Vertically stacked Micro-LED full-color micro display

Abstract

The invention, which belongs to the technical field of Micro-LED display, provides a vertically stacked Micro-LED full-color micro-display comprising a substrate unit, a pixel stacking unit and a connecting unit. The plurality of pixel stacking units are vertically stacked on the substrate unit, and electrical connection and mechanical connection are realized through the connecting units; each pixel stacking unit comprises a plurality of sub-pixel structures with different light emitting colors, each sub-pixel structure is provided with an anode contact part and a cathode contact part, the anode contact parts are connected with the anodes of the substrate units through the connecting units, and the cathode contact parts are connected with the cathodes of the substrate units through the connecting units. The problems that in an existing Micro-LED full-color display technology, large-amount transfer precision and yield are difficult to consider at the same time, color conversion efficiency is low, light attenuation is serious, a traditional vertical stacking technology is complex, bonding layer damage and performance degradation are likely to be caused are solved, and high-brightness wide-color-gamut display, efficient production and large-scale mass production are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of Micro-LED display, and particularly to a vertically stacked Micro-LED full-color microdisplay. Background Art

[0002] As a new generation of display technology, Micro-LED display technology has shown great application potential in many fields such as consumer electronics, automotive electronics, and public display, becoming a research hotspot and development direction in the display field, due to its significant advantages such as high brightness, high contrast, low power consumption, and long lifespan. In the manufacturing process of Micro-LED full-color microdisplays, the efficient integration of sub-pixels with different emission colors and stable electrical and mechanical connections are key links, directly affecting the performance and manufacturing cost of the display.

[0003] At present, the traditional Micro-LED full-color display technology mainly adopts the method of horizontally arranging RGB pixels, that is, realizing full-color display by arranging and combining Micro-LED chips of red, green, and blue colors on a plane. This method has some insurmountable problems. Specifically, it includes: 1) Since each red, green, and blue sub-pixel needs to occupy a certain plane space, in order to ensure that each sub-pixel can be independently driven and work normally, a certain distance needs to be reserved between sub-pixels, which results in a limited number of pixels that can be arranged in a limited display area and makes it difficult to achieve a higher pixel density. In application scenarios with extremely high requirements for display accuracy, such as virtual reality (VR), augmented reality (AR) devices, etc., the traditional horizontal arrangement method cannot meet the requirements of high-resolution display, and users will obviously perceive the graininess of the picture during use, affecting the visual experience. 2) The traditional horizontal arrangement method requires separate mass transfer and bonding operations for Micro-LED chips of red, green, and blue colors. The mass transfer technology requires tens of thousands or even more tiny chips to be accurately transferred to the target substrate in a short time, and the transfer accuracy and chip yield need to be ensured, which places extremely high requirements on equipment and processes. At the same time, due to the differences in chip materials and characteristics of different colors, it is necessary to optimize the bonding process parameters for each color of chip separately during the bonding process, increasing the complexity and difficulty of the process, resulting in low production efficiency and a significant increase in manufacturing costs. 3) In the horizontally arranged RGB pixel structure, since the red, green, and blue sub-pixels are arranged side by side on a plane, when light emits from the sub-pixels, crosstalk and light mixing are likely to occur between different colors of light. Especially when the pixel pitch is small, this light mixing problem will be more serious, resulting in a decrease in the color accuracy and clarity of the display picture, and color deviation and blurring phenomena, affecting the display quality of the display. 4) The space in the vertical direction of the horizontally arranged RGB pixel structure is not fully utilized, resulting in a relatively large thickness of the entire display, which is not conducive to the realization of the thin and light design of the display device. In the current trend of the consumer electronics market with increasing requirements for product thinness, lightness, and portability, the traditional horizontally arranged Micro-LED full-color display is at a disadvantage in the market competition. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a vertically stacked Micro-LED full-color microdisplay, which solves the problems in the existing Micro-LED full-color display technology that it is difficult to balance the mass transfer accuracy and yield, the color conversion efficiency is low, the light decay is serious, the traditional vertical stacking process is complex and easy to cause damage and performance degradation of the bonding layer, etc., and realizes high-brightness wide-color gamut display, efficient production, and large-scale mass production.

[0005] To achieve the above purpose, the present invention provides the following solutions: A vertical stacked Micro-LED full-color microdisplay, comprising a substrate unit, a pixel stacking unit, and a connection unit; a plurality of the pixel stacking units are vertically stacked on the substrate unit, and electrical connection and mechanical connection are achieved through the connection unit; the pixel stacking unit includes sub-pixel structures of multiple different light-emitting colors, and each sub-pixel structure has an anode contact part and a cathode contact part. The anode contact part is connected to the anode of the substrate unit through the connection unit, and the cathode contact part is connected to the cathode of the substrate unit through the connection unit.

[0006] Preferably, the substrate unit is a driving substrate, and a driving substrate anode metal, a first sub-pixel anode, a second sub-pixel anode, a third sub-pixel anode, and a driving substrate cathode are arranged on the driving substrate; the driving substrate anode metal is respectively connected to the first sub-pixel anode, the second sub-pixel anode, and the third sub-pixel anode for providing anode driving signals for different sub-pixels, and the driving substrate cathode is used for receiving the cathode current of the sub-pixels.

[0007] Preferably, a plurality of the pixel stacking units are composed of a vertically stacked RGB pixel array, and the vertically stacked RGB pixel array is driven in a common cathode and anode addressing manner; the vertically stacked RGB pixel array includes a plurality of vertically stacked RGB pixels, and each vertically stacked RGB pixel includes a first sub-pixel, a second sub-pixel, and a third sub-pixel stacked in sequence along the vertical direction, in a stepped shape; the quarter and three-quarter regions corresponding to the second sub-pixel and the third sub-pixel are both removed to open light-emitting windows for the first sub-pixel and the second sub-pixel; The first sub-pixel is a sub-pixel that emits red light at the bottom layer and includes a red light LED epitaxial layer; the second sub-pixel is a sub-pixel that emits green light in the middle layer and includes a green light LED epitaxial layer; the third sub-pixel is a sub-pixel that emits blue light at the top layer and includes a blue light LED epitaxial layer; the green light LED epitaxial layer and the blue light LED epitaxial layer are integrally bonded to a blue-green light LED substrate through a third bonding layer to form a blue-green light LED epitaxial wafer, and the blue-green light LED epitaxial wafer is integrally bonded to the red light LED epitaxial wafer through a second bonding layer. The red light LED epitaxial wafer is composed of the red light LED epitaxial layer and a red light LED substrate. After peeling off the red light LED substrate, a vertically stacked LED is formed; the area ratio of the light-emitting windows of the first sub-pixel, the second sub-pixel, and the third sub-pixel is 1:2:1.

[0008] Preferably, the connection unit includes an anode connection structure, a cathode connection structure, a bonding layer, and bonding leads; the anode connection structure includes a first anode connection structure, a second anode connection structure, and a third anode connection structure; the cathode connection structure includes a first cathode ohmic contact layer, a second cathode ohmic contact layer, a third cathode ohmic contact layer, a cathode interconnection structure, and a sub-pixel common cathode pad; the bonding layer includes a first bonding layer, a second bonding layer, and a third bonding layer.

[0009] Preferably, one end of the first anode connection structure is connected to the first anode ohmic contact layer of the p-type contact surface of the first sub-pixel, and the other end is connected to the first sub-pixel anode on the driving substrate, realizing the anode signal transmission and mechanical connection between the first sub-pixel and the driving substrate; one end of the second anode connection structure is connected to the second anode ohmic contact layer of the p-type contact surface of the second sub-pixel, and the other end is connected to the second sub-pixel anode on the driving substrate; one end of the third anode connection structure is connected to the third anode ohmic contact layer of the p-type contact surface of the third sub-pixel, and the other end is connected to the third sub-pixel anode on the driving substrate; the first anode connection structure, the second anode connection structure, and the third anode connection structure are all formed by electroplating and filling in the through holes.

[0010] Preferably, the materials of the first anode ohmic contact layer, the second anode ohmic contact layer, and the third anode ohmic contact layer are low work function metals and their material combinations or transparent conductive oxides, respectively forming ohmic contacts with the p-type contact surfaces of the first sub-pixel, the second sub-pixel, and the third sub-pixel to reduce the contact resistance.

[0011] Preferably, the first cathode ohmic contact layer forms an ohmic contact with the n-type contact surface of the first sub-pixel, the second cathode ohmic contact layer forms an ohmic contact with the n-type contact surface of the second sub-pixel, and the third cathode ohmic contact layer forms an ohmic contact with the n-type contact surface of the third sub-pixel; the first cathode ohmic contact layer, the second cathode ohmic contact layer, and the third cathode ohmic contact layer are connected together through the cathode interconnection structure and led to the sub-pixel common cathode pad; the cathode interconnection structure is electrically insulated from the n-type contact surfaces of the first sub-pixel, the second sub-pixel, and the third sub-pixel through the passivation layer.

[0012] Preferably, the material combination of the first cathode ohmic contact layer is one of Ti / Al / Ti / Au, Cr / Au, and the material combinations of the second cathode ohmic contact layer and the third cathode ohmic contact layer are one of Ti / Al, Ti / Al / Ni / Au, Ti / Al / Au.

[0013] Preferably, one end of the bonding lead is connected to the sub-pixel common cathode pad, and the other end is connected to the driving substrate cathode on the driving substrate, realizing the electrical connection between the sub-pixel cathode and the driving substrate cathode, and enabling the cathode current of the sub-pixel to flow back to the driving substrate.

[0014] Preferably, the first bonding layer is used to bond the vertically stacked LEDs to the driving substrate; the second bonding layer is used to perform a full-surface bonding of the blue-green light-emitting diode (LED) epitaxial wafer and the red LED epitaxial wafer; the third bonding layer is used to perform a full-surface bonding of the green LED epitaxial layer and the blue LED epitaxial layer to the blue-green LED substrate. The second bonding layer and the third bonding layer are formed by a full-surface bonding process to improve the mechanical connection stability between layers. The first bonding layer and the embedded anode connection structure are formed by alignment bonding to achieve anode addressing connection between the vertically stacked LEDs and the driving substrate.

[0015] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: (1) By vertically stacking the RGB tri-color Micro-LED epitaxial layers, the present invention realizes a native wide color gamut and high-brightness direct emission without color conversion materials, thereby significantly improving the light-emitting efficiency. This design avoids the problems of low photon conversion efficiency and color gamut compression caused by the color conversion layer in traditional photoluminescence schemes.

[0016] (2) The present invention adopts a wafer-level bonding technology to perform a full-surface bonding of the RGB tri-color LED epitaxial layers, and then only needs a single alignment bonding and a driving substrate to achieve electrical interconnection, which simplifies the manufacturing process and avoids the time-consuming steps of transferring one by one in the mass transfer technology, thereby significantly reducing the manufacturing cost and improving the production efficiency.

[0017] (3) The present invention can complete the integration of the three primary color pixels and the driving substrate through a single alignment bonding, reducing problems such as thermal stress damage of the bonded layer, accumulation of interface defects, and deterioration of ohmic contact performance that may occur in the multi-step alignment bonding process, effectively improving the optoelectronic performance of the microdisplay device and the yield of large-scale production. In addition, the design that the red LED pixels are located at the bottom layer helps to reduce the surface damage caused by etching, thereby reducing the small-size effect of the red LEDs and further improving the yield.

[0018] (4) The vertically stacked Micro-LED full-color microdisplay provided by the present invention reduces the process complexity and is compatible with the wafer-level processing mode, making it easier to achieve large-scale mass production. This simplified process flow and high-yield production method provide a reliable technical path for the commercialization and large-scale application of Micro-LED displays. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 Cross-sectional view in the A-B direction of the overall structure provided for a vertical stacked Micro-LED full-color microdisplay of the present invention; Figure 2 Cross-sectional view in the C-D direction of the overall structure provided for a vertical stacked Micro-LED full-color microdisplay of the present invention; Figure 3 For Figure 1 Cross-sectional view in the A-B direction of the vertical stacked RGB pixel array in Figure 4 For Figure 2 Cross-sectional view in the C-D direction of the vertical stacked RGB pixel array in Figure 5 Top view of the vertical stacked RGB pixel array provided for a vertical stacked Micro-LED full-color microdisplay of the present invention; Figure 6 Schematic structural diagram of an infrared LED epitaxial wafer provided in Embodiment 1 of the present invention; Figure 7 Schematic structural diagram of a blue-green LED epitaxial wafer provided in Embodiment 1 of the present invention; Figure 8 Schematic structural diagram of a vertical stacked LED provided in Embodiment 1 of the present invention.

[0021] Explanation of reference numerals: 1. Driving substrate; 2. First sub-pixel; 3. Second sub-pixel; 4. Third sub-pixel; 5. First bonding layer; 6. Second bonding layer; 7. Third bonding layer; 8. First anode ohmic contact layer; 9. Second anode ohmic contact layer; 10. Third anode ohmic contact layer; 11. First anode connection structure; 12. Second anode connection structure; 13. Third anode connection structure; 14. First cathode ohmic contact layer; 15. Second cathode ohmic contact layer; 16. Third cathode ohmic contact layer; 17. Passivation layer; 18. Driving substrate anode metal; 19. First sub-pixel anode; 20. Second sub-pixel anode; 21. Third sub-pixel anode; 22. Cathode interconnection structure; 23. Driving substrate cathode; 24. Bonding lead; 25. Sub-pixel common cathode pad; 26. Red LED epitaxial layer; 27. Green LED epitaxial layer; 28. Blue LED epitaxial layer; 29. Blue-green LED substrate; 30. Red LED substrate; 31. Vertically stacked LED; 32. Vertically stacked RGB pixel; 33. Red LED epitaxial wafer; 34. Blue-green LED epitaxial wafer; 35. Vertically stacked RGB pixel array. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0024] Embodiment 1 As Figure 1 and Figure 2 shown, the present invention provides a vertically stacked Micro-LED full-color microdisplay, including a substrate unit, a pixel stacking unit, and a connection unit; a plurality of pixel stacking units are vertically stacked on the substrate unit, and electrical connection and mechanical connection are realized through the connection unit; the pixel stacking unit includes a plurality of sub-pixel structures with different light-emitting colors, and each sub-pixel structure has an anode contact part and a cathode contact part. The anode contact part is connected to the anode of the substrate unit through the connection unit, and the cathode contact part is connected to the cathode of the substrate unit through the connection unit. This structural design realizes the integration of sub-pixels with different light-emitting colors in the vertical direction. Compared with the traditional horizontal arrangement method, it improves the pixel density, reduces the light crosstalk and color mixing phenomenon, and improves the color accuracy and clarity of the display screen; at the same time, the vertically stacked structure makes full use of the vertical space, which is beneficial to realizing the thinning of the display device.

[0025] Referring to Figure 3 、 Figure 4 and Figure 5 , the substrate unit is the driving substrate 1, on which there are a driving substrate anode metal 18, a first sub-pixel anode 19, a second sub-pixel anode 20, a third sub-pixel anode 21, and a driving substrate cathode 23; the driving substrate anode metal 18 is respectively connected to the first sub-pixel anode 19, the second sub-pixel anode 20, and the third sub-pixel anode 21, and is used to provide anode driving signals for different sub-pixels, and the driving substrate cathode 23 is used to receive the cathode current of the sub-pixels. This design provides stable driving signals for each sub-pixel, ensures the normal light emission of the sub-pixels, realizes the independent control of the light emission of different color sub-pixels, and thus can accurately adjust the color and brightness of the display screen.

[0026] The multiple pixel stacking units are composed of a vertically stacked RGB pixel array 35, and the vertically stacked RGB pixel array 35 is driven in a common cathode and anode addressing manner; the vertically stacked RGB pixel array 35 includes a plurality of vertically stacked RGB pixels 32, and each vertically stacked RGB pixel 32 includes a first sub-pixel 2, a second sub-pixel 3, and a third sub-pixel 4 stacked in sequence along the vertical direction, showing a stepped shape; the quarter and three-quarter regions corresponding to the second sub-pixel 3 and the third sub-pixel 4 are both removed to open light-emitting windows for the first sub-pixel 2 and the second sub-pixel 3; Referring to Figure 8 , the first sub-pixel 2 is a sub-pixel that emits red light at the bottom layer and includes a red light LED epitaxial layer 26; the second sub-pixel 3 is a sub-pixel that emits green light in the middle layer and includes a green light LED epitaxial layer 27; the third sub-pixel 4 is a sub-pixel that emits blue light at the top layer and includes a blue light LED epitaxial layer 28; the green light LED epitaxial layer 27 and the blue light LED epitaxial layer 28 are integrally bonded to the blue-green light LED substrate 29 through a third bonding layer 7 to form a blue-green light LED epitaxial wafer 34, and the blue-green light LED epitaxial wafer 34 is integrally bonded to the red light LED epitaxial wafer 33 through a second bonding layer 6. The red light LED epitaxial wafer 33 is composed of a red light LED epitaxial layer 26 and a red light LED substrate 30. After peeling off the red light LED substrate 30, a vertically stacked LED 31 is formed; the area ratio of the light-emitting windows of the first sub-pixel 2, the second sub-pixel 3, and the third sub-pixel 4 is 1:2:1. Through this vertical stacking and light-emitting window design, the spectral separation and spatial multiplexing of the RGB three primary colors are realized. Without color conversion materials, direct light emission with a native wide color gamut and high brightness can be achieved, improving the light-emitting efficiency; the integral bonding process reduces the process steps, lowers the cost, and improves the yield compared with the mass transfer technology; the red light LED pixel is located at the bottom layer, reducing the small-size effect of the red light LED caused by surface damage during etching, and further improving the display performance and product yield.

[0027] The connection unit includes an anode connection structure, a cathode connection structure, a bonding layer, and bonding leads 24; the anode connection structure includes a first anode connection structure 11, a second anode connection structure 12, and a third anode connection structure 13; the cathode connection structure includes a first cathode ohmic contact layer 14, a second cathode ohmic contact layer 15, a third cathode ohmic contact layer 16, a cathode interconnection structure 22, and a sub-pixel common cathode pad 25; the bonding layer includes a first bonding layer 5, a second bonding layer 6, and a third bonding layer 7. The connection unit ensures stable electrical and mechanical connections between each sub-pixel and the driving substrate 1. The anode connection structure and the cathode connection structure achieve signal transmission and current loops, enabling the sub-pixels to emit light normally, and it is a key structure for realizing full-color display of the microdisplay.

[0028] One end of the first anode connection structure 11 is connected to the first anode ohmic contact layer 8 on the p-type contact surface of the first sub-pixel 2, and the other end is connected to the first sub-pixel anode 19 on the driving substrate 1, realizing the anode signal transmission and mechanical connection between the first sub-pixel 2 and the driving substrate 1; one end of the second anode connection structure 12 is connected to the second anode ohmic contact layer 9 on the p-type contact surface of the second sub-pixel 3, and the other end is connected to the second sub-pixel anode 20 on the driving substrate 1; one end of the third anode connection structure 13 is connected to the third anode ohmic contact layer 10 on the p-type contact surface of the third sub-pixel 4, and the other end is connected to the third sub-pixel anode 21 on the driving substrate 1; the first anode connection structure 11, the second anode connection structure 12, and the third anode connection structure 13 are all formed by electroplating and filling in through holes. This connection method ensures that the anode signal can be efficiently transmitted to each sub-pixel, provides stable driving for the light emission of the sub-pixels, and at the same time, the mechanical connection enhances the bonding strength between the sub-pixels and the driving substrate 1, ensuring the stability of the device during use.

[0029] The materials of the first anode ohmic contact layer 8, the second anode ohmic contact layer 9, and the third anode ohmic contact layer 10 are low work function metals and their material combinations or transparent conductive oxides, forming ohmic contacts with the p-type contact surfaces of the first sub-pixel 2, the second sub-pixel 3, and the third sub-pixel 4 respectively to reduce the contact resistance. The low contact resistance reduces the energy loss during signal transmission, improves the electron injection efficiency, enables the sub-pixels to emit light more efficiently, and enhances the light emission performance and energy efficiency of the microdisplay.

[0030] The first cathode ohmic contact layer 14 forms an ohmic contact with the n-type contact surface of the first sub-pixel 2, the second cathode ohmic contact layer 15 forms an ohmic contact with the n-type contact surface of the second sub-pixel 3, and the third cathode ohmic contact layer 16 forms an ohmic contact with the n-type contact surface of the third sub-pixel 4; the first cathode ohmic contact layer 14, the second cathode ohmic contact layer 15, and the third cathode ohmic contact layer 16 are connected together through the cathode interconnection structure 22 and led to the sub-pixel common cathode pad 25; the cathode interconnection structure 22 is electrically insulated from the n-type contact surfaces of the first sub-pixel 2, the second sub-pixel 3, and the third sub-pixel 4 through the passivation layer 17. These structures ensure the smooth return of the cathode current. At the same time, the electrical insulation design prevents short circuits between the cathode and other parts, ensuring the stable electrical performance of the device and enabling the microdisplay to work properly. The optional material combinations for the first cathode ohmic contact layer 14 are Ti / Al / Ti / Au, Cr / Au, etc.; the optional material combinations for the second cathode ohmic contact layer 15 and the third cathode ohmic contact layer 16 are Ti / Al, Ti / Al / Ni / Au, Ti / Al / Au, etc. These material combinations have good electrical conductivity and stability, can effectively reduce the cathode contact resistance, ensure the stable transmission of the cathode current, and thus ensure the stability and reliability of the sub-pixel light emission.

[0031] One end of the bonding wire 24 is connected to the sub-pixel common cathode pad 25, and the other end is connected to the driving substrate cathode 23 on the driving substrate 1, realizing the electrical connection between the sub-pixel cathode and the driving substrate cathode 23, and enabling the cathode current of the sub-pixel to flow back to the driving substrate 1. The bonding wire 24 completes the electrical connection of the entire circuit, ensures the integrity of the current loop, is a necessary condition for the normal light emission of the sub-pixel, and ensures the stable operation of the microdisplay. The first bonding layer 5 is used to bond the vertically stacked LED 31 to the driving substrate 1; the second bonding layer 6 is used to bond the blue-green light-emitting LED epitaxial wafer 34 and the red light-emitting LED epitaxial wafer 33 over the entire surface; the third bonding layer 7 is used to bond the green light-emitting LED epitaxial layer 27 and the blue light-emitting LED epitaxial layer 28 over the entire surface to the blue-green light-emitting LED substrate 29; the second bonding layer 6 and the third bonding layer 7 are formed by a full-surface bonding process to improve the mechanical connection stability between layers. The full-surface bonding process enhances the bonding force between each epitaxial wafer and the substrate, makes the entire microdisplay structure more stable, can withstand certain external forces and environmental changes, and improves the reliability and service life of the product; the first bonding layer 5 and the anode connection structure embedded therein are formed by alignment bonding to achieve the anode addressing connection between the vertically stacked LED and the driving substrate 1.

[0032] The above-described vertically stacked Micro-LED full-color microdisplay is fabricated through the following steps, including the following steps: Step 1: Prepare the epitaxial wafer: Provide a flip-chip structured red light-emitting LED epitaxial wafer 33, the structure of which is as Figure 6As shown, its p-type contact surface is on the top layer and its n-type contact surface is on the bottom layer. The red light LED epitaxial wafer 33 can be composed of a quaternary compound AlGaInP, and the corresponding substrate material is GaAs. At the same time, a blue-green light LED epitaxial wafer 34 grown on the same substrate is provided, and its structure is as Figure 7 shown, with its p-type contact surface on the top and its n-type contact surface on the bottom. The optional blue and green light LEDs can be composed of a ternary compound InGaN. The blue and green light LEDs are connected by materials such as silica gel or epoxy glue, and the substrate is made of materials such as Si or sapphire.

[0033] Step 2: Processing of the red light LED epitaxial wafer 33: Move the red light LED epitaxial wafer 33 to a temporary carrier, with its p-type contact surface on the bottom layer and its n-type contact surface on the top layer, and then peel off the red light LED substrate 30. Subsequently, thin the red light LED epitaxial layer 26 to the n-GaN layer, and then integrally bond the n-type contact surface of the red light LED epitaxial layer 26 and the p-type contact surface of the green light LED epitaxial layer 27. The bonding layer can be a dielectric layer, such as SiO 2 、Al 2 O 3 etc., or a polymer layer, such as silica gel, epoxy glue, benzocyclobutene (BCB), etc., and then peel off the temporary carrier.

[0034] Step 3: Etch the red light LED epitaxial layer 26 and the second bonding layer 6 to form a through hole connecting to the second sub-pixel anode 20; then etch the green light LED epitaxial layer 27 and the third bonding layer 7 to form a through hole connecting to the third sub-pixel anode 21. Subsequently, deposit a thin insulating layer. The material can be a dielectric layer, such as SiO 2 、Al 2 O 3 etc., or a polymer layer, such as silica gel, epoxy glue, benzocyclobutene (BCB), etc., to form the first bonding layer 5; then open the hole in the first bonding layer 5 within the through hole to facilitate the deposition of the second anode ohmic contact layer 9 and the third anode ohmic contact layer 10 on the p-type contact surfaces of the green light LED epitaxial layer 27 and the blue light LED epitaxial layer 28.

[0035] Step 5: Deposit the p-GaN ohmic contact layers for the blue and green light LEDs, namely the second anode ohmic contact layer 9 and the third anode ohmic contact layer 10, in the through holes. The material can be a low work function metal and its material combination, such as Ni / Au, pd / Au, pt / Au, etc., or a transparent conductive oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), etc.; then deposit a seed layer integrally.

[0036] Step 6: Electroplate and fill the vias to form the second anode connection structure 12 and the third anode connection structure 13, so as to electrically connect the anodes of the second sub-pixel 3 and the third sub-pixel 4 to the driving substrate 1; then remove the excess metal formed by electroplating through a planarization process, so that the second anode connection structure 12, the third anode connection structure 13 and the first bonding layer 5 are on the same horizontal plane.

[0037] Step 7: Deposit a first anode ohmic contact layer 8 on the p-type contact surface and the anode connection structure of the first sub-pixel 2. The optional material combinations of the first anode ohmic contact layer 8 are Ni / Au, Ti / Pt / Au, etc.

[0038] Step 8: Flip-chip bond the vertically stacked LED 31 and the driving substrate 1. Optional bonding methods include bump bonding, hybrid bonding, etc.; then peel off the blue-green LED substrate 29. Optional substrate peeling methods include laser peeling, chemical etching, mechanical grinding, etc. Subsequently, etch the blue LED epitaxial layer 28 and the green LED epitaxial layer 27 to form the light-emitting windows of the first sub-pixel 3 and the second sub-pixel 4; deposit a passivation layer 17 to protect the device surface from the external environment; then open holes in the passivation layer 17 to facilitate the contact between the n-GaN sides of the first sub-pixel 2, the second sub-pixel 3 and the third sub-pixel 4 and the first cathode ohmic contact layer 14, the second cathode ohmic contact layer 15 and the third cathode ohmic contact layer 16.

[0039] Step 9: Deposit the first cathode ohmic contact layer 14, the second cathode ohmic contact layer 15 and the third cathode ohmic contact layer 16. The optional metal combinations of the first cathode ohmic contact layer 14 are Ti / Al / Ti / Au, Cr / Au, etc.; the optional metal combinations of the second cathode ohmic contact layer 15 and the third cathode ohmic contact layer 16 are Ti / Al, Ti / Al / Ni / Au, Ti / Al / Au, etc.; deposit a cathode interconnection structure 22 to lead the first cathode ohmic contact layer 14, the second cathode ohmic contact layer 15 and the third cathode ohmic contact layer 16 to the sub-pixel common cathode pad 25; finally, perform wire bonding between the sub-pixel common cathode pad 25 and the driving substrate cathode 23 to complete the electrical connection of the entire device.

[0040] Therefore, by adopting the above-mentioned vertical stacked Micro-LED full-color microdisplay, the problems in the existing Micro-LED full-color display technology, such as the difficulty in balancing the high-precision transfer accuracy and yield, low color conversion efficiency, serious light decay, complex traditional vertical stacking process, easy damage to the bonding layer and performance degradation, are solved, realizing high-brightness wide-color gamut display, efficient production and large-scale mass production.

[0041] In this text, specific examples are used to illustrate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A vertically stacked Micro-LED full-color micro display, characterized in that: It includes a substrate unit, a pixel stacking unit and a connecting unit; a plurality of the pixel stacking units are vertically stacked on the substrate unit, and electrical and mechanical connections are achieved through the connecting unit; the pixel stacking unit includes a plurality of sub-pixel structures with different luminous colors, each sub-pixel structure has an anode contact portion and a cathode contact portion, the anode contact portion is connected to the anode of the substrate unit through the connecting unit, and the cathode contact portion is connected to the cathode of the substrate unit through the connecting unit.

2. A vertically stacked Micro-LED full-color micro display according to claim 1, characterized in that: The substrate unit is a driving substrate, on which a driving substrate anode metal, a first sub-pixel anode, a second sub-pixel anode, a third sub-pixel anode and a driving substrate cathode are arranged; The anode metal of the driving substrate is respectively connected to the first sub-pixel anode, the second sub-pixel anode and the third sub-pixel anode to provide anode driving signals for different sub-pixels, and the cathode of the driving substrate is used to receive cathode current of the sub-pixel.

3. A vertically stacked Micro-LED full-color micro display according to claim 2, characterized in that: The plurality of pixel stacking units are composed of vertically stacked RGB pixel arrays, and the vertically stacked RGB pixel arrays are driven in a common cathode and anode addressing manner; The vertically stacked RGB pixel array includes a plurality of vertically stacked RGB pixels, each of the vertically stacked RGB pixels includes a first sub-pixel, a second sub-pixel, and a third sub-pixel stacked in sequence in a vertical direction in a stepped shape; a quarter area and three quarter areas corresponding to the second sub-pixel and the third sub-pixel are removed to open light exit windows for the first sub-pixel and the second sub-pixel; The first sub-pixel is a sub-pixel emitting red light at the bottom layer, which includes a red LED epitaxial layer; the second sub-pixel is a sub-pixel emitting green light at the middle layer, which includes a green LED epitaxial layer; the third sub-pixel is a sub-pixel emitting blue light at the top layer, which includes a blue LED epitaxial layer; the green LED epitaxial layer and the blue LED epitaxial layer are fully bonded to the blue-green LED substrate through the third bonding layer to form a blue-green LED epitaxial wafer, the blue-green LED epitaxial wafer is fully bonded to the red LED epitaxial wafer through the second bonding layer, the red LED epitaxial wafer is composed of the red LED epitaxial layer and the red LED substrate, and the red LED substrate is peeled off to form a vertically stacked LED; the light output window area ratio of the first sub-pixel, the second sub-pixel and the third sub-pixel is 1:2:

1.

4. The vertically stacked Micro-LED full-color micro display according to claim 3, characterized in that: The connection unit includes an anode connection structure, a cathode connection structure, a bonding layer and a bonding wire; the anode connection structure includes a first anode connection structure, a second anode connection structure and a third anode connection structure; the cathode connection structure includes a first cathode ohmic contact layer, a second cathode ohmic contact layer, a third cathode ohmic contact layer, a cathode interconnection structure and a sub-pixel common cathode pad; the bonding layer includes a first bonding layer, a second bonding layer and a third bonding layer.

5. The vertically stacked Micro-LED full-color micro display according to claim 4, characterized in that: One end of the first anode connection structure is connected to the first anode ohmic contact layer of the p-type contact surface of the first sub-pixel, and the other end is connected to the first sub-pixel anode on the driving substrate, so as to realize the anode signal transmission and mechanical connection between the first sub-pixel and the driving substrate; one end of the second anode connection structure is connected to the second anode ohmic contact layer of the p-type contact surface of the second sub-pixel, and the other end is connected to the second sub-pixel anode on the driving substrate; one end of the third anode connection structure is connected to the third anode ohmic contact layer of the p-type contact surface of the third sub-pixel, and the other end is connected to the third sub-pixel anode on the driving substrate; the first anode connection structure, the second anode connection structure and the third anode connection structure are all formed by electroplating filling in the through hole.

6. The vertically stacked Micro-LED full-color micro display according to claim 5, characterized in that: The materials of the first anode ohmic contact layer, the second anode ohmic contact layer and the third anode ohmic contact layer are low work function metals and their material combinations or transparent conductive oxides, which form ohmic contacts with the p-type contact surfaces of the first sub-pixel, the second sub-pixel and the third sub-pixel respectively to reduce contact resistance.

7. The vertically stacked Micro-LED full-color micro display according to claim 4, characterized in that: The first cathode ohmic contact layer forms an ohmic contact with the n-type contact surface of the first sub-pixel, the second cathode ohmic contact layer forms an ohmic contact with the n-type contact surface of the second sub-pixel, and the third cathode ohmic contact layer forms an ohmic contact with the n-type contact surface of the third sub-pixel; the first cathode ohmic contact layer, the second cathode ohmic contact layer and the third cathode ohmic contact layer are connected together through a cathode interconnection structure and led to a sub-pixel common cathode pad; the cathode interconnection structure is electrically insulated from the n-type contact surfaces of the first sub-pixel, the second sub-pixel and the third sub-pixel through a passivation layer.

8. The vertically stacked Micro-LED full-color micro display according to claim 7, characterized in that: The material combination of the first cathode ohmic contact layer is one of Ti / Al / Ti / Au and Cr / Au, and the material combination of the second cathode ohmic contact layer and the third cathode ohmic contact layer is one of Ti / Al, Ti / Al / Ni / Au and Ti / Al / Au.

9. The vertically stacked Micro-LED full-color micro display according to claim 7, characterized in that: One end of the bonding wire is connected to the sub-pixel common cathode pad, and the other end is connected to the drive substrate cathode on the drive substrate, so as to realize the electrical connection between the sub-pixel cathode and the drive substrate cathode, and make the cathode current of the sub-pixel flow back to the drive substrate.

10. The vertically stacked Micro-LED full-color micro display according to claim 4, characterized in that: The first bonding layer is used to bond the vertically stacked LED to the driving substrate; the second bonding layer is used to bond the blue-green LED epitaxial wafer to the red LED epitaxial wafer on the entire surface; the third bonding layer is used to bond the green LED epitaxial layer and the blue LED epitaxial layer to the blue-green LED substrate on the entire surface; the second bonding layer and the third bonding layer are formed by a full-surface bonding process to improve the mechanical connection stability between the layers; the first bonding layer and the embedded anode connection structure are formed by alignment bonding to achieve an anode addressing connection between the vertically stacked LED and the driving substrate.

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