Patent Publication Number: US-2023163248-A1

Title: Semiconductor light-emitting device self-assembly apparatus and method

Description:
TECHNICAL FIELD 
     The present disclosure relates to a self-assembly apparatus and method for manufacturing a display device using a semiconductor light emitting diode having a size of several μm to several tens of μm. 
     BACKGROUND ART 
     Recently, liquid crystal displays (LCD), organic light-emitting diode (OLED) displays, and micro LED displays are competing to implement a large-area display in the field of display technology. 
     Meanwhile, if a semiconductor light emitting diode (micro LED; uLED) having a cross-sectional area or diameter of 100 μm or less is used in the display, the display does not absorb light using a polarizing plate or the like, and thus, very high efficiency can be provided. However, since a large display requires millions of semiconductor light emitting diodes, it is difficult to transfer the elements, compared to other technologies. 
     Examples of a technology that is currently being developed as a transfer process include pick &amp; place, laser lift-off (LLO), or self-assembly. Among them, the self-assembly is a method in which a semiconductor light emitting diode finds its own position in the fluid, and is the most advantageous method for realizing a large-screen display device. 
     Recently, although a micro LED structure suitable for self-assembly has been proposed in U.S. Pat. No. 9,825,202, research on a technology for manufacturing a display through self-assembly of the micro LED is still insufficient. Accordingly, the present disclosure proposes a new type of manufacturing method and manufacturing apparatus capable of performing self-assembly of micro LEDs. 
     DISCLOSURE 
     Technical Problem 
     One object of the present disclosure is to provide a new manufacturing process having high reliability in a large-screen display using a micro-sized semiconductor light emitting diode. 
     Another object of the present disclosure is to provide a manufacturing process capable of improving transfer precision when self-assembling a semiconductor light emitting diode using a temporary board or a wiring board. 
     Another object of the present disclosure is to provide a manufacturing process that can effectively solve assembly defects generated during self-assembly. 
     Technical Solution 
     In order to achieve the above object, the present disclosure provides a self-assembly apparatus of a semiconductor light emitting diode which includes a fluid chamber including a space configured to accommodate a plurality of semiconductor light emitting diodes having a magnetic material and a fluid; a magnet configured to apply a magnetic force to the semiconductor light emitting diodes in a state where an assembly surface of a board is submerged in the fluid; a power supply portion configured to induce a formation of an electric field between assembly electrodes provided on the board so that the semiconductor light emitting diodes are seated at a predetermined position of the board while the semiconductor light emitting diodes are moved by a change in a position of the magnet; and a repair portion disposed in the fluid chamber and configured to separate some of the semiconductor light emitting diodes seated on the board from the board, in which the repair portion is configured to spray and suction the fluid. 
     In an embodiment, the repair portion may comprise a body portion, the body portion may include an upper surface disposed to face the assembly surface; a lower surface spaced apart from the upper surface; and a plurality of sidewalls disposed between the upper surface and the lower surface, and at least one hole may be formed in the upper surface. 
     In an embodiment, the repair portion may include a fluid controller configured to supply a fluid to an inner space of the body portion and suction the fluid filled in the space. 
     In an embodiment, the repair portion may include a position adjusting portion configured to move a position of the fluid controller; and a controller configured to control the position adjusting portion and the fluid controller. 
     In an embodiment, the controller may be configured to control the position adjusting portion so that the hole overlaps the semiconductor light emitting diode in which the assembly defect has occurred on the board; and control the fluid controller so that the fluid is suctioned into the inner space of the body portion in a state where the hole overlaps the semiconductor light emitting diode in which the assembly defect has occurred. 
     In an embodiment, the controller may be configured to control the fluid controller so that the fluid is suctioned into the inner space of the body portion until the semiconductor light emitting diode in which the assembly defect has occurred is adsorbed on the upper surface. 
     In an embodiment, the controller may be configured to, before the fluid is suctioned into the inner space of the body portion, control the position controller so that the hole overlaps another semiconductor light emitting diode adjacent to the semiconductor light emitting diode in which the assembly defect has occurred, and in a state where the hole overlaps the another semiconductor light emitting diode, control the fluid controller so that the fluid is sprayed through the hole. 
     In addition, the present disclosure provides a self-assembly method of a semiconductor light emitting diode which includes transferring a board so that an assembly surface of the board is submerged in a fluid accommodated in a fluid chamber; putting semiconductor light emitting diodes into the fluid chamber; applying a magnetic force to the semiconductor light emitting diodes so that the semiconductor light emitting diodes move in one direction in the fluid chamber; inducing the semiconductor light emitting diodes to predetermined positions by applying power to a plurality of electrodes disposed on the assembly surface of the board so that the semiconductor light emitting diodes are seated at the predetermined positions of the board while the semiconductor light emitting diodes are moved; and suctioning the fluid into a repair portion so that the semiconductor light emitting diode in which an assembly defect has occurred is separated from the board, in which the semiconductor light emitting diode in which the assembly defect has occurred includes a semiconductor light emitting diode that is not seated at the predetermined position. 
     In an embodiment, the step of suctioning the fluid into the repair portion may include transferring the repair portion so that a hole provided in the repair portion overlaps the semiconductor light emitting diode in which the assembly defect has occurred; and suctioning the fluid into the repair portion in a state where the hole overlaps the semiconductor light emitting diode in which the assembly defect has occurred. 
     In an embodiment, the self-assembly method of a semiconductor light emitting diode may further include, before the suctioning the fluid into the repair portion, transferring the repair portion so that the hole overlaps another semiconductor light emitting diode adjacent to the semiconductor light emitting diode in which the assembly defect has occurred; and in a state where the hole overlaps the another semiconductor light emitting diode, spraying the fluid through the hole. 
     Advantageous Effect 
     According to the present disclosure having the above configuration, in a display device in which individual pixels are formed of micro light emitting diodes, a large number of semiconductor light emitting diodes can be assembled at once. 
     As described above, according to the present disclosure, it is possible to pixelate a semiconductor light emitting diode in a large amount on a small-sized wafer and then transfer it to a large-area board. Through this, it is possible to manufacture a large-area display device at a low cost. 
     In addition, according to the manufacturing method and apparatus of the present disclosure, a semiconductor light emitting diode is transferred simultaneously and multiple times in place using a magnetic field and an electric field in a solution, thereby being capable of realizing low-cost, high-efficiency, and high-speed transfer regardless of the size, number, or transfer area of parts. 
     In addition, according to the manufacturing method and apparatus of the present disclosure, since assembly defects generated during self-assembly can be eliminated, the defect rate of the display device can be significantly reduced. 
     In addition, according to the present disclosure, the semiconductor light emitting diode that is incorrectly assembled is separated from the board by suctioning the fluid, and even if the semiconductor light emitting diode is separated from the board, the semiconductor light emitting diode is not damaged and can be recycled. In addition, according to the present disclosure, since the fluid suctioned into the repair portion has little effect on the board, there is no risk of damage to the board in the process of separating the semiconductor light emitting diode from the board. 
     In addition, according to the present disclosure, by spraying the fluid to the semiconductor light emitting diode disposed in the vicinity of the semiconductor light emitting diode in which the assembly defect has occurred, the semiconductor light emitting diode disposed in the vicinity of the semiconductor light emitting diode in which the assembly defect has occurred is strongly fixed to the board. Through this, the present disclosure can minimize the influence of the fluid suction of the repair portion. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a conceptual diagram illustrating an embodiment of a display device using a semiconductor light emitting diode of the present disclosure. 
         FIG.  2    is a partially enlarged view of portion A of the display device of  FIG.  1   . 
         FIG.  3    is an enlarged view of the semiconductor light emitting diode of  FIG.  2   . 
         FIG.  4    is an enlarged view illustrating another embodiment of the semiconductor light emitting diode of  FIG.  2   . 
         FIGS.  5 A to  5 E  are conceptual views for describing a new process of manufacturing the semiconductor light emitting diode. 
         FIG.  6    is a conceptual diagram illustrating an example of a self-assembly apparatus of a semiconductor light emitting diode according to the present disclosure. 
         FIG.  7    is a block diagram of the self-assembly apparatus of  FIG.  6   . 
         FIGS.  8 A to  8 E  are conceptual views illustrating a process of self-assembling a semiconductor light emitting diode using the self-assembly apparatus of  FIG.  6   . 
         FIG.  9    is a conceptual diagram for describing the semiconductor light emitting diode of  FIGS.  8 A to  8 E . 
         FIGS.  10  and  11    are cross-sectional views of a repair portion according to an embodiment of the present disclosure. 
         FIG.  12    is a conceptual diagram illustrating a state where the repair portion according to the present disclosure is viewed from the bottom plate of the fluid chamber. 
         FIGS.  13 A to  13 D  are conceptual views illustrating types of semiconductor light emitting diodes mounted on a board. 
         FIGS.  14 A to  14 D  are conceptual views illustrating a self-assembly method using a repair portion. 
         FIGS.  15  and  16    are conceptual views illustrating a method of minimizing the influence of the surrounding by the fluid suction of the repair portion. 
     
    
    
     BEST MODE 
     Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings, and the same or similar elements are designated with the same numeral references regardless of the numerals in the drawings and their redundant description will be omitted. The suffixes “module” and “unit or portion” for components used in the following description are merely provided only for facilitation of preparing this specification, and thus they are not granted a specific meaning or function. In addition, when it is determined that the detailed description of the related known technology may obscure the gist of embodiments disclosed herein in describing the embodiments, a detailed description thereof will be omitted. Further, it should be noted that the accompanying drawings are only for easy understanding of the embodiments disclosed in the present specification, and should not be construed as limiting the technical spirit disclosed in the present specification by the accompanying drawings. It is also understood that when an element, such as a layer, region, or substrate, it is referred to as being “on” another element, it may be directly present on the other element or intervening elements in between. 
     The display device described herein may include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDA), portable multimedia players (PMP), navigation systems, slate PCs, a Tablet PC, Ultra Books, digital TVs, digital signages, head mounted displays (HMDs), desktop computers, and the like. However, it will be readily apparent to those skilled in the art that the configuration according to the embodiments described in the present specification may be applied to a device capable of display having even a new product form to be developed later. 
       FIG.  1    is a conceptual diagram illustrating an embodiment of a display device using a semiconductor light emitting diode of the present disclosure,  FIG.  2    is a partially enlarged view of portion A of the display device of  FIG.  1   ,  FIG.  3    is an enlarged view of the semiconductor light emitting diode of  FIG.  2   , and  FIG.  4    is an enlarged view illustrating another embodiment of the semiconductor light emitting diode of  FIG.  2   . 
     As illustrated, information processed by a controller of a display device  100  may be output from a display module  140 . A closed-loop-type case  101  surrounding edges of the display module may form a bezel of the display device. 
     The display module  140  may include a panel  141  on which images are displayed, and the panel  141  may include a micro-sized semiconductor light emitting diode  150  and a wiring board  110  on which the semiconductor light emitting diode  150  is mounted. 
     Wirings may be formed on the wiring board  110  to be connected to an n-type electrode  152  and a p-type electrode  156  of the semiconductor light emitting diode  150 . Through this, the semiconductor light emitting diode  150  may be provided on the wiring board  110  as an individual pixel that emits light itself. 
     An image displayed on the panel  141  is visual information, and is implemented by independently controlling light emission of sub-pixels arranged in a matrix form through the wirings. 
     In the present disclosure, a micro LED (Light Emitting Diode) is exemplified as a type of the semiconductor light emitting diode  150  that converts current into light. The micro LED may be a light emitting diode formed in a small size of 100 micro or less. In the semiconductor light emitting diode  150 , blue, red, and green colors are provided in light emitting regions, respectively, and a unit pixel may be realized by a combination thereof. That is, the unit pixel may mean a minimum unit for realizing one color, and at least three micro LEDs may be provided in the unit pixel. 
     More specifically, referring to  FIG.  3   , the semiconductor light emitting diode  150  may have a vertical structure. 
     For example, the semiconductor light emitting diode  150  is mainly made of gallium nitride (GaN), and indium (In) and/or aluminum (Al) are added together to implement a high output light emitting diode that emits various lights including blue. 
     The vertical semiconductor light emitting diode may include a p-type electrode  156 , a p-type semiconductor layer  155  formed on the p-type electrode  156 , an active layer  154  formed on the p-type semiconductor layer  155 , an n-type semiconductor layer  153  formed on the active layer  154 , and an n-type electrode  152  formed on the n-type semiconductor layer  153 . In this case, the p-type electrode  156  positioned in a lower portion may be electrically connected to the p-electrode of the wiring board, and the n-type electrode  152  positioned in an upper portion may be electrically connected to the n-electrode at the upper side of the semiconductor light emitting diode. The vertical semiconductor light emitting diode  150  has a great advantage in that it is possible to reduce the chip size because electrodes are arranged up and down. 
     As another example, referring to  FIG.  4   , the semiconductor light emitting diode may be a flip chip type light emitting diode. 
     For this example, the semiconductor light emitting diode  250  may include a p-type electrode  256 , a p-type semiconductor layer  255  on which the p-type electrode  256  is formed, an active layer  254  formed on the p-type semiconductor layer  255 , an n-type semiconductor layer  253  formed on the active layer  254 , and an n-type electrode  252  spaced apart from the p-type electrode  256  in the horizontal direction on the n-type semiconductor layer  253 . In this case, both the p-type electrode  256  and the n-type electrode  152  may be electrically connected to the p-electrode and n-electrode of the wiring board under the semiconductor light emitting diode. 
     The vertical semiconductor light emitting diode and the horizontal semiconductor light emitting diode may be a green semiconductor light emitting diode, a blue semiconductor light emitting diode, or a red semiconductor light emitting diode, respectively. In the case of the green semiconductor light emitting diode and the blue semiconductor light emitting diode, gallium nitride (GaN) is mainly used, and indium (In) and/or aluminum (Al) are added together to implement a high output light emitting diode that emits green or blue light. For this example, the semiconductor light emitting diode may be a gallium nitride thin film formed in various layers such as n-Gan, p-Gan, AlGaN, InGan, etc. Specifically, the p-type semiconductor layer may be P-type GaN, and the n-type semiconductor layer may be N-type GaN. However, in the case of the red semiconductor light emitting diode, the p-type semiconductor layer may be P-type GaAs, and the n-type semiconductor layer may be N-type GaAs. 
     In addition, the p-type semiconductor layer may be P-type GaN doped with Mg on the p-electrode side, and the n-type semiconductor layer may be N-type GaN doped with Si on the n-electrode side. In this case, the above-described semiconductor light emitting diodes may be semiconductor light emitting diodes having no active layer. 
     Meanwhile, referring to  FIGS.  1  to  4   , since the light emitting diodes are very small, unit pixels that emit light themselves may be arranged in a high definition in the display panel, thereby realizing a high-definition display device. 
     In the display device using the semiconductor light emitting diode of the present disclosure described above, the semiconductor light emitting diode grown on a wafer and formed through mesa and isolation is used as an individual pixel. In this case, the micro-sized semiconductor light emitting diode  150  needs to be transferred to the wafer at a predetermined position on a substrate of the display panel. There is a pick and place technique as such a transfer technique, but the success rate is low and a lot of time is required. As another example, there is a technique of transferring several devices at a time using a stamp or a roll, but it is not suitable for a large screen display due to a limitation in yield. The present disclosure proposes a new manufacturing method and manufacturing apparatus for a display device that can solve these problems. 
     To this end, a new method of manufacturing a display device will be described below.  FIGS.  5 A to  5 E  are conceptual views for describing a new process of manufacturing the semiconductor light emitting diode. 
     In the present specification, a display device using a passive matrix (PM) type semiconductor light emitting diode is taken as an example. However, the examples described below are also applicable to an active matrix (AM) type semiconductor light emitting diode. In addition, although a method of self-assembling a horizontal semiconductor light emitting diode is described as an example, it is also applicable to a method of self-assembling a vertical semiconductor light emitting diode. 
     First, according to the manufacturing method, a first conductivity type semiconductor layer  153 , an active layer  154 , and a second conductivity type semiconductor layer  155  are individually grown on a growth substrate  159  ( FIG.  5 A ). 
     After the first conductivity type semiconductor layer  153  is grown, the active layer  154  is grown on the first conductivity type semiconductor layer  153 , and then the second conductivity type semiconductor layer  155  is grown on the active layer  154 . In this way, when the first conductivity type semiconductor layer  153 , the active layer  154 , and the second conductivity type semiconductor layer  155  are sequentially grown, as shown in  FIG.  5   a   , the first conductivity type semiconductor layer  153 , the active layer  154  and the second conductive semiconductor layer  155  form a stacked structure. 
     In this case, the first conductivity type semiconductor layer  153  may be a p-type semiconductor layer, and the second conductivity type semiconductor layer  155  may be an n-type semiconductor layer. However, the present disclosure is not necessarily limited thereto, and the first conductivity type may be n-type and the second conductivity type may be p-type. 
     In addition, although the present embodiment exemplifies the case in which the active layer is present, a structure in which the active layer is not present is also possible in some cases as described above. As an example, the p-type semiconductor layer may be P-type GaN doped with Mg, and the n-type semiconductor layer may be N-type GaN doped with Si on the n-electrode side. 
     The growth substrate  159  (wafer) may be formed of a material having a light-transmitting property, for example, any one of sapphire (Al2O3), GaN, ZnO, and AlO, but is not limited thereto. In addition, the growth substrate  159  may be formed of a material suitable for semiconductor material growth, a carrier wafer. The growth substrate  159  may be formed of a material having excellent thermal conductivity, and may include a conductive board or an insulating board, for example, a SiC board having higher thermal conductivity than a sapphire (Al2O 3 ) board, or use at least one of Si, GaAs, GaP, InP, and Ga2O3. 
     Next, at least a portion of the first conductivity type semiconductor layer  153 , the active layer  154 , and the second conductivity type semiconductor layer  155  are removed to form a plurality of semiconductor light emitting diodes ( FIG.  5 B ). 
     More specifically, isolation is performed such that the plurality of light emitting diodes form a light emitting diode array. That is, the first conductivity type semiconductor layer  153 , the active layer  154 , and the second conductivity type semiconductor layer  155  are vertically etched to form a plurality of semiconductor light emitting diodes. 
     In the case of forming a horizontal type semiconductor light emitting diode, a mesa process in which the active layer  154  and the second conductivity type semiconductor layer  155  are partially removed in the vertical direction and the first conductivity type semiconductor layer  153  is exposed to the outside and thereafter, isolation in which the first conductivity type semiconductor layer is etched to form a plurality of semiconductor light emitting diode arrays may be performed. 
     Next, second conductivity type electrodes  156  (or p-type electrodes) are formed on one surface of the second conductivity type semiconductor layer  155  ( FIG.  5 C ). The second conductivity type electrode  156  may be formed by a deposition method such as sputtering, but the present disclosure is not limited thereto. However, when the first conductive semiconductor layer and the second conductive semiconductor layer are an n-type semiconductor layer and a p-type semiconductor layer, respectively, the second conductivity type electrode  156  may be an n-type electrode. 
     Then, the growth substrate  159  is removed to provide a plurality of semiconductor light emitting diodes. For example, the growth substrate  159  may be removed using a laser lift-off (LLO) method or a chemical lift-off (CLO) method ( FIG.  5 D ). 
     Thereafter, the semiconductor light emitting diodes  150  are seated on a board in a chamber filled with a fluid ( FIG.  5 E ). 
     For example, the semiconductor light emitting diodes  150  and the board are put in the chamber filled with a fluid, and the semiconductor light emitting diodes are self-assembled onto the board  161  using flow, gravity, surface tension, and the like. In this case, the board may be an assembled board  161 . 
     As another example, it is also possible to put the wiring board in a fluid chamber instead of the assembly board  161  so that the semiconductor light emitting diodes  150  are directly seated on the wiring board. In this case, the board may be a wiring board. However, for convenience of description, in the present disclosure, the board is provided as, for example, the assembly board  161  on which the semiconductor light emitting diodes  1050  are seated. 
     Cells (not shown) in which the semiconductor light emitting diodes  150  are inserted may be provided in the assembly board  161  to facilitate mounting of the semiconductor light emitting diodes  150  on the assembly board  161 . Specifically, cells in which the semiconductor light emitting diodes  150  are seated are formed in the assembly board  161  at positions where the semiconductor light emitting diodes  150  are to be aligned with wiring electrodes. The semiconductor light emitting diodes  150  are assembled to the cells while moving in the fluid. 
     After a plurality of semiconductor light emitting diodes are arrayed on the assembly board  161 , the semiconductor light emitting diodes of the assembly board  161  are transferred to a wiring board, enabling large-area transfer. Accordingly, the assembly board  161  may be referred to as a temporary board. 
     On the other hand, in order to apply the self-assembly method described above to the manufacture of a large-screen display, it is necessary to increase transfer yield. The present disclosure proposes a method and apparatus for minimizing the influence of gravity or frictional force and preventing non-specific binding in order to increase the transfer yield. 
     In this case, in the display device according to the present disclosure, a magnetic material is disposed on the semiconductor light emitting diode to move the semiconductor light emitting diode using magnetic force, and the semiconductor light emitting diode is seated at a predetermined position by using an electric field during movement. Hereinafter, the transfer method and apparatus will be described in more detail with the accompanying drawings. 
       FIG.  6    is a conceptual diagram illustrating an example of a self-assembly apparatus of a semiconductor light emitting diode according to the present disclosure, and  FIG.  7    is a block diagram of the self-assembly apparatus of  FIG.  6   .  FIGS.  8 A to  8 E  are conceptual views illustrating a process of self-assembling a semiconductor light emitting diode using the self-assembly apparatus of  FIG.  6   , and  FIG.  9    is a conceptual diagram for describing the semiconductor light emitting diode of  FIGS.  8 A to  8 E . 
     Referring to  FIGS.  6  and  7   , a self-assembly apparatus  160  of the present disclosure may include a fluid chamber  162 , a magnet  163  and a position control unit  164 . 
     The fluid chamber  162  has a space for accommodating a plurality of semiconductor light emitting diodes. The space may be filled with a fluid, and the fluid may include water or the like as an assembly solution. Accordingly, the fluid chamber  162  may be a water tank and may be configured in an open type. However, the present disclosure is not limited thereto, and the fluid chamber  162  may be of a closed type in which the space is a closed space. 
     The board  161  may be disposed in the fluid chamber  162  such that an assembly surface on which the semiconductor light emitting diodes  150  are assembled faces downward. For example, the board  161  may be transferred to an assembly position by a transfer device, and the transfer device may include a stage  165  on which the board is mounted. The position of the stage  165  is controlled by the control unit, and through this, the board  161  may be transferred to the assembly position. 
     In this case, in the assembly position, the assembly surface of the board  161  faces the bottom of the fluid chamber  150 . As shown, the assembly surface of the board  161  is disposed to be immersed in the fluid in the fluid chamber  162 . Accordingly, the semiconductor light emitting diode  150  moves to the assembly surface in the fluid. 
     The board  161  is an assembly board in which an electric field is able to be formed, and may include a base portion  161   a,  a dielectric layer  161   b,  and a plurality of electrodes  161   c.    
     The base portion  161   a  may be formed of an insulating material, and the plurality of electrodes  161   c  may be a thin or thick bi-planar electrode patterned on one surface of the base portion  161   a.  The electrode  161   c  may be formed of, for example, a stack of Ti/Cu/Ti, Ag paste, and ITO. 
     The dielectric layer  161   b  may be formed of an inorganic material such as SiO2, SiNx, SiON, Al2O3, TiO2, HfO2, or the like. Alternatively, the dielectric layer  161   b  may be comprised of a single layer or a multi-layer as an organic insulator. The dielectric layer  161   b  may have a thickness of several tens of nm to several μm. 
     Furthermore, the board  161  according to the present disclosure includes a plurality of cells  161   d  separated by barrier ribs. The cells  161   d  are sequentially arranged in one direction and may be made of a polymer material. Also, the barrier ribs  161   e  defining the cells  161   d  are shared with the neighboring cells  161   d.  The barrier ribs  161   e  may protrude from the base portion  161   a,  and the cells  161   d  may be sequentially arranged along one direction by the barrier ribs  161   e.  More specifically, the cells  161   d  are sequentially arranged in the column and row directions, respectively, and may have a matrix structure. 
     As shown, the cell  161   d  may have a groove for accommodating the semiconductor light emitting diode  150  and the groove may be a space defined by the barrier ribs  161   e.  The shape of the groove may be the same as or similar to that of the semiconductor light emitting diode. For example, when the semiconductor light emitting diode has a rectangular shape, the groove may have a rectangular shape. Also, although not shown, when the semiconductor light emitting diode has a circular shape, the groove formed in the cells may have a circular shape. Furthermore, each of the cells is configured to accommodate a single semiconductor light emitting diode. That is, one semiconductor light emitting diode is accommodated in one cell. 
     Meanwhile, the plurality of electrodes  161   c  may include a plurality of electrode lines disposed at the bottom of each of the cells  161   d,  and the plurality of electrode lines may extend to adjacent cells. 
     The plurality of electrodes  161   c  are disposed below the cells  161   d,  and different polarities are applied to the electrodes  161   c  to generate an electric field in the cells  161   d.  To form the electric field, the dielectric layer may form the bottom of the cells  161   d  while the dielectric layer is covering the plurality of electrodes  161   c.  In this structure, when different polarities are applied to the pair of electrodes  161   c  under the cells  161   d,  an electric field is formed, and the semiconductor light emitting diodes may be inserted into the cells  161   d  due to the electric field. 
     In the assembly position, the electrodes of the board  161  are electrically connected to a power supply device  171 . The power supply device  171  may apply power to the plurality of electrodes to generate the electric field. 
     As shown, the self-assembly apparatus may include a magnet  163  for applying a magnetic force to the semiconductor light emitting diodes. The magnet  163  is spaced apart from the fluid chamber  162  to apply a magnetic force to the semiconductor light emitting diodes  150 . The magnet  163  may be disposed to face the opposite surface of the assembly surface of the board  161 , and the position of the magnet is controlled by the position control unit  164  connected to the magnet  163 . 
     The semiconductor light emitting diode  1050  may include a magnetic material to move in the fluid due to the magnetic field of the magnet  163 . 
     Referring to  FIG.  9   , a semiconductor light emitting diode including a magnetic material may include a first conductivity type electrode  1052 , a second conductivity type electrode  1056 , a first conductivity type semiconductor layer  1053  on which the first conductivity type electrode  1052  is disposed, a second conductivity type semiconductor layer  1055  on which the second conductivity type electrode  1056  is disposed, the second conductivity type semiconductor layer  1055  overlapping the first conductivity type semiconductor layer  1052  and an active layer  1054  disposed between the first and second conductivity type semiconductor layers  1053  and  1055 . 
     Here, the first conductivity type may be p-type, the second conductivity type may be n-type, and vice versa. In addition, as described above, the semiconductor light emitting diode having no active layer may be used. 
     Meanwhile, in the present disclosure, the first conductivity type electrode  1052  may be generated after the semiconductor light emitting diode is assembled to the wiring board through self-assembly of the semiconductor light emitting diode. Also, in the present disclosure, the second conductivity type electrode  1056  may include the magnetic material. The magnetic material may mean a magnetic metal. The magnetic material may be Ni, SmCo, or the like, and as another example, may include a material corresponding to at least one of Gd-based, La-based, and Mn-based materials. 
     The magnetic material may be provided in the second conductivity type electrode  1056  in the form of particles. Alternatively, the conductivity type electrode including a magnetic material may have one layer formed of a magnetic material. For this example, as shown in  FIG.  9   , the second conductivity type electrode  1056  of the semiconductor light emitting diode  1050  may include a first layer  1056   a  and a second layer  1056   b.  Here, the first layer  1056   a  may include a magnetic material, and the second layer  1056   b  may include a metal material rather than a magnetic material. 
     As shown, in this example, the first layer  1056   a  including a magnetic material may be disposed to contact the second conductivity type semiconductor layer  1055 . In this case, the first layer  1056   a  is disposed between the second layer  1056   b  and the second conductivity type semiconductor layer  1055 . The second layer  1056   b  may be a contact metal connected to the second electrode of the wiring board. However, the present disclosure is not necessarily limited thereto, and the magnetic material may be disposed on one surface of the first conductivity type semiconductor layer. 
     Referring back to  FIGS.  6  and  7   , more specifically, the self-assembly apparatus is provided with a magnet handler that is movable automatically or manually in the x, y, and z axes on the upper portion of the fluid chamber, or a motor capable of rotating the magnet  163 . The magnet handler and the motor may constitute the position control unit  164 . Through this, the magnet  163  may rotate in a horizontal direction with the board  161 , clockwise or counterclockwise direction. 
     Meanwhile, a bottom plate  166  having a light-transmitting property may be formed in the fluid chamber  162 , and the semiconductor light emitting diodes may be disposed between the bottom plate  166  and the board  161 . An image sensor  167  may be disposed to face the bottom plate  166  to monitor the inside of the fluid chamber  162  through the bottom plate  166 . The image sensor  167  is controlled by the control unit  172  and may include an inverted type lens, a CCD and the like to observe the assembly surface of the board  161 . 
     The self-assembly apparatus described above is configured to use a combination of a magnetic field and an electric field, and when using this, the semiconductor light emitting diodes may be seated at predetermined positions on the board due to an electric field while moving by a change in the position of the magnet. Hereinafter, an assembly process using the self-assembly apparatus described above will be described in more detail. 
     First, a plurality of semiconductor light emitting diodes  1050  including a magnetic material are formed through the process described with reference to  FIGS.  5 A to  5 C . In this case, in the process of forming the second conductivity type electrode of  FIG.  5 C , a magnetic material may be deposited on the semiconductor light emitting diode. 
     Next, the board  161  is transferred to an assembly position, and the semiconductor light emitting diodes  1050  are put into the fluid chamber  162  ( FIG.  8 A ). 
     As described above, the assembly position of the board  161  may be a position in which the board  161  is to be disposed in the fluid chamber  162  such that the assembly surface of the board  161  on which the semiconductor light emitting diodes  1050  are to be assembled faces downward. 
     In this case, some of the semiconductor light emitting diodes  1050  may sink to the bottom of the fluid chamber  162  and some may float in the fluid. The bottom plate  166  having a light-transmitting property is provided in the fluid chamber  162 , and some of the semiconductor light emitting diodes  1050  may sink to the bottom plate  166 . 
     Next, a magnetic force is applied to the semiconductor light emitting diodes  1050  such that the semiconductor light emitting diodes  1050  vertically float in the fluid chamber  162  ( FIG.  8 B ). 
     When the magnet  163  of the self-assembly apparatus moves from its original position to the opposite surface of the assembly surface of the board  161 , the semiconductor light emitting diodes  1050  may float toward the board  161  in the fluid. The original position may be a position deviated from the fluid chamber  162 . As another example, the magnet  163  may be made of an electromagnet. In this case, electricity is supplied to the electromagnet to generate an initial magnetic force. 
     Meanwhile, in this example, when the magnitude of the magnetic force is adjusted, the separation distance between the assembly surface of the board  161  and the semiconductor light emitting diodes  1050  may be controlled. For example, the separation distance is controlled using the weight, buoyancy, and magnetic force of the semiconductor light emitting diodes  1050 . The separation distance may be several millimeters to several tens of micrometers from the outermost edge of the board. 
     Next, a magnetic force is applied to the semiconductor light emitting diodes  1050  such that the semiconductor light emitting diodes  1050  move in one direction in the fluid chamber  162 . For example, it is possible to move the magnet  163  in a direction horizontal to the board, clockwise or counterclockwise ( FIG.  8 C ). In this case, the semiconductor light emitting diodes  1050  move in a direction parallel to the board  161  from positions spaced apart from the board  161  due to the magnetic force. 
     Next, an electric field is applied to guide the semiconductor light emitting diodes  1050  to preset positions such that the semiconductor light emitting diodes  1050  are seated in the preset positions of the board  161  while the semiconductor light emitting diodes  1050  are moving ( FIG.  8 C ). For example, while the semiconductor light emitting diodes  1050  are moving in a direction horizontal to the board  161 , the semiconductor light emitting diodes  1050  may move in a direction perpendicular to the board  161  due to the electric field, and be then seated in the preset positions of the board  161 . 
     More specifically, an electric field is generated by supplying power to the bi-planar electrode of the board  161  to enable assembly to be made only at preset positions. That is, the semiconductor light emitting diodes  1050  are self-assembled at assembly positions of the board  161  by using the selectively generated electric field. To this end, cells in which the semiconductor light emitting diodes  1050  are inserted may be provided in the board  161 . 
     Thereafter, a process of unloading the board  161  is performed, and the assembly process is finished. When the board  161  is an assembly board, a post-process for realizing a display device by transferring the semiconductor light emitting diodes arranged as described above to a wiring board may be performed. 
     Meanwhile, after guiding the semiconductor light emitting diodes  1050  to the preset positions, the magnet  163  may be moved in a direction away from the board  161  such that the semiconductor light emitting diodes  1050  remaining in the fluid chamber  162  fall to the bottom of the fluid chamber  162  ( FIG.  8 D ). As another example, when power supply is stopped in a case where the magnet  163  is an electromagnet, the semiconductor light emitting diodes  1050  remaining in the fluid chamber  162  may fall to the bottom of the fluid chamber  162 . 
     Thereafter, when the semiconductor light emitting diodes  1050  at the bottom of the fluid chamber  162  are recovered, the recovered semiconductor light emitting diodes  1050  may be reused. 
     The self-assembly apparatus and method described above may use a magnetic field to enable distant parts to congregate near a predetermined assembly site and apply a separate electric field to the assembly site such that the parts are selectively assembled only to the assembly site in order to increase the assembly yield in fluidic assembly. In this case, the assembly board is placed on the upper portion of the water tank and the assembly surface is directed downward to minimize the effect of gravity due to the weight of the parts and prevent non-specific binding to eliminate defects. That is, to increase the transfer yield, the assembly board is placed on the upper portion to minimize the effect of gravity or frictional force, and to prevent non-specific binding. 
     As described above, according to the present disclosure having the above configuration, in a display device in which individual pixels are formed of semiconductor light emitting diodes, a large number of semiconductor light emitting diodes may be assembled at once. 
     As described above, according to the present disclosure, it is possible to pixelate a large amount of semiconductor light emitting diodes on a small-sized wafer and then transfer the semiconductor light emitting diodes to a large-area substrate. Through this, it is possible to manufacture a large-area display device at a low cost. 
     Meanwhile, although the assembly accuracy of the self-assembly method described above is very high, the semiconductor light emitting diode may not be disposed at a predetermined position or may not be disposed in a designated orientation with a very low probability. In other words, assembly defects may occur with a very low probability in the self-assembly process. 
     In the case of a large-area display device, since hundreds or tens of millions of semiconductor light emitting diodes are transferred, the number of defective pixels becomes non-negligible even though the assembly defect probability is very low. For this reason, there is a need for a means capable of resolving assembly defects after self-assembly. 
     The present disclosure provides an apparatus and method capable of resolving assembly defects after self-assembly. The present disclosure further includes a repair portion in the self-assembly apparatus described above. 
     First, the structure of the repair portion will be described, but the structure to be described below is only an example of the repair portion according to the present disclosure, and the structure of the repair portion is not limited thereto. 
       FIGS.  10  and  11    are cross-sectional views of a repair portion according to an embodiment of the present disclosure, and  FIG.  12    is a conceptual diagram illustrating a state where the repair portion according to the present disclosure is viewed from the bottom plate of the fluid chamber. 
     Referring to  FIG.  10   , the repair portion  300  includes a body portion. The body portion may include an upper surface  310 , a lower surface  320 , and a plurality of sidewalls  330 . Meanwhile, at least one hole  311  may be formed in the upper surface  310 . 
     In the present specification, a space surrounded by the upper surface  310 , the lower surface  320 , and the plurality of side walls  330  is defined as an inner space of the body portion. The fluid flows into the inner space of the body portion or is discharged to the outside of the body portion, through the hole. Here, the fluid flows in toward the hole  311  or is ejected in a direction the hole  311  faces. 
     Here, the upper surface of the repair portion may be made of glass as shown in  FIG.  10    or made of a silicone material as shown in  FIG.  11   , but is not limited thereto. 
     The hole may be formed in any one of a circular shape and a slit shape, but is not limited thereto. 
     Meanwhile, the repair portion  300  according to the present disclosure includes a fluid controller  340 . The fluid controller  340  is configured to supply fluid to the inner space of the body portion and suction the fluid filled in the space. 
     An embodiment in which the fluid controller  340  suctions the fluid will first be described. The fluid controller  340  suctions the fluid filled in the space so that a portion of the fluid accommodated in the fluid chamber is suctioned into the body portion through the hole  311 . When the body portion suctions the fluid in a state where the body portion is disposed at a position sufficiently close to the semiconductor light emitting diode, a suction force acts on the semiconductor light emitting diode. Accordingly, the semiconductor light emitting diode to which the suction force acts is moved in the direction of the body portion. This will be described below. 
     Meanwhile, the fluid controller  340  is configured to supply a fluid into the body portion. The fluid controller  340  supplies a fluid to the inner space of the body portion so that a portion of the fluid accommodated in the body portion is ejected to the outside of the body portion through the hole  311 . When the body portion ejects a fluid while the body portion is disposed sufficiently close to the semiconductor light emitting diode, the ejected fluid may affect the semiconductor light emitting diode. An effect of the fluid on the semiconductor light emitting diode may vary according to a relative position between the hole and the semiconductor light emitting diode. This will be described below. 
     However, the fluid should be selectively sprayed onto any one of the semiconductor light emitting diodes assembled at intervals of less than 500 μm. For this reason, the size of the hole  311  should be very small. Specifically, the diameter of the hole  311  is preferably formed within several tens of μm. Meanwhile, a distance between the board and the bottom plate of the fluid chamber may be very narrow. In an embodiment, a distance between the board and the bottom plate may be 2 mm. 
     The repair portion  300  should be able to move forward, backward, left and right in the space. To this end, the present disclosure may further include a position adjusting portion for allowing the repair portion  300  to move between the assembly surface of the board and the bottom plate. 
     As shown in  FIG.  12   , when the bottom plate of the fluid chamber  500  is made of a light-transmitting material, the position of the repair portion  300  may be checked in real time. Through this, the position of the repair portion  300  of the present disclosure can be precisely adjusted. However,  FIG.  12    is a diagram for better understanding, and in fact, the hole provided in the repair portion  300  is disposed to face the board, not the bottom plate. 
     Meanwhile, whether or not an assembly defect has occurred and the location of the occurrence may be detected through the monitoring result of the image sensor. The position adjusting portion moves the position of the repair portion so that the hole of the repair portion faces the location where the assembly defect has occurred. 
     The self-assembly apparatus according to the present disclosure may include a controller configured to control the position adjusting portion and the fluid controller  340 . The controller may be the same controller as the controller  172  described with reference to  FIG.  7    or a separately provided controller. In this specification, the controller configured to control the position adjusting portion and the fluid controller  340  and the controller  172  described with reference to  FIG.  7    are not distinguished, but the two controllers are not necessarily the same controller. 
     The fluid may be the same material as the fluid in the fluid chamber, but is not limited thereto. In an embodiment, the fluid may be water. 
     After self-assembly, the repair portion  300  is used to separate the semiconductor light emitting diodes in which the assembly defect has occurred among the semiconductor light emitting diodes seated on the board from the board. However, the semiconductor light emitting diode separated from the board by the repair portion  300  is not limited to the semiconductor light emitting diode in which the assembly defect has occurred. For example, even a semiconductor light emitting diode in which some of the normally assembled semiconductor light emitting diodes are damaged may be separated from the board by the repair portion  300 . 
     Hereinafter, a type in which the assembly defect has occurred will be described. 
       FIGS.  13 A to  13 D  are conceptual views illustrating types of semiconductor light emitting diodes mounted on a board. 
     When the step described with reference to  FIG.  8 E  is finished, some of the semiconductor light emitting diodes put into the fluid are affected by the magnetic field formed in the board to be seated on the board. In order not to cause assembly defects, the semiconductor light emitting diode should be seated at a predetermined position on the board, and a predetermined surface of the semiconductor light emitting diode should be disposed to face the board. In the present specification, one surface of the semiconductor light emitting diode to be disposed to face the board during self-assembly is referred to as a first surface. Alternatively, a surface opposite to the first surface is referred to as a second surface. 
     Referring to  FIG.  13 A , the first surface of the semiconductor light emitting diode  1150   a  seated on the board may be disposed at an angle to the assembly surface of the board. In this case, it becomes difficult to form a wiring electrode for supplying power to the semiconductor light emitting diode  1150   a.  In addition, there is a high possibility that the semiconductor light emitting diode  1150   a  is separated from the board in a later process. Accordingly, the disposition of the semiconductor light emitting diode according to  FIG.  13 A  corresponds to one type of assembly defect. 
     Meanwhile, referring to  FIG.  13 B , the semiconductor light emitting diode  1150   b  seated on the board may be disposed at a predetermined position on the board, and a first surface of the semiconductor light emitting diode  1150   b  may be disposed to face the board. Accordingly, the disposition of the semiconductor light emitting diode according to  FIG.  13 B  corresponds to a normal disposition. The semiconductor light emitting diode seated on the board should have a disposition as shown in  FIG.  13 B . 
     Meanwhile, referring to  FIG.  13 C , the semiconductor light emitting diode  1150   c  seated on the board may not be disposed at a predetermined position on the board. In this case, it is difficult to form a wiring electrode for supplying power to the semiconductor light emitting diode  1150   c,  and it is difficult to form a pixel at a designated position. Accordingly, the disposition of the semiconductor light emitting diode according to  FIG.  13 C  corresponds to one type of assembly defect. 
     Finally, referring to  FIG.  13 D , the second surface of the semiconductor light emitting diode  1150   d  seated on the board may be disposed to face the board. In this case, the wiring electrode cannot be connected to the semiconductor light emitting diode  1150   d.  Accordingly, the disposition of the semiconductor light emitting diode according to  FIG.  13 D  corresponds to one type of assembly defect. 
     As described above, various types of assembly defects may occur in the semiconductor light emitting diode mounted on the board.  FIGS.  13 A,  13 C, and  13 D  only show an example of an assembly defect, and the drawings do not limit the type of assembly defect. A structure other than the structure described with reference to  FIG.  13 B  may be defined as an assembly defect. 
     The repair portion  300  according to the present disclosure allows the semiconductor light emitting diode having an assembly defect to be separated from the board. 
     Hereinafter, a self-assembly method of the semiconductor light emitting diode using the repair portion will be described. 
       FIGS.  14 A to  14 C  are conceptual views illustrating a self-assembly method using a repair portion. 
     First, the self-assembly method described with reference to  FIGS.  8 A to  8 E  is performed. 
     Thereafter, a step of suctioning a fluid into the repair portion in the fluid chamber is performed so that the semiconductor light emitting diode in which the assembly defect has occurred on the board is separated from the board. 
     Referring to  FIG.  14 A , after the self-assembly described with reference to  FIGS.  8 A to  8 E  is finished, assembly defects may occur in some semiconductor light emitting diodes. The position adjusting portion moves the repair portion so that the hole  311  of the repair portion  300  overlaps the semiconductor light emitting diode in which the assembly defect has occurred. However, the hole does not necessarily overlap the semiconductor light emitting diode in which the assembly defect has occurred. 
     Next, referring to  FIG.  14 B , in a state where the hole  311  is sufficiently adjacent to the semiconductor light emitting diode  1150 ′ in which the assembly defect has occurred, a step of suctioning the fluid through the hole  311  by the repair portion  300  is performed. When the fluid is suctioned, care must be taken not to affect the normally assembled semiconductor light emitting diodes. A method of minimizing the influence of the surrounding by fluid suction will be described below. 
     Meanwhile, referring to  FIG.  14 C , the controller controls the fluid controller  340  so that the fluid is suctioned into the inner space of the body portion until the semiconductor light emitting diode  1150  ‘ in which the assembly defect has occurred is adsorbed on the upper surface of the body portion. The semiconductor light emitting diode  1150 ’ in which the assembly defect has occurred is adsorbed to the body portion while overlapping the hole. In this state, when the fluid controller  340  additionally suctions the fluid, the semiconductor light emitting diode in which the assembly defect has occurred may be strongly fixed on the body portion. In this state, the controller transfers the repair portion  300  to recover the semiconductor light emitting diode in which the assembly defect has occurred. The recovered semiconductor light emitting diode may be recycled for self-assembly or disposed of. 
     Meanwhile, the repair portion  300  may be used in a state where an electric field is formed on the board. Accordingly, an electric force acts on the semiconductor light emitting diode seated on the board. The repair portion should suction the fluid so that a suction force sufficient to offset the electric force acts. 
     Meanwhile, some semiconductor light emitting diodes separated from the board by the repair portion  300  may be semiconductor light emitting diodes in which the assembly defect has occurred or damaged semiconductor light emitting diodes. As described in  FIGS.  13 A to  13 D , the semiconductor light emitting diode in which the assembly defect has occurred may be at least one of a semiconductor light emitting diode that is not seated in a predetermined position, a semiconductor light emitting diode disposed having a second surface facing the board, and a light emitting device having a first surface disposed at an angle to the board. 
     Meanwhile, when some of the semiconductor light emitting diodes are separated from the board, the positions of the some of the semiconductor light emitting diodes are left as empty spaces. The processes of  FIGS.  8 A to  8 E  may be performed once more so that a new semiconductor light emitting diode is seated in the empty space. As a result, all of the semiconductor light emitting diodes are disposed in a predetermined positions and orientation as shown in  FIG.  14 D . 
     According to the present disclosure, since the incorrectly assembled semiconductor light emitting diode is separated from the board by suctioning the fluid, even if the semiconductor light emitting diode is separated from the board, the semiconductor light emitting diode is not damaged and can be recycled. In addition, according to the present disclosure, since the fluid suctioned into the repair portion has little influence on the board, there is no risk of damage to the board in the process of separating the semiconductor light emitting diode from the board. 
     Meanwhile, the present disclosure provides a method of minimizing the influence of the surrounding by the fluid suction of the repair portion. 
       FIGS.  15  and  16    are conceptual views illustrating a method of minimizing the influence of the surrounding by the fluid suction of the repair portion. 
     Specifically, referring to  FIG.  15   , in the present disclosure, before the fluid is suctioned through the repair portion  300 , using the repair portion  300  the semiconductor light emitting diodes normally assembled are strongly fixed on the board. The controller controls the position adjusting portion so that the hole overlaps the other semiconductor light emitting diode  1150 ″ adjacent to the semiconductor light emitting diode in which the assembly defect has occurred before the fluid is suctioned into the inner space of the body portion. 
     In a state where the hole overlaps the other semiconductor light emitting diode, the fluid controller  340  is controlled so that the fluid is sprayed through the hole. Thereafter, the controller controls the fluid controller  340  so that the fluid is sprayed through the hole while the hole overlaps the other semiconductor light emitting diode  1150 ″. In this case, it is preferable that the hole and the other semiconductor light emitting diode  1150 ″ completely overlap. 
     When the fluid is sprayed in a state where the hole and the other semiconductor light emitting diode  1150 ″ completely overlap, the fluid is vertically sprayed to the other semiconductor light emitting diode  1150 ″. In this case, the sprayed fluid does not separate the other semiconductor light emitting diode  1150 ″ from the board, but strongly fixes the other semiconductor light emitting diode  1150 ″ to the board. When the fluid is sprayed on the semiconductor light emitting diodes surrounding the semiconductor light emitting diode in which the assembly defect has occurred, the surrounding semiconductor light emitting diodes are strongly fixed to the board, so that the influence of fluid suction can be minimized. 
     In one embodiment, referring to  FIG.  16   , based on the semiconductor light emitting diode  1250 ′ in which the assembly defect has occurred, the fluid is sprayed onto the semiconductor light emitting diodes  1250   a  to  1250   d  disposed on the top, bottom, left and right sides, and thus the semiconductor light emitting diodes  1250   a  to  1250   d  may be strongly fixed on the board. Through this, the present disclosure minimizes the influence of fluid suction. 
     As described above, according to the present disclosure, by spraying a fluid to the semiconductor light emitting diode disposed around the semiconductor light emitting diode in which the assembly defect has occurred, the semiconductor light emitting diode disposed around the semiconductor light emitting diode in which the assembly defect has occurred is strongly fixed on the board. Through this, the present disclosure can minimize the influence of the fluid suction of the repair portion.