Abstract:
An exemplary method of manufacturing a light emitting diode (LED) die includes steps: providing a preformed LED structure, the LED structure including a first substrate, and a nucleation layer, a buffer layer, an N-type layer, a muti-quantum well layer and an P-type layer formed successively on the first substrate; forming at least one insulation block on the P-type layer; forming a mirror layer on the on the P-type layer and covering the insulation block; forming a conductive second substrate on the mirror layer; removing the first substrate, the nucleation layer and the buffer layer and exposing a bottom surface of the N-type layer; and disposing one N-electrode on the exposed surface of the N-type layer. The N-electrode is located corresponding to the insulation block.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure relates to a method for manufacturing a semiconductor structure, and more particularly to a method for manufacturing a light emitting diode (LED) die capable of to have current evenly flowing therein to improve the lighting efficiency of the LED die. 
         [0003]    2. Description of the Related Art 
         [0004]    LEDs have low power consumption, high efficiency, quick reaction time, long lifetime, and the absence of toxic elements such as mercury during manufacturing. Due to these advantages, traditional light sources are gradually replaced by LEDs. 
         [0005]    When the LED works, current flowing from a P electrode to an N electrode is easily concentrated on the shortest path between the P electrode and the N electrode. The concentration of the current results in a brightness of an illumination area of the LED near the N electrode being greater than other illumination area away from the N electrode, and accordingly, the brightness of the LED is not uniform. In addition, a temperature of the illumination area of the LED near the electrodes is easily becoming higher and higher which leads to a life time of the LED be decreased. 
         [0006]    Therefore, a manufacturing method of manufacturing the LED die that overcomes aforementioned deficiencies is required. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present method of manufacturing the LED die. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0008]      FIGS. 1 to 6  are cross-sectional views showing steps of a method for manufacturing an LED die in accordance with a first embodiment of the disclosure. 
           [0009]      FIGS. 7 to 13  are cross-sectional views showing steps of a method for manufacturing an LED die in accordance with a second embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring to  FIGS. 1 to 6 , a method of manufacturing an LED die  100  in accordance with first embodiment of the disclosure is provided. The manufacturing method includes steps as following. 
         [0011]    Referring  FIG. 1 , a preformed LED structure  10  is provided. The LED structure  10  includes a first substrate  11 , a nucleation layer  12 , a buffer layer  13 , an N-type layer  14 , a muti-quantum well layer  15  and a P-type layer  16  successively formed on the first substrate  11 , along a height direction of the LED structure  10 . 
         [0012]    Specifically, the first substrate  11  is flat and can be made of materials such as sapphire, silicon carbide (SiC), silicon (Si) or gallium nitride (GaN) and so on. In this embodiment, the first substrate  11  is made of sapphire. 
         [0013]    The nucleation layer  12 , the buffer layer  13 , the N-type layer  14 , the muti-quantum well layer  15  and the P-type layer  16  are sequentially formed on the first substrate  11  by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE). The nucleation layer  12  enhances a connection performance between the first substrate  11  and the buffer layer  13 . The buffer layer  13  decreases crystal lattices dislocation between the nucleation layer  12  and the N-type layer  14 . In this embodiment, the N-type layer  14  is N-type GaN, and the P-type layer  16  is P-type GaN. 
         [0014]    Referring to  FIG. 2 , an insulation layer  20  is formed on the P-type layer  16 . The insulation layer  20  can be made of materials such as SiO 2 , AlN, Si x N y  and so on. In this embodiment, the insulation layer  20  is made of SiO 2 . 
         [0015]    Referring to  FIG. 3 , the insulation layer  20  is etched to form a plurality of insulation blocks  21 . The insulation blocks  21  are formed by photolithography etching the insulation layer  20 . In this embodiment, the number of the insulation blocks  21  is two and the insulation blocks  21  are spaced from each other. 
         [0016]    Referring to  FIG. 4 , a mirror layer  30  is formed on the P-type layer  16  to cover the insulation blocks  21 . The mirror layer  30  is flat for improving light extracting efficiency of the LED die  100 . 
         [0017]    Referring to  FIG. 5 , a second substrate  40  is formed on the mirror layer  30  by electroplating or die bonding. The second substrate  40  is a metal substrate or a semiconductor substrate. The second substrate  40 , when designed as a metal substrate, may be made of Ti, Al, Ag, Ni, W, Cu, Pd, Cr or Au. Then the first substrate  11 , the nucleation layer  12  and the buffer layer  13  are removed from the LED structure  10  by laser separation method or chemical separation method, and a bottom surface of the N-type layer  14  originally adjacent to the buffer layer  13  is exposed. 
         [0018]    Referring to  FIG. 6 , the LED structure  10  is inverted, and two N-electrodes  50  are disposed on the exposed surface of the N-type layer  14  and located corresponding to the insulation blocks  21 , respectively. The N-electrodes  50  may be made of materials such as Ti, Al, Ag, Ni, W, Cu, Pd, Cr or Au. Each N-electrode  50  has a size the same as that of each insulation block  21 . 
         [0019]    When the LED die  100  works, the second substrate  40  and the N-electrodes  50  are located at two opposite sides of the muti-quantum well layer  15  respectively. When a forward voltage is applied to the second substrate  40  and the N-electrodes  50 , electrons inside the N-type layer  14  will be captured by electric holes inside the P-type layer  16  under excitation of an electric field, photons are emitted from the muti-quantum well layer  15  where the combinations of the electrons and the electric holes occur. Since the N-electrodes  50  are located corresponding to the insulation blocks  21 , the shortest path for current between the second substrate  40  and the N-electrodes  50  are blocked by the insulation blocks  21 , thereby making the current be dispersed in the LED die  100  more evenly. The current flowing from the second substrate  40  to the N-type electrodes  50 , will go around two opposite sides of each of the insulation blocks  21  by dodging the insulation blocks  21 . Accordingly, the current is more uniformly distributed in the LED die  100  to cause the LED die  100  to have a more uniform illumination and an enhanced lighting efficiency. Meanwhile, the life time of the LED die  100  is prolonged since heats generated by the LED die  100  are evenly distributed in the LED die  100 . 
         [0020]    Referring to  FIGS. 7 to 13 , a method of manufacturing an LED die  200  in accordance with second embodiment of the disclosure is provided. 
         [0021]    Referring to  FIG. 7 , a preformed LED structure  10  is provided. The LED structure  10  includes a first substrate  11 , a nucleation layer  12 , a buffer layer  13 , an N-type layer  14 , a muti-quantum well layer  15  and a P-type layer  16  successively formed along a height direction of the LED structure  10 . 
         [0022]    The first substrate  11  is flat and may be made of some materials such as sapphire, silicon carbide (SiC), silicon (Si) or gallium nitride (GaN) and so on. In this embodiment, the first substrate  11  is made of sapphire. 
         [0023]    The top surface of the P-type layer  16  is etched to form a plurality of grooves  17  spaced from each other. Each groove  17  has a depth which is smaller than a height of the P-type layer  16 . In this embodiment, the number of the grooves  17  is two and the two grooves  17  are spaced from each other. 
         [0024]    Referring to  FIG. 8 , an insulation layer  20  is formed on the P-type layer  16  with a part of the insulation layer being received in the grooves  17 . The insulation layer  20  may be made of materials such as SiO 2 , AlN or Si x N y . In this embodiment, the insulation layer  20  is made of SiO 2 . 
         [0025]    Referring to  FIG. 9 , a part of the insulation layer  20  on the P-type layer  16  without being received in the grooves  17  is removed, and a part of the insulation layer  20  received in the grooves  17  is retained to form a plurality of insulation blocks  21 . A top surface of each of the insulation blocks  21  is coplanar with a top surface of the P-type layer  16 . In this embodiment, the part of the insulation layer  20  on the P-type layer  16  without being etched to define the grooves  17  is removed by chemical-mechanical polishing method. 
         [0026]    Referring to  FIG. 10 , a mirror layer  30  is formed on the P-type layer  16  and covers the insulation blocks  21 . The mirror layer  30  is flat for strengthening outputs of light of the LED die  200 . 
         [0027]    Referring to  FIG. 11 , a second substrate  40  is formed on the mirror layer  30  by electroplating or die bonding. The second substrate  40  is a conductive substrate. The second substrate  40  is a metal substrate made of metal materials such as Ti, Al, Ag, Ni, W, Cu, Pd, Cr or Au. 
         [0028]    The first substrate  11 , the nucleation layer  12  and the buffer layer  13  are removed from the LED structure  10  by laser separation method or chemical separation method, and a bottom surface of the N-type layer  14  originally adjacent to the buffer layer  13  is exposed in the air. 
         [0029]    Referring to  FIG. 12 , the LED structure  10  is inverted, two N-electrodes  50  are disposed on the exposed surface of the N-type layer  14  corresponding to the locations of the insulation blocks  21 . The N-electrodes  50  may be made of materials such as Ti, Al, Ag, Ni, W, Cu, Pd, Cr or Au. Each N-electrode  50  has a size the same as that of each insulation block  21 . 
         [0030]    When the LED die  200  works, the second substrate  40  and the N-electrodes  50  are respectively located at two opposite sides of the muti-quantum well layer  15 . When a forward voltage is applied to the second substrate  40  and the N-electrodes  50 , electrons inside the N-type layer  14  jump to electric holes inside the P-type layer  16  by excitation of an electric field; photons are emitted from the muti-quantum well layer  15  where the combinations of the electrons and the electric holes occur. Since the N-electrodes  50  correspond to the insulation block  21  in size and position, the current which may flow through the shortest path between the second substrate  40  and the N-electrodes  50  are blocked by the insulation blocks  21 . The current evenly flows from the second substrate  40  to the N-type electrodes  50  via two opposite sides of each of the insulation blocks  21  by dodging the insulation blocks  21 . Meanwhile, the life time of the LED die  200  is prolonged since heats generated by the LED die  100  are more evenly distributed in the LED die  200 . 
         [0031]    It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.