Transfer substrate and micro LED transfer method using same

Abstract

A transfer substrate and a micro LED transfer method using same are disclosed. The transfer substrate comprises: a light-transmitting substrate; and a thin film laminated on one surface of the light-transmitting substrate and having a plurality of micro LEDs attached thereto, wherein blisters are formed on the thin film by a UV laser so as to be used in a laser blister transfer method.

Description

Transfer substrate and micro LED transfer method using the same

[0001] The present disclosure relates to a transfer substrate and a micro LED transfer method using the same.

[0002] Micro LEDs, measuring less than 100㎛ in size and capable of converting electrical signals into optical signals, offer faster response times, lower power consumption, lighter weight, thinner form factor, and higher efficiency than conventional LEDs. Displays featuring micro LEDs offer superior image quality and reliability compared to liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays.

[0003] Micro LEDs formed on a wafer undergo multiple transfer processes and are transferred from multiple transfer substrates to a target substrate (e.g., a display substrate). The spacing between the multiple micro LEDs arranged on the transfer substrate is smaller than the size of the micro LEDs themselves. The multiple micro LEDs arranged at fine intervals on the transfer substrate are then transferred to another transfer substrate or target substrate using a laser ablation transfer method that enables precise transfer.

[0004] A transfer substrate is provided with a laser ablation layer and an adhesive layer laminated on the laser ablation layer. The laser ablation layer is vaporized and removed by a laser irradiated on the transfer substrate. The adhesive layer has adhesive properties to attach a plurality of micro LEDs to the transfer substrate. Through the transfer process, a plurality of micro LEDs on the wafer are transferred to the transfer substrate. The plurality of micro LEDs are arranged at a constant pitch on the adhesive layer. Before transferring the plurality of micro LEDs on the transfer substrate to another transfer substrate, a descum process is performed to remove a portion of the adhesive layer remaining on the surface of the micro LED (including the light-emitting surface of the micro LED) by dry etching.

[0005] However, there was a problem that the pad of the micro LED was damaged due to the descum process, and even though the descum process was performed, the residue on the surface of the micro LED was not completely removed, resulting in a problem of PL (photoluminescence) defects during micro LED testing.

[0006] The present disclosure relates to a transfer substrate capable of omitting a discom process and a micro LED transfer method using the transfer substrate.

[0007] A transfer substrate according to one or more embodiments may include a light-transmitting substrate; and a thin film laminated on one surface of the light-transmitting substrate and having a plurality of micro light emitting diodes (LEDs) attached thereto. The thin film may be bubble-formed by a UV laser for use in a laser blister transfer method.

[0008] The UV laser irradiated onto the above transparent substrate and the above thin film may have a short wavelength range of 190 nm to 360 nm.

[0009] The short wavelength of the above UV laser may be one of 193 nm, 248 nm, 266 nm, 308 nm and 355 nm.

[0010] The above thin film may include a polyimide-based mixed material.

[0011] The above thin film may have a thickness range of 3㎛ to 20㎛.

[0012] The above thin film may include a laser blister layer laminated on one surface of the light-transmitting substrate; and an adhesive layer laminated on the laser blister layer.

[0013] The above laser blister layer may include a polyimide-based material.

[0014] The above laser blister layer may have a thickness range of 0.01 μm to 1 μm.

[0015] The above adhesive layer may include a polydimethylsiloxane (PDMS)-based material.

[0016] The above adhesive layer may have a thickness range of 1 μm to 5 μm.

[0017] A micro LED transfer method according to one or more embodiments may include the steps of: transferring a plurality of micro LEDs from a wafer to a first transfer substrate; irradiating the first transfer substrate with a UV laser to transfer the plurality of micro LEDs from the first transfer substrate to a second transfer substrate by a laser blister transfer method; and irradiating the second transfer substrate with a UV laser to transfer the plurality of micro LEDs from the second transfer substrate to a target substrate by a laser blister transfer method. The UV laser used in the laser blister transfer method may have a short wavelength range of 190 nm to 360 nm.

[0018] The short wavelength of the UV laser used in the above laser blister transfer method may be one of 193 nm, 248 nm, 266 nm, 308 nm and 355 nm.

[0019] Each of the first thin film applied to the first transfer substrate and the second thin film applied to the second transfer substrate, to which the plurality of micro LEDs are attached and which generate bubbles in response to the UV laser, may have a thickness range of 3 μm to 20 μm.

[0020] Each of the first thin film applied to the first transfer substrate and the second thin film applied to the second transfer substrate may include a first layer that generates bubbles in response to the UV laser; and a second layer laminated on the first layer and to which the plurality of micro LEDs are attached. The first layer may swell while generating bubbles in response to the UV laser. The second layer may be deformed together with the first layer to move the plurality of micro LEDs to a transfer position.

[0021] The first layer may have a thickness range of 0.01 μm to 1 μm. The second layer may have a thickness range of 1 μm to 5 μm.

[0022] FIG. 1 is a block diagram illustrating a display device according to one or more embodiments.

[0023] FIG. 2 is a diagram illustrating a display module according to one or more embodiments.

[0024] FIG. 3 is a cross-sectional view illustrating a portion of a display module according to one or more embodiments.

[0025] FIG. 4 is a drawing showing a transfer substrate according to one or more embodiments.

[0026] FIG. 5 is a flowchart illustrating a micro LED transfer method according to one or more embodiments.

[0027] FIGS. 6 and 7 are drawings illustrating examples of transferring a plurality of micro LEDs from a wafer to a first transfer substrate according to one or more embodiments.

[0028] FIGS. 8 and 9 are drawings illustrating examples of transferring a plurality of micro LEDs from a first transfer substrate to a second transfer substrate according to one or more embodiments.

[0029] FIGS. 10 and 11 are drawings illustrating examples of transferring a plurality of micro LEDs from a second transfer substrate to a target substrate according to one or more embodiments.

[0030] FIG. 12 is a diagram illustrating an example of thermally compressing a plurality of micro LEDs transferred to a target substrate according to one or more embodiments.

[0031] FIG. 13 is a drawing showing a transfer substrate according to one or more embodiments.

[0032] Hereinafter, various embodiments will be described in more detail with reference to the accompanying drawings. One or more embodiments described herein may be variously modified. Specific embodiments may be depicted in the drawings and further described in the detailed description. However, the specific embodiments disclosed in the accompanying drawings are merely intended to facilitate understanding of various embodiments. Therefore, the technical concepts disclosed in the accompanying drawings are not intended to be limited by the specific embodiments disclosed in the accompanying drawings, but should be understood to include all equivalents or alternatives falling within the spirit and technical scope of the present disclosure.

[0033] In this disclosure, terms including ordinal numbers such as "first," "second," etc. may be used to describe various components, but these components are not limited by the aforementioned terms. The aforementioned terms are used solely for the purpose of distinguishing one component from another. In this disclosure, terms such as "comprises" or "has" should be understood to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preemptively exclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to the other component, but that other components may also be present in between. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there are no other components present in between. In this disclosure, the term "same" may encompass not only complete matching but also differences that take into account the scope of processing errors. If a detailed description of a related known function or configuration is deemed likely to unnecessarily obscure the gist of this disclosure, the detailed description will be abbreviated or omitted.

[0034] Below, with reference to the attached drawings, an embodiment of the present disclosure is described in detail so that those skilled in the art can easily implement the present disclosure. However, the embodiment of the present disclosure may be implemented in various different forms and is not limited to the embodiment of the present disclosure described herein.

[0035] FIG. 1 is a block diagram illustrating a display device according to one or more embodiments.

[0036] Referring to FIG. 1, a display device (1) may include a display module (3) and a processor (4). The display module (3) may include a substrate (10) and a display driver integrated circuit (IC) (7) for controlling the driving of a plurality of micro LEDs provided on the substrate (10). In the present disclosure, the substrate (10) may be referred to as a 'target substrate'. The target substrate may mean a substrate that serves as a target for transferring a plurality of micro LEDs from a transfer substrate during the process of manufacturing the display module (3).

[0037] The processor (4) may be implemented as a digital signal processor (DSP), a microprocessor, a graphics processing unit (GPU), an artificial intelligence (AI) processor, a neural processing unit (NPU), or a time controller (TCON) that processes a digital image signal. However, the present invention is not limited thereto, and may include one or more of a central processing unit (CPU), a micro controller unit (MCU), a micro processing unit (MPU), a controller, an application processor (AP), a communication processor (CP), or an ARM processor, or may be defined by the relevant terminology. In addition, the processor (4) may be implemented as a system on chip (SoC) or large scale integration (LSI) having a built-in processing algorithm, or may be implemented in the form of an application specific integrated circuit (ASIC), or a field programmable gate array (FPGA).

[0038] The processor (4) can control hardware or software components connected to the processor (4) by running an operating system or application program, and can perform various data processing and calculations. In addition, the processor (4) can load commands or data received from at least one of the other components into volatile memory and process them, and store various data in non-volatile memory.

[0039] The display driver IC (7) may include an interface module (7a), a memory (7b) (e.g., a buffer memory), an image processing module (7c), or a mapping module (7d). The display driver IC (7) may receive, for example, image information including image data or an image control signal corresponding to a command for controlling the image data, from another component of the display device (1) through the interface module (7a). For example, according to one embodiment, the image information may be received from a processor (4) (e.g., a main processor (e.g., an application processor) or an auxiliary processor (e.g., a graphics processing unit) that operates independently of the function of the main processor).

[0040] The display driver IC (7) can communicate with the sensor module through the interface module (7a). In addition, the display driver IC (7) can store at least a part of the received image information in the memory (7b), for example, on a frame basis. The image processing module (7c) can, for example, perform preprocessing or postprocessing (e.g., resolution, brightness, or size adjustment) on at least a part of the image data based on at least the characteristics of the image data or the characteristics of the substrate (10). The mapping module (7d) can generate a voltage value or a current value corresponding to the image data preprocessed or postprocessed through the image processing module (7c). According to one embodiment, the generation of the voltage value or the current value can be performed based at least in part on, for example, the properties of the pixels of the substrate (10) (e.g., the arrangement of the pixels (RGB stripe or pentile structure), or the size of each subpixel). At least some pixels of the substrate (10) may be driven based at least in part on, for example, the voltage value or current value, so that visual information (e.g., text, an image, or an icon) corresponding to the image data may be displayed through the substrate (10).

[0041] The display driver IC (7) can transmit a driving signal (e.g., a driver driving signal, a gate driving signal, etc.) to the display based on image information received from the processor (4).

[0042] The display driver IC (7) can display an image based on an image signal received from the processor (4). For example, the display driver IC (7) can display an image by generating a driving signal for a plurality of sub-pixels based on the image signal received from the processor (4) and controlling the light emission of the plurality of sub-pixels based on the driving signal.

[0043] According to one or more embodiments, the display module (3) may further include a touch circuit. The touch circuit may include a touch sensor and a touch sensor IC for controlling the same. The touch sensor IC may control the touch sensor to detect, for example, a touch input or a hovering input with respect to a designated location of the substrate (10). For example, the touch sensor IC may detect the touch input or the hovering input by measuring a change in a signal (e.g., voltage, light quantity, resistance, or charge quantity) with respect to the designated location of the substrate (10). The touch sensor IC may provide information (e.g., location, area, pressure, or time) about the detected touch input or hovering input to the processor (4). According to one embodiment, at least a portion of the touch circuit (e.g., the touch sensor IC) may be included as a part of the display driver IC (7), or as a part of the substrate (10), or as a part of another component (e.g., an auxiliary processor) disposed externally to the display module (3).

[0044] According to one or more embodiments, the pixel driving method of the display module (3) may be an AM (active matrix) driving method or a PM (passive matrix) driving method.

[0045] According to one or more embodiments, the display device (1) may include a display module (3). The display module (3) may display various images. Here, the images may include still images and / or moving images. The display module (3) may display various images, such as broadcast content, multimedia content, etc. In addition, the display module (3) may also display a user interface and icons.

[0046] According to one or more embodiments, the display module (3) can be installed and applied in a wearable device, a portable device, a handheld device, and various electronic products or battlefields requiring a display.

[0047] According to one or more embodiments, the display device (1) may include a plurality of display modules (3). The plurality of display modules (3) may be physically connected to implement a large display (e.g., a large format display). The large display may be a monitor for a personal computer, a high-resolution television, signage (or digital signage), or an electronic display by connecting the plurality of display modules (3) in a grid arrangement.

[0048] FIG. 2 is a diagram illustrating a display module according to one or more embodiments. FIG. 3 is a cross-sectional view illustrating a portion of a display module according to one or more embodiments.

[0049] Referring to FIGS. 2 and 3, the display module (3) may include a substrate (10) and a plurality of micro LEDs arranged on the substrate (10). The plurality of micro LEDs may include a first micro LED (100) that emits red light, a second micro LED (200) that emits green light, and a third micro LED (300) that emits blue light. In this case, the first micro LED (100), the second micro LED (200), and the third micro LED (300) may form one pixel. Each micro LED may be referred to as a sub-pixel. The substrate (10) may be provided with a plurality of pixel areas (10a) in a roughly grid shape. One pixel may be provided in each pixel area.

[0050] A substrate (10) may have TFT circuits (thin film transistor circuits) provided on the front surface of the substrate (10) on which a plurality of pixel areas (10a) are provided. A power supply circuit for supplying power to the TFT circuit, a data driving driver, a gate driving driver, and a timing controller for controlling each driving driver may be provided on the back surface of the substrate (10).

[0051] The TFT circuit may include a plurality of TFTs for driving the first, second, and third micro LEDs (100, 200, 300). The TFT circuit may be formed on the front surface of the substrate (10), but is not limited thereto, and may be manufactured in the form of a separate film and laminated to the front surface of the substrate (10). A plurality of substrate pads (11, 12, 13, 14, 15, 16) arranged in the TFT circuit may be electrically connected to the TFTs of the TFT circuit.

[0052] Many TFTs are not limited to a specific structure or type. For example, TFTs can be implemented as LTPS TFTs (low-temperature polycrystalline silicon TFTs), oxide TFTs, Si TFTs (poly silicon, a-silicon), organic TFTs, graphene TFTs, etc. A TFT circuit can only include P-type (or N-type) MOSFETs (metal oxide semiconductor field effect transistors) in a CMOS (complementary metal oxide semiconductor) process on a Si wafer.

[0053] A plurality of contact electrodes (101, 102, 201, 202, 301, 302) provided on each of the first, second, and third micro LEDs (100, 200, 300) and a plurality of substrate pads (11, 12, 13, 14, 15, 16) of the substrate (10) can be electrically and physically interconnected by a conductive adhesive member (20). The conductive adhesive member (20) can be an anisotropic conductive film or an anisotropic conductive paste.

[0054] The first, second, and third micro LEDs (100, 200, 300) may each include a light-emitting surface (105, 205, 305) from which light is emitted. A plurality of micro LEDs (100, 200, 300) may be formed in a flip chip form in which a plurality of contact electrodes (101, 102, 201, 202, 301, 302) are provided on the opposite side of the light-emitting surface (105, 205, 305).

[0055] Hereinafter, with reference to the drawings, a transfer substrate according to one or more embodiments and a transfer method of a micro LED using the same are described.

[0056] In the present disclosure, 'transfer' may refer to a series of operations of separating a plurality of micro LEDs formed on a wafer from the wafer and transferring them onto a first transfer substrate, transferring the plurality of micro LEDs on the first transfer substrate onto a second transfer substrate, and moving the plurality of micro LEDs on the second transfer substrate onto a target substrate (e.g., a substrate forming a display module). The wafer may have an epitaxial layer formed thereon having a single-crystal structure made by growing silicon (Si), gallium arsenide (GaAs), or the like. The transfer substrate may be referred to as an 'interposer', a 'relay substrate', a 'carrier substrate', or a 'temporary substrate'. The micro LED may be referred to as a 'micro light-emitting chip' or a 'micro light-emitting device'.

[0057] FIG. 4 is a cross-sectional view illustrating a transfer substrate used in manufacturing a display module according to one or more embodiments.

[0058] Referring to FIG. 4, a transfer substrate (50) may be provided with a thin film (51) on one surface. The thin film (51) may include a laser active layer (52) formed with a predetermined thickness on one surface of the transfer substrate (50) and an adhesive layer (53) laminated with a predetermined thickness on the laser blister layer (52).

[0059] The transfer substrate (50) may be a light-transmitting substrate. For example, the transfer substrate (50) may be a glass substrate. Alternatively, according to one or more other exemplary embodiments, the transfer substrate (50) may be a heat-resistant substrate that improves deformation of the transfer substrate (50) due to high temperature heat applied to the transfer substrate (50) when heating the laser blister layer (52) with a laser.

[0060] In the present disclosure, a laser blister transfer method can be applied as a transfer method. The laser blister layer (52) can have a predetermined material and a predetermined thickness so as to maintain transfer precision and transfer speed through the laser blister transfer method, and can use a UV laser (ultra violet laser). For example, the laser blister layer (52) can be made of a polyimide-based material. In this case, the laser blister layer (52) can have a thickness range of 0.01 μm to 1 μm. The UV laser (L2, see FIG. 8) irradiated to the laser blister layer (52) can be a short-wavelength laser to improve damage to a plurality of micro LEDs transferred from a first transfer substrate to a second transfer substrate or from the second transfer substrate to a target substrate by the laser. The UV laser can have a wavelength range of 190 nm to 360 nm, which is a short-wavelength region. The short wavelength of the UV laser can be one of 193 nm, 248 nm, 266 nm, 308 nm and 355 nm.

[0061] The adhesive layer (53) may be configured to attach a plurality of micro LEDs to the transfer substrate (50) by adhesive force. The adhesive layer (53) may have a thickness range of 1 μm to 5 μm so that it can be deformed together with the laser blister layer (52) when the laser blister layer (52) swells toward the outside of the transfer substrate (50) in response to the UV laser (L2).

[0062] The adhesive layer (53) may be a polydimethylsiloxane (PDMS)-based material having adhesiveness and elasticity so that a plurality of micro LEDs (100, 200, 300) arranged on the transfer substrate (50) can be detachably attached.

[0063] Alternatively, the adhesive layer (53) may be a resin-based material, a rubber-based material, or a mixed material. The resin-based material may be a thermosetting material (e.g., urea-based, melanin-based, phenol-based, unsaturated polyester-based, epoxy-based, resorcinol-based, or furan-based) or a thermoplastic material (e.g., vinyl acetate, polyvinyl alcohol-based, vinyl chloride-based, polyvinylacetyl-based, acrylic-based, saturated polyester-based, polyamide-based, or polyethylene-based). The rubber-based material may be, for example, butadiene-based, nitrile-based, butyl-based, silicone-based, polychloroprene-based, or ethyl-based. The mixed material may be, for example, phenolic vinyl-based, phenolic chloroprene-based, phenolic nitrile-based, epoxy polyamide-based, or natrile rubber-epoxy-based.

[0064] A process for transferring a plurality of micro LEDs using a transfer substrate according to one embodiment of the present disclosure is described.

[0065] FIG. 5 is a flowchart illustrating a micro LED transfer method according to one or more embodiments. FIGS. 6 and 7 are drawings illustrating examples of transferring a plurality of micro LEDs from a wafer to a first transfer substrate according to one or more embodiments. The 'first transfer substrate' described below is substantially the same as the transfer substrate (50) illustrated in FIG. 3, and for convenience, is given the same reference numeral 50 as the transfer substrate (50).

[0066] Referring to FIG. 6, a first transfer substrate (50) may be placed on the lower side of a wafer (40) on which a plurality of micro LEDs (100, 200, 300) are arranged. Each contact electrode (101, 102, 201, 202, 301, 302) of the plurality of micro LEDs (100, 200, 300) arranged on the wafer (40) may face the adhesive layer (53) of the first transfer substrate (50). In this state, a laser (L1) is irradiated to a preset point of the wafer (40) (e.g., a point where the first micro LED (100) is positioned).

[0067] Referring to FIG. 7, the first micro LED (100) is separated from the buffer layer (41) of the wafer (40) and transferred to the first transfer substrate (50). The contact electrodes (101, 102) of the first micro LED (100) can be attached on the adhesive layer (53) of the first transfer substrate (50).

[0068] Next, a laser (L1) is irradiated to a preset point on the wafer (40) (e.g., a point where the second micro LED (200) is positioned). The second micro LED (200) is separated from the buffer layer (41) of the wafer (40) and transferred to the first transfer substrate (50). The second micro LED (200) may be transferred to a location adjacent to the first micro LED (100) on the first transfer substrate (50).

[0069] In the present disclosure, a laser (L1) is irradiated onto a wafer (40) to sequentially transfer the remaining micro LEDs of the wafer (40) to a first transfer substrate (50) (configuration (501) of FIG. 5).

[0070] FIGS. 8 and 9 are drawings illustrating examples of transferring a plurality of micro LEDs from a first transfer substrate to a second transfer substrate according to one or more embodiments.

[0071] The second transfer substrate (60) may have substantially the same configuration as the first transfer substrate (50). For example, the second transfer substrate (60) may be a light-transmitting substrate. The second transfer substrate (60) may have a thin film (61) provided on one surface thereof that is identical to the thin film (51) of the first transfer substrate (50). The thin film (61) of the second transfer substrate (60) may include a laser blister layer (62) and an adhesive layer (63).

[0072] Referring to Fig. 8, a second transfer substrate (60) can be placed on the lower side of a first transfer substrate (50). Each light-emitting surface (105, 205, 305) of a plurality of micro LEDs (100, 200, 300) of the first transfer substrate (50) can face the adhesive layer (63) of the second transfer substrate (60). In this state, a UV laser (L2) is irradiated to a preset point (e.g., a point where the first, second, and third micro LEDs (100, 200, 300) are positioned) of the first transfer substrate (50). In this case, the UV laser (L2) may have a wavelength range of 190 nm to 360 nm, which is a short wavelength region, so as to improve damage to the first, second, and third micro LEDs (100, 200, 300). The short wavelength of the UV laser can be one of 193 nm, 248 nm, 266 nm, 308 nm and 355 nm.

[0073] Referring to FIG. 9, a portion (52a) of the laser blister layer (52) provided on the first transfer substrate (50) at the point where the UV laser (L2) is irradiated reacts with the UV laser (L2) to generate bubbles between the first transfer substrate (50) and the laser blister layer (52). A cavity (55) is formed between the first transfer substrate (50) and the laser blister layer (52) by the bubbles. Accordingly, a portion (52a) of the laser blister layer (52) and a portion (53a) of the corresponding adhesive layer (53) swell toward the second transfer substrate (60).

[0074] The first, second, and third micro LEDs (100, 200, 300) move toward the second transfer substrate (60) while attached to the adhesive layer (53). The first, second, and third micro LEDs (100, 200, 300) can be attached to the adhesive layer (63) of the second transfer substrate (60) by the force of swelling of a portion (52a) of the laser blister layer (52) and a portion (53a) of the adhesive layer (53) due to the bubbles.

[0075] In the present disclosure, a plurality of micro LEDs are transferred from a first transfer substrate (50) to a second transfer substrate (60) in pixel units (R / G / B micro LEDs). However, this is not limited thereto, and a plurality of micro LEDs arranged on the first transfer substrate (50) may be transferred one by one, or two or more micro LEDs arranged at specific locations on the first transfer substrate (50) may be transferred to the second transfer substrate (60).

[0076] In the present disclosure, the remaining micro LEDs of the first transfer substrate (50) are sequentially transferred to the second transfer substrate (60) through a laser blister transfer method (configuration (502) of FIG. 5).

[0077] In the present disclosure, a transfer process is performed using a laser blister transfer method while the first transfer substrate (50) and the second transfer substrate (60) are positioned to maintain a predetermined distance, i.e., while maintaining a non-contact state. In the transfer process, transfer can be performed while moving the second transfer substrate (60) at a constant speed. Alternatively, in the transfer process, laser blister transfer can be performed while simultaneously moving the first transfer substrate (50) and the second transfer substrate (60) at the same speed or at different speeds. Accordingly, the transfer method according to one or more examples can improve the work speed compared to the transfer method of the prior art, i.e., the transfer method in which laser transfer is performed while the transfer substrate and the target substrate (or another transfer substrate) maintain a contact state.

[0078] FIGS. 10 and 11 are drawings illustrating examples of transferring a plurality of micro LEDs from a second transfer substrate to a target substrate according to one or more embodiments.

[0079] Referring to Fig. 10, a target substrate (10) can be placed on the lower side of a second transfer substrate (60). Each contact electrode (101, 102, 201, 202, 301, 302) of a plurality of micro LEDs (100, 200, 300) of the second transfer substrate (60) can face a conductive adhesive member (20) of the target substrate (10). The conductive adhesive member (20) can cover a plurality of substrate pads (11, 12, 13, 14, 15, 16) of the target substrate (10) in the form of a thin film.

[0080] The target substrate (10) refers to a substrate included in the display module (3). A number of substrate pads (11, 12, 13, 14, 15, 16) are provided on the target substrate (10).

[0081] The target substrate (10) can be aligned to the second transfer substrate (60). Accordingly, a plurality of substrate pads (11, 12, 13, 14, 15, 16) of the target substrate (10) can be arranged to correspond to each contact electrode (101, 102, 201, 202, 301, 302) of a plurality of micro LEDs (100, 200, 300) of the second transfer substrate (60).

[0082] A UV laser (L2) is irradiated to a preset point (e.g., a point where the first, second, and third micro LEDs (100, 200, and 300) are positioned) of the second transfer substrate (60). In this case, the UV laser (L2) may have a wavelength range of 190 nm to 360 nm, which is a short wavelength region, so as to improve damage to the first, second, and third micro LEDs (100, 200, and 300). The short wavelength of the UV laser may be one of 193 nm, 248 nm, 266 nm, 308 nm, and 355 nm.

[0083] Referring to Fig. 11, a portion (62a) of the laser blister layer (62) provided on the second transfer substrate (60) at the point where the UV laser (L2) is irradiated reacts with the UV laser (L2) to generate bubbles between the second transfer substrate (60) and the laser blister layer (62). A cavity (65) is formed between the second transfer substrate (60) and the laser blister layer (62) by the bubbles. Accordingly, a portion (62a) of the laser blister layer (62) and a portion (63a) of the corresponding adhesive layer (63) swell toward the target substrate (10).

[0084] The first, second, and third micro LEDs (100, 200, 300) move toward the target substrate (10) while being attached to the adhesive layer (63). The first, second, and third micro LEDs (100, 200, 300) can be attached to the conductive adhesive member (20) of the target substrate (10) by the force of swelling of a part (62a) of the laser blister layer (62) and a part (63a) of the adhesive layer (63) by the bubbles.

[0085] In the present disclosure, a plurality of micro LEDs are transferred from a second transfer substrate (60) to a target substrate (10) in pixel units (R / G / B micro LEDs). However, this is not limited thereto, and a plurality of micro LEDs arranged on the second transfer substrate (60) may be transferred one by one, or two or more micro LEDs arranged at specific locations on the second transfer substrate (60) may be transferred to the target substrate (10).

[0086] In the present disclosure, the remaining micro LEDs of the second transfer substrate (60) are sequentially transferred to the target substrate (10) through a laser blister transfer method (configuration (503) of FIG. 5).

[0087] In the present disclosure, the transfer process is performed using a laser blister transfer method while the second transfer substrate (60) and the target substrate (10) are positioned to maintain a predetermined distance, i.e., while maintaining a non-contact state. In the transfer process, the laser transfer can be performed while moving the target substrate (10) at a constant speed. Alternatively, in the transfer process, the laser blister transfer can be performed while simultaneously moving the second transfer substrate (60) and the target substrate (10) at the same speed or at different speeds. Accordingly, the transfer method according to one or more examples can improve the work speed compared to the transfer method of the prior art, i.e., the transfer method in which laser transfer is performed while the transfer substrate and the target substrate (or another transfer substrate) are maintained in a contact state.

[0088] The present disclosure describes, but is not limited to, transferring a plurality of micro LEDs from a second transfer substrate (60) to a target substrate (10). If necessary, a plurality of micro LEDs of the second transfer substrate (60) may be transferred to the target substrate (10) through an n-th transfer process via a plurality of transfer substrates, such as a third transfer substrate and a fourth transfer substrate. Here, n is a positive integer.

[0089] FIG. 12 is a diagram illustrating an example of thermally compressing a plurality of micro LEDs transferred to a target substrate according to one or more embodiments.

[0090] A plurality of micro LEDs (100, 200, 300) arranged at a preset pixel pitch (or display pitch) on a target substrate (10) may not be completely physically and electrically connected to each corresponding substrate pad (11, 12, 13, 14, 15, 16) of each contact electrode (101, 102, 201, 202, 301, 302).

[0091] Referring to Fig. 12, the block (80) of the press device can be used to press the light-emitting surfaces (105, 205, 305) of a plurality of micro LEDs (100, 200, 300) toward the target substrate (10). In this case, high-temperature heat can be provided to the stage supporting the block (80) and / or the target substrate (10).

[0092] By this thermal compression process, each contact electrode (101, 102, 201, 202, 301, 302) of a plurality of micro LEDs (100, 200, 300) can be electrically and physically connected to each corresponding substrate pad (11, 12, 13, 14, 15, 16).

[0093] In the present disclosure, by performing the transfer process of a plurality of micro LEDs using the laser blister transfer method as described above, no residue (e.g., a portion of an adhesive layer used on a transfer substrate) remains on the surface (e.g., a light-emitting surface) of the micro LED, as occurs during the conventional laser ablation transfer process. Therefore, in the present disclosure, the descum process for removing residue can be omitted, thereby improving damage to the micro LEDs during the descum process.

[0094] The aforementioned transfer substrate (50) used in the laser blister transfer method is composed of two layers, the thin film (51) being a laser blister layer (52) and an adhesive layer (53). The transfer substrate described below describes an example in which the thin film is composed of one layer.

[0095] FIG. 13 is a drawing showing a transfer substrate according to one or more embodiments.

[0096] Referring to FIG. 13, the transfer substrate (90) may include a thin film (81) formed as a single layer on one side. The thin film (91) may have a predetermined material and a predetermined thickness so as to maintain transfer precision and transfer speed through a blister transfer method, and may have adhesiveness to which a plurality of micro LEDs may be attached.

[0097] For example, the thin film (91) may be made of a polyimide-based mixed material and may have a thickness range of 3 μm to 20 μm. In this case, the UV laser (L2, see FIG. 8) irradiated onto the transfer substrate (90) may have a wavelength range of 190 nm to 360 nm, which is a short wavelength region, to improve damage to a plurality of micro LEDs transferred from the transfer substrate to the n-th transfer substrate or from the n-th transfer substrate to the target substrate. The short wavelength of the UV laser may be one of 193 nm, 248 nm, 266 nm, 308 nm, and 355 nm.

[0098] The thin film (91) of the transfer substrate (90) is formed of a single layer, but can implement a function similar to or substantially the same as that of the thin film (51) of the aforementioned transfer substrate (50). Therefore, a plurality of micro LEDs can be transferred to an n-th transfer substrate or a target substrate using a laser blister transfer method using the transfer substrate (90).

[0099] While the present disclosure has been illustrated and described above with reference to various embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. In the transfer board, a light-transmitting substrate; and A thin film laminated on one surface of the above-mentioned light-transmitting substrate and having a plurality of micro LEDs (micro light emitting diodes) attached thereto; The above thin film is a transfer substrate in which bubbles are formed by a UV laser for use in the laser blister transfer method.

2. In paragraph 1, A transfer substrate, wherein the UV laser irradiated onto the above transparent substrate and the above thin film has a short wavelength range of 190 nm to 360 nm.

3. In paragraph 2, The short wavelength of the above UV laser is one of 193 nm, 248 nm, 266 nm, 308 nm and 355 nm, the transfer substrate.

4. In paragraph 1, The above thin film is a transfer substrate comprising a polyimide-based mixed material.

5. In paragraph 4, The above thin film is a transfer substrate having a thickness range of 3㎛ to 20㎛.

6. In paragraph 1, The above thin film is, A laser blister layer laminated on one surface of the above light-transmitting substrate; and A transfer substrate comprising an adhesive layer laminated on the laser blister layer.

7. In paragraph 6, The above laser blister layer is a transfer substrate comprising a polyimide-based material.

8. In paragraph 7, The above laser blister layer has a thickness range of 0.01㎛ to 1㎛, and the transfer substrate.

9. In paragraph 6, A transfer substrate, wherein the adhesive layer comprises a polydimethylsiloxane (PDMS)-based material.

10. In paragraph 9, A transfer substrate, wherein the adhesive layer has a thickness range of 1㎛ to 5㎛.

11. In the micro LED transfer method, A step of transferring a plurality of micro LEDs from a wafer to a first transfer substrate; A step of irradiating the first transfer substrate with a UV laser to transfer the plurality of micro LEDs from the first transfer substrate to the second transfer substrate by a laser blister transfer method; and A step of irradiating the second transfer substrate with a UV laser to transfer the plurality of micro LEDs from the second transfer substrate to the target substrate by a laser blister transfer method; A micro LED transfer method in which the UV laser used in the above laser blister transfer method has a short wavelength range of 190 nm to 360 nm.

12. In paragraph 11, A micro LED transfer method, wherein the short wavelength of the UV laser used in the above laser blister transfer method is one of 193 nm, 248 nm, 266 nm, 308 nm and 355 nm.

13. In paragraph 11, Each of the first thin film applied to the first transfer substrate and the second thin film applied to the second transfer substrate, A micro LED transfer method in which a plurality of micro LEDs are attached and generate bubbles in response to the UV laser, and have a thickness range of 3 μm to 20 μm.

14. In paragraph 11, Each of the first thin film applied to the first transfer substrate and the second thin film applied to the second transfer substrate, A first layer that generates bubbles in response to the UV laser; and A second layer laminated on the first layer and having the plurality of micro LEDs attached thereto; The above first layer swells while generating bubbles in response to the UV laser, A micro LED transfer method, wherein the second layer is deformed together with the first layer to move the plurality of micro LEDs to a transfer position.

15. In paragraph 14, The above first layer has a thickness range of 0.01㎛ to 1㎛, A micro LED transfer method, wherein the second layer has a thickness range of 1 μm to 5 μm.

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