LED Transfer Method and Method for Manufacturing a Display Device Using the Same

Abstract

To provide an LED transfer method and a manufacturing method of a display device using the same which reduce defects in a plurality of LEDs in a transfer step of transferring the plurality of LEDs to a donor substrate from a wafer.SOLUTION: An LED transfer method according to one embodiment of the present invention includes bonding a rigid substrate on which a plurality of LEDs is formed and a flexible substrate, transferring the plurality of LEDs to the flexible substrate, and detaching the rigid substrate and the flexible substrate. The detaching of the rigid substrate and the flexible substrate includes separating the rigid substrate and the flexible substrate in a state in which one surface of the rigid substrate is fixed and a portion among outermost portions of the flexible substrate is fixed by a fixing member. Accordingly, it is possible to reduce transfer defects of the plurality of LEDs by detaching the flexible substrate and the rigid substrate in a line-by-line separation method.SELECTED DRAWING: Figure 4E

Description

Technical Field

[0001] The present invention relates to a method for transferring light-emitting diodes (LEDs) and a method for manufacturing a display device using the same. More specifically, the present invention relates to a method for transferring LEDs with improved yield during the transfer of a plurality of LEDs, and a method for manufacturing a display device using the same.

Background Art

[0002] Display devices used in computer monitors, TVs, mobile phones, etc. include organic light-emitting display devices (OLEDs) that emit light by themselves, and liquid crystal display devices (LCDs) that require a separate light source. The application range of display devices is diverse, not only including computer monitors and TVs, but also personal portable devices. Research is underway on display devices that have a large display area while having a reduced volume and weight.

[0003] In recent years, display devices including light-emitting diodes (LEDs) have attracted attention as next-generation display devices. Since LEDs are made of inorganic materials rather than organic materials, they have excellent reliability and a longer lifespan compared to liquid crystal display devices and organic light-emitting display devices. In addition, LEDs not only have a fast lighting speed, but also have excellent luminous efficiency, strong impact resistance, excellent stability, and can display high-brightness images.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a method for transferring LEDs with reduced defects of a plurality of LEDs during a transfer process of transferring a plurality of LEDs from a wafer to a donor substrate, and a method for manufacturing a display device using the same.

[0005] Another problem to be solved by the present invention is to provide a method for transferring LEDs with improved alignment accuracy of a plurality of LEDs, and a method for manufacturing a display device using the same.

[0006] Another problem to be solved by the present invention is to provide a method for transferring LEDs that increases the detachment speed between a wafer and a donor substrate and reduces the process time, and a method for manufacturing a display device using the same.

[0007] Another problem to be solved by the present invention is to provide a method for transferring LEDs that minimizes the distortion of a plurality of LEDs when detaching a wafer from a donor substrate or a donor substrate from a display panel, and a method for manufacturing a display device using the same.

[0008] The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0009] The method for transferring LEDs according to an embodiment of the present invention includes a step of attaching a rigid substrate on which a plurality of LEDs are formed to a flexible substrate, a step of transferring the plurality of LEDs to the flexible substrate, and a step of detaching the rigid substrate from the flexible substrate. The step of detaching the rigid substrate from the flexible substrate includes a step of fixing one surface of the rigid substrate and separating the rigid substrate from the flexible substrate while fixing a part of the outermost portion of the flexible substrate with a fixing member. Therefore, the transfer failure of a plurality of LEDs can be reduced by detaching the flexible substrate from the rigid substrate by a wire peeling method.

[0010] The manufacturing method of a display device according to an embodiment of the present invention includes steps of attaching a wafer and a donor substrate, transferring a plurality of LEDs on the wafer to the donor substrate, detaching the wafer and the donor substrate, attaching the donor substrate on which the plurality of LEDs are arranged and a display panel, transferring the plurality of LEDs on the donor substrate to the display panel, and detaching the display panel and the donor substrate. The step of detaching the wafer and the donor substrate includes a step of fixing one surface of the wafer to a head and detaching the wafer and the donor substrate in a state where a part of the outermost contour portion of the donor substrate is fixed to a stage. Therefore, the wafer and the donor substrate can be detached in a wire peeling method by detaching the wafer and the donor substrate in a state where only a part of the outermost contour portion of the donor substrate is fixed, and the impact applied to the plurality of LEDs on the donor substrate can be minimized. Specific matters of other embodiments are included in the detailed description and the drawings.

Advantages of the Invention

[0011] In the present invention, when detaching the donor substrate from the wafer, only one side end portion of the donor substrate can be physically fixed to minimize distortion of the plurality of LEDs on the donor substrate.

[0012] In the present invention, the donor substrate and the wafer can be wire-peeled to minimize a decrease in the transfer yield of the plurality of LEDs.

[0013] In the present invention, the transfer speed of the LEDs can be improved to reduce the process time and cost and improve productivity.

[0014] The effects according to the present invention are not limited to the contents illustrated above, and more various effects are included in the present invention.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figures 4A - 4G

Figures 5A - 5B

Figures 6A - 6B

Mode for Carrying Out the Invention

[0016] The advantages, features, and the methods for achieving them of the present invention will become clear by referring to the embodiments described in detail hereinafter together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be embodied in various different shapes. Merely, these embodiments are provided so that the disclosure of the present invention becomes complete, and to fully inform those with ordinary knowledge in the technical field to which the present invention pertains of the scope of the invention. The present invention is only defined by the scope of the claims.

[0017] The shapes, areas, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, so the present invention is not limited to the illustrated matters. Throughout the specification, the same reference numerals refer to the same components. Also, when explaining the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description thereof will be omitted. When terms such as "including", "having", "being made" mentioned in the present invention are used, unless "only" is used, other parts can be added. When a component is expressed in the singular, unless otherwise explicitly stated, it includes the case of including a plurality.

[0018] When interpreting a component, it is interpreted as including an error range even without a separate explicit description.

[0019] When it comes to the description of the positional relationship, for example, when the positional relationship between two parts is described such as "above ~", "on the upper part of ~", "on the lower part of ~", "next to ~", etc., as long as "immediately" or "directly" is not used, one or more other parts may be located between the two parts.

[0020] What is referred to as "on" an element or layer by another element or layer includes both the case where there is another layer or another element immediately above the other element or intervening between them.

[0021] Also, the first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are merely used to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical concept of the present invention.

[0022] Throughout the specification, the same reference numerals refer to the same components.

[0023] The area and thickness of each configuration shown in the drawings are shown for the convenience of explanation, and the present invention is not necessarily limited to the area and thickness of the shown configuration.

[0024] The respective features of the various embodiments of the present invention can be partially or entirely combined or combined with each other, enabling various interlocks and drives technically, and each embodiment may be implemented independently of each other or may be implemented together in a related relationship.

[0025] Hereinafter, the present invention will be described with reference to the drawings.

[0026] FIG. 1 is a plan view of a display device according to an embodiment of the present invention. In FIG. 1, for the convenience of explanation, only the display panel PN and a plurality of pixels PX among the various components of the display device 100 are shown.

[0027] The display panel PN is configured to display an image and includes a display area AA and a non-display area NA.

[0028] The display panel PN includes a display area AA and a non-display area NA.

[0029] The display area AA is an area for displaying an image. In the display area AA, a plurality of pixels PX for displaying an image and a circuit unit for driving the plurality of pixels PX may be arranged. The circuit unit can include various thin film transistors, capacitors, wirings, etc. for driving the pixel PX. For example, the circuit unit can be composed of various components such as a driving thin film transistor, a switching thin film transistor, a storage capacitor, a gate wiring, and a data wiring, but is not limited thereto.

[0030] The non-display area NA is an area where an image is not displayed and is an area where various wirings, driving ICs, etc. for driving the pixels PX arranged in the display area AA are arranged. For example, various driving ICs such as a gate driver IC and a data driver IC may be arranged in the non-display area NA.

[0031] In FIG. 1, the non-display area NA is shown as surrounding the display area AA, but the non-display area NA may be an area extending from one side of the display area AA and is not limited thereto.

[0032] A plurality of pixels PX are arranged in the display area AA of the display panel PN. Each of the plurality of pixels PX can be composed of a plurality of sub-pixels. The plurality of sub-pixels are individual units that emit light, and an LED and a driving circuit are formed in each of the plurality of sub-pixels. For example, the plurality of pixels PX can include a red sub-pixel, a green sub-pixel, and a blue sub-pixel, but are not limited thereto, and the plurality of pixels PX may further include a white sub-pixel.

[0033] And the LEDs arranged in each of the plurality of sub-pixels may be LEDs that emit light of the same hue, or may be LEDs that emit light of different hues from each other. For example, when each of the plurality of LEDs emits light of a different hue, some of the plurality of LEDs may be red LEDs that emit red light, some of the plurality of LEDs may be green LEDs that emit green light, and the rest of the plurality of LEDs may be blue LEDs that emit blue light. And a variety of hues of light including white can be realized by a combination of light from the red LEDs, green LEDs, and blue LEDs.

[0034] And when the plurality of LEDs emit light of the same hue, a light conversion member can be arranged together with the plurality of LEDs. For example, when the plurality of LEDs are blue LEDs, a red light conversion layer and a green light conversion layer can be arranged together in each of the plurality of sub-pixels. However, the types and numbers of LEDs arranged in the plurality of sub-pixels constituting the pixel PX can be variously configured according to embodiments and are not limited thereto.

[0035] The plurality of pixels PX can be arranged at equal intervals. The plurality of pixels PX can be arranged at the same interval. For example, the interval from the center of one pixel PX to the center of an adjacent pixel PX among the plurality of pixels PX may be a first interval D1. And the first interval D1, which is the interval between the pixels PX, can also be defined as the pixel pitch.

[0036] In the following, FIG. 2 will be referred to together for a more detailed description of the plurality of pixels PX.

[0037] FIG. 2 is a schematic cross-sectional view of sub-pixels forming a plurality of pixels of a display device according to an embodiment of the present invention.

[0038] Referring to FIG. 2, the substrate 110 is a support member for supporting other components of the display device 100 and may be made of an insulating material. For example, the substrate 110 may be made of glass, resin, or the like. Also, the substrate 110 may comprise a plastic such as a polymer or polyimide (PI), etc., and may be made of a material having flexibility.

[0039] The driving transistor 120 is disposed on the substrate 110 of the display panel PN. The driving transistor 120 can be used as a driving element of the display device 100. The driving transistor 120 includes a gate electrode 121, an active layer 122, a source electrode 123, and a drain electrode 124.

[0040] The gate electrode 121 is disposed on the substrate 110. The gate electrode 121 can be made of a conductive material, for example, copper (Cu), aluminum (Al), molybdenum (Mo), titanium (Ti), or an alloy thereof, but is not limited thereto.

[0041] The gate insulating layer 111 is disposed on the gate electrode 121. The gate insulating layer 111 is a layer for insulating the gate electrode 121 and the active layer 122 and may be made of an insulating material. For example, the gate insulating layer 111 can be formed of a single layer or a multi-layer of silicon oxide (SiOx) or silicon nitride (SiNx), but is not limited thereto.

[0042] The active layer 122 is disposed on the gate insulating layer 111. For example, the active layer 122 can be made of an oxide semiconductor, amorphous silicon, polysilicon, or the like, but is not limited thereto.

[0043] A source electrode 123 and a drain electrode 124 are arranged on the active layer 122 while being separated from each other. The source electrode 123 and the drain electrode 124 can be electrically connected to the active layer 122. The source electrode 123 and the drain electrode 124 can be composed of a conductive material, for example, copper (Cu), aluminum (Al), molybdenum (Mo), titanium (Ti), or an alloy thereof, but are not limited thereto.

[0044] On the other hand, in this specification, the driving transistor 120 is illustrated as a driving transistor 120 having a structure in which the gate electrode 121 is disposed at the lowermost part, the active layer 122 is disposed on the gate electrode 121, and the source electrode 123 and the drain electrode 124 are disposed on the active layer 122, but is not limited thereto.

[0045] A common wiring CL is disposed on the gate insulating layer 111. The common wiring CL can transmit a common power supply supplied from the outside to the plurality of LEDs of the plurality of sub-pixels. The common wiring CL can be made of the same material as the source electrode 123 and the drain electrode 124 of the driving transistor 120 and formed in the same process, but the material and arrangement of the common wiring CL are not limited thereto.

[0046] A first insulating layer 112 is disposed on the driving transistor 120 and the common wiring CL. The first insulating layer 112 is disposed above the driving transistor 120 and can protect the driving transistor 120. The first insulating layer 112 can be made of an organic material such as benzocyclobutene or photo acryl.

[0047] An LED is disposed on the first insulating layer 112. The LED may be an LED (Light Emitting Diode) or a Micro LED made of an inorganic material. The LED may be electrically connected to the source electrode 123 or the drain electrode 124 of the driving transistor 120 through a contact hole formed in the first insulating layer 112. On the other hand, in FIG. 2, it is shown that the LED is disposed on the patterned first insulating layer 112, but the LED may be disposed on the first insulating layer 112 having a flat upper surface without being patterned, and the present invention is not limited thereto.

[0048] When a plurality of LEDs are LEDs, they can be formed in various structures such as a lateral type, a vertical type, and a flip chip. The horizontal LED includes an n electrode NE and a p electrode PE horizontally disposed on both sides of the light emitting layer EL. The vertical LED includes an n electrode NE and a p electrode PE disposed above and below the light emitting layer EL. The flip chip LED has substantially the same structure as the horizontal LED. In the horizontal LED, the n electrode NE and the p electrode PE are horizontally disposed above the light emitting layer EL, while in the flip chip LED, the n electrode NE and the p electrode PE are horizontally disposed below the light emitting layer EL. In the following description, it is assumed that the plurality of LEDs are horizontal structure LEDs, but the types of the plurality of LEDs are not limited thereto.

[0049] On the other hand, the LED can be manufactured by a process separate from the TFT array process of the display panel PN. For example, a plurality of LEDs can be formed on a wafer 200 made of a material such as sapphire and disposed on the display panel PN on which the driving transistor 120 and various wirings are disposed through a transfer process.

[0050] The LED includes a p-type semiconductor layer PL, a light emitting layer EL, an n-type semiconductor layer NL, a p electrode PE, and an n electrode NE.

[0051] An n-type semiconductor layer NL is disposed on a first insulating layer 112, and a p-type semiconductor layer PL is disposed on the n-type semiconductor layer NL. The p-type semiconductor layer PL and the n-type semiconductor layer NL may be layers formed by implanting n-type or p-type impurities into gallium nitride (GaN). For example, the p-type semiconductor layer PL may be a layer formed by implanting p-type impurities into gallium nitride, and the n-type semiconductor layer NL may be a layer formed by implanting n-type impurities into gallium nitride, but is not limited thereto. The p-type impurities may be magnesium (Mg), zinc (Zn), beryllium (Be), etc., and the n-type impurities may be silicon (Si), germanium (Ge), tin (Sn), etc., but are not limited thereto.

[0052] A light-emitting layer EL is disposed between the p-type semiconductor layer PL and the n-type semiconductor layer NL. The light-emitting layer EL can emit light by receiving supply of holes and electrons from the p-type semiconductor layer PL and the n-type semiconductor layer NL. The light-emitting layer EL may be formed in a single-layer or multi-quantum well (MQW) structure. For example, the light-emitting layer EL may be made of indium gallium nitride (InGaN), gallium nitride (GaN), etc., but is not limited thereto. A p-electrode PE is disposed on the p-type semiconductor layer PL, and an n-electrode NE is disposed on the n-type semiconductor layer NL. The p-electrode PE can be electrically connected to the p-type semiconductor layer PL, and the n-electrode NE can be electrically connected to the n-type semiconductor layer NL.

[0053] A second insulating layer 113 is disposed on the LED and the first insulating layer 112. The second insulating layer 113 is disposed on top of the plurality of LEDs and can protect the plurality of LEDs. The second insulating layer 113 may be made of an organic material such as benzocyclobutene or photo acryl.

[0054] The first connection electrode CE1 and the second connection electrode CE2 are disposed on the second insulating layer 113. The first connection electrode CE1 can electrically connect the driving transistor 120 and the LED through the contact holes of the first insulating layer 112 and the second insulating layer 113. For example, the first connection electrode CE1 can electrically connect the drain electrode 124 of the driving transistor 120 and the p electrode PE of the LED. The first connection electrode CE1 can be made of a transparent metal oxide such as ITO (Indium Tin Oxide), IGZO (Indium Gallium Zinc Oxide), or IGO (Indium Gallium Oxide), but is not limited thereto.

[0055] The second connection electrode CE2 can electrically connect the common wiring CL and the LED through the contact holes of the first insulating layer 112 and the second insulating layer 113. For example, the second connection electrode CE2 can electrically connect the common wiring CL and the n electrode NE of the LED. The second connection electrode CE2 can be made of a transparent metal oxide such as ITO (Indium Tin Oxide), IGZO (Indium Gallium Zinc Oxide), or IGO (Indium Gallium Oxide), but is not limited thereto.

[0056] A protective layer 114 is disposed on the first connection electrode CE1 and the second connection electrode CE2. The protective layer 114 is disposed on the entire surface of the display panel PN and can protect the circuit including the plurality of LEDs and the driving transistor 120 from external impacts. The protective layer 114 can be made of, for example, OCA (optical clear adhesive) or OCR (optical clear resin), but is not limited thereto.

[0057] On the other hand, although not shown in the drawings, a reflective layer disposed so as to overlap the plurality of LEDs may be further disposed. The reflective layer is disposed so as to overlap the plurality of LEDs and can reflect the light emitted from the plurality of LEDs to the outside of the display device 100, thereby improving the light efficiency of the display device 100.

[0058] Hereinafter, with reference to FIGS. 3 to 4G, a method for transferring an LED according to an embodiment of the present invention and a method for manufacturing a display device 100 using the same will be described.

[0059] FIG. 3 is a flowchart of steps for explaining a method for manufacturing a display device according to an embodiment of the present invention. FIGS. 4A to 4G are schematic process diagrams for explaining a method for transferring an LED according to an embodiment of the present invention and a method for manufacturing a display device using the same. Specifically, FIGS. 4A to 4F are schematic process diagrams for explaining a primary transfer process, and FIG. 4G is a schematic process diagram for explaining a secondary transfer process. FIG. 4A is a plan view of a wafer 200, and FIG. 4B is a plan view of a donor substrate 300. FIG. 4C is a cross-sectional view taken along line A-A' of FIG. 4B. FIGS. 4D and 4E are schematic cross-sectional views for explaining a detachment process of the wafer 200 and the donor substrate 300. For convenience of explanation, the donor substrate 300, the wafer 200, and a plurality of LEDs are schematically shown. FIG. 4F is a plan view of the donor substrate 300 after the primary transfer process is completed. FIG. 4G is a cross-sectional view of the donor substrate 300 and the display panel PN for explaining the secondary transfer process.

[0060] First, referring to FIG. 3, the primary transfer process can be carried out to transfer a plurality of LEDs on the wafer 200 to the donor substrate 300, and the secondary transfer process can be carried out to transfer the plurality of LEDs on the donor substrate 300 to the display panel PN. Thus, the manufacturing process of the display device 100 can be completed by transferring a plurality of LEDs from the wafer 200 to the donor substrate 300 and from the donor substrate 300 to the display panel PN.

[0061] Hereinafter, the primary transfer process will be described with reference to FIGS. 3, 4A to 4F first.

[0062] Referring to both FIG. 3 and FIG. 4A, the wafer 200 is a substrate on which a plurality of LEDs are formed. Substances such as gallium nitride (GaN) and indium gallium nitride (InGaN) that constitute a plurality of LEDs can be formed on the wafer 200 to grow a crystal layer, and the crystal layer can be cut into individual chips and electrodes can be formed to form a plurality of LEDs. The wafer 200 can be made of sapphire, silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), etc., but is not limited thereto. And since the wafer 200 is made of a hard substance such as sapphire, it can be defined as a rigid substrate.

[0063] At this time, a plurality of LEDs that emit light of the same hue may be formed on one wafer 200, or a plurality of LEDs that emit light of mutually different hues may be formed. In the following, it will be described on the assumption that a plurality of LEDs that emit light of the same hue are formed on one wafer 200.

[0064] The wafer 200 includes an active region 200A and an outer peripheral region 200B. The active region 200A is a region where a plurality of LEDs are formed, and the outer peripheral region 200B disposed outside the active region 200A is a region where at least one or more dams DM and a plurality of alignment keys AK are disposed.

[0065] A plurality of LEDs are arranged in the active region 200A. The plurality of LEDs can be formed by patterning an epitaxial layer formed on the wafer 200. Specifically, after growing substances that form an n-type semiconductor layer NL, a light-emitting layer EL, and a p-type semiconductor layer PL that form a plurality of LEDs on the wafer 200, it can be patterned into a plurality of pieces, that is, an isolation process can be carried out to form a plurality of LEDs. The plurality of LEDs can be arranged at a second interval D2. The second interval D2 may be the interval from the center of one LED among the plurality of LEDs to the center of the adjacent LED. And the second interval D2 may be smaller than the first interval D1 which is the interval between the plurality of pixels PX of the display panel PN.

[0066] The plurality of alignment keys AK arranged in the outer peripheral region 200B includes a first alignment key AK1 and a second alignment key AK2. The first alignment key AK1 and the second alignment key AK2 can be arranged in the outer peripheral region 200B. However, the first alignment key AK1 and the second alignment key AK2 are not limited to those shown in the drawings, and their numbers and positions can be designed in various ways.

[0067] The first alignment key AK1 is a component used to align the wafer 200 and the donor substrate 300. The first alignment key AK1 is a mark for aligning and parallelizing the donor substrate 300 when transferring a plurality of LEDs on the wafer 200 to the donor substrate 300. The first alignment key AK1 on the wafer 200 and the alignment protrusion 332 on the donor substrate 300 can be aligned to align and parallelize the wafer 200 and the donor substrate 300.

[0068] For example, the first alignment key AK1 may be a metal pattern arranged between a plurality of dams DM in the outer peripheral region 200B, or formed on the upper part or the lower part of the plurality of dams DM. Therefore, the first alignment key AK1 can be detected by a vision method to align the wafer 200 and the donor substrate 300. In this case, even if the first alignment key AK1 is formed on the dam DM described later, since the first alignment key AK1 is a kind of metal pattern, the step generated between the wafer 200 and the donor substrate 300 by the first alignment key AK1 can be negligible. Therefore, the first alignment key AK1 can be formed without being limited to the position of the dam DM in the outer peripheral region 200B.

[0069] The second alignment key AK2 is a component used to align the donor substrate 300 and the display panel PN. The second alignment key can be transferred to the donor substrate 300 together with a plurality of LEDs when transferring the plurality of LEDs on the wafer 200 to the donor substrate 300. Thereafter, the second alignment key AK2 on the donor substrate 300 can be used to align and parallelize the donor substrate 300 and the display panel PN.

[0070] The first alignment key AK1 and the second alignment key AK2 may be formed together during the formation of a plurality of LEDs, or may be formed in a process separate from the plurality of LEDs. If the first alignment key AK1 and the second alignment key AK2 are formed together with the plurality of LEDs, the first alignment key AK1 and the second alignment key AK2 may be made of the same material as at least a part of the material forming the plurality of LEDs. However, the materials and formation processes of the first alignment key AK1 and the second alignment key AK2 can be configured in various ways according to the design and are not limited thereto.

[0071] The shapes and sizes of the first alignment key AK1 and the second alignment key AK2 can be configured in various ways. In order to distinguish the first alignment key AK1 and the second alignment key AK2 disposed in the outer region 200B, the shapes or sizes of the first alignment key AK1 and the second alignment key AK2 can be configured to be different. For example, the size of the first alignment key AK1 may be larger than the size of the second alignment key AK2, but it is not limited thereto.

[0072] One or more dams DM are disposed in the outer region 200B. The dam DM is configured to improve the contact area with the donor substrate 300 described later and improve the adhesion force with the donor substrate 300. One or more dams DM can be formed together with the plurality of LEDs. Specifically, a part of the epi-layer that overlaps the outer region 200B can be left without being patterned during the process of patterning the epi-layer into a plurality of pieces, and one or more dams DM can be formed. Therefore, the height of the dam DM can be formed to be substantially the same as the height of the plurality of LEDs.

[0073] On the one hand, the minimum width of the dam DM can be designed in consideration of the interval by which the wafer 200 and the donor substrate 300 are most shifted and the width of the region where a plurality of dam protrusions 335 of the donor substrate 300 are arranged. In the selective transfer method of transferring only some of the plurality of LEDs on the wafer 200 to the donor substrate 300, the bonding position of the donor substrate 300 and the wafer 200 can change little by little. For example, the bonding position of the donor substrate 300 and the wafer 200 can change within the third interval D3 which is the interval between a plurality of chip protrusions 331 of the donor substrate 300 described later. At this time, at least a part of the dam DM can be in contact with a plurality of dam protrusions 335 in a non-transfer region 330B of the donor substrate 300 described later so as to improve the bonding force between the donor substrate 300 and the wafer 200. In this case, in order to bring at least a part of the dam DM into contact with the plurality of dam protrusions 335, the interval by which the donor substrate 300 and the wafer 200 are most shifted, for example, must be configured to be equal to or greater than the third interval D3. If the minimum width of the dam DM is less than or equal to the third interval D3, at least a part of the dam DM may be difficult to bond with the non-transfer region 330B of the donor substrate 300, and the bonding force between the donor substrate 300 and the wafer 200 may decrease. Therefore, by configuring the minimum width of the dam DM to be equal to or greater than the interval by which the wafer 200 and the donor substrate 300 are most shifted, the bonding force between the wafer 200 and the donor substrate 300 can be ensured to be at a certain level or higher during the transfer process.

[0074] The interval between the dam DM in the outer peripheral region 200B and the LED arranged at the outermost periphery in the active region 200A may be the same as or even larger than the interval from the outer periphery of one LED to the outer periphery of the adjacent LED. At this time, the interval from the outer periphery of one LED to the outer periphery of the adjacent LED is an interval smaller than the second interval D2. By forming the interval between the dam DM in the outer peripheral region 200B and the LED arranged at the outermost periphery of the active region 200A to be the same as or larger than the interval from the outer periphery to the outer periphery of the LED, the interference between the LEDs during the transfer process can be minimized, which will be described later with reference to FIG. 4E.

[0075] On the one hand, in FIG. 4A, although the dam DM is shown as being disposed adjacent to each of the four sides of the active region 200A, the dam DM may be formed to extend to the edge of the wafer 200 or may be formed over the entire outer peripheral region 200B except for the portion where structures such as a plurality of alignment keys AK are formed, and is not limited thereto.

[0076] On the other hand, the second alignment key AK2 can be disposed with the active region 200A and the dam DM interposed therebetween. The second alignment key AK2 can be disposed outside the dam DM in the outer peripheral region 200B. When the second alignment key AK2 is formed in the same process as a plurality of LEDs, the second alignment key AK2 can also be formed by being patterned together when patterning the epitaxial layer for forming the plurality of LEDs. That is, the second alignment key AK2 can be formed by patterning the epitaxial layer formed in the outer peripheral region 200B. At this time, after sufficiently securing the region where the dam DM is to be formed, the second alignment key AK2 can be formed outside the dam DM. Therefore, the second alignment key AK2 can be disposed at a distance from the active region 200A with a minimum width of the dam DM, for example, at an interval of not less than the third interval D3.

[0077] Referring to FIG. 4B, the donor substrate 300 includes a base layer 310, an adhesive layer 320, a resin layer 330, a plurality of chip protrusions 331, a plurality of alignment protrusions 332, and a plurality of dam protrusions 335.

[0078] The base layer 310 is a configuration for supporting various components included in the donor substrate 300, and may be made of at least a material harder (rigid) than the resin layer 330 in order to minimize the warpage of the resin layer 330. The base layer 310 is disposed below the resin layer 330 and can support the resin layer 330, the plurality of chip protrusions 331, and the plurality of alignment protrusions 332. For example, the base layer 310 may include a polymer or plastic, etc., and may be made of PC (Poly Carbonate) or PET (Poly Ethylene Terephthalate), etc., but is not limited thereto.

[0079] A resin layer 330 is disposed on the base layer 310. During the transfer process, the resin layer 330 can support a plurality of chip protrusions 331 to which a plurality of LEDs are attached. The resin layer 330 can be made of a polymer resin having viscoelasticity. For example, the resin layer 330 can be composed of PDMS (Poly Di Methyl Siloxane), PUA (Poly Urethane Acrylate), PEG (Poly Ethylene Glycol), PMMA (Poly Methyl Meth Acrylate), PS (Poly Styrene), epoxy resin, urethane resin, acrylic resin, etc., but is not limited thereto.

[0080] The resin layer 330 includes a transfer region 330A and a non-transfer region 330B. The transfer region 330A is a region where a plurality of chip protrusions 331 are arranged. The transfer region 330A is a region where a plurality of chip protrusions 331 to which a plurality of LEDs are attached are arranged, and can be arranged to overlap at least a part of the wafer 200 or the display panel PN during the transfer process.

[0081] The non-transfer region 330B is a region where a plurality of alignment protrusions 332 and a plurality of dam protrusions 335 are arranged. The second alignment key AK2 of the wafer 200 can be transferred to the non-transfer region 330B.

[0082] The plurality of chip protrusions 331 are protrusions on which a plurality of LEDs are arranged, and can be formed to extend from one surface of the resin layer 330. The plurality of chip protrusions 331 can be integrated with the resin layer 330 and can be made of a polymer material having viscoelasticity similar to that of the resin layer 330. For example, the plurality of chip protrusions 331 can be composed of PDMS (Poly Di Methyl Siloxane), PUA (Poly Urethane Acrylate), PEG (Poly Ethylene Glycol), PMMA (Poly Methyl Meth Acrylate), PS (Poly Styrene), epoxy resin, urethane resin, acrylic resin, etc., but is not limited thereto.

[0083] On the upper surfaces of the plurality of chip protrusions 331, a plurality of LEDs can be temporarily attached. The plurality of LEDs formed on the wafer 200 can be transferred onto the upper surfaces of the plurality of chip protrusions 331, and the plurality of LEDs can temporarily maintain a state of being attached to the upper surfaces of the plurality of chip protrusions 331 until being transferred to the display panel PN. Then, a donor substrate 300 including a resin layer 330 made of a soft material and the plurality of chip protrusions 331 integrated with the resin layer 330 and having a plurality of LEDs temporarily attached thereon can be defined as a flexible substrate.

[0084] At this time, the plurality of chip protrusions 331 can be arranged at a third interval D3. The third interval D3 may be a larger interval than a second interval D2 which is the interval between the plurality of LEDs on the wafer 200. The third interval D3 of the plurality of chip protrusions 331 may be N times the second interval D2 of the plurality of LEDs on the wafer 200. In this case, only some of the plurality of LEDs arranged at the second interval D2 on the wafer 200 can be transferred onto the plurality of chip protrusions 331 of the donor substrate 300. For example, when the third interval D3 is twice the second interval D2, the odd-numbered LEDs or the even-numbered LEDs can be selectively transferred in a line onto the plurality of chip protrusions 331.

[0085] The third interval D3 may be the first interval D1, which is the interval between a plurality of pixels PX of the display panel PN, that is, an interval that is N times or 1 / N times the pixel pitch. Specifically, the third interval D3 from the center of one chip protrusion 331 to the center of an adjacent chip protrusion 331 may be N times or 1 / N times the pixel pitch. By forming the intervals between the plurality of chip protrusions 331 to be N times or 1 / N times the pixel pitch, the pixel pitch of the display panel PN can be varied on one donor substrate 300, and a plurality of LEDs can be transferred. Considering the third interval D3, which is the interval between the plurality of chip protrusions 331, and the first interval D1, which is the pixel pitch, a plurality of LEDs arranged on the plurality of chip protrusions 331 can be selectively transferred to vary the pixel pitch. For example, when the pixel pitch is formed to be the same as the second interval D2, which is the interval between the plurality of chip protrusions 331, the plurality of LEDs on the plurality of chip protrusions 331 can be transferred to the display panel PN at once. For example, when the pixel pitch is formed to be twice the third interval D3 of the plurality of chip protrusions 331, the pixel pitch can be adjusted by transferring only the plurality of LEDs on the odd-numbered chip protrusions 331 or the even-numbered chip protrusions 331 among the plurality of chip protrusions 331 arranged in the same row. However, the arrangement and intervals of the plurality of chip protrusions 331 can be variously changed according to the design and are not limited thereto.

[0086] The size of the plurality of chip protrusions 331 may be larger than the size of the plurality of LEDs. By forming the upper surface size of the plurality of chip protrusions 331 to be larger than that of the plurality of LEDs, the plurality of LEDs can be landed on the plurality of chip protrusions 331 even if an alignment error occurs between the donor substrate 300 and the wafer 200. Therefore, considering the alignment error between the wafer 200 and the donor substrate 300, the upper surface size of the plurality of chip protrusions 331 can be formed to be larger than that of the plurality of LEDs.

[0087] A plurality of alignment protrusions 332 and a plurality of dam protrusions 335 are arranged in the non-transfer region 330B. The plurality of alignment protrusions 332 include a plurality of first alignment protrusions 333 and a plurality of second alignment protrusions 334.

[0088] The plurality of first alignment protrusions 333 are components used to align the wafer 200 and the donor substrate 300. The plurality of first alignment protrusions 333 can be arranged to correspond to the first alignment key AK1 of the wafer 200. For example, the first alignment key AK1 of the first wafer 200 and the first alignment protrusions 333 of the donor substrate 300 can be aligned to align the wafer 200 and the donor substrate 300 and make their parallelism consistent. At this time, the first alignment protrusions 333 and the first alignment key AK1 can have different shapes or sizes to facilitate identification. For example, either one of the first alignment protrusions 333 and the first alignment key AK1 can be in a donut shape with a hole formed in the middle, and the other one can be in a circular shape that overlaps the hole. In FIGS. 4a and 4b, the first alignment key AK1 of the wafer 200 and the first alignment protrusions 333 of the donor substrate 300 are shown as circular, but the shapes of the first alignment key AK1 and the first alignment protrusions 333 are not limited thereto.

[0089] The second alignment protrusions 334 can be arranged to correspond to the second alignment key AK2 of the wafer 200. For example, two second alignment protrusions 334 can be arranged in each of the non-transfer region 330B arranged above the transfer region 330A and the non-transfer region 330B arranged below the transfer region 330A of the donor substrate 300. After aligning the first alignment key AK1 of the wafer 200 and the first alignment protrusions 333 of the donor substrate 300 to align the wafer 200 and the donor substrate 300, the plurality of LEDs on the wafer 200 are transferred to the plurality of chip protrusions 331 on the donor substrate 300, and the second alignment key AK2 of the wafer 200 can be transferred to the second alignment protrusions 334 of the donor substrate 300. At this time, the second alignment key AK2 transferred to the donor substrate 300 can be used when aligning the display panel PN and the donor substrate 300.

[0090] The plurality of dam projections 335 can, during the transfer process, contact the dam DM of the wafer 200 to improve the adhesion force between the wafer 200 and the donor substrate 300, and at the same time minimize the deformation of the plurality of chip projections 331 from the impact applied to the donor substrate 300. For example, after the wafer 200 and the donor substrate 300 are bonded together, when transferring a plurality of LEDs onto the donor substrate 300, the plurality of LEDs may move on the donor substrate 300 and an impact may be applied to the donor substrate 300. When an impact is applied to the donor substrate 300, the positions, shapes, etc. of the plurality of chip projections 331 in the resin layer 330 and the transfer region 330A may be deformed. At this time, the plurality of dam projections 335 in the non-transfer region 330B arranged to surround the transfer region 330A can maintain the state of being bonded to the wafer 200 and minimize the deformation of the plurality of chip projections 331 in the resin layer 330 and the transfer region 330A. Also, the plurality of dam projections 335 can contact one or more dams DM of the wafer 200 to maintain the state in which the wafer 200 and the donor substrate 300 are bonded together.

[0091] And at least one or more dam projections 335 can be arranged adjacent to the plurality of alignment projections 332. At least one or more dam projections 335 can be arranged between the plurality of alignment projections 332 and the transfer region 330A or between the plurality of alignment projections 332 and the edge of the resin layer 330. During the transfer process, at least one or more dam projections 335 can be arranged adjacent to the plurality of alignment projections 332 so as to minimize the weakening of the adhesion force between the donor substrate 300 and the wafer 200 in the region where the plurality of alignment projections 332 are arranged and the separation of the donor substrate 300 and the wafer 200.

[0092] The plurality of dam projections 335 may be equal to or larger than the size of the plurality of chip projections 331 and may have the same height as the plurality of chip projections 331. When the plurality of dam projections 335 are equal to or larger than the size of the plurality of chip projections 331, they can be formed in various shapes. For example, a plurality of first dam projections 335a arranged in the non-transfer regions 330B above and below the transfer region 330A among the plurality of dam projections 335 may be formed in a square shape and may be arranged at intervals from each other. For example, a plurality of second dam projections 335b arranged in the non-transfer regions 330B on the left and right sides of the transfer region 330A among the plurality of dam projections 335 may be formed in a rectangular shape. However, the shapes of the plurality of dam projections 335 can be configured in various ways and are not limited thereto.

[0093] And the minimum width of the region where the plurality of dam projections 335 are arranged may be the same as the minimum width of the dam DM. For example, the minimum width of the region where the plurality of dam projections 335 are arranged may be configured to be equal to or greater than a third interval D3, which is the interval at which the wafer 200 and the donor substrate 300 are most shifted. At this time, in the drawing, it is shown that the plurality of dam projections 335 are arranged in the entire non-transfer region 330B and the width of the non-transfer region 330B where the plurality of dam projections 335 are arranged corresponds to the minimum width of the dam DM of the wafer 200. However, the plurality of dam projections 335 may be arranged only in a part of the non-transfer region 330B, and the width of the non-transfer region 330B and the size of the region where the plurality of dam projections 335 are arranged may be different and are not limited thereto.

[0094] By arranging a plurality of dam projections 335 spaced apart from each other in the non-transfer region 330B of the donor substrate 300, it is possible to reduce the trapping of air between the dam DM and the dam projections 335 when the wafer 200 and the donor substrate 300 are bonded together. This will be described in detail later with reference to FIG. 4C.

[0095] On the other hand, on the donor substrate 300, a plurality of chip protrusions 331 may not be provided, and a plurality of LEDs may be directly transferred onto the resin layer 330. That is, the donor substrate 300 may not include separate chip protrusions 331. The structure of the donor substrate 300 can vary depending on the shape, arrangement, transfer method, etc. of the plurality of LEDs, and is not limited thereto. In the following, for convenience of explanation, it is assumed that the donor substrate 300 includes a plurality of chip protrusions 331, and a plurality of LEDs are transferred to each of the plurality of chip protrusions 331.

[0096] An adhesive layer 320 is disposed between the resin layer 330 and the base layer 310. The adhesive layer 320 adheres the resin layer 330 to the display panel PN. The adhesive layer 320 can be made of a substance having adhesiveness, and can be made of, for example, OCA (Optical Clear Adhesive), PSA (Pressure Sensitive Adhesive), etc., but is not limited thereto.

[0097] However, the adhesive layer 320 may be omitted by design. For example, after directly coating the substance forming the resin layer 330 on the base layer 310 and then curing it, the resin layer 330 can be formed. In such a case, since the resin layer 330 can be attached to the base layer 310 without disposing the adhesive layer 320, the adhesive layer 320 may be omitted by design and is not limited thereto.

[0098] Next, referring to FIG. 4C together, the wafer 200 on which a plurality of LEDs are formed and the donor substrate 300 are loaded into the process equipment. Then, the wafer 200 and the donor substrate 300 loaded into the process equipment are aligned. The wafer 200 and the donor substrate 300 can be aligned in a state where the plurality of LEDs on the wafer 200 and the plurality of chip protrusions 331 of the donor substrate 300 face each other. For example, the wafer 200 and the donor substrate 300 can be aligned by aligning the center of the first alignment key AK1 of the wafer 200 with the center of the first alignment protrusion 333 of the donor substrate 300.

[0099] After the alignment of the wafer 200 and the donor substrate 300 is completed, the wafer 200 and the donor substrate 300 are bonded together (S110). The plurality of LEDs in the active region 200A of the wafer 200 correspond to the plurality of chip protrusions 331 in the transfer region 330A of the donor substrate 300, and the dam DM in the outer region 200B of the wafer 200 and the wafer 200 and the donor substrate 300 can be bonded together so as to correspond to the plurality of dam protrusions 335 in the non-transfer region 330B of the donor substrate 300.

[0100] At this time, the dam DM of the wafer 200 and the plurality of dam protrusions 335 of the donor substrate 300 can be bonded together, increasing the contact area between the wafer 200 and the donor substrate 300, and the wafer 200 and the donor substrate 300 can be bonded together uniformly. For example, the dam DM arranged to surround the active region 200A of the wafer 200 can be bonded to the plurality of dam protrusions 335 of the donor substrate 300 so that the entire wafer 200 and the entire donor substrate 300 can be bonded together uniformly. If the dam DM is formed only on a part of the four sides of the active region 200A in the wafer 200, a bonding force difference may occur between the region where the dam DM is formed and the region where the dam DM is not formed, making it difficult for the entire surfaces of the wafer 200 and the donor substrate 300 to be bonded together uniformly. In this case, a bonding failure may occur between the plurality of LEDs of the wafer 200 and the plurality of chip protrusions 331 of the donor substrate 300. Therefore, by forming a plurality of dams DM in the entire outer region 200B of the wafer 200, the bonding force between the wafer 200 and the donor substrate 300 can be uniformly improved.

[0101] Then, in the non-transfer region 330B of the donor substrate 300 corresponding to the outer peripheral region 200B of the wafer 200, a plurality of dam protrusions 335 spaced apart from each other can be arranged to minimize air trapping. Specifically, in the outer peripheral region 200B of the wafer 200, a dam DM having a size relatively larger than that of the plurality of dam protrusions 335 can be arranged. If the dam protrusions 335 are formed to have a size corresponding to that of the dam DM, even if the contact area between the dam DM and the dam protrusions 335 increases and the adhesion force between the wafer 200 and the donor substrate 300 increases, there may be a region where air is trapped by the dam DM and the dam protrusions 335 and non-bonding occurs. Therefore, the dam protrusions 335 corresponding to the dam DM are formed as a plurality of dam protrusions 335 spaced apart from each other, and air can be moved to the outside of the wafer 200 and the donor substrate 300 through the empty space between the plurality of dam protrusions 335. At this time, the dam protrusions 335 arranged above or below the transfer region 330A can form an air passage extending in the column direction, and the dam protrusions 335 arranged on the left or right side of the transfer region 330A can form an air passage extending in the row direction. Therefore, by arranging a plurality of dam protrusions 335 spaced apart from each other in the non-transfer region 330B of the donor substrate 300, a path through which air moves when the wafer 200 and the donor substrate 300 are bonded can be formed, and a region where air is trapped and the wafer 200 and the donor substrate 300 are not bonded can be reduced.

[0102] Next, a plurality of LEDs of the wafer 200 are transferred to the donor substrate 300 (S120). In a state where the wafer 200 and the donor substrate 300 are arranged to face each other, a laser can be selectively irradiated only to the LEDs to be transferred to the donor substrate 300 among the plurality of LEDs. The LEDs irradiated with the laser can be detached from the wafer 200 and adhere to the plurality of chip protrusions 331 of the donor substrate 300.

[0103] Depending on the design, a plurality of LEDs may be transferred only to some of the plurality of chip protrusions 331 of the donor substrate 300, or a plurality of LEDs may be transferred to the entire plurality of chip protrusions 331. For example, when transferring red LEDs, green LEDs, and blue LEDs from different wafers 200 onto a single donor substrate 300 to transfer the red LEDs, green LEDs, and blue LEDs to the display panel PN at once, LEDs can be transferred from only some of the chip protrusions 331 out of the plurality of chip protrusions 331 from one wafer 200. For example, when transferring only one type of LED onto a single donor substrate 300 to transfer only one type of LED to the display panel PN, LEDs can also be transferred from one wafer 200 to the entire plurality of chip protrusions 331. However, considering the second interval D2 which is the interval between the plurality of chip protrusions 331, the first interval D1 which is the interval between the plurality of pixels PX of the display panel PN, etc., the type of LEDs transferred during the transfer process, the position, and the number of the chip protrusions 331 to which the LEDs are transferred can be designed in various ways and are not limited thereto.

[0104] On the other hand, at least some of the plurality of second alignment keys AK2 of the wafer 200 can also be transferred to the donor substrate 300. In a state where the wafer 200 and the donor substrate 300 are arranged to face each other, a laser can be selectively irradiated only to some of the second alignment keys AK2 to be transferred to the donor substrate 300 out of the plurality of second alignment keys AK2. Then, the second alignment key AK2 irradiated with the laser can be detached from the wafer 200 and adhered to the second alignment protrusion 334 of the donor substrate 300.

[0105] In this case, if the plurality of second alignment keys AK2 are arranged offset and biased on the plurality of second alignment protrusions 334, the plurality of LEDs maintaining a certain interval from the plurality of second alignment keys AK2 can also be arranged offset and biased on the plurality of chip protrusions 331. Therefore, the positions of the plurality of LEDs can be easily grasped through the second alignment key AK2. However, the second alignment key AK2 does not necessarily have to be transferred together with the plurality of LEDs and is not limited thereto.

[0106] Next, referring to FIGS. 4D and 4E, after a plurality of LEDs on the wafer 200 are transferred to the donor substrate 300, the wafer 200 and the donor substrate 300 are detached (S130).

[0107] Referring to FIG. 4D, the wafer 200 and the donor substrate 300 in the bonded state can be loaded onto the stage ST. The wafer 200 and the donor substrate 300 in the bonded state can be positioned between the stage ST and the head HD. The wafer 200 can be arranged to correspond to the head HD, and the donor substrate 300 can be arranged to correspond to the stage ST.

[0108] However, in this specification, although it has been described that the wafer 200 and the donor substrate 300 are moved to the stage ST for the detachment process of the wafer 200 and the donor substrate 300, the bonding and detachment processes of the wafer 200 and the donor substrate 300 may be performed on the same stage and are not limited thereto.

[0109] Next, a part of the outermost portion of the donor substrate 300 is physically fixed to the stage ST (S131). The fixing member GR can be used to fix one edge of the plurality of edges of the donor substrate 300 or at least one corner of the four corners of the donor to the stage ST. And the remaining portion of the donor substrate 300 not fixed to the stage ST by the fixing member GR can be movable on the stage ST. For example, one edge of the outermost portion of the donor substrate 300 can be fixed to the stage ST with a gripper. For example, two adjacent corner portions of the outermost portion of the donor substrate 300 can be fixed to the stage ST with a gripper. The stage ST does not need to vacuum-adsorb the donor substrate 300, and the stage ST and the donor substrate 300 can be physically fixed by the fixing member GR.

[0110] Then, the wafer 200 is fixed to the head HD (S132). One side of the wafer 200 can be fixed to the head HD. For example, the entire one side of the wafer 200 can be fixed to the head HD by a vacuum adsorption method or by a fixing member. In this case, the stage ST may be moved toward the head HD side to vacuum-adsorb the head HD and the wafer 200, or the head HD may be moved toward the wafer 200 side to vacuum-adsorb the head HD and the wafer 200.

[0111] Next, referring to FIG. 4E, the head HD and / or the stage ST is moved (S133). The head HD and the stage ST are separated from each other to detach the wafer 200 and the donor substrate 300. Specifically, the head HD, the stage ST, or the head HD and the stage ST are moved away from each other to detach the wafer 200 fixed to the head HD and the donor substrate 300 partially fixed to the stage ST. At this time, at least one of the head HD and the stage ST is moved in a direction perpendicular to one side of the stage ST, that is, in the Z-axis direction, to detach the wafer 200 and the donor substrate 300. For example, either the head HD or the stage ST can be moved in the Z-axis direction, or both the head HD and the stage ST can be moved in the Z-axis direction.

[0112] In this case, the wafer 200 fixed to the head HD by the vacuum adsorption method can maintain the state where the entire one side is attached to the head HD. On the other hand, the donor substrate 300 having only an edge or a corner fixed to the stage ST is configured to be movable without being fixed to the stage ST, and the remaining portion can move along the wafer 200 and the head HD. When the wafer 200 and the donor substrate 300 are moved away from each other with the entire one side of the wafer 200 fixed to the head HD and only a part of the outermost portion of the donor substrate 300 fixed to the stage ST, the wafer 200 and the donor substrate 300 can be detached in a wire peeling form.

[0113] For example, when moving the wafer 200 and the head HD in the Z-axis direction with the right edge of the donor substrate 300 fixed to the stage ST, the remaining portion of the donor substrate 300 attached to the wafer 200 can float in the Z-axis direction along the wafer 200 and the head HD. When the wafer 200 and the head HD start to move in the Z-axis direction first, it can be peeled off from the wafer 200 earliest from the right edge of the donor substrate 300 that cannot float along the wafer 200. Then, as the head HD and the wafer 200 gradually move away from the donor substrate 300, it can be sequentially peeled off from the wafer 200 from a part of the donor substrate 300 adjacent to the right edge of the donor substrate 300. Finally, the left edge of the donor substrate 300 can be peeled off from the wafer 200, and the detachment of the wafer 200 and the donor substrate 300 can be completed. Therefore, the plurality of LEDs adhered to the plurality of chip protrusions 331 of the donor substrate 300 can be separated from the wafer 200 in line units.

[0114] On the other hand, the remaining portion of the donor substrate 300 that is not physically fixed to the stage ST can move along the wafer 200 and float from the stage ST during the detachment process, and can land on the stage ST when the detachment is completed. At this time, a vertical impact can be applied to the donor substrate 300 and the plurality of LEDs. However, since the plurality of LEDs adhered to the plurality of chip protrusions 331 of the donor substrate 300 are very strong against vertical impacts, the possibility of transfer failure of the plurality of LEDs is low even if the donor substrate 300 floats from the stage ST during the process.

[0115] Then, in order to reduce the interference between the dam DM of the wafer 200 and the LED disposed on the outermost periphery of the active region 200A during the wire peeling process, the distance between the dam DM and the LED can be formed to be greater than or equal to the distance from the outer periphery of one LED to the outer periphery of the adjacent LED. As described above, when the wafer 200 and the donor substrate 300 are detached, the plurality of LEDs can be separated from the wafer 200 in line units. At this time, if a sufficient distance is not ensured between the dam DM and the active region 200A, the outermost LED of the active region 200A transferred to the donor substrate 300 and the dam DM may interfere with each other during the process of being sequentially separated. If it is a surface peeling method in which the donor substrate 300 and the entire surface of the wafer 200 are separated at once, the outermost LED and the dam DM may not interfere with each other. However, in the LED transfer method according to an embodiment of the present invention and the manufacturing method of the display device 100 using the same, since the wafer 200 and the donor substrate 300 are detached by the wire peeling method, interference may occur between the outermost LED where the wire peeling finally progresses and the dam DM, which may lead to transfer defects of the plurality of LEDs. Therefore, a sufficient distance can be ensured between the dam DM in the outer peripheral region 200B of the wafer 200 and the plurality of LEDs in the active region 200A to reduce the interference between the dam DM and the plurality of LEDs when the wafer 200 and the donor substrate 300 are detached.

[0116] On the other hand, when fixing a part of the outermost part of the donor substrate 300 to the stage ST by a vacuum adsorption method instead of physically fixing it, it may be disadvantageous in terms of process time and yield. When partially vacuum-adsorbing the edge of the donor substrate 300, wire peeling may be possible. However, when increasing the desorption speed of the wafer 200 and the donor substrate 300, since the speed and the adhesive force are proportional, the adhesive force between the wafer 200 and the donor substrate 300 may increase, and it may become difficult to maintain a strong vacuum pressure sufficient to fix the donor substrate 300. Conversely, when decreasing the desorption speed of the wafer 200 and the donor substrate 300, the adhesive force becomes relatively low, and the untransferred defects of a plurality of LEDs may increase, and the process time may also increase. Therefore, when fixing the donor substrate 300 by a vacuum adsorption method, it is disadvantageous in terms of process time and transfer yield, so a part of the outermost part of the donor substrate 300 can be fixed to the stage ST in a physical manner.

[0117] Referring to FIG. 4F, after completing the primary transfer process, a plurality of LEDs can be arranged on the donor substrate 300. At this time, the plurality of LEDs arranged on the donor substrate 300 can be arranged radially around one LED' among the plurality of LEDs.

[0118] Specifically, one LED' among the plurality of LEDs can be arranged at the center of the chip protrusion 331 of the donor substrate 300. And the farther an LED is from one LED' and arranged around one LED', the farther it can be arranged from the center of the chip protrusion 331. For example, an LED adjacent to one LED' can be arranged adjacent to the center of the chip protrusion 331, and an LED far from one LED' can be arranged away from the center of the chip protrusion 331. For example, some LEDs arranged on the right side of one LED' can be arranged biased to the right from the center of the chip protrusion 331, and some LEDs arranged on the upper side of one LED' can be arranged biased upward from the center of the chip protrusion 331.

[0119] At this time, one LED' can vary depending on the portion of the donor substrate 300 fixed to the stage ST. For example, when the right edge of the donor substrate 300 is fixed to the stage ST, one LED may be one of the LEDs arranged in the left region from the center of the donor substrate 300. Specifically, when detaching the donor substrate 300 and the wafer 200, the greatest tension can act on the right edge of the donor substrate 300 physically fixed to the stage ST and the region adjacent to the right edge. That is, when detaching the donor substrate 300 and the wafer 200, the tension acting on the donor substrate 300 can vary depending on the fixed portion, and due to the change in tension, a plurality of LEDs can be radially transferred onto a plurality of chip protrusions 331. Therefore, when detaching the donor substrate 300 and the wafer 200 in a wire peeling form after physically fixing only one side end portion of the donor substrate 300, the plurality of LEDs arranged on the donor substrate 300 can be radially distributed.

[0120] Finally, referring to FIG. 4G, the secondary transfer process can be advanced to transfer the plurality of LEDs on the donor substrate 300 to the display panel PN to complete the manufacturing process of the display device 100. At this time, the display panel PN is a display panel PN on which a circuit for driving a plurality of LEDs, for example, a driving transistor 120 and a plurality of wirings are formed.

[0121] First, the donor substrate 300 with a plurality of LEDs arranged thereon and the display panel PN are loaded into the process equipment. Next, the donor substrate 300 and the display panel PN are aligned.

[0122] At this time, the donor substrate 300 and the display panel PN can be aligned based on the second alignment key AK2 transferred from the wafer 200 to the donor substrate 300 and the alignment key AK of the display panel PN. The plurality of LEDs and the second alignment key AK2 disposed on the donor substrate 300 are transferred in the same process. Therefore, the relative positions of the plurality of LEDs and the second alignment key AK2 can be constant. Therefore, when aligning the donor substrate 300 and the display panel PN with reference to the second alignment key AK2 whose relative position with respect to the plurality of LEDs is constant, the alignment accuracy for transferring the plurality of LEDs to a fixed position can be improved. Accordingly, when transferring the plurality of LEDs of the donor substrate 300 to the display panel PN, the donor substrate 300 and the display panel PN can be aligned with reference to the second alignment key AK2. However, in this specification, although it has been described that the donor substrate 300 and the display panel PN are aligned with reference to the second alignment key AK2, the donor substrate 300 and the display panel PN can also be aligned with reference to other components and are not limited thereto.

[0123] The alignment key AK of the display panel PN aligned with the second alignment key AK2 on the donor substrate 300 may be any one of the components formed on the display panel PN, or may be separately formed and disposed. For example, when the alignment key AK is any one of the components formed on the display panel PN, a reflective layer that overlaps with the plurality of LEDs among the components formed on the display panel PN, a part of the plurality of wirings arranged to drive the plurality of LEDs, etc. can also function as the alignment key AK. Further, when the alignment key AK is separately formed and disposed, the alignment key AK may be a pattern or structure formed on the display panel PN, but is not limited thereto.

[0124] Next, after the alignment of the donor substrate 300 and the display panel PN is completed, the donor substrate 300 and the display panel PN are bonded together (S140). Next, the plurality of LEDs are transferred to the display panel PN (S150). Then, after transferring the plurality of LEDs of the donor substrate 300 to the display panel PN, the donor substrate 300 and the display panel PN are detached (S160). In this case, the plurality of LEDs radially distributed on the donor substrate 300 can also be radially distributed after being transferred to the display panel PN.

[0125] At this time, the donor substrate 300 and the display panel PN may be detached by a wire peeling method as shown in FIG. 4E, or may be detached by other methods. For example, the donor substrate 300 and the display panel PN may be detached by a surface peeling method in which the entire surface is peeled off at once, and the detachment method of the donor substrate 300 and the display panel PN may be configured in various ways.

[0126] Therefore, the manufacturing process of the display device 100 can be completed through the steps of primarily transferring a plurality of LEDs from the wafer 200 to the donor substrate 300 and secondarily transferring the plurality of LEDs transferred to the donor substrate 300 to the display panel PN. On the other hand, a rigid substrate may be used as the donor substrate 300 in addition to the flexible substrate. For example, the donor substrate 300 may be made of a hard material instead of a material such as PDMS. However, when the donor substrate 300 is a rigid substrate, it is difficult to configure the donor substrate 300 over a large area due to thickness variations, and there is a problem of an increase in the number of transfer times. In contrast, when the donor substrate 300 is made of a flexible substrate, the area of the donor substrate 300 can be increased, and damage to the LEDs can be minimized. Therefore, a flexible substrate can be used as the donor substrate 300.

[0127] On the other hand, when the wafer 200 is detached from the donor substrate 300, which is a flexible substrate, by a surface peeling method, transfer defects of a plurality of LEDs may occur. For example, in order to detach the donor substrate 300 and the wafer 200 by a surface peeling method, the entire surface of the donor substrate 300 can be fixed to the stage ST, and the detachment process can proceed with the entire surface of the wafer 200 fixed to the head HD. At this time, when the donor substrate 300, which is a flexible substrate, is fixed to the stage ST by a vacuum suction method, a phenomenon in which wrinkles form on the donor substrate 300 may occur, and transfer defects of a plurality of LEDs may occur. In addition, the surface tension generated during surface peeling and the external force due to vacuum suction may affect the LEDs of a fine size, and the LEDs may be transferred in a flipped or tilted state, or may be transferred in a rotated state. Such transfer defects may occur randomly within the surface peeling region SA, which may lead to a decrease in yield and an increase in process cost.

[0128] In contrast, in the method for transferring LEDs according to an embodiment of the present invention, only one side end portion of the donor substrate 300, which is a flexible substrate, is physically fixed. Therefore, the external force due to vacuum suction is minimized, and since the donor substrate 300 is naturally peeled off from the wafer 200 even during the desorption process, the surface tension can be minimized. Specifically, one side end of the donor substrate 300, which is a flexible substrate, is physically fixed to the stage ST, and the wafer 200, which is a rigid substrate, can be fixed by vacuum suction to the head HD. Then, the donor substrate 300, the wafer 200, or both the donor substrate 300 and the wafer 200 are moved in a vertical direction to peel the donor substrate 300 from the wafer 200. At this time, one side end of the donor substrate 300 is physically fixed, and the remaining portion is not fixed. Therefore, the remaining portion of the donor substrate 300 can move together along the wafer 200. However, as the distance between the wafer 200 and the donor substrate 300 gradually increases, the wafer 200 can be sequentially separated from one side end portion of the donor substrate 300 fixed to the stage ST. Therefore, the external force affecting the plurality of LEDs during the desorption process of the donor substrate 300 and the wafer 200 can be reduced, and the transfer failure of the plurality of LEDs can be minimized. Accordingly, in the method for transferring LEDs according to an embodiment of the present invention and the method for manufacturing the display device 100 using the same, the wafer 200 and the donor substrate 300 can be desorbed by a line peeling method to reduce the transfer failure of the plurality of LEDs.

[0129] Further, in the method for transferring LEDs according to an embodiment of the present invention and the method for manufacturing the display device 100 using the same, the desorption speed of the wafer 200 and the donor substrate 300 can be increased to reduce the non-transfer failure of the plurality of LEDs. A substance such as PDMS forming the plurality of chip protrusions 331 of the donor substrate 300 has a characteristic that the adhesive force increases as the speed increases. Therefore, when increasing the desorption speed of the donor substrate 300 and the wafer 200, the adhesive force of the chip protrusions 331 can be increased to improve the adhesive force of the plurality of LEDs attached on the chip protrusions 331. Thus, the wafer 200 and the donor substrate 300 are desorbed by a high-speed line peeling method to reduce the non-transfer failure of the plurality of LEDs and at the same time minimize the situation where the plurality of LEDs are transferred while being turned over or tilted during the transfer process.

[0130] Hereinafter, with reference to FIGS. 5A to 6B, the LED transfer method according to an embodiment of the present invention is compared with the LED transfer method according to a comparative example. FIGS. 5A and 5B are schematic diagrams for explaining the transfer method according to Comparative Example 1. FIGS. 6A and 6B are schematic diagrams for explaining the transfer method according to Comparative Example 2. For convenience of explanation, in FIGS. 5B and 6B, only the base layer 310 and the resin layer 330 of the donor substrate 300 are shown.

[0131] The LED transfer method according to Comparative Example 1 is a transfer method in which the donor substrate 300 is fixed to the stage ST using both a fixing member GR and a vacuum suction method, and the donor substrate 300 and the wafer 200 are peeled off. The LED transfer method according to Comparative Example 2 is a transfer method in which only the fixing member GR is used to fix both sides of the donor substrate 300 to the stage ST, and the donor substrate 300 and the wafer 200 are peeled off.

[0132] First, referring to FIGS. 5A and 5B, in the LED transfer method according to Comparative Example 1, both side edges of the donor substrate 300 are fixed with a fixing member GR while the entire one surface of the donor substrate 300 is vacuum-sucked to the stage ST. Then, the entire one surface of the wafer 200 is fixed to the head HD by a vacuum suction method.

[0133] Next, the wafer 200 and the donor substrate 300 are moved in a direction away from each other so that the wafer 200 and the donor substrate 300 can be detached. At this time, since the entire one surface of the donor substrate 300 is fixed to the stage ST and the entire one surface of the wafer 200 is also fixed to the head HD, the donor substrate 300 and the wafer 200 can be peeled off by surface peeling. That is, the resin layer 330 of the donor substrate 300 can have the entire surface as a surface peeling region SA. Therefore, transfer defects of a plurality of LEDs can occur in the entire resin layer 330 in which a plurality of chip protrusions 331 of the donor substrate 300 are arranged.

[0134] Referring to FIGS. 6A and 6B, in the LED transfer method according to Comparative Example 2, only both side edges of the donor substrate 300 are fixed to the stage ST by the fixing member GR. Then, the entire one surface of the wafer 200 is fixed to the head HD by a vacuum suction method.

[0135] Next, the wafer 200 and the donor substrate 300 are moved in a direction away from each other so that the wafer 200 and the donor substrate 300 can be detached. At this time, since only both side edges of the donor substrate 300 are fixed to the stage ST and the entire one surface of the wafer 200 is fixed to the head HD, it can be detached by a wire peeling method from both side edges of the donor substrate 300 to a part of the inner region of the donor substrate 300. However, the central region of the donor substrate 300 that is finally detached can be detached from the wafer 200 by a surface peeling method. Therefore, in the resin layer 330 in which a plurality of chip protrusions 331 are arranged, a part of the region extending from both side edges can be a wire peeling region LA, and the remaining intermediate region can be a surface peeling region SA.

[0136] Therefore, in the LED transfer methods according to Comparative Example 1 and Comparative Example 2, at least a part of the donor substrate 300 can become a surface peeling region SA, and the probability of transfer failure of a plurality of LEDs generated in the surface peeling region SA can increase. That is, compared with the LED transfer method according to an embodiment of the present invention, which is a wire peeling method, in the LED transfer methods according to Comparative Example 1 and Comparative Example 2, the surface peeling region SA of the donor substrate 300 increases, which may be disadvantageous in terms of yield. Therefore, in the LED transfer method according to an embodiment of the present invention, only one end portion of the donor substrate 300, which is a flexible substrate, is physically fixed to the stage ST, and the stage ST and / or the head HD are moved with the one surface of the wafer 200 vacuum-sucked to the head HD, so that the entire region of the donor substrate 300 can become a wire peeling region LA, and transfer failure of a plurality of LEDs can be reduced.

[0137] Embodiments of the present invention can also be described as follows.

[0138] According to an aspect of the present invention, a method for transferring LEDs includes a step of attaching a rigid substrate on which a plurality of LEDs are formed and a flexible substrate, a step of transferring the plurality of LEDs to the flexible substrate, and a step of detaching the rigid substrate and the flexible substrate. The step of detaching the rigid substrate and the flexible substrate includes a step of fixing one surface of the rigid substrate and separating the rigid substrate and the flexible substrate in a state where a part of the outermost portion of the flexible substrate is fixed by a fixing member.

[0139] The step of detaching the rigid substrate and the flexible substrate can further include a step of loading the rigid substrate and the flexible substrate in the attached state onto a stage.

[0140] The step of detaching the rigid substrate and the flexible substrate further includes a step of fixing one edge of the plurality of edges of the flexible substrate to the stage with a fixing member, and the remaining portion of the flexible substrate can be configured to be movable on the stage.

[0141] The step of detaching the rigid substrate and the flexible substrate further includes a step of fixing at least one corner of the plurality of corners of the flexible substrate to the stage with a fixing member, and the remaining portion of the flexible substrate can be configured to be movable on the stage.

[0142] The step of detaching the rigid substrate and the flexible substrate can further include a step of moving the rigid substrate, the flexible substrate, or the rigid substrate and the flexible substrate in a direction perpendicular to one surface of the stage.

[0143] According to still another feature of the present invention, the step of detaching the rigid substrate and the flexible substrate may be a step of peeling the rigid substrate and the flexible substrate linearly.

[0144] The plurality of LEDs arranged on the flexible substrate are arranged radially around one of the plurality of LEDs, and one LED can be separated from the center of the flexible substrate.

[0145] According to another aspect of the present invention, a method for manufacturing a display device includes steps of attaching a wafer and a donor substrate, transferring a plurality of LEDs on the wafer to the donor substrate, detaching the wafer and the donor substrate, attaching the donor substrate on which the plurality of LEDs are disposed and a display panel, transferring the plurality of LEDs on the donor substrate to the display panel, and detaching the display panel and the donor substrate. The step of detaching the wafer and the donor substrate includes a step of fixing one surface of the wafer to a head and detaching the wafer and the donor substrate in a state where a part of the outermost contour portion of the donor substrate is fixed to a stage.

[0146] The wafer and the display panel may be rigid substrates, and the donor substrate may be a flexible substrate.

[0147] The step of detaching the wafer and the donor substrate may further include a step of fixing one edge of the outermost contour portion of the donor substrate to the stage with a gripper.

[0148] The step of detaching the wafer and the donor substrate may further include a step of fixing at least one or more corners of the outermost contour portion of the donor substrate to the stage with a gripper.

[0149] The step of detaching the wafer and the donor substrate may further include a step of fixing one surface of the wafer to the head by vacuum suction or a fixing member.

[0150] The step of detaching the wafer and the donor substrate may further include a step of moving the head, the stage, or the head and the stage in the Z-axis direction. When moving the head, the stage, or the head and the stage in the Z-axis direction, the plurality of LEDs on the donor substrate may be separated from the wafer in line units.

[0151] When moving the head, the stage, or the head and the stage in the Z-axis direction, at least a part of the donor substrate may be separated from the stage.

[0152] The wafer includes an active region in which a plurality of LEDs are formed and an outer peripheral region in which one or more dams are formed, and the distance between the LED disposed at the outermost periphery of the active region and the dam among the plurality of LEDs may be equal to or greater than the distance from the outer periphery of one LED to the outer periphery of the adjacent LED among the plurality of LEDs.

[0153] The donor substrate includes chip protrusions to which each of the plurality of LEDs adheres. One of the plurality of LEDs transferred to the donor substrate is disposed at the center of the chip protrusion, and another one of the plurality of LEDs disposed on one side of one of the LEDs transferred to the donor substrate may be disposed offset to one side from the center of the chip protrusion.

[0154] As described above, the embodiments of the present invention have been described in more detail with reference to the accompanying drawings. However, the present invention is not necessarily limited to such embodiments, and various modifications can be made within the scope not departing from the technical idea of the present invention. Therefore, the embodiments disclosed in the present invention are not for limiting the technical idea of the present invention, but for explaining it, and the scope of the technical idea of the present invention is not limited by such embodiments. Therefore, it should be understood that the embodiments described above are exemplary in all aspects and not restrictive. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

Claims

1. A wafer comprising: a substrate including an active region and an outer peripheral region; a plurality of light emitting diodes arranged at regular intervals in the active region and configured to emit light of the same color; a plurality of dams arranged in the outer peripheral region and formed at the same height as the plurality of light emitting diodes; a first alignment key arranged in the outer peripheral region and having a metal pattern; and a second alignment key arranged in the outer peripheral region. The substrate is made of any one of sapphire, silicon carbide (SiC), gallium nitride (GaN), and zinc oxide (ZnO). The first alignment key and the second alignment key are made of the same material as at least a part of the material constituting the plurality of light emitting diodes. The plurality of dams are arranged between the active region and the second alignment key.

2. The wafer according to claim 1, wherein the first alignment key is placed in any one of a region between the plurality of dams, an upper part of the plurality of dams, and a lower part of the plurality of dams, and the second alignment key is arranged away from the plurality of dams.

3. The wafer according to claim 1, wherein the second alignment key and the plurality of light emitting diodes are configured to be removable from the substrate.

4. The wafer according to claim 1, wherein the first alignment key and the second alignment key have different shapes or sizes.

5. The wafer according to claim 1, wherein a minimum width of each of the plurality of dams is larger than a distance between the plurality of light emitting diodes.

6. The wafer according to claim 1, wherein a distance between a dam closest to the active region among the plurality of dams and an outermost light emitting diode among the plurality of light emitting diodes is the same as or larger than a distance between the plurality of light emitting diodes.

7. The wafer according to claim 1, wherein the plurality of dams are arranged adjacent to each of four sides of the active region.

8. A donor substrate for transferring the plurality of light emitting diodes by being attached to the wafer according to claim 1, the donor substrate comprising: a base layer; an adhesive layer disposed on the base layer; a resin layer disposed on the adhesive layer and having a transfer region and a non-transfer region; a plurality of chip protrusions disposed in the transfer region; a plurality of alignment protrusions disposed in the non-transfer region; and a plurality of dam protrusions disposed in the non-transfer region and surrounding the transfer region. ​ The plurality of alignment protrusions are a plurality of first alignment protrusions, and a plurality of second alignment protrusions having a shape different from that of the plurality of first alignment protrusions and include when the wafer and the donor substrate are joined, the first alignment protrusion corresponds to the first alignment key, and the second alignment protrusion corresponds to the second alignment key, donor substrate. **Claim 9** The donor substrate according to claim 8, wherein the base layer is made of a material that is at least harder than the resin layer. **Claim 10** The donor substrate according to claim 8, wherein the plurality of chip protrusions, the plurality of alignment protrusions, and the plurality of dam protrusions are formed integrally with the resin layer. **Claim 11** The donor substrate according to claim 10, wherein the resin layer, the plurality of chip protrusions, the plurality of alignment protrusions, and the plurality of dam protrusions are made of any one of polydimethylsiloxane (PSMS), polyurethane acrylate (PUA), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), polystyrene (PS), epoxy resin, urethane resin, and acrylic resin. **Claim 12** The donor substrate according to claim 8, wherein the size of each of the plurality of dam protrusions is larger than the size of each of the plurality of chip protrusions.

Images