Patent Publication Number: US-2023135290-A1

Title: Display device using semiconductor light-emitting diodes, and method for manufacturing same

Description:
TECHNICAL FIELD 
     The present disclosure relates to a display device using semiconductor light-emitting diodes, and one particular implementation relates to a display device using semiconductor light-emitting diodes having a size of several to several tens of μm. 
     BACKGROUND ART 
     In recent years, in the field of display technology, liquid-crystal displays (LCDs), organic light-emitting diodes (OLED) displays, microLED displays, etc. have been competing to realize large-area displays. 
     Semiconductor light-emitting diodes (microLEDs) with a diameter or cross-sectional area less than 100 μm, when used in displays, may offer very high efficiency because the displays do not need a polarizer to absorb light. However, large-scale displays require several millions of semiconductor light-emitting diodes, which makes it difficult to transfer the devices compared to other technologies. 
     Some of the technologies currently in development for the transfer process include pick &amp; place, laser lift-off (LLO), and self-assembly. Among these technologies, the self-assembly approach is a method that allows semiconductor light-emitting diodes to find their positions on their own in a fluid, which is most advantageous in realizing large-screen display devices. 
     Self-assembly methods may include a method of directly assembling a semiconductor light-emitting element on a final substrate to be used in a product, and a method of assembling a semiconductor light-emitting element on an assembly substrate and transferring the semiconductor light-emitting element to a final substrate through an additional transfer process. The direct assembly method on the final substrate is efficient in terms of process, and the method using the assembly substrate is advantageous in terms of additionally using a structure for self-assembly without limitation. Therefore, the two methods are selectively used. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The present disclosure is directed to providing an active matrix-type display device to where a structure for self-assembly of a semiconductor light-emitting diodes is added. In particular, the present disclosure is directed to providing a display device capable of operating stably even if a structure for assembly is added to it. 
     Furthermore, the present disclosure is directed to providing a method for manufacturing the above display device. 
     Solution to Problem 
     A display according to the present disclosure may include: a base unit; a data wire and a gate wire arranged in columns and rows, respectively, on the base unit so as to intersect each other; 
     a power wire extending in the same direction as the data wire and disposed between two adjacent data wires; thin film transistors connected to the data wire and gate wire; a semiconductor light-emitting diode operating in connection with the thin film transistors; and a pair of residual assembly electrodes overlapping the semiconductor light-emitting diode. 
     According to the present disclosure, the pair of residual assembly electrodes may be formed in such a way as not to overlap the data wire and the power wire. 
     According to the present disclosure, the pair of residual assembly electrodes may include: a first residual assembly electrode protruding toward the semiconductor light-emitting diodes on the side of the data wire; and a second residual assembly electrode protruding toward the semiconductor light-emitting diodes on the side of the power wire. 
     According to the present disclosure, the display device may include: a first insulating layer disposed between the data wire and the power wire and the pair of residual assembly electrodes; a second insulating layer disposed between the pair of residual assembly electrodes and the semiconductor light-emitting diode; and a third insulating layer disposed to cover the semiconductor light-emitting diode. 
     According to the present disclosure, the data wire and the power wire may include: a first area overlapping the first insulating layer; and a second area overlapping the first insulating layer, the second insulating layer, and the third insulating layer. 
     A method for manufacturing a display device according to the present disclosure may include the steps of: (a) forming a data wire and a gate wire arranged in columns and rows, respectively, on a base unit so as to intersect each other, a power wire extending in the same direction as the data wire, and thin-film transistors connected to the data wire and the gate wire; (b) forming an assembly electrode in such a way as to extend in the same direction as the data wire, with an extension overlapping either the data wire or the power wire; (c) seating a semiconductor light-emitting diode in a preset position by applying a voltage signal to the assembly electrode; and (d) removing the extension of the assembly electrode. 
     According to the present disclosure, the base unit may include a pair of residual assembly electrodes which is left thereon after the removal of the assembly electrode, wherein the pair of residual assembly electrodes overlap the semiconductor light-emitting diode. 
     According to the present disclosure, the pair of residual assembly electrodes may include: a first residual assembly electrode protruding toward the semiconductor light-emitting diodes on the side of the data wire; and a second residual assembly electrode protruding toward the semiconductor light-emitting diodes on the side of the power wire. 
     According to the present disclosure, the step (a) may include forming a first insulating layer covering the data wire and the gate wire, the step (b) may include forming a second insulating layer covering the assembly electrode, and the step (c) may include seating the semiconductor light-emitting diode in a preset position and then forming a third insulating layer covering the semiconductor light-emitting diode. 
     According to the present disclosure, the step of forming a third insulating layer may be carried out after masking an area of overlap between the data wire and the assembly electrode and an area of overlap between the power wire and the assembly electrode. 
     According to the present disclosure, the step (d) may include: selectively etching the second insulating layer which is formed in the area of overlap between the data wire and the assembly electrode and the area of overlap between the power wire and the assembly electrode; and etching the extension of the assembly electrode which overlaps either the data wire or the power wire. 
     Advantageous Effects of Invention 
     A display device according to the present disclosure has the effect of leaving a final structure that only includes a pair of residual assembly electrodes by removing an extension of an assembly electrode that overlaps a data wire or a power wire, and therefore reducing parasitic capacitance created by the overlap between the assembly electrode and the data wire or the power wire, thereby enabling stable operation. 
     Furthermore, a display device according to the present disclosure has a structure in which an assembly electrode is added onto an active matrix-type panel, and provides efficiency in terms of the manufacturing method, since employs an existing active matrix-panel manufacturing method and does not require semiconductor light-emitting diodes to be temporarily transferred onto a separate substrate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a conceptual view illustrating one implementation of a display device using semiconductor light-emitting elements. 
         FIG.  2    is a partial enlarged view of the portion A in the display device of  FIG.  1   . 
         FIG.  3    is an enlarged view of the semiconductor light-emitting element of  FIG.  2   . 
         FIG.  4    is an enlarged view illustrating another implementation of the semiconductor light-emitting element of  FIG.  2   . 
         FIGS.  5 A to  5 E  are conceptual diagrams illustrating a new process for manufacturing the semiconductor light-emitting element. 
         FIG.  6    is a conceptual diagram illustrating an example of a device for self-assembling semiconductor light-emitting elements. 
         FIG.  7    is a block diagram of the self-assembly device of  FIG.  6   . 
         FIGS.  8 A to  8 E  are conceptual view illustrating a process for self-assembling semiconductor light-emitting elements using the self-assembly device of  FIG.  6   . 
         FIG.  9    is a conceptual view illustrating the semiconductor light-emitting element of  FIGS.  8 A to  8 E . 
         FIG.  10    is a conceptual diagram showing a structure in which assembly electrodes are added to a conventional active matrix-type display panel. 
         FIG.  11    is a cross-sectional view taken along the line A-A′ of  FIG.  10   . 
         FIG.  12    is a graph showing measurements of parasitic capacitance in the structure of  FIG.  11   . 
         FIG.  13    is a conceptual diagram showing a structure of an active matrix-type display panel according to the present disclosure. 
         FIG.  14    is a cross-sectional view taken along the line B-B′ and line C-C″ of  FIG.  13   . 
         FIG.  15    is a conceptual diagram showing the semiconductor light-emitting diode of  FIG.  13    in a non-assembled state. 
         FIGS.  16 A to  16 C  are conceptual diagrams for explaining a process of manufacturing a structure in which an assembly electrode, a data wire, and a power wire do not overlap. 
     
    
    
     MODE FOR THE INVENTION 
     Description will now be given in detail according to exemplary implementations disclosed herein, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components may be provided with the same or similar reference numbers, and description thereof will not be repeated. In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to give any special meaning or function. In describing the present disclosure, if a detailed explanation for a related known function or construction is considered to unnecessarily divert the gist of the present disclosure, such explanation has been omitted but would be understood by those skilled in the art. The accompanying drawings are used to help easily understand the technical idea of the present disclosure and it should be understood that the idea of the present disclosure is not limited by the accompanying drawings. Furthermore, it will be understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the another element or an intermediate element may also be interposed therebetween. 
     A display device disclosed herein may include a portable (mobile) phone, a smart phone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation, a slate PC, a tablet PC, an ultrabook, a digital TV, a desktop computer, and the like. However, the configuration according to the implementation described herein can be applied as long as it can include a display even in a new product form to be developed later. 
       FIG.  1    is a conceptual view illustrating one implementation of a display device using semiconductor light-emitting elements (or diodes),  FIG.  2    is a partial enlarged view of the portion A in the display device of  FIG.  1   ,  FIG.  3    is an enlarged view of the semiconductor light-emitting element of  FIG.  2   , and  FIG.  4    is an enlarged view illustrating another implementation of the semiconductor light-emitting element of  FIG.  2   . 
     As illustrated, information processed by a controller of a display device  100  may be output on a display module  140 . A closed loop-shaped case  101  that runs around the edge of the display module  140  may define the bezel of the display device. 
     The display module  140  may include a panel  141  that displays an image, and the panel  141  may include micro-sized semiconductor light-emitting elements (or diodes)  150  and a wiring substrate  110  where the semiconductor light-emitting elements  150  are mounted. 
     The wiring substrate  110  may be provided with wirings, which can be connected to n-type electrodes  152  and p-type electrodes  156  of the semiconductor light-emitting elements  150 . As such, the semiconductor light-emitting elements  150  may be provided on the wiring substrate  110  as individual pixels that emit light on their own. 
     The image displayed on the panel  141  may be visual information, which is rendered by controlling the light emission of unit pixels (sub-pixels) arranged in a matrix configuration independently through the wirings. 
     The present disclosure takes microLEDs (light-emitting diodes) as an example of the semiconductor light-emitting elements  150  which convert current into light. The microLEDs may be light-emitting elements that are small in size less than 100 micron meters. The semiconductor light-emitting elements  150  may have light-emitting regions of red, green, and blue, and unit pixels may be produced by combinations of these colors. That is, the unit pixels are the smallest units for producing one color. Each unit pixel may contain at least three microLEDs. 
     More specifically, referring to  FIG.  3   , the semiconductor light-emitting element  150  may have a vertical structure. 
     For example, each of the semiconductor light-emitting elements  150  may be implemented with a high-power light emitting device that emits various lights including blue in which gallium nitride (GaN) is mostly used, and indium (In) and or aluminum (Al) are added thereto. 
     The vertical type semiconductor light emitting device includes 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  at the bottom may be electrically connected to a p-electrode of the wiring substrate, and the upper n-type electrode  152  at the top may be electrically connected to an n-electrode above the semiconductor light-emitting element. The electrodes can be disposed in an upward/downward direction in the vertical semiconductor light-emitting element  150 , thereby providing a great advantage of reducing a chip size. 
     In another example, referring to  FIG.  4   , the semiconductor light-emitting elements may be flip chip-type light-emitting elements. 
     As an example of such a flip chip-type light-emitting element, the semiconductor light-emitting element  250  may include a p-type electrode  256 , a p-type semiconductor layer  255  disposed on the p-type layer  256 , an active layer  254  disposed on the p-type semiconductor layer  255 , an n-type semiconductor layer  253  disposed on the active layer  254 , and an n-type electrode  252  vertically separated from the p-type electrode  256  on the n-type semiconductor layer  253 . In this case, both the p-type electrode  256  and the n-type electrode  252  may be electrically connected to a p electrode and an n electrode of the wiring substrate, below the semiconductor light-emitting element. 
     The vertical semiconductor light-emitting element and a horizontal light-emitting element each may be used as a green semiconductor light-emitting element, blue semiconductor light-emitting element, or red semiconductor light-emitting element. The green semiconductor light-emitting element and the blue semiconductor light-emitting element may be implemented as high-power light-emitting elements that are composed mostly of gallium nitride (GaN), with some indium (In) and/or aluminum (Al) added to it, and emit green and blue light, respectively. As an example, the semiconductor light-emitting elements may be made of gallium nitride thin films which include various layers of n-Gan, p-GaN, AlGaN, InGaN, etc. More specifically, the p-type semiconductor layer may be P-type GaN, and the n-type semiconductor layer may be N-type GaN. However, for the red semiconductor light-emitting element, the p-type semiconductor layer may be P-type GaAs, and the n-type semiconductor layer may be N-type GaAs. 
     Moreover, the p-type semiconductor layer may be P-type GaN doped with Mg on the p electrode, and the n-type semiconductor layer may be N-type GaN doped with Si on the n electrode. In this case, the above-described semiconductor light-emitting elements may be semiconductor light-emitting elements without the active layer. 
     In some examples, referring to  FIGS.  1  to  4   , because of the very small size of the light-emitting elements, self-emissive, high-definition unit pixels may be arranged on the display panel, and therefore the display device can deliver high picture quality. 
     In the display device using the semiconductor light-emitting elements, semiconductor light-emitting elements may be grown on a wafer, formed through mesa and isolation, and used as individual pixels. In this case, the micro-sized semiconductor light-emitting elements  150  should be transferred onto a wafer, at preset positions on a substrate of the display panel. One of the transfer technologies available may be pick and place, but it has a low success rate and requires a lot of time. In another example, a number of diodes may be transferred at a time by using a stamp or roll, which, however, is not suitable for large-screen displays because of limited yields. The present disclosure proposes a new method and device for manufacturing a display device that can solve these problems. 
     To this end, a new method for manufacturing a display device will be described first below.  FIGS.  5 A to  5 E  are conceptual views illustrating a new process for manufacturing the semiconductor light-emitting elements (or diodes). 
     In this specification, a display device using passive matrix (PM) type semiconductor light-emitting elements will be illustrated. However, an example described below may also be applicable to an active matrix (AM) type semiconductor light-emitting element. Also, although the illustration will be given of how horizontal semiconductor light-emitting elements are self-assembled, it may also be applied to self-assembling of vertical semiconductor light-emitting elements. 
     First of all, according to the manufacturing method, a first conductive semiconductor layer  153 , an active layer  154 , and a second conductive semiconductor layer  155  may be grown on a growth substrate  159  ( FIG.  5 A ). 
     Once the first conductive semiconductor layer  153  is grown, the active layer  154  may be grown on the first conductive semiconductor layer  153  and then the second conductive semiconductor layer  155  may be grown on the active layer  154 . By sequentially growing the first conductive semiconductor layer  153 , the active layer  154 , and the second conductive semiconductor layer  155 , the first conductive semiconductor layer  153 , the active layer  154 , and the second conductive semiconductor layer  155  may form a stack structure as illustrated in  FIG.  5 A . 
     In this case, the first conductive semiconductor layer  153  may be a p-type semiconductor layer, and the second conductive semiconductor layer  155  may be an n-type semiconductor layer. However, the present invention is not necessarily limited thereto, and may employ an example in which the first conductive electrode is the n-type and the second conductive electrode is the p-type. 
     Moreover, although this exemplary implementation is illustrated by assuming the presence of the active layer, the active layer may be omitted if necessary, as stated above. In 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. 
     The growth substrate  159  (wafer) may be formed of, but not limited to, light-transmissive material, for example, one of sapphire (Al2O3), GaN, ZnO, and AlO. In addition, the growth substrate  1059  may be made of a material suitable for growing a semiconductor material, namely, a carrier wafer. The growth substrate  2101  may also be formed of a material having high thermal conductivity. The growth substrate  2101  may use at least one of a SiC substrate having higher thermal conductivity than the sapphire (Al2O3) substrate, Si, GaAs, GaP, InP and Ga2O3, in addition to a conductive substrate or an insulating substrate. 
     Next, a plurality of semiconductor light-emitting elements may be formed by removing at least parts of the first conductive semiconductor layer  153 , the active layer  154 , and the second conductive semiconductor layer  155  ( FIG.  5 B ). 
     More specifically, isolation may be performed so that the plurality of light-emitting elements form a light-emitting diode array. That is, a plurality of semiconductor light-emitting elements may be formed by vertically etching the first conductive semiconductor layer  153 , the active layer  154 , and the second conductive semiconductor layer  155 . 
     In the case of horizontal semiconductor light-emitting elements, a mesa process may be performed which exposes the first conductive semiconductor layer  153  to the outside by vertically removing part of the active layer  154  and the second conductive semiconductor layer  155 , and then isolation may be performed which forms an array of semiconductor light-emitting elements by etching the first conductive semiconductor layer  153 . 
     Next, a second conductive electrode  156  (or p-type electrode) may be formed on one surface of the second conductive semiconductor layer  155  ( FIG.  5 C ). The second conductive electrode  156  may be formed by a deposition method such as sputtering, but the present disclosure is not necessarily limited to this. In a case where 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 conductive electrode  156  may serve as an n-type electrode. 
     Next, the growth substrate  159  may be removed, thus leaving a plurality of semiconductor light-emitting elements. For example, the growth substrate  1059  may be removed using laser lift-off (LLO) or chemical lift-off (CLO) ( FIG.  5 D ). 
     Afterwards, the step of mounting the semiconductor light-emitting elements  150  on a substrate in a chamber filled with a fluid may be performed ( FIG.  5 E ). 
     For example, the semiconductor light-emitting elements  150  and the substrate  161  may be put into a chamber filled with a fluid, and the semiconductor light-emitting elements may be self-assembled onto the substrate  161  using fluidity, gravity, surface tension, etc. In this case, the substrate may be an assembly substrate  161 . 
     In another example, a wiring substrate, instead of the assembly substrate  161 , may be put into a fluid chamber, and the semiconductor light-emitting elements  150  may be mounted directly onto the wiring substrate. In this case, the substrate may be a wiring substrate. For convenience of explanation, the present disclosure is illustrated with an example in which the semiconductor light-emitting elements  150  are mounted onto the assembly substrate  161 . 
     To facilitate the mounting of the semiconductor light-emitting elements  150  onto the assembly substrate  161 , cells (not shown) into which the semiconductor light-emitting elements  150  are fitted may be provided on the assembly substrate  161 . Specifically, cells where the semiconductor light-emitting elements  150  are mounted may be disposed on the assembly substrate  161  at positions where the semiconductor light-emitting elements  150  are aligned to with wiring electrodes. The semiconductor light-emitting elements  150  may be assembled to the cells as they move within the fluid. 
     After arraying the semiconductor light-emitting elements  150  on the assembly substrate  161 , the semiconductor light-emitting elements  150  may be transferred to the wiring substrate from the assembly substrate  161 , thereby enabling a large-area transfer across a large area. Thus, the assembly substrate  161  may be referred to as a temporary substrate. 
     Meanwhile, the above-explained self-assembly method requires a higher transfer yield so that it can be applied to the manufacture of large-screen displays. The present disclosure proposes a method and device that minimizes the effects of gravity or friction and avoids 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 may be placed on the semiconductor light-emitting elements so that the semiconductor light-emitting elements are moved by magnetic force, and the semiconductor light-emitting elements may be mounted at preset positions by an electric field in the process of being moved. This transfer method and device will be described in more detail below with reference to the accompanying drawings. 
       FIG.  6    is a conceptual diagram illustrating an example of a device for self-assembling semiconductor light-emitting elements and  FIG.  7    is a block diagram of the self-assembly device of  FIG.  6   .  FIGS.  8 A to  8 E  are conceptual view illustrating a process for self-assembling semiconductor light-emitting elements using the self-assembly device of  FIG.  6    and  FIG.  9    is a conceptual view illustrating the semiconductor light-emitting element of  FIGS.  8 A to  8 E . 
     Referring to  FIGS.  6  and  7   , the self-assembly device  160  may include a fluid chamber  162 , a magnet  163 , and a position controller  164 . 
     The fluid chamber  162  may define a space for receiving a plurality of semiconductor light-emitting elements. The space may be filled with a fluid, and the fluid may be an assembly solution, which includes water or the like. Thus, the fluid chamber  162  may be a water tank and configured as an open-type. However, the present disclosure is not limited to this, and the fluid chamber  162  may be a closed-type chamber in which the space is in a closed state. 
     A substrate  161  may be placed in the fluid chamber  162  so that an assembly surface where the semiconductor light-emitting elements  150  are assembled faces downwards. For example, the substrate  161  may be fed to an assembly site by a feed unit (transfer unit), and the transfer unit may include a stage  165  where the substrate is mounted. The position of the stage  165  may be adjusted by the controller, whereby the substrate  161  can be fed to the assembly site. 
     In this instance, the assembly surface of the substrate  161  at the assembly site may face the bottom of the fluid chamber  162 . As illustrated in the drawings, the assembly surface of the substrate  161  may be placed to be soaked with the fluid in the fluid chamber  162 . Thus, the semiconductor light-emitting elements  150  in the fluid may be moved to the assembly surface. 
     The substrate  161  may be an assembly substrate where an electric field can 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 made of an insulating material, and the plurality of electrodes  161   c  may be thin-film or thick-film bi-planar electrodes that are patterned on one surface of the base portion  161   a . The electrodes  161   c  may be formed of a stack of Ti/Cu/Ti, Ag paste, ITO, etc. 
     The dielectric layer  161   b  is made of an inorganic material such as SiO2, SiNx, SiON, Al2O3, TiO2, HfO2, or the like. Alternatively, the dielectric layer  161   b  may be made of a single layer or multiple layers as an organic insulator. A thickness of the dielectric layer  161   b  may be several tens of nanometers (nm) to several micrometers (μm). 
     In addition, the substrate  161  may include a plurality of cells  161   d  that are partitioned by barrier walls. The cells  161   d  may be sequentially arranged in one direction and made of a polymer material. Furthermore, the barrier walls  161   e  defining the cells  161   d  may be made to be shared with neighboring cells  161   d . The barrier walls  161   e  may protrude from the base portion  161   a , and the cells  161   d  may be sequentially arranged in one direction by the barrier walls  161   e . More specifically, the cells  161   d  may be sequentially arranged in column and row directions and have a matrix configuration. 
     As illustrated in the drawings, the cells  161   d  may have recesses for receiving the semiconductor light-emitting elements  150 , and the recesses may be spaces defined by the barrier walls  161   e . The recesses may have a shape identical or similar to the shape of the semiconductor light-emitting elements. For example, if the semiconductor light-emitting elements are rectangular, the recesses may be rectangular too. In addition, although not shown, when the semiconductor light-emitting element has a circular shape, grooves formed inside the cells may be formed in a circular shape. Moreover, each of the cells is configured to accommodate a single semiconductor light-emitting element. In other words, a single semiconductor light-emitting element is accommodated in a single cell. 
     Meanwhile, the plurality of electrodes  161   c  may have a plurality of electrode lines that are placed on bottoms of the cells  161   d , and the plurality of electrode lines may extend to neighboring cells. 
     The plurality of electrodes  161   c  may be placed beneath the cells  161   d , and different polarities may be applied to create an electric field within the cells  161   d . To form an electric field, the dielectric layer  161   b  may form the bottom of the cells  161   d  while covering the electrodes  161   c . With this structure, when different polarities are applied to a pair of electrodes  161   c  beneath each cell  161   d , an electric field may be formed and the semiconductor light-emitting elements can be inserted into the cells  161   d  by the electric field. 
     The electrodes of the substrate  161  at the assembly site may be electrically connected to a power supply unit  171 . The power supply unit  171  may perform the function of generating the electric field by applying power to the electrodes. 
     As shown in the drawings, the self-assembly device may have the magnet  163  for applying magnetic force to the semiconductor light-emitting elements. The magnet  163  may be disposed at a distance from the fluid chamber  162  to apply magnetic force to the semiconductor light-emitting elements  150 . The magnet  163  may be disposed to face an opposite side of the assembly surface of the substrate  161 , and the position of the magnet  163  may be controlled by the position controller  164  connected to the magnet  163 . 
     The semiconductor light-emitting elements  1050  may have a magnetic material so that they can be moved within the fluid by a magnetic field. 
     Referring to  FIG.  9   , a semiconductor light-emitting element having a magnetic material may include a first conductive electrode  1052 , a second conductive electrode  1056 , a first conductive semiconductor layer  1053  on which the first conductive electrode  1052  is disposed, a second conductive semiconductor layer  1055  which overlaps the first conductive semiconductor layer  1052  and on which the second conductive electrode  1056  is disposed, and an active layer  1054  disposed between the first and second conductive semiconductor layers  1053  and  1055 . 
     Here, the first conductive may refer to p-type, and the second conductive type may refer to n-type, or vice versa. As stated previously, the semiconductor light-emitting diode may be formed without the active layer. 
     Meanwhile, the first conductive electrode  1052  may be formed after the semiconductor light-emitting element is assembled onto the wiring substrate by the self-assembling of the semiconductor light-emitting element. Further, the second conductive electrode  1056  may include a magnetic material. The magnetic material may refer a magnetic metal. The magnetic material may be Ni, SmCo, etc. In another example, the magnetic material may include at least one of Gd-based, La-based, and Mn-based materials. 
     The magnetic material may be provided in the form of particles on the second conductive electrode  1056 . Alternatively, one layer of a conductive electrode including a magnetic material may be made of the magnetic material. As an example, the second conductive electrode  1056  of the semiconductor light-emitting element  1050  may include a first layer  1056   a  and a second layer  1056   b , as illustrated in  FIG.  9   . Here, the first layer  1056   a  may include a magnetic material, and the second layer  1056   b  may include a metal material other than the magnetic material. 
     As illustrated in the drawing, in this example, the first layer  1056   a  including the magnetic material may be disposed in contact with the second conductive semiconductor layer  1055 . In this case, the first layer  1056   a  may be disposed between the second layer  1056   b  and the second conductive semiconductor layer  1055 . The second layer  1056   b  may be a contact metal that is connected to the second electrode on the wiring substrate. However, the present disclosure is not necessarily limited to this, and the magnetic material may be disposed on one surface of the first conductive semiconductor layer. 
     Still referring to  FIGS.  6  and  7   , more specifically, on top of the fluid chamber of the self-assembly device, a magnet handler capable of automatically or manually moving the magnet  163  on the x, y, and z axes or a motor capable of rotating the magnet  163  may be provided. The magnet handler and motor may constitute the position controller  164 . As such, the magnet  163  may rotate in a horizontal, clockwise, or counterclockwise direction with respect to the substrate  161 . 
     Meanwhile, the fluid chamber  162  may be provided with a light-transmissive bottom plate  166 , and the semiconductor light-emitting elements may be disposed between the bottom plate  166  and the substrate  161 . An image sensor  167  may be disposed to face the bottom plate  166  so as to monitor the inside of the fluid chamber  162  through the bottom plate  166 . The image sensor  167  may be controlled by a controller  172 , and may include an inverted-type lens, CCD, etc. so as to observe the assembly surface of the substrate  161 . 
     The self-assembly device may be configured to use a magnetic field and an electric field in combination. With this, the semiconductor light-emitting elements can be mounted at preset positions on the substrate by the electric field while being moved by changes in the position of the magnet. Hereinafter, the assembly process using the self-assembly device will be described in more detail. 
     First of all, a plurality of semiconductor light-emitting elements  1050  having a magnetic material may be formed through the process explained with reference to  FIGS.  5 A to  5 C . In this case, the magnetic material may be deposited onto the semiconductor light-emitting elements in the process of forming the second conductive electrode of  FIG.  5 C . 
     Next, the substrate  161  may be fed to an assembly site, and the semiconductor light-emitting elements  1050  may be put into the fluid chamber  162  ( FIG.  8 A ). 
     As described above, the assembly site on the substrate  161  may be a position at which the substrate  161  is placed in the fluid chamber  162  in such a way that an assembly surface where the semiconductor light-emitting elements  150  are assembled faces downwards. 
     In this case, some of the semiconductor light-emitting elements  1050  may sink to the bottom of the fluid chamber  162  and some of them may float in the fluid. When the fluid chamber  162  is provided with the light-transmissive bottom plate  166 , some of the semiconductor light-emitting elements  1050  may sink to the bottom plate  166 . 
     Next, magnetic force may be applied to the semiconductor light-emitting elements  1050  so that the semiconductor light-emitting elements  1050  in the fluid chamber  162  come up to the surface ( FIG.  8 B ). 
     When the magnet  163  of the self-assembly device moves to the opposite side of the assembly surface of the substrate  161  from its original position, the semiconductor light-emitting elements  1050  may float in the fluid towards the substrate  161 . The original position may refer to s position at which the magnet  163  is outside the fluid chamber  162 . As another example, the magnet  163  may be configured as an electromagnet. In this case, an initial magnetic force may be generated by supplying electricity to the electromagnet. 
     Meanwhile, in this implementation, the spacing between the assembly surface of the substrate  161  and the semiconductor light-emitting elements  1050  may be controlled by adjusting strength of the magnetic force. For example, the spacing may be controlled by using weight, buoyancy, and magnetic force of the semiconductor light-emitting elements  1050 . The spacing may be several millimeters to several tens of micrometers from the outermost part of the substrate  161 . 
     Next, magnetic force may be applied to the semiconductor light-emitting elements  1050  so that the semiconductor light-emitting elements  1050  can move in one direction within the fluid chamber  162 . For example, the magnet  163  may move in a horizontal direction to the substrate, a clockwise direction, or a counterclockwise direction ( FIG.  8 C ). In this case, the semiconductor light-emitting elements  1050  may be moved horizontally with respect to the substrate  161  by the magnetic force, with being spaced apart from the substrate  161 . 
     Next, the semiconductor light-emitting elements  1050  may be guided to preset positions on the substrate  161  by applying an electric field so that the semiconductor light-emitting elements  1050  are mounted at the preset positions during their movement ( FIG.  8 C ). For example, the semiconductor light-emitting elements  1050  may be moved vertically with respect to the substrate  161  by the electric field while being moved horizontally with respect to the substrate  161 , thereby being placed at the preset positions of the substrate  161 . 
     More specifically, an electric field may be generated by supplying power to bi-planar electrodes on the substrate  161 , and the semiconductor light-emitting electrodes  1050  may be guided to be assembled only at the preset positions by the electric field. That is, the semiconductor light-emitting elements  1050  may be self-assembled at the assembly site on the substrate  161  by a selectively generated electric field. To this end, the substrate  161  may be provided with cells into which the semiconductor light-emitting elements  1050  are fitted. 
     Afterwards, unloading of the substrate  161  may be performed, thereby completing the assembly process. In a case where the substrate  161  is an assembly substrate, the assembled semiconductor light-emitting elements may be transferred onto a wiring substrate to carry out a subsequent process for realizing the display device, as described previously. 
     Meanwhile, after the semiconductor light-emitting elements  1050  are guided to the preset positions, the magnet  163  may be moved away from the substrate  161  such that the semiconductor light-emitting elements  1050  remaining in the fluid chamber  162  fall to the bottom of the fluid chamber  162  ( FIG.  8 D ). In another example, when power supply is stopped in a case where the magnet  163  is an electromagnet, the semiconductor light-emitting elements  1050  remaining in the fluid chamber  162  may fall to the bottom of the fluid chamber  162 . 
     Thereafter, the semiconductor light-emitting elements  1050  on the bottom of the fluid chamber  162  may be collected, and the collected semiconductor light-emitting elements  1050  may be re-used. 
     In the above-explained self-assembly device and method, parts at far distances may be concentrated near a preset assembly site by using a magnetic field in order to increase assembly yields in a fluidic assembly, and guided to be selectively assembled only at the assembly site by applying an electric field to the assembly site. In this case, the assembly substrate may be positioned on top of a water tank, with its assembly surface facing downward, thereby minimizing the effect of gravity from the weights of the parts and avoiding non-specific binding and eliminating defects. That is, the assembly substrate may be placed on the top to increase transfer yields, thus minimizing the effect of gravity or friction and avoiding non-specific binding. 
     As seen from above, with the configuration, a large number of semiconductor light-emitting elements can be assembled at a time in a display device where individual pixels are made up of semiconductor light-emitting elements. 
     As such, a large number of semiconductor light-emitting elements can be pixelated on a small-sized wafer and then transferred onto a large-area substrate. This enables the manufacture of a large-area display device at a low cost. 
     Hereinafter, a display device using semiconductor light-emitting elements having a novel structure according to an implementation will be described with reference to the accompanying drawings. 
     A display device  2000  according to an embodiment of the present disclosure is an active matrix-type (hereinafter, AM-type) display device including an assembly electrode  2060  as a structure for self-assembling semiconductor light-emitting diodes—more specifically, including a pair of residual assembly electrodes  2061  and  2062  as part of the assembly electrodes. 
       FIG.  10    is a conceptual diagram showing a structure in which assembly electrodes are added to a conventional active matrix-type display panel.  FIG.  11    is a cross-sectional view taken along the line A-A′ of  FIG.  10   .  FIG.  12    is a graph showing measurements of parasitic capacitance in the structure of  FIG.  11   . 
     The AM-type display device (or display device)  200  may have a data wire  220  and a gate wire  230  arranged on a base unit  210 . The data wire  220  and the gate wire  230  may extend in different directions and intersect each other. 
     The base unit  210  may further include wires Vss and Vdd. The Vdd wire (hereinafter, a power wire  240 ) may extend in the same direction as the data wire  220 . 
     Thin-film transistors (a switching thin-film transistor  250   s  and a driving thin-film transistor  250   d ) and a storage capacitor, including a semiconductor light-emitting diode  270 , may be disposed in an area defined by an intersection of the data wire  220  and the gate wire  230 . 
     The thin-film transistors  250  each include a gate electrode, an active layer, a source electrode, and a drain electrode, and may be classified into a-Si type and LTPS type whose active layer is formed of silicon and oxide type whose active layer is formed of oxide, depending on the material of the active layer. Among them, the oxide type is suitable for large-sized displays such as PCs and TVs, since its active layer is formed of an IGZO (indium, gallium, zinc, and oxygen) compound. 
     The semiconductor light-emitting diode  270  may be electrically connected to the thin-film transistors  250  by a connecting electrode  280 . The connecting electrode  280  may be formed to extend from an electrode of the semiconductor light-emitting diode  270  and fill a via hole H exposing the gate electrode or drain electrode of a thin-film transistor  250  and electrically connect the semiconductor light-emitting diode  270  and the thin-film transistor  250 . 
     Conventionally, in order to assembly a semiconductor light-emitting diode  270  that is several to several tens of μm in size to an AM-type display device  200 , a semiconductor light-emitting diode  270  is assembled through self-assembly to a donor substrate with assembly electrodes formed on it, and then the semiconductor light-emitting diode  270  is transferred from an assembly substrate to a substrate with thin-film transistors  250  and wires formed on it, by using PDMS stamps. 
     Meanwhile, in order to self-assemble a semiconductor light-emitting diode  270  to a substrate with thin-film transistors  250  and wires formed on it, an assembly electrode  260  needs to be added to receive a voltage signal for forming an electrical field, in which case it is necessary for the assembly electrode  260  to extend in the same direction as the data wire  220  and the power wire  240 . Accordingly, the assembly electrode  260  may overlap the data wire  220  (or the power wire  240 ), with an insulating layer  211  formed of a dielectric material interposed in between. 
     However, such a structure is problematic in that it forms very high parasitic capacitance C between the assembly electrode  260  and the data wire  220  or the power wire  240  (see the graph of  FIG.  12   ). 
     The parasitic capacitance C causes RC delay, and distorts the waveform of the data wire  220 , thus deteriorating the operational stability of the display device. Specifically, when a voltage is applied to the data wire  220 , the assembly electrode  260  overlapping the data wire  220  electrically floats, and the voltage of the assembly electrode  260  continuously changes with the voltage of the data wire  220 . Thus, the capacitance also changes and therefore the operational stability of the display device  200  is deteriorated. 
     The present disclosure relates to an AM-type display device  2000  capable of operating stably even if assembly electrodes for self-assembly are added. 
       FIG.  13    is a conceptual diagram showing a structure of an active matrix-type display panel according to the present disclosure.  FIG.  14    is a cross-sectional view taken along the line B-B′ and line C-C″ of  FIG.  13   . 
     Referring to  FIG.  13   , the display device  2000  according to the present disclosure may include a data wire  2020 , a gate wire  2030 , a power wire  2040 , thin-film transistors  2050 , a pair of residual assembly electrodes  2061  and  2062 , and a semiconductor light-emitting diode  2070 , which are disposed on a base unit  2010 . 
     The base unit  2010  may include polyimide PI to achieve flexibility, and its material is not specifically limited as long as it provides insulation and flexibility. 
     The data wire  2020  and the gate wire  2030  may be disposed to intersect each other on the base unit  2010 . The data wire  2020  and the gate wire  2030  may be arranged in columns and rows and intersect each other, and may be separated by an insulating layer  2014 . 
     The power wire  2040  extending in the same direction as the data wire  2020  may be disposed on the base unit  2010 . The power wire  2040  may be disposed between two adjacent data wires  2020 , much closer to one of the two adjacent data wires  2020 . 
     Thin-film transistors  2050  and a storage capacitor, including a semiconductor light-emitting diode  2070 , may be disposed in an area defined by an intersection of the data wire  2020  and the gate wire  2030 . 
     The thin-film transistors  250  may be connected to the data wire  2020  and the gate wire  2030 . The semiconductor light-emitting diode  2070  may operate in connection with the thin-film transistors  2050 . The thin-film transistors  2050  may include a switching thin-film transistor  2050   s  and a driving thin-film transistor  2050   d . Meanwhile, the switching thin-film transistor  2050   s  and the driving thin-film transistor  2050   d  have the same structure and the same manufacturing process, which is a well-known technology, so a detailed description thereof will be omitted. 
     According to the present disclosure, the semiconductor light-emitting diode  2070  may be a horizontal semiconductor light-emitting diode  2070  with p-type and n-type electrodes formed on one side. The semiconductor light-emitting diode  2070  may be connected to the switching thin-film transistor  2050   s  and the driving thin-film transistor  2050   d.    
     The semiconductor light-emitting diode  2070  and the thin-film transistors  2050  may be electrically connected by a connecting electrode  2080 . The connecting electrode  2080  may be formed to extend from the p-type and n-type electrodes of the semiconductor light-emitting diode  2070  and fill a via hole H exposing the gate electrode or drain electrode of a thin-film transistor  2050  and electrically connect the semiconductor light-emitting diode  2070  and the thin-film transistor  2050 . 
     According to the present disclosure, a pair of residual assembly electrodes  2061  and  2062  may be disposed in an area defined by an intersection of the data wire  2020  and the gate wire  2030 . The pair of residual assembly electrodes  2061  and  2062  may overlap the semiconductor light-emitting diode  2070 . The pair of residual assembly electrodes  2061  and  2062  may be part of the assembly electrode  2060  added to self-assemble the semiconductor light-emitting diode  2070 . 
     According to the present disclosure, the pair of residual assembly electrodes  2061  and  2062  may be formed in such a way as not to overlap the data wire  2020  and the power wire  2040 . Specifically, in the present disclosure, the assembly electrode  2060  may be formed to include an extension  261  extending in the same direction as the data wire  2020  or the power wire  2040  and overlapping the same and a protrusion  262  protruding toward the semiconductor light-emitting diode  2070  without overlapping the data wire  2020  or the power wire  2040 , as shown in  FIG.  10   . After the self-assembly process, the extension  261  overlapping the data wire  2020  and the power wire  2040  may be removed. 
     The pair of residual assembly electrodes  2061  and  2062  may correspond to the protrusion  262  of the assembly electrode  2060  which does not overlap the data wire  2020  and the power wire  2040 . 
     That is, according to the present disclosure, the final display device  200  will only have the pair of residual assembly electrodes  2061  and  2062  left on it, which corresponds to the protrusion  262  not overlapping the data wire  2020  and the power wire  2040 . This eliminates or greatly reduces the parasitic capacitance formed when the display device  2000  is operated. 
     The pair of residual assembly electrodes  2061  and  2062  may include a first residual assembly electrode  2061  protruding toward the semiconductor light-emitting diode  2070  on the side of the data wire  2020  and a second residual assembly electrode  2062  protruding toward the semiconductor light-emitting diode  2070  on the side of the power wire  2040 . 
     Meanwhile, according to the present disclosure, a first insulating layer  2011  may be included which is disposed between the data wire  2020  and the power wire  2040  and the pair of residual assembly electrodes  2061  and  2062 . The first insulating layer  2011  may be for electrically separating the assembly electrode  2060  or the pair of residual assembly electrodes  2061  and  2062  from the data wire  2020  and the power wire  2040 . The first insulating layer  2011  may be formed of an inorganic insulating material such as SiO2, SiNx, SiON, Al2O3, TiO2, HfO2, etc., but not limited thereto. 
     Moreover, according to the present disclosure, a second insulating layer  2012  may be included which is disposed between the pair of residual assembly electrodes  2061  and  2062  and the semiconductor light-emitting diode  2070 . The second insulating layer  2012  may be formed on the entire surface of the substrate, but may be left only in some area in the end. The second insulating layer  2012  may be formed of an inorganic insulating material such as SiO2, SiNx, SiON, Al2O3, TiO2, HfO2, etc., but not limited thereto. 
     Moreover, according to the present disclosure, a third insulating layer  2013  may be included which is formed to cover the semiconductor light-emitting diode  2070 . The third insulating layer  2013  may be a layer for planarizing one surface of a substrate while filling space between semiconductor light-emitting diodes  2070 , and may be formed on some area of the substrate. The third insulating layer  2013  may have a thickness of several to several tens of μm, and be formed of an organic insulating material, for example. The third insulating layer  2013  may include a hole exposing part of the p-type and n-type electrodes of the semiconductor light-emitting diode  2070 . 
     According to the above-described structure including the first to third insulating layers  2011 ,  2012 , and  2013 , the data wire  2020  and the power wire  2040  may include a first area  2020   a  overlapping the first insulating layer  2011  and a second area  2020   b  overlapping the first insulating layer  2011 , the second insulating layer  2012 , and the third insulating layer  2013 . 
     Next, a method for manufacturing the above-described AM-type display device  2000  will be described with reference to  FIGS.  15  and  16   . 
       FIG.  15    is a conceptual diagram showing the semiconductor light-emitting diode of  FIG.  13    in a non-assembled state.  FIGS.  16 A to  16 C  are conceptual diagrams for explaining a process of manufacturing a structure in which an assembly electrode, a data wire, and a power wire do not overlap. 
     First, a step (a) of forming a plurality of wires and thin-film transistors  2050  on a base unit  2010  may be performed. Specifically, a data wire  2020  and a gate wire  2030  may be formed on a base unit  2010  and arranged in columns and rows, respectively, on the base unit  2010  and intersect each other, and a power wire  2040  may be formed to extend in the same direction as the data wire  2020 . Also, the thin-film transistors  2050  may be formed to be connected to the data wire  2020  and the gate wire  2030 . 
     For example, the step (a) may be carried out by sequentially performing a step of forming a gate wire  2030  and a gate electrode on a base unit  2010 , a step of forming a gate insulating film, a step of forming an active layer and an ohmic contact layer, a step of forming a data wire and a power wire, and a step of forming a source electrode and a drain electrode. 
     Also, the step (a) may include a step of forming a first insulating layer  2011  covering the data wire  2020  and the power wire  2040 , and the first insulating layer  2011  may be formed of an inorganic insulating material. 
     Next, a step (b) of forming an assembly electrode  2060  in such a way as to extend in the same direction as the data wire  2020 , with an extension overlapping either the data wire  2020  or the power wire  2040 . The assembly electrode  2060  may be formed on the first insulating layer  2011 . 
     The assembly electrode  2060  may include an extension  2060   a  overlapping either the data wire  2020  or the power wire  2040  and a protrusion  2060   b  protruding from the extension  2060   a  and not overlapping the data wire  2020  or the power wire  2040 . 
     The assembly electrode  2060  may be formed of a non-resistant metal such as Al, Mo, Cu, Ag, or Ti or an alloy composed of two or more types of non-resistant metal. Also, the assembly electrode  2060  may have a thickness of several or several tens of nm. 
     Moreover, the step (b) may include a step of forming a second insulating layer  2012  covering the assembly electrode  2060 , and the second insulating layer  2012  may be formed of an inorganic insulating material. 
     Next, a step (c) of seating a semiconductor light-emitting diode  2070  in a preset position by applying a voltage signal to the assembly electrode  2060 . The semiconductor light-emitting diode  2070  may be seated on the second insulating layer  2012 . Meanwhile, the step (c) may be a self-assembly process using a magnetic field and an electrical field according to  FIGS.  8 A to  8 E , and a detailed description thereof will be omitted. 
     In addition, the step (c) may include a step of forming a third insulating layer  2013  covering the semiconductor light-emitting diode  2070  after seating the semiconductor light-emitting diode  2070  in a preset position. The third insulating layer  2013  may be formed of an inorganic insulating material. 
     The third insulating layer  2013  may be formed on some area of the substrate. Specifically, the third insulating layer  2013  may be formed in areas excluding an area of overlap between the data wire  2020  and the assembly electrode  2060  and an area of overlap between the power wire  2040  and the assembly electrode  2060 . The area of overlap between the assembly electrode  2060  and the data wire  2020  or the power wire  2040  may be the extension  2060   a  of the assembly electrode  2060 . 
     Accordingly, the step of forming a third insulating layer  2013  may be carried out after masking an area of overlap between the data wire  2020  and the assembly electrode  2060  and an area of overlap between the power wire  2040  and the assembly electrode  2060 . According to the present disclosure, the portion of the assembly electrode  2060  that overlaps the data wire  2020  or the power wire  2040  needs to be removed in the end to prevent formation of parasitic capacitance. Thus, the third insulating layer  2013  may not be formed in this portion ( FIG.  16 A ). 
     Next, a step (d) of removing the extension  2060   a  of the assembly electrode  2060  may be performed. The step (d) may be performed in the process of forming a via hole H and a connecting electrode  2080  to electrically connect the semiconductor light-emitting diode  2070  and the thin-film transistors  2050 . 
     The step (d) may be carried out by sequentially performing a step ( FIG.  16 B ) of selectively etching the second insulating layer  2012  which is formed in the area of overlap between the data wire  2020  and the assembly electrode  2060  and the area of overlap between the power wire  2040  and the assembly electrode  2060 , and a step ( FIG.  16 C ) of etching the extension  2060   a  of the assembly electrode  2060  which overlaps either the data wire  2020  or the power wire  2040 . That is, in the step (d), the second insulating layer  2012  and the assembly electrodes  2060  may be etched from areas where the third insulating layer  2013  is not formed. 
     After the step (d) is completed, a pair of residual assembly electrodes  2061  and  2062  may be left on the base unit  2010 . That is, the pair of residual assembly electrodes  2061  and  2062  may be the protrusion  2060   b  which is left after the removal of the extension  2060   a  of the assembly electrode  2060 . 
     Meanwhile, a conductive material (for example, metal) may fill the via hole H, and may be connected to the p-type and n-type electrode of the semiconductor light-emitting diode  2070 , thereby electrically connecting the semiconductor light-emitting diode  2070  and the thin-film transistors  2050 . 
     The display device according to the present disclosure provides efficiency in terms of the manufacturing method, since it employs an existing active matrix-panel manufacturing method and does not require semiconductor light-emitting diodes to be temporarily transferred onto a separate substrate. 
     The present disclosure as set forth above is not limited to the configuration and method of the above-described embodiments, but all or some of the embodiments may be selectively combined to make various changes to the embodiments.