High-density micro-led array structure and preparation method thereof

Abstract

The application relates to a high-density Micro-LED array structure and a preparation method thereof. The structure comprises a driving substrate layer, a bonding layer for connecting an LED chip layer and the driving substrate layer, an n-layer LED chip layer stacked in a vertical substrate direction, a bonding layer for connecting the n-layer chips, and n>=2. The bonding layer is composed of an organic medium, a plurality of metal wall structures, and a plurality of metal electrodes. The organic medium realizes physical bonding connection between the chip layer and the driving substrate layer and between different chip layers. The chip electrodes are respectively electrically connected with the metal electrodes, the metal electrodes are electrically connected with the metal walls, and the metal walls realize electrical connection between the chips and between the chips and the driving circuit. The structure has reliable bonding connection, good electrical connection, and can realize micro-nanometer high-precision alignment in the chip preparation process. The metal walls can inhibit light crosstalk and reshape the light shape.

Description

Technical Field

[0001] This invention relates to the field of optoelectronics and information display technology, and in particular to a high-density Micro-LED array structure and its fabrication method. Background Technology

[0002] Display technology is my country's third largest manufacturing sector. From CRT (cathode ray tube) displays to LCD (liquid crystal display) and OLED (organic light-emitting diode) displays, the next generation of display technology—Highly Integrated Semiconductor Information Display (HISID)—will develop towards high integration, ultra-high resolution, immersive high interactivity, and true 3D. Interactive, true 3D future information displays demand high density and high integration of light sources. Compared to traditional LCD and OLED displays, Micro-LEDs, inorganic light-emitting devices with light-emitting units smaller than 50μm, will play an irreplaceable role in future display technologies due to their advantages of lower power consumption, wider color gamut, longer lifespan, faster response speed, and stronger thermal stability. Micro-LED arrays with pixel sizes in the micrometer range can not only serve as high-density light sources but also integrate detectors to sense and collect real-time spatial 3D environment and human motion information to achieve high interactivity. The high-speed response of Micro-LEDs will lay a solid foundation for high-speed, long-distance visible light communication. In addition, Micro-LED can also be widely used in high-performance display devices, AR (Augmented Reality), VR (Virtual Reality), smartphones / watches, high-end TVs, automotive / airborne displays, flexible displays, and transparent displays.

[0003] For Micro-LED to achieve absolute dominance in future displays, it needs to overcome a series of challenges, especially in mass transfer technology for full-color applications and bonding between Micro-LED chips and driving substrates. For high-density (ppi>1000) Micro-LED displays, active-matrix technology is typically used, with the Micro-LED chip and driving substrate achieving electrical and physical connections through flip-chip bonding. In traditional flip-chip bonding, metal bumps simultaneously provide electrical and physical connections between chip layers and between chip layers and the driving substrate. This technology typically suffers from the following problems: 1. Unstable and non-uniform metal bump structure. The high temperature and pressure conditions during high-density bump bonding can cause expansion, deformation, and defects in the metal bumps; inconsistencies in the height and shape of the metal bumps during evaporation and reflow processes; furthermore, chip warpage caused by epitaxial wafer peeling also affects the height uniformity of the metal bumps. The stability, integrity, and uniformity (especially height) of the metal bump structure affect the physical and electrical connections between the chip and the driving substrate. 2. Alignment accuracy issues in the overlay process. In mass transfer technology applied to full-color displays, the pick-and-place operation of chips and the connection between Micro-LED chip pixels and driving substrate pixels require extremely high alignment accuracy. In particular, for Micro-LED chips used in AR / VR technology, the period of the light-emitting unit is less than 10μm, requiring the alignment accuracy of the metal bumps to be below the micrometer level. 3. Optical crosstalk from side-emitting chips. The spacing between high-density Micro-LED chips is only on the micrometer level. Light emitted from the side of the chip will interfere with the emitted light from adjacent Micro-LED chips, severely affecting the display's contrast and color purity. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a high-density Micro-LED array structure and its fabrication method. The structure has reliable bonding and good electrical connection, and the chip fabrication process can achieve high-precision alignment at the micro-nano level. The metal wall can suppress optical crosstalk and shape the emitted light.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a high-density Micro-LED array structure, comprising a driving substrate layer, a bonding layer for connecting LED chip layers and the driving substrate layer, n LED chip layers stacked along a direction perpendicular to the substrate, and a bonding layer for connecting the n chip layers, where n≥2; the bonding layer is composed of an organic dielectric, multiple sets of metal wall structures, and multiple metal electrodes; the organic dielectric realizes the bonding connection between the chip layers and the driving substrate layer, and between different chip layers; the chip electrodes are electrically connected to the metal electrodes respectively, the metal electrodes are electrically connected to the metal walls, and the metal walls realize the electrical connection between the chips.

[0006] In a preferred embodiment, the driving substrate layer is a substrate having one or more of the following: CMOS circuits, thin film transistor circuits, transistor circuit matrices, and IC circuit matrices; the substrate itself is a glass substrate, silicon substrate, sapphire substrate, PCB, quartz substrate, and flexible organic material substrate.

[0007] In a preferred embodiment, the organic media constituent material comprises a high-strength organic polymer and has a thickness of 0.1-20 μm.

[0008] In a preferred embodiment, the metal electrode is electrically connected to the chip electrode and extends to the side of the chip, and the metal wall is connected to the metal electrode extending to the side of the chip.

[0009] In a preferred embodiment, the multiple sets of metal walls surround the chip, and the electrical connections between the chips and between the chip and the driving substrate are achieved through the electrical connection of metal electrodes to the same set of metal walls.

[0010] In a preferred embodiment, the exterior of the metal wall is provided with a metallic material; the metallic material is one or more of copper, nickel, chromium, indium, tin, silver, gold, tungsten, titanium, and platinum, or a mixture or alloy thereof.

[0011] In a preferred embodiment, the metal electrode is one or more of ITO, graphene, MoS2, copper, nickel, chromium, indium, tin, silver, gold, tungsten, titanium, and platinum, or a mixture or alloy thereof.

[0012] In a preferred embodiment, multiple sets of metal walls are distributed around each Micro-LED chip and electrically connected to the corresponding Micro-LED chip electrodes through metal electrodes; the multiple sets of metal walls are distributed around multiple sets of electrodes on the driving substrate and electrically connected to the corresponding electrodes on the driving substrate through metal electrodes.

[0013] In a preferred embodiment, the metal walls distributed around the Micro-LED chip suppress optical crosstalk by reflecting the emitted light and shaping the emitted light beam; the Micro-LED chip is a single-layer Micro-LED chip with any emission color, or a multi-layer Micro-LED chip with different emission colors.

[0014] This invention also provides a method for fabricating a high-density Micro-LED array structure. The method involves fabricating the aforementioned high-density Micro-LED array structure by bonding an LED epitaxial wafer to a driving substrate and multiple LED epitaxial wafers together using an organic medium. Then, a Micro-LED chip array, a metal wall, and metal electrodes are fabricated based on alignment marks on the previous layer, aligning the new chip array with the previous layer. The method for fabricating the metal wall includes, but is not limited to, one or more of the following: electroplating, electroless plating, atomic layer deposition (ALD), chemical vapor deposition (CVD), thermal evaporation, electron beam evaporation, or magnetron sputtering.

[0015] Compared with existing technologies, this invention has the following advantages: In this structure, the physical bonding connections between chips and between chips and the driving circuit are achieved using organic media, while the electrical connections are achieved using metal walls and metal electrodes. This invention separates physical bonding connections from electrical connections, reducing the requirements for bump uniformity, integrity, and structural stability in traditional metal bump bonding; the metal walls can suppress optical crosstalk by reflecting side-emitted light, improving the light extraction efficiency of the light-emitting device; the vertical stacking of Micro-LED chips of different emission colors can improve space utilization, further increase pixel density, and provide space for integrated photoelectric sensors. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the Micro-LED structure according to a preferred embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the driving substrate according to a preferred embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the electrical connection between a Micro-LED chip with the same polarity and a driving substrate according to a preferred embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of the electrical connection between a Micro-LED chip with opposite polarities and a driving substrate according to a preferred embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram of the electrical connection between the Micro-LED chip and the driving substrate according to a preferred embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] like Figures 1 to 5 As shown, Embodiment 1 of the present invention provides a high-density Micro-LED array structure, including a driving substrate layer, a bonding layer for connecting LED chip layers and the driving substrate layer, n LED chip layers stacked in the direction perpendicular to the substrate, and a bonding layer for connecting the n chip layers, where n ≥ 2. The bonding layer consists of an organic dielectric, multiple sets of metal wall structures, and multiple metal electrodes. The organic dielectric enables physical bonding connections between the chip layers and the driving substrate layer, and between different chip layers; the chip electrodes are electrically connected to the metal electrodes, the metal electrodes are electrically connected to the metal walls, and the metal walls enable electrical connections between the chips. In this embodiment, n = 3, meaning that 3 chip layers and the driving substrate layer are connected through the organic dielectric, metal walls, and metal electrodes.

[0025] The driving substrate is a substrate having one or more of the following: CMOS circuits, thin-film transistor (TFT) circuits, transistor circuit matrices, and IC circuit matrices. The substrate itself can be one or more of the following: glass substrate, silicon substrate, sapphire substrate, PCB, quartz substrate, and flexible organic material substrate.

[0026] The organic medium is composed of, but is not limited to, one or a mixture of, high-strength organic polymers such as BCB and SU8. The organic medium enables physical bonding between the chip layer and the driving substrate layer, and between the chip layers, and has a thickness of 0.1-20 μm.

[0027] like Figure 2As shown, after the LED epitaxial wafer is bonded to the driving substrate layer and the multilayer LED epitaxial wafers as a whole using an organic medium, a Micro-LED chip array, metal wall, and metal connection electrodes are fabricated according to the alignment marks on the previous layer, which can achieve high-precision alignment between the new layer of chip array and the previous layer of chip array. This embodiment provides a method for large-scale, high-precision, and high-yield high-density full-color Micro-LED display devices. First, the LED epitaxial wafers on the substrate are cut into small-sized epitaxial wafers, such as 0.5-1 inches, the size of the Micro-LED display screen. The LED epitaxial wafers on the substrate are bonded to a temporary substrate using an organic medium, and the sapphire substrate is peeled off. A layer of adhesive organic medium is covered on the driving substrate layer to bond the LED epitaxial wafers to the driving substrate, and the temporary substrate is peeled off. Figure 2 A Micro-LED chip array is fabricated by marking on a driving substrate, and metal electrodes and metal wall structures for the Micro-LED chip array are grown. A layer of adhesive organic dielectric is filled and coated onto the first layer of the Micro-LED chip array. A second layer of small-sized LED epitaxial wafer is bonded to the first layer of chips. A second layer of Micro-LED chip array is fabricated according to the markings on the first layer of chips, and metal electrodes and metal wall structures are grown on top of the first layer of metal walls. This process is repeated to fabricate multilayer Micro-LED chip arrays and grow metal electrodes and metal walls.

[0028] like Figure 1 As shown, in this embodiment, the metal electrode is electrically connected to the chip electrode and extends to the side of the chip, and the metal wall is connected to the metal electrode extending to the side of the chip.

[0029] Multiple sets of metal walls surround the chip. Electrical connections between chips and between the chip and the driving substrate are achieved through electrical connections between metal electrodes and the same set of metal walls. These metal walls only provide electrical connections, reducing the strength requirements for the metal walls. Figure 1 As shown in this embodiment, in the Micro-LED chip, four sets of metal walls are plated at the four corners, and the central cross part is the light-emitting area of ​​the Micro-LED chip.

[0030] The electrodes on the driving substrate include, but are not limited to, circular bumps, square bumps, or other structures.

[0031] The method for preparing the metal wall includes, but is not limited to, one or more of the following: electroplating, electroless plating, thermal evaporation, atomic layer deposition (ALD), chemical vapor deposition (CVD), electron beam evaporation, or magnetron sputtering.

[0032] The metal wall may be composed of a metallic material, or the metallic material may cover the entire or part of the exterior of any material, wherein the metallic material is one or more of copper, nickel, chromium, indium, tin, silver, gold, tungsten, titanium, and platinum, or a mixture or alloy thereof.

[0033] The metal electrode is one or more of ITO, graphene, MoS2, copper, nickel, chromium, indium, tin, silver, gold, tungsten, titanium, and platinum, or a mixture or alloy thereof.

[0034] The multiple sets of metal walls are distributed around each Micro-LED chip and electrically connected to the corresponding Micro-LED chip electrodes via metal electrodes; simultaneously, the multiple sets of metal walls surround multiple sets of electrodes on the driving substrate and are electrically connected to the corresponding electrodes on the driving substrate via metal electrodes. Figure 3 In Embodiment 1, the cathodes or anodes of each layer of Micro-LED chips and a set of electrodes on the driving substrate are connected to the same set of metal walls via metal electrodes, achieving a common cathode or common anode electrical connection; the anodes or cathodes of each layer of Micro-LED chips are connected to electrodes on the driving substrate via different sets of metal walls, and the chips of each layer form a parallel stacked structure with the same polarity. Or as... Figure 4 As shown in Embodiment 2, each layer of Micro-LED chips consists of at least two layers of Micro-LED chips with different emitting colors connected in parallel and stacked vertically with opposite polarities.

[0035] The metal walls distributed around the Micro-LED chip can suppress optical crosstalk by reflecting the emitted light and shape the emitted light beam to improve light extraction efficiency.

[0036] The Micro-LED chip can be a single-layer Micro-LED chip with any emission color, or a multi-layer Micro-LED chip with different emission colors. For example... Figure 3 , 4 As shown in Embodiments 1 and 2, the full-color Micro-LED display device is composed of red, green and blue primary colors, and the three groups of red, green and blue chips form a parallel vertical stacked structure.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, 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 scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for fabricating a high-density Micro-LED array structure, characterized in that, The high-density Micro-LED array structure includes a driving substrate layer, a bonding layer for connecting LED chip layers and the driving substrate layer, n LED chip layers stacked along a direction perpendicular to the substrate, and a bonding layer for connecting the n chip layers, where n ≥ 2. The bonding layer consists of an organic dielectric, multiple sets of metal wall structures, and multiple metal electrodes. The organic dielectric enables bonding connections between the chip layers and the driving substrate layer, and between different chip layers. The chip electrodes are electrically connected to the metal electrodes, and the metal electrodes are electrically connected to the metal walls. The metal walls enable electrical connections between the chips. The multiple sets of metal walls are distributed around the chips, and the electrical connections between the chips and between the chips and the driving substrate are achieved through... Electrical connection between metal electrodes and the same set of metal walls is achieved; multiple sets of metal walls are distributed around each Micro-LED chip, and are electrically connected to the electrodes of the corresponding Micro-LED chip through metal electrodes; the multiple sets of metal walls surround multiple sets of electrodes distributed around the driving substrate, and are electrically connected to the corresponding electrodes of the driving substrate through metal electrodes; the metal walls distributed around the Micro-LED chip suppress optical crosstalk by reflecting the emitted light and perform beam shaping on the emitted light; the Micro-LED chip is a single-layer Micro-LED chip with arbitrary emission color, or a multi-layer Micro-LED chip with different emission colors. The fabrication method includes: covering a driving substrate layer with an adhesive organic medium, bonding an LED epitaxial wafer to the driving substrate, fabricating a Micro-LED chip array according to the markings on the driving substrate, and growing metal electrodes and metal wall structures for the Micro-LED chip array; filling and covering a first layer of the Micro-LED chip array with an adhesive organic medium, bonding a second layer of the LED epitaxial wafer to the first layer of the chip, fabricating a second layer of the Micro-LED chip array according to the markings on the first layer of the chip, and growing metal electrodes and metal wall structures on the basis of the first layer of metal walls; repeating this process to fabricate a multilayer Micro-LED chip array and grow metal electrodes and metal walls.

2. The method for fabricating a high-density Micro-LED array structure according to claim 1, characterized in that, The driving substrate layer is a substrate having one or more of CMOS circuits and thin film transistor circuits; the substrate itself is a mixture of one or more of glass substrates, silicon substrates, sapphire substrates, quartz substrates, and flexible organic material substrates.

3. The method for fabricating a high-density Micro-LED array structure according to claim 1, characterized in that, The organic medium material comprises a high-strength organic polymer and has a thickness of 0.1-20 μm.

4. The method for fabricating a high-density Micro-LED array structure according to claim 3, characterized in that, The metal electrode is electrically connected to the chip electrode and extends to the side of the chip, and the metal wall is connected to the metal electrode extending to the side of the chip.

5. The method for fabricating a high-density Micro-LED array structure according to claim 1, characterized in that, The exterior of the metal wall is made of a metallic material; the metallic material is one or more of copper, nickel, chromium, indium, tin, silver, gold, tungsten, titanium, and platinum.

6. The method for fabricating a high-density Micro-LED array structure according to claim 1, characterized in that, The metal electrode is one or more of ITO, graphene, MoS2, copper, nickel, chromium, indium, tin, silver, gold, tungsten, titanium, and platinum.

7. The method for fabricating a high-density Micro-LED array structure according to claim 1, characterized in that, The method for preparing the metal wall includes one or more of the following: electroplating, electroless plating, ALD, CVD, electron beam evaporation, or magnetron sputtering.

8. A high-density Micro-LED array structure, characterized in that... The high-density Micro-LED array structure is prepared using the preparation method described in any one of claims 1 to 7.

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