Abstract:
The invention provides a substrate structure used for manufacturing a light-emitting diode and a method for manufacturing the light-emitting diode. The substrate structure includes a substrate having a first surface and a second surface opposite to the first surface and a plurality of grooving structure formed on the first surface of the substrate. The light-emitting diode is formed on the first surface of the substrate.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to Taiwan Application Serial Number 102105730 filed Feb. 19, 2013, which is herein incorporated by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to a light-emitting diode, and more particularly, to a light-emitting diode having a plurality of recess structures on the side walls. 
         [0004]    2. Description of Related Art 
         [0005]    Generally, when a light-emitting diode (LED) operates and emits light, the light travels into a transparent substrate from a light-emitting layer, and then transmits out from sidewalls of the transparent substrate. Therefore, the transmittance of the transparent substrate directly affects the light-emitting efficiency of light-emitting diode. Conventionally, a sidewall etching (SWE) process or a stealth dicing (SD) process is used to isolate LED dies, but it is known that the processes are harmful to the transmittance of a light-emitting diode. 
         [0006]    For example, when the SWE process is used to isolate the LED dies, several sintering marks may be formed on the transparent substrate. The sintering marks can absorb light energy and reduce the transmittance. On the other hand, when the SD process is used to isolate the LED dies, the sidewall of the LED dies are so smooth that the light entering into the transparent substrate may face total internal reflection, which reduces the transmittance. 
         [0007]    Therefore, an improved LED die and a method of manufacturing the same are needed to solve the aforementioned problems. 
       SUMMARY 
       [0008]    The present disclosure provides a light-emitting diode (LED) die and a method for manufacturing thereof, so as to solve the problems of the prior art and enhance the transparent efficiency of the LED die. 
         [0009]    One aspect of the present disclosure is to provide an LED die. The LED die comprises a transparent substrate, an N-type semiconductor layer positioned on the transparent substrate, a light-emitting layer positioned on the N-type semiconductor layer, and a P-type semiconductor layer positioned on the light-emitting layer. In which, the N-type semiconductor layer, the transparent substrate or both have side walls with a plurality of recess structure. 
         [0010]    Another aspect of the present disclosure is to provide a method for manufacturing the LED die. The method for manufacturing the LED die comprises the following steps. A transparent substrate is provided, which has an upper surface. A LED stacked structure is formed on the transparent substrate. A plurality of recess structures are formed on sidewalls of the N-type semiconductor layer, the transparent substrate or both. In which, the LED stacked structure comprises an N-type semiconductor layer positioned on the transparent substrate, a light-emitting layer positioned on the N-type semiconductor layer, and a P-type semiconductor layer positioned on the light-emitting layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1A  is a top view of a light-emitting diode (LED) die according to one embodiment of the present disclosure; 
           [0013]      FIG. 1B and 1C  are cross-sectional views of the LED die taken along A-A′ line in  FIG. 1A ; 
           [0014]      FIG. 1D to 1F  are cross-sectional views of the LED die taken along B-B′ line in  FIG. 1A ; 
           [0015]      FIG. 2A  is a top view of an LED die according to one embodiment of the present disclosure; 
           [0016]      FIG. 2B  is a cross-sectional view of the LED die taken along C-C′ line in  FIG. 2A ; 
           [0017]      FIG. 2C and 2D  are cross-sectional views of the LED die taken along D-D′ line in  FIG. 2A ; and 
           [0018]      FIG. 3A to 3F  are side views of LED die structures according to embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The light-emitting diode (LED) die and the method for manufacturing the same of the embodiments are discussed in detail below, but not limited the scope of the present disclosure. The same symbols or numbers are used to the same or similar portion in the drawings or the description. And the applications of the present disclosure are not limited by the following embodiments and examples, which the person in the art can apply in the related field. 
         [0020]    The present disclosure provides an LED die, and a method for manufacturing thereof. In which, the LED die comprises a plurality of recess structures enhancing the laterally light-emitting efficiency of the LED die. 
         [0021]      FIG. 1A  is a top view of a light-emitting diode (LED) die according to one embodiment of the present disclosure. In  FIG. 1A , the LED die  100  comprises a plurality of recess structures  110  surrounding the edge of the LED die  100 . 
         [0022]      FIG. 1B and 1C  are cross-sectional views of the LED die taken along A-A′ line in  FIG. 1A . In  FIG. 1B , the structure of the LED die  100  from bottom to top is a transparent substrate  120 , an N-type semiconductor layer  130 , a light-emitting layer  140 , a P-type semiconductor layer  150  and an electrode  160 . In which, the recess structures  110  are positioned on the sidewalls of the transparent substrate  120 . According to one embodiment of the present disclosure, the recess structures  110  are positioned on the sidewalls of the transparent substrate  120  and the N-type semiconductor layer  130 , as shown in  FIG. 1C . According to another embodiment of the present disclosure, the recess structures  110  are positioned on the sidewalls of the N-type semiconductor layer  130 . According to one embodiment of the present disclosure, the material of the transparent substrate  120  is selected from the group of sapphire, silicon, silicon carbide (SiC), diamond, quartz, and the combinations thereof. 
         [0023]    Otherwise, in  FIG. 1B , the sidewalls of the transparent substrate  120  and the N-type semiconductor layer  130  further comprises a chamfer structure (φ). According to one embodiment of the present disclosure, the chamfer structure (φ) has angle in a range of 30° to 90°. 
         [0024]    A cross-section of the recess structures  110  has a first normal line  112 , and the transparent structure  120  has a second normal line  122 , wherein the first normal line  112  and the second normal line  122  has an included angle (θ). According to one embodiment of the present disclosure the included angle (θ) is in a range of 30° to 60°. According to another embodiment of the present disclosure, the included angle (θ) is 45°. 
         [0025]    The light  170  may enter into the transparent substrate  120  from the light-emitting layer  140 , and then emit from the sidewalls of the transparent substrate  120 . Because the recess structures  110  may be a rough surface on the edge of the transparent substrate  120  or the N-type semiconductor layer  130 , and increase the surface area, the light-emitting efficiency of the LED die  100  is increased thereby. 
         [0026]    The recess structures of the LED die are orifice-shaped, groove-shaped or both. In which, the orifice-shaped recess structures are in shape of inverted trapezoid, pullet, saw tooth, inverted pyramid, or a combination thereof. 
         [0027]      FIGS. 1D to 1F  are cross-sectional views of the LED die taken along B-B′ line in  FIG. 1A . In  FIG. 1D , the recess structures  110  of the LED die  100  is in inverted trapezoid shape. According to one embodiment of the present disclosure, the recess structures  110  of the LED die  100  is in pullet shape, as shown in  FIG. 1E . According to another embodiment of the present disclosure, the recess structures  110  of the LED die  100  is in inverted pyramid shape, as shown in  FIG. 1F . According to one embodiment of the present disclosure, the depth of the recess structures  110  is in a range of 6 μm to 12 μm. 
         [0028]      FIG. 2A  is a top view of an LED die according to one embodiment of the present disclosure, wherein the recess structures is in grooves. In  FIG. 2A , a LED die  200  comprises a plurality of recess structures  210  in grooves surrounding the edge of the LED die  200 . 
         [0029]      FIG. 2B  is a cross-sectional view of the LED die taken along C-C′ line in  FIG. 2A . In  FIG. 2B , the structure of the LED die  200  from bottom to top is a transparent substrate  220 , an N-type semiconductor layer  230 , a light-emitting layer  240 , a P-type semiconductor layer  250  and an electrode  260 . In which, the recess structures  210  are positioned on the sidewalls of the transparent substrate  220 . 
         [0030]      FIGS. 2C and 2D  are cross-sectional views of the LED die taken along D-D′ line in  FIG. 2A . In  FIG. 2C , the recess structures  210  are positioned on the sidewalls of the transparent substrate  220  and the N-type semiconductor layer  230 . In  FIG. 2D , the recess substrates  210  are positioned on the sidewalls of the N-type semiconductor layer  230 . 
         [0031]      FIGS. 3A to 3F  are side views of LED die structures according to embodiments of the present disclosure. In  FIG. 3A , the transparent substrate  310  is provided, which has an upper surface  312 . Then, a light-emitting diode (LED) structure  320  is formed on the upper surface of the transparent substrate  310 , as shown in  FIG. 3B . The LED stacked structure  320  from bottom to top comprises an N-type semiconductor layer, a light-emitting layer and a P-type semiconductor layer, wherein the N-type semiconductor layer, the light-emitting layer and the P-type semiconductor layer are not shown individually. 
         [0032]    In  FIG. 3C , a mask  330  has a plurality of holes  332 . The mask  330  covers on the LED stacked structure  320 , and then form a plurality of recess structures  312  on the transparent substrate  310 , the LED stacked structure  320  or the both, by an etching method  340 . In which, the etching method  340  may be a dry-etching or a wet-etching or the both. 
         [0033]    According to one embodiment of the present disclosure, the dry-etching is performed by inductively coupled plasma (ICP). Compared to wet-etching, dry-etching possess higher accuracy, but may damage the LED stacked structure. 
         [0034]    According to one embodiment of the present disclosure, the wet-etching is performed by hot phosphoric acid. Because hot phosphoric acid may etch the N-type semiconductor layer at the same time, the light-emitting efficiency can be enhanced. But, compared to dry-etching, the etching time of wet-etching is longer, and may damage the LED stacked structure. 
         [0035]    According to one embodiment of the present disclosure, the recess structures are formed by laser, and then sintering marks are removed by hot phosphoric acid. Because the depth of the recess structures can be controlled precisely by laser, and the etching time can be reduced, the LED die made by this embodiment has better light-emitting efficiency. 
         [0036]    In  FIG. 3D , the LED stacked structure  320  and the transparent substrate  310  are diced along the recess structures  312 , so as to form the LED die  300 . In which, the recess structures  312  are formed on the sidewalls of the LED stacked structure  320  and the transparent substrate  310 . 
         [0037]    According to one embodiment of the present disclosure, the recess structures  312  are only formed on the sidewalls of the LED stacked structure  320 , as shown in  FIG. 3E . According to another embodiment of the present disclosure, the LED stacked structure  320  does not completely cover the transparent substrate  310 , so the recess structures  312  can be only formed on the sidewalls of the transparent substrate  310 , as shown in  FIG. 3F . 
         [0000]    
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Promoting 
                   
                   
                   
               
               
                   
                   
                 Rate of 
               
               
                   
                   
                 Light 
                   
                 Difference 
               
               
                   
                 Light 
                 intensity 
                 Electric 
                 of Electric 
                 Yield 
               
               
                   
                 Intensity 
                 (%) 
                 Performance 
                 Performance 
                 (%) 
               
               
                   
               
             
             
               
                 Example 1 
                 193.04 
                 2.3% 
                 3.09 
                 −0.02 
                 95.80 
               
               
                 Comparative 
                 188.62 
                 — 
                 3.11 
                 — 
                 94.17 
               
               
                 Example 1 
               
               
                 Example 2 
                 197.05 
                 3.6% 
                 3.10 
                  0.00 
                 95.21 
               
               
                 Comparative 
                 190.13 
                 — 
                 3.10 
                 — 
                 95.09 
               
               
                 Example 2 
               
               
                 Example 3 
                 195.85 
                 2.0% 
                 3.09 
                 −0.01 
                 93.42 
               
               
                 Comparative 
                 192.08 
                 — 
                 3.10 
                 — 
                 91.86 
               
               
                 Example 3 
               
               
                 Example 4 
                 197.59 
                 1.2% 
                 3.10 
                 −0.02 
                 93.95 
               
               
                 Comparative 
                 195.34 
                 — 
                 3.12 
                 — 
                 93.82 
               
               
                 Example 4 
               
               
                   
               
             
          
         
       
     
         [0038]    Table 1 is comparisons of a wet-etching method with laser and a sidewall etching method for the influence of the light intensity, electric performance and yield of LED dies. The experiment is performed on the same wafer, wherein a half of the wafer is used to make LED dies by the sidewall etching; and another half of the wafer is used to make LED dies by the wet-etching method with laser. 
         [0039]    On Table 1, Examples 1-4 are all firstly forming recess structures by laser, and then removing residual sintering marks by hot phosphoric acid. And Comparative Examples 1-4 are only performed sidewall etching by laser. Compared to Comparative Examples, the light intensities of LED of Examples are enhanced 1.2% to 3.6%. Otherwise, there is no significant difference of electric performance and yield of LEDs between Examples and Comparative Examples. It is known as the results of Table 1 that the light intensities of LEDs provided by embodiments of the present disclosure are enhanced without the influence of the electric performance and yield of the same. 
         [0040]    In embodiments of the present disclosure, since the recess structures are formed on the transparent substrate, the N-type semiconductor layer or the both, it can not only increase the surface area of the side wall of LEDs, but also enhance the light-emitting efficiency. Therefore, the method for manufacturing LEDs provided by embodiments of the present disclosure can solve the problems of the conventional manufacturing process. 
         [0041]    Although embodiments of the present disclosure and their advantages have been described in detail, they are not used to limit the present disclosure. It should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the present disclosure. Therefore, the protecting scope of the present disclosure should be defined as the following claims.