Micro-led light emitting unit for display device and method of manufacturing same

Abstract

The present invention relates to a display device using a micro-LED for a display device and a method of manufacturing same, the micro-LED being capable of solving a short-circuit problem between a P-type semiconductor layer and an N-type semiconductor layer of the micro-LED by forming a short-circuit prevention layer, and also suppressing occurrence of voids by controlling the spacing and thickness of wells when forming the short-circuit prevention layer.

Description

Micro LED light-emitting unit for display device and manufacturing method thereof

[0001] The present invention relates to a technology for manufacturing a display device using a micro LED (micro Light Emitting Diode; micro-LED).

[0002] More specifically, the present invention relates to a micro LED light-emitting unit for a display device and a manufacturing method thereof, which can solve a short-circuit problem between a P-type semiconductor layer and an N-type semiconductor layer of a micro LED by forming a short-circuit prevention layer, and also suppress the occurrence of voids when forming the short-circuit prevention layer.

[0003] The research subject information of the present invention is as follows.

[0004] Subproject No.: 00420281, Ministry: Ministry of Trade, Industry and Energy, Project Management Agency: Korea Institute of Industrial Technology Planning and Evaluation, Research Project Name: Electronic Components Industry Technology Development, Research Project Name: Development of MOCVD Equipment Technology for Single Cluster-Type 6-inch Nitride High-Temperature Growth for High-Uniformity (Wavelength Uniformity ≤ ±2㎚) LED Characteristics, Project Implementing Organization: Advanced View Technology, Research Period: 2024.04.01-2026.12.31

[0005] Flat panel displays include LCD (Liquid Crystal Display), OLED (Organic Light Emitting Diode) displays, and micro LED displays.

[0006] Among these, LCDs lack a light-emitting device within the display panel, requiring a separate backlight unit to supply light to the display panel. Light-emitting diodes (LEDs) are typically used as light sources in these backlight units.

[0007] OLED displays feature self-luminous OLEDs within the display panel, eliminating the need for a separate backlight. Furthermore, OLED displays offer advantages such as fast response times, high brightness, and wide viewing angles. However, OLED displays require encapsulation technology to prevent moisture and air from penetrating the OLEDs, as they contain organic materials that are vulnerable to moisture and air infiltration.

[0008] Meanwhile, micro LED displays, which feature micro LEDs measuring up to 500㎛ in length within the display panel, do not require a separate backlight unit. This is a remarkably small size compared to the LEDs used in general lighting. Micro LEDs are known to be approximately 20% more energy efficient than standard LEDs, and their small size also results in lower heat generation and power consumption. Due to these advantages, extensive research is being conducted to apply micro LEDs to displays.

[0009] In manufacturing micro LED displays, the key is to precisely position the micro LEDs in predetermined locations on the display panel. Conventionally, micro LEDs were transferred to the display panel using a support. Recently, extensive research has been conducted on technologies that utilize electric fields, such as dielectrophoresis, to position micro LEDs dispersed in a solution onto the display panel.

[0010] Korean Patent Publication No. 10-1436123 (published on November 3, 2014; hereinafter, “Patent Document 1”) discloses a method of placing a solution containing multiple micro LEDs on multiple electrode pairs by applying power to the multiple electrode pairs, thereby arranging the multiple micro LEDs on each electrode pair. However, a high voltage is applied to each electrode pair, and thus, when the micro LEDs come into contact with the electrode pairs, an overvoltage may be applied to both ends of the micro LEDs, potentially resulting in damage to the micro LEDs.

[0011] To address the issue of micro LED damage caused by direct contact between the micro LEDs and the electrode pairs during micro LED arrays, as described in Patent Document 1, a method utilizing wells has been proposed. Specifically, this method involves forming an insulating layer on a substrate on which bottom electrode pairs are formed, forming a well over each bottom electrode pair through etching, and then arranging the micro LEDs within the wells using dielectrophoresis.

[0012] Meanwhile, when forming a well, a step is generated due to the presence of a bottom electrode pair, and the micro LED does not contact the bottom of the well but rather the step portion. In this state, if an electrode pad such as ITO (Indium Tin Oxide) is deposited for electrical connection of the micro LED, the P-type semiconductor layer and N-type semiconductor layer may not be electrically separated, resulting in a short circuit.

[0013] The problem to be solved by the present invention is to provide a micro LED light-emitting unit for a display device and a manufacturing method thereof, which can solve the short-circuit problem between a P-type semiconductor layer and an N-type semiconductor layer by forming a short-circuit prevention layer.

[0014] In addition, the problem to be solved by the present invention is to provide a micro LED light emitting unit for a display device and a manufacturing method thereof that can suppress the occurrence of voids when forming a short-circuit prevention layer.

[0015] The purposes of the present invention are not limited to the purposes mentioned above, and other purposes and advantages of the present invention that are not mentioned can be understood through the following description or examples.

[0016] According to an embodiment of the present invention for solving the above problem, a micro LED light-emitting unit comprises: a substrate; a plurality of bottom electrode pairs, each pair including a first bottom electrode and a second bottom electrode spaced apart from each other on the substrate; an insulating layer covering the substrate on which the plurality of bottom electrode pairs are formed; wherein a well is formed in the insulating layer at each upper portion of a region between the first bottom electrodes and the second bottom electrodes of the plurality of bottom electrode pairs, each well including a first bottom surface and a second bottom surface at an edge of the first bottom surface and located higher than the first bottom surface; a plurality of micro LEDs arranged to contact the second bottom surface of each well; a short-circuit prevention layer formed on an upper surface of the micro LED, excluding a portion between a lower surface of the micro LED and the first bottom surface, between the micro LED and a sidewall of the well, and both edges of the upper surface of the micro LED, in the well in which the micro LED is arranged; And a plurality of transparent electrode pairs, each of which includes a first transparent electrode electrically connected to one edge exposed upwardly of the micro LED, and a second transparent electrode electrically connected to the other edge exposed upwardly of the micro LED.

[0017] It is preferable that one side wall of the well vertically overlaps with the first bottom electrode, and the other side wall of the well vertically overlaps with the second bottom electrode.

[0018] Both the above insulating layer and the above short-circuit prevention layer can be formed of a material containing SiO2.

[0019] The first transparent electrode of the plurality of transparent electrode pairs may be extended to contact one side of the micro LED, and the second transparent electrode of the plurality of transparent electrode pairs may be extended to contact the other side of the micro LED.

[0020] It is preferable that the spacing between a well and another adjacent well be 5 to 10 μm.

[0021] The depth of the above well is preferably 0.3 µm to 0.9 µm.

[0022] It is desirable that one micro LED is placed in one well.

[0023] According to an embodiment of the present invention for solving the above problem, a method for manufacturing a micro LED light-emitting unit comprises the steps of: forming a plurality of bottom electrode pairs, each pair including a first bottom electrode and a second bottom electrode spaced apart from each other, on a substrate; forming an insulating layer on the substrate on which the plurality of bottom electrode pairs are formed; etching portions of the insulating layer corresponding to the upper portion of a region between the first bottom electrodes and the second bottom electrodes of the plurality of bottom electrode pairs, to form a plurality of wells, each well including a first bottom surface and a second bottom surface higher than the first bottom surface at an edge of the first bottom surface; arranging a plurality of micro LEDs so as to contact the second bottom surface of each well; forming a short-circuit prevention layer, in the well in which the micro LEDs are arranged, on an upper surface of the micro LED excluding a lower surface of the micro LED and the first bottom surface, a between the micro LED and a sidewall of the well, and both edges of the upper surface of the micro LED; And a step of forming a plurality of transparent electrode pairs, each pair including a first transparent electrode electrically connected to one edge exposed to the upper side of the micro LED and a second transparent electrode electrically connected to the other edge exposed to the upper side of the micro LED; wherein the short-circuit prevention layer is formed by a method including spin coating.

[0024] Both the above insulating layer and the short-circuit prevention layer may be formed of a material containing SiO2. Preferably, the short-circuit prevention layer may be formed by a process of spin-coating a solution containing a silicate compound, an organic solvent, and distilled water, followed by heat treatment.

[0025] The step of forming the short-circuit prevention layer may include a step of performing spin coating over the entire surface including the inside of the well in which the micro LED is placed, and a step of exposing both edges of the upper surface of the micro LED and the side surface of the micro LED through a patterning process.

[0026] In the step of forming the plurality of wells, the size of the well can be controlled so that one side wall of the well vertically overlaps with the first bottom electrode, and the other side wall of the well vertically overlaps with the second bottom electrode.

[0027] In the step of forming the above plurality of wells, the interval between any well and another well adjacent thereto can be controlled to 5 μm to 10 μm.

[0028] In the step of forming the plurality of wells, it is preferable to form the depth of the wells to be 0.3 µm to 0.9 µm.

[0029] According to the micro LED light-emitting unit and its manufacturing method according to the present invention, the gap between the insulating layer and the micro LED is filled with, for example, SiO2, etc. by spin coating to fix the micro LED, thereby suppressing the possibility of a short circuit occurring between the P-type semiconductor layer and the N-type semiconductor layer of the micro LED when forming a subsequent transparent electrode layer.

[0030] In addition, in the case of the present invention, by forming both the insulating layer and the short-circuit prevention layer with SiO2, the alignment position of the micro LED can be maintained even if the groove size of the insulating layer is large, and defects and failures of the LED element can be prevented, resulting in an excellent yield.

[0031] In particular, in the case of the present invention, by controlling the depth of the well and the spacing between wells, the presence of voids between the insulating layer and the micro LED can be suppressed, thereby contributing to improved luminous efficiency and operating reliability.

[0032] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0033] Figure 1 schematically illustrates a plane of a micro LED light-emitting unit according to an embodiment of the present invention.

[0034] Figure 2 schematically illustrates an example of the AA cross-section of Figure 1.

[0035] Figure 3 schematically illustrates an example of the structure of the well of Figure 2.

[0036] Figure 4 is an enlarged view of part B of Figure 2.

[0037] FIGS. 5A to 5E schematically illustrate each step of a method for manufacturing a micro LED light-emitting unit according to an embodiment of the present invention. FIG. 5A illustrates an example in which a bottom electrode pair is formed on a substrate, FIG. 5B illustrates an example in which an insulating layer including a well is formed, FIG. 5C illustrates an example in which a micro LED is arranged in a well, FIG. 5D illustrates an example in which a short-circuit prevention layer is formed, and FIG. 5E illustrates an example in which a transparent electrode pair is formed.

[0038] <Explanation of symbols>

[0039] 110: Substrate

[0040] 120: Bottom electrode pair

[0041] 130: Insulating layer

[0042] 135: Well

[0043] 140: Micro LED

[0044] 150: Short-circuit prevention layer

[0045] 160: Transparent electrode pair

[0046] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification. The sizes and relative sizes of layers and regions in the drawings may be exaggerated for clarity of description.

[0047] When an element or layer is referred to as being "on" or "over" another element, it includes not only being directly on top of the other element or layer, but also having other layers or elements intervening therebetween. Conversely, when an element is referred to as being "directly on" or "directly above" it indicates that there are no other elements or layers intervening therebetween. Furthermore, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that the components may be "connected," "coupled," or "connected" through other components.

[0048] The terminology used herein is for the purpose of describing embodiments and is therefore not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, operations, and / or elements mentioned.

[0049] Hereinafter, a micro LED light emitting unit for a display device and a manufacturing method thereof according to some embodiments of the present invention will be described.

[0050] Fig. 1 schematically illustrates a plan view of a micro LED light-emitting unit according to an embodiment of the present invention. Fig. 2 schematically illustrates an example of a cross-section taken along line AA of Fig. 1. Fig. 3 schematically illustrates an example of the structure of the well of Fig. 2. Fig. 4 is an enlarged view of part B of Fig. 2.

[0051] Referring to FIGS. 1 to 4, a micro LED light emitting unit according to an embodiment of the present invention includes a substrate (110), a plurality of bottom electrode pairs (120), an insulating layer (130), a plurality of wells (135), a plurality of micro LEDs (140), a short-circuit prevention layer (150), and a plurality of transparent electrode pairs (160).

[0052] The substrate (110) may be, for example, an active matrix backplane including a TFT (Thin Film Transistor) structure. The micro LED light-emitting unit according to the present invention may be driven by, for example, a TFT. The substrate (110) may be a glass substrate, a silicon substrate, a sapphire substrate, a GaN substrate, or the like. In addition, the substrate (110) may be a plastic substrate such as polyimide. An insulating layer such as SiO2 or Al2O3 may be formed on the uppermost surface of the substrate (110).

[0053] The plurality of bottom electrode pairs (120) each include a first bottom electrode (120a) and a second bottom electrode (120b) spaced apart from each other on the substrate (110). Each of the first bottom electrode (120a) and the second bottom electrode (120b) may include a commonly used metal or conductive metal oxide, for example, may include at least one of Al, Ti, In, Cr, Au, Ni, and ITO, and more preferably may include Au. The thickness of the first bottom electrode (120a) and the second bottom electrode (120b) may be 10 to 100 nm, but is not limited thereto.

[0054] An insulating layer (130) is formed to cover a substrate (110) on which a plurality of bottom electrode pairs (120) are formed. The insulating layer (130) may be formed of an organic material such as PMGI (polydimethylglutarimide) or an inorganic material such as SiO2.

[0055] However, when an organic material such as PMGI is applied as the insulating layer (130), it is generally vulnerable to heat and chemical resistance, which may result in limitations in subsequent processes. In addition, when an organic material such as PMGI is applied as the insulating layer (130), the adhesive strength with the micro LED is weak, which increases the possibility of the micro LED being detached from the well of the insulating layer during subsequent processes.

[0056] Inorganic materials such as SiO2 have a dielectric constant (K) of approximately 3.9 to 4.2, which is similar to that of previously used materials (PMGI), allowing for smooth dielectric conduction. Furthermore, inorganic materials such as SiO2 can be applied to high frequencies, enabling the creation of finer circuits. Furthermore, SiO2 and micro LEDs exhibit excellent adhesion, enabling stable processing without concerns about detachment of the micro LED during subsequent processes.

[0057] Therefore, it is more preferable that the insulating layer (130) be formed of an inorganic material such as SiO2.

[0058] A plurality of wells (135) are formed in the insulating layer (130). Each of the plurality of wells is formed in the upper portion of the region between the first bottom electrode (120a) and the second bottom electrode (120b) of the bottom electrode pair.

[0059] Each well (135) is formed by an etching process of an insulating layer. Referring to FIG. 4, each well (135) includes a first bottom surface (135a), a second bottom surface (135b), and a side wall (135c). The second bottom surface (135b) is formed at the edge of the first bottom surface (135a) and is also formed at a higher position than the first bottom surface (135a). For example, when the insulating layer (130) is formed through a SiO2 deposition process, due to the presence of the bottom electrode pair (120), the portion corresponding to the upper portion of each of the first bottom electrode (120a) and the second bottom electrode (120b) is formed higher than the portion corresponding between the first bottom electrode (120a) and the second bottom electrode (120b), and therefore, during etching for well formation, the second bottom surface (135b) can be formed at a higher position than the first bottom surface (135a), as in the example illustrated in FIG. 3.

[0060] A plurality of micro LEDs (140) are arranged to contact the second bottom surface (135b) of each well.

[0061] The micro LED (140) may be a nitride semiconductor-based LED such as GaN. The micro LED (140) usable in the present invention may be, for example, a nanorod-type or core-shell-type device having an aspect ratio of approximately 1 to 10 and a length of 1 μm to 100 μm. The nanorod-type micro LED may include an N-type semiconductor layer, an active layer, and a P-type semiconductor layer from the bottom, and a transparent electrode layer may be additionally included on the P-type semiconductor layer. The core-shell-type micro LED may include an N-type semiconductor layer, an active layer, and a P-type semiconductor layer from the inside, and a transparent electrode layer may be additionally included on the surface of the P-type semiconductor layer.

[0062] In the present invention, each micro LED (140) is positioned within a well using a dielectrophoresis method. Using dielectrophoresis, the micro LEDs are moved and arranged at a predetermined location by a force generated along the gradient direction of the electric field. The magnitude and direction of the force generated during dielectrophoresis are affected by the permittivity and conductivity of the medium and the frequency of the applied AC electric field.

[0063] For desirable dielectric conduction, each sidewall of the well (135) may vertically overlap with the bottom electrode. That is, one sidewall of the well (135) may vertically overlap with the first bottom electrode, and the other sidewall of the well may vertically overlap with the second bottom electrode. This can advantageously increase the size of the electric field locally and selectively align the micro LEDs.

[0064] The short-circuit prevention layer (150) prevents the P-type semiconductor layer and the N-type semiconductor layer of the micro LED from being electrically connected, that is, from causing a short. For example, when the micro LED is placed so as to be in contact with the second bottom surface of the well, a gap is formed between the first bottom surface of the well and the micro LED. When a transparent electrode is subsequently deposited, the transparent electrode is deposited in this gap, so that the P-type semiconductor layer and the N-type semiconductor layer of the micro LED are not electrically separated, which may cause a short-circuit phenomenon. At this time, if the gap between the first bottom surface of the well and the micro LED is filled with the short-circuit prevention layer (150), the short-circuit between the P-type semiconductor layer and the N-type semiconductor layer can be prevented. For this purpose, the short-circuit prevention layer (150) is formed of an insulator.

[0065] The short-circuit prevention layer (150) is formed on the upper surface of the micro LED excluding both edges of the upper surface of the micro LED, between the lower surface of the micro LED and the first bottom surface, between the micro LED and the side wall of the well, and in the well where the micro LED is placed. Here, the lower surface and the upper surface of the micro LED are based on the state in which the micro LED is placed. The short-circuit prevention layer (150) includes a first short-circuit prevention portion (150a) formed between the lower surface of the micro LED (140) and the first bottom surface (135a), a second short-circuit prevention portion (150b) formed between the micro LED (140) and the side wall (135b) of the well, and a third short-circuit prevention portion (150c) formed on the upper surface of the micro LED (140).

[0066] The short-circuit prevention layer (150) may be formed through a spin coating process. Preferably, both the insulating layer (130) and the short-circuit prevention layer (150) may be formed of a material containing SiO2. By forming the insulating layer and the short-circuit prevention layer from the same material containing SiO2, the adhesion of the short-circuit prevention layer to the insulating layer can be maximized.

[0067] A plurality of transparent electrode pairs (160) are respectively connected to the P-type semiconductor layer and the N-type semiconductor layer of the micro LED (140). Specifically, the plurality of transparent electrode pairs (160) each include a first transparent electrode electrically connected to one edge exposed upwardly of the micro LED, and a second transparent electrode electrically connected to the other edge exposed upwardly of the micro LED.

[0068] For example, as in the example illustrated in FIG. 3, the first transparent electrode (160a) of the plurality of transparent electrode pairs may be extended to contact a portion of a side surface of one side of the micro LED, and the second transparent electrode (160b) of the plurality of transparent electrode pairs may be extended to contact a portion of a side surface of the other side of the micro LED. In this case, the contact area between each transparent electrode and the micro LED may be expanded, thereby increasing operational reliability.

[0069] The spacing between a well and another adjacent well (a in FIG. 1) may be 5 μm to 10 μm, preferably 6 μm to 10 μm, and more preferably 8 μm to 10 μm. If the spacing between wells (a) is too short, less than 5 μm, a void may occur in the gap between the side wall of the well and the micro LED or in the gap between the bottom of the well, i.e., the first bottom surface (135a) of the well and the micro LED, so that part or all of the gap may not be filled.

[0070] The causes of void generation are as follows. When forming a short-circuit prevention layer using the spin coating method applied to the present invention, a curing process must be performed after spin coating due to the process and material characteristics. At this time, shrinkage of the film occurs during the curing process, and if the coating is not performed properly, a hole, i.e., a void, may be generated in the film due to the shrinkage during the curing process. What is unique in the present invention is that voids occurred when the spacing (a) between wells was too short, less than 5 μm. This appears to be because the space between the sidewall and the micro LED was not properly coated due to interference between wells during spin coating.

[0071] When voids occur, the following problems arise. Voids tend to appear in random locations, making subsequent process control difficult. Furthermore, if these voids occur at the bottom of the micro LED, they can prevent it from functioning as a protective layer.

[0072] Meanwhile, when the spacing between wells exceeds 10㎛, the size of the micro LED light-emitting unit and the display device including the same increases without increasing the effect.

[0073] Referring to FIGS. 2 and 3, in the present invention, the depth (b) of the well corresponds to the height from the second bottom surface (135b) of the well to the top of the well. The depth of the well is determined by the thickness of the bottom electrode pair (120), the thickness of the insulating layer (130), and the etching process for forming the well. The depth of the well is preferably 0.3 to 0.9 μm, and more preferably 0.3 to 0.7 μm. If the depth of the well is too small, less than 0.3 μm, there is a possibility that the micro LED may be detached from the well during a subsequent process. Conversely, if the depth of the well exceeds 0.9 μm, the thickness of the third short-circuit prevention portion (150c) on the top of the micro LED may become excessively thick, which may not be sufficiently removed during the subsequent etching process for exposing both ends of the micro LED, and thus light emission may not occur.

[0074] In addition, if the thickness of the insulating layer between the well and the bottom electrode is too thick, the intensity of the electric field in the region between the first bottom electrode and the second bottom electrode tends to decrease, so it is desirable to have an appropriate thickness. For example, the thickness of the insulating layer between the well and the bottom electrode may be approximately 0.01 to 0.2 μm, and specifically, may be 0.1 to 0.2 μm, but is not limited thereto.

[0075] It is desirable to place one micro LED per well. In this case, since exactly one micro LED is placed per well, alignment issues such as those occurring do not occur. It is also possible to place multiple micro LEDs per well, but in this case, the arrangement direction of the micro LEDs is not precise, which may cause problems such as some micro LEDs not working. In order to place one micro LED per well, the length of the well may be approximately 1.1 to 1.5 times the length of the micro LED, and the width of the well may be approximately 1.1 to 1.8 times the width of the micro LED.

[0076] FIGS. 5A to 5E schematically illustrate each step of a method for manufacturing a micro LED light-emitting unit according to an embodiment of the present invention.

[0077] Specifically, FIG. 5a shows an example in which a bottom electrode pair is formed on a substrate, FIG. 5b shows an example in which an insulating layer including a well is formed, FIG. 5c shows an example in which a micro LED is placed within a well, FIG. 5d shows an example in which a short-circuit prevention layer is formed, and FIG. 5e shows an example in which a transparent electrode pair is formed.

[0078] A method for manufacturing a micro LED light-emitting unit according to an embodiment of the present invention first forms a plurality of bottom electrode pairs (120), each of which includes a first bottom electrode (120a) and a second bottom electrode (120b) spaced apart from each other on a substrate (110), as shown in the example illustrated in FIG. 5a.

[0079] Next, as in the example illustrated in Fig. 5b, after forming an insulating layer (130) on a substrate on which a plurality of bottom electrode pairs are formed, portions of the insulating layer corresponding to the upper portion of the region between the first bottom electrode (120a) and the second bottom electrode (120b) of the plurality of bottom electrode pairs are etched to form a plurality of wells (135). The plurality of wells (135) include a first bottom surface (135a) and a second bottom surface (135b) that extends in a step form from the edge of the first bottom surface and is located higher than the first bottom surface.

[0080] In the step of forming a plurality of wells, the size of the well (135) can be controlled so that one side wall (135c) of the well (135) vertically overlaps with the first bottom electrode (120a), and the other side wall of the well (135) vertically overlaps with the second bottom electrode (120b).

[0081] In the step of forming a plurality of wells, the spacing between a certain well and another adjacent well can be controlled to 5 μm to 10 μm. In addition, in the step of forming a plurality of wells, the depth (b) of the wells can be formed to 0.3 μm to 0.9 μm.

[0082] Next, as in the example illustrated in Fig. 5c, a plurality of micro LEDs (140) are arranged to contact the second bottom surface (135b) of each well. The micro LEDs (140) may not contact the first bottom surface (135a) of the well.

[0083] Next, as in the example illustrated in FIG. 5d, a short-prevention layer (150) is formed to prevent a short between the P-type semiconductor layer and the N-type semiconductor layer of the micro LED (140). Specifically, in the well where the micro LED (140) is placed, a first short-prevention portion (150a) is formed between the lower surface of the micro LED and the first bottom surface, a second short-prevention portion (150b) is formed between the micro LED and the side wall of the well, and a third short-prevention portion (150c) is formed on the upper surface of the micro LED. Specifically, after the short-prevention layer (150) is formed over the entire upper surface of the insulating layer, including the inside of the well where the micro LED (140) is placed, both edges of the upper surface of the micro LED are exposed through a patterning process. Preferably, the step of forming the short-prevention layer exposes both edges of the upper surface of the micro LED and the side surface of the micro LED in the patterning process in order to increase the contact area between the micro LED (140) and the subsequent transparent electrode pair (160).

[0084] The short-circuit prevention layer (150) can be formed by spin coating.

[0085] Both the insulating layer and the short-circuit prevention layer can be formed of a material containing SiO2. To this end, the short-circuit prevention layer (150) can be formed by a process of spin-coating a solution containing a silicate compound, an organic solvent, and distilled water, followed by heat treatment. For example, the solution may contain an insulator, a silicate polymer, an organic solvent, and distilled water. Specifically, the solution may contain 1 to 10 wt% of a silicate polymer, 50 to 85 wt% of an organic solvent, and the remainder distilled water. The organic solvent may contain 30 to 50 wt% of isopropyl alcohol, 10 to 30 wt% of acetone, and 10 to 30 wt% of reagent alcohol, based on the total solution.

[0086] As an example of a spin coating process for a SiO2 short-circuit prevention layer, a substrate having micro LEDs is mounted on a vacuum chuck, and then a solution containing a small amount of SiO2 precursor is dispensed to the center of the substrate, and the substrate is rotated at a predetermined rpm speed according to the desired thin film thickness. The centrifugal force resulting from the rotation causes the solution to spread evenly over the entire surface of the substrate, rapidly evaporating the solvent, and forming a thin thin film. After coating the solution, a stepwise heat treatment is preferably performed. In the case of a stepwise heat treatment, the solvent is slowly evaporated to reduce thermal shock and the flatness of the SiO2 short-circuit prevention layer can be secured.

[0087] Next, as in the example illustrated in FIG. 5e, a plurality of transparent electrode pairs (160) are formed, each including a first transparent electrode (160a) electrically connected to one edge exposed to the upper side of the micro LED, and a second transparent electrode (160b) electrically connected to the other edge exposed to the upper side of the micro LED.

[0088] The transparent electrode pair (160) can be deposited on the etched structure, and preferably can be deposited so as to cover both the insulating layer (130), the short-circuit prevention layer (150), and the micro LED (140).

[0089] The transparent electrode pair (160) can be separated into a first transparent electrode (160a) and a second transparent electrode (160b), and can include a transparent conductive oxide (TCO) material such as ITO (Indium Tin Oxide), FTO (Fluorine-doped Tin Oxide), IZO (Indium Zinc Oxide), ZnO (Zinc Oxide), etc.

[0090] The thickness of the transparent electrode pair (160) may be 100 to 200 nm, and preferably 125 to 160 nm. By satisfying the thickness of the transparent electrode pair of 100 to 200 nm, there is an effect of lowering the resistance related to the applied current.

[0091] Example

[0092] Table 1 shows the luminescence effectiveness according to well depth under all other process conditions being the same. The well depth was defined as the length from the second bottom surface of the well to the top height of the well, as shown in Fig. 3.

[0093] Whether or not the micro LED emits light is indicated by ○ if the micro LED emits light when at least 5 V is applied to the transparent electrode, and × if the micro LED does not emit light or has excessively low brightness.

[0094] [Table 1]

[0095]

[0096] Referring to Table 1, in the case of Examples 1 and 2 where the well depth was 0.9 μm or less as specified in the present invention, the micro LED emitted light properly. However, in the case of Comparative Examples 1 and 2 where this was not satisfied, the micro LED did not emitted light properly. This may mean that if the well depth is too deep beyond the range specified in the present invention, the thickness of the short-circuit prevention layer may be too thick, which may easily cause etching failures in the etching process of the short-circuit prevention portion on the top of the micro LED for exposing the micro LED.

[0097] Table 2 shows whether voids occur after spin-coating a SiO2 short-circuit prevention layer according to the well spacing under all other process conditions being the same.

[0098] The occurrence of voids was determined by microscopic observation. If no voids occurred, they were marked with ×, and if voids occurred, they were marked with ○.

[0099] [Table 2]

[0100]

[0101] Referring to Table 2, it can be seen that the well-to-well spacing shows a large change within 5 μm or so. In Examples 3, 4, and 5, where the well-to-well spacing is 5 μm or more as specified in the present invention, no voids occurred in the SiO2 short-circuit prevention layer. However, in Comparative Example 3, where the well-to-well spacing was 4.5 μm, the micro LED did not emit light properly.

[0102] In this way, according to the micro LED light-emitting unit of the present invention, by forming a short-circuit prevention layer by spin coating, the alignment position of the micro LED can be maintained even if the groove size of the insulating layer is large, and the occurrence of defects and failures in the LED element can be prevented, resulting in an excellent yield. In particular, in the case of the present invention, by controlling the depth of the well and the spacing between wells, the presence of voids between the insulating layer and the micro LED can be suppressed, thereby contributing to improved light-emitting efficiency and operating reliability.

[0103] Although the present invention has been described with reference to the drawings exemplified above, it is to be understood that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications may be made by those skilled in the art within the scope of the technical idea of ​​the present invention. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

Claims

1. Substrate; A plurality of bottom electrode pairs, each pair including a first bottom electrode and a second bottom electrode spaced apart from each other on the substrate; An insulating layer covering a substrate on which the plurality of bottom electrode pairs are formed; wherein a well is formed in the insulating layer at each upper portion of a region between the first bottom electrode and the second bottom electrode of the plurality of bottom electrode pairs, and each well includes a first bottom surface and a second bottom surface at an edge of the first bottom surface and located higher than the first bottom surface, wherein one side wall of the well vertically overlaps with the first bottom electrode, and the other side wall of the well vertically overlaps with the second bottom electrode; A plurality of micro LEDs arranged to contact the second bottom surface of each well; In the well where the micro LED is placed, a short-circuit prevention layer formed on the upper surface of the micro LED except for the lower surface of the micro LED and the first bottom surface, between the micro LED and the side wall of the well, and both edges of the upper surface of the micro LED; and A micro LED light emitting unit comprising a plurality of transparent electrode pairs, each pair including a first transparent electrode electrically connected to one upper exposed edge of the micro LED and a second transparent electrode electrically connected to the other upper exposed edge of the micro LED.

2. In paragraph 1, A micro LED light-emitting unit, wherein both the insulating layer and the short-circuit prevention layer are formed of a material containing SiO2.

3. In paragraph 1, A micro LED light emitting unit, wherein the first transparent electrode of the plurality of transparent electrode pairs extends to contact one side of the micro LED, and the second transparent electrode of the plurality of transparent electrode pairs extends to contact the other side of the micro LED.

4. In paragraph 1, A micro LED light emitting unit having a height from the top of the bottom electrode pair to the top of the well of 0.3 μm to 0.9 μm.

5. In paragraph 1, A micro LED light emitting unit, wherein the spacing between a well and an adjacent well is 5 μm to 10 μm.

6. In paragraph 1, A micro LED light-emitting unit in which one micro LED is placed in one well.

7. A step of forming a plurality of bottom electrode pairs, each pair including a first bottom electrode and a second bottom electrode spaced apart from each other on a substrate; A step of forming an insulating layer on a substrate on which the plurality of bottom electrode pairs are formed; A step of etching portions of an insulating layer corresponding to the upper portion of a region between the first bottom electrode and the second bottom electrode of the plurality of bottom electrode pairs to form a plurality of wells including a first bottom surface and a second bottom surface at a higher position than the first bottom surface at an edge of the first bottom surface, wherein one side wall of the well vertically overlaps with the first bottom electrode and the other side wall of the well vertically overlaps with the second bottom electrode; A step of arranging a plurality of micro LEDs so as to contact the second bottom surface of each well; In a well in which the micro LED is placed, a step of forming a short-circuit prevention layer formed on the upper surface of the micro LED, excluding both edges of the upper surface of the micro LED, between the lower surface of the micro LED and the first bottom surface, between the micro LED and the side wall of the well, and between the micro LED and the side wall of the well; and A step of forming a plurality of transparent electrode pairs, each pair including a first transparent electrode electrically connected to one edge exposed to the upper side of the micro LED and a second transparent electrode electrically connected to the other edge exposed to the upper side of the micro LED; A method for manufacturing a micro LED light-emitting unit, wherein the above short-circuit prevention layer is formed by a method including spin coating.

8. In paragraph 7, A method for manufacturing a micro LED light-emitting unit, wherein both the insulating layer and the short-circuit prevention layer are formed of a material containing SiO2.

9. In paragraph 8, A method for manufacturing a micro LED light-emitting unit, wherein the above short-circuit prevention layer is formed by a process of spin-coating a solution containing a silicate compound, an organic solvent, and distilled water, and then heat-treating the solution.

10. In paragraph 7, The step of forming the above short-circuit prevention layer is: A step of performing spin coating over the entire surface including the inside of the well in which the micro LED is placed, A method for manufacturing a micro LED light-emitting unit, comprising a step of exposing both edges of the upper surface of the micro LED and the side surface of the micro LED through a patterning process.

11. In paragraph 7, A method for manufacturing a micro LED light-emitting unit, wherein, in the step of forming the plurality of wells, the height from the top of the bottom electrode pair to the top of the well is controlled to 0.3 μm to 0.9 μm.

12. In paragraph 7, A method for manufacturing a micro LED light-emitting unit, wherein, in the step of forming the plurality of wells, the interval between a well and another well adjacent thereto is controlled to 5 μm to 10 μm.

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