Ultrathin LED element, inkjet ink containing the same, and light source

Abstract

The present invention relates to an LED element, and more particularly to an ultra-thin LED element, an inkjet ink containing the same, and a light source.

Description

Technical Field

[0001] This invention relates to LED elements, and more specifically, to ultra-thin LED elements, inkjet inks incorporating the same, and light sources. Background Technology

[0002] Micro-LEDs and nano-LEDs offer excellent color and high efficiency, and are environmentally friendly materials, thus they are being used as core materials for displays. Based on this market situation, research is currently underway to develop new nanorod LED structures or nanowire LEDs with shell coatings through new manufacturing processes. Furthermore, research is also being conducted on protective film materials to achieve high efficiency and stability of the protective film covering the outer surface of nanorods, or on ligand materials that facilitate subsequent processes.

[0003] In conjunction with research in this material field, large-scale red, green, and blue micro-LED display TVs have recently been commercialized. In the future, full-color TVs will be commercialized using blue sub-pixels and red and green sub-pixels. The blue sub-pixels are implemented using blue micro-LEDs or nano-LEDs, while the red and green sub-pixels are implemented using quantum dots emitted by the blue LEDs. Furthermore, red, green, and blue nano-LED display TVs are also planned for commercialization.

[0004] Micro-LED displays boast advantages such as high performance, theoretically long lifespan, and extremely high efficiency. However, developing an 8K resolution display requires individually matching red, green, and blue micro-LEDs to nearly 100 million sub-pixels. Therefore, considering the high cost, high process defect rate, and low productivity of the pick-and-place technology for manufacturing micro-LED displays, there are technological limitations, making it difficult to manufacture truly high-resolution commercial displays, from smartphones to televisions. Furthermore, the reality is that configuring nano-LEDs one by one onto sub-pixels using the same pick-and-place technology as micro-LEDs is even more challenging.

[0005] To overcome this difficulty, Patent Publication No. 10-1436123 discloses a display manufactured by means of: immersing a solution of mixed nanorod LEDs into a sub-pixel, then forming an electric field between two arranged electrodes, magnetically aligning the nanorod LED elements on the electrodes, thereby forming the sub-pixel.

[0006] However, the disclosed technology arranges LED elements using an electric field, requiring the LED elements to have a large, unidirectionally elongated rod shape. This makes the LED elements prone to rapid deposition in solvents, thus hindering their ink-making process. Furthermore, the elements are assembled lying flat on the electrodes, parallel to the stacking direction of the semiconductor layers within the element, resulting in a small light extraction area and poor efficiency.

[0007] Specifically, known manufacturing methods for nanorod-shaped LED devices include hybrid nanopatterning processes and dry / wet etching for top-down LED chip fabrication, or direct bottom-up growth on a substrate. In this type of nanorod LED, the long axis of the LED aligns with the stacking direction, i.e., in the p-GaN / InGaN multiple quantum well (MQW) / n-GaN stacked structure, resulting in a small light-emitting area. Due to this small area, surface defects significantly reduce efficiency, and the difficulty in optimizing electron-hole recombination rates leads to a substantial decrease in luminous efficiency compared to traditional chips.

[0008] Therefore, there is an urgent need to develop a new type of LED material that is suitable for ink fabrication, has a large light-emitting area, minimizes or prevents efficiency reduction caused by surface defects, and optimizes the electron-hole recombination rate. Summary of the Invention

[0009] (The problem to be solved)

[0010] The present invention is proposed to solve the above-mentioned problems, and aims to provide an ultra-thin LED element, an inkjet ink and a light source containing the same, which are suitable for ink-making, have a large light-emitting area, minimize or prevent efficiency reduction caused by surface defects, and optimize the electron-hole recombination speed.

[0011] (Solutions)

[0012] To address the aforementioned issues, the present invention provides an ultra-thin LED element, which includes at least a first conductive semiconductor layer, a photoactive layer, and a second conductive semiconductor layer, wherein the ratio between the thickness of the layers in the stacking direction and the length of the major axis in the cross-section perpendicular to the stacking direction is 1:0.5 to 1.5.

[0013] According to one embodiment of the present invention, either the first conductive semiconductor layer or the second conductive semiconductor layer may be an n-type group III nitride semiconductor layer, while the other may be a p-type group III nitride semiconductor layer.

[0014] In addition, the maximum area of ​​ultra-thin LED components can be 16μm. 2 the following;

[0015] In addition, the thickness of the ultra-thin LED element can be less than 2.7 μm, more preferably less than 2.0 μm, and even more preferably 0.2 to 1.0 μm.

[0016] More preferably, it can be below 4 μm², and even more preferably, it can be from 0.1 μm² to 2.5 μm².

[0017] In addition, the first conductive semiconductor layer is an n-type group III nitride semiconductor layer, and an electron delay layer may be included below the first conductive semiconductor layer to balance the number of electrons and holes recombinating in the photoactive layer.

[0018] Additionally, the electronic delay layer may comprise one or more selected from the group consisting of CdS, GaS, ZnS, CdSe, CaSe, ZnSe, CdTe, GaTe, SiC, ZnO, ZnMgO, SnO2, TiO2, In2O3, Ga2O3, Si, poly(paraphenylenevinylene) and its derivatives, polyaniline, poly(3-alkylthiophene) and poly(paraphenylene)

[0019] In addition, the first conductive semiconductor layer is a doped n-type group III nitride semiconductor layer, and the electron delay layer can be a group III nitride semiconductor with a doping concentration lower than that of the first conductive semiconductor layer.

[0020] Additionally, the ultra-thin LED element may also include a protective film that surrounds the exposed sides of the ultra-thin LED element.

[0021] In addition, the first conductive semiconductor layer is an n-type group III nitride semiconductor layer, and the second conductive semiconductor layer is a p-type group III nitride semiconductor layer; the ultra-thin LED element may further include at least one of a hole-pushing film and an electron-pushing film, wherein the hole-pushing film surrounds the exposed side of the second conductive semiconductor layer or the exposed side of the second conductive semiconductor layer and at least a portion of the exposed side of the photoactive layer to move the holes on the exposed side surface towards the center; and the electron-pushing film surrounds the exposed side of the first conductive semiconductor layer to move the electrons on the exposed side surface towards the center.

[0022] In addition, the ultra-thin LED element may include the hole pusher film and the electron pusher film. The electron pusher film may be set as the outermost film, and the outermost film surrounds the sides of the first conductive semiconductor layer, the photoactive layer and the second conductive semiconductor layer.

[0023] Additionally, the hole-push membrane may contain components derived from AlN. X Choose one or more from the group consisting of ZrO2, MoO, Sc2O3, La2O3, MgO, Y2O3, Al2O3, Ga2O3, TiO2, ZnS, Ta2O5 and n-MoS2.

[0024] In addition, the electron-push film may contain components derived from Al2O3, HfO2, and SiN. x SiO2, ZrO2, Sc2O3, AlN x Choose one or more from the group consisting of Ga2O3.

[0025] In addition, the ultra-thin LED element may also include: a second electrode layer disposed on the first conductive semiconductor layer; and a first electrode layer disposed on the second conductive semiconductor layer.

[0026] In addition, a selective bonding layer is also included on the top or bottom layer of the ultra-thin LED element. The selective bonding layer is used to assemble the ultra-thin LED element by erecting it in the thickness direction at the target position of the driving electrode. The selective bonding layer can be a magnetic layer or a chemical bond induction layer.

[0027] In addition, the present invention provides an inkjet ink composition comprising a plurality of ultra-thin LED elements of the present invention.

[0028] In addition, the present invention provides a light source in which the ultra-thin LED element of the present invention is mounted.

[0029] The following defines the terms used in this invention.

[0030] In the embodiments of the present invention, the terms “on,” “under,” and “lower” used to describe the formation of layers, regions, patterns, or substrates, layers, regions, or patterns, encompass both the meanings of “direct” and “indirect.”

[0031] (The effect of the invention)

[0032] Compared to conventional rod-shaped LED elements, the ultra-thin LED element of this invention increases the light-emitting area, thus facilitating the achievement of high brightness and luminous efficiency. Furthermore, while increasing the light-emitting area, it also significantly reduces the area of ​​the photoactive layer exposed on the surface, thereby preventing or minimizing efficiency degradation caused by surface defects. Further, it minimizes the reduction in electron-hole recombination efficiency caused by electron-hole velocity imbalance, and the resulting reduction in luminous efficiency. Moreover, it exhibits excellent dispersion and retention properties in solvents without the need for separate dispersants or other additives, making it suitable for use as inkjet ink and thus applicable to a wide range of light sources for displays and other applications.

[0033] This invention was developed with the support of the following national research and development programs, the details of which are as follows.

[0034] [Project Number] 1711105790

[0035] [Project Number] 2016R1A5A1012966

[0036] [Department Name] Ministry of Science, Technology and Information

[0037] [Name of Project Management (Specialty) Institution] Korea National Research Foundation

[0038] [Research Project Name] Engineering Field (S / ERC)

[0039] [Research Project Title] Circadian Rhythms Using Hybrid Devices: An ICT Research Center

[0040] [Name of the Institution Implementing the Project] Kookmin University Industry-Academia Collaboration Group

[0041] [Research Period] 2021-01-01~2021-12-31

[0042] [Project Number] 1415174040

[0043] [Project Number] 20016290

[0044] [Department Name] Trade, Industry and Resources Department

[0045] [Name of the Project Management (Specialty) Organization] Korea Institute for Industrial Technology Evaluation and Management

[0046] [Research Project Name] Electronic Components Industry Technology Development - Ultra-Large Micro-LED Modular Display

[0047] [Research Topic Title] Development of Submicron Blue Light Source Technology for Modular Displays

[0048] [Name of the Institution Implementing the Project] Kookmin University Industry-Academia Collaboration Foundation

[0049] [Research Period] April 1, 2021 – December 31, 2024 Attached Figure Description

[0050] Figure 1 This is a perspective view of an ultra-thin LED element according to an embodiment of the present invention.

[0051] Figure 2 It is along Figure 1 A cross-sectional view of the X-X' boundary line.

[0052] Figures 3a to 3c This is a diagram of various embodiments of the selective bonding layer that an ultra-thin LED element may have, according to an embodiment of the present invention.

[0053] Figure 4 It is a schematic diagram used to illustrate the balance of electrons and holes in an LED element.

[0054] Figure 5 This is a perspective view of an ultra-thin LED element according to an embodiment of the present invention.

[0055] Figure 6 This is a cross-sectional view of an ultra-thin LED element according to an embodiment of the present invention.

[0056] Figure 7 This is a schematic diagram of a method for manufacturing an ultra-thin LED element according to an embodiment of the present invention.

[0057] Figure 8 This is a schematic diagram of the manufacturing process of the resin layer included in one embodiment of the present invention.

[0058] Figure 9 This is a schematic diagram of a method for manufacturing an ultra-thin LED element according to an embodiment of the present invention.

[0059] Figure 10 This is a schematic diagram of a method 2 for manufacturing an ultra-thin LED element according to an embodiment of the present invention.

[0060] Figure 11 This is a schematic diagram of a method for manufacturing an ultra-thin LED element according to an embodiment of the present invention.

[0061] Figures 12 to 13 These are SEM images taken at a specific step in a method for manufacturing an ultra-thin LED element according to an embodiment of the present invention.

[0062] Figure 14 This is an SEM image of an ultra-thin LED element obtained by an ultra-thin LED element manufacturing method according to an embodiment of the present invention.

[0063] Figure 15This is an SEM image of the LED wafer remaining after an ultra-thin LED element has been manufactured using an ultra-thin LED element manufacturing method according to an embodiment of the present invention.

[0064] Figure 16 and Figure 17 It is an absorbance curve of each wavelength measured at different time intervals after the LED element assemblies of Example 1 and Comparative Example 1 were dispersed in acetone.

[0065] Figure 18 It is a dispersion retention (DR) curve calculated using absorbance measured at different time intervals after dispersing the LED element assemblies of Example 1 and Comparative Example 1 in acetone. Detailed Implementation

[0066] The following describes embodiments of the present invention to enable those skilled in the art to readily implement it. The present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0067] Reference Figure 1 and Figure 2 As described above, the ultra-thin LED element 101 of the present invention includes: a first conductive semiconductor layer 10, a photoactive layer 20, and a second conductive semiconductor layer 30. In addition, it may also include: a second electrode layer 60 formed under the first conductive semiconductor layer 10, a first electrode layer 40 formed on the second conductive semiconductor layer 30, and a selective bonding layer formed on the first electrode layer 40.

[0068] The aforementioned layers are stacked in any direction, and the ratio between the thickness in the stacking direction and the length of the major axis in the cross-section perpendicular to the stacking direction satisfies 1:0.5 to 1.5, preferably 1:0.8 to 1.2, and more preferably 1:0.9 to 1.1. Accordingly, when ultra-thin LED elements are implemented as inkjet ink, excellent dispersibility is achieved within the dispersion medium, which helps maintain a dispersed state for a long time without sedimentation. Furthermore, because the geometry suitable for this ink-like structure eliminates the need for separate additives to maintain the dispersed state, it has the advantage of preventing contamination of the driving electrode or circuit board due to separate additives. Moreover, when printing ink containing ultra-thin LED elements onto the driving electrode, conventional nanorod-type LED elements with large aspect ratios mostly lie almost flat on the driving electrode, while ultra-thin LED elements have the advantage of reducing the probability of lying flat on the driving electrode. Furthermore, reducing the probability of multiple components being assembled in different orientations when mounted on the driving electrode in the thickness direction reduces the likelihood of the p-type and n-type conductive semiconductor layers being assembled in different orientations. This reduces leakage current caused by reverse alignment, thus improving lifespan. Here, the length of the major axis refers to the diameter in the case of a circular cross-section, the length of the major axis in the case of an ellipse, and the length of the longest side in the case of a polygon.

[0069] Furthermore, the ratio between the length of the minor axis and the length of the major axis in the cross-section is 1:0.5 to 1.5, preferably 1:0.8 to 1.2, and more preferably 1:0.9 to 1.1, which is more conducive to achieving the above-mentioned objective of the present invention. Even if the ratio between the thickness and the length of the major axis satisfies 1:0.5 to 1.5, if the ratio between the length of the minor axis and the length of the major axis in the cross-section exceeds 1:0.5 to 1.5, the LED element will be difficult to maintain a dispersed state in the dispersion medium for a long time, and therefore may not be suitable for ink-forming. In addition, in order to maintain the dispersion of such an LED element with a geometry unsuitable for ink-forming in the dispersion medium for a long time, additives are required, thus posing a risk of contamination of the driving electrode or circuit board due to the use of additives.

[0070] On the other hand, for in Figure 1 The ultra-thin LED element 101 shown has a cross-section of the same size as the stacking direction of the layers, but is not limited to this, and the size of the cross-section may vary depending on the thickness.

[0071] Additionally, it should be noted that the shape of the ultra-thin LED element 101 can be in... Figure 1 The cylindrical shape shown is not limited to this; it is not only a polyhedron such as a hexahedron, octahedron, or decahedron, but also an irregular shape with star-shaped faces.

[0072] According to one embodiment of the present invention, the slow sedimentation rate during ink formation results in excellent dispersion retention performance, thus allowing the maximum surface area of ​​the ultra-thin LED element 101 to be 16 μm. 2 The following is preferred: 9μm 2 The following is more preferably 4μm. 2 Further, and more preferably, it can be 0.1 μm. 2 ~2.5μm 2 Here, maximum area refers to the maximum value among the areas of the vertically projected LED elements. If the maximum area exceeds 16μm... 2 At this time, the sedimentation rate increases, which may reduce the dispersion retention performance. Therefore, it is not suitable for manufacturing ink, or there may be limitations such as the need for additional additives or the use of specific dispersion media in order to make it into an ink.

[0073] According to one embodiment of the present invention, the thickness of the ultra-thin LED element 101 can be less than 2.7 μm, more preferably less than 2.0 μm, and even more preferably 0.2 to 1.0 μm.

[0074] More preferably, it can be below 1μm, which is more suitable for maintaining a dispersed state for a long time during ink production.

[0075] However, in the case of LED components, when achieving thinness, the location where electrons and holes bind is removed from the photoactive layer 20, which can reduce luminous efficiency. Especially when etching large-area LED wafers to achieve ultra-thin LED components, the thicknesses of the first conductive semiconductor layer, photoactive layer, and second conductive semiconductor layer are already determined in the LED wafer state, and differ from the wafer thickness. Since only a portion is etched to achieve an ultra-thin LED component, this problem inevitably arises. This change in the location where electrons and holes bind stems from the difference in the velocities of electrons and holes moving through the conductive semiconductor layer; for example, in the conductive semiconductor layer of n-type GaN, the electron mobility is 200 cm⁻¹. 2 / Vs, in contrast, the hole mobility in the conductive semiconductor layer of p-type GaN is only 5cm². 2 / Vs, because of such an imbalance in electron-hole velocities, the binding positions of electrons and holes along the thickness of the conductive semiconductor layer of p-type GaN and the conductive semiconductor layer of n-type GaN can vary beyond the photoactive layer.

[0076] For reference Figure 4To explain, in an LED element 200 with a stacked diameter of approximately 600 nm consisting of an n-type GaN conductive semiconductor layer 210, a photoactive layer 220, and a p-type GaN conductive semiconductor layer 230, in order to balance the number of electrons and holes recombinating at point A2 within the photoactive layer 220 by considering the electron mobility of the n-type GaN conductive semiconductor layer 210 and the hole mobility of the p-type GaN conductive semiconductor layer 230, the thickness h of the n-type GaN conductive semiconductor layer 210 must be thick during the design. Therefore, unless the thickness of the p-type GaN conductive semiconductor layer 230 is made very thin, the possibility of realizing a rod-shaped LED element with a length extending in the thickness direction is very high. In other words, when designing the thickness of each layer of an LED element so that the balance between the number of recombinated electrons and holes is located in the photoactive layer 220, even if the major axis length of the cross-section perpendicular to the thickness direction can be made smaller, it is difficult to reduce the thickness of the LED element to below a predetermined value. Ultimately, a rod-shaped LED element formed by extending the thickness direction of the LED element must be realized. Therefore, even if the balance between the number of recombinated holes and electrons in the photoactive layer is achieved, it is not suitable for realization as an ink. In addition, when a thin n-type GaN conductive semiconductor layer 210 is realized to be suitable for realization as an ink, the position where the balance between the number of recombinated electrons and holes is achieved changes from the photoactive layer 220 to a point A3 within the p-type GaN conductive semiconductor layer 230, thereby reducing the luminous efficiency.

[0077] Accordingly, an ultrathin LED element according to an embodiment of the present invention may further include an electron delay layer, which is adjacent to the n-type conductive semiconductor layer, to achieve a balance between the number of holes and electrons recombinating in the photoactive layer while having a geometry suitable for implementation as an ink, thereby preventing a decrease in luminous efficiency. (Refer to...) Figure 5 To explain, when the first conductive semiconductor layer is an n-type conductive semiconductor, the ultra-thin LED element 102 can have an electron delay layer 50 below the first conductive semiconductor layer 10. This prevents a decrease in luminous efficiency even when the first conductive semiconductor layer 10 is thin. Furthermore, the reduced thickness of the first conductive semiconductor layer 10 decreases the probability of electrons being trapped due to surface defects as they move along the thickness direction of the first conductive semiconductor layer 10, thus minimizing luminous loss.

[0078] For example, the electron delay layer 50 may contain one or more materials selected from the group consisting of CdS, GaS, ZnS, CdSe, CaSe, ZnSe, CdTe, GaTe, SiC, ZnO, ZnMgO, SnO2, TiO2, In2O3, Ga2O3, Si, poly(paraphenylenevinylene) and its derivatives, polyaniline, poly(3-alkylthiophene) and poly(paraphenylene). Alternatively, as another example, when the first conductive semiconductor layer 10 is a doped n-type group III nitride semiconductor layer, the electron delay layer 50 may be a group III nitride semiconductor with a doping concentration lower than that of the first conductive semiconductor layer 10.

[0079] The thickness of the electron delay layer 50 can be 1 nm to 100 nm, but is not limited to this. The thickness can be appropriately changed by considering the materials of the n-type conductive semiconductor layer, the electron delay layer, etc.

[0080] The following describes in detail each layer of the ultra-thin LED elements 101 and 102 according to an embodiment of the present invention.

[0081] Either the first conductive semiconductor layer 10 or the second conductive semiconductor layer 30 can be an n-type semiconductor layer, while the other can be a p-type semiconductor layer. The n-type and p-type semiconductor layers can be any known semiconductor layers used in light-emitting diodes, and their use is unrestricted. For example, the n-type and p-type semiconductor layers can comprise group III-V semiconductors called group III nitride materials, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen.

[0082] For example, the first conductive semiconductor layer 10 may be an n-type semiconductor layer, in which case the n-type semiconductor layer may be a semiconductor layer with In... x Al y Ga 1-x-y The semiconductor material with the composition N (0≤x≤1, 0≤y≤1, 0≤x+y≤1) may be selected from one or more of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc., and may be doped with a first conductive dopant (e.g., Si, Ge, Sn). According to a preferred embodiment of the present invention, the thickness of the first conductive semiconductor layer 10 may be 100nm to 1800nm, but is not limited thereto.

[0083] Alternatively, the second conductive semiconductor layer 30 can be a p-type semiconductor layer. In this case, the p-type semiconductor layer can be a layer with In... x Al y Ga 1-x-y The semiconductor material is composed of N (0≤x≤1, 0≤y≤1, 0≤x+y≤1), and may be selected from one or more of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc., and may be doped with a second conductive dopant (e.g., Mg). According to a preferred embodiment of the present invention, the thickness of the second conductive semiconductor layer 30 may be 50nm to 150nm, but is not limited thereto.

[0084] Furthermore, the photoactive layer 20 located between the first conductive semiconductor layer 10 and the second conductive semiconductor layer 30 can be formed as a single or multiple quantum well structure. The photoactive layer 20 can be used without limitation as a photoactive layer included in a typical LED element used in lighting, displays, etc. A coating layer (not shown) doped with a conductive dopant can also be formed above and / or below the photoactive layer 20. This coating layer can be implemented using an AlGaN layer or an InAlGaN layer. In addition, materials such as AlGaN and AlInGaN can also be used for the photoactive layer 20. With this photoactive layer 20, when an electric field is applied to the element, electrons and holes moving from the conductive semiconductor layers located above and below the photoactive layer to the photoactive layer recombine in the photoactive layer, thus emitting light. In a preferred embodiment of the present invention, the thickness of the photoactive layer 20 can be 50 nm to 200 nm, but is not limited thereto.

[0085] On the other hand, a second electrode layer 60 may be provided below the first conductive semiconductor layer 10. Alternatively, an electron delay layer 50 may be provided between the first conductive semiconductor layer 10 and the second electrode layer 60. In addition, a first electrode layer 40 may be provided above the second conductive semiconductor layer 30.

[0086] When the first electrode layer 40 and the second electrode layer 60 are electrode layers included in conventional LED components used in lighting, displays, etc., they can be used without limitation. The first electrode layer 40 and the second electrode layer 60 can be separate layers formed independently using one of Cr, Ti, Al, Au, Ni, ITO, and their oxides or alloys, or composite layers formed by mixing two or more of these materials. For example, ... Figure 5As shown, the ultra-thin LED element 102 may have a first electrode layer 42 on the second conductive semiconductor layer 30, which may have a first electrode layer 40 with a stacked ITO layer and a Ti / Au composite layer 41. In addition, the first electrode composite layer 40 and the second electrode layer 60 may be independent and have a thickness of 10nm to 500nm, but are not limited thereto.

[0087] Additionally, a selective bonding layer 70 may be included on the first electrode layers 40 and 42. The selective bonding layer 70 performs the function of assembling ultra-thin LED elements at target locations of the driving electrodes. The layer material of the selective bonding layer 70 may vary depending on the specific bonding method. For example, the selective bonding layer 70 may be a chemical bond inducing layer; specifically, such as... Figure 3a As shown, the selective bonding layer 71 can be an ion-bonded induction layer, assembled on the driving electrode with an ion-bonded induction layer carrying opposite charges via ion bonds. Additionally, as... Figure 3b As shown, the selective bonding layer 72 can be a covalent bond-inducing layer, which can be assembled with a covalent bond-inducing layer on a driving electrode having other functional groups capable of covalently bonding with the existing functional groups through covalent bonding. Additionally, as... Figure 3c As shown, the selective bonding layer 70 can be a magnetic layer 73, and the magnetic layer 73 can be assembled on the driving electrode using magnetic properties.

[0088] On the other hand, Figure 1 and Figure 2 The selective bonding layer 70 is shown to be located on the second electrode layer 60, but it is not limited thereto; it can also be configured to be located on the first electrode layer 40. In other words, the selective bonding layer 70 can be configured as the uppermost or lowermost layer of the ultrathin LED element.

[0089] Additionally, the ultra-thin LED element 101 may also include a protective film 80, which surrounds the side surface of the element when the surface parallel to the stacking direction is a side surface. The protective film 80 functions to protect the surfaces of the first conductive semiconductor layer 10, the photoactive layer 20, and the second conductive semiconductor layer 30. Furthermore, similar to a manufacturing method described later, it can protect the first conductive semiconductor layer 10 during the process of separating multiple LED pillars after etching the LED wafer in the thickness direction. As an example, the protective film 80 may contain any one or more of silicon nitride (Si3N4), silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), zirconium oxide (ZrO2), yttrium oxide (Y2O3), titanium dioxide (TiO2), aluminum nitride (AlN), and gallium nitride (GaN). The thickness of the protective film 80 can be 5nm to 100nm, more preferably 30nm to 100nm, which is beneficial for protecting the first conductive semiconductor layer 10 in the process of separating the LED pillars described later.

[0090] On the other hand, such as Figure 6 As shown, in order to achieve better luminous efficiency in addition to its protective function as a protective film, an ultra-thin LED element 103 of an embodiment of the present invention may have a protective film 80' composed of a hole-pushing film 81 and an electron-pushing film 82. The hole-pushing film 81 surrounds the exposed side of the second conductive semiconductor layer 30 or the exposed side of the second conductive semiconductor layer 30 and at least a portion of the exposed side of the photoactive layer 20 to move holes on the exposed side surface towards the center. The electron-pushing film 82 surrounds the exposed side of the first conductive semiconductor layer 10 to move electrons on the exposed side surface towards the center, so as to achieve better luminous efficiency in addition to its protective function as a protective film.

[0091] A portion of the charge moving from the first conductive semiconductor layer 10 to the photoactive layer 20 and a portion of the holes moving from the second conductive semiconductor layer 30 to the photoactive layer 20 can move along the side surface. In this case, due to defects present on the surface, electrons or holes may be hardened, thus posing a risk of reduced luminous efficiency. Even with a protective film, hardening caused by defects generated on the device surface before the protective film is formed cannot be avoided. However, when the protective film 80' is formed by a hole-pushing film 81 and an electron-pushing film 82, electrons and holes are concentrated towards the center of the device to guide their movement towards the photoactive layer, thus preventing loss of luminous efficiency due to surface defects even if defects exist on the device surface before the protective film is formed.

[0092] For example, the hole-pushing membrane 81 may comprise AlN XOne or more of the following are selected from the group consisting of ZrO2, MoO, Sc2O3, La2O3, MgO, Y2O3, Al2O3, Ga2O3, TiO2, ZnS, Ta2O5, and n-MoS2; the electron-push film 82 may contain one or more of the following: Al2O3, HfO2, SiN x SiO2, ZrO2, Sc2O3, AlN x Choose one or more from the group consisting of Ga2O3.

[0093] In addition, such as Figure 6 As shown, when the ultra-thin LED element has both hole push film 81 and electron push film 82, the electron push film 82 can be configured as the outermost film surrounding the sides of the first conductive semiconductor layer 10, the photoactive layer 20 and the second conductive semiconductor layer 30.

[0094] In addition, the hole-pushing film 81 and the electron-pushing film 82 can be independent and have a thickness of 1nm to 50nm.

[0095] On the other hand, the first conductive semiconductor layer 10, the photoactive layer 20, and the second conductive semiconductor layer 30 mentioned above can be included as the minimum constituent elements of an ultrathin film LED device. It should be noted that other phosphor layers, quantum dot layers, active layers, semiconductor layers, hole blocking layers, and / or electrode layers may also be included above / below each layer.

[0096] The ultra-thin LED element assembly 100, including the ultra-thin LED element 101 of an embodiment of the present invention described above, can be constructed by... Figure 7 The manufacturing method 1 shown or in Figure 10 The manufacturing process is shown as method 2. Method 1 is more useful when the n-type III nitride semiconductor layer is a doped n-type III nitride semiconductor layer, while method 2 is useful if the n-type III nitride semiconductor layer is undoped.

[0097] Manufacturing methods 1 and 2 range from manufacturing LED wafer 100a to manufacturing a wafer containing multiple LED structures. Figure 1 100h Figure 10 The process (100h) is the same, but the method of separating the LED structure from the wafer differs. This difference applies to the process from manufacturing LED wafer 100a to manufacturing wafers comprising multiple LED structures. Figure 1 100h Figure 10 The process of manufacturing 100h will be described using manufacturing method 1.

[0098] First, refer to Figure 7 Explanation of manufacturing method 1.

[0099] Manufacturing method 1 may include: step (1), preparing LED chip 100a ( Figure 7 (a)); Step (2), patterning the upper part of the LED chip 100a to have a target shape and size in a plane perpendicular to the direction of the stacked layers in a single LED structure. Figure 7 (b) and (c) are then etched vertically to at least a portion of the thickness of the first conductive semiconductor layer 10 to form a plurality of LED structures. Figure 7 (d)~(h)); Step (3), forming a protective film to surround the exposed surfaces of each of the plurality of LED structures and to expose the upper surface of the first portion between adjacent LED structures to the outside. Figure 7 (i)~(j)); Step (4), after immersing the LED chip in the electrolyte, it is electrically connected to any one terminal of the power supply, and the other terminal of the power supply is electrically connected to the electrode immersed in the electrolyte, and then the power supply is applied to form multiple pores. Figure 7 (k)); and step (5), applying ultrasonic waves to the LED wafer to separate the multiple LED structures from the first portion forming the multiple pores. Figure 7 (o)).

[0100] As for the LED wafer 100a prepared in step (1), any commercially available one can be used without restriction. For example, the LED wafer 100a may be composed of at least a substrate 1, a first conductive semiconductor layer 10, a photoactive layer 20, and a second conductive semiconductor layer 30. In this case, the first conductive semiconductor layer 10 may be an n-type III nitride semiconductor layer, and the second conductive semiconductor layer 30 may be a p-type III nitride semiconductor layer. In addition, in order to achieve the target thickness, the remaining LED structure after etching can be separated on the LED wafer through steps (3) to (5) after etching the n-type III nitride semiconductor layer. Therefore, there is no restriction on the thickness of the n-type III nitride semiconductor layer 10 in the LED wafer, and the presence or absence of a separate sacrificial layer can be disregarded when selecting the wafer.

[0101] Furthermore, each layer within the LED chip 100a may have a c-plane crystal structure. Additionally, the LED chip 100a may undergo a cleaning process, which can appropriately employ conventional chip cleaning solutions and processes; therefore, this invention does not impose any particular limitations on this. For example, the cleaning solution may be isopropanol, acetone, and hydrochloric acid, but is not limited to these.

[0102] Then, before performing step (2), the step of forming a first electrode layer 40 on the p-type group III nitride semiconductor layer 30 can be performed. The first electrode layer 40 can be formed by conventional methods for forming electrodes on semiconductor layers, for example by deposition using sputtering. The material of the first electrode layer 40 is the same as described above, for example, it can be ITO, and it can be formed with a thickness of about 150 nm. The first electrode layer 40 can also undergo a rapid thermal annealing process after the deposition process, for example, it can be treated at 600°C for 10 minutes, but considering that the thickness, material, etc. of the electrode layer can be appropriately adjusted, the present invention does not particularly limit this.

[0103] Subsequently, as in step (2), the upper part of the LED chip can be patterned so that the plane perpendicular to the direction of the stacked layers in the individual LED structure has the desired shape and size. Figure 7 (b) to (c)). Specifically, a mask pattern layer may be formed on the upper surface of the first electrode layer 40. The mask pattern layer may use known methods and materials used in etching LED wafers. The pattern of the pattern layer may be formed by applying conventional photolithography or nanoimprinting.

[0104] For example, such as Figure 7 As shown in (f), the mask pattern layer can be a stack of a first mask layer 2, a second mask layer 3, and a resin pattern layer 4' with a predetermined pattern formed on the first electrode layer 40. To briefly illustrate the method of forming the mask pattern layer, for example, it can be formed as follows: the first mask layer 2 and the second mask layer 3 are formed on the first electrode layer 40 by deposition, and a resin layer 4', which is the origin of the resin pattern layer 4', is formed on the second mask layer 3. Figure 7 (b) and (c) are then removed using conventional methods such as RIE (reactive ion etching) to remove the residual resin portion 4a of resin layer 4. Figure 7 (d)) The second mask layer 3 and the first mask layer 2 are sequentially etched along the pattern of the resin pattern layer 4'. Figure 7 (e) and (f)). In this case, for example, the first mask layer 2 can be formed of silicon dioxide, and the second mask layer 3 can be a metal layer such as aluminum or nickel. The etching of these can be performed by RIE and ICP (inductively coupled plasma), respectively. On the other hand, the resin pattern layer 4' can also be removed when etching the first mask layer 2 (see 100f).

[0105] In addition, such as Figure 8As shown, the resin layer 4, from which the resin pattern layer 4' originates, can be formed by nanoimprinting to create a mold 6b corresponding to the predetermined pattern model 6a of the target. Figure 8 (a) is then processed in mold 6b to form resin layer 4. Figure 8 (b) Then, the resin layer 4 is transferred onto the first electrode layer 40 so that the resin layer 4 is located on the wafer stack 100b that forms the first mask layer 2 and the second mask layer 3. Then, the mold 6b is removed, thereby realizing the wafer stack 100c with the resin layer 4 formed.

[0106] On the other hand, a method for forming patterns by nanoimprinting was explained, but it is not limited to this method. It can also be formed by photolithography using known photosensitive materials or known laser interference lithography, electron beam lithography, etc.

[0107] After that, as Figure 7 As shown in (g), the pattern of the mask pattern layers 2 and 3 formed on the first electrode layer 40 is etched in a direction perpendicular to the surface of the LED wafer 100f to a portion of the thickness of the n-type III nitride semiconductor layer, i.e., the first conductive semiconductor layer 10, thereby manufacturing an LED wafer 100g with LED structures. This etching can be performed using conventional dry etching methods such as ICP and KOH / TAMH wet etching. During this etching process, the aluminum constituting the mask pattern layer, i.e., the second mask layer 3, is removed, followed by the removal of the silicon dioxide of the mask pattern layer present on the first electrode layer 40 constituting each LED structure within the LED wafer 100g, i.e., the first mask layer 2, thereby manufacturing an LED wafer 100h with multiple LED structures.

[0108] Then, as step (3), a step is performed to form a protective film 80a to surround the exposed surfaces of each of the plurality of LED structures with a predetermined thickness in the LED wafer 100h in which the plurality of LED structures are formed, and to expose the upper surface S1 of the first portion a between adjacent LED structures to the outside. Figure 7 (i) and (j)). The protective film 80a is used to prevent damage to the LED structure due to the execution of step (4), and at the same time, it also performs the function of protecting the side surface of the individual separated LED structure from external stimuli when it remains on the side of the LED structure separated from the LED chip.

[0109] For steps (3) to (5) refer to Figure 9To explain in detail, step (3) can be performed by the following steps: depositing a protective film material on an LED wafer 100h on which multiple LED structures are formed, so that the protective film 80a surrounds the exposed surfaces of each of the multiple LED structures with a predetermined thickness (step 3-1); and removing the protective film deposited on the upper surface S1 of the first part a between adjacent LED structures to expose the upper surface S1 of the first part a between the LED structures to the outside (step 3-2).

[0110] Step 3-1 is the step of depositing a protective film material onto an LED wafer 100h on which multiple LED structures are formed. Figure 9 (a)). At this time, the protective film material can be a known material that is not chemically corroded by the electrolyte in step (4) described later. For example, the material of the protective film 80 described above can be used without limitation. Specifically, it can include one or more materials selected from the group consisting of silicon nitride (Si3N4), silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), zirconium oxide (ZrO2), yttrium oxide (Y2O3), lanthanum oxide (La2O3), scandium oxide (Sc2O3), titanium dioxide (TiO2), aluminum nitride (AlN), and gallium nitride (GaN). In addition, the thickness of the protective film 80a formed by depositing the protective film material can be 5 nm to 100 nm, and more preferably 30 μm to 100 nm. If the thickness of the protective film 80a is less than 5 nm, it is difficult to prevent the LED structure from being eroded by the electrolyte in step (2) described later; when the thickness is greater than 100 nm, there may be problems such as increased manufacturing costs and connection between LED structures.

[0111] Next, step 3-2 is the step of removing the protective film deposited on the upper surface S1 of the first portion a between adjacent LED structures to expose the upper surface S1 of the first portion a between the LED structures to the outside. Figure 9 (b) Because a protective film material is also deposited on the upper surface S1 of the first portion a between adjacent LED structures during step 3-1, the electrolyte cannot contact the n-type III nitride semiconductor, i.e., the first conductive semiconductor layer 10, and thus the target pores cannot be formed in the first portion a. Accordingly, a step is performed to remove the protective film material covering the upper surface S1 of the first portion a to expose it to the outside. At this time, the removal of the protective film material can be performed by a known dry or wet etching method.

[0112] On the other hand, according to an embodiment of the present invention, the protective film 80a formed in step (3) is a temporary protective film for preventing damage to the LED structure caused by performing step (3), and a step of forming a surface protective film surrounding the sides of the LED structure after removing the temporary protective film may be included between steps (4) and (5). That is, as Figure 7 As shown, in step (3), the protective film 5' is only used as a temporary protective film to prevent damage to the LED structure in step (4). Figure 7 (i) to (k)), before performing step (5), the protective film 5' is removed, and then a surface protective film 80 is formed to perform the function of preventing damage to the surface of the LED structure, so that the surface protective film 80 covers the side of the LED structure (i) to (k). Figure 7 (m)

[0113] On the other hand, such as Figure 7 The illustrated embodiment presents the inconvenience of forming a protective film twice, but the number of times can be chosen by considering the planar shape, size, and spacing between the LED structures being manufactured. Furthermore, during step (4) described later, partial erosion of the protective film may occur. If the eroded protective film remains on the final obtained single LED structure as a surface protective film, it may be difficult to properly perform the surface protection function. Therefore, it may be advantageous to reform the protective film after removing the protective film from step (4), depending on the circumstances.

[0114] The explanation is as described above. Figure 7 The manufacturing process shown involves depositing a temporary protective film material 5 onto an LED wafer 100h that forms multiple LED structures. Figure 7 (i) is then etched onto the upper surface S1 of the first portion a of the n-type III nitride semiconductor layer 10 doped between adjacent LED structures of the LED wafer 100i, forming a temporary protective film 5 that protects the sides and top of multiple LED structures, i.e., protective film 5'. Afterwards, step (4) described later is performed. Figure 7 (k)), and then the protective film 5' is removed by etching. Figure 7 The (l) will serve as a surface protective film for protecting the surface of the LED structure. That is, the protective film material is deposited on the LED chip 100l, and then the protective film material formed on each part of the LED structure is removed, thus forming a protective film 80 surrounding the sides of the LED structure. Figure 7At this time, not only the protective film material formed on the upper part of the LED structure, but also the protective film material deposited on the upper surface S1 of the first part a of the doped n-type III nitride semiconductor layer 10 between adjacent LED structures of the LED wafer 100m can be removed. Accordingly, in step (5) described later, the foaming solvent can contact the upper surface S1 of the first part a, and the bubbles generated by the ultrasonic waves can penetrate and form pores P in the first part a. Therefore, the LED structure can be separated by the bubbles.

[0115] On the other hand, the temporary protective film material and the surface protective film material are described in the same way as the protective film materials described above, and the film thickness can also be achieved within the thickness range of the protective film described above.

[0116] Then, as step (4) of manufacturing method 1, the LED chip is immersed in the electrolyte and then electrically connected to any one terminal of the power supply, and the other terminal of the power supply is electrically connected to the electrode immersed in the electrolyte, and then the power supply is applied to form a plurality of pores in the first part.

[0117] Specifically, referring to Figure 9 To illustrate, an LED chip 100h2 with a protective film 80a is electrically connected to any one terminal of a power supply, such as the anode, and the remaining terminal of the power supply, such as the cathode, is electrically connected to an electrode immersed in an electrolyte to apply power. This allows the fabrication of an LED chip 100h3 in which a plurality of pores P are formed on the first portion a of the doped n-type III nitride semiconductor, i.e., the first conductive semiconductor layer 10. The pores P are formed from the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor, i.e., the first conductive semiconductor layer 10, which is in direct contact with the electrolyte, in the thickness direction and on the side of the first portion a corresponding to the lower portion of each of the plurality of LED structures.

[0118] The electrolyte used in step (4) may contain one or more oxyacids selected from the group consisting of oxalic acid, phosphoric acid, sulfurous acid, sulfuric acid, carbonic acid, acetic acid, chlorous acid, bromic acid, nitrous acid, and nitric acid; more preferably, oxalic acid may be used, which has the advantage of minimizing damage to the first conductive semiconductor layer. Additionally, the electrode may be made of platinum (Pt), carbon (C), nickel (Ni), or gold (Au), for example, a platinum electrode. Furthermore, step (4) may involve applying a voltage of 3V or higher as a power source for 1 minute to 24 hours, thereby allowing pores P to be smoothly formed on the side of the first portion a corresponding to the lower part of each of the multiple LED structures, thus making it easier to separate the LED structure from the wafer in step (5). More preferably, the voltage may be 10V or higher, and more preferably, 30V or lower may be applied. If a voltage less than 3V is applied, even if the power supply application time is increased, pores cannot be successfully formed on the first part a side corresponding to the lower part of each LED structure. Therefore, it is difficult to separate them in step (5). Or, even if multiple LED structures are separated, the shapes of the separated end faces are different, so the multiple LED structures may not exhibit uniform characteristics. Preferably, the voltage can be 10V or more, and more preferably, it can be 30V or less. If a voltage less than 3V is applied, even if the power supply application time is increased, pores cannot be successfully formed on the first part a side corresponding to the lower part of each LED structure. Therefore, it is difficult to separate them in step (5). Or, even if multiple LED structures are separated, the shapes of the separated end faces are different, so the multiple LED structures may not exhibit uniform characteristics. In addition, when a voltage greater than 30V is applied, pores can be formed to the lower end of the LED structure connected to the first part a of the doped n-type III nitride semiconductor layer, i.e., the second part b, which may cause a decrease in light emission characteristics. Furthermore, in step (5) described later, separation of the LED structure is preferably performed at the boundary point between the first portion a and the second portion b of the doped n-type group III nitride semiconductor layer. However, because pores formed on the second portion b side may extend beyond the boundary point, separation may occur at a certain point on the second portion b side. Therefore, there is a risk that an LED structure with an n-type semiconductor layer having a thickness less than the originally designed n-type semiconductor layer thickness may be obtained. In addition, the power application time has a similar effect to the voltage intensity. If the application time is prolonged, there is a risk that pores will form on the second portion b outside the target portion. Conversely, if the application time is short, pore formation is not smooth, and therefore it may be difficult to separate the LED structure.

[0119] After step (4) and before step (5) described later, an LED wafer 100h4 may be manufactured by removing the protective film formed on the upper surface of each LED structure in the protective film 80a, so that it can be electrically connected to the first electrode layer 40 side after the LED structure is separated from the wafer. In addition, since only the protective film formed on the upper surface of the LED structure is removed, the protective film 80 remaining on the side of the LED structure can perform the function of protecting the side of the LED structure from the outside.

[0120] Additionally, after step (4) and before step (5) described later, a step of forming other layers on the first electrode layer 40 of the LED structure can be performed. For example, the other layers can be an ITO layer, that is, the first electrode layer 40 can also form a Ti / Au composite layer or a selective bonding layer 70 of the first electrode layer material (see reference). Figure 7 (n)).

[0121] Subsequently, as step (5) of manufacturing method 1, an ultrasonic wave is applied to the LED wafer 100h4 to separate the multiple LED structures from the first part a that forms multiple pores P.

[0122] At this point, ultrasound can be applied directly to the LED chip 100h4 with pores, or indirectly by immersing the LED chip 100h4 with pores in a solvent. However, the method of collapsing the pores P in the first part a by means of the physical external force generated by the ultrasound itself cannot successfully collapse the pores. If excessive pores are formed in order to achieve successful collapse, there is a risk that pores will form in the second part b of the LED structure, which may lead to the side effect of reducing the quality of the LED structure.

[0123] Accordingly, according to an embodiment of the present invention, step (5) can be performed using a sonochemistry method. Specifically, the LED wafer 100h4 is immersed in a foaming solution 76 (or solution), and ultrasound is applied to the foaming solution 76 (or solution). The energy generated by the bubbles generated and grown through the sonochemistry mechanism collapses the pores when they burst, thereby separating multiple LED structures. Specifically, ultrasound is generated alternately in relatively high-pressure and relatively low-pressure regions in the direction of sound wave propagation. The generated bubbles are repeatedly compressed and expanded simultaneously through the high-pressure and low-pressure regions, growing into bubbles with higher temperatures and pressures before collapsing. During collapse, these bubbles become local hotspots that generate high temperatures, such as 4000K, and high pressures, such as 1000 atmospheres. This energy is used to collapse the pores generated in the LED wafer, thereby separating the LED structures from the wafer. Ultimately, ultrasound not only performs the functions of generating bubbles in the foaming solution (or solution), growing bubbles, moving the generated bubbles and penetrating into the pores P of the first part a, but also facilitates the separation of multiple LED structures from the LED chip through the pore collapse mechanism generated by the external force generated when the unstable bubbles with high temperature and high pressure burst after penetrating into the pores P. Accordingly, an LED assembly 100' containing multiple ultra-thin LED elements 101' can be obtained.

[0124] For the foaming solution 76 (or solution), it is permissible to use a solution (or solution) that generates bubbles and grows under high pressure and high temperature when ultrasound is applied. Preferably, the foaming solution (or solution) can use a vapor pressure of 100 mmHg (20°C) or less. As another example, it can use a vapor pressure of 80 mmHg (20°C) or less, 60 mmHg (20°C) or less, 50 mmHg (20°C) or less, 40 mmHg (20°C) or less, 30 mmHg (20°C) or less, 20 mmHg (20°C) or less, or 10 mmHg (20°C) or less. If a solvent with a vapor pressure exceeding 100 mmHg (20°C) is used, it is impossible to separate normally in a short time, thus posing a risk of prolonged manufacturing time and increased production costs. For the foaming solution 76 that satisfies the physical properties described above, as an example, it can be one or more selected from the group consisting of γ-butyrolactone, propylene glycol monomethyl ether acetate, methylpyrrolidone, and 2-methoxyethanol. On the other hand, a solution (or solution) at room temperature, such as 20°C with a vapor pressure of 100 mmHg, can also be used. However, it should be noted that step (3) can also be performed by adjusting the conditions for performing step (5) differently, such as adjusting the conditions so that the vapor pressure of the foaming solution (or solution) is below 100 mmHg (for example, low temperature conditions, etc.). In this case, the restrictions on the types of solvents that can be used can be further relaxed, and for example, solvents such as water, acetone, chloroform, and alcohol can also be used.

[0125] Furthermore, the wavelength of the ultrasound applied in step (5) can be at a frequency that can create a region capable of inducing an ultrasonic chemical reaction, specifically at a frequency that allows for the growth and collapse of bubbles to form local hotspots with high pressure and high temperature during bubble collapse. For example, this could be 10 kHz to 2 MHz, and the ultrasound application time could be from 1 minute to 24 hours. This allows for easy separation of the LED structure from the LED chip. Even if the wavelength of the applied ultrasound is within this range, a low intensity or short application time may increase the risk of unseparated LED structures or an increase in the number of unseparated LED structures. Additionally, a high intensity or long application time may damage the LED structure.

[0126] On the other hand, in order to form the second electrode layer 60 on the first conductive semiconductor layer 10, before performing the above-described step (5), a step of attaching the support film 9 to the LED wafer 100n to form other layers on the first conductive semiconductor layer 10, such as the second electrode layer 60 or an electron delay layer (not shown), may also be performed. Figure 7 After performing step (5), multiple LED structures can be separated in the state of having the support film 9 attached. Figure 7 (p)). Then, a second electrode layer 60 is formed by a known method, such as depositing a second electrode layer 60 on top of multiple LED structures in the state of an attached support film 9. Figure 7 (q)) After removing the support film, an assembly of multiple ultra-thin LED elements 101 can be obtained 100.

[0127] Then, refer to Figure 10 This describes a method for manufacturing ultra-thin LED components using manufacturing method 2.

[0128] As described above, the process of forming an LED wafer 100h with multiple LED structures from an LED wafer is the same as manufacturing method 1. Then, for the LED wafer 100h with multiple LED structures formed, the following steps can be performed: Step (i), forming an insulating film 8 to cover the exposed sides of the multiple LED structures ( Figure 10 (b)); Step (ii), in order to expose the upper surface S1 of the first conductive semiconductor layer 10 between adjacent LED structures, a portion of the insulating film formed on the upper part of the first conductive semiconductor layer 10 is removed. Figure 10 (c)); Step (iii), the first conductive semiconductor layer 10 is further etched in the thickness direction through the exposed upper surface S1 of the first conductive semiconductor layer, and a portion of the first conductive semiconductor layer with a predetermined thickness of exposed side is formed below the first conductive semiconductor layer of the micro-nano needle LED pillar on which the insulating film 8' is formed. Figure 10 (c)); Step (iv) involves etching the first conductive semiconductor layer portion exposing the sides from both sides toward the center. Figure 10 (d)); Step (v), remove the insulating film 8 ( Figure 10 (e)); Step (vi) forms a protective film 80 on the sides of multiple LED structures. Figure 10 (f)); Step (vii), remove the protective film formed on the upper part of the multiple LED structures to expose the first electrode layer 40 ( Figure 10 (g)); Step (ⅷ), forming a selective bonding layer 70 on the first electrode layer 40. Figure 10 (h) and step (x), separating multiple LED structures from the LED wafer to manufacture an ultra-thin LED assembly 100' comprising multiple ultra-thin LED elements 101'. On the other hand, the above-described manufacturing method 2 can be performed using known methods for manufacturing LED elements, and a detailed description of this is based on the inventors' patent application number 2020-0050884. As a reference insertion for this invention, the detailed description of each step of manufacturing method 2 is omitted in this invention.

[0129] At this point, in step (ⅸ), the separation of multiple LED structures can be achieved by cutting with a cutting tool or by peeling off the adhesive film.

[0130] On the other hand, through Figure 6 The protective film 80', consisting of a hole-pushing film 81 and an electron-pushing film 82 to improve luminous efficiency, can be formed as a protective film. The manufacturing method for this will refer to... Figure 11 Please provide an explanation.

[0131] With the above Figure 7 , 9 The difference between 10 and 10 is that the following process is executed twice ( Figure 11 (b), (d), (e)): During vertical etching, instead of etching to a portion of the first conductive semiconductor layer 10, which is an n-type semiconductor, the first etching reaches the second conductive semiconductor layer 30 or a portion or all of the second conductive semiconductor layer 30 and the photoactive layer 20. Figure 11 (a)), then a second etching is performed to a portion of the thickness of the first conductive semiconductor layer 10. Figure 11 (c) and deposit thin film material, removing the thin film material between multiple LED structures.

[0132] Specifically, the following process is performed: when etching the LED wafer in a vertical direction, instead of etching to a portion of the first conductive semiconductor layer 10, which is an n-type semiconductor, the first etching only reaches the second conductive semiconductor layer 30, or a portion or all of the second conductive semiconductor layer 30 and the photoactive layer 20. Figure 11 (a)), followed by deposition of hole-push film material 81a ( Figure 11 (b) is then removed, followed by the removal of hole-repelling material formed between the LED structures. Afterwards, the following process can be performed: the first conductive semiconductor layer 10 is re-etched to a predetermined thickness (b) Figure 11 (c) Then, an electron-push film material 82a is deposited on the LED structure having the hole-push film 81b. Figure 11 (d)), and then the electron repulsion material formed on the upper surface S1 between the LED structures is removed again. Figure 11 (e)). Then, the above is executed. Figure 7 and Figure 9 The process of separating LED structures in the middle ( Figure 7 Below (k), Figure 9 (d) below) or in Figure 10 The process of separating LED structures in the middle ( Figure 10 (d) and below), thus the ultra-thin LED element 103 can be separated from the LED chip.

[0133] The ultra-thin LED elements 101, 102, and 103 obtained by the above method can be realized as inkjet ink compositions. The ink composition may also contain dispersion media, other additives, etc., as known in inkjet ink compositions, and the present invention does not impose any particular limitations on this.

[0134] Furthermore, the present invention includes a light source comprising the aforementioned ultra-thin LED elements 101, 102, and 103. As an example, the light source can be various LED lighting devices, displays, medical devices, beauty devices, various optical devices, and components constituting these devices, such as those for home / automotive use.

[0135] The present invention will be described in more detail below through the following embodiments. However, the following embodiments do not limit the scope of the present invention, but should be interpreted as being for understanding the present invention.

[0136] (Example 1)

[0137] A conventional LED wafer (Epistar) was prepared by sequentially stacking an undoped n-type III nitride semiconductor layer, a Si-doped n-type III nitride semiconductor layer (4 μm thick), a photoactive layer (0.45 μm thick), and a p-type III nitride semiconductor layer (0.05 μm thick) on a substrate. ITO (0.15 μm thick) as a first electrode layer, SiO2 (1.2 μm thick) as a first mask layer, and Al (0.2 μm thick) as a second mask layer were sequentially deposited on the prepared LED wafer. Then, a patterned SOG resin layer was transferred to the second mask layer using a nanoimprint lithography device. Next, the SOG resin layer was cured using RIE, and the residual resin portion of the resin layer was etched using RIE to form a resin pattern layer. Then, the second mask layer was etched along the pattern using ICP, and the first mask layer was etched using RIE. Subsequently, the first electrode layer, p-type III nitride semiconductor layer, and photoactive layer were etched using ICP. Then, the doped n-type III nitride semiconductor layer was etched to a thickness of 0.78 μm. To ensure the sidewalls of the etched doped n-type III nitride semiconductor layer were perpendicular to the layer sidewalls, KOH wet etching was used to fabricate an LED wafer with multiple LED structures (850 nm in diameter and 850 nm in height). Finally, a protective film material, SiN, was deposited on the LED wafer with the multiple LED structures. x (Refer to Figure 12 The SEM images, taken from the side of the LED structure (with deposition thicknesses of 52.5 nm and 72.5 nm), were then removed using a reactive ion etching machine to remove the protective film material formed between multiple LED structures, exposing the upper surface S1 of the first part a of the doped n-type III nitride semiconductor layer.

[0138] Next, the LED chip with the temporary protective film formed is immersed in an electrolyte, namely a 0.3M oxalic acid aqueous solution, and then connected to the anode terminal of the power supply. The platinum electrode immersed in the electrolyte is connected to the cathode terminal, and then a 10V voltage is applied for 5 minutes. Figure 13 As shown in the SEM image, multiple pores are formed from the surface of the first portion a of the doped n-type III nitride semiconductor layer to a depth of 600 nm. Subsequently, a temporary protective film is removed by RIE, followed by the deposition of a 50 nm thick surface protective film, Al2O3, on the LED wafer, with the side of the LED structure as the reference. The surface protective films formed on the upper parts of the multiple LED structures and the surface protective film formed on the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer are removed by ICP, exposing the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer and the upper surface of the LED structure. The LED wafer is then immersed in a foaming solution, γ-butyrolactone, and irradiated with ultrasound at a frequency of 40 kHz for 10 minutes to generate bubbles. These bubbles collapse within the pores formed in the doped n-type III nitride semiconductor layer, thus... Figure 14 The SEM images show an ultra-thin LED assembly containing ultra-thin LED elements, formed by separating multiple LED structures from a wafer. Additionally, as... Figure 15 It can be confirmed that there are no unseparated LED structures on the chip.

[0139] (Comparative Example 1)

[0140] A rod-shaped LED element assembly with the same stacked structure as Example 1, with a diameter of 650 nm and a height of 4.2 μm, was manufactured from LED wafers using conventional methods.

[0141] (Experimental Example 1)

[0142] The LED element assemblies manufactured according to Example 1 and Comparative Example 1 were respectively immersed in acetone and then dispersed by ultrasonic irradiation at 100W. The absorbance was measured at 15-minute intervals to detect and confirm the dispersion state of the LED elements after 2 hours. The absorbance curves of the ultra-thin LED element assembly of Example 1 at each detection time point are shown in the figure. Figure 16 The absorbance curves of the rod-shaped LED element assembly of Comparative Example 1 at various detection time periods are shown in the figure. Figure 17 As shown, the spectral area of ​​the visible light region from 380nm to 780nm is standardized in the detection results, such as... Figure 18 The absorbance curves for each time period are shown.

[0143] pass Figure 18 It can be confirmed that the ultra-thin LED element of Example 1 has excellent long-term dispersion retention in acetone solvent compared to the rod-shaped LED element of Comparative Example 1.

[0144] The above describes one embodiment of the present invention. However, the concept of the present invention is not limited to the embodiment presented in this specification. Those skilled in the art who understand the concept of the present invention can easily propose other embodiments by adding, changing, deleting, or adding constituent elements within the same conceptual scope, and these are also included within the conceptual scope of the present invention.

Claims

1. An ultra-thin LED element, comprising at least: The first conductive semiconductor layer, the photoactive layer, and the second conductive semiconductor layer have a thickness in the stacking direction and a length in the major axis of the cross-section perpendicular to the stacking direction in a ratio of 1:0.5 to 1.5, and the maximum area of ​​the ultra-thin LED element is 4.0 μm. 2 In the following, the maximum area refers to the maximum value of the area of ​​the vertically projected LED element.

2. The ultra-thin LED element according to claim 1, characterized in that, Either the first conductive semiconductor layer or the second conductive semiconductor layer is an n-type group III nitride semiconductor layer, and the other is a p-type group III nitride semiconductor layer.

3. The ultra-thin LED element according to claim 1, characterized in that, The thickness of the ultra-thin LED element is less than 2.7 μm.

4. The ultra-thin LED element according to claim 1, characterized in that, The first conductive semiconductor layer is an n-type group III nitride semiconductor layer, and an electron delay layer is further included below the first conductive semiconductor layer to balance the number of electrons and holes recombinating in the photoactive layer.

5. The ultra-thin LED element according to claim 4, characterized in that, The electronic delay layer comprises one or more selected from the group consisting of CdS, GaS, ZnS, CdSe, CaSe, ZnSe, CdTe, GaTe, SiC, ZnO, ZnMgO, SnO2, TiO2, In2O3, Ga2O3, Si, poly(p-phenylenevinylene) and its derivatives, polyaniline, poly(3-alkylthiophene), and poly(p-phenylene).

6. The ultra-thin LED element according to claim 4, characterized in that, The first conductive semiconductor layer is a doped n-type group III nitride semiconductor layer, and the electron delay layer is a group III nitride semiconductor with a doping concentration lower than that of the first conductive semiconductor layer.

7. The ultra-thin LED element according to claim 1, characterized in that, Also includes: A protective film surrounds the exposed sides of the ultra-thin LED element.

8. The ultra-thin LED element according to claim 1, characterized in that, The first conductive semiconductor layer is an n-type group III nitride semiconductor layer, and the second conductive semiconductor layer is a p-type group III nitride semiconductor layer. The ultra-thin LED element further includes at least one of a hole-pushing film and an electron-pushing film, wherein the hole-pushing film surrounds the exposed side of the second conductive semiconductor layer or the exposed side of the second conductive semiconductor layer and at least a portion of the exposed side of the photoactive layer to move the holes on the exposed side surface towards the center. The electron pusher film surrounds the exposed side of the first conductive semiconductor layer to move electrons from the exposed side surface towards the center.

9. The ultra-thin LED element according to claim 8, characterized in that, The hole-pushing film and the electron-pushing film are both included, with the electron-pushing film being the outermost film. The outermost film surrounds the sides of the first conductive semiconductor layer, the photoactive layer, and the second conductive semiconductor layer.

10. The ultra-thin LED element according to claim 8, characterized in that, The cavitation membrane comprises components derived from AlN X Choose one or more from the group consisting of ZrO2, MoO, Sc2O3, La2O3, MgO, Y2O3, Al2O3, Ga2O3, TiO2, ZnS, Ta2O5 and n-MoS2.

11. The ultra-thin LED element according to claim 8, characterized in that, The electron-particle film comprises Al2O3, HfO2, and SiN. x SiO2, ZrO2, Sc2O3, AlN x Choose one or more from the group consisting of Ga2O3.

12. The ultra-thin LED element according to claim 1, characterized in that, The ultra-thin LED element further includes: a second electrode layer disposed on the first conductive semiconductor layer; and a first electrode layer disposed on the second conductive semiconductor layer.

13. The ultra-thin LED element according to claim 1, characterized in that, The top or bottom layer of the ultra-thin LED element also includes a selective bonding layer, which is used to assemble the ultra-thin LED element by erecting it in the thickness direction at the target position of the driving electrode. The selective binding layer is a magnetic layer or a chemical bond-inducing layer.

14. An inkjet ink composition comprising an ultra-thin LED element as described in any one of claims 1 to 13.

15. A light source having an ultra-thin LED element as described in any one of claims 1 to 13.

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