A full-color Micro-LED and its preparation method and display device

Abstract

The present application provides a full-color Micro-LED and its preparation method and display device. The full-color Micro-LED preparation method bonds a hollow metal layer on a monochrome Micro-LED array and sets quantum dots in the hollow metal layer. This method only uses a monochrome Micro-LED array and has a high yield rate. By using a hollow metal layer as the structural layer of the quantum dots, the metal layer is easy to hollow out. The metal acts as a separation wall between the quantum dots. On the one hand, it can prevent light crosstalk between the quantum dots. On the other hand, the metal plays a role in reflecting light, so that the light emitted by the quantum dots will not be scattered, the quantum dots emit more light, and the utilization rate of blue light is improved. This preparation method can reduce the steps and processes of flipping the quantum dots to the monochrome Micro-LED array by first bonding the hollow metal layer to the monochrome Micro-LED array and then setting the quantum dots in the hollow metal layer, making it easier to manufacture.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a full-color Micro-LED and a preparation method and a display device thereof. Background Art

[0002] Micro-LED is a miniaturized LED array structure with self-luminous display characteristics. Its technical advantages include full solid state, long life, high brightness, low power consumption, small size, ultra-high resolution, and can be used in extreme environments such as high temperature or radiation. Compared with OLED technology, which is also a self-luminous display, Micro-LED is not only more efficient and has a longer life, but also has relatively stable materials that are not easily affected by the environment, and can also avoid the generation of afterimages. For such a tiny LED chip, it is relatively complicated to achieve full color using the traditional RGB three-color array, and it is necessary to transfer a large number of Micro-LED chips, which has a low yield rate.

[0003] Quantum dots have high light absorption-luminescence efficiency, very narrow half-width, wide absorption spectrum and other characteristics, so they have high color purity and saturation, simple structure, thinness, and rollability, which are very suitable for MicroDisplay applications. However, how to combine quantum dots with Micro-LEDs is still a problem that technicians in this field need to solve, and the existing quantum dot combination methods are relatively complicated. Summary of the invention

[0004] The purpose of this application is to provide a method for preparing a full-color Micro-LED to simplify the combination of quantum dots and Micro-LED.

[0005] To achieve the above objectives, the present application provides a method for preparing a full-color Micro-LED, comprising:

[0006] Prepare a hollow metal layer, and carve a metal plate to obtain a hollow metal layer including a plurality of hollow points;

[0007] Bonding the hollow metal layer to a single-color Micro-LED array, wherein the single-color Micro-LED array includes a plurality of Micro-LED chips, so that the hollow points correspond to the Micro-LED chips respectively;

[0008] Red quantum dots and green quantum dots are arranged at the hollow points to form a plurality of light conversion units in the hollow metal layer, and each of the light conversion units includes a red quantum dot, a green quantum dot and a hollow point without a quantum dot.

[0009] Preferably, a light-blocking wall is arranged between the multiple Micro-LED chips of the monochrome Micro-LED array, and the hollow metal layer is arranged corresponding to the light-blocking wall.

[0010] Preferably, the monochrome Micro-LED array is a flip-chip monochrome Micro-LED array, and the light-blocking wall does not penetrate the surface of the monochrome Micro-LED array.

[0011] Preferably, the method for preparing the monochromatic Micro-LED array comprises:

[0012] Etching is performed on a blue LED epitaxial wafer to obtain mesas and grooves;

[0013] Depositing a light-blocking material into the groove to obtain a blue LED epitaxial wafer with a light-blocking wall;

[0014] The blue light LED epitaxial wafer with the light blocking wall is reversely soldered to obtain the monochromatic Micro-LED array.

[0015] Preferably, after etching the blue LED epitaxial wafer to obtain the mesas and grooves, the method further comprises:

[0016] depositing a current spreading layer on the mesa;

[0017] Depositing a metal layer on the current diffusion layer and the groove to form an electrode structure;

[0018] A passivation layer is deposited on the metal layer.

[0019] Preferably, the blue LED epitaxial wafer with the light-blocking wall is subjected to reverse soldering to obtain the monochromatic Micro-LED array, comprising:

[0020] Depositing a substrate on the blue LED epitaxial wafer with the light-blocking wall;

[0021] Etching the substrate on the table to etch electrode contact holes;

[0022] Metal solder joints are deposited at the electrode contact holes to obtain the single-color Micro-LED array.

[0023] Preferably, different quantum dot solutions are pressed into the hollow dots at a set speed using inkjet printing to form red quantum dots and green quantum dots.

[0024] Preferably, the printed quantum dot solution is dried or subjected to low-temperature vacuum treatment to evaporate the benign solvent in the quantum dot solution and retain the pixel-level quantum dots.

[0025] Preferably, the thickness of the metal plate is 3um to 18um.

[0026] Preferably, the metal plate is made of aluminum or gold.

[0027] The present application also provides a full-color Micro-LED, which is prepared using the above-mentioned full-color Micro-LED preparation method.

[0028] The present application also provides a display device, comprising the above-mentioned full-color Micro-LED.

[0029] Compared with the prior art, the beneficial effects of this application include:

[0030] The preparation method of full-color Micro-LED provided in the present application is used to prepare full-color Micro-LED that combines quantum dots with Micro-LED. Since only a single-color Micro-LED array is needed, there is no problem of mass transfer of multiple Micro LED chips, which can greatly improve the yield rate. At the same time, only a single-color Micro-LED array is used, and the lifespan and decay rate of each Micro-LED array are consistent, which can avoid the display color deviation caused by the different lifespans and decay rates of Micro-LEDs of different colors.

[0031] By using a hollow metal layer as the structural layer of quantum dots, the metal layer is easy to hollow out. Using metal as a separation wall between quantum dots can prevent light crosstalk between quantum dots on the one hand, and on the other hand, the metal plays a role in reflecting light, so that the light emitted by the quantum dots will not be scattered, the quantum dots emit more light, and the utilization rate of blue light is improved. By first bonding the hollow metal layer to the monochrome Micro-LED array and then setting the quantum dots in the hollow metal layer, the process steps of flipping the quantum dots to the monochrome Micro-LED array can be reduced, making it easier to manufacture.

[0032] In addition, the full-color Micro-LED quantum dots obtained by the full-color Micro-LED preparation method do not directly contact the multi-quantum hydrazine active area and the P-type layer, thereby avoiding the temperature rise of the P-type layer affecting the life of the quantum dots and avoiding the influence of the quantum dots on the performance of the multi-quantum hydrazine active area. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0034] Figure 1 It is a schematic diagram of the process of preparing a full-color Micro-LED of the present invention;

[0035] Figure 2 Schematic diagram of the preparation process of the full-color Micro-LED preparation method of the present invention;

[0036] Figure 3 It is a three-dimensional schematic diagram of the hollow metal layer of the present invention.

[0037] The accompanying drawings are marked as follows:

[0038] 100-full-color Micro-LED; 20-monochrome Micro-LED array; 22-Micro-LED chip; 1-substrate; 2-buffer layer; 3-N-type gallium nitride layer; 4-multi-quantum well active area; 5-P-type gallium nitride layer; 6-photoresist; 7-substrate; 8-metal solder joint; 9-table; 10-groove; 11-light-blocking wall; 30-hollow metal layer; 31-hollow dot; 32-red quantum dot; 33-green quantum dot; 34-protective layer. DETAILED DESCRIPTION

[0039] As used herein:

[0040] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0041] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0042] The full-color Micro-LED preparation method provided in the present application is used to prepare full-color Micro-LED. Micro-LED is a micro light emitting diode. The luminous color of the full-color Micro-LED can cover the entire visible range from blue light to red light.

[0043] This application provides a method for preparing a full-color Micro-LED. Figure 1 ,include:

[0044] S100: preparing a hollow metal layer, engraving a metal plate to obtain a hollow metal layer including a plurality of hollow points.

[0045] Specifically, the hollow metal layer is used as the structural layer of the quantum dots, and the metal plate used to carve the hollow metal layer is made of a metal with high reflectivity, such as gold or silver. The metal plate can be carved by laser printing or etching, and the carving method is simple.

[0046] The hollow metal layer includes multiple hollow points, which penetrate the upper and lower surfaces of the metal plate. The arrangement and shape of the hollow points are designed according to the arrangement and shape of the Micro-LED chips on the monochrome Micro-LED array, so that the hollow points of the hollow metal layer can be set corresponding to the Micro-LED chips. The size of the hollow points is roughly the same as the cross-sectional area of ​​the Micro-LED chip, or slightly smaller than the cross-sectional area of ​​the Micro-LED chip. Figure 3 FIG. 1 is a schematic structural diagram of an embodiment of a hollow metal layer 30 with hollow points 31 .

[0047] S200: Bonding the hollow metal layer to a monochrome Micro-LED array, where the monochrome Micro-LED array includes a plurality of Micro-LED chips, so that the hollow points correspond to the Micro-LED chips respectively.

[0048] Specifically, the monochrome Micro-LED array can be a flip-chip monochrome Micro-LED array or a face-mounted monochrome Micro-LED array. The Micro-LED chips in the monochrome Micro-LED array emit light independently. The Micro-LED chip usually includes a P-type gallium nitride region, an active region, and an N-type gallium nitride region. The light emitted from the chip active region of the face-mounted monochrome Micro-LED array is emitted through the P-type gallium nitride region and the transparent electrode; on the contrary, the light emitted from the chip active region of the flip-chip monochrome Micro-LED array is emitted through the N-type GaN region.

[0049] There may be blank areas or light-blocking walls between the multiple Micro-LED chips of a monochrome Micro-LED array. The light-blocking walls can prevent crosstalk between the light emitted by the Micro-LED chips. When light-blocking walls are set between the Micro-LED chips, the hollow metal layer is set corresponding to the light-blocking wall, the metal parts without engraving are set corresponding to the light-blocking wall, and the hollow point positions are set corresponding to the Micro-LED chips.

[0050] Preferably, the thickness of the metal plate used to prepare the hollow metal layer is 3 um to 18 um.

[0051] In one embodiment, see Figure 2 The monochrome Micro-LED array 20 is a flip-chip monochrome Micro-LED array 20, and the preparation method of the monochrome Micro-LED array 20 includes:

[0052] S10: Etching is performed on the blue light LED epitaxial wafer to obtain mesas and grooves.

[0053] Specifically, Figure 2 As shown in (a), the structure of the blue light LED epitaxial wafer includes: a substrate 1, a buffer layer 2 grown on the substrate 1, an N-type gallium nitride layer 3 grown on the buffer layer 2, a multi-quantum well active region 4 grown on the N-type gallium nitride layer 3, and this embodiment is a blue light multi-quantum well active region 4, and a P-type gallium nitride layer 5 grown on the multi-quantum well active region 4.

[0054] Specifically, the substrate 1 can be a sapphire substrate 1, the N-type gallium nitride layer 3 is obtained by doping silicon with gallium nitride, the monochrome Mirco-LED array structure leads the cathode from the N-type gallium nitride layer 3, the multi-quantum well active area 4 is grown on the N-type gallium nitride layer 3, the multi-quantum well is a system in which multiple quantum wells are combined together, and the multi-quantum well active area 4 serves as an active area to realize the light emission of the monochrome Mirco-LED array structure, the P-type gallium nitride layer 5 is obtained by doping magnesium with gallium nitride, and the monochrome Mirco-LED array structure leads the anode from the P-type gallium nitride layer 5, thereby using the P-type gallium nitride layer 5 as the anode and the N-type gallium nitride layer 3 as the cathode, which contacts the multi-quantum well active area 4 to provide a working voltage, so that the multi-quantum well active area 4 emits light.

[0055] The blue LED epitaxial wafer is cleaned with a sulfuric acid solution of H2SO4 (96%): H2O2: H2O = 5:1:1 for 10 minutes, acetone for 5 minutes, isopropanol for 5 minutes, and then deionized water and nitrogen blown dry. The surface of the cleaned blue LED epitaxial wafer is coated with photoresist 6, dried, exposed, developed, and etched to obtain a mesa 9 and a groove 10.

[0056] After obtaining the table 9 and the groove 10, the method further includes depositing a current diffusion layer (not shown in the figure) on the table 9. The current diffusion layer is deposited on the blue LED epitaxial wafer by electron beam evaporation, plasma sputtering, or thermal evaporation; the obtained wafer with the current diffusion layer deposited is immersed in an acetone solution for ultrasonic treatment for 5 minutes, and then immersed in an isopropanol solution for ultrasonic treatment for 5 minutes, and finally washed with deionized water to remove the current diffusion layer in the groove 10, leaving only the current diffusion layer on the table 9. Preferably, the current diffusion layer adopts a nickel / gold double-layer metal layer, wherein the thickness of the nickel metal layer and the gold metal layer are both set to The nickel / gold double metal layer is deposited by electron beam evaporation, and the gas flow rate can be set to: Ar: 300sccm, O2: 3sccm; the RF power can be set to 50W.

[0057] A metal layer is deposited on the current diffusion layer and the groove 10 to form an electrode structure; the material of the metal layer can be one or more of titanium, aluminum, gold, chromium, nickel, and platinum.

[0058] A passivation layer is deposited on the metal layer; the passivation layer can be made of materials such as silicon dioxide, silicon nitride, and aluminum oxide. As a specific embodiment, a silicon dioxide passivation layer is deposited by PECVD, wherein the flow rate of SiH4 is increased from 10 sccm to 20 sccm, the deposition temperature is 160°C, the deposition time is 12 minutes, and the deposition thickness is 600nm; after the deposition is completed, the wafer is placed in an oven at 120°C and baked for 30 minutes to evaporate the water vapor on the wafer.

[0059] S20: depositing a light-blocking material into the groove to obtain a blue LED epitaxial wafer with a light-blocking wall.

[0060] Specifically, Figure 2 As shown in (b), the photoresist is preferably a black photoresist, and the black photoresist is deposited in the groove 10 to form a light-blocking wall 11. The light-blocking wall 11 is arranged between the multiple Micro-LED chips 22, and does not penetrate the N-type gallium nitride layer 3 of the monochrome Micro-LED array 20. Since the N-type gallium nitride layer 3 is used to set the electrode, the light-blocking wall 11 cannot penetrate the N-type gallium nitride layer 3, otherwise the electrode structure cannot be set.

[0061] In one embodiment, the black photoresist includes: a photoresist reactant, carbon black particles, and an organic body with a molecular weight less than 1000. An organic body with a smaller molecular weight reflects less light and can improve display contrast. The size of the carbon black particles is less than 1 micron, such as 0.1 micron, 0.5 micron, etc. The black photoresist also includes a photoinitiator, a solvent, and an additive, etc., wherein the photoinitiator is used to initiate polymerization of the photoresist reactant.

[0062] S30: Perform reverse solder joints on the blue LED epitaxial wafer with the light-blocking wall to obtain a monochrome Micro-LED array.

[0063] Specifically, Figure 2 (c) and Figure 2 As shown in (d), a substrate 7 is first deposited on the blue LED epitaxial wafer with the light blocking wall 11, and then the substrate 7 on the table 9 is etched to etch out the electrode contact hole, and finally a metal solder joint 8 is deposited at the electrode contact hole. The metal solder joint 8 can be made of one or more metals such as indium, titanium, aluminum, nickel, gold, chromium, platinum, etc. Then, the substrate 1 and the buffer layer 2 are removed to obtain a monochrome Micro-LED array 20 including a plurality of Micro-LED chips 22.

[0064] like Figure 2(e) is a schematic diagram of a specific embodiment of S200. Figure 3 The hollow metal layer 30 shown is bonded to the monochrome Micro-LED array 20 prepared in S30, and the hollow points 31 correspond to the Micro-LED chips 22 respectively. In this embodiment, the hollow metal layer 30 is bonded to the surface of the monochrome Micro-LED array 20, and the height of the hollow metal layer 30 on the full-color Micro-LED 100 is greater than the height of the Micro-LED chip 22.

[0065] S300: Arranging red quantum dots and green quantum dots at the hollow points to form a plurality of light conversion units in the hollow metal layer, and each light conversion unit includes a red quantum dot, a green quantum dot and a hollow point without a quantum dot.

[0066] Specifically, after the hollow metal layer is bonded to the monochrome Micro-LED array, red quantum dots and green quantum dots are set at the hollow points. The setting rules of the red quantum dots and green quantum dots should meet the rules of the light-emitting pixel unit. The red quantum dots correspond to red light, the green quantum dots correspond to green light, and the hollow points without quantum dots correspond to blue light. One red quantum dot, one green quantum dot and one hollow point correspond to one light conversion unit. In the light conversion unit, one red quantum dot and one green quantum dot can be arranged adjacent to each other or arranged at intervals through the hollow points.

[0067] like Figure 2 (f) is a schematic diagram of a specific embodiment of S300, in which a full-color Micro-LED 100 is obtained, and red quantum dots 32 and green quantum dots 33 are arranged in the hollow points 31, so that the red quantum dots 32, the green quantum dots 33 and the hollow points 31 are arranged respectively toward the Micro-LED chip 22; the Micro-LED chip 22 at the position corresponding to the red quantum dot 32, the Micro-LED chip 22 at the position corresponding to the green quantum dot 33 and the Micro-LED chip 22 at the position corresponding to the hollow point 31 constitute a light-emitting pixel unit.

[0068] Preferably, different quantum dot solutions are pressed into the hollow points 31 at a set speed using inkjet printing to form red quantum dots 32 and green quantum dots 33. Using high-precision inkjet printing equipment, the red quantum dots 32 and green quantum dots 33 are respectively printed into the hollow points 31 of the hollow metal layer 30 to form a high-precision quantum dot color conversion layer. The inkjet printing equipment contains a nozzle alignment system and a quantum dot solution loading system.

[0069] Due to the presence of the hollow metal layer, the quantum dot solution will not diffuse disorderly due to the fluidity of the liquid. The hollow metal layer will block the diffused quantum dots, preventing the quantum dot solution droplets from diffusing, thereby limiting the quantum dot solution to a specific area, thereby eliminating the coffee ring effect caused by the dispersion of ink droplets and forming uniform quantum dot pixels.

[0070] Furthermore, the printed quantum dot pixels are dried or subjected to low-temperature vacuum treatment to evaporate the benign solvent in the quantum dot solution and retain the quantum dots at the pixel level.

[0071] For further information, see Figure 2 (f) After the quantum dots are printed at the hollow points 31 , a thin sapphire sheet may be bonded on the surface of the hollow metal layer 30 to block water and oxygen and serve as a protective layer 34 .

[0072] The preparation method of full-color Micro-LED provided in the present application is used to prepare full-color Micro-LED that combines quantum dots with Micro-LED. Since only a single-color Micro-LED array is needed, there is no problem of mass transfer of multiple Micro LED chips, which can greatly improve the yield rate. At the same time, only a single-color Micro-LED array is used, and the lifespan and decay rate of each Micro-LED array are consistent, which can avoid the display color deviation caused by the different lifespans and decay rates of Micro-LEDs of different colors.

[0073] By using a hollow metal layer as the structural layer of quantum dots, the metal layer is easy to hollow out. Using metal as a separation wall between quantum dots can prevent light crosstalk between quantum dots on the one hand, and on the other hand, the metal plays a role in reflecting light, so that the light emitted by the quantum dots will not be scattered, the quantum dots emit more light, and the utilization rate of blue light is improved. By first bonding the hollow metal layer to the monochrome Micro-LED array and then setting the quantum dots in the hollow metal layer, the process steps of flipping the quantum dots to the monochrome Micro-LED array can be reduced, making it easier to manufacture.

[0074] In addition, the full-color Micro-LED quantum dots obtained by the full-color Micro-LED preparation method do not directly contact the multi-quantum hydrazine active area and the P-type layer, thereby avoiding the temperature rise of the P-type layer affecting the life of the quantum dots and avoiding the influence of the quantum dots on the performance of the multi-quantum hydrazine active area.

[0075] The present application also provides a full-color Micro-LED, which is prepared using the above-mentioned full-color Micro-LED preparation method.

[0076] The present application also provides a display device, comprising the above-mentioned full-color Micro-LED.

[0077] The display device may be, for example, a display screen applied to an electronic device, which may include: a smart phone, a smart watch, a laptop computer, a tablet computer, a driving recorder, a navigator, or any other device with a display screen.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0079] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a full-color Micro-LED, characterized in that: include: Prepare a hollow metal layer, and use laser printing to engrave a metal plate, wherein the thickness of the metal plate is 3um to 18um, to obtain a hollow metal layer including a plurality of hollow points; Bonding the hollow metal layer to a single-color Micro-LED array, wherein the single-color Micro-LED array includes a plurality of Micro-LED chips, so that the hollow points correspond to the Micro-LED chips respectively; Arranging red quantum dots and green quantum dots at the hollow points to form a plurality of light conversion units in the hollow metal layer, and each of the light conversion units includes a red quantum dot, a green quantum dot and a hollow point without a quantum dot; A light-blocking wall is arranged between the multiple Micro-LED chips of the monochromatic Micro-LED array, and the hollow metal layer is arranged corresponding to the light-blocking wall; The monochrome Micro-LED array is a flip-chip monochrome Micro-LED array, and the light-blocking wall does not penetrate the surface of the monochrome Micro-LED array.

2. The preparation method according to claim 1, characterized in that: The method for preparing the monochromatic Micro-LED array comprises: Etching is performed on a blue LED epitaxial wafer to obtain mesas and grooves; Depositing a light-blocking material into the groove to obtain a blue LED epitaxial wafer with a light-blocking wall; The blue light LED epitaxial wafer with the light blocking wall is reversely soldered to obtain the monochromatic Micro-LED array.

3. The preparation method according to claim 2, characterized in that: After the blue light LED epitaxial wafer is etched to obtain the mesa and the groove, the method further comprises: depositing a current spreading layer on the mesa; Depositing a metal layer on the current diffusion layer and the groove to form an electrode structure; A passivation layer is deposited on the metal layer.

4. The preparation method according to claim 2, characterized in that: The method of performing reverse soldering on the blue light LED epitaxial wafer with the light blocking wall to obtain the monochromatic Micro-LED array comprises: Depositing a substrate on the blue LED epitaxial wafer with the light-blocking wall; Etching the substrate on the table to etch electrode contact holes; Metal solder joints are deposited at the electrode contact holes to obtain the single-color Micro-LED array.

5. The preparation method according to claim 1, characterized in that: Different quantum dot solutions are pressed into the hollow dots at a set speed using an inkjet printing method to form red quantum dots and green quantum dots.

6. The preparation method according to claim 5, characterized in that: The printed quantum dot solution is dried or vacuumed at low temperature to evaporate the benign solvent in the quantum dot solution and retain the pixel-level quantum dots.

7. The preparation method according to claim 1, characterized in that: The metal plate is made of aluminum or gold.

8. A full-color Micro-LED, characterized in that: It is prepared by the preparation method of a full-color Micro-LED as described in any one of claims 1 to 7.

9. A display device, characterized in that: Including the full-color Micro-LED as described in claim 8.

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