Patent Publication Number: US-2019172760-A1

Title: Micro lighting device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwan Application No. 106142619 filed on 2017 Dec. 5. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a micro lighting device, and more particularly, to a micro lighting device with repair mechanism. 
     2. Description of the Prior Art 
     Compared to traditional incandescent bulbs, light-emitting diodes (LEDs) are advantageous in low power consumption, long lifetime, small size, no warm-up time, fast reaction speed, and the ability to be manufactured as small or array devices. In addition to outdoor displays, traffic signs, and liquid crystal display (LCD) backlight for various electronic devices such as mobile phones, notebook computers or personal digital assistants (PDAs), LEDs are also widely used as indoor/outdoor lighting devices in place of fluorescent of incandescent lamps. 
     The size of traditional LED arrays is the dimension of millimeters (mm). The size of micro LED arrays may be reduced to the dimension of micrometers (μm) while inheriting the same good performances regarding power consumption, brightness, resolution, color saturation, reaction speed, life time and efficiency. In a micro LED manufacturing process, a thin-film, miniaturized and array design is adopted so that multiple micro LEDs are fabricated in the dimension of merely 1-10 μm. Next, these micro LEDs are mass transferred to be disposed on another circuit board. Protection layers and upper electrodes may be formed in a physical deposition process before packaging the upper substrate. Since the manufacturing process of micro LEDs is very complicated, there is a need to improve manufacturing yield. 
     SUMMARY OF THE INVENTION 
     The present invention provides a micro lighting device including a source line, a ground line, a main luminescent device having a first electrode and a second electrode, and a redundant luminescent device having a third electrode and a fourth electrode. The first electrode is electrically connected to the source line and the second electrode is electrically connected to the ground line and at least one of the third electrode and the fourth electrode is electrically isolated from both the source line and the ground line when the main luminescent device is able to light up. At least one of the first electrode and the second electrode is electrically isolated from both the source line and the ground line, the third electrode is electrically connected to the source line and the fourth electrode is electrically connected to the ground line when the main luminescent device is unable to light up. 
     The present invention further provides a micro lighting device including a source line, a ground line, a main luminescent device having a first electrode and a second electrode, a redundant luminescent device having a third electrode and a fourth electrode, and a conductive material. The first electrode is electrically connected to the source line and the second electrode is electrically connected to the ground line when the main luminescent device is able to light up. Both the first electrode and the second electrode are electrically isolated from both the source line and the ground line when the main luminescent device is unable to light up. The redundant luminescent device is arranged to be disposed on the main luminescent device when the main luminescent device is unable to light up and the conductive material is used for electrically connecting the third electrode to the source line and for electrically connecting the fourth electrode to the ground line. 
     The present invention further provides a method of manufacturing and repairing micro lighting device. The method includes fabricating a main luminescent device which includes a first electrode and a second electrode and then transferring the main luminescent device to be disposed on a substrate, fabricating a redundant luminescent device which includes a third electrode and a fourth electrode and then transferring the redundant luminescent device to be disposed on the substrate, electrically connecting the first electrode to a source line, electrically connecting the second electrode to a ground line, and electrically isolating at least one of the third electrode and the fourth electrode from both the source line and the ground line when the main luminescent device is able to light up, and electrically isolating at least one of the first electrode and the second electrode from both the source line and the ground line, electrically connecting the third electrode to the source line, and electrically connecting the fourth electrode to the ground line when the main luminescent device is unable to light up. 
     The present invention further provides a method of manufacturing and repairing micro lighting device. The method includes fabricating a main luminescent device which includes a first electrode and a second electrode, fabricating a redundant luminescent device which includes a third electrode and a fourth electrode, transferring the main luminescent device to be disposed on a substrate, electrically connecting the first electrode to a source line and electrically connecting the second electrode to a ground line when the main luminescent device is able to light up, electrically isolating at least one of the first electrode and the second electrode from both the source line and the ground line when the main luminescent device is able to light up, disposing the redundant luminescent device on the main luminescent device, and disposing a conductive material for electrically connecting the third electrode to the source line and for electrically connecting the fourth electrode to the ground line. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a structural diagram illustrating a micro lighting device according to an embodiment of the present invention. 
         FIG. 1B  is a diagram illustrating a method of repairing the micro lighting device according to an embodiment of the present invention. 
         FIG. 2A  is a structural diagram illustrating a micro lighting device according to another embodiment of the present invention. 
         FIG. 2B  is a diagram illustrating a method of repairing a micro lighting device according to another embodiment of the present invention. 
         FIG. 3A  is a structural diagram illustrating a micro lighting device according to another embodiment of the present invention. 
         FIGS. 3B-3D  are diagrams illustrating a method of repairing a micro lighting device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a structural diagram illustrating a micro lighting device  100  according to an embodiment of the present invention. A cross-sectional diagram of the micro lighting device  100  is depicted on the left side of  FIG. 1A , and a top-view diagram of the micro lighting device  100  is depicted on the right side of  FIG. 1A . The micro lighting device  100  with a thin-film, miniaturized and array design includes a plurality of main luminescent devices (only one main luminescent device  10  is depicted for illustrative purpose), at least one redundant luminescent device  20 , a source line  30 , and a ground line  40 . 
     The main luminescent device  10  and the redundant luminescent device  20  are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to a substrate  50 . Under normal condition, when a positive voltage is applied to a P-electrode and a negative voltage is applied to an N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, the main luminescent device  10  and the redundant luminescent device  20  may be micro LED devices. The main luminescent device  10  includes a P-type semiconductor layer  12 , an N-type semiconductor layer  14 , a P-electrode  16 , an n-electrode  18 , and a luminescent layer  15 , wherein the P-electrode  16  is electrically connected to the source line  30  and the N-electrode  18  is electrically connected to the ground line  40 . The redundant luminescent device  20  includes a P-type semiconductor layer  22 , an N-type semiconductor layer  24 , a P-electrode  26 , an n-electrode  28 , and a luminescent layer  25 , wherein the P-electrode  26  is electrically connected to the source line  30  but the N-electrode  18  is electrically isolated from the ground line  40 . 
       FIG. 1B  is a diagram illustrating a method of repairing the micro lighting device  100  according to an embodiment of the present invention. A cross-sectional diagram of the repaired micro lighting device  100  is depicted on the left side of  FIG. 1B , and a top-view diagram of the repaired micro lighting device  100  is depicted on the right side of  FIG. 1B , wherein the repair locations are designated by flash signs. For illustrative purpose, it is assumed that the main luminescent device  10  in  FIG. 1A  somehow malfunctions and is unable to light up when applying voltages to the P-electrode  16  and the N-electrode  18 , while the normal redundant luminescent device  20  is unable to light up because no voltage can be applied to the N-electrode  28 . As depicted in  FIG. 1B , the electrical connection between the P-electrode  16  of the main luminescent device  10  and the source line  30  may be cut off using laser cutting technique so as to prevent leakage current from the flawed main luminescent device  10 . Next, the electrical connection between the N-electrode  28  of the redundant luminescent device  20  and the ground line  40  may be established using laser repair technique so that the normal redundant luminescent device  20  may light up to replace the flawed main luminescent device  10 . 
       FIG. 2A  is a structural diagram illustrating a micro lighting device  200  according to another embodiment of the present invention. A cross-sectional diagram of the micro lighting device  200  is depicted on the left side of  FIG. 2A , and a top-view diagram of the micro lighting device  200  is depicted on the right side of  FIG. 2A . The micro lighting device  200  with a thin-film, miniaturized and array design includes a plurality of main luminescent devices (only one main luminescent device  10  is depicted for illustrative purpose), at least one redundant luminescent device  20 , a source line  30 , and a ground line  40 . 
     The main luminescent device  10  and the redundant luminescent device  20  are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to a substrate  50 . Under normal condition, when a positive voltage is applied to a P-electrode and a negative voltage is applied to an N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, the main luminescent device  10  and the redundant luminescent device  20  may be micro LED devices. The main luminescent device  10  includes a P-type semiconductor layer  12 , an N-type semiconductor layer  14 , a P-electrode  16 , an n-electrode  18 , and a luminescent layer  15 , wherein the P-electrode  16  is electrically connected to the source line  30  and the N-electrode  18  is electrically connected to the ground line  40 . The redundant luminescent device  20  includes a P-type semiconductor layer  22 , an N-type semiconductor layer  24 , a P-electrode  26 , an n-electrode  28 , and a luminescent layer  25 , wherein the N-electrode  18  is electrically connected to the ground line  40  but the P-electrode  26  is electrically isolated from the source line  30 . 
       FIG. 2B  is a diagram illustrating a method of repairing the micro lighting device  200  according to an embodiment of the present invention. A cross-sectional diagram of the repaired micro lighting device  200  is depicted on the left side of  FIG. 2B , and a top-view diagram of the repaired micro lighting device  200  is depicted on the right side of  FIG. 2B , wherein the repair locations are designated by flash signs. For illustrative purpose, it is assumed that the main luminescent device  10  in  FIG. 2A  somehow malfunctions and is unable to light up when applying voltages to the P-electrode  16  and the N-electrode  18 , while the normal redundant luminescent device  20  is unable to light up because no voltage can be applied to the P-electrode  26 . As depicted in  FIG. 2B , the electrical connection between the N-electrode  18  of the main luminescent device  10  and the ground line  40  may be cut off using laser cutting technique so as to prevent leakage current from the flawed main luminescent device  10 . Next, the electrical connection between the P-electrode  26  of the redundant luminescent device  20  and the source line  30  may be established using laser repair technique so that the normal redundant luminescent device  20  may light up to replace the flawed main luminescent device  10 . 
       FIG. 3A  is a structural diagram illustrating a micro lighting device  300  according to another embodiment of the present invention. A cross-sectional diagram of the micro lighting device  300  is depicted on the left side of  FIG. 3A , and a top-view diagram of the micro lighting device  300  is depicted on the right side of  FIG. 3A . The micro lighting device  300  with a thin-film, miniaturized and array design includes a plurality of main luminescent devices (only two main luminescent devices  11  and  12  are depicted for illustrative purpose), a source line  30 , and a ground line  40 . 
     The main luminescent devices  11  and  12  are fabricated by combining P-type and N-type semiconductor materials before being mass transferred to a substrate  50 . Under normal condition, when a positive voltage is applied to a P-electrode and a negative voltage is applied to an N-electrode, electrons flow from the N-region towards the P-region and holes flow from the P-region towards the N-region due to the forward-bias voltage. These electrons and holes then combine in the PN junction of the luminescent layer, thereby emitting photons of light. In an embodiment of the present invention, the main luminescent devices  11  and  12  may be micro LED devices each including a P-type semiconductor layer  12 , an N-type semiconductor layer  14 , a P-electrode  16 , an n-electrode  18 , and a luminescent layer  15 , wherein the P-electrode  16  is electrically connected to the source line  30  and the N-electrode  18  is electrically connected to the ground line  40 . 
       FIGS. 3B-3D  are diagrams illustrating a method of repairing the micro lighting device  300  according to an embodiment of the present invention. A cross-sectional diagram of the repaired micro lighting device  300  is depicted on the left side of  FIGS. 3B-3D , and a top-view diagram of the repaired micro lighting device  300  is depicted on the right side of  FIGS. 3B-3D , wherein the repair locations are designated by flash signs. For illustrative purpose, it is assumed that the main luminescent device  11  in  FIG. 3A  somehow malfunctions and is unable to light up when applying voltages to its P-electrode  16  and its N-electrode  18 , while the normal main luminescent device  12  is able to light up when applying voltages to its P-electrode  16  and its N-electrode  18 . As depicted in  FIG. 3B , the electrical connection between the P-electrode  16  of the main luminescent device  11  and the source line  30  and the electrical connection between the N-electrode  18  of the main luminescent device  11  and the ground line  40  may be cut off using laser cutting technique so as to prevent leakage current from the flawed main luminescent device  11 . Next as depicted in  FIG. 3C , a redundant luminescent device  20  may be fabricated by combining P-type and N-type semiconductor materials before being transferred to be displaced on the main luminescent device  11 . The redundant luminescent device  20  includes a P-type semiconductor layer  22 , an N-type semiconductor layer  24 , a P-electrode  26 , an n-electrode  28 , and a luminescent layer  25 . Next as depicted in  FIG. 3D , conductive material  35  may be deposited on the redundant luminescent device  20  so that the P-electrode  26  and the n-electrode  28  may be electrically connected to the source line  30  and the ground line  40 , respectively. Therefore, the normal redundant luminescent device  20  may light up to replace the flawed main luminescent device  11 . 
     In an embodiment of the present invention, the conductive material  35  may be tantalum, molybdenum or tungsten metal which may be welded to the electrodes of the redundant luminescent device  20  in a laser metal transfer (LMT) process. In another embodiment of the present invention, the conductive material  35  may be Ni(CO)4, Fe(CO)5, Cr(CO)6, Mo(CO)6, or W(CO)6 metal compounds which may be deposited on the electrodes of the redundant luminescent device  20  in a laser chemical vapor deposition (LCVD) process. However, the type of the conductive material  35  does not limit the scope of the present invention. 
     In conclusion, the present invention provides a micro lighting device with repair mechanism. In addition to good performances regarding power consumption, brightness, resolution, color saturation, reaction speed, life time and efficiency, the present micro lighting device can also improve manufacturing yield using the repair mechanism. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.