Methods for separating multiple LED structures from a wafer

Abstract

The present invention relates to a method for separating multiple LED structures from a wafer, which is not limited by the presence of a sacrificial layer within the wafer, and does not require pre-designing the thickness of the semiconductor layer during wafer manufacturing. Instead, it allows for easy and non-destructive separation of LED structures with target size, thickness, and shape from a commercially available wafer.

Description

TECHNICAL FIELD

[0001] The present application relates to a method of separating a plurality of LED structures from a wafer. BACKGROUND

[0002] Mini-LEDs and nano-LEDs can achieve excellent color and high efficiency, and are environmentally friendly materials, and thus are being used as core materials for displays. In line with this market situation, research is recently being conducted for developing new nano-LED structures or developing LEDs through new manufacturing processes.

[0003] It is well known that individual LED elements, which were independent in the past, can be manufactured through a top-down method and a bottom-up method, but some people prefer to be manufactured through a bottom-up method based on a chemical growth method.

[0004] However, it is not easy to manufacture hundreds of millions of ultra-small independent LED elements of a nanoscale size through a bottom-up method, and even if manufactured, there is a problem in that it is difficult to have uniform sizes and characteristics, respectively.

[0005] On the contrary, in the case of a top-down method, when a wafer is etched to a target size and number, and then the LED structure remaining after the wafer is separated from the wafer etched from the wafer, thousands to hundreds of millions of independent LED elements having uniform characteristics can be manufactured.

[0006] In the case of a conventional top-down method, a method of peeling off a substrate is being used as a method for separating the LED structure remaining after being etched in a vertical direction, and in the case of this method, the wafer needs to be etched in a vertical direction until the substrate is reached, and thus the height of the LED structure is necessarily the same as the overall height of the remaining semiconductor layer except for the substrate in the wafer, and thus there is a problem in that the height of the LED element cannot be arbitrarily adjusted, and the height of each LED element is already determined in the wafer that has been manufactured.

[0007] To address this issue, a method was introduced to separate the LED structure from the semiconductor layer by applying ultrasonic waves to a vertically etched LED structure. However, this method has limitations, namely, it requires restrictions on the aspect ratio and the diameter of the bottom surface. Specifically, the bottom surface diameter must be less than 500 nm and the height must be at least five times the bottom surface diameter. Therefore, when the target size or aspect ratio of the LED element exceeds this range, this method may fail to separate the LED structure. Furthermore, the applied ultrasonic waves do not affect the lower end of the target LED structure and the interface between the adjacent semiconductor layers. Instead, the middle portion of the LED structure, exceeding the target position, is frequently separated from the wafer, resulting in difficulties in achieving uniform shape, size, and quality of the separated LED structure.

[0008] In addition, another method has been introduced, which involves introducing a sacrificial layer into the LED wafer and separating the LED structure by removing the sacrificial layer. However, in this case, the wafer itself needs to have a sacrificial layer, which leads to problems such as limiting the types of wafers that can be used, increasing costs due to the addition of a sacrificial layer, and chemical damage to the LED structure caused by the etching solution used when removing the sacrificial layer.

[0009] Therefore, there is an urgent need to develop a method that can easily and non-destructively separate LED structures from wafers without limiting the type of wafer, the size, or the shape of the LED structure to be realized. Summary of the Invention

[0010] (The problem to be solved)

[0011] The present invention is proposed to solve the problems described above, and aims to provide a method that allows for the easy and non-destructive separation of LED structures of a target size and shape from a commercially available wafer, without the need to pre-design the presence of a sacrificial layer or specify the thickness of the semiconductor layers within the wafer during wafer manufacturing.

[0012] Another object of the present invention is to provide a method for separating an LED structure from a wafer, preventing poor separation at points other than the target point during the separation of the LED structure from the wafer.

[0013] (Solutions)

[0014] To address the aforementioned issues, the present invention provides a method for separating LED structures. This method involves separating multiple LED structures from an LED wafer having multiple LED structures formed thereon. The multiple LED structures include a second portion of a doped n-type III nitride semiconductor layer connected to a first portion of that layer. The method for separating the LED structures includes: step (1) forming a protective film to surround the exposed surfaces of each of the multiple LED structures, exposing the upper surfaces of the first portions between adjacent LED structures to the outside; step (2) immersing the LED wafer in an electrolyte, then electrically connecting it to any one terminal of a power source, and connecting the remaining terminal of the power source to an electrode immersed in the electrolyte to apply power, thereby forming multiple pores in the first portion; and step (3) applying ultrasonic waves to the LED wafer to separate the multiple LED structures from the first portion having the multiple pores.

[0015] According to one embodiment of the present invention, the plurality of LED structures may further include a photoactive layer and a p-type III nitride semiconductor layer stacked on a second portion of a doped n-type III nitride semiconductor layer.

[0016] Alternatively, an LED chip with multiple LED structures can be formed by the following method, which may include: step a), preparing an LED chip, wherein the LED chip is a layer on a substrate comprising a doped n-type III nitride semiconductor layer, a photoactive layer and a p-type III nitride semiconductor layer; step b), patterning the upper part of the LED chip to have a target shape and size in a plane perpendicular to the direction of the stacked layers in a single LED structure, and then etching vertically to at least a portion of the thickness of the doped n-type III nitride semiconductor layer to form multiple LED structures.

[0017] In addition, the protective film may have the function of preventing damage to the LED structure caused by performing step (2).

[0018] In addition, the protective film in step (1) can be a temporary protective film to prevent damage to the LED structure caused by performing step (2). The method for separating multiple LED structures from the wafer may also include a step between step (2) and step (3) of forming a surface protective film surrounding the sides of the LED structure after removing the temporary protective film.

[0019] Additionally, the area of ​​the bottom surface of the LED structure connected to the first part can be 25 μm. 2 the following.

[0020] In addition, the thickness of the protective film can be 5nm to 100nm.

[0021] In addition, the protective film may include one or more of the following: 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).

[0022] Alternatively, step (2) can be performed by applying a voltage of 3V or higher for 1 minute to 24 hours.

[0023] In addition, the average pore size of the plurality of pores in step (2) is less than 100 nm.

[0024] In addition, the electrolyte 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, chloric acid, bromic acid, nitrous acid, and nitric acid.

[0025] In addition, step (3) involves immersing the LED chip in a foaming solution, then applying ultrasound to the foaming solution to generate bubbles. The energy generated when the bubbles burst in the pores collapses the pores, allowing multiple LED structures to be separated.

[0026] In addition, in order to grow and collapse bubbles to become local hot spots that generate high pressure and high temperature when the bubbles collapse, the ultrasonic frequency applied to the foaming solution can be 10KHz to 2MHz.

[0027] In addition, the solution used to form the bubbles can be a solution with low vapor pressure and low environmental impact.

[0028] Additionally, step (1) may include the following steps: forming a protective film on the LED wafer to form a protective film surrounding each side of a plurality of LED structures; and removing the protective film formed on the upper surface of a first portion between adjacent LED structures to expose the upper surface of the first portion between adjacent LED structures.

[0029] In addition, the following steps may be included between steps (2) and (3): removing the protective film formed on the upper part of each LED structure; and forming a first electrode on the upper part of the LED structure.

[0030] In addition, the present invention provides an LED structure assembly manufactured according to the present invention.

[0031] The following defines the terms used in this invention.

[0032] 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.”

[0033] (The effect of the invention)

[0034] The method for separating multiple LED structures from a wafer according to the present invention does not require pre-designing the presence of a sacrificial layer or the thickness of the semiconductor layer within the wafer during wafer manufacturing. Instead, it allows for easy and non-destructive separation of LED structures with target size, thickness, and shape from commercially available wafers. Furthermore, it prevents poor separation at points other than the target point during LED structure separation, resulting in uniform size among the multiple LED structures. This allows for the creation of LED structure assemblies exhibiting more uniform characteristics and makes it widely applicable as a material for displays and various light sources.

[0035] This invention was developed with the support of the following national research and development programs, the details of which are as follows.

[0036] [Project Number] 1711105790

[0037] [Project Number] 2016R1A5A1012966

[0038] [Department Name] Ministry of Science, Technology and Information

[0039] [Name of Project Management (Specialty) Institution] Korea National Research Foundation

[0040] [Research Project Name] Engineering Field (S / ERC)

[0041] [Research Project Title] Circadian Rhythms Using Hybrid Devices: An ICT Research Center

[0042] [Name of the Institution Implementing the Project] Kookmin University Industry-Academia Collaboration Group

[0043] [Research Period] 2021-01-01~2021-12-31

[0044] [Project Number] 1415174040

[0045] [Project Number] 20016290

[0046] [Department Name] Trade, Industry and Resources Department

[0047] [Name of the Project Management (Specialty) Organization] Korea Institute for Industrial Technology Evaluation and Management

[0048] [Research Project Name] Electronic Components Industry Technology Development - Ultra-Large Micro-LED Modular Display

[0049] [Research Topic Title] Development of Submicron Blue Light Source Technology for Modular Displays

[0050] [Name of the Institution Implementing the Project] Kookmin University Industry-Academia Collaboration Foundation

[0051] [Research Period] April 1, 2021 – December 31, 2024 Attached Figure Description

[0052] Figure 1 This is a schematic diagram of a process for separating multiple nanostructures from a wafer according to an embodiment of the present invention.

[0053] Figure 2 This is a schematic diagram illustrating a method for forming a plurality of pores in a doped n-type group III nitride semiconductor layer, performed in one embodiment of the present invention.

[0054] Figure 3 A schematic diagram of the LED structure separation method as an embodiment of the present invention is a schematic diagram of the overall process for manufacturing multiple LED structures separated from a single LED chip.

[0055] Figure 4 This is a schematic diagram of the manufacturing process of the resin layer included in an embodiment of the present invention.

[0056] Figures 5 to 7 This is a perspective view of various shapes of LED structures separated by an embodiment of the present invention.

[0057] Figures 8 to 11 These are SEM images of a specific step in the LED structure separation process of Example 1.

[0058] Figures 12 to 14 These are SEM images of a specific step in the LED structure separation process of Example 2. Detailed Implementation

[0059] 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.

[0060] An embodiment of the present invention provides a method for separating multiple LED structures from a wafer. The method is a method for separating multiple LED structures from an LED wafer on which multiple LED structures are formed, wherein the multiple LED structures include a second portion of a doped n-type III nitride semiconductor layer connected to the first portion on a first portion of the doped n-type III nitride semiconductor layer. The method for separating multiple LED structures from the wafer includes: step (1), forming a protective film to surround the exposed surfaces of each of the multiple LED structures, and exposing the upper surfaces of the first portions between adjacent LED structures to the outside; step (2), immersing the LED wafer in an electrolyte, then electrically connecting it to any one terminal of a power source, and connecting the remaining terminal of the power source to the electrode immersed in the electrolyte and then applying a power source to form multiple pores in the first portion; and step (3), applying ultrasonic waves to the LED wafer to separate the multiple LED structures from the first portion on which multiple pores are formed.

[0061] Reference Figure 1 To illustrate, the LED wafer 100h1, which is the object of step (1) of the present invention, can be an LED wafer in the following state: a plurality of LED structures, including a second portion b of a doped n-type III nitride semiconductor layer 10 at the lower end, are formed on a first portion a of the doped n-type III nitride semiconductor layer 10, and the first portion and the second portion b are connected. This is an LED wafer in the state before the plurality of LED structures are separated into individual independent elements after a typical LED wafer has been etched in a vertical direction. Furthermore, it is preferable that the area of ​​the bottom surface of the LED structure connected to the first portion is 25 μm. 2 Below, if the area of ​​the bottom surface exceeds 25μm 2 If so, it may be difficult to separate the LED through step (2) described later.

[0062] The lower portion of the plurality of LED structures includes a doped n-type III nitride semiconductor layer 10, while the upper portion may have various semiconductor layers and electrode layers typically found in LED elements. For example, the plurality of LED structures may further include: a photoactive layer 20, a p-type III nitride semiconductor layer 30, and a first electrode layer 40 stacked on a second portion b of the doped n-type III nitride semiconductor layer 10. Additionally, the doped n-type III nitride semiconductor layer 10 may also include a substrate 1 typically found in wafers.

[0063] The doped n-type III nitride semiconductor layer 10 may comprise a III-V semiconductor material called a III nitride, particularly a binary, ternary, or quaternary alloy of gallium, aluminum, indium, and nitrogen. For example, the n-type III nitride semiconductor layer 10 may be an In-type semiconductor material. x Al y Ga1-x-y Semiconductor materials with a composition of N (0≤x≤1, 0≤y≤1, 0≤x+y≤1) can be selected from one or more of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc. Furthermore, the n-type III nitride semiconductor layer must be a semiconductor layer doped with a first conductive dopant (e.g., Si, Ge, Sn), because the first conductive dopant can form pores in the n-type III nitride semiconductor layer 10 through step (2) described later. On the other hand, the thickness of the n-type III nitride semiconductor layer 10 doped within the wafer can be 0.5μm to 4μm, and the thickness of the second portion b of the n-type III nitride semiconductor layer 10 doped within each LED structure can be 0.5μm to 4μm.

[0064] Furthermore, the photoactive layer 20 can be a photoactive layer present in a typical LED, formed as a single or multiple quantum well structure. When the photoactive layer 20 is included in a typical LED element used in lighting, displays, etc., its use is unrestricted. 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 doped with the conductive dopant 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 semiconductor layers located above and below the photoactive layer to the photoactive layer recombine in the photoactive layer, thus emitting light. According to a preferred embodiment of the present invention, the thickness of the photoactive layer 20 can be 30 nm to 300 nm, but is not limited thereto.

[0065] Furthermore, the p-type III nitride semiconductor layer 30 stacked on the photoactive layer 20 can be used without limitation in the case of a typical p-type III nitride semiconductor layer in an LED. For example, it can be a layer with In... x Al y Ga 1-x- y Semiconductor materials with a composition of N (0≤x≤1, 0≤y≤1, 0≤x+y≤1), such as InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc., can be selected from any one or more of them. Additionally, a second conductive dopant (e.g., Mg) can be doped. According to a preferred embodiment of the invention, the thickness of the p-type III nitride semiconductor layer 30 can be 0.01 μm to 0.30 μm, but is not limited thereto.

[0066] Furthermore, the first electrode layer 40 formed on the p-type III nitride semiconductor layer 30 can be used without limitation if it is an electrode layer commonly used in LED devices. The first electrode layer 40 can be made of materials such as Cr, Ti, Al, Au, Ni, ITO, and oxides or alloys thereof, either individually or in mixtures, or by forming layers of these materials separately and then stacking the layers thus formed. Preferably, a transparent material can be used to minimize light loss; as an example, it can be made of ITO or... Figure 3 The first electrode composite layer 42 shown is formed by stacking a first electrode layer 40 as an ITO layer and a metal electrode layer 41 as an Au layer. Furthermore, the thickness of the first electrode layer 40 or the first electrode composite layer 42 can be independently 50 nm to 500 nm, but is not limited to this.

[0067] In addition, the aforementioned n-type III nitride semiconductor layer 10, photoactive layer 20, and p-type III nitride semiconductor layer 30 can be included as the minimum constituent elements of an ultrathin film LED structure. Other phosphor layers, quantum dot layers, active layers, semiconductor layers, hole blocking layers, and / or electrode layers may also be included above or below each layer.

[0068] According to an embodiment of the present invention, such as Figure 3 As shown in (a) to (h), an LED chip 100h1 having multiple LED structures can be formed by the following method, which includes: step a), including a substrate 1, a doped n-type group III nitride semiconductor layer 10, a photoactive layer 20 and a p-type group III nitride semiconductor layer 30, preparing to stack these layers on the substrate 1 to form an LED chip 100a( Figure 3 (a) and (b)); patterning the upper part of the LED chip so that a plane perpendicular to the direction of the stacked layers on a single LED structure has a target shape and size. Figure 3 (b) and (c) are then etched vertically to at least a portion of the thickness of the doped n-type III nitride semiconductor layer to form multiple LED structures. Figure 3 (d)~(g)).

[0069] The LED wafer 100a prepared in step a) is commercially available and can be used without restriction as long as it is commercially available. Furthermore, to achieve the target thickness, the remaining LED structure after etching the n-type III nitride semiconductor layer can be separated on the LED wafer using the separation method of this invention. Therefore, there is no limitation on the thickness of the n-type III nitride semiconductor layer 10 within the LED wafer, and the presence of a separate sacrificial layer can be disregarded when selecting the wafer. Additionally, each layer within the LED wafer 100a can have a c-plane crystal structure. Furthermore, the LED wafer 100a can undergo a cleaning process, which can appropriately employ conventional wafer cleaning solutions and processes; therefore, this invention does not impose any particular limitations on this. For example, the cleaning solution can be isopropanol, acetone, and hydrochloric acid, but is not limited to these.

[0070] Then, before performing step b), 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.

[0071] Subsequently, as in step b), the upper part of the LED chip can be patterned so that a plane perpendicular to the direction of the stacked layers in a single LED structure has the desired shape and size. Figure 3 (b) to (f)). 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 chips. The pattern of the pattern layer may be formed by applying conventional photolithography or nanoimprinting.

[0072] For example, such as Figure 3 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 through the following process: 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 3(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 3 (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 3 (e) and (f)). In this case, the second mask layer 3 can be a metal layer such as aluminum or nickel. For example, the first mask layer 2 can be formed with silicon dioxide. The etching of these layers can be performed by ICP (inductively coupled plasma) and RIE, respectively. On the other hand, the resin pattern layer 4' can also be removed when etching the first mask layer 2 (see 100f).

[0073] On the other hand, such as Figure 4 As 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 4 (a) is then processed in mold 6b to form resin layer 4. Figure 4 (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 on which the first mask layer 2 and the second mask layer 3 are formed. Then, the mold 6b is removed, thereby realizing the wafer stack 100c on which the resin layer 4 is formed.

[0074] 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.

[0075] After that, as Figure 3 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 group nitride 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. In this etching process, Al constituting the mask pattern layer, i.e., the second mask layer 3, is removed, followed by the removal of silicon dioxide, i.e., the first mask layer 2, present on the first electrode layer 40 constituting each LED structure within the LED wafer 100g. This allows the manufacture of an LED wafer 100h with multiple LED structures formed as the target of step (1) of this invention.

[0076] Subsequently, as step (1) of the present invention, a protective film 80a is formed on the prepared LED wafer 100h having multiple LED structures, such that the protective film 80a surrounds the exposed surfaces of each of the multiple LED structures with a predetermined thickness, and exposes the upper surface S1 of the first portion a between adjacent LED structures to the outside. Figure 1 (b)). The protective film 80a is used to prevent damage to the LED structure due to the execution of step (2) described later, and at the same time, it also performs the function of protecting the side surface of the individual separated LED structure from external stimuli while it remains on the side of the LED structure separated from the LED wafer.

[0077] Specifically, step (1) 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 1-1); and 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 (step 1-2).

[0078] Step 1-1 is the step of depositing a protective film material onto an LED wafer 100h on which multiple LED structures are formed. At this time, the protective film material can be a known material that is not chemically corroded by the electrolyte in step (2) described later. For example, it may 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). Furthermore, the thickness of the protective film 80a formed by depositing the protective film material can be from 5 nm 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 corroded by the electrolyte in step (2) described later; when the thickness of the protective film 80a is greater than 100 nm, there may be problems with increased manufacturing costs and connections between LED structures.

[0079] Next, steps 1-2 involve 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 to the outside. Because step 1-1 also deposits a protective film material on the upper surface S1 of the first portion a between adjacent LED structures, the electrolyte cannot contact the n-type III nitride semiconductor layer 10, thus preventing the formation of the target pores in the first portion a. Therefore, the step of removing the protective film material covering the upper surface S1 of the first portion a to expose it to the outside is performed. The removal of the protective film material can be carried out using known dry or wet etching methods.

[0080] On the other hand, according to one embodiment of the present invention, the protective film formed in step (1) is a temporary protective film for preventing damage to the LED structure caused by performing step (2). Between step (2) and step (3), a step may be included to remove the temporary protective film and then form a surface protective film surrounding the sides of the LED structure. That is, the protective film 80a described above performs the function of remaining after step (2) to prevent damage to the LED structure in step (2) and to prevent damage to the surface of the LED structure after step (2). Conversely, in some embodiments, the protective film in step (1) is only used as a temporary protective film for preventing damage to the LED structure in step (2), and is removed before performing step (3). Afterward, a surface protective film can be formed to perform the function of preventing damage to the surface of the LED structure, so that the surface protective film covers the sides of the LED structure. As described above, some embodiments have the inconvenience of forming two protective films, but the planar shape, size, and spacing between the LED structures can be considered when making the selection. In addition, when performing step (2) described later, partial erosion of the protective film may occur. When 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 performed in step (2) as appropriate.

[0081] Reference Figure 3 The manufacturing process of a portion of the embodiments described above is explained by... Figure 3 (i) to (j) a temporary protective film 5 is deposited on the LED wafer 100h, which forms multiple LED structures. Then, the temporary protective film material deposited on the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer 10 between adjacent LED structures of the LED wafer 100i on which the temporary protective film 5 is deposited is etched, thus forming a temporary protective film 5' protecting the sides and top of the multiple LED structures. Afterwards, step (2) described later is performed. Figure 3 (k)), and then the protective film 5' is removed by etching. Figure 3(l)) A protective film material, which serves as a surface protective film for protecting the surface of the LED structure, is deposited on the LED chip 100l. Afterwards, 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 3 (m)). At this time, not only the protective film material formed on the upper part of the LED structure, but also the protective film material deposited between adjacent LED structures of the LED chip 100l, that is, on the upper surface S1 of the first part a of the doped n-type III nitride semiconductor layer 10, can be removed together. Accordingly, in step (3) 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.

[0082] 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.

[0083] Subsequently, as step (2) of the present invention, the LED chip is immersed in the electrolyte and then electrically connected to any one terminal of the power supply, and the remaining terminal of the power supply is electrically connected to the electrode immersed in the electrolyte and then a power supply is applied to form a plurality of pores in the first part.

[0084] Specifically, such as Figure 1 and Figure 2 As shown, 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 75 immersed in an electrolyte 74 to apply power. This allows the fabrication of an LED chip 100h3 in which a plurality of pores P are formed in the first portion a of the doped n-type III nitride semiconductor layer. The pores P are formed from the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer, which is in direct contact with the electrolyte, in the thickness direction and along the side of the first portion a corresponding to the lower portion of each of the plurality of LED structures.

[0085] The electrolyte used in step (2) is preferably an oxyacid, specifically one or more 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 can be used, which has the advantage of forming pores without damaging the LED structure. Additionally, the electrode can be made of platinum (Pt), carbon (C), nickel (Ni), or gold (Au), for example, a platinum electrode. Furthermore, step (2) can 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 (3). More preferably, the voltage can be 10V or higher, and even more preferably, 30V or lower can be applied. If a voltage less than 3V is applied, even if the power supply time is increased, pores cannot be successfully formed on the side of the first portion a corresponding to the lower part of each LED structure. Therefore, it is difficult to separate them in step (3). Or, even if multiple LED structures are separated, the shapes of the separated end faces are different, so multiple LED structures may not exhibit uniform characteristics. In addition, when a voltage exceeding 15V is applied, pores can be formed to the lower end of the LED structure connected to the first portion a of the doped n-type III nitride semiconductor layer, i.e., the second portion b, which may cause a decrease in light emission characteristics. Furthermore, in step (3) described later, it is preferable to separate the LED structure at the boundary point between the first portion a and the second portion b of the doped n-type III nitride semiconductor layer. However, because pores formed on the side of the second portion b may extend beyond the boundary point, separation may occur at a certain point on the side of the second portion b. Therefore, there is a risk that an LED structure with an n-type semiconductor layer thickness smaller 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 extended, there is a risk that pores will form in the second part b outside the target part. Conversely, if the application time is short, the pores will not form smoothly, so it may be difficult to separate the LED structure.

[0086] After step (2) and before step (3) 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 formed on the side surface of the LED structure remains, which can perform the function of protecting the side surface of the LED structure from the outside.

[0087] In addition, the average pore size of the plurality of pores in step (2) is less than 100 nm, so the LED structure can be more easily separated from the wafer through step (3).

[0088] Additionally, after step (2) and before step (3) described later, the step of forming other layers on the first electrode layer 40 of the LED structure may be performed. For example, the other layers may be a metal electrode layer 41 (see reference). Figure 3 (n)).

[0089] Subsequently, as step (3) of the present invention, 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.

[0090] 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 pores using the physical 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 into the second part b of the LED structure, which may lead to a side effect of reducing the quality of the LED structure.

[0091] Accordingly, according to an embodiment of the present invention, step (3) can be performed using a sonochemistry method. Specifically, the LED wafer 100h4 is immersed in a foaming solution 76 (or solvent), and then ultrasound is applied to the foaming solution 76 (or solvent). 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 in both 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 only performs the function of generating bubbles in the foaming solution (or solvent), growing bubbles, moving the generated bubbles and penetrating into the pores P of the first part a. Afterwards, multiple LED structures can be easily separated from the LED chip by the pore collapse mechanism generated by the external force generated when the unstable bubbles with high temperature and high pressure that subsequently penetrate into the pores P burst.

[0092] For the foaming solution 76 (or solvent), any solution (or solvent) that generates bubbles upon application of ultrasound and grows into bubbles with high pressure and high temperature can be used without limitation. Preferably, the foaming solution (or solvent) can be used with a vapor pressure of 100 mmHg (20°C) or less. As another example, it can be used with 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 achieve normal separation 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 methyl ether acetate, methylpyrrolidone, and 2-methoxyethanol. Alternatively, a solution (or solvent) with a vapor pressure of 100 mmHg at room temperature, such as 20°C, can be used. However, it should be noted that step (3) can be performed by adjusting the conditions differently, such as by adjusting the vapor pressure of the foaming solution (or solvent) to below 100 mmHg (for example, low temperature conditions). In this case, the restrictions on the types of solvents that can be used can be further relaxed; for example, solvents such as water, acetone, and alcohol can also be used.

[0093] Furthermore, the wavelength of the ultrasound applied in step (3) can be applied at a frequency that can create a region capable of inducing an ultrasonic chemical reaction, specifically a local hot spot that generates high pressure and high temperature during bubble collapse, thus promoting bubble growth and collapse. For example, this could be 10 kHz to 2 MHz, and the ultrasound application time could be 1 minute to 24 hours, thereby facilitating the separation of the LED structure from the LED chip. Even if the wavelength of the applied ultrasound is within this range, there is a risk of an increase in the number of LED structures that are not separated from the LED chip or the number of unseparated LED structures if the intensity is low or the application time is short. In addition, if the intensity of the applied ultrasound is high or the application time is long, there is a risk of damage to the LED structure.

[0094] Furthermore, the present invention can obtain LED structure assemblies 100 and 100' comprising multiple individual LED structures 101 and 102 separated from the LED chip through the above method. For example... Figures 5 to 7As shown, the implemented LED structures 103, 104, and 105 may include: doped n-type III nitride semiconductor layers 103a, 104a, and 105a; photoactive layers 103b, 104b, and 105b; p-type III nitride semiconductor layers 103c, 104c, and 105c; and a protective film (not shown) surrounding the sides of the LED structure. Additionally, the LED structures 103, 104, and 105 may be cylindrical in shape. Figure 5 ), regular hexahedron ( Figure 6 ) or a unidirectionally extending rectangular hexahedron ( Figure 7 In addition, cylindrical LED structures can be implemented from a rope shape with a height greater than its diameter to a disc shape with a diameter greater than its height.

[0095] Furthermore, regarding the size of the implemented individual LED structure, for example, in the case of a cylindrical LED structure 103, the diameter can be 0.5μm to 5μm and the height can be 0.5μm to 5μm; in the case of a regular hexahedral LED structure 104, the length of one side can be 0.5μm to 5μm; in the case of a right-angled hexahedral LED structure, the length of the long side of the top or bottom surface can be 0.5μm to 10μm, the length of the short side can be 0.5μm to 5μm, and the height can be 0.5μm to 4μm.

[0096] 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.

[0097] (Example 1)

[0098] 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 etching. 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 8 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.

[0099] Next, the LED chip with the 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 9 The SEM images show multiple pores 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, the protective film formed on the upper part of the multiple LED structures was removed by RIE, exposing the upper surface of the LED structures. Then, the LED wafer was immersed in a foaming solution, namely γ-butyrolactone, and then ultrasonically irradiated at 40 kHz for 10 minutes to generate bubbles. These bubbles collapsed into the pores formed in the doped n-type III nitride semiconductor layer, thus... Figure 10 The SEM images showed multiple LED structures. Additionally, as... Figure 11 It can be confirmed that there are no unseparated LED structures on the chip.

[0100] (Example 2)

[0101] The procedure was carried out and performed in the same manner as in Example 1, except that an SOG resin layer with a modified pattern was used to form a right-angled quadrilateral shape at the top and bottom of the LED structure formed on the LED chip, and the material of the second mask layer was changed to an 80.6 nm thick nickel layer. Then, as in Example 1, the second mask layer was etched along the pattern using ICP, and the first mask layer was etched using RIE. Next, the first electrode layer, the p-type III nitride semiconductor layer, and the photoactive layer were etched using ICP, followed by etching the doped n-type III nitride semiconductor layer to a thickness of 0.8 μm. The mask pattern layer was then removed by KOH wet etching, as described above. Figure 12 SEM images showed an LED wafer fabricated with multiple LED structures (4 μm long side, 838 nm short side, and 744 nm height) forming a rectangular hexahedral shape. Next, as a protective film, Al₂O₃ was deposited on the LED wafer with a thickness of approximately 60 nm, aligned with the sides of the LED structures. The surface protective film formed on the upper part 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 were removed by RIE, exposing the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer. The LED wafer was then immersed in a 0.3 M oxalic acid aqueous solution (electrolyte) and connected to the anode terminal of a power supply. A platinum electrode immersed in the electrolyte was connected to the cathode terminal, and a voltage of 15 V was applied for five minutes. Figure 13 SEM images show multiple pores formed along the depth direction on the surface of the first portion a of the doped n-type III nitride semiconductor layer. Subsequently, the protective film formed on the upper part of the multiple LED structures was removed by ICP, exposing the upper surface of the LED structures. Then, the LED wafer was immersed in 100% γ-butyrolactone as a foaming solution, followed by ultrasonic irradiation at 160W and 60Hz for 10 minutes to generate bubbles. These bubbles collapsed into the pores formed in the doped n-type III nitride semiconductor layer, thus... Figure 14 The SEM images showed multiple LED structures in the shape of a right-angled hexahedron.

[0102] (Example 3)

[0103] It was carried out in the same manner as in Example 1, except that the foaming solution was changed to acetone to separate the LED structure from the wafer.

[0104] (Example 4)

[0105] It was carried out in the same manner as in Example 1, except that the foaming solvent was changed to water to separate the LED structure from the wafer.

[0106] (Experimental Example 1)

[0107] The yield of LED structures separated from the LED wafer was measured using the separation methods of Examples 1, 3, and 4. The yield was calculated as a percentage by comparing the number of LED structures present on the LED wafer before separation with the number of LED structures remaining on the LED wafer after separation using SEM images. The results are shown in Table 1 below.

[0108] (Table 1)

[0109] Example 1 Example 3 Example 4 Blowing solvent γ-butyrolactone Acetone Water Blowing solvent vapour pressure 1.5 mm Hg (20 °C) 184 mm Hg (20 °C) 17.5 mm Hg LED structure separation yield (%) 100％ 15％ 50％

[0110] Table 1 confirms that, in the case of acetone and water, the LED structure could not be completely separated after 10 minutes of ultrasonication. However, in contrast, the separation yield was excellent in the case of Example 1. This indicates that solvents that form excellent bubbles through ultrasonic chemistry can be separated more easily.

[0111] 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. A method for separating a plurality of LED structures from a wafer, which is a method for separating a plurality of LED structures from an LED wafer on which the plurality of LED structures are formed, the plurality of LED structures including a second portion of a doped n-type III-nitride semiconductor layer successively to a first portion of the doped n-type III-nitride semiconductor layer, the method for separating a plurality of LED structures from a wafer characterized by comprising: Step (1) of forming a protective film to surround an exposed surface of each of the plurality of LED structures and expose an upper surface of the first portion between adjacent LED structures to the outside; Step (2) of immersing the LED wafer in an electrolyte, thereafter electrically connecting either terminal of a power source and connecting the remaining terminal of the power source to an electrode immersed in the electrolyte, and then applying the power source to form a plurality of pores in the first portion; and Step (3) of applying ultrasonic waves to the LED wafer to separate the plurality of LED structures from the first portion by collapsing the plurality of pores, wherein the doped n-type III-nitride semiconductor layer in the plurality of separated LED structures includes a groove formed by collapsing the plurality of pores. The plurality of LED structures each further includes a light active layer and a p-type III-nitride semiconductor layer stacked on the second portion of the doped n-type III-nitride semiconductor layer. The LED wafer on which the plurality of LED structures are formed is formed by a method comprising: Step a) of preparing an LED wafer on which layers including a doped n-type III-nitride semiconductor layer, a light active layer, and a p-type III-nitride semiconductor layer are stacked on a substrate; and Step b) of patterning an upper portion of the LED wafer to have a target shape and size in a plane perpendicular to the direction of the stacked layers in a single LED structure, and thereafter etching in a vertical direction to at least a portion of the thickness of the doped n-type III-nitride semiconductor layer to form the plurality of LED structures. The protective film has a function for preventing the LED structures from being damaged due to the execution of Step (2). The protective film of Step (1) is a temporary protective film for preventing the LED structures from being damaged due to the execution of Step (2), 2. A method of separating a plurality of LED structures from a wafer according to claim 1, wherein, The method for separating a plurality of LED structures from a wafer further includes, between Step (2) and Step (3), a step of forming a surface protective film surrounding the side surface of the LED structures after removing the temporary protective film.

3. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The thickness of the protective film is 5 nm to 100 nm. The protective film contains one or more selected from the group consisting of silicon nitride, silicon dioxide, aluminum oxide, hafnium oxide, zirconium oxide, yttrium oxide, lanthanum oxide, scandium oxide, titanium dioxide, aluminum nitride, and gallium nitride. Step (2) is performed by applying a voltage of 3 V or more for 1 minute to 24 hours.

4. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The electrolyte contains one or more oxygen-containing acids selected from the group consisting of oxalic acid, phosphoric acid, sulfurous acid, sulfuric acid, carbonic acid, acetic acid, chlorous acid, chloric acid, bromic acid, nitrous acid, and nitric acid.

5. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The average pore diameter of the plurality of pores in Step (2) is 100 nm or less. ​ 6. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The area of the LED structure bottom surface consecutive to the first portion is 25 μm 2 The following.

7. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, ​ 8. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, ​ 9. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, ​ 10. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, ​ 11. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, ​ 12. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The step (3) includes the steps of:

13. A method of separating a plurality of LED structures from a wafer according to claim 12, wherein, The step (3) includes the steps of:

14. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of:

15. The method of singulating a plurality of LED structures from a wafer of claim 1, wherein, The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of:

16. An LED structure assembly comprising: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes the steps of: The step (1) includes

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