Full-color micro LED display manufacturing method using monolithic integration of micro LEDs with transistors and full-color micro LED display manufactured by the same

Abstract

The present invention relates to a method for manufacturing a full-color transparent micro LED display. The present invention provides a method for manufacturing a full-color transparent micro LED display through monolithic integration of micro LEDs and transistors, comprising: a step of manufacturing an integrated device by integrating micro LEDs and thin-film transistors on an RGB LED epitaxial wafer; a step of manufacturing RGB cell-unit displays by forming transparent wiring on the wafer on which the integrated device is formed, inspecting the display at the wafer stage, and then performing wafer thinning and dicing; and a step of manufacturing a full-color display by aligning the RGB die-unit displays and bonding the wafers using a transparent bonding material.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a full-color transparent micro LED display, and more specifically, to a method for manufacturing a full-color transparent display by monolithically integrating micro LEDs and thin-film transistors on an epitaxial wafer for LED fabrication, fabricating transparent displays in die units for each RGB (Red, Green, Blue), and then vertically aligning and bonding them. Background Technology

[0002] Micro LEDs are attracting attention as next-generation displays due to their superior characteristics compared to Organic Light-Emitting Diodes (OLEDs), such as brightness, contrast ratio, response speed, and lifespan. However, unlike OLEDs, which can be implemented through simple processes, Micro LEDs must be fabricated using Metal Organic Chemical Vapor Deposition (MOCVD) on crystalline substrates (e.g., Si, Al2O3). For this reason, the manufacturing of Micro LED displays is largely divided into the frontplane and the backplane.

[0003] The front plane consists of light-emitting elements, and the back plane consists of driving elements for driving LEDs and metal wiring for applying signals to the driving elements. Therefore, the manufacturing of a micro LED display is carried out in parallel to manufacture the front plane and the back plane, respectively, and then a transfer process is required to transfer the LED chip manufactured on the crystalline substrate to the back plane on which the driving elements and wiring are formed.

[0004] Transfer processes include pick and place, stamp, and electrostatic methods. However, because micro-LED chips fabricated on sapphire substrates are small and thin, problems such as chip damage, transfer failure, chip alignment failure, or chip tilting occur during the transfer process. Furthermore, micro-LEDs are very small, ranging from 1 to 100 μm, and approximately 25 million pixels are required to implement a 4K display device. Consequently, there is a problem in that it takes at least one month to manufacture a single 4K display device using a simple pick and place method.

[0005] Micro LEDs suffer from low luminous efficiency due to their extremely small size; to overcome this, methods such as using passivation layers like SiO2 and SiN to improve luminous efficiency are employed. Additionally, the low driving current necessitates precise driving technology, which tends to lead to complex pixel circuits.

[0006] Manufacturing methods for full-color micro LEDs include using quantum dots as a color conversion layer and techniques for growing and transferring RGB on separate wafers. Among these, using quantum dots as a color conversion layer has cost and efficiency issues, while the method of transferring RGB separately has the problem of low pixel density (PPI) and a threefold increase in the number of transfer processes. Prior art literature

[0007] Korean Registered Patent Publication No. 10-2669057 The problem to be solved

[0008] The present invention aims to solve the problem of the transfer process of the micro LED display as described above. Specifically, the invention aims to manufacture a full-color transparent display by manufacturing transparent die-unit displays on separate RGB epitaxy wafers, and then aligning and bonding the separate RGB die-unit displays. means of solving the problem

[0009] The present invention provides a method for manufacturing a full-color transparent micro LED display through monolithic integration of a micro LED and a transistor, comprising: a step of manufacturing an integrated device by integrating a micro LED and a thin-film transistor on an RGB LED epitaxial wafer; a step of manufacturing a cell-unit display by RGB by forming transparent wiring on the wafer on which the integrated device is formed, inspecting the display at the wafer level, and then performing wafer thinning and dicing to manufacture a die-unit display by RGB; and a step of manufacturing a full-color display by aligning the die-unit displays by RGB and bonding the wafers using a transparent bonding material.

[0010] The above display inspection is an inspection of the optical and electrical characteristics of the display defined at the wafer level.

[0011] The above integrated device fabrication steps are performed sequentially as follows: preparing an LED epitaxy wafer; forming a MESA structure to expose the n-GaN of the LED on the LED epitaxy wafer; depositing an LED electrode on the wafer having the MESA structure formed thereon; forming an insulating layer for electrical isolation on the wafer having the LED electrode formed thereon; depositing a gate electrode of a transistor on the wafer having the insulating layer formed thereon; forming a dielectric layer for insulation on the wafer having the gate electrode formed thereon; forming an active layer of a transistor on the wafer having the dielectric layer formed thereon; selectively etching the insulating layer of the wafer having the active layer formed thereon to form an opening to connect the source electrode of the transistor and the anode of the LED; and depositing a transistor electrode on the wafer having the opening formed thereon.

[0012] The above wafer polishing is performed so that the final thickness of the substrate is in the range of 20 μm to 500 μm.

[0013] The above transparent wiring and electrodes include one or more of oxide semiconductors, polymer materials, 2D materials, metal-based nanostructures, and carbon-based nanostructures.

[0014] The above oxide semiconductor includes one or more of ITO, ZnO, IGZO, AZO, IZTO, SnO, FTO, and CuO.

[0015] The above transparent bonding material includes a transparent adhesive or a patterned opaque bonding material, and comprises oxide semiconductor series indium tin oxide (ITO), zinc oxide (ZnO), indium gallium zinc oxide (IGZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium zinc tin oxide (IZTO), fluorine-doped tin oxide (FTO), tin oxide (SnO₂), cadmium oxide (CdO), indium oxide (In₂O₃), titanium dioxide (TiO₂), and vanadium dioxide (VO₂). Dioxide), Nickel Oxide (NiO), Antimony-doped Tin Oxide (Sb-doped SnO₂), Copper Aluminum Oxide (CuAlO₂), Lanthanum-doped Zinc Oxide (La-doped ZnO), Silicon Dioxide (SiO₂), Silicon Nitride (SiN), Aluminum Oxide (Al₂O₃), Zirconium Dioxide (ZrO₂), Hafnium Oxide (HfO₂);Polymer-based transparent materials including polyethylenedioxythiophene polystyrene sulfonate (PEDOT), polypyrrole (PPy), polyaniline (PANI), polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polyimide (PI), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), Norland optical adhesive (NOA), SU-8, and epoxy resin; It comprises one or more of the two-dimensional materials graphene, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS₂), tungsten disulfide (WS₂), black phosphorus (BP), tin disulfide (SnS₂), MXene (Ti₃C₂), and molybdenum ditelluride (MoTe₂);

[0016] The above-mentioned patterned opaque bonding material comprises indium (In), tin (Sn), gold (Au), nickel (Ni), metal-based nanostructures such as silver nanowires (AgNW), aluminum nanowires (AlNW), gold nanowires (AuNW), nickel nanowires (NiNW), copper nanowires (CuNW), platinum nanowires (PtNW), palladium nanoparticles, ruthenium nanoparticles, and titanium nanotubes; carbon-based nanostructures such as carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and fullerene (C 60), graphene nanoribbons, carbon nanofibers, carbon quantum dots, graphene oxide (GO), reduced graphene oxide (rGO); nanopatterns and metamaterials, such as metamaterials, nanohole arrays, nanopyramids, nanorods, nanowires, nanoparticles, plasmonic structures, nanofibers, nanoporous structures; It includes one or more of the following composite materials: silver nanowire / polyethylenedioxythiophene composite (AgNW / PEDOT), carbon nanotube / polymer composite (CNT / Polymer), graphene / polymer composite, molybdenum disulfide / silver nanowire hybrid film (MoS₂ / AgNW), zinc oxide / graphene composite (ZnO / Graphene), silicon dioxide / carbon nanotube composite (SiO₂ / CNT), titanium dioxide / polyaniline composite (TiO₂ / PANI), copper nanowire / polyvinylidene fluoride composite (CuNW / PVDF), MXene / polymer composite (MXene / Polymer), and silver nanoparticle / polyethylenedioxythiophene composite (Ag Nanoparticle / PEDOT).

[0017] When using the above-mentioned patterned opaque bonding material, transparency is ensured by forming a thin film by one or more methods such as thermal evaporation, electron beam deposition, sputtering deposition, and electroplating, and then etching to form a pattern, or by forming the opaque bonding material using an inkjet printing method.

[0018] Pixel density is improved by vertically aligning the pixels of the above RGB die-unit displays and placing them in the same position.

[0019] The present invention also provides a full-color transparent micro LED display manufactured by the above manufacturing method.

[0020] RGB subpixels are controlled individually through a Display Driver IC (DDI) attached to each pixel.

[0021] Through these means of solution, the present invention can realize a monolithic integrated structure that does not require a transfer process and provide a full-color micro LED display having high transparency and pixel density. Effects of the invention

[0022] The method for manufacturing a full-color transparent micro LED display through monolithic integration of micro LEDs and transistors according to the present invention can improve the luminous efficiency of the LED through a passivation layer of the monolithic integrated device, and can manufacture a transparent display on each epitaxy wafer without transfer by developing a die-unit RGB transparent display through a transparent wiring process.

[0023] In addition, thin-film transistors can be integrated to minimize the pixel circuit area of ​​the display, and pixel density can be maximized by vertically stacking RGB die-unit displays.

[0024] In addition, the display manufacturing process, which was previously carried out in parallel, can be standardized, and a full-color display can be easily implemented by bonding transparent displays made in die units for each RGB.

[0025] This enables the manufacturing of next-generation transparent micro LED displays with high efficiency, high resolution, and high transmittance. Brief explanation of the drawing

[0026] FIG. 1 is a diagram illustrating the LED wafer preparation, MESA structure formation, LED electrode deposition, passivation layer formation, and gate deposition steps among the integrated device fabrication steps of the present invention. FIG. 2 is a diagram illustrating the steps of forming a dielectric layer, forming an active layer, etching a passivation layer, and depositing a transistor electrode among the steps of fabricating an integrated device of the present invention. FIG. 3 is a diagram illustrating the manufacturing steps of a cell-unit display for each RGB of the present invention, showing a transparent wiring process, electrical / optical inspection, wafer polishing, and cutting process. FIG. 4 is a drawing illustrating the vertical stacking structure of an RGB die unit display for manufacturing a full-color display according to the present invention. FIGS. 5 and 6 illustrate a method for manufacturing a die-unit display using an opaque bonding material of the present invention, showing a stacked structure, a dot array pattern for ensuring transparency, and a pattern formation method. FIG. 7 is a diagram illustrating the structure of a final full-color transparent micro LED display according to the present invention. Specific details for implementing the invention

[0027] The advantages and features of the invention disclosed herein, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, this specification is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of this specification is complete and to fully inform those skilled in the art (hereinafter referred to as "skilled in the art") of the scope of this specification, and the scope of rights of this specification is defined only by the scope of the claims.

[0028] The terms used in this specification are for describing the embodiments and are not intended to limit the scope of the claims in this specification. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. The terms "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of one or more other components in addition to the components mentioned. Throughout the specification, the same reference numerals refer to the same components, and "and / or" includes each of the mentioned components and all combinations of one or more. Although terms such as "first," "second," etc., are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical scope of the present invention.

[0029] Unless otherwise defined, all terms used herein (including technical and scientific terms) may be used in a meaning commonly understood by a person skilled in the art to which this specification pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0030] Spatially relative terms such as "below," "beneath," "lower," "above," and "upper" may be used to facilitate the description of the relationship between one component and other components as illustrated in the drawings. Spatially relative terms should be understood as encompassing different orientations of components during use or operation, in addition to the orientations depicted in the drawings. For example, if a component depicted in a drawing is inverted, a component described as "below" or "beneath" of another component may be placed "above" of that component. Therefore, the exemplary term "below" may encompass both the lower and upper directions. Components may also be oriented in other directions, and accordingly, spatially relative terms may be interpreted according to the orientation.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0032] The method for manufacturing a full-color transparent micro LED display according to the present invention is broadly divided into an integrated element fabrication step, a cell-unit display fabrication step for each RGB, and a full-color display fabrication step.

[0033] As shown in FIGS. 1 and 2, the integrated device fabrication steps proceed sequentially as a process of integrating micro LEDs and thin-film transistors on an LED epitaxy wafer. First, an LED epitaxy wafer (LED substrate) is prepared, and then a MESA structure is formed to expose the n-GaN of the LED. Subsequently, LED electrodes are deposited, and an insulating layer for electrical isolation is formed. Next, the gate electrode of the transistor is deposited, a dielectric layer for insulation is formed, and then the active layer of the transistor is formed. The insulating layer is selectively etched to form an opening for connecting the source electrode of the transistor and the anode of the LED, and finally, the transistor electrodes are deposited. As shown in FIG. 2, the fabricated integrated device consists of a light-emitting device section and a driving device section, and includes a substrate, n-GaN, MQW, p-GaN, various electrode layers, and an insulating layer.

[0034] The manufacturing steps for RGB cell-unit displays are carried out as shown in Fig. 3. First, transparent wiring is formed on a wafer on which integrated elements are arranged. The transparent wiring can be made of materials available for use in transparent bonding materials. After forming the wiring, electrical and optical characteristics are inspected on the wafer at the cell level. Subsequently, the thickness of the substrate is adjusted to a range of 20-500 μm through wafer polishing and polishing processes, and the wafer is cut into die units. Fig. 3 shows an example of a Blue LED, and Green LEDs and Red LEDs can be manufactured in the same way.

[0035] As shown in FIGS. 4 and 5, the full-color display fabrication step involves vertically aligning and bonding RGB die-unit displays. As illustrated in FIGS. 4 and 5, bonding methods include using a transparent adhesive or using a patterned opaque bonding material. When using an opaque material, transparency is ensured by forming a thin film and etching it to form a pattern using one or more methods such as thermal evaporation, electron beam deposition, sputtering deposition, or electroplating, or by forming the opaque bonding material using an inkjet printing method. The final display illustrated in FIG. 7 can individually control RGB subpixels through a Display Driver IC.

[0036] All materials of the full-color micro LED display of the present invention may use exemplary materials available in transparent bonding materials.

[0037] The manufacturing method of the present invention eliminates the need for a transfer process and can achieve high pixel density through the vertical stacking of RGB pixels, and can produce a full-color micro LED display with excellent transmittance by utilizing transparent materials.

Claims

Claim 1 A method for manufacturing a full-color transparent micro LED display through monolithic integration of a micro LED and a transistor, comprising: a step of manufacturing an integrated device by integrating a micro LED and a thin-film transistor on an RGB LED epitaxial wafer; a step of manufacturing RGB-specific cell-specific displays by forming transparent wiring on the wafer on which the integrated device is formed, inspecting the physical properties of the display at the wafer level, and then performing wafer thinning and dicing; and a step of manufacturing a full-color display by aligning the RGB-specific die-specific displays and bonding the wafers using a transparent bonding material. Claim 2 A method for manufacturing a full-color transparent micro LED display according to claim 1, wherein the integrated device fabrication step comprises sequentially performing the following steps: preparing an LED epitaxy wafer; forming a MESA structure to expose the n-GaN of an LED on the LED epitaxy wafer; depositing an LED electrode on the wafer having the MESA structure formed thereon; forming an insulating layer for electrical isolation on the wafer having the LED electrode formed thereon; depositing a gate electrode of a transistor on the wafer having the insulating layer formed thereon; forming a dielectric layer for insulation on the wafer having the gate electrode formed thereon; forming an active layer of a transistor on the wafer having the dielectric layer formed thereon; selectively etching the insulating layer of the wafer having the active layer formed thereon to form an opening to connect the source electrode of the transistor and the anode of the LED; and depositing a transistor electrode on the wafer having the opening formed thereon. Claim 3 A method for manufacturing a full-color transparent micro LED display according to claim 1, characterized in that the wafer polishing is performed such that the final thickness of the substrate is within the range of 20 μm to 500 μm. Claim 4 A method for manufacturing a full-color transparent micro LED display according to claim 1, wherein the transparent wiring and electrode comprise one or more of an oxide semiconductor, a polymer material, a 2D material, a metal-based nanostructure, and a carbon-based nanostructure. Claim 5 A method for manufacturing a full-color transparent micro LED display according to claim 4, wherein the oxide semiconductor comprises one or more of ITO, ZnO, IGZO, AZO, IZTO, SnO, FTO, and CuO. Claim 6 In claim 1, the transparent bonding material comprises a transparent adhesive or a patterned opaque bonding material, and includes indium tin oxide (ITO), zinc oxide (ZnO), indium gallium zinc oxide (IGZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium zinc tin oxide (IZTO), fluorine-doped tin oxide (FTO), tin oxide (SnO₂), cadmium oxide (CdO), indium oxide (In₂O₃), and titanium dioxide (TiO₂). Vanadium dioxide (VO₂), nickel oxide (NiO), antimony-doped tin oxide (Sb-doped SnO₂), copper aluminum oxide (CuAlO₂), lanthanum-doped zinc oxide (La-doped ZnO), silicon dioxide (SiO₂), silicon nitride (SiN), aluminum oxide (Al₂O₃), zirconium dioxide (ZrO₂), hafnium dioxide (HfO₂);Polymer-based transparent materials including polyethylenedioxythiophene polystyrene sulfonate (PEDOT), polypyrrole (PPy), polyaniline (PANI), polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polyimide (PI), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), Norland optical adhesive (NOA), SU-8, and epoxy resin; The patterned opaque bonding material comprises one or more of the two-dimensional materials graphene, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS₂), tungsten disulfide (WS₂), black phosphorus (BP), tin disulfide (SnS₂), MXene (Ti₃C₂), and molybdenum ditelluride (MoTe₂), and comprises indium (In), tin (Sn), gold (Au), nickel (Ni), and metal-based nanostructures such as silver nanowires (AgNW), aluminum nanowires (AlNW), gold nanowires (AuNW), nickel nanowires (NiNW), copper nanowires (CuNW), platinum nanowires (PtNW), palladium nanoparticles, ruthenium nanoparticles, and titanium nanotubes; Carbon-based nanostructures such as carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and fullerenes (C; 60 ), graphene nanoribbons, carbon nanofibers, carbon quantum dots, graphene oxide (GO), reduced graphene oxide (rGO); nanopatterns and metamaterials, such as metamaterials, nanohole arrays, nanopyramids, nanorods, nanowires, nanoparticles, plasmonic structures, nanofibers, nanoporous structures; A method for manufacturing a full-color transparent micro light-emitting diode display characterized by comprising one or more of the following composite materials: silver nanowire / polyethylenedioxythiophene composite (AgNW / PEDOT), carbon nanotube / polymer composite (CNT / Polymer), graphene / polymer composite, molybdenum disulfide / silver nanowire hybrid film (MoS₂ / AgNW), zinc oxide / graphene composite (ZnO / Graphene), silicon dioxide / carbon nanotube composite (SiO₂ / CNT), titanium dioxide / polyaniline composite (TiO₂ / PANI), copper nanowire / polyvinylidene fluoride composite (CuNW / PVDF), MXene / polymer composite (MXene / Polymer), and silver nanoparticle / polyethylenedioxythiophene composite (Ag Nanoparticle / PEDOT). Claim 7 A method for manufacturing a full-color transparent micro LED display according to claim 6, characterized in that when using the patterned opaque bonding material, transparency is secured by forming a thin film by one or more methods of thermal evaporation, electron beam deposition, sputtering deposition, and electron plating, and then etching to form a pattern, or by forming the opaque bonding material using an inkjet printing method. Claim 8 A method for manufacturing a full-color transparent micro LED display according to claim 1, characterized by improving pixel density by vertically aligning the pixels of the RGB die unit display and placing them at the same position. Claim 9 Full-color transparent micro LED display manufactured by the manufacturing method of claim 1. Claim 10 A full-color transparent micro LED display characterized by individually controlling RGB subpixels through a Display Driver IC (DDI) attached to each pixel in claim 9.

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