Display screen, micro-led display substrate and preparation method thereof

Abstract

The application provides a display screen, a Micro-LED display substrate and a preparation method thereof, wherein the Micro-LED display substrate comprises a substrate, and a light-emitting unit arranged on the substrate, wherein the light-emitting unit comprises three-color Micro-LED chips arranged in an array, and the light-emitting unit comprises three stacked layers, each layer is arranged with Micro-LED chips of one color, and three adjacent Micro-LED chips of different colors are matched to form a light-emitting array group, and the light-emitting array group has full-color light-emitting function. The Micro-LED display substrate and the preparation method thereof can solve the problems of color difference and crosstalk of the three-color Micro-LED chips.

Description

Technical Field

[0001] This invention relates to the field of semiconductor light-emitting device technology, and in particular to a display screen, a Micro-LED display substrate, and a method for preparing the same. Background Technology

[0002] In recent years, Micro-LED display substrates have gradually emerged as one of the rising stars in display technology. However, their unique technical characteristics and numerous and challenging technical bottlenecks have become a significant obstacle to their further development. As a display device, Micro-LED display substrates possess more prominent advantages than traditional LED display substrates, such as low power consumption, fast response, long lifespan, and high luminous efficacy. Due to these characteristics, they have significant application value in fields requiring high-resolution displays, helmet-mounted displays, miniature projectors, and micro-wearable electronics.

[0003] In existing Micro-LED display substrates, RGB (red, green, and blue) Micro-LED chips are used for mixed excitation. Because the chips are shrunk to the micrometer level, alignment and mass transfer of the three chips are required, resulting in a large workload, high difficulty, and poor alignment accuracy. Alternatively, some reports have described stacking the RGB chips. While this stacking eliminates the need for alignment during fabrication due to vertical overlap, the chips will obstruct each other, requiring metal wiring between them. Furthermore, insulating layers are needed between the chips and between the P and N electrodes for isolation. To achieve good insulation, the insulating layer material typically needs to be relatively thick. This thick insulating layer material, along with the metals and semiconductors within it, generates significant film stress. With three chips in the vertical direction and multiple structural layers, the stress is high, potentially causing the insulating layer material to split or even detach, thus reducing the reliability and yield of the display substrate. Due to the aforementioned factors, when these micron-sized chips are assembled into a fixed module, the RGB chips overlap vertically. As a result, the light emission angles of the three RGB chips are mismatched, and the side light emission interferes with the light emission of adjacent chips, easily causing crosstalk. This affects the light emission quality and image quality of the full-color display substrate, resulting in poor color depth and failure to achieve the desired display effect. Summary of the Invention

[0004] The purpose of this invention is to provide a display screen, a Micro-LED display substrate, and a method for preparing the same, so as to solve the problems of color difference and crosstalk in three-primary-color Micro-LED chips.

[0005] To achieve the above and other related objectives, the present invention provides a Micro-LED display substrate, comprising:

[0006] Substrate;

[0007] A light-emitting unit is disposed on the substrate. The light-emitting unit includes three primary color Micro-LED chips arranged in an array. The light-emitting unit includes three stacked layers, each layer containing Micro-LED chips of one primary color. Three adjacent Micro-LED chips of different primary colors are paired to form a light-emitting array group. The light-emitting array group has a full-color light-emitting function.

[0008] Optionally, the light-emitting unit comprises three stacked layers, and the three layers of Micro-LED chips of different primary colors do not overlap in the vertical direction.

[0009] Optionally, the three-color Micro-LED chip includes a first-color Micro-LED chip, a second-color Micro-LED chip, and a third-color Micro-LED chip, with at least two empty spaces reserved between adjacent Micro-LED chips of the same color for laying out Micro-LED chips of the other two colors.

[0010] Optionally, the stacked three layers are arranged from bottom to top as a first primary color Micro-LED chip, a second primary color Micro-LED chip, and a third primary color Micro-LED chip.

[0011] Optionally, an oxide bonding layer is provided between the first primary color Micro-LED chip and the second primary color Micro-LED chip, and an oxide bonding layer is provided between the second primary color Micro-LED chip and the third primary color Micro-LED chip.

[0012] Optionally, the oxide bonding layer may be made of a transparent and non-conductive oxide material.

[0013] Optionally, the first primary color Micro-LED chip is a blue flip-chip Micro-LED chip or a green flip-chip Micro-LED chip; the second primary color Micro-LED chip is a green flip-chip Micro-LED chip or a blue flip-chip Micro-LED chip, and the second primary color Micro-LED chip is different from the first primary color Micro-LED chip; the third primary color Micro-LED chip is a red flip-chip Micro-LED chip.

[0014] Optionally, the third primary color Micro-LED chip includes, from top to bottom, an etching barrier layer, a first type ohmic contact layer, a first type extended layer, a first type roughening layer, a first type confinement layer, a multiple quantum well layer, a second type confinement layer, a second type extended layer, a second type ohmic contact layer, a diffusion barrier layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0015] Optionally, the first primary color Micro-LED chip includes, from bottom to top, an undoped GaN layer, a first type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a second type semiconductor layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0016] Optionally, the second primary color Micro-LED chip includes, from top to bottom, an undoped GaN layer, a first type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a second type semiconductor layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0017] Optionally, the Micro-LED chip is rectangular, with the first type electrode layer and the second type electrode layer of the chip at its two ends.

[0018] Optionally, the width of the Micro-LED chip is 20μm to 50μm and the length is 40μm to 100μm.

[0019] Optionally, the vacant position is filled with a transparent insulating layer.

[0020] To achieve the above and other related objectives, the present invention also provides a method for preparing a Micro-LED display substrate, comprising the following steps:

[0021] A first primary color LED wafer and a second primary color LED wafer are provided. The first primary color LED wafer includes a plurality of first primary color Micro-LED chips, and the second primary color LED wafer includes a plurality of second primary color Micro-LED chips.

[0022] Perform alignment bonding of the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer;

[0023] The substrate on the second surface of the second primary color LED wafer is peeled off to form a combined wafer with two primary colors of Micro-LED chips;

[0024] A third primary color LED wafer is provided, the third primary color LED wafer comprising a plurality of third primary color Micro-LED chips;

[0025] The first surface of the third primary color LED wafer is aligned and bonded to the second surface of the second primary color LED wafer after the substrate has been removed;

[0026] The substrate on the second surface of the third primary color LED wafer is removed to form a combined wafer of Micro-LED chips with three primary colors;

[0027] The combined wafer of Micro-LED chips with three primary colors is cut to form a Micro-LED display substrate;

[0028] The Micro-LED display substrate includes a substrate and light-emitting units located on the substrate. The light-emitting units include three-color Micro-LED chips arranged in an array after being cut from a Micro-LED composite wafer with three primary colors.

[0029] Optionally, the first primary color Micro-LED chip, the second primary color Micro-LED chip, and the third primary color Micro-LED chip do not overlap in the vertical direction.

[0030] Optionally, the first primary color Micro-LED chip is a blue flip-chip Micro-LED chip or a green flip-chip Micro-LED chip; the second primary color Micro-LED chip is a green flip-chip Micro-LED chip or a blue flip-chip Micro-LED chip, and the second primary color Micro-LED chip is different from the first primary color Micro-LED chip; the third primary color Micro-LED chip is a red flip-chip Micro-LED chip.

[0031] Optionally, the third primary color Micro-LED chip includes, from bottom to top, an etching barrier layer, a first type ohmic contact layer, a first type extended layer, a first type roughening layer, a first type confinement layer, a multiple quantum well layer, a second type confinement layer, a second type extended layer, a second type ohmic contact layer, a diffusion barrier layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0032] Optionally, the first primary color Micro-LED chip includes, from bottom to top, an undoped GaN layer, a first type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a second type semiconductor layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0033] Optionally, the second primary color Micro-LED chip includes, from bottom to top, an undoped GaN layer, a first type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a second type semiconductor layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0034] Optionally, a first primary color LED wafer and a second primary color LED wafer are provided. The first primary color LED wafer includes a plurality of first primary color Micro-LED chips, and the second primary color LED wafer includes a plurality of second primary color Micro-LED chips. Specific steps include:

[0035] A first primary color LED wafer is provided, and the first primary color LED wafer is dry etched. The etching stops on the substrate of the first primary color LED wafer to form a plurality of first primary color Micro-LED chips. At least two empty positions are reserved between adjacent first primary color Micro-LED chips for laying out second primary color Micro-LED chips and third primary color Micro-LED chips.

[0036] A second primary color LED wafer is provided, and the second primary color LED wafer is dry etched. The etching stops on the substrate of the second primary color LED wafer to form a plurality of second primary color Micro-LED chips. At least two empty positions are reserved between adjacent second primary color Micro-LED chips for the placement of the first primary color Micro-LED chip and the third primary color Micro-LED chip.

[0037] A third primary color LED wafer is provided, the third primary color LED wafer comprising a plurality of third primary color Micro-LED chips, the specific steps of which include:

[0038] A third primary color LED wafer is provided, and the third primary color LED wafer is dry etched. The etching stops on the substrate of the third primary color LED wafer to form a plurality of third primary color Micro-LED chips. At least two empty positions are reserved between adjacent third primary color Micro-LED chips for the placement of the first primary color Micro-LED chip and the second primary color Micro-LED chip.

[0039] Optionally, before the step of aligning and bonding the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer, the method further includes:

[0040] A first lead is formed on the passivation layer on the first primary color LED wafer, and the first type electrode layer and the second type electrode layer of the first primary color Micro-LED chip are respectively connected to the external contact point on the periphery of the light-emitting unit through the first lead;

[0041] A first oxide bonding layer is formed on the first surface of the first primary color LED wafer that forms the first lead.

[0042] Optionally, before the step of aligning and bonding the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer, the method further includes:

[0043] A second lead is formed on the passivation layer of the second primary color LED wafer, and the first type electrode layer and the second type electrode layer of the second primary color Micro-LED chip are respectively connected to the external contact point around the light-emitting unit through the second lead;

[0044] A second oxide bonding layer is formed on the first surface of the second primary color LED wafer that forms the second lead.

[0045] Optionally, the step of aligning and bonding the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer includes:

[0046] The first oxide bonding layer is chemically and mechanically polished to serve as the first bonding surface;

[0047] The second oxide bonding layer is chemically and mechanically polished to serve as the second bonding surface;

[0048] The first and second bonding surfaces were activated using an activation solution, and then aligned bonding was achieved under high temperature and high pressure.

[0049] Optionally, before the step of aligning and bonding the first surface of the third primary color LED wafer with the second primary color LED wafer after the substrate has been removed, the method further includes:

[0050] A third lead is formed on the third passivation layer of the third primary color LED wafer, and the first type electrode layer and the second type electrode layer of the third primary color Micro-LED chip are respectively connected to the external contact point around the light-emitting unit through the third lead;

[0051] A third oxide bonding layer is formed on the first surface of the third primary color LED wafer in which the third lead is formed;

[0052] A fourth oxide bonding layer is formed on the second surface of the substrate after the second primary color LED wafer is stripped.

[0053] Optionally, the step of aligning and bonding the first surface of the third primary color LED wafer with the second surface of the second primary color LED wafer after the substrate has been removed includes:

[0054] The third oxide bonding layer is subjected to chemical mechanical polishing to serve as the third bonding surface;

[0055] The fourth oxide bonding layer is subjected to chemical mechanical polishing to serve as the fourth bonding surface;

[0056] The third and fourth bonding surfaces were activated using an activation solution, and then para-bonding was achieved under high temperature and high pressure.

[0057] Optionally, the activation solution includes a mixture of ammonia, hydrofluoric acid, and hydrogen peroxide.

[0058] Optionally, after chemical mechanical polishing, the surface roughness of all oxide bonded layers is less than [value missing].

[0059] Optionally, all oxide bonding layers are made of transparent and non-conductive oxide materials with a thickness of 3μm to 5μm.

[0060] Optionally, the formation process of the first lead, the second lead, and the third lead includes one of the stripping process and the electron beam evaporation process.

[0061] Optionally, the lengths of the first primary color Micro-LED chip, the second primary color Micro-LED chip, and the third primary color Micro-LED chip are all 40μm to 100μm, and the widths are 20μm to 50μm.

[0062] Optionally, the process of stripping the substrate from the second surface of the second primary color LED wafer includes a laser irradiation stripping process.

[0063] Optionally, the method for removing the substrate from the second surface of the third primary color LED wafer includes an etching process, wherein the etching process solution includes a mixture of ammonia and hydrogen peroxide.

[0064] Optionally, before the step of forming a first oxide bonding layer on the first surface of the first primary color LED wafer to form the first lead, a transparent insulating layer is further included to fill the vacancy position of the first primary color LED wafer.

[0065] Before the step of forming a second oxide bonding layer on the first surface of the second primary color LED wafer to form the second lead, the method further includes filling the vacancy positions of the second primary color LED wafer with a transparent insulating layer.

[0066] Before the step of forming a third oxide bonding layer on the first surface of the third primary color LED wafer to form the third lead, a transparent insulating layer is also included to fill the vacancy positions of the third primary color LED wafer.

[0067] To achieve the above and other related objectives, the present invention also provides a display screen, including a driving panel, the aforementioned Micro-LED display substrate, and circuitry, wherein the Micro-LED display substrate is connected to the driving panel via circuitry.

[0068] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0069] This invention provides a Micro-LED display substrate comprising three stacked layers, each layer containing Micro-LED chips of a different primary color. The three primary color Micro-LED chips are arranged in an array, and the three layers of Micro-LED chips of different primary colors do not overlap in the vertical direction. Furthermore, the chips and circuits of each layer can be independently controlled, thereby reducing color difference and crosstalk problems, and enabling full-color light emission.

[0070] This invention also provides a method for fabricating a Micro-LED display substrate, which uses a multi-layer alignment bonding process between wafers to realize the array arrangement of three-color Micro-LED chips. This method can eliminate the need for mass transfer, reduce alignment and fabrication difficulty, and improve production efficiency and yield. Furthermore, it can eliminate the step of transferring red Micro-LED chips to a sapphire substrate, allowing all three-color Micro-LED chips to be transferred directly to the same substrate in one step, making the method simple. Attached Figure Description

[0071] Figure 1 This is a partial structural schematic diagram of a blue Micro-LED wafer according to an embodiment of the present invention;

[0072] Figure 2 This is a partial structural schematic diagram of a green Micro-LED wafer according to an embodiment of the present invention;

[0073] Figure 3 This is a partial structural schematic diagram of a red Micro-LED wafer according to an embodiment of the present invention;

[0074] Figure 4 This is a partial structural schematic diagram of a combined wafer of Micro-LED chips with three primary colors according to an embodiment of the present invention;

[0075] Figure 5 This is a top view of a combined wafer of Micro-LED chips with three primary colors according to an embodiment of the present invention;

[0076] Figure 6 This is a cross-sectional view of a Micro-LED display substrate according to an embodiment of the present invention;

[0077] Figures 7-14 This is a cross-sectional view of each step in a method for preparing a Micro-LED display substrate according to an embodiment of the present invention. Detailed Implementation

[0078] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more comprehensive understanding of the display screen, Micro-LED display substrate, and their fabrication method proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0079] The Micro-LED display substrate provided by the present invention includes: a substrate; a light-emitting unit disposed on the substrate, the light-emitting unit including three primary color Micro-LED chips, the three primary color Micro-LED chips being arranged in an array, and the light-emitting unit including three stacked layers, each layer being arranged with a primary color Micro-LED chip, and three adjacent Micro-LED chips of different primary colors being paired to form a light-emitting array group, the light-emitting array group having a full-color light-emitting function.

[0080] The light-emitting unit includes three primary color Micro-LED chips, specifically red, green, and blue Micro-LED chips, but is not limited to these. The three primary color Micro-LED chips are fabricated into independent, non-overlapping light-emitting array groups. The light-emitting unit includes multiple light-emitting array groups, which can be configured with three primary color (RGB) Micro-LEDs according to design requirements. Each light-emitting array group has at least one red Micro-LED chip, one green Micro-LED chip, and one blue Micro-LED chip; in other embodiments, it may also have one red Micro-LED chip, two green Micro-LED chips, and one blue Micro-LED chip, or two red Micro-LED chips, one green Micro-LED chip, and one blue Micro-LED chip.

[0081] In this embodiment, the three-primary-color Micro-LED chip can be at least one of flip-chip Micro-LED chips, upright Micro-LED chips, and vertical Micro-LED chips, but is not limited thereto. Preferably, the three-primary-color Micro-LED chip is a flip-chip Micro-LED chip. The three-primary-color Micro-LED chip includes a first-primary-color Micro-LED chip, a second-primary-color Micro-LED chip, and a third-primary-color Micro-LED chip. The stacked three layers are arranged sequentially from bottom to top: the first-primary-color Micro-LED chip is a blue flip-chip Micro-LED chip or a green flip-chip Micro-LED chip; the second-primary-color Micro-LED chip is a green flip-chip Micro-LED chip or a blue flip-chip Micro-LED chip, and the second-primary-color Micro-LED chip is different from the first-primary-color Micro-LED chip; the third-primary-color Micro-LED chip is a red flip-chip Micro-LED chip. For example, the three-primary-color Micro-LED chip includes a red flip-chip Micro-LED chip, a blue flip-chip Micro-LED chip, and a green flip-chip Micro-LED chip. The three-primary-color Micro-LED chip is fabricated from a three-primary-color LED wafer, see reference [link / reference]. Figures 1-3 The first primary color LED wafer 1 is ultimately formed into a wafer with multiple first primary color Micro-LED chips 11 through a series of processes. For example, a blue LED wafer is ultimately formed into a wafer with multiple blue flip-chip Micro-LED chips through a series of processes. The second primary color LED wafer 2 is ultimately formed into a wafer with multiple second primary color Micro-LED chips 21 through a series of processes. For example, a green LED wafer is ultimately formed into a wafer with multiple green flip-chip Micro-LED chips through a series of processes. The third primary color LED wafer 3 is ultimately formed into a wafer with multiple third primary color Micro-LED chips 31 through a series of processes. For example, a red LED wafer is ultimately formed into a wafer with multiple red flip-chip Micro-LED chips through a series of processes.

[0082] A first oxide bonding layer and a second oxide bonding layer are provided between the first primary color Micro-LED chip and the second primary color Micro-LED chip, and a third oxide bonding layer and a fourth oxide bonding layer are provided between the second primary color Micro-LED chip and the third primary color Micro-LED chip. The oxide bonding layer is made of a transparent and non-conductive oxide material.

[0083] The light-emitting unit comprises three stacked layers, with the three layers of Micro-LED chips of different primary colors not overlapping in the vertical direction. Therefore, there is only one chip per layer in the vertical direction, resulting in low stress and improving the reliability and yield of the Micro-LED display substrate.

[0084] At least two empty spaces are reserved between adjacent Micro-LED chips of the same primary color, to be used for Micro-LED chips of the other two primary colors. (See also...) Figure 4 The first layer consists of first-color LED wafers 1, such as blue LED wafers (i.e., the blue LED wafer at the bottom layer), with two empty positions reserved between adjacent blue flip-chip Micro-LEDs on the horizontal plane of this layer. The second layer consists of second-color LED wafers 2, such as green LED wafers (i.e., the green LED wafer in the middle layer), with the green flip-chip Micro-LED corresponding to one of the reserved empty positions on the first-layer blue LED wafers. The third layer consists of third-color LED wafers 3, such as red LED wafers (i.e., the red LED wafer at the top layer), with the red flip-chip Micro-LED corresponding to one of the remaining empty positions on the first-layer blue LED wafers. (See reference...) Figure 5 This method of combining red, green, and blue flip-chip Micro-LEDs into an array in a top-down view can achieve a full-color display effect.

[0085] The vacant positions are filled with a transparent insulating layer. This transparent insulating layer fills the spaces between adjacent Micro-LED chips in each layer. Specifically, the transparent insulating layer includes a first insulating layer between the first primary color Micro-LED chips 11, a second insulating layer between the second primary color Micro-LED chips 21, and a third insulating layer between the third primary color Micro-LED chips 31. The material of the transparent insulating layer includes at least one of silicon oxide, aluminum oxide, and spin-on glass (SOG), but is not limited to these. The transparent insulating layer can be flush with or higher than the surface of the Micro-LED chips, and its thickness is preferably 10 μm to 15 μm.

[0086] The red flip-chip Micro-LED comprises, from bottom to top: an etch barrier layer, a first type ohmic contact layer, a first type extended layer, a first type roughening layer, a first type confinement layer, a multiple quantum well layer, a second type confinement layer, a second type extended layer, a second type ohmic contact layer, a diffusion barrier layer, a passivation layer, a first type electrode layer, and a second type electrode layer.

[0087] The etching barrier layer is preferably made of AlInGaP; the first type ohmic contact layer is preferably made of GaAs; the first type extended layer is preferably made of AlGaInP; the first type roughening layer is preferably made of AlGaInP; the first type confinement layer is preferably made of AlInP; the multi-quantum well layer includes a well layer and a barrier layer, the well layer is preferably made of GaInP, and the barrier layer is preferably made of AlGaInP; the second type confinement layer is preferably made of AlInP; the second type extended layer is preferably made of AlGaInP; the second type ohmic contact layer is preferably made of GaP; the diffusion barrier layer is preferably a TiW / Pt diffusion barrier layer, with a total thickness preferably of 500 nm to 800 nm. The TiW / Pt diffusion barrier layer adopts a TiW / Pt / TiW / Pt / TiW / Pt stacked structure, with the thickness of each TiW layer preferably of 300 nm to 500 nm and the thickness of each Pt layer preferably of 20 nm to 50 nm; the passivation layer is preferably made of silicon oxide or silicon nitride. The materials of each of the above structural layers are optimal, but not limited to these; other materials may be used in other embodiments.

[0088] The blue flip-chip Micro-LED chip comprises, from bottom to top: an undoped GaN layer, a first-type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a second-type semiconductor layer, a passivation layer, a first-type electrode layer, and a second-type electrode layer.

[0089] The green flip-chip Micro-LED comprises, from bottom to top: an undoped GaN layer, a first-type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a second-type semiconductor layer, a passivation layer, a first-type electrode layer, and a second-type electrode layer.

[0090] The materials of each structural layer of the blue flip-chip Micro-LED and the green flip-chip Micro-LED are similar. The first type semiconductor layer is preferably made of GaN; the multi-quantum-well layer of the green and blue flip-chip Micro-LEDs includes a well layer and a barrier layer, wherein the well layer is preferably made of InGaN, and the barrier layer is preferably made of GaN; the electron blocking layer is preferably made of AlGaN; the second type semiconductor layer is preferably made of GaN; and the passivation layer is preferably made of silicon oxide or silicon nitride. While the materials of each of the above structural layers are optimal, they are not limited to these, and other materials may be used in other embodiments.

[0091] The first type of structural layer is preferably an N-type structural layer, and the second type of structural layer is preferably a P-type structural layer. Specifically, the red flip-chip Micro-LED, from bottom to top, comprises: an etch barrier layer, an N-type ohmic contact layer, an N-type extension layer, an N-type roughening layer, an N-type confinement layer, a multiple quantum well layer, a P-type confinement layer, a P-type extension layer, a P-type ohmic contact layer, a diffusion barrier layer, a passivation layer, and an N-type electrode layer and a P-type electrode layer. The blue flip-chip Micro-LED, from bottom to top, comprises: an undoped GaN layer, an N-type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a P-type semiconductor layer, a passivation layer, an N-type electrode layer, and a P-type electrode layer. The green flip-chip Micro-LED, from bottom to top, comprises: an undoped GaN layer, an N-type semiconductor layer, a multiple quantum well layer, an electron blocking layer, a P-type semiconductor layer, a passivation layer, an N-type electrode layer, and a P-type electrode layer. The tri-color Micro-LED chip is rectangular, with its two ends being the P-electrode and N-electrode, respectively. The P-electrode and N-electrode of the tri-color Micro-LED chip are connected to external contact points around the light-emitting unit via leads. During subsequent packaging, these external contact points are led out to the package end. The width of the tri-color Micro-LED chip is preferably 20μm to 50μm, and the length is preferably 40μm to 100μm.

[0092] See Figure 6 The image shows a cross-sectional view of the Micro-LED display substrate in the vertical direction. For the fabrication method of the Micro-LED display substrate, please refer to [link to documentation]. Figures 7-14 This includes the following steps:

[0093] Step S1: Provide a first primary color LED wafer and a second primary color LED wafer. The first primary color LED wafer includes a plurality of first primary color Micro-LED chips, and the second primary color LED wafer includes a plurality of second primary color Micro-LED chips.

[0094] Step S2: Perform alignment bonding of the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer;

[0095] Step S3: Peel off the substrate from the second surface of the second primary color LED wafer to form a combined wafer with two primary colors of Micro-LED chips;

[0096] Step S4: Provide a third primary color LED wafer, wherein the third primary color LED wafer includes a plurality of third primary color Micro-LED chips;

[0097] Step S5: Align and bond the first surface of the third primary color LED wafer with the second surface of the second primary color LED wafer after the substrate has been removed;

[0098] Step S6: Remove the substrate from the second surface of the third primary color LED wafer to form a combined wafer of Micro-LED chips with three primary colors;

[0099] Step S7: Cut the combined wafer of Micro-LED chips with three primary colors to form a Micro-LED display substrate; wherein, the Micro-LED display substrate includes a substrate and light-emitting units located on the substrate, and the light-emitting units include three-primary-color Micro-LED chips arranged in an array after the combined wafer of Micro-LED chips with three primary colors is cut.

[0100] In step S1, the first primary color LED wafer is, for example, a first primary color LED epitaxial wafer with a first type electrode layer and a second type electrode layer formed thereon. The first primary color LED wafer is ultimately formed into multiple first primary color Micro-LED chips through a series of processes. For example, a blue LED wafer is ultimately formed into multiple blue flip-chip Micro-LED chips through a series of processes.

[0101] The first primary color LED wafer can be a blue LED wafer or a green LED wafer; the second primary color LED wafer can be a green LED wafer or a blue LED wafer, and the second primary color LED wafer is different from the first primary color LED wafer; for example, when the first primary color LED wafer is a blue LED wafer, the corresponding second primary color LED wafer is a green LED wafer. The third primary color LED wafer is a red LED wafer. The three primary color LED wafers include a first primary color LED wafer, a second primary color LED wafer, and a third primary color LED wafer, that is, the three primary color LED wafers include blue LED wafers, green LED wafers, and red LED wafers. In the following embodiments, the first primary color LED wafer is a blue LED wafer, the second primary color LED wafer is a green LED wafer, and the third primary color LED wafer is a red LED wafer, as an example for illustration.

[0102] In step S1, a first primary color LED wafer and a second primary color LED wafer are provided. The first primary color LED wafer includes a plurality of first primary color Micro-LED chips, and the second primary color LED wafer includes a plurality of second primary color Micro-LED chips. The specific steps include:

[0103] Step S11: Provide a first primary color LED wafer, perform dry etching on the first primary color LED wafer, stop the etching on the sapphire substrate of the first primary color LED wafer, and form a plurality of first primary color Micro-LED chips. At least two empty positions are reserved between adjacent first primary color Micro-LED chips for laying out the second primary color Micro-LED chip and the third primary color Micro-LED chip.

[0104] Step S12: Provide a second primary color LED wafer, perform dry etching on the second primary color LED wafer, and stop the etching on the sapphire substrate of the second primary color LED wafer to form a plurality of second primary color Micro-LED chips. At least two empty positions are reserved between adjacent second primary color Micro-LED chips for the layout of the first primary color Micro-LED chip and the third primary color Micro-LED chip.

[0105] The second primary color Micro-LED chip is located on one of the vacant positions reserved by the first primary color Micro-LED chip on the horizontal plane.

[0106] Figure 7 A cross-sectional view of the first primary color LED epitaxial wafer is shown, specifically a cross-sectional view of the blue LED epitaxial wafer. A first-type electrode layer 121 and a second-type electrode layer 122 are formed on the blue LED epitaxial wafer to form a blue LED wafer. Therefore, refer to... Figure 7 and8 The blue LED wafer comprises, from bottom to top: a sapphire substrate 10, an undoped GaN layer (not shown in the figure), a first type semiconductor layer 111, a multiple quantum well layer (not shown in the figure), an electron blocking layer (not shown in the figure), a second type semiconductor layer 112, a passivation layer (not shown in the figure), a first type electrode layer 121, and a second type electrode layer 122.

[0107] Continue reading Figure 8 The first primary color LED wafer is etched to form multiple first primary color Micro-LED chips 11. The etching is preferably dry etching, and the first primary color LED wafer can be etched to form multiple first primary color Micro-LED chips 11. At least two empty positions are reserved between adjacent first primary color Micro-LED chips 11 for arranging second primary color Micro-LED chips 21 and third primary color Micro-LED chips 31. The dry etching stops on the upper surface of the sapphire substrate 10 to divide the first primary color LED wafer into multiple first primary color Micro-LED chips 11. The dimensions of the first primary color flip-chip Micro-LED chips are preferably 20μm to 50μm in width and 40μm to 100μm in length.

[0108] See Figure 9 Between step S11 and step S12, the following is also included:

[0109] A first lead (not shown in the figure) is formed on the passivation layer of the first primary color LED wafer. The first type electrode layer 121 and the second type electrode layer 122 of the first primary color Micro-LED chip 11 are respectively connected to the external contact point of the light-emitting unit. The external contact point is led out to the package end during subsequent packaging.

[0110] A first oxide bonding layer 14 is formed on the first surface of the first primary color LED wafer that forms the first lead.

[0111] In addition, the first lead can also be fabricated together with the first type electrode layer 121 and the second type electrode layer 122, that is, the first lead is formed during the preparation of the first type electrode layer 121 and the second type electrode layer 122.

[0112] In this embodiment, the second surface of the LED wafer is defined as the surface near the substrate, and the first surface is the surface on the side where the electrode is formed.

[0113] The formation process of the first lead includes, but is not limited to, a lift-off process and an electron beam evaporation process (e-gun). The material of the first lead is preferably a metal lead. The first lead serves as a connection line between the first type electrode layer 121 and the second type electrode layer 122 of the first primary color Micro-LED chip, connecting the first type electrode layer 121 and the second type electrode layer 122 of the first primary color Micro-LED chip 11 to the external contact points on the periphery of the light-emitting unit, respectively.

[0114] The process for forming the first oxide bonding layer 14 includes, but is not limited to, plasma processing. The material of the first oxide bonding layer 14 is preferably one of alumina, silicon oxide, and spin-on glass (SOG), but is not limited to these. The thickness of the first oxide bonding layer 14 is preferably 3 μm to 5 μm. For example, a 4 μm thick SiO2 layer can be deposited on the first surface of the first primary color LED wafer using a plasma process.

[0115] The preferred material for the oxide bonding layer is SiO2, a transparent insulating material that significantly improves external quantum efficiency, meaning the light emitted by the three-primary-color Micro-LED chip can easily pass through the oxide bonding layer. If metal bonding is used, the metal material is generally opaque, significantly affecting brightness. Furthermore, it requires drilling to form electrical connections, making the process complex. Metal bonding also requires point-to-point alignment, demanding high precision. Oxide bonding, on the other hand, is wafer-wide bonding, eliminating the need for point-to-point alignment and requiring lower alignment precision, thus improving alignment accuracy and bonding quality. Moreover, with oxide bonding, the leads can be placed inside the oxide bonding layer, forming good insulation and isolation, reducing leakage risk, improving the reliability and yield of the Micro-LED display substrate, and consequently improving the emission angle matching of the three-primary-color Micro-LED chip, solving the color difference and crosstalk problems inherent in three-primary-color Micro-LED chips.

[0116] Before forming the first oxide bonding layer 14 on the first surface of the first primary color LED wafer to form the first lead, the method further includes filling the first primary color LED wafer with a first insulating layer 13. The first insulating layer 13 fills at least two pre-reserved gaps between adjacent first primary color Micro-LED chips 11, and the upper surface of the first insulating layer 13 is flush with or higher than the upper surface of the second type electrode layer 122. The first oxide bonding layer 14 also covers the first insulating layer 13. The material of the first insulating layer 13 is preferably at least one of silicon oxide, aluminum oxide, and spin-on glass (SOG), but is not limited thereto. The first insulating layer is easy to implement, low in cost, and has relatively low process difficulty.

[0117] See Figure 10 The process may further include the following after step S12:

[0118] A second lead (not shown in the figure) is formed on the passivation layer of the second primary color LED wafer. The first type electrode layer 221 and the second type electrode layer 222 of the second primary color Micro-LED chip 21 are respectively connected to the external contact point around the light-emitting unit through the second lead. The external contact point is led out to the packaging end during subsequent packaging.

[0119] A second oxide bonding layer 24 is formed on the first surface of the second primary color LED wafer that forms the second lead.

[0120] In addition, the second lead can also be fabricated together with the first type electrode layer 221 and the second type electrode layer 222, that is, the second lead is formed during the preparation of the first type electrode layer 221 and the second type electrode layer 222.

[0121] The formation process of the second lead includes, but is not limited to, a lift-off process and an electron beam evaporation process (e-gun). The material of the second lead is preferably a metal lead. The second lead serves as a connection line between the first type electrode layer 221 and the second type electrode layer 222 of the second primary color Micro-LED chip, connecting the first type electrode layer 221 and the second type electrode layer 222 of the second primary color Micro-LED chip 21 to the external contact points on the periphery of the light-emitting unit, respectively.

[0122] The process for forming the second oxide bonding layer 24 includes, but is not limited to, plasma processing. The material of the second oxide bonding layer 24 is preferably one of alumina, silicon oxide, and spin-on glass (SOG), but is not limited to these. The thickness of the second oxide bonding layer 24 is preferably 3 μm to 5 μm. For example, a 4 μm thick SiO2 layer can be deposited on the first surface of the second primary color LED wafer using a plasma process.

[0123] Before the step of forming the second oxide bonding layer 24 on the first surface of the second primary color LED wafer to form the second lead, the method further includes filling the second primary color LED wafer with a second insulating layer 23. The second insulating layer 23 fills at least two pre-reserved gaps between adjacent second primary color Micro-LED chips 21, and the upper surface of the second insulating layer 23 is flush with or higher than the upper surface of the second type electrode layer 222. The second oxide bonding layer 24 also covers the second insulating layer 23. The material of the second insulating layer 23 is preferably at least one of silicon oxide, aluminum oxide, and spin-on glass (SOG), but is not limited thereto.

[0124] See Figure 11 In step S2, the specific steps for aligning and bonding the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer include:

[0125] Step S21: Perform chemical mechanical polishing on the first oxide bonding layer 14 to serve as the first bonding surface;

[0126] Step S22: Perform chemical mechanical polishing on the second oxide bonding layer 24 to serve as the second bonding surface;

[0127] Step S23: The first bonding surface and the second bonding surface are activated with an activation solution, and the alignment bonding is achieved under high temperature and high pressure.

[0128] In steps S21 and S22, after the first oxide bonding layer 14 and the second oxide bonding layer 24 are chemically mechanically polished, their surface roughness is reduced.

[0129] In step S23, an activation solution is prepared using ammonia, hydrofluoric acid, and hydrogen peroxide in a certain proportion to activate the bonding surface, forming HOH chemical bonds. Then, the bonding is performed under high temperature and high pressure. The preferred high temperature is 400℃~600℃; the preferred high pressure is 15000kgf~20000kgf. In this example, multiple first-color Micro-LED chips are bonded to multiple second-color Micro-LED chips simultaneously. That is, bonding the first-color Micro-LED chips to the second-color Micro-LED chips is equivalent to aligning and bonding the entire first-color LED wafer to the second-color LED wafer, eliminating the need for separate alignment and bonding of each first-color Micro-LED chip to each second-color Micro-LED chip. This embodiment is simple and easy to implement, saving significant process time and reducing alignment difficulty, improving alignment accuracy and bonding quality, and avoiding errors that occur during the bonding process of a large number of Micro-LED chips. This helps reduce color difference and crosstalk problems.

[0130] In step S3, the substrate on the second surface of the second primary color LED wafer is peeled off to form a combined wafer with two primary colors of Micro-LED chips. Preferably, laser irradiation is used to peel off the substrate 20 on the second surface of the second primary color LED wafer.

[0131] See Figure 12 In step S4, a third primary color LED wafer is provided and etched, with the etching stopping at the upper surface of the substrate 30, forming multiple third primary color Micro-LED chips 31. At least two empty positions are reserved between adjacent third primary color Micro-LED chips for arranging the first and second primary color Micro-LED chips. The etching method is preferably dry etching, and the third primary color Micro-LED chip 31 can be located on a horizontal plane at another of the reserved empty positions of the first primary color Micro-LED chip 11. The substrate 30 of the third primary color LED wafer is preferably a GaAs substrate.

[0132] Between step S4 and step S5, the following is also included:

[0133] A third lead (not shown in the figure) is formed on the passivation layer of the third primary color LED wafer. The first type electrode layer 321 and the second type electrode layer 322 of the third primary color Micro-LED chip 31 are respectively connected to the external contact point around the light-emitting unit through the third lead. The external contact point is led out to the package end during subsequent packaging.

[0134] A third oxide bonding layer 34 is formed on the first surface of the third primary color LED wafer in which the third lead is formed;

[0135] A fourth oxide bonding layer 40 is formed on the second surface of the substrate 20 after the second primary color LED wafer is stripped.

[0136] The formation process of the third lead includes, but is not limited to, a lift-off process and an electron beam evaporation process (e-gun). The material of the third lead is preferably a metal lead. The third lead serves as a connection line between the first type electrode layer 321 and the second type electrode layer 322 of the third primary color Micro-LED chip, connecting the first type electrode layer 321 and the second type electrode layer 322 of the third primary color Micro-LED chip 31 to the external contact points surrounding the light-emitting unit.

[0137] The processes used to form the third oxide bonding layer 34 and the fourth oxide bonding layer 40 include, but are not limited to, plasma technology. The materials used for the third oxide bonding layer 34 and the fourth oxide bonding layer 40 are preferably alumina, silicon oxide, and spin-on glass (SOG), but are not limited to these. The thickness of the third oxide bonding layer 34 and the fourth oxide bonding layer 40 is preferably 3 μm to 5 μm. For example, a 4 μm thick SiO2 layer can be deposited on a third primary color LED wafer using a plasma process.

[0138] Before the step of forming the third oxide bonding layer 34 on the first surface of the third primary color LED wafer to form the third lead, the method further includes filling the third primary color LED wafer with a third insulating layer 33. The third insulating layer 33 fills at least two vacancy positions reserved between adjacent third primary color Micro-LED chips 31, and the upper surface of the third insulating layer 33 is flush with or higher than the upper surface of the second type electrode layer 322. The third oxide bonding layer 34 also covers the third insulating layer 33. The material of the third insulating layer 33 is preferably at least one of silicon oxide, aluminum oxide, and spin-on glass (SOG), but is not limited thereto.

[0139] See Figure 13 In step S5, the specific steps for aligning and bonding the first surface of the third primary color LED wafer with the second surface of the second primary color LED wafer after the substrate has been removed include:

[0140] Step S51: Perform chemical mechanical polishing on the third oxide bonding layer to serve as the third bonding surface;

[0141] Step S52: Perform chemical mechanical polishing on the fourth oxide bonding layer to obtain the fourth bonding surface;

[0142] Step S53: The third and fourth bonding surfaces are activated with an activation solution and then aligned under high temperature and high pressure.

[0143] In steps S51 and S52, after the third oxide bonding layer and the fourth oxide bonding layer are subjected to chemical mechanical polishing, their surface roughness is reduced.

[0144] In step S53, an activation solution is prepared using ammonia, hydrofluoric acid, and hydrogen peroxide in a certain proportion to activate the bonding surface, forming HOH chemical bonds. Then, the bonding is performed under high temperature and high pressure. The preferred high temperature is 400℃~600℃; the preferred high pressure is 15000kgf~20000kgf. In this example, multiple third-primary-color Micro-LED chips are bonded simultaneously to multiple second-primary-color Micro-LED chips with removed second-surface substrates. This means the entire third-primary-color LED wafer is aligned and bonded to a wafer containing LED chips of both primary colors, eliminating the need to individually align and bond each third-primary-color Micro-LED chip. This simplifies the process, saves significant processing time, reduces alignment difficulty, improves alignment accuracy and bonding quality, and avoids errors that occur with a large number of Micro-LED chips during bonding, thus reducing color difference and crosstalk issues.

[0145] See Figure 14 In step S6, the method for removing the substrate from the second surface of the third primary color LED wafer includes an etching process. The etching solution includes, for example, a mixture of ammonia and hydrogen peroxide, with a preferred mixing ratio of 1:10. For example, ammonia and hydrogen peroxide are used to etch and remove the GaAs substrate of the red LED wafer, ultimately forming a combined wafer of blue, green, and red Micro-LED chips, while the remaining sapphire substrate serves as the substrate of the Micro-LED display substrate.

[0146] In step S7, the combined wafer of Micro-LED chips with three primary colors is cut to form a Micro-LED display substrate; wherein, the Micro-LED display substrate includes a substrate and light-emitting units located on the substrate, and the light-emitting units include three-primary-color Micro-LED chips arranged in an array after the combined wafer of Micro-LED chips with three primary colors is cut.

[0147] In summary, this invention eliminates the need for mass transfer, solving the problems of low production yield, time-consuming and labor-intensive processes caused by the immaturity of mass transfer-related technologies, which prevent mass production. It reduces manufacturing difficulty and improves production efficiency and yield. Furthermore, the Micro-LED display substrate of this invention comprises three stacked layers, each layer containing Micro-LED chips of a different primary color. These three primary color Micro-LED chips are arranged in an array, and the three layers of different primary color Micro-LED chips do not overlap vertically. Each layer's chips and circuitry can be independently controlled, thereby reducing color difference and crosstalk issues and enabling full-color illumination.

[0148] This invention employs a multi-stage alignment and bonding process to directly transfer three-primary-color Micro-LED chips onto the same Micro-LED display substrate in a single step. This method is simple and eliminates the complexity of requiring independent operations for vertically structured red Micro-LED wafers. Specifically, in this embodiment, entire wafers are aligned together, rather than requiring individual chip-to-chip alignment as in existing technologies. This eliminates the need for massive transfers, reduces alignment and fabrication difficulty, improves production efficiency and yield, and helps solve problems related to color difference and crosstalk.

[0149] Furthermore, this invention allows for the design of a Micro-LED display screen of the required size based on product specifications, and enables the connection and testing of related circuits during the manufacturing process. Additionally, because the three-primary-color Micro-LED chips are obtained through photolithography and etching processes, this invention allows for precise control over pixel size and array arrangement.

[0150] In addition, the present invention also provides a display screen, including a driving panel, the aforementioned Micro-LED display substrate, and circuitry, wherein the Micro-LED display substrate is connected to the driving panel via circuitry. The driving panel may be, for example, a PCB board.

[0151] The aforementioned display screen can achieve full-color illumination and can solve the problems of color difference and crosstalk that exist in traditional Micro-LED displays.

[0152] Furthermore, it is understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of protection of the present invention.

[0153] Furthermore, it should be understood that the invention is not limited to the specific methods, compounds, materials, manufacturing techniques, uses, and applications described herein, which can vary. It should also be understood that the terminology described herein is used only to describe particular embodiments and not to limit the scope of the invention. It must be noted that the singular forms “a,” “an,” and “the” used herein and in the appended claims include plural bases unless the context clearly indicates otherwise. Thus, for example, a reference to “a step” means a reference to one or more steps, and may include secondary steps. All conjunctions used should be understood in the broadest sense. Therefore, the word “or” should be understood to have the definition of logical “or” rather than logical “exclusive”, unless the context clearly indicates otherwise. Structures described herein will be understood to also refer to functional equivalents of that structure. Language that can be interpreted as approximate should be understood in that way unless the context clearly indicates otherwise.

Claims

1. A Micro-LED display substrate, characterized in that, The application relates to a substrate, a light-emitting unit arranged on the substrate, the light-emitting unit comprising three-color Micro-LED chips arranged in an array, the light-emitting unit comprising three stacked layers, each layer arranged with Micro-LED chips of one color, at least two vacant positions reserved between any adjacent Micro-LED chips of the same color for arranging Micro-LED chips of the other two colors, three adjacent Micro-LED chips of different colors forming a light-emitting array group, the light-emitting array group having full-color light-emitting function, the three-color Micro-LED chips comprising, from bottom to top, first-color Micro-LED chips, second-color Micro-LED chips and third-color Micro-LED chips, each color Micro-LED chip having an electrode layer, and the surface of the electrode layer side of each color Micro-LED chip being a first surface, the first surface of the first-color Micro-LED chips being aligned and bonded with the first surface of the second-color Micro-LED chips, the substrate of the second surface of the second-color LED wafer corresponding to the second-color Micro-LED chips being peeled off after bonding, the second surface of the second-color Micro-LED chips being aligned and bonded with the first surface of the third-color Micro-LED chips. The oxide bonding layer is arranged between the first-color Micro-LED chips and the second-color Micro-LED chips, and between the second-color Micro-LED chips and the third-color Micro-LED chips, and the material of the oxide bonding layer comprises transparent and non-conductive oxide material; the first-color Micro-LED chips are blue flip-chip Micro-LED chips or green flip-chip Micro-LED chips; the second-color Micro-LED chips are green flip-chip Micro-LED chips or blue flip-chip Micro-LED chips, and the second-color Micro-LED chips are different from the first-color Micro-LED chips; and the third-color Micro-LED chips are red flip-chip Micro-LED chips. The light-emitting unit comprises three stacked layers, and the Micro-LED chips of different colors in the three layers do not overlap in the vertical direction. The third-color Micro-LED chip comprises, from top to bottom, an etching barrier layer, a first-type ohmic contact layer, a first-type extension layer, a first-type roughening layer, a first-type limiting layer, a multi-quantum well layer, a second-type limiting layer, a second-type extension layer, a second-type ohmic contact layer, a diffusion barrier layer, a passivation layer, a first-type electrode layer and a second-type electrode layer. 2.The Micro-LED display substrate of claim 1, wherein, ​ 3.The Micro-LED display substrate of claim 1, wherein, ​ 4.The Micro-LED display substrate of claim 1, wherein, The first primary color Micro-LED chip comprises, from bottom to top, an undoped GaN layer, a first type semiconductor layer, a multi-quantum well layer, an electron blocking layer, a second type semiconductor layer, a passivation layer, a first type electrode layer and a second type electrode layer. 5.The Micro-LED display substrate of claim 1, wherein, The second primary color Micro-LED chip comprises, from top to bottom, an undoped GaN layer, a first type semiconductor layer, a multi-quantum well layer, an electron blocking layer, a second type semiconductor layer, a passivation layer, a first type electrode layer and a second type electrode layer. 6.The Micro-LED display substrate of claim 1, wherein, The Micro-LED chip is rectangular, and the two ends of the rectangle are the first type electrode layer and the second type electrode layer of the chip.

7. The Micro-LED display substrate of claim 6, wherein, The width of the Micro-LED chip is 20 μm to 50 μm, and the length is 40 μm to 100 μm. 8.The Micro-LED display substrate of claim 1, wherein, The vacancy position is filled with a transparent insulating layer. 9.A method for manufacturing a Micro-LED display substrate, comprising: The method comprises the following steps: providing a first primary color LED wafer and a second primary color LED wafer, wherein the first primary color LED wafer comprises a plurality of first primary color Micro-LED chips, and the second primary color LED wafer comprises a plurality of second primary color Micro-LED chips; aligning and bonding the first surface of the first primary color LED wafer and the first surface of the second primary color LED wafer; stripping the substrate of the second surface of the second primary color LED wafer to form a combined wafer sheet of Micro-LED chips with two primary colors; providing a third primary color LED wafer, wherein the third primary color LED wafer comprises a plurality of third primary color Micro-LED chips; aligning and bonding the first surface of the third primary color LED wafer with the second surface of the second primary color LED wafer from which the substrate has been stripped; removing the substrate of the second surface of the third primary color LED wafer to form a combined wafer sheet of Micro-LED chips with three primary colors; cutting the combined wafer sheet of Micro-LED chips with three primary colors to form a Micro-LED display substrate; The Micro-LED display substrate includes a substrate of the first primary color Micro-LED chip and a light-emitting unit on the substrate of the first primary color Micro-LED chip, and the light-emitting unit includes three primary color Micro-LED chips arranged in an array after cutting of a Micro-LED combined wafer with three primary colors, at least two vacant positions being reserved between any adjacent Micro-LED chips of the same primary color for layout of Micro-LED chips of the other two primary colors; an oxide bonding layer is arranged between the first primary color Micro-LED chip and a second primary color Micro-LED chip, and between the second primary color Micro-LED chip and a third primary color Micro-LED chip, and the material of the oxide bonding layer includes a transparent and non-conductive oxide material; the first primary color Micro-LED chip is a blue light flip Micro-LED chip or a green light flip Micro-LED chip; the second primary color Micro-LED chip is a green light flip Micro-LED chip or a blue light flip Micro-LED chip, and the second primary color Micro-LED chip is different from the first primary color Micro-LED chip; and the third primary color Micro-LED chip is a red light flip Micro-LED chip. 10.The method of claim 9, wherein the method further comprises: forming a plurality of micro-LEDs on the substrate; and forming a plurality of micro-LEDs on the substrate. The first primary color Micro-LED chip, the second primary color Micro-LED chip and the third primary color Micro-LED chip do not overlap in the vertical direction.

11. The method of claim 9, wherein the method further comprises: The third primary color Micro-LED chip includes, in sequence from bottom to top, an etching barrier layer, a first type ohmic contact layer, a first type extension layer, a first type roughening layer, a first type confinement layer, a multiple quantum well layer, a second type confinement layer, a second type extension layer, a second type ohmic contact layer, a diffusion barrier layer, a passivation layer, a first type electrode layer and a second type electrode layer.

12. The method of claim 9, wherein the method further comprises: The first primary color Micro-LED chip includes, in sequence from bottom to top, an undoped GaN layer, a first type semiconductor layer, a multiple quantum well layer, an electron barrier layer, a second type semiconductor layer, a passivation layer, a first type electrode layer and a second type electrode layer.

13. The method of claim 9, wherein the method further comprises: The second primary color Micro-LED chip includes, in sequence from bottom to top, an undoped GaN layer, a first type semiconductor layer, a multiple quantum well layer, an electron barrier layer, a second type semiconductor layer, a passivation layer, a first type electrode layer and a second type electrode layer. 14.The method of claim 9, wherein the method further comprises: forming a plurality of micro-LEDs on the substrate; and forming a plurality of micro-LEDs on the substrate. The step of providing the first primary color LED wafer and the second primary color LED wafer includes: A first base color LED wafer is provided, dry etching is performed on the first base color LED wafer, and the etching is stopped on the substrate of the first base color LED wafer, thereby forming a plurality of first base color Micro-LED chips, and at least two vacant positions are reserved between adjacent first base color Micro-LED chips for layout of second base color Micro-LED chips and third base color Micro-LED chips; A second base color LED wafer is provided, dry etching is performed on the second base color LED wafer, and the etching is stopped on the substrate of the second base color LED wafer, thereby forming a plurality of second base color Micro-LED chips, and at least two vacant positions are reserved between adjacent second base color Micro-LED chips for layout of first base color Micro-LED chips and third base color Micro-LED chips; The step of providing a third base color LED wafer includes: A third base color LED wafer is provided, dry etching is performed on the third base color LED wafer, and the etching is stopped on the substrate of the third base color LED wafer, thereby forming a plurality of third base color Micro-LED chips, and at least two vacant positions are reserved between adjacent third base color Micro-LED chips for layout of first base color Micro-LED chips and second base color Micro-LED chips.

15. The method of claim 9, wherein the method further comprises: Before the step of performing alignment bonding of the first surface of the first base color LED wafer and the first surface of the second base color LED wafer, the following step is further included: A first lead wire is formed on the passivation layer of the first base color LED wafer, and the first type electrode layer and the second type electrode layer of the first base color Micro-LED chip are connected to the external contact points of the periphery of the light emitting unit through the first lead wire; A first oxide bonding layer is formed on the first surface of the first base color LED wafer on which the first lead wire is formed.

16. The method of claim 15, wherein the method further comprises: Before the step of performing alignment bonding of the first surface of the first base color LED wafer and the first surface of the second base color LED wafer, the following step is further included: A second lead wire is formed on the passivation layer of the second base color LED wafer, and the first type electrode layer and the second type electrode layer of the second base color Micro-LED chip are connected to the external contact points of the periphery of the light emitting unit through the second lead wire; A second oxide bonding layer is formed on the first surface of the second base color LED wafer on which the second lead wire is formed.

17. The method of claim 16, wherein the method further comprises: The step of performing alignment bonding of the first surface of the first base color LED wafer and the first surface of the second base color LED wafer includes: Chemical mechanical polishing is performed on the first oxide bonding layer as a first bonding surface; Chemical mechanical polishing is performed on the second oxide bonding layer as a second bonding surface; Activation solution is used to activate the first bonding surface and the second bonding surface, and alignment bonding is achieved under high temperature and high pressure.

18. The method of claim 17, wherein the method further comprises: Before the step of performing alignment bonding of the first surface of the third base color LED wafer and the second surface of the second base color LED wafer from which the substrate is peeled off, the following step is further included: forming a third lead line on the third passivation layer of the third base color LED wafer, and connecting the first type electrode layer and the second type electrode layer of the third base color Micro-LED chip to the external contact points of the periphery of the light emitting unit through the third lead line; forming a third oxide bonding layer on the first surface of the third base color LED wafer on which the third lead line is formed; forming a fourth oxide bonding layer on the second surface of the second base color LED wafer from which the substrate is stripped.

19. The method of claim 18, wherein the method further comprises: The step of aligning and bonding the first surface of the third base color LED wafer to the second surface of the second base color LED wafer from which the substrate is stripped includes: chemically and mechanically polishing the third oxide bonding layer as a third bonding surface; chemically and mechanically polishing the fourth oxide bonding layer as a fourth bonding surface; activating the third bonding surface and the fourth bonding surface with an activation solution, and realizing the aligning and bonding under high temperature and high pressure.

20. The method of claim 17 or 19, wherein the method further comprises: The activation solution includes a mixture of ammonia, hydrofluoric acid and hydrogen peroxide.

21. The method of claim 17 or 19, wherein the method further comprises: The surface roughness of all the oxide bonding layers after being chemically and mechanically polished is less than 5Å.

22. The method of claim 17 or 19, wherein the method further comprises: The thickness of all the oxide bonding layers is 3μm~5μm.

23. The method of claim 15 or 16 or 18, wherein the method further comprises: The forming process of the first lead line, the second lead line and the third lead line includes one of a stripping process and an electron beam evaporation process.

24. The method of claim 9, wherein the method further comprises: The length of the first base color Micro-LED chip, the second base color Micro-LED chip and the third base color Micro-LED chip is 40μm~100μm, and the width is 20μm~50μm.

25. The method of claim 9, wherein the method further comprises: The process of stripping the substrate of the second surface of the second base color LED wafer includes a laser irradiation stripping process. 26.The method of claim 9, wherein the method further comprises: The method of removing the substrate of the second surface of the third base color LED wafer includes an etching process, and the solution of the etching process includes a mixture of ammonia and hydrogen peroxide.

27. The preparation method of the Micro-LED display substrate according to claim 18, wherein, before the step of forming the first oxide bonding layer on the first surface of the first base color LED wafer on which the first lead line is formed, the method further includes filling a transparent insulating layer in the vacancy position of the first base color LED wafer; before the step of forming the second oxide bonding layer on the first surface of the second base color LED wafer on which the second lead line is formed, the method further includes filling a transparent insulating layer in the vacancy position of the second base color LED wafer; before the step of forming the third oxide bonding layer on the first surface of the third base color LED wafer on which the third lead line is formed, the method further includes filling a transparent insulating layer in the vacancy position of the third base color LED wafer.

28. A display screen, characterized by A driving panel, a Micro-LED display substrate as claimed in any one of claims 1~8 and a circuit, wherein the Micro-LED display substrate is connected to the driving panel through the circuit.

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