Abstract:
A method for manufacturing light emitting chips includes steps of: providing a substrate having a plurality of separate epitaxy islands thereon, wherein the epitaxy islands are spaced from each other by channels; filling the channels with an insulation material; sequentially forming a reflective layer, a transition layer and a base on the insulation material and the epitaxy islands; removing the substrate and the insulation material to expose the channels; and cutting the reflective layer, the transition layer and the base to form a plurality of individual chips along the channels.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a method for manufacturing light emitting chips, and more particularly, to a method for manufacturing light emitting chips having high light emitting efficiency. 
         [0003]    2. Description of Related Art 
         [0004]    As new type light source, LEDs are widely used in various applications. An LED often includes an LED chip to emit light. A conventional LED chip includes a substrate, and an N-type semiconductor layer, a light-emitting layer and a P-type semiconductor layer sequentially grown on the substrate. The substrate is generally made of sapphire (Al 2 O 3 ) for providing growing environment to the layers. However, such sapphire substrate has a low heat conductive capability, causing that heat generated by the layers cannot be timely dissipated. Therefore, a new type substrate made of Si is developed. Such Si substrate has a thermal conductivity larger than that of the sapphire substrate so that the heat generated by the layers can be effectively removed. 
         [0005]    Nevertheless, such Si substrate also has a problem that it absorbs the light emitted from the light-emitting layer due to the material characteristic thereof. Thus, the light extracting efficiency of the LED chip is limited. 
         [0006]    What is needed, therefore, is a method for manufacturing light emitting chips which can overcome the limitations described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present disclosure can be better understood with reference to the following 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 disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  shows a first process of a method for manufacturing light emitting chips in accordance with an embodiment of the present disclosure. 
           [0009]      FIG. 2  shows a second process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0010]      FIG. 3  shows a third process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0011]      FIG. 4  shows a fourth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0012]      FIG. 5  shows a fifth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0013]      FIG. 6  shows a sixth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0014]      FIG. 7  shows a seventh process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0015]      FIG. 8  shows an eighth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0016]      FIG. 9  shows a ninth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0017]      FIG. 10  shows a tenth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0018]      FIG. 11  shows an eleven process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0019]      FIG. 12  shows a twelve process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0020]      FIG. 13  shows a thirteenth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0021]      FIG. 14  shows a fourteenth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0022]      FIG. 15  shows a fifteenth process of the method of manufacturing light emitting chips in accordance with the embodiment of the present disclosure. 
           [0023]      FIG. 16  shows light emitting chips which have been manufactured by the method of  FIGS. 1-15 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0024]    A method for manufacturing light emitting chips in accordance with an embodiment of the present disclosure is disclosed. The method mainly includes multiple steps as described below. 
         [0025]    As shown in  FIG. 1 , a substrate  10  is provided. The substrate  10  is preferably made of Si. The substrate  10  has a flat top face for facilitating formation of semiconductor and other layers on the substrate  10 . 
         [0026]    The substrate  10  is provided with a photoresist layer  20  on the top face thereof as shown in  FIG. 2 . The photoresist layer  20  may be made of positive photoresist material or negative photoresist material, depending on the actual requirements. 
         [0027]    The photoresist layer  20  is patterned to form a plurality of individual islands as shown in  FIG. 3 . The islands of the photoresist layer  20  are spaced from each other by a plurality of gaps  22  between the islands. A plurality of areas of the top face of the substrate  10  are exposed to the gaps  22 . The method for patterning the photoresist layer  20  may be micro-lithography or other suitable technologies. 
         [0028]    As shown in  FIG. 4 , the substrate  10  is then heated in an environment containing a large amount of oxygen or nitrogen so that the exposed areas of the top face of the substrate  10  are reacted to form SiO 2  or Si 3 N 4 . Such SiO 2  or Si 3 N 4  acts as a blocking layer  12  which can prevent semiconductor structures from being grown therefrom. A temperature to heat the substrate  10  is preferably selected between 120 and 150 degrees centigrade. However, if high temperature-resistant material is employed to make the photoresist layer  20 , the temperature to heat the substrate  10  can raise to a range between 200 and 250 degrees centigrade. The photoresist layer  20  does not react with the oxygen or nitrogen and remains to cover the remaining areas of the top face of the substrate  10 . 
         [0029]    The photoresist layer  20  is removed to expose the remaining areas of the top face of the substrate  10  as shown in  FIG. 5 . The exposed remaining areas alternate with the reacted areas (i.e., the blocking layer  12 ) of the top face of the substrate  10 . The photoresist layer  20  may be removed by development or other suitable methods. 
         [0030]    As shown in  FIG. 6 , an epitaxy structure  30  is formed on the substrate  10 . The epitaxy structure  30  includes a first semiconductor layer  32 , a light-emitting layer  34  and a second semiconductor layer  36  grown on the exposed areas of the top face of the substrate  10  sequentially. In this embodiment, the first semiconductor layer  32  is an N-type GaN layer, the second semiconductor layer  36  is a P-type GaN layer, and the light-emitting layer  34  is a muti-quantum wells GaN layer. Alternatively, the first semiconductor layer  32 , the second semiconductor layer  36  and the light-emitting layer  34  can also be made of other suitable materials. Since the blocking layer  12  presented between the exposed areas of the top face of the substrate  10  prevents the epitaxy structure  30  from being grown therefrom, a plurality of channels  300  are defined just above the blocking layer  12  to divide the epitaxy structure  30  into a plurality of discrete blocks. However, in order to prevent the blocks of the epitaxy structure  30  from being grown laterally too much to connect with each other, a width of each channel  300  should be ensured twice more than a thickness of the epitaxy structure  30 . 
         [0031]    An insulation material  40  is further filled into the channels  300  to have a top face thereof coplanar with that of the epitaxy structure  30  as shown in  FIG. 7 . The insulation material  40  may be made of a material similar to that of the photoresist layer  20  or the blocking layer  12 . Preferably, a photoresist material is selected in this embodiment since the photoresist material has a good performance of filling. 
         [0032]    A reflective layer  50  is further formed on the top faces of the epitaxy structure  30  and the insulation material  40  as shown in  FIG. 8 . The reflective layer  50  is continuous to cover all the top faces of the epitaxy structure  30  and the insulation material  40 . The reflective layer  50  may be made of aluminum, silver or gold and formed via an E-gun or a PECVD (Plasma Enhanced Chemical Vapor Deposition) technology. The reflective layer  50  can reflect light emitted from the light-emitting layer  34  towards an outside environment, thereby increasing light-extracting efficiency of the light emitting chips. 
         [0033]    As shown in  FIG. 9 , a transition layer  60  is further formed on a top face of the reflective layer  50  via the E-gun or PECVD technology. The transition layer  60  may be made of silver, aluminum, gold or chrome. The transition layer  60  is used for joining another layer on the reflective layer  50 . 
         [0034]    A base  70  is further formed on the transition layer  60  by electroplating as shown in  FIG. 10 . The base  70  may be made of silver, aluminum, gold or cooper. The base  70  has a thickness far larger than that of the reflective layer  50  and that of the transition layer  60 . The base  70  functions to support the epitaxy structure  30  and absorb heat generated from the epitaxy structure  30 . The base  70  also acts as a conductor for introducing current into the epitaxy structure  30 . 
         [0035]    As shown in  FIG. 11 , a protective layer  80  is further provided to fully cover a top face of the base  70 , lateral faces of the base  70 , the transition layer  60 , the reflective layer  50  and the epitaxy structure  30 . The protective layer  80  also partially covers lateral sides of the substrate  10 . A bottom face of the substrate  10  is not covered by the protective layer  80  and is exposed to an external environment. The protective layer  80  may be made of corrosion-resistant materials such as wax. 
         [0036]    As shown in  FIG. 12 , the epitaxy structure  30  in combination with the other layers are inverted to render the bottom face of the substrate  10  facing upwardly, and the substrate  10  is wholly etched away to expose the bottom face of the first semiconductor layer  32  and the blocking layer  12 . The epitaxy structure  30 , the reflective layer  50 , the transition layer  60  and the base  70  are protected by the protective layer  80  from the etching. 
         [0037]    As shown in  FIG. 13 , the blocking layer  12  and the insulation material  40  are further removed from the epitaxy structure  30  by another etching or other methods, whereby the channels  300  in the epitaxy structure  30  are restored and exposed. 
         [0038]    The protective layer  80  is then fully removed to expose the transition layer  60 , the reflective layer  50  and the base  70  as shown in  FIG. 14 . 
         [0039]    As shown in  FIG. 15 , multiple pairs of first and second electrodes  38 ,  39  are formed on the blocks of the epitaxy structure  30  and the base  70 , respectively. Each first electrode  38  is made on a bottom face of the first semiconductor layer  32 , and a corresponding second electrode  39  is made on the top face of the base  70 . 
         [0040]    As shown in  FIG. 16 , finally, the reflective layer  50  together with the transition layer  60  and the base  70 , is cut to form a plurality of individual chips along the channels  300 . 
         [0041]    Since the original Si substrate  10  is removed and the reflective layer  50  is incorporated to the chip, the light extracting efficiency of the chip is enhanced. Furthermore, the metal base  70  can timely absorb much more heat from the epitaxy structure  30 , thereby ensuring normal operation of the chip. 
         [0042]    It is believed that the present disclosure and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the present disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments.