light-emitting diode is a light-emitting table, which includes a PN junction diode, which is composed of a direct bandgap semiconductor material. When the upper and lower electrodes apply a forward bias to the micro light-emitting diode to cause current to pass through, electrons and holes recombine in the active region and emit single-color light photons at the same time.

[0004] The reflector layer is a reflective structure surrounding the light-emitting mesa, and its function is to reflect the light emitted by the light-emitting mesa toward the direction of the microlens. At present, the reflector layer is generally manufactured by photolithography, etching deposition, and other processes. However, due to the limitations of the current process, the reflector layer is prone to defects such as small or incomplete coverage area and difficulty in removing the photoresist mold. Summary of the invention

[0005] The task of the present invention is to provide a reflector layer for a micro light emitting diode, a method for forming the reflector layer, and a micro light emitting diode. Through the reflector layer, the method, or the micro light emitting diode, the defects of the reflector layer can be reduced, thereby improving the luminous efficiency of the micro light emitting diode.

[0006] In a first aspect of the present invention, the aforementioned task is solved by a reflector layer for a micro light emitting diode, wherein the reflector layer is configured to reflect light from a light emitting mesa toward a light emitting side, and the area of ​​the upper surface of the light emitting mesa facing the light emitting side is larger than the area of ​​the lower surface facing away from the light emitting side, wherein the reflector layer comprises:

[0007] a main body portion arranged to cover the lower surface of the light emitting mesa and surround the side surfaces of the light emitting mesa; and

[0008] The edge portion is connected to the edge of the main body portion and forms an angle greater than 0° with the main body portion, wherein the edge portions of the reflector layers of adjacent micro-light emitting diodes are disconnected from each other.

[0009] In one embodiment of the present invention, the angle ranges from 5° to 85°.

[0010] In another embodiment of the present invention, it is provided that:

[0011] The edge portion has a length of 0.1 to 0.2 μm and a thickness of 0.2 to 0.4 μm; and / or

[0012] The thickness of the main body is 0.2 to 0.5 μm; and / or

[0013] The lowermost side of the edge portion is flush with or not flush with the lower surface of the light emitting table.

[0014] In another embodiment of the present invention, the cross-sectional shape of the main body portion in a cross section parallel to the upper surface of the light-emitting mesa is one of the following:

[0015] A triangle, a square, a rectangle, a circle, an ellipse, and an n-gon, wherein n is an integer greater than 4.

[0016] In another embodiment of the present invention, the cross-sectional shape of the main body is in the positive direction, and the cross-sectional shape of the light-emitting table is a circle, wherein the circle is an inscribed circle of the square, and the circle has rounded outer corners.

[0017] In another embodiment of the present invention, it is provided that:

[0018] The distance between the lowermost side of the connection portion between the edge portion and the main body portion and the upper surface of the light-emitting mesa is 0 to 0.8 μm; and / or

[0019] The distance between the edge portions of the reflector layers of adjacent micro light emitting diodes is 0.3 μm to 2 μm.

[0020] In another embodiment of the present invention, the reflector layer includes, starting from the side facing the light-emitting mesa:

[0021] an atomic layer deposition layer, the material of which is selected from the group consisting of nickel, platinum, titanium, and tantalum;

[0022] a reflective metal layer configured to reflect light, the reflective metal layer being made of a material selected from the group consisting of: silver, aluminum, and gold;

[0023] a first barrier layer comprising at least first and second barrier layers, wherein the materials of the first and second barrier layers are respectively selected from the group consisting of platinum, titanium, and tantalum; and

[0024] The second barrier layer is made of a material selected from the group consisting of platinum, titanium, and tantalum.

[0025] In another embodiment of the present invention, the material of the second barrier layer is the same as the material of the first barrier layer.

[0026] In another embodiment of the present invention, it is provided that:

[0027] The ALD layer material is nickel;

[0028] The material of the reflective metal layer is silver;

[0029] The materials of the first and second barrier layers are titanium and platinum, respectively; and

[0030] The material of the second barrier layer is titanium.

[0031] In another embodiment of the present invention, it is provided that:

[0032] The thickness of the ALD layer is 3 to 8 angstroms;

[0033] The thickness of the reflective metal layer is 800 to 1200 angstroms;

[0034] The first barrier layer has a thickness of 100 to 300 angstroms, and the second barrier layer has a thickness of 400 to 600 angstroms; and

[0035] The second barrier layer has a thickness of 100 to 300 angstroms.

[0036] In another embodiment of the present invention, the reflector layer includes N first barrier layers and N second barrier layers that are alternately arranged with each other, wherein N is an integer, and N=2-5.

[0037] In a second aspect of the present invention, the aforementioned task is solved by a photoresist ring for forming a reflector layer according to the present invention, wherein the photoresist ring is configured to form (e.g., mold) the reflector layer, and the photoresist ring comprises:

[0038] a lower ring arranged to surround the light emitting mesa of the micro light emitting diode; and

[0039] The upper ring is arranged on the lower ring, wherein at a connection portion between the upper ring and the lower ring, a thickness of the upper ring is greater than a thickness of the lower ring.

[0040] In one embodiment of the present invention, at the connection portion between the upper ring and the lower ring, the thickness of the upper ring is 20% to 60% greater than the thickness of the lower ring.

[0041] In another embodiment of the present invention, the height of the lower ring is 2 / 3 of the height of the light-emitting table; or

[0042] The height of the lower ring is the same as the height of the light-emitting layer of the light-emitting mesa.

[0043] In another embodiment of the present invention, it is provided that:

[0044] The height of the lower ring is 0.2 to 0.5 μm and the height of the upper ring is 1.3 to 1.7 μm; and / or

[0045] The thickness of the lower ring is 1.9 to 2.4 μm, and the thickness of the upper ring is 1.8 to 2.3 μm.

[0046] In another embodiment of the present invention, the bottom of the upper ring is lower than the lower surface of the light-emitting mesa, and the top is higher than the lower surface of the light-emitting mesa.

[0047] In another embodiment of the present invention, it is provided that:

[0048] The cross-sectional shape of the upper ring and / or the lower ring in the cross section parallel to the upper surface of the light-emitting mesa is one of the following: a triangle, a square, a rectangle, a circle, an ellipse, and an n-gon, wherein n is an integer greater than 4; and / or

[0049] The shape of the longitudinal section of the upper ring and / or the lower ring in the longitudinal section perpendicular to the upper surface of the light-emitting mesa is one of the following: a trapezoid, a triangle.

[0050] In another embodiment of the present invention, the cross-sectional shape of the upper ring and the lower ring is a square, and the square has rounded inner corners.

[0051] In another embodiment of the present invention, the lower ring is formed in a first photolithography step, and the lower ring is formed in a second photolithography step after the first photolithography step.

[0052] In another embodiment of the present invention, it is provided that:

[0053] The lower ring has a gradually decreasing thickness in a longitudinal section perpendicular to the upper surface of the light-emitting mesa; and

[0054] The upper ring has a gradually decreasing thickness in a longitudinal section perpendicular to the upper surface of the light-emitting mesa.

[0055] In a third aspect of the present invention, the aforementioned object is solved by a micro-light emitting diode chip, the micro-light emitting diode chip comprising:

[0056] Illuminated countertop, including:

[0057] A transparent conductive layer, which is arranged on a side of the light-emitting surface facing away from the light-emitting side;

[0058] a first epitaxial layer disposed between the transparent conductive layer and the light emitting layer;

[0059] a light emitting layer disposed between the first epitaxial layer and the second epitaxial layer and configured to emit light; and

[0060] A second epitaxial layer is arranged on a side of the light-emitting mesa facing the light-emitting side, wherein the area of ​​the second epitaxial layer is larger than the area of ​​the first epitaxial layer;

[0061] A reflector layer according to the present invention, which is arranged to surround the light-emitting mesa;

[0062] an insulating layer configured to accommodate the light emitting mesas and the via contacts;

[0063] A driving circuit having a metal layer, a plurality of through-hole contacts being arranged on the driving circuit, the through-hole contacts being electrically connected to the metal layer, the micro-LED array region being bonded to the driving circuit through a bottom conductive bonding layer, wherein the driving circuit further has a wiring stack under the metal layer, which is configured to lead out a first electrode;

[0064] a first electrode electrically connected to the through-hole contact portion;

[0065] a passivation layer covering at least a portion of a side surface of the light-emitting mesa;

[0066] a top transparent conductive layer, which is disposed on a surface of the passivation layer and is in electrical contact with the second epitaxial layer; and

[0067] The second electrode is disposed on the surface of the transparent conductive layer.

[0068] In one embodiment of the present invention, the second electrode is a ring-shaped reflective electrode, which is arranged around the light-emitting mesa.

[0069] In another embodiment of the present invention, the polarity of the second electrode is opposite to that of the first electrode.

[0070] In another embodiment of the present invention, the material of the second epitaxial layer is a material layer of the second conductivity type containing two or more elements of Ga, N, As, Al, In, and P, and the first epitaxial layer is a material layer of the first conductivity type containing two or more elements of Ga, N, As, Al, In, and P, wherein the first conductivity type is different from the second conductivity type.

[0071] In another embodiment of the present invention, the light emitting layer comprises a multi-quantum well layer, wherein the multi-quantum well layer is an InGaN / GaN multi-quantum well layer, an InGaN / AlGaN multi-quantum well layer, an InGaAs / AlGaAs multi-quantum well layer, or an AlGaInP multi-quantum well layer.

[0072] In another embodiment of the present invention, an electron blocking layer is disposed on a first side of the light-emitting layer, wherein the first side refers to a side along which electrons migrate out of the light-emitting layer.

[0073] In another embodiment of the present invention, the material of the passivation layer is Si3N4 film, SiO2 film or Al2O3 film.

[0074] In another embodiment of the present invention, it is provided that:

[0075] The material of the insulating layer is selected from the group consisting of silicon dioxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon carbonitride (SiCN), hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), zirconium oxide (ZrO2), lanthanum oxide (La2O3), magnesium oxide (MgO), phospho-silicate glass (PSG), boro-phospho-silicate glass (BPSG), or any combination thereof; and / or

[0076] The material of the metal layer is selected from the group consisting of aluminum (Al), copper (Cu), tungsten (W), silver (Ag), gold (Au), nickel (Ni), platinum (Pt), tantalum (Ta), and molybdenum (Mo).

[0077] In another embodiment of the present invention, the through-hole contact portion includes a first and a second through-hole contact portion, and the insulating layer includes a first and a second insulating layer, and the micro-light-emitting diode chip includes an upper stack and a lower stack, wherein the upper stack includes a first insulating layer, a light-emitting table and a first through-hole contact portion, and the lower stack includes a second insulating layer, a second through-hole contact portion and a driving circuit, wherein the lower stack is joined to the upper stack by hybrid bonding, so that the first through-hole contact portion is bonded to the second through-hole contact portion, and the first insulating layer is bonded to the second insulating layer.

[0078] In a fourth aspect of the invention, the aforementioned task is solved by a method for forming a reflector layer, the method comprising the following steps:

[0079] Provide a light-emitting countertop;

[0080] A lower ring is formed around the light-emitting table;

[0081] forming an upper ring on the lower ring, wherein at a connection portion between the upper ring and the lower ring, a thickness of the upper ring is greater than a thickness of the lower ring;

[0082] Applying a reflector layer on the light-emitting mesa, the upper ring and the lower ring, wherein the reflector layer forms a suspended layer separated from the lower ring at the connecting portion, and the lower ring has a gap under the suspended layer that is not covered by the reflector layer; and

[0083] Remove the upper and lower rings.

[0084] In one embodiment of the present invention, forming a lower ring around the light-emitting mesa and forming an upper ring on the lower ring comprises the following steps:

[0085] Covering the light-emitting mesa with a photoresist to form a first photoresist layer;

[0086] exposing the first photoresist layer;

[0087] Covering the first photoresist layer with photoresist to form a second photoresist layer;

[0088] exposing the second photoresist layer; and

[0089] The first and second photoresist layers are developed and washed to form a lower ring and an upper ring.

[0090] In another embodiment of the present invention, removing the upper ring and the lower ring comprises:

[0091] Cleaning the upper ring and the lower ring with a degumming liquid, so that the degumming liquid enters the bottom of the lower ring through the gap;

[0092] Removing the lower ring by means of a debonding solution; and

[0093] Remove the upper ring connected to it by removing the lower ring.

[0094] The present invention has at least the following beneficial effects:

[0095] (1) The present invention can improve the quality of the reflector layer by using a photoresist ring to form the reflector layer, because the photoresist ring can reliably isolate and disconnect the reflector layers of adjacent light-emitting mesas to prevent short circuits. At the same time, the photoresist ring can limit the formed reflector layer to a desired range, that is, surround the light-emitting mesas, and at the same time ensure that the metal is fully deposited on the lower surface and side surfaces of the light-emitting mesas. The reflector layer manufactured in this way can reliably disconnect between adjacent light-emitting mesas, and at the same time, an edge portion inclined or curved toward the lower surface of the light-emitting mesas can be formed at its edge, so that the edge of the reflector layer is away from the conductive structure on the upper surface of the light-emitting mesas, such as the epitaxial layer or the transparent conductive layer, to prevent short circuits. At the same time, it can ensure that the reflector layer has sufficient thickness on the upper surface of the light-emitting mesas, ensure sufficient coverage at the edge and improve the edge coverage quality.

[0096] (2) The photoresist ring used in the present invention is a double-layer structure, wherein the connection between the upper ring and the lower ring has a thickness jump, so that when the reflector layer is coated on the light-emitting table, the upper ring and the lower ring, the reflector layer forms a suspended layer separated from the lower ring at the connection, and because the reflector layer cannot continue to be attached to the suspended layer, the lower ring has a gap under the suspended layer that is not covered by the reflector layer. The gap can allow the degumming liquid to enter the root of the lower ring during the degumming process, so that the lower ring can be reliably removed by the degumming liquid, and the upper ring on the lower ring and the reflector layer attached thereto are removed at the same time, thereby achieving complete removal of the photoresist mold body.

[0097] (3) By changing the shape of the photoresist ring, the shape of the reflector layer can be reliably changed. For example, by using a square photoresist ring, a square reflector layer surrounding the light-emitting table can be formed, thereby increasing the reflection surface. Using the photoresist ring, reflector layers of other shapes are all achievable, such as triangle, rectangle, ellipse, circle, quadrilateral or more n-gon, etc.

[0098] (4) By adding an atomic layer deposition layer made of a barrier metal on the side of the reflector layer facing the light-emitting mesa, the metal in the reflector can be effectively prevented from diffusing into the light-emitting mesa through the bottom transparent conductive layer arranged between the reflector layer and the light-emitting mesa, causing the performance degradation or failure of the light-emitting mesa, and inhibiting the oxidation of the reflective metal, thereby inhibiting the reduction of the reflection efficiency caused by oxidation. In addition, the present invention significantly improves the metal barrier effect by changing the number of alternating metal stacks (for example, alternating stacks of platinum layers and titanium layers) in the reflector layer; in addition, the second and third barrier layers made of a barrier metal are also arranged on the side of the reflector layer facing away from the light-emitting mesa, which can effectively inhibit the diffusion of easily diffusible metals such as silver in the reflector layer into the insulating layer, thereby avoiding short circuit or failure of the insulating layer caused by diffusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] The present invention will be further described below in conjunction with specific embodiments with reference to the accompanying drawings.

[0100] Figure 1 A first embodiment of a reflector layer for a micro light emitting diode according to the present invention is shown;

[0101] Figure 2 A second embodiment of a reflector layer for a micro light emitting diode according to the present invention is shown;

[0102] Figure 3 A first embodiment of a layered structure of a mirror layer according to the invention is shown;

[0103] Figure 4 A second embodiment of the layered structure of the mirror layer according to the invention is shown;

[0104] Figure 5 A first application scenario of the reflector layer according to the present invention is shown;

[0105] Figure 6 A schematic diagram showing a first embodiment of a photoresist ring for forming a reflector layer according to the present invention;

[0106] Figure 7 A schematic diagram showing a second embodiment of a photoresist ring for forming a reflector layer according to the present invention;

[0107] Figure 8 A schematic top view of a method for forming a reflector layer according to the present invention is shown; and

[0108] Figures 9A to 9D The steps of a method of forming a mirror layer are shown. DETAILED DESCRIPTION

[0109] It should be noted that the components in the figures may be shown exaggeratedly for the sake of illustration and are not necessarily true to scale. In the figures, identical or functionally identical components are provided with the same reference numerals.

[0110] In the present invention, unless otherwise specified, "arranged on...", "arranged above..." and "arranged above..." do not exclude the existence of an intermediate between the two. In addition, "arranged on or above..." merely indicates the relative positional relationship between two components, and in certain cases, such as after reversing the product direction, it can also be converted into "arranged below or below...", and vice versa.

[0111] In the present invention, each embodiment is only intended to illustrate the aspects of the present invention and should not be construed as limiting.

[0112] In the present invention, unless otherwise specified, the quantifiers "a", "an" and "an" do not exclude the presence of a plurality of elements.

[0113] In the present invention, the term “connected” may refer to both being directly connected or being indirectly connected via an intermediate element.

[0114] In the present invention, the term "configuration" refers to the setting of the shape, structure, material and / or function of the target object to achieve the desired technical effect, wherein "configuration" includes a variety of alternative technical means for achieving the technical effect, which become obvious under the teaching of the present invention.

[0115] It should also be noted that in the embodiments of the present invention, for the sake of clarity and simplicity, only a portion of the parts or components may be shown, but those of ordinary skill in the art will understand that under the teachings of the present invention, the required parts or components may be added according to the needs of the specific scenario. In addition, unless otherwise specified, the features in different embodiments of the present invention may be combined with each other. For example, a feature in the second embodiment may be used to replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment also falls within the disclosure scope or recorded scope of the present application.

[0116] It should also be noted that within the scope of the present invention, the terms "same", "equal", "equal to" and the like do not mean that the values ​​of the two are absolutely equal, but allow a certain reasonable error, that is, the terms also cover "substantially the same", "substantially equal", "substantially equal to". By analogy, in the present invention, the terms "perpendicular to", "parallel to" and the like indicating directions also cover the meanings of "substantially perpendicular to" and "substantially parallel to".

[0117] In the present invention, the term "configuration" refers to the setting of the shape, structure, material and / or function of the target object to achieve the desired technical effect, wherein "configuration" includes a variety of alternative technical means for achieving the technical effect, which become obvious under the teaching of the present invention.

[0118] In the present invention, the term "upward reflection" means that light is reflected so that the distance between the reflected light and the upper surface of the light-emitting table becomes increasingly greater. The upward direction includes directly above and obliquely above.

[0119] In the present invention, the term "upper surface of the light-emitting mesa" refers to the surface of the light-emitting mesa facing the light-emitting side (i.e., the direction of the lens), and the term "lower surface of the light-emitting mesa" refers to the surface of the light-emitting mesa facing away from the light-emitting side (e.g., toward the driving circuit). The term "side surface of the light-emitting mesa" refers to the surface of the light-emitting mesa located between the upper surface and the lower surface of the light-emitting mesa.

[0120] Figure 1 A first embodiment of a reflector layer 102 for a micro light emitting diode according to the present invention is shown.

[0121] like Figure 1 As shown, the reflector layer 102 for a micro-LED according to the present invention is configured to reflect light from the light-emitting mesa 101 of the micro-LED toward the light-emitting side (direction A in the figure). The area of ​​the upper surface A of the light-emitting mesa 101 facing the light-emitting side is larger than the area of ​​the lower surface B facing away from the light-emitting side.

[0122] The light-emitting mesa 101 is configured to emit light, and includes a first epitaxial layer 101C, a light-emitting layer 101C, and a second epitaxial layer 101A, wherein the first epitaxial layer 101C has a different conductivity type from the second epitaxial layer 101A, for example, one of them is n-type and the other is p-type, or vice versa. The light-emitting mesa 101 is arranged on a temporary substrate 104. After the temporary substrate 104 is removed (for example, by debonding or grinding), the upper surface of the light-emitting mesa 101 will be exposed. A transparent conductive layer 105 is arranged at the lower surface B of the light-emitting mesa 101, which is configured to electrically connect the second epitaxial layer A at the lower surface B to an electrode (not shown, such as an anode) through a conductive reflector layer 102. In addition, a passivation layer 103 is arranged on the side and part of the lower surface B of the light-emitting mesa 101, and the passivation layer 103 is configured to reduce current leakage at the side wall, passivate side wall defects, and prevent water, oxygen, etc. from damaging the light-emitting mesa 101 during operation. The passivation layer 103 has a notch at the lower surface B to expose the transparent conductive layer 105 for electrical connection. The side surface of the light-emitting mesa 101 between the upper surface A and the lower surface B may have an inclination angle of 55° to 75°, preferably 60° to 70°, to improve the aperture ratio.

[0123] The reflector layer 102 includes a main body portion 102A and an edge portion 102B. These two portions are described below.

[0124] Main body

[0125] The main body 102A is arranged to cover the lower surface B of the light-emitting mesa 101 and surround the side surface of the light-emitting mesa 101 between the upper surface A and the lower surface B. Here, the main body 102 of the reflector layer 102 fills the gap of the passivation layer 103 for electrical connection between the transparent conductive layer 101 and the electrode. In this embodiment, the reflector layer 102 covers the entire side surface of the light-emitting mesa 101, but in other embodiments, the reflector layer 102 may also cover only a portion of the side surface of the light-emitting mesa 101. The side surface portion of the main body may have the same inclination angle with the upper surface of the light-emitting mesa 101 as the side surface of the light-emitting mesa 101 and the upper surface A, and the inclination angle is, for example, 55° to 75°, preferably 60° to 70°. The side and bottom portions of the main body 102A basically and completely cover the surface of the light-emitting table 101 except the upper surface A for emitting light, and can reflect the light emitted by the light-emitting table 101 toward the light-emitting side, that is, the direction of the upper surface A, thereby reflecting as much light as possible from the light-emitting table 101 other than the light-emitting side. After one or more reflections, these lights can be redirected to the light-emitting side, thereby improving the light extraction rate or light extraction efficiency (LEE) of the micro-LED. The thickness of the main body can be, for example, 0.2 to 0.5 μm. For the layered structure and materials of the main body 102A and the edge portion 102B, please refer to Figure 3 and its description.

[0126] Edge

[0127] The edge portion 102B of the reflector layer 102 is connected to the edge or end of the main body 102A of the reflector layer 102, and the edge portion 102B forms an angle α greater than 0° with the main body 102A, wherein the edge portions 102B of the reflector layer 102 of adjacent micro-LEDs are disconnected from each other. The length of the edge portion 102B can be, for example, 0.1 to 0.2 μm, and the thickness can be, for example, 0.2 to 0.4 μm. Depending on the process or the shape of the photoresist ring used to form the edge portion 102B, the angle α can be 5° to 85°, preferably 20° to 70°, most preferably 30° to 60°, for example 45°. The lowermost side of the edge portion 102B can be flush or not flush with the lower surface B of the light-emitting table 101, that is, on a straight line or not on a straight line (higher than the lower surface B). For example, the distance between the lowermost side of the connection between the edge portion and the main body and the upper surface of the light-emitting table is 0, that is, they are in contact with each other, or the distance is not zero, that is, they are not in contact with each other, and the distance can be, for example, 0 to 0.8 μm. The longitudinal cross-sectional shape of the edge portion 102B in the cross-section perpendicular to the upper surface can be, for example, a triangle, a rectangle, a trapezoid, an ellipse, an irregular shape with a curved surface, etc. The edge portions 102B of the reflector layer 102 of adjacent micro-light-emitting diodes are disconnected from each other without electrical contact, and the distance between them can be, for example, 0.3 to 5 μm. For the layered structure and materials of the main body 102A and the edge portion 102B, please refer to Figure 3 and its description.

[0128] It can be seen from the above structure that the reflector layer 102 according to the present invention has good quality, because the reflector layer 102 is disconnected from each other between adjacent light-emitting mesas 101 to prevent short circuit. At the same time, the edge of the reflector layer 102 also has an edge portion 102A that is bent or inclined toward the lower surface B of the light-emitting mesas, so that the edge of the reflector layer 102 can be away from the conductive structure at the upper surface A of the light-emitting mesas 102, such as the epitaxial layer or the transparent conductive layer, thereby reducing the risk of short circuit; at the same time, it can also ensure that the reflector layer 102 has sufficient thickness at the upper surface A of the light-emitting mesas 101, ensuring sufficient coverage at the edge and improving the edge coverage quality.

[0129] Figure 2 A second embodiment of a reflector layer 102 for a micro light emitting diode according to the present invention is shown.

[0130] Figure 2 The second embodiment shown is Figure 1The first embodiment shown is basically the same, with the main difference being that, in the second embodiment, the edge portion 102B of the reflector layer 102 has a rectangular shape, and the connection portion between the main body portion 102A and the edge portion 102B does not contact the temporary substrate 104, that is, there is a certain distance from the lower surface A, thereby further reducing the area of ​​the reflector layer 102 exposed from the insulating layer surrounding the light-emitting table 101, thereby reducing the risk of short circuit.

[0131] Figure 3 A first embodiment of a layered structure of a mirror layer 200 according to the invention is shown.

[0132] like Figure 3 The reflector layer 200 according to the present invention includes, from top to bottom, an atomic layer deposition layer 201, a reflective metal layer 202, a first barrier layer 203, and a second barrier layer 204, wherein the upper side of the reflector layer 200 faces the light-emitting mesa or epitaxial layer of the micro-light-emitting diode, and the lower side of the reflector layer 200 faces away from the light-emitting mesa or epitaxial layer of the micro-light-emitting diode or faces the bottom transparent conductive layer. Each layer is described below.

[0133] ·Atomic layer deposition layer 201, which is arranged at the uppermost layer, i.e., the outermost layer toward the light-emitting mesa or epitaxial layer. The material of the atomic layer deposition layer 201 may include nickel, platinum, titanium, and tantalum, for example. The material of the atomic layer deposition layer 201 is preferably nickel. The thickness of the atomic layer deposition layer is 3 to 8 angstroms, preferably 5 angstroms. 1 angstrom = 10^(-10) meters. The function of the atomic layer deposition layer 201 is to deposit a certain thickness of barrier metal (e.g., nickel) on the outer side of the reflective metal layer 201 through an atomic layer deposition (ALD) process, and the barrier metal can effectively block or at least inhibit the outward diffusion of the reflective metal layer 201, for example, preventing it from diffusing through the transparent conductive layer into the light-emitting mesa or epitaxial layer disposed thereon.

[0134] A reflective metal layer 202 is disposed between the atomic layer deposition layer 201 and the first barrier layer 203 and is configured to reflect light. The material of the reflective metal layer 202 may include silver, aluminum, and gold, for example.

[0135] Aluminum (Al): Aluminum is a commonly used optical reflective material. It has a high reflectivity, which can reach about 80%-90% in the visible light range. In addition, the cost of aluminum is relatively low, and it is easy to form reflectors of various shapes. Aluminum also has a certain reflective ability in the ultraviolet and infrared regions, but its reflective performance will change with the change of wavelength.

[0136] Silver (Ag): The reflectivity of silver is higher than that of aluminum in the visible light band, reaching more than 95%, especially in the blue and green light bands, where its reflectivity is even better. However, silver is easily oxidized, and the reflectivity of oxidized silver decreases. In addition, silver is easy to diffuse. In view of the fact that silver is easy to diffuse and oxidize, the inventors can better prevent the diffusion and oxidation of the reflective metal layer made of silver by arranging an atomic layer deposition layer 201 before the silver layer.

[0137] Gold (Au): Gold has good reflective properties in the infrared band, and its reflectivity in the infrared region can be as high as 98% or more. However, the reflectivity of gold in the visible light band is relatively low, and the color is golden yellow, so gold is mainly used for light reflection of infrared micro-LEDs.

[0138] The material of the reflective metal layer 201 is preferably a metal with high reflectivity, such as silver. The thickness of the reflective metal layer can be, for example, 800 to 1200 angstroms, preferably 1000 angstroms.

[0139] The principle of metal reflection light is as follows: when light shines on the metal surface, the free electrons in the metal will be forced to vibrate under the action of the electric field of the light. These vibrating electrons will radiate electromagnetic waves with the same frequency as the incident light. This is the source of the reflected light.

[0140] The penetration depth of light in metal (also called skin depth) is a physical quantity related to the material properties of the metal and the frequency of light. It represents the distance that light penetrates when the intensity of light decays to 1 / e (about 37%) of the surface intensity. For metals, the penetration depth of light is usually at the nanometer level. In other words, light can penetrate a certain depth (e.g. 200 nanometers) at the nanometer level on the metal surface.

[0141] In view of this, the atomic layer deposition layer 201 is constructed to be as thin as possible, for example, not more than 10 angstroms, such as 3 to 8 angstroms, preferably 5 angstroms, so that the light from the light-emitting table can penetrate the surface atomic layer deposition layer 201 as unimpeded as possible, and be reflected by the reflective metal layer 202 with high reflectivity arranged therebehind. On the other hand, if the atomic layer deposition layer 201 is too thin, its metal barrier function will be affected, so the inventors uniquely set its layer thickness to 3 to 8 angstroms, preferably 5 angstroms, so that both good metal barrier is achieved and the high reflectivity of the reflective metal layer 202 is taken into account.

[0142] A first barrier layer 203, which is arranged between the reflective metal layer 202 and the second barrier layer 204 and includes at least a first barrier layer 203A and a second barrier layer 203B. The first barrier layer 203A and the second barrier layer 203B may include platinum, titanium, and tantalum, for example, respectively. The thickness of the first barrier layer is 100 to 300 angstroms, preferably 200 angstroms, and the thickness of the second barrier layer is 400 to 600 angstroms, preferably 500 angstroms. For example, the first barrier layer 203A is preferably made of titanium, and the second barrier layer 203B is preferably made of platinum. In addition, the first barrier layer 203 may be repeated, for example, the reflector layer 200 may include a plurality of first barrier layers 203 arranged one after another, for example, including 2, 3, 4, 5 or other number of first barrier layers 203. The first barrier layer 203 is configured to perform metal blocking on the reflective metal layer 202 from the back side and prevent it from being oxidized, and in particular, it may block metal atoms of the reflective metal layer such as silver from entering the insulating layer to affect its insulation. In particular, when the first and second barrier layers 203A and 203B are titanium and platinum, respectively, the stack of titanium and platinum has the following technical effects:

[0143] (1) The stacking of titanium and platinum can effectively prevent the reflective layer material from being oxidized or corroded by chemicals. In the reflective layer, if the base reflective material (such as silver) is oxidized, its reflectivity will drop significantly. Titanium and platinum have high chemical stability and can prevent oxygen and other chemicals that may cause the reflective layer material to deteriorate from contacting the core material of the reflective layer, such as silver, thereby ensuring that the reflective performance remains stable during long-term use.

[0144] (2) The stacking of titanium and platinum can adjust the optical constants of the reflective layer to make it better suited to different reflective metals. Different optical devices have different requirements for the optical parameters of the reflective layer (such as refractive index, extinction coefficient, etc.). Titanium and platinum have specific optical properties in the optical frequency band. By adjusting the thickness and number of layers of the stacking, the optical properties of the reflective metal layer can be fine-tuned to meet the needs of a specific optical system. In particular, when the number of stacking layers is 3, it has better reflective properties for the light of the light-emitting table of the micro-LED, and at the same time has better metal blocking ability and anti-oxidation ability for the silver reflective metal layer.

[0145] A second barrier layer 204 is arranged on the outermost side of the reflector layer 200 toward the bottom transparent conductive layer. The material of the second barrier layer 204 may include platinum, titanium, and tantalum, preferably titanium. The thickness of the second barrier layer may be, for example, 100 to 300 angstroms, preferably 200 angstroms. The second barrier layer 204 has metal blocking and anti-oxidation effects on one hand, and can prevent the oxidation of the reflective metal layer and block its metal diffusion on the other hand. On the other hand, it can participate in the fine-tuning of the reflective characteristics of the reflective metal layer, for example, forming a titanium-platinum-titanium fine-tuning stacked layer with the first and second barrier layers of the first barrier layer 203. In this case, the material of the second barrier layer 204 is preferably different from that of the first barrier layer, for example, both are titanium.

[0146] Figure 4 A second embodiment of a layered structure of a mirror layer 200 according to the invention is shown.

[0147] The reflector layer 200 of the second embodiment is basically the same as the reflector layer 200 of the first embodiment, with the main difference being that, in the second embodiment, the material of the atomic layer deposition layer is nickel with a thickness of 5 angstroms, the material of the reflective metal layer is silver with a thickness of 1000 angstroms, the materials of the first and second barrier layers are titanium and platinum with thicknesses of 200 and 500 angstroms respectively, and the material of the second barrier layer is titanium with a thickness of 200 angstroms; in addition, the number of layers of the first barrier layer 203 is 3.

[0148] In this embodiment, an atomic layer deposition layer 201 made of nickel is disposed on the front side of the silver metal reflective layer 202, and a first barrier layer 202 composed of three titanium layers and platinum layers is disposed behind the silver metal reflective layer 202, so that titanium and platinum appear alternately, and a second barrier layer 204 made of titanium is arranged behind the first barrier layer 202. In this way, the arrangement of three stacked pairs can improve the blocking and anti-oxidation effects on the silver reflective metal layer, and can also fine-tune the optical reflection characteristics of silver. In addition, the second barrier layer made of titanium and the first barrier layer 204 constitute a titanium-platinum-titanium stacked pair, which further fine-tunes the reflection characteristics of silver.

[0149] Figure 5 The first application scenario of the reflector layer 200 according to the present invention is shown. In this application scenario, the light-emitting table or epitaxial layer of the micro-LED chip 600 has an inverted trapezoidal structure, that is, the light-emitting table has a large upper surface and a small lower surface, so the reflector layer 200 is arranged to surround all sides of the light-emitting table in the insulating layer and cover its bottom surface, thereby maximizing the light reflection area and improving the light efficiency of the micro-LED.

[0150] The various components of the micro-LED chip 600 are described in detail below.

[0151] like Figure 5As shown, the micro-LED chip 600 according to the present invention comprises an upper stack 600A and a lower stack 600B, wherein the upper stack 600A and the lower stack 600B are hybrid-bonded at the interface A to form a complete micro-LED chip 600. The structures and components of the upper stack 600A and the lower stack 600B are described in detail below.

[0152] Upper layer

[0153] The upper stack 600A includes a first insulating layer 611A, a light emitting mesa 601, a transparent conductive layer 608, a first electrode 604 (cathode), a first via contact 602, a second electrode 610 (anode), a first bonding mark 609A, and a microlens 605. Each component is described below.

[0154] A first insulating layer 611A, which is configured to accommodate at least a portion of the light-emitting mesa 601 and provide electrical insulation therefor. Here, the first electrical insulating layer 611A has a recess 607, which is configured to accommodate the light-emitting layer and the second epitaxial layer of the light-emitting mesa 601 and the auxiliary structure of the light-emitting mesa 601. For a detailed description of the light-emitting mesa 601 and its auxiliary structures (such as the passivation layer 612, the reflector layer 615, etc.), reference can be made to the light-emitting mesa 601 and its description. Here, it should be noted that the recess 607 can be formed after the light-emitting mesa 601, that is, the light-emitting mesa 601 and its auxiliary structures are first formed on the temporary substrate, and then the first insulating layer 611A surrounding them is formed on the light-emitting mesa 601 and its auxiliary structures. The material of the first insulating layer 611A can be, for example, silicon dioxide, silicon nitride, a high dielectric constant material (such as hafnium oxide, aluminum oxide, etc.), etc. The first insulating layer 611A can be formed by thermal oxidation, chemical vapor deposition (CVD), etc. The thickness of the first insulating layer 611A is, for example, 1 to 3 μm, preferably 2 μm, and more preferably 0.6 to 1.4 μm. In addition, the first insulating layer 611A may be planarized at the interface A (eg, by chemical mechanical polishing (CMP)) to facilitate hybrid bonding with the second insulating layer 611B.

[0155] The first insulating layer 611A is transparent to the light emitted from the light emitting mesa 601. In some embodiments, the first insulating layer 611A is made of a dielectric material such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes silicon dioxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon carbonitride (SiCN), hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), zirconium oxide (ZrO2), lanthanum oxide (La2O3), magnesium oxide (MgO), phospho-silicate glass (PSG), boro-phospho-silicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes a polymer such as SU-8, PermiNex, benzocyclobutene (BCB), or a transparent plastic (resin) including spin-on glass (SOG), or an adhesive microresist BCL-1200, or any combination thereof. In some embodiments, the first insulating layer 611A can facilitate the passage of light emitted from the light-emitting mesa 601. In some embodiments, the first insulating layer 611A can include multiple parts, such as three embedded dielectric parts and two bonding dielectric parts. The embedded dielectric part refers to the dielectric layer surrounding each light-emitting diode structure; and the bonding dielectric part refers to the dielectric layer between two light-emitting diode structures. The embedded dielectric part and the bonding dielectric part may have the same or different compositions.

[0156] A light-emitting mesa 601, which is configured to emit light, wherein the area of ​​the top surface (i.e., the upper surface) of the light-emitting mesa 01 is larger than the area of ​​the bottom surface (i.e., the lower surface) of the light-emitting mesa, and is in an "inverted trapezoidal" shape. The inclination angle of the light-emitting mesa 601 can be, for example, 10° to 85°, preferably 30° to 70°, and especially 35° to 50°. The light-emitting mesa 601 includes a first epitaxial layer 601A, a light-emitting layer 601B, and a second epitaxial layer 601C, wherein the first epitaxial layer 601A is arranged on the top or upper surface of the light-emitting mesa, that is, on the side facing the light-emitting surface, the light-emitting layer 601B is arranged in the recess 607 and arranged between the first epitaxial layer 601A and the second epitaxial layer 601C, and the second epitaxial layer 601C is arranged on the bottom or lower surface of the light-emitting mesa 601, that is, on the side facing the driving backplane 606. The light-emitting layer 601B, for example, includes a multi-quantum well layer and an electron blocking layer. In one embodiment of the present invention, the first epitaxial layer 601A is an N-type GaN layer or an N-type AlGaN layer, and the second epitaxial layer 601C is a P-type GaN layer or a P-type AlGaN layer, that is, the material of the second epitaxial layer 601C can be a material layer of the second conductivity type including two or more elements of Ga, N, As, Al, In, and P, and the first epitaxial layer 601A can be a material layer of the first conductivity type including two or more elements of Ga, N, As, Al, In, and P. The multi-quantum well layer is an InGaN / GaN multi-quantum well layer or an InGaN / AlGaN multi-quantum well layer or an InGaAs / AlGaAs multi-quantum well layer. The electron blocking side is arranged on the first side of the light-emitting layer, and the first side refers to the side along which the electrons migrate out of the light-emitting layer. In another embodiment of the present invention, the first epitaxial layer can also be a P-type GaN layer or a P-type AlGaN layer, and the second epitaxial layer can be an N-type GaN layer or an N-type AlGaN layer. The top width of the light-emitting mesa 601 is, for example, 0.5 to 3 μm, preferably 1.0 to 2.0 μm. The thickness of the first epitaxial layer 601A is, for example, 4000 to 5000 angstroms, the thickness of the light-emitting layer 601B is, for example, 3500 to 4000 angstroms, and the thickness of the second epitaxial layer 601C is, for example, 2500 to 3500 angstroms. 1 angstrom = 10^(-10) meters. Figure 3It can be seen that the first epitaxial layer 601A is located outside the recess 607, while the light-emitting layer 601B and the second epitaxial layer 601C are located inside the recess 607. In this way, the surface area of ​​the first epitaxial layer 601A is not limited by the opening area of ​​the recess 607, but can be significantly larger than the opening area of ​​the recess 607, thereby significantly increasing the area and thickness of the first epitaxial layer 601A; in addition, since the recess 607 only needs to accommodate the light-emitting layer 601B and the second epitaxial layer 601C, these two layers have a larger area and thickness compared with the structure of the prior art that needs to accommodate three layers, thereby better increasing the area and thickness of the epitaxial layer 601 and improving the light emission. It can also be seen here that the first epitaxial layer 601A passes through the first electrode 604 from below the first electrode 604 (here, the cathode), so that the first epitaxial layers 601A of adjacent light-emitting mesas 601 can be connected to each other, so that in the case of a common cathode structure (i.e., the first epitaxial layers of all micro-LEDs in the same array are connected to a common cathode), the conductivity between the cathode 604 and the first epitaxial layer 601A can be significantly enhanced compared to the case where the cathode 604 is connected only by the transparent conductive layer 608 covering it, thereby increasing its power supply. In addition, the contact cross section between the first epitaxial layer 601A and the cathode 604 at the edge is partially flat and partially inclined. Compared with the vertical surface, the inclined surface increases the contact area between the first epitaxial layer 601A and the cathode 604, thereby increasing the conductivity.

[0157] The light-emitting mesa 601 further includes auxiliary structures such as passivation layers 612 and 613, a reflector layer 615, a bottom transparent conductive layer 618, etc. The passivation layer 612 is arranged between the light-emitting mesa 601 and the reflector layer 615, and optionally extends on the upper surface of the first insulating layer 611A, while the passivation layer 613 is arranged between the inner wall of the recess 607 and the reflector layer 615, and optionally extends on the upper surface of the first insulating layer 611A. In another embodiment, only one of the passivation layers 612 and 613 extends on the upper surface of the first insulating layer 611A, or both of them do not extend on the upper surface of the first insulating layer 611A, instead, they only extend to the upper surface of the first insulating layer 611A, and the upper surface of the first insulating layer 611A is covered by another insulating layer or a dielectric layer. The passivation layers 612 and 613 not only reduce the current leakage at the sidewall, but also passivate the sidewall defects, prevent water, oxygen, etc. from damaging the light-emitting mesa during operation, and prevent the metal in the reflector layer 615, cathode 604, etc. from diffusing into the first insulating layer 611 or the light-emitting mesa 601. The passivation layers 612 and 613 can be formed by depositing SiO2 material using a CVD process, or by depositing Al2O3 material using an ALD process. The bottom transparent conductive layer 618 is arranged between the second epitaxial layer 601C and the reflector layer 615. The bottom transparent conductive layer 618 is configured to electrically connect the second epitaxial layer 601C of the light-emitting mesa 601 to the reflector layer 615 and further to the through-hole contact 602. The material of the bottom transparent conductive layer 618 is, for example, metal oxide, such as indium tin oxide ITO, zinc oxide ZnO, etc., and its formation method includes, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), sol-gel method, solution coating method, etc.

[0158] The reflector layer 615 is configured to reflect upward the light from the light emitting mesa 601. To this end, the reflector layer 615 has an inclined surface on the side facing the light emitting mesa 601, and its inclination angle is, for example, the same as the inclination angle of the light emitting mesa, which is 10° to 85°, preferably 30° to 70°, and especially 35° to 50°.

[0159] Here, the reflector layer 615 includes a side reflector layer 615A, a bottom reflector layer 615B, and an edge portion 615C, wherein the side reflector layer 615A and the bottom reflector layer 615B constitute the main body of the reflector layer 615. The side reflector layer 615A covers at least a portion of the side surface of the light-emitting mesa 601. Both the side reflector layer 615A and the bottom reflector layer 615B are configured to reflect light from the light-emitting mesa 601 upward, and the bottom reflector layer 615B is also configured to electrically connect the bottom transparent conductive layer 618 to the first through-hole contact portion 602. In this embodiment, the side reflector layer 615 covers the side surface of the light-emitting mesa 601 in the recess 607, and the side reflector layer 615 is formed between the passivation layer 612 and the inner wall of the recess 607 of the insulating layer. Due to the presence of the passivation layer 612, the side reflector 615 may or may not have an atomic layer deposition layer on the side facing the light-emitting mesa 601. In the case of having an atomic layer deposition layer, the metal in the reflector layer 615 can be further prevented from penetrating into the light-emitting mesa 601 through the passivation layer 612. The side reflector layer 615A has an inclined surface on the side facing the light-emitting mesa 601 to reflect the light from the light-emitting mesa upward, and its inclination angle is, for example, the same as the inclination angle of the light-emitting mesa 601, which is 10° to 85°, preferably 30° to 70°, and especially 35° to 50°. The bottom reflector layer 615B covers at least a portion of the bottom surface of the light-emitting mesa 601. In this embodiment, the bottom reflector 615B covers the bottom transparent conductive layer 618 of the light-emitting mesa 601. The bottom reflector layer 615B has an atomic layer deposition layer on the side facing the light-emitting mesa 601. The atomic layer deposition layer can block the metal from the reflective metal layer to prevent its diffusion without substantially affecting the reflection of light.

[0160] from Figure 5 It can be seen that the edge portions 615C of the reflector layer 615 are disconnected from each other between adjacent light-emitting mesas 601 to prevent short circuits. At the same time, the edge of the reflector layer 615 also has an edge portion 615C that is bent or inclined toward the lower surface of the light-emitting mesas, so that the edge of the reflector layer 615 can be away from the conductive structure, such as the epitaxial layer, on the upper surface of the light-emitting mesas 615, reducing the risk of short circuits. In other words, such a setting reduces the area of ​​the edge portion 615C of the reflector layer 615 exposed from the insulating layer 611A surrounding the light-emitting mesas 601, and at the same time ensures that the reflector layer 102 has sufficient thickness at the upper surface A of the light-emitting mesas 101, ensuring sufficient coverage at the edge and improving the edge coverage quality.

[0161] The reflector layer 200 includes an atomic layer deposition layer 201, a reflective metal layer 202, a first barrier layer 203, and a second barrier layer 204 from top to bottom (i.e., from facing the light-emitting mesa 601 to facing away from the light-emitting mesa 601), wherein the upper side of the reflector layer 200 faces the light-emitting mesa or epitaxial layer of the micro-light-emitting diode, and the lower side of the reflector layer 200 faces away from the light-emitting mesa or epitaxial layer of the micro-light-emitting diode or faces the bottom transparent conductive layer.

[0162] For example, the stacked structure of the reflector layer 615 is as follows (in order from close to the light-emitting mesa to far away from the light-emitting mesa):

[0163] Atomic layer deposition layer 201, made of nickel, with a thickness of 5 angstroms;

[0164] The reflective metal layer 202 is made of silver and has a thickness of 1000 angstroms;

[0165] The first and second barrier layers 203A and 203B are made of titanium and platinum, respectively, and have thicknesses of 200 and 500 angstroms, respectively;

[0166] The second barrier layer 204 is made of titanium and has a thickness of 200 angstroms.

[0167] In addition, the number of layers of the first barrier layer 203 is three.

[0168] The reflector layer 615 can be formed, for example, by evaporation, sputtering, chemical vapor deposition (CVD), etc., wherein the atomic layer deposition layer 201 of the reflector layer 615 is formed by atomic layer deposition. The thickness of the passivation layer 612 between the reflector layer 612 and the light-emitting mesa 601 is 800 to 2000 angstroms, preferably 1000 to 1600 angstroms. The thickness of the passivation layer 613 between the reflector layer 615 and the inner wall of the recess 607 is 200 to 800 angstroms, preferably 300 to 600 angstroms.

[0169] A top transparent conductive layer 608, which is arranged on the first epitaxial layer 601A and electrically connects the first electrode 604 (cathode) to the first epitaxial layer 601A. Here, the top transparent conductive layer 608 extends on the first epitaxial layer 601A and completely covers the first epitaxial layer 601A, thereby providing a more uniform power supply for the first epitaxial layer 601A. In other embodiments, the top transparent conductive layer 608 may also only partially cover the first epitaxial layer 601A. In addition, the top transparent conductive layer 608 also extends under the first electrode 604, which is the cathode in this case, so that the transparent conductive layer 608 extends continuously on the first epitaxial layer 601A of the adjacent light-emitting mesa 601A, thereby increasing the coverage area of ​​the first epitaxial layer 601A. The material of the top transparent conductive layer 608 is, for example, a metal oxide, such as indium tin oxide ITO, zinc oxide ZnO, etc., and its formation method includes, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), sol-gel method, solution coating method, etc.

[0170] The first electrode 604, here a cathode, is arranged to surround the light-emitting mesa 604. The cathode 604 and its connecting parts can be made of materials such as metal (such as copper, silver or aluminum), graphene, ITO, aluminum-doped zinc oxide (AZO) or fluorine-doped tin oxide (FTO) or any combination of the above materials. In another embodiment of the present invention, the cathode 604 and its connecting parts can be made of non-transparent or transparent conductive materials, such as indium tin oxide (ITO). In a preferred embodiment, the cathode 604 is made of a reflective metal (such as copper, silver or aluminum), so that the cathode 604 can reflect light from the light-emitting mesa 601 while optically isolating adjacent light-emitting mesas 601 from each other, for example, reflecting the light upward to the microlens 605, thereby increasing the light output. In another embodiment, a reflective layer, such as a silver layer, can be coated on the surface of the cathode 604 to provide a reflective capability. Here, the surface of the cathode 604 facing the light-emitting mesa 601A is an inclined surface, and is inclined toward both sides (i.e., inclined toward both sides starting from the bottom surface), so that the light falling thereon can be reflected upward, i.e., toward the light-emitting side. In addition, the cathode 604 can be divided into an edge cathode 604A and a middle cathode 604B, wherein the edge cathode 604A is arranged between the second electrode 610 (which is the anode) and the edgemost light-emitting mesa 601, wherein a part of the edge cathode 604A is arranged on the passivation layer 612, and another part is arranged on the transparent conductive layer 608, and the middle cathode 604B is arranged between adjacent light-emitting mesas 601, wherein the middle cathode 604B is arranged on the transparent conductive layer 608. In this way, the edge cathode 604A can completely cover the side of the first epitaxial layer 601A and be in electrical contact with it, thereby increasing the electrical contact area between the cathode 604 and the first epitaxial layer 601A.

[0171] A first through-hole contact 602, which is electrically connected to the bottom of the light-emitting mesa 601 and passes through the first insulating layer 611A. The first through-hole contact 602 is used for hybrid bonding with the second through-hole contact 603, and thereby electrically connects the bottom of the light-emitting mesa 601, especially the second epitaxial layer 601C, to the second electrode 610 (here, the anode). The first through-hole contact 602 is preferably a cylindrical through-hole, and the inner wall and / or the middle space are filled with a conductor, such as metal copper. The diameter of the first through-hole contact 602 is 0.3 to 2 μm, preferably 0.6 to 1.4 μm. The first through-hole contact 602 can be planarized at the interface A (for example, by chemical mechanical polishing CMP) to facilitate hybrid bonding with the second through-hole contact 603. In addition, in order to promote the bonding strength between the first through-hole contact 602 and the second through-hole contact 603 and improve the conductivity, a first interface metal layer may be arranged at the first opening of the first through-hole contact 602, and the area of ​​the first interface metal layer is larger than the area of ​​the first opening. Similarly, a second interface metal layer may be arranged at the second opening of the second through-hole contact, and the area of ​​the second interface metal layer is larger than the area of ​​the second opening. The areas of the first interface metal layer and the second interface metal layer may be equal, or the area of ​​the first interface metal layer may be larger than or smaller than the area of ​​the second interface metal layer. When the first interface metal layer and the second interface metal layer 202 are bonded to each other, the bonding surface formed is larger than the bonding surface formed by directly bonding the first opening of the first through-hole contact 602 and the second opening 204 of the second through-hole contact 603, thereby increasing the bonding strength and improving the conductivity between the first through-hole contact 602 and the second through-hole contact 603. The first interface metal layer 201 and the second interface metal layer 202 are made of, for example, a conductive metal, such as copper. The formation method thereof may include, for example, physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, chemical plating, etc. The formation method of the first through-hole contact portion 603 may be, for example, as follows: a light-emitting mesa 601 and a first insulating layer 611A are formed on a temporary substrate, and then the first insulating layer 611A is etched to form a through hole leading to the bottom of the light-emitting mesa 601, and then a metal is deposited in the through hole, and finally the opening of the through hole is planarized to form a bonding surface.

[0172] In addition, the first through-hole contact 602 is used to electrically connect the driving circuit 606 to the bottom (here, the reflector layer 607) of the epitaxial layer 601 (or the light-emitting mesa) of the micro-LED array after bonding with the second through-hole contact 603, thereby connecting the epitaxial layer 601 to the anode 610. Here, a first metal barrier layer 617 is provided between the through-hole contact 602 and the reflector layer 607. The first metal barrier layer 617 can prevent the metal in the first through-hole contact 602 from diffusing into the epitaxial layer 601 or the insulating layer 611A or preventing it from being oxidized through the reflector layer 607 and other layers that may be arranged therebetween (e.g., the bottom transparent electrode layer). If the metal in the first through-hole contact 602 diffuses into the epitaxial layer 601, the light-emitting performance of the epitaxial layer 601 will be affected; if it diffuses into the insulating layer 611A, it will affect the insulating effect of the insulating layer 611A, thereby causing leakage current or even short circuit; if the metal in the through-hole contact 602 is oxidized, it may cause poor contact between the first through-hole contact 602 and the reflector layer 607, or even cause the electrical circuit to the epitaxial layer 601 to be broken. It can be seen that by providing the first through-hole contact 602 according to the present invention, the diffusion of the metal in the first through-hole contact 602 can be better avoided, thereby effectively preventing the risks of reduced light-emitting performance, short circuit, and open circuit of the micro-LED. The combination of the first metal barrier layer 617 and the first and second barrier layers 203 and 204 of the reflector layer can further enhance the metal barrier and anti-oxidation effects.

[0173] The second electrode 610, which is an anode in this case, is electrically connected to the driving backplane 606 through a third through-hole contact 614 that passes through the first insulating layer 611A and the second insulating layer 611B. The anode 610 can be connected to an external power source or a control source, for example, to power or control the micro-LED chip 600. Here, the third through-hole contact 614 can include a plurality of through-hole contacts, so as to connect the second epitaxial layer 601C of the plurality of light-emitting mesas to the anode 610. Here, it is exemplarily shown that the third through-hole contact 614 includes two through-hole contacts, but this is merely exemplary, and other numbers of through-hole contacts 614 are also conceivable. The third through-hole contact 614 can be formed either before or after hybrid bonding. If the third through-hole contact 614 is formed before hybrid bonding, the upper and lower parts of the third through-hole contact 614 are first formed in the upper stack 600A and the lower stack 600B, respectively, and then the two are connected to form the third through-hole contact after hybrid bonding, and then the first insulating layer 611A is etched from above to form the anode 610 on the third through-hole contact 614. If the third through-hole contact 614 is formed after hybrid bonding, the first insulating layer 611A is etched from above to form a through hole leading to the driving backplane 606, and then metal is deposited in the through hole, and then the third through-hole contact 614 is etched to form a recess, and then metal is deposited in the recess to form the anode 610. The anode 610 and its connecting parts can be made of materials such as metal (such as copper, silver or aluminum), graphene, ITO, aluminum-doped zinc oxide (AZO) or fluorine-doped tin oxide (FTO) or any combination of the above materials.

[0174] · A first bonding mark 609A, which is disposed in the first insulating layer 611A and exposes a first mark surface, i.e., an opening of the first bonding mark. The first bonding mark 609A in the upper stack 600A serves as a mark for alignment with the second bonding mark 609B in the lower stack 600B, thereby achieving precise hybrid bonding, wherein the second bonding mark 609B is disposed in the second insulating layer 600B and exposes a second mark surface, i.e., an opening of the second bonding mark. The first bonding mark 609A and the second bonding mark 609B are aligned in such a way that, during hybrid bonding, the first mark surface is aligned and attached to the second mark surface, at which point the upper stack 600A and the lower stack 600B are aligned, and then hybrid bonding can be performed. The first bonding mark 609A and the second bonding mark 609B can be metal vias, and the two can be bonded at the interface. In addition, the first bonding mark 609A and the second bonding mark 609B may have enlarged openings and / or the openings may be coated with a metal layer to facilitate identification of their positions and increase bonding strength.

[0175] A microlens 605 is disposed above the light-emitting mesa 601 to shape the light emitted therefrom, such as converging or collimating. The microlens includes a lens portion 605A and a spacer portion 605B. The lens portion 605A is disposed at the outermost side, i.e., the uppermost side, and is configured to shape the light from the light-emitting mesa 601. The spacer portion 605B is disposed between the lens portion 605A and the light-emitting mesa 601 to adjust the focal position of the lens portion 605A. For example, the focal point of the lens portion 605A can be exactly located in the light-emitting mesa 601 of the micro-LED by adjusting the thickness of the spacer portion 605B and the curvature of the lens portion 605A. The width of the microlens 605 is, for example, 0.8 to 4 μm, preferably 1 to 3 μm. The distance between the lens portion 605A and the cathode 604 is, for example, 0.05 to 4 μm, preferably 0.1 to 0.3 μm. The microlens 605 corresponds to the light-emitting mesa 601 one by one. Meanwhile, in this embodiment, there is a gap between adjacent microlenses 605 and the bottoms thereof are connected to each other. The bottom of the gap is higher than the top of the light-emitting mesa 601, or higher than the bottom of the light-emitting layer 601B of the light-emitting mesa 601, and the lens portion 604A is located above the cathode 604. The microlenses 605 can be formed by multiple depositions. In the process of forming the microlenses, a SiO2 film layer needs to be deposited first, and then ion etching is performed. The microlenses are formed on the surface of the transparent conductive layer 608 at positions corresponding to each light-emitting mesa 601.

[0176] Lower stack

[0177] The lower stack 600B includes a second insulating layer 611B, a second through-hole contact 603, a driving back plate 606, and a second bonding mark 609B. Each component is described below.

[0178] A second insulating layer 611B is arranged on the driving backplate 606 and is configured to accommodate the second through-hole contact 603. The material of the second insulating layer 611B can be, for example, silicon dioxide, silicon nitride, a high dielectric constant material (such as hafnium oxide, aluminum oxide, etc.), etc. The second insulating layer 611B can be formed on the driving backplate 606 by, for example, thermal oxidation, chemical vapor deposition (CVD), etc. The thickness of the second insulating layer 611B is, for example, 1 to 3 μm, preferably 2 μm, and more preferably 0.6 to 1.4 μm. In addition, the second insulating layer 611B can be planarized at the interface A (for example, by chemical mechanical polishing CMP) to promote hybrid bonding with the first insulating layer 611A.

[0179] The second insulating layer 611B may be transparent to the light emitted from the light emitting mesa 601. In some embodiments, the second insulating layer 611B is made of a dielectric material such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes silicon dioxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon carbonitride (SiCN), hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), zirconium oxide (ZrO2), lanthanum oxide (La2O3), magnesium oxide (MgO), phospho-silicate glass (PSG), boro-phospho-silicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes a polymer such as SU-8, PermiNex, benzocyclobutene (BCB), or a transparent plastic (resin) including spin-on glass (SOG), or an adhesive microresist BCL-1200, or any combination thereof. In some embodiments, the second insulating layer 611B can facilitate the passage of light emitted from the light-emitting mesa 601. In some embodiments, the second insulating layer 611B can include multiple parts, such as three embedded dielectric parts and two bonding dielectric parts. The embedded dielectric part refers to the dielectric layer surrounding each light-emitting diode structure; and the bonding dielectric part refers to the dielectric layer between two light-emitting diode structures. The embedded dielectric part and the bonding dielectric part may have the same or different compositions.

[0180] A second via contact 603, which passes through the second insulating layer 611B. The second via contact 603 is configured to be hybrid bonded with the first via contact 602 at the interface A, and thereby electrically connects the bottom of the light-emitting mesa 601, especially the second epitaxial layer 601C, to the second electrode 610 (here, the anode). The second via contact 603 is preferably a cylindrical through-hole, and the inner wall and / or the intermediate space are filled with a conductor, such as metal copper. The diameter of the second via contact 603 is 0.5 to 2.2 μm, preferably 0.8 to 1.6 μm. The second via contact 603 can be planarized at the interface A (for example, by chemical mechanical polishing CMP) to promote hybrid bonding with the first via contact 602. In addition, in order to promote the bonding strength between the second via contact 603 and the first via contact 602 and improve the conductivity, a second interface metal layer can be arranged at the second opening of the second via contact 603, and the area of ​​the second interface metal layer is larger than the area of ​​the second opening. Similarly, a first interface metal layer may be arranged at the first opening of the first through-hole contact 602, and the area of ​​the first interface metal layer is larger than the area of ​​the first opening. The areas of the first interface metal layer and the second interface metal layer may be equal, or the area of ​​the first interface metal layer may be larger than or smaller than the area of ​​the second interface metal layer. After the first interface metal layer and the second interface metal layer are bonded to each other, the bonding surface formed is larger than the bonding surface formed by directly bonding the first opening of the first through-hole contact 602 and the second opening of the second through-hole contact 603, thereby increasing the bonding strength and improving the conductivity between the first through-hole contact 602 and the second through-hole contact 603. The first interface metal layer and the second interface metal layer are, for example, made of a conductive metal, such as copper. The formation method thereof may, for example, include physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, chemical plating, and the like. The second through hole contact portion 603 may be formed, for example, as follows: providing a driving backplane 606, then forming a second insulating layer 611B on the driving backplane 606, then etching the second insulating layer 611B to form a through hole leading to the top of the driving backplane 606, then depositing metal in the through hole, and finally flattening the opening of the through hole to form a bonding surface.

[0181] In addition, the second through-hole contact 603 is used to electrically connect the driving circuit 606 to the bottom (here, the reflector layer 607) of the epitaxial layer 601 (or the light-emitting mesa) of the micro-LED array after bonding with the first through-hole contact 603, thereby connecting the epitaxial layer 601 to the anode 610. Here, a first metal barrier layer 617 is provided between the second through-hole contact 603 and the driving circuit 607. The first metal barrier layer 617 can prevent the metal in the second through-hole contact 603 from diffusing into the driving circuit 606 or the insulating layer 611B or preventing it from being oxidized. If the metal in the second through-hole contact 602 diffuses into the driving circuit 606, the electrical performance of the driving circuit will be affected, such as a short circuit; if it diffuses into the insulating layer 611B, it will affect the insulating effect of the insulating layer 611B, thereby causing leakage current or even a short circuit; if the metal in the second through-hole contact 603 is oxidized, it may cause poor contact between the second through-hole contact 603 and the driving circuit 606, or even cause the electrical line to the driving circuit 606 to be broken. It can be seen that by providing the second through-hole contact 603 according to the present invention, the diffusion of the metal in the second through-hole contact 603 can be better avoided, thereby effectively preventing the risks of short circuit, open circuit, etc. of the driving circuit 606. The combination of the first metal barrier layer 617 and the first and second barrier layers 203 and 204 of the reflector layer can further enhance the metal barrier and anti-oxidation effects.

[0182] A driving backplane 606 (or a driving circuit) is electrically connected to the second through-hole contact 603 so as to electrically connect the second epitaxial layer 601C of the light-emitting mesa 601 to the anode 610. To this end, the driving backplane 606 has a conductive circuit layer for interconnecting each second through-hole contact 603 to the corresponding anode 610. The driving backplane 606 can be, for example, a thin film transistor TFT driving circuit, and can include a 2T1C driving circuit, a 3T1C driving circuit, and a 5T2C driving circuit. The driving backplane 606 is configured to drive the micro light-emitting diode, for example, to control the connection, disconnection and brightness of the micro light-emitting diode. The driving backplane 606 can include, for example, transistors, capacitors, a conductive circuit layer, an insulating layer, and a metal layer. The conductive circuit layer is formed on the substrate and is configured to supply power to the micro light-emitting diode array. The insulating layer is formed on the conductive circuit layer, wherein the insulating layer is provided with a through hole, and the through hole is provided with a through hole contact (for example, an IC copper column) for electrically connecting the conductive circuit layer to the micro light-emitting diode array. The metal layer is used for bonding and electrical contacting of the micro light emitting diodes. The conductive line layer, the metal layer and the insulating layer may have been formed on the substrate 601 by deposition, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD).

[0183] A second bonding mark 609B, which is disposed in the second insulating layer 611B and exposes a second mark surface, i.e., an opening of the second bonding mark. The second bonding mark 609B in the lower stack 600B serves as a mark corresponding to the first bonding mark 609A in the upper stack 600A, thereby achieving precise hybrid bonding. The first bonding mark 609A and the second bonding mark 609B are aligned in such a way that, during hybrid bonding, the first mark surface is aligned and affixed to the second mark surface, at which point the upper stack 600A and the lower stack 600B are aligned, and then hybrid bonding can be performed. The first bonding mark 609A and the second bonding mark 609B can be metal through holes, and the two can be bonded at the interface. In addition, the first bonding mark 609A and the second bonding mark 609B can have an enlarged opening and / or a metal layer can be coated at the opening to facilitate identification of their positions and increase bonding strength.

[0184] After the lower stack 600A and the upper stack 600B are formed, the lower stack 600A is bonded to the upper stack 600A by hybrid bonding, so that the first through hole contact portion 602 is bonded to the second through hole contact portion 603, and the first insulating layer 611A is bonded to the second insulating layer 611B, and optionally the first bonding mark 609A is bonded to the second bonding mark 609B, and the upper and lower parts of the third through hole between the preliminary 614 are bonded to each other. The present invention solves the technical problem encountered when manufacturing an inverted trapezoidal light-emitting mesa with a large upper surface and a small lower surface, that is, the problem of electrical connection between the light-emitting mesa and the driving backplane, by separately manufacturing the upper stack 600A and the lower stack 600B and then bonding the two to each other by hybrid bonding. The present invention realizes the electrical connection from the light-emitting table 601 to the driving backplane 606 through hybrid bonding, so that the upper stack 600A and the lower stack 600B can be manufactured from the surface opposite to the hybrid bonding surface, that is, the interface A, toward the hybrid bonding surface, thereby realizing a high-quality conductive structure, such as the first to third through-hole contacts (such as IC copper pillars), and the length of the conductive structure can also be flexibly selected.

[0185] An example of a hybrid bond may include the following two parts:

[0186] (1) Dielectric-to-dielectric bonding (i.e., bonding between the first insulating layer 611A and the second insulating layer 611B): At room temperature, extremely flat and smooth dielectric surfaces obtained by chemical mechanical polishing (CMP) are activated by plasma treatment or other methods and then brought into close contact at room temperature to achieve preliminary bonding.

[0187] (2) Metal-to-metal bonding (i.e., bonding between through-hole contacts): After completing dielectric-to-dielectric bonding, the upper and lower layers are heated to 200-400°C for annealing to strengthen the dielectric bonding and promote metal-to-metal bonding, thereby achieving hybrid bonding.

[0188] Figure 6 A schematic diagram of a first embodiment of a photoresist ring 300 for forming a reflective mirror layer according to the present invention is shown.

[0189] like Figure 6 As shown, the photoresist ring 300 for forming the reflector layer according to the present invention includes an upper ring 301 and a lower ring 302. The function of the photoresist ring 300 is to act as a mold when forming the reflector layer on the light-emitting mesa 101. On the one hand, it isolates and disconnects the reflector layers of adjacent light-emitting mesas 101 from each other, and on the other hand, it shapes the reflector layer so that the reflector layer has a desired cross-sectional shape, such as a circle, a square, a rectangle, etc. The photoresist ring 300 includes an upper ring 301 and a lower ring 302, wherein the lower ring 302 is arranged to surround the light-emitting mesa 101 of the micro light-emitting diode, and the upper ring 301 is arranged on the lower ring 301, wherein at the connection between the upper ring 301 and the lower ring 302, the thickness of the upper ring 301 is greater than the thickness of the lower ring 301. For example, at the connection between the upper ring and the lower ring, the thickness of the upper ring is 20% to 60% greater than the thickness of the lower ring. Such a thickness jump is conducive to forming a suspended layer of the reflector layer at the connection portion, the suspended layer is separated from the lower ring 301, and there is a gap of the reflector layer under the suspended layer, wherein the gap allows the degumming liquid to enter and erode the bottom of the lower ring 302 during the degumming process, thereby separating the lower ring 302 from the temporary substrate 104, and the separated lower ring 302 will take away the upper ring 301 and the reflector layer covered thereon. The cleaned structure will not have the photoresist ring 300, but a well-formed reflector layer.

[0190] The height of the lower ring 302 can affect the height of the edge of the reflector layer and the height of the gap. The higher the height of the lower ring 302, the higher the edge and the higher the gap. For example, in the present embodiment, the height of the lower ring 302 is 2 / 3 of the height of the light-emitting table 101, or the height of the lower ring 302 is the same as the height of the light-emitting layer 101B of the light-emitting table 101. In this way, the height of the edge of the reflector layer formed is relatively low, so that the formed reflector layer basically corresponds to the profile of the light-emitting table, for example, a flat-topped cone. At the same time, since the lower ring 302 is relatively low, the gap formed is also relatively low, so as to facilitate the entry of the degumming liquid. The longitudinal section shape of the upper ring 301 and the lower ring 302 in the longitudinal section perpendicular to the upper surface of the light-emitting table can be a trapezoid or a triangle. Under the teachings of the present invention, other shapes can also be conceivable.

[0191] Figure 7 A schematic diagram of a second embodiment of a photoresist ring 300 for forming a reflective mirror layer according to the present invention is shown.

[0192] Figure 7The second embodiment shown is Figure 6 The first embodiment shown is basically the same, and the main difference is that in the second embodiment, the height of the lower ring 302 is set to be higher than the lower surface B of the light-emitting table. In this way, the edge portion of the formed reflector layer has substantially the same height as the light-emitting table, which can be beneficial to the cross-sectional shape of the molded reflector layer. By making the cross-sectional shape of the lower ring 302 (the upper ring 302 has the same shape when necessary) in the cross section parallel to the upper surface A of the light-emitting table 101 one of the following: triangle, square, rectangle, circle, ellipse, and n-gon, where n is an integer greater than 4, the formed reflector layer can have the same cross-sectional shape, that is, triangle, square, rectangle, circle, ellipse, and n-gon. Preferably, the cross-sectional shape of the lower ring 301 (and the upper ring 302 when necessary) is a square, and the square has rounded inner corners, so that the formed reflector layer has a square cross-sectional shape, and the square has rounded outer corners.

[0193] Figure 8 FIG. 1 is a schematic top view of a method for forming a reflector layer 102 according to the present invention.

[0194] like Figure 8 As shown, the reflector layer 102 according to the present invention surrounds the light-emitting mesa 101 and has a rounded square cross-sectional shape. This can be achieved, for example, by making the photoresist ring of the reflector layer have a square cross-sectional shape with rounded inner corners, and the bottom of the upper ring is flush with or higher than the lower surface of the light-emitting mesa. By analogy, by making the photoresist ring of the reflector layer have other cross-sectional shapes, and the bottom of the upper ring is flush with or higher than the lower surface of the light-emitting mesa, a reflector layer with the other cross-sectional shape can be formed.

[0195] Figures 9A to 9D The steps of a method of forming a mirror layer are shown.

[0196] like Fig. 9A As shown, in step S1, a lower ring 302 is formed around the light-emitting mesa 101. This can be achieved by coating a photoresist and then exposing and developing it.

[0197] like Fig. 9B As shown, in step S2, an upper ring 301 is formed on the lower layer 302, wherein at the connection portion 303 between the upper ring 301 and the lower ring 302, the thickness of the upper ring 301 is greater than the thickness of the lower ring 301. This can be achieved by coating a photoresist and exposing and developing.

[0198] like Fig. 9CAs shown, in step S3, a reflector layer 304 is coated on the light-emitting table 101, the upper ring 301 and the lower ring 302, wherein the reflector layer 304 forms a suspended layer 305 separated from the lower ring 302 at the connection portion 303, and the lower ring 302 has a gap 306 under the suspended layer 305 that is not covered by the reflector layer 304. The existence of the suspended layer is caused by the thickness difference between the upper ring 301 and the lower ring 302 at the connection portion 303, because the thickness difference causes the reflector layer 304 to be unable to attach to the lower ring 302 during the downward flow, but to form a suspended layer 305. Due to the effect of gravity, the suspended layer 305 can only support a certain length, and it will break when it exceeds the length, thereby forming a gap 306. The gap 306 allows the degumming liquid to enter the root of the lower ring 302 during the degumming process, so that the lower ring 302 can be reliably removed by the degumming liquid, and the upper ring 301 on the lower ring 302 and the reflector layer 304 attached thereto can be removed at the same time, thereby achieving complete removal of the photoresist ring.

[0199] like Fig.9D As shown, in step S4, the upper ring 301 and the lower ring 302 are removed. The process is to apply a degumming liquid so that the degumming liquid enters the root of the lower ring 302. After a certain period of time, the degumming liquid dissolves the lower ring 302 and enables it to be removed during the washing process. At the same time, the upper ring 301 on the lower ring 302 and the reflector layer 304 attached thereto can also be removed. Fig.9D As can be seen in FIG. 3 , after the debonding step, the reflector layer 304 has a main body portion 304A and an edge portion 304B.

[0200] Although some embodiments of the present invention have been described in this application document, it will be appreciated by those skilled in the art that these embodiments are merely shown as examples. Those skilled in the art may conceive of numerous variations, alternatives, and improvements under the teachings of the present invention without departing from the scope of the present invention. The appended claims are intended to define the scope of the present invention and thus cover methods and structures within the scope of these claims themselves and their equivalents.

Claims

1. A reflector layer for a micro light emitting diode, wherein the reflector layer reflects light from a light emitting surface toward a light emitting side, and the area of ​​the upper surface of the light emitting surface facing the light emitting side is larger than the area of ​​the lower surface facing away from the light emitting side, wherein the reflector layer comprises: A main body portion, covering the lower surface of the light-emitting table and surrounding the side surfaces of the light-emitting table; as well as The edge portion is connected to the edge of the main body portion and forms an angle greater than 0° with the main body portion, wherein the edge portions of the reflector layers of adjacent micro-light emitting diodes are disconnected from each other. 2 . The reflector layer according to claim 1 , wherein the angle ranges from 5° to 85°.

3. The reflector layer according to claim 1, wherein: The edge portion has a length of 0.1 to 0.2 μm and a thickness of 0.2 to 0.4 μm; and / or The thickness of the main body is 0.2 to 0.5 μm; and / or The lowermost side of the edge portion is flush with or not flush with the lower surface of the light emitting table.

4. The reflector layer according to claim 1 , wherein a cross-sectional shape of the main body portion in a cross section parallel to the upper surface of the light-emitting mesa is one of the following: A triangle, a square, a rectangle, a circle, an ellipse, and an n-gon, wherein n is an integer greater than 4. 5 . The reflector layer according to claim 4 , wherein the cross-sectional shape of the main body is in the positive direction, and the cross-sectional shape of the light-emitting mesa is a circle, wherein the circle is an inscribed circle of the square, and the circle has rounded outer corners.

6. The reflector layer according to claim 1, wherein: The distance between the lowermost side of the connection portion between the edge portion and the main body portion and the upper surface of the light-emitting mesa is 0 to 0.8 μm; and / or The distance between the edge portions of the reflector layers of adjacent micro light emitting diodes is 0.3 to 2 μm.

7. The reflector layer according to claim 1, wherein the reflector layer comprises, starting from a side facing the light-emitting mesa: an atomic layer deposition layer, the material of which is selected from one or more of the following: nickel, platinum, titanium, and tantalum; A reflective metal layer, wherein the material of the reflective metal layer is selected from one or more of the following: silver, aluminum, and gold; A first barrier layer comprising at least first and second barrier layers, wherein the materials of the first and second barrier layers are respectively selected from one or more of the following: platinum, titanium, and tantalum; and The second barrier layer is made of a material selected from one or more of the following: platinum, titanium, and tantalum.

8. The mirror layer according to claim 7, wherein the material of the second barrier layer is the same as the material of the first barrier layer.

9. The reflector layer according to claim 7, wherein: The ALD layer material is nickel; The material of the reflective metal layer is silver; The materials of the first and second barrier layers are titanium and platinum respectively; as well as The material of the second barrier layer is titanium.

10. The reflector layer according to claim 7, wherein: The thickness of the ALD layer is 3 to 8 angstroms; The thickness of the reflective metal layer is 800 to 1200 angstroms; The first barrier layer has a thickness of 100 to 300 angstroms, and the second barrier layer has a thickness of 400 to 600 angstroms; and The second barrier layer has a thickness of 100 to 300 angstroms. 11 . The reflector layer according to claim 7 , wherein the reflector layer comprises N first barrier layers and N second barrier layers which are alternately arranged with each other, wherein N is an integer, and N=2 to 5.

12. A photoresist ring for forming a reflector layer according to any one of claims 1 to 11, wherein the photoresist ring forms the reflector layer, and the photoresist ring comprises: The lower ring surrounds the light-emitting surface of the micro-LEDs; as well as The upper ring is on the lower ring, wherein at the connection portion between the upper ring and the lower ring, the thickness of the upper ring is greater than the thickness of the lower ring. 13 . The photoresist ring according to claim 12 , wherein at a connection portion between the upper ring and the lower ring, a thickness of the upper ring is 20% to 60% greater than a thickness of the lower ring.

14. The photoresist ring according to claim 12, wherein the height of the lower ring is 2 / 3 of the height of the light-emitting mesa; or The height of the lower ring is the same as the height of the light-emitting layer of the light-emitting mesa.

15. The photoresist ring according to claim 12, wherein: The height of the lower ring is 0.2 to 0.5 μm and the height of the upper ring is 1.3 to 1.7 μm; and / or The thickness of the lower ring is 1.9 to 2.4 μm, and the thickness of the upper ring is 1.8 to 2.3 μm.

16. The photoresist ring according to claim 12, wherein a bottom of the upper ring is lower than a lower surface of the light-emitting mesa, and a top of the upper ring is higher than the lower surface of the light-emitting mesa.

17. The photoresist ring according to claim 12, wherein: The cross-sectional shape of the upper ring and / or the lower ring in the cross section parallel to the upper surface of the light-emitting mesa is one of the following: a triangle, a square, a rectangle, a circle, an ellipse, and an n-gon, wherein n is an integer greater than 4; and / or The shape of the longitudinal section of the upper ring and / or the lower ring in the longitudinal section perpendicular to the upper surface of the light-emitting mesa is one of the following: a trapezoid, a triangle. 18 . The photoresist ring according to claim 17 , wherein the cross-sectional shapes of the upper ring and the lower ring are square, and the square has rounded inner corners.

19. The photoresist ring according to any one of claims 12 to 17, wherein: The lower ring has a gradually decreasing thickness in a longitudinal section perpendicular to the upper surface of the light-emitting mesa; and The upper ring has a gradually decreasing thickness in a longitudinal section perpendicular to the upper surface of the light-emitting mesa.

20. A micro light emitting diode chip, comprising: Illuminated countertop, including: A transparent conductive layer, on the side of the light-emitting surface facing away from the light-emitting side; A first epitaxial layer, between the transparent conductive layer and the light emitting layer; a light emitting layer between the first epitaxial layer and the second epitaxial layer; and A second epitaxial layer, on a side of the light-emitting mesa facing the light-emitting side, wherein the area of ​​the second epitaxial layer is larger than the area of ​​the first epitaxial layer; The reflector layer according to claim 1, surrounding the light-emitting table; an insulating layer accommodating the light-emitting mesa and the through-hole contact; A driving circuit having a metal layer, a plurality of through-hole contacts being arranged on the driving circuit, the through-hole contacts being electrically connected to the metal layer, the micro-LED array region being bonded to the driving circuit through a bottom conductive bonding layer, wherein the driving circuit further has a wiring stack under the metal layer, leading out a first electrode; a first electrode electrically connected to the through-hole contact portion; a passivation layer covering at least a portion of a side surface of the light-emitting mesa; a top transparent conductive layer, which is located on a surface of the passivation layer and is in electrical contact with the second epitaxial layer; and The second electrode is located on the surface of the transparent conductive layer. 21 . The micro light emitting diode chip according to claim 20 , wherein the second electrode is a ring-shaped reflective electrode, which is arranged around the light emitting mesa.

22. The micro light emitting diode chip according to claim 20, wherein the polarity of the second electrode is opposite to that of the first electrode.

23. A micro-light emitting diode chip according to claim 20, wherein the material of the second epitaxial layer is a material layer of the second conductivity type comprising two or more elements of Ga, N, As, Al, In, and P, and the first epitaxial layer is a material layer of the first conductivity type comprising two or more elements of Ga, N, As, Al, In, and P, wherein the first conductivity type is different from the second conductivity type.

24. The micro-LED chip according to claim 20, wherein the light-emitting layer comprises a multi-quantum well layer, wherein the multi-quantum well layer is an InGaN / GaN multi-quantum well layer, an InGaN / AlGaN multi-quantum well layer, an InGaAs / AlGaAs multi-quantum well layer, or an AlGaInP multi-quantum well layer. 25 . The micro light emitting diode chip according to claim 24 , wherein the first side of the light emitting layer has an electron blocking layer, the first side being a side along which electrons migrate out of the light emitting layer. 26 . The micro light emitting diode chip according to claim 20 , wherein the material of the passivation layer is Si 3 N 4 film, SiO 2 film or Al 2 O 3 film.

27. The micro-LED chip according to claim 20, wherein: The material of the insulating layer is selected from one or more of the following: silicon dioxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon carbonitride (SiCN), hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), zirconium oxide (ZrO2), lanthanum oxide (La2O3), magnesium oxide (MgO), phospho-silicate glass (PSG), boro-phospho-silicate glass (BPSG), or any combination thereof; and / or The material of the metal layer is selected from one or more of the following: aluminum (Al), copper (Cu), tungsten (W), silver (Ag), gold (Au), nickel (Ni), platinum (Pt), tantalum (Ta), and molybdenum (Mo).

28. A micro-light emitting diode chip according to claim 20, wherein the through-hole contact portion includes a first and a second through-hole contact portion, and the insulating layer includes a first and a second insulating layer, and the micro-light emitting diode chip includes an upper stack and a lower stack, wherein the upper stack includes a first insulating layer, a light-emitting table and a first through-hole contact portion, and the lower stack includes a second insulating layer, a second through-hole contact portion and a driving circuit, wherein the lower stack is bonded to the upper stack so that the first through-hole contact portion is combined with the second through-hole contact portion, and the first insulating layer is combined with the second insulating layer.

29. A method for forming a reflector layer, comprising the steps of: Provide a lighted tabletop; A lower ring is formed around the light-emitting table; forming an upper ring on the lower ring, wherein at a connection portion between the upper ring and the lower ring, a thickness of the upper ring is greater than a thickness of the lower ring; Applying a reflector layer on the light-emitting mesa, the upper ring and the lower ring, wherein the reflector layer forms a suspended layer separated from the lower ring at the connecting portion, and the lower ring has a gap under the suspended layer that is not covered by the reflector layer; and Remove the upper and lower rings.

30. The method of claim 29, wherein forming a lower ring around the light-emitting mesa and forming an upper ring on the lower ring comprises the following steps: Covering the light-emitting mesa with a photoresist to form a first photoresist layer; exposing the first photoresist layer; Covering the first photoresist layer with photoresist to form a second photoresist layer; exposing the second photoresist layer; as well as The first and second photoresist layers are developed and washed to form a lower ring and an upper ring.

31. The method of claim 29, wherein removing the upper ring and the lower ring comprises: Cleaning the upper ring and the lower ring with a degumming liquid, so that the degumming liquid enters the bottom of the lower ring through the gap; Remove the lower ring by glue removal solution; as well as Remove the upper ring connected to it by removing the lower ring.

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