Abstract:
A method of manufacturing a light-emitting device includes: providing a substrate; forming a light-emitting structure comprising an active layer on the substrate; forming a protective layer having a first thickness on the light-emitting structure; etching the protective layer such that the protective layer has a second thickness less than the first thickness; and patterning the protective layer.

Description:
RELATED APPLICATION 
       [0001]    This application a continuation application of U.S. patent application Ser. No. 15/240,264, entitled “LIGHT EMITTING DEVICE”, filed on Aug. 18, 2016, which is a continuation application of U.S. patent application Ser. No. 14/098,643, entitled “LIGHT EMITTING DEVICE”, filed on Dec. 6, 2013, now U.S. Pat. No. 9,425,362, which claims priority from previously filed Taiwan Patent Application No. 101146337 filed on Dec. 7, 2012, entitled as “METHOD OF MAKING A LIGHT EMITTING DEVICE AND LIGHT EMITTING DEVICE MADE THEREOF”, and the entire contents of which are hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
     Technical Field 
       [0002]    The present disclosure relates to a method of making a light-emitting device and in particular to a method of etching a protective layer. 
       Description of the Related Art 
       [0003]    The light-emitting diodes (LEDs) of the solid-state lighting elements have the characteristics of the low power consumption, low heat generation, long operational life, shockproof, small volume, quick response and good opto-electrical property like light emission with a stable wavelength so the LEDs have been widely used in household appliances, indicator light of instruments, and opto-electrical products, etc. 
         [0004]    Generally speaking, the method of making a light-emitting diode comprises many lithography processes and each of the processes comprises complicated steps. How to reduce the steps of processes and decrease the cost is an important issue. 
         [0005]    Besides, light-emitting diodes can be further combined with a sub-mount to form a light emitting device, such as a bulb. The light-emitting device comprises a sub-mount with circuit; a solder on the sub-mount fixing the light-emitting diode on the sub-mount and electrically connecting the base of the light-emitting diode and the circuit of the sub-mount; and an electrical connection structure electrically connecting the electrode pad of the light-emitting diode and the circuit of the sub-mount; wherein the above sub-mount can be a lead frame or a large size mounting substrate for designing circuit of the light-emitting device and improving its heat dissipation. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    A method of manufacturing a light-emitting device includes: providing a substrate; forming a light-emitting structure comprising an active layer on the substrate; forming a protective layer having a first thickness on the light-emitting structure; etching the protective layer such that the protective layer has a second thickness less than the first thickness; and patterning the protective layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIGS. 1A-1H  show a cross-sectional view of a method of manufacturing a light-emitting device in accordance with an embodiment of the present disclosure. 
           [0008]      FIG. 2A  shows a light-emitting device in accordance with an embodiment according to the manufacturing method of the present disclosure. 
           [0009]      FIG. 2B  shows a partial enlarged drawing of  FIG. 2A . 
           [0010]      FIGS. 3A-3C  show top views of light-emitting devices in accordance with embodiments of the present disclosure. 
           [0011]      FIG. 4  shows an exploded drawing of a bulb in accordance with an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0012]    The drawings illustrate the embodiments of the application and, together with the description, serve to illustrate the principles of the application. The same name or the same reference number given or appeared in different paragraphs or figures along the specification should has the same or equivalent meanings while it is once defined anywhere of the disclosure. The thickness or the shape of an element in the specification can be expanded or narrowed. It is noted that the elements not drawn or described in the figure can be included in the present application by the skilled person in the art. 
         [0013]      FIGS. 1A-1G  show figures of a method of manufacturing a light-emitting device  100  in accordance with an embodiment of the present disclosure. 
         [0014]    As shown in  FIG. 1A , a substrate  10   a  is provided and a light-emitting structure  11  is formed on the substrate  10   a.  In this embodiment, the substrate  10   a  is a sapphire wafer substrate. The light-emitting structure  11  sequentially comprises a first type semiconductor layer  111 , an active layer  112 , and a second semiconductor layer  113  on the substrate. The first type semiconductor layer  111  and the second semiconductor layer  122  can be a cladding layer or a confinement layer separately provides an electron and a hole to be combined with each other in the active layer  112  and emits a light. As shown in  FIG. 1B , etching the active layer  112  and the second type semiconductor layer  113  to from a plurality of light-emitting structures  1000 . A plurality of the light-emitting structures  1000  are spaced arranged on the substrate  10   a  and expose a part of the first semiconductor layer  111 . Besides, the light-emitting device  100  is a horizontal type structure but can also be a vertical type structure or other type structure. As shown in  FIG. 1C , a protection layer  12  is formed to cover the first type semiconductor layer  111 , the active layer  112 , the second type semiconductor layer  113  and the substrate  10   a.  The protective layer  12  has a first thickness t 1  and is configured to protect the light-emitting structure  11  during the following etching process. In this embodiment, the first thickness t 1  is between 3300-10000 Å. As shown in  FIG. 1D , a laser is applied to cut the substrate  10  to form a trench  16  in the substrate  10 , wherein the cross section of the trench  16  is a triangle. It is noted that byproducts are generated when using a laser to cut the substrate  10 , and an etching step is applied to remove the byproducts. However, the protective layer  12  is also etched while etching the byproducts. Therefore, as shown in  FIG. 1E , the protective layer  120  has a second thickness t 2  between 3000-9700 Å after etching the byproducts and the second thickness t 2  is less than the first thickness t 1 . The difference between the first thickness t 1  and the second thickness t 2  is larger than 300 Å. In this embodiment, the method of etching the byproducts and etching the protective layer  12  at the same time comprises using an acidic solution to etch the byproducts and the protective layer  12 . The acidic solution comprises a mixture solution of a phosphoric acid solution and a sulfuric acid solution, wherein a ratio between the sulfuric acid and the phosphoric acid is about 3:1. In another embodiment, the acidic solution is a phosphoric acid solution. As shown in  FIG. 1F , the protective layer  120  is patterned to be a patterned protective layer  121 . In this embodiment, the patterned protective layer  121  is also configured to be a current barrier layer  121 . As shown in  FIG. 1G , a transparent conductive layer  13  is formed on the barrier layer  121  and the second semiconductor layer  113 . As shown in  FIG. 1H , a first electrode  14  is formed on the transparent conductive layer  13  at the position corresponding to the barrier layer  121  and a second electrode  15  is formed on the first type semiconductor layer  111 . The protective layer  121  or the barrier layer  121  is an insulating material and has a transmittance larger than 90%. Besides, the barrier layer  121  has a resistance larger than 10 14  Ω-cm. The barrier layer  121  comprises silicon oxide (SiO 2 ), silicon nitride (SiN x ) or titanium dioxide (TiO 2 ). Then, splitting the light-emitting structure  1000  along the trench  16  to form a plurality of light-emitting devices  100 . 
         [0015]      FIG. 2A  shows a light-emitting device  100  based on the method described in  FIGS. 1A-1H .  FIG. 2B  shows a partial enlarged drawing of  FIG. 2A . The light-emitting structure  11  is formed on the substrate  10   b.  The light-emitting structure  11  sequentially comprises a first type semiconductor layer  111 , an active layer  112 , and a second type semiconductor layer  113 . The second type semiconductor layer  113  comprises a first region  1131  and a second region  1132 . A barrier layer  121  is formed on the first region  1131  and has a lower surface  1211  and a side wall  1212  which is inclined against the lower surface  1211  and an angle (θ) between the sidewall and the bottom surface is between 10°-70°. A transparent conductive layer  13  is formed on the side wall  1212  of the barrier layer  121  and has a third thickness (t 3 ); the transparent conductive layer  13  is also formed on the second region  1132  of the second semiconductor layer  113  and has a fourth thickness (t 4 ). Since the angle (θ) between the sidewall  1212  and the lower surface  121  is less than 70°, the transparent conductive layer  13  can cover the side wall  1212  of the barrier layer  121  and the second region  1132  of the second semiconductor layer  113  uniformly. In this embodiment, a difference (t 3 −t 4 ) between the thickness of the transparent conductive layer  13  formed on the sidewall  1212  of the barrier layer  121  and the thickness of the transparent conductive layer  13  formed on the second region  1132  of the second semiconductor layer  113  and the thickness (t 3 ) of the transparent conductive layer  13  formed on the side wall  1212  of the barrier layer  121  forms a ratio ((t 3 −t 4 )/t 3 ) less than 10%. Besides, since a trench  16  of a triangular shape (referring to  FIG. 1D ) is formed in the substrate  10   a  when applying a laser, an inclined sidewall  101  of the substrate  10   b  is formed while splitting the light-emitting structures  1000  to form a light-emitting device  100 . The inclined sidewall  101  is inclined against an upper surface  102  of the substrate  10   b  and an angle between the inclined sidewall  101  and the upper surface  102  of the upper surface  102  is larger than 90°. Moreover, an acidic solution is used to remove the byproducts generated by laser cutting after the inclined sidewall  101  is cut by laser so that the inclined sidewall  101  has a rough surface. 
         [0016]      FIGS. 3A-3C  show top views of light-emitting devices  100 ,  100 ′ and  100 ″. The light-emitting device  100 ,  100 ′ or  100 ″ has a rectangular shape and has a first side  104 , a second side  105 , a third side  106 , and a fourth side  107 . As shown in  FIG. 3A , the light-emitting device  100  has a first electrode  14  near the first side  104  and the first electrode  14  is formed at the position on the transparent conductive layer  13  opposing to the barrier layer  121 . In this embodiment, the first electrode  14  has a shape substantially the same as that of the barrier layer  121 . The first electrode  14  comprises a first electrode pad  141  and a plurality of first extended electrodes  142  extending from the first electrode pad  141 . The area of the barrier layer  121  is larger than the area of the electrode pad  141  and the extended electrode  142 . The light-emitting device  100  further comprises a second electrode  15  near the second side  105  opposing to the first side  104 . The second electrode  15  comprises a second electrode pad  151  and a second extended electrode  152  extending to the first side  104  while a first extended electrode  142  extends from the first electrode pad  141  to the second electrode pad  151  (in a direction toward the second side  105 ). Besides, the first electrode pad  141  can also be placed at a corner near the first side  104  and the third side  106 , the second electrode pad  151  can also be placed at a corner near the second side  105  and the fourth side  107 , and the second extended electrode  152  extends toward the first electrode pad  141 . In another embodiment, as shown in  FIG. 3B , the light-emitting device  100 ′ comprises a first electrode  14 ′ and a second electrode  15 ′. The first electrode  14 ′ comprises a first electrode pad  141 ′ and a first extended electrode  142 ′. The second electrode  15 ′ comprises a second electrode pad  151 ′. The first extended electrode  142 ′ extends in a direction from the first electrode pad  141 ′ to the second electrode pad  151 ′. Besides, a barrier layer  121  comprises an electrode region  1215 , a plurality of first extension regions  1213 , and a plurality of second extension regions  1214 . The electrode region  1215  of the barrier layer  121  is formed on the region corresponding to the region of the first electrode  14 ′ and has a shape substantially the same as the first electrode  14 ′ and an area larger than that of the first electrode  14 ′. The first extension region  1213  extends from the electrode region  1215  (the first electrode pad  141 ′ and the first extend electrode  142 ′) to the side wall (the third side  106  and the fourth side  107 ). In this embodiment, four second extension regions  1214  extend forward (in a direction to the first side  104 ) and backward (in a direction to the second side  105 ) form the electrode region  1215  (the first electrode pad  141 ′ and the first extend electrode  142 ′). The first electrode  14 ′ is not formed on the first extension region  1213  and the second extension region  1214 . 
         [0017]    As shown in  FIG. 3C , in another embodiment, the light-emitting device  100 ″ comprises a first electrode  14 ″ and a second electrode  15 ″. The first electrode  14 ″ comprises a first electrode pad  141 ″ and a first extended electrode  142 ″. The second electrode  15 ″ comprises a second electrode pad  151 ″. The first extended electrode  142 ″ extends in a direction from the first electrode pad  141 ″ to the second electrode pad  151 ″. Besides, a barrier layer  121  comprises an electrode region  1215 ′ and a plurality of extension regions  1213 ′. The electrode region  1215 ′ of the barrier layer  121  is formed on the region corresponding to that of the first electrode  14 ″ and has a shape substantially the same as the first electrode  14 ″ and an area larger than that of the first electrode  14 ″. A plurality of extension regions  1213 ′ extends from the electrode region  1215 ′ (the first electrode pad  141 ″ and the first extend electrode  142 ″) to four sides ( 104 , 105 , 106 , and  107 ) at an angle of 45°. The first electrode  14 ″ is not formed on the extension region  1213 ′. 
         [0018]    The first type semiconductor layer can be an n-type semiconductor and the second type semiconductor layer can be a p-type semiconductor. The first type semiconductor layer and the second semiconductor layer comprise AlGaAs, AlGaInP, AlInP, InGaP, AlInGaN, InGaN, AlGaN and GaN. Optionally, the first type semiconductor layer can be a p-type semiconductor layer and the second type semiconductor layer can be an n-type semiconductor layer. The active layer comprises AlGaAs, AlGaInP, InGaP, AlInP, AlInGaN, InGaN, AlGaN and GaN. The active layer can be a single heterostructure (SH), a double-side double heterostructure (DDH) or a multi-quantum well (MQW) structure. The substrate comprises GaAs, GaP, Ge, sapphire, glass, diamond, SiC, Si, GaN, and ZnO or other substitution material. 
         [0019]      FIG. 4  shows an exploded drawing of a bulb  30  in accordance with an embodiment of the present disclosure. The bulb  30  comprises a cover  21 , a lens  22 , a light emitting module  24 , a substrate  25 , a heat-dissipation element  26 , a connection element  27 , and a circuit element  28 . The light emitting module  24  comprises a carrier  23  and a plurality of light-emitting devices. The light-emitting device can be any of the light-emitting device  100  ( 100 ′ and  100 ″) mentioned above. As shown in  FIG. 4 , for example, twelve light-emitting devices are placed on the carrier  23  comprising six red light light-emitting devices and six blue light light-emitting devices arranged staggered and electrically connected to each other (in series or in parallel). The blue light light-emitting device comprises a phosphor device formed above to convert the light emitted from the blue light light-emitting device. The light emitted by the blue light light-emitting device and the converted light are mixed to be a white light which is matched with a red light light-emitting device to emit a warm white light having a color temperature between 2400-3000K. 
         [0020]    It will be apparent to those having ordinary skill in the art that various modifications and variations can be made to the devices in accordance with the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure covers modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.