Abstract:
A light-emitting diode includes a substrate, the substrate including an upper surface, a bottom surface opposite to the upper surface, and a side surface; a first type semiconductor layer on the upper surface, wherein the first type semiconductor layer includes a first portion and a second portion, and the second portion includes an edge surrounding the first portion; a light-emitting layer on the first portion; and a second type semiconductor layer on the light-emitting layer, wherein the second portion includes a first surface and a second surface, and a first distance is between the first surface and the upper surface, and a second distance is between the second surface and the upper surface and is smaller than the first distance; wherein the first surface is rougher than the second surface, and the second surface is located at the edge.

Description:
TECHNICAL FIELD 
     The present application relates to a method of dicing a wafer to improve the production of light-emitting diodes and decreasing the cost thereof. 
     DESCRIPTION OF BACKGROUND ART 
     As the light emitting efficiency of the light-emitting diode (LED) is increased in recent years, the application of the light-emitting diode has expanded from decoration lighting to the general lighting. The light-emitting diode also has gradually replaced the traditional fluorescent lamp to be the light source of the next generation. 
     The final step of producing the light-emitting diodes is dicing the wafer. In the step of dicing, firstly the wafer is cut by laser, and then the wafer is cleaved into a plurality of light-emitting diodes. Traditionally, the laser ablates or melts the wafer from the wafer&#39;s surface to the wafer&#39;s interior. The wafer has semiconductor stacking layers on the surface. Thus, when the wafer is ablated or melted by the laser, the light-absorbing substance which is able to absorb the light is generated. 
     The above light-emitting diode can further comprise a sub-mount to form a light-emitting device, wherein the light-emitting device comprises electric circuitries disposed on the sub-mount, at least a solder on the sub-mount to fix the light-emitting diode on the sub-mount, and an electrical connection structure to electrically connect an electrical pad of the light-emitting diode (LED) and the electric circuitries of the sub-mount. The sub-mount can be a lead frame or a mounting substrate for electrical circuit design and heat dissipation improvement. 
     SUMMARY OF THE DISCLOSURE 
     A light-emitting diode, comprising: a substrate, the substrate comprising an upper surface, a bottom surface opposite to the upper surface, and a side surface; a first type semiconductor layer on the upper surface, wherein the first type semiconductor layer comprises a first portion and a second portion, and the second portion comprises an edge surrounding the first portion; a light-emitting layer on the first portion; and a second type semiconductor layer on the light-emitting layer, wherein the second portion comprises a first surface and a second surface, and a first distance is between the first surface and the upper surface, and a second distance is between the second surface and the upper surface and is smaller than the first distance; wherein the first surface is rougher than the second surface, and the second surface is located at the edge. 
     A method of manufacturing a light-emitting diode, comprising the steps of: provide a substrate; providing a semiconductor stack layer on the substrate, wherein the semiconductor stack layer comprises a first surface opposite to the substrate; treating the first surface to form a second surface, wherein the second surface is flatter than the first surface; and providing a laser beam through the second surface to separate the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  schematically show a light-emitting diode in accordance with an embodiment of the present application; 
         FIGS. 2A and 2B  schematically show a wafer device in accordance with an embodiment of the present application; 
         FIGS. 3A to 3G  schematically show a method of manufacturing the light-emitting diode in accordance with an embodiment of the present application. 
         FIG. 4  shows a light bulb having the LED array from any one of the first to third embodiments. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings hereafter. The following embodiments are given by way of illustration to help those skilled in the art fully understand the spirit of the present application. Hence, it should be noted that the present application is not limited to the embodiments herein and can be realized by various forms. Further, the drawings are not precise scale and components may be exaggerated in view of width, height, length, etc. Herein, the similar or identical reference numerals will denote the similar or identical components throughout the drawings. 
     First Embodiment 
       FIGS. 1A and 1B  schematically show a light-emitting diode in accordance with an embodiment of the present application.  FIG. 1A  shows a top view of a light-emitting diode comprising a first type semiconductor layer  20 , a second type semiconductor layer  40  on the first type semiconductor layer  20 , a first electrical pad  23  ohmically contacts the first type semiconductor layer  20  and a second electrical pad  43  ohmically contacts the second type semiconductor layer  40 . The first type semiconductor layer  20  comprises a first surface  21  and a second surface  222 , wherein the second surface  222  surrounds the first portion. 
       FIG. 1B  shows the cross-sectional view of the dotted line AA′ in  FIG. 1A . The light-emitting diode comprises a transparent substrate  10  having an upper surface  101 , a bottom surface  102 , and a side surface  103  between the upper surface  101  and the bottom surface  102 , a first type semiconductor layer  20  on the upper surface  101 , a light-emitting layer  30  on the first type semiconductor layer  20 , a second type semiconductor layer  40  on the light-emitting layer  30 , a first electrical pad  23  ohmically contacts the first type semiconductor layer  20 , a second electrical pad  43  ohmically contacts the second type semiconductor layer  40 , and a reflective layer  50  on the bottom surface  102 , wherein the side surface  103  comprises a damage region  1031 . 
     The material of the transparent substrate  10  comprises the transparent material, such as sapphire (Al 2 O 3 ), GaN, SiC, AlN, ZnO or MgO, SiO 2 , B 2 O 3  or BaO, so the transparent substrate  10  can be penetrated by a laser beam which is able to focus on the interior thereof. The damage region  1031  is formed on the side surface  103  during the laser penetration and is distant from the upper surface  101  and the bottom surface  102 . The wavelength region of the laser beam comprises 350-500, 350-800, 350-1200, 500-1000, 700-1200 or 350-1500 nm. The first type semiconductor layer  20  comprises a first portion  201  and a second portion  202 , the light-emitting layer  30  is on the first portion  201 , and the second type semiconductor layer  40  is on the light-emitting layer  30 . When the first type semiconductor layer  20  is p-type semiconductor material, the second type semiconductor layer  40  can be n-second type semiconductor. Conversely, when the first type semiconductor layer  20  is n-type semiconductor material, the second type semiconductor layer  40  can be semiconductor material. The light-emitting layer  30  can be intrinsic semiconductor material, p-type semiconductor material or n-type semiconductor material. When an electrical current flows through the first type semiconductor layer  20 , the light-emitting layer  30 , and the second type semiconductor layer  40 , the light-emitting layer  30  can emit a light. When the light-emitting layer  30  is Al a Ga b In 1-a-b P, the light-emitting layer  30  can emit a red, orange, or yellow light. When the light-emitting layer  30  is Al c Ga d In 1-c-d N, the light-emitting layer  30  can emit a blue or green light. 
     The second portion  202  of the first type semiconductor layer  20  comprises a first surface  21 , a second surface  222  and a third surface  221 . The second type semiconductor layer  40  comprises a fifth surface  41  and a fourth surface  42 . The average roughness (Ra) of the first surface  21  and that of the fifth surface  41  are larger than 100 nm. The average roughness (Ra) of each of the second surface  222 , third surface  221  and the fourth surface  42  is in a range of 10 nm to 100 nm, and preferably is smaller than 50 nm. The second surface  222  and the third surface  221  are flatter than the first surface  21 , and the fourth surface  42  is flatter than the fifth surface  41 . The average roughness (Ra) of the first surface  21  and that of the fifth surface  41  larger than 100 nm can reduce the total internal reflection of the light emitted from the light-emitting layer  30  to increase the light extraction efficiency. The second surface  222 , the third surface  221  and the fourth surface  42  are formed by regionally treating the first surface  21  and the fifth surface  41  at the same time with the same process, such as wet etching or dry etching, so the difference of the average roughness (Ra) between the fourth surface  42 , or the third surface  221 , and the second surface  222  is smaller than 50 nm. Thus, the depth of the second surface  222  or the third surface  221  related to the first surface  21  is the same as that of the fourth surface  42  related to the fifth surface  41 . The depth of the second surface  222  or the third surface  221  related to the first surface  21  is in a range of 2000 Å and 10000 Å, and preferably in a range of 4000 Å and 7000 Å. The depth of the fourth surface  42  related to the fifth surface  41  is in a range of 2000 Å and 10000 Å, and preferably in a range of 4000 Å and 7000 Å. 
     The first electrical pad  23  is formed on the third surface  221  and ohmically contacts the first type semiconductor layer  20 . The second electrical pad  43  is formed on the fourth surface  42  and ohmically contacts the second type semiconductor layer  40 . The first electrical pad  23  and the second electrical pad  43  are operable for conducting an electrical current from outside to flow through the first type semiconductor layer  20 , the light-emitting layer  30 , and the second type semiconductor layer  40 . The material of the first electrical pad  23  and the second electrical pad  43  comprises the metal material, such as Cu, Al, In, Sn, Au, Pt, Zn, Ag, Ti, Ni, Pb, Pd, Ge, Cr, Cd, Co, Mn, Sb, Bi, Ga, Tl, Po, Ir, Re, Rh, Os, W, Li, Na, K, Be, Mg, Ca, Sr, Ba, Zr, Mo or La, or metal alloy, such as Ag—Ti, Cu—Sn, Cu—Zn, Cu—Cd, Sn—Pb—Sb, Sn—Pb—Zn, Ni—Sn, Ni—Co, Au alloy, or Ge—Au—Ni. 
     The second surface  222  surrounds the first portion and is therefore located at the edge of the light-emitting diode. The width of the second surface  222  is in a range of 5 μm and 15 μm, and preferably is 10 μm. Because the average roughness (Ra) of the second surface  222  is in a range of 10 nm to 100 nm, and preferably is smaller than 50 nm, the laser beam can penetrate the second surface  222  to focus in the interior of the substrate  10 . 
     The reflective layer  50  on the bottom surface  102  can reflect the light emitted from the light-emitting layer  30  to increase the light extraction efficiency. The reflective layer  50  comprises a metal layer, DBR, or the combination thereof. The reflectivity of the reflective layer  50  is larger than 70% for the laser beam, of which the wavelength region is in a range of 350 nm and 500 nm, 350 nm and 800 nm, 350 nm and 1200 nm, 500 nm and 1000 nm, 700 nm and 1200 nm, or 350 nm and 1500 nm. 
     Second Embodiment 
       FIGS. 2A and 2B  schematically show a wafer device  2  in accordance with an embodiment of the present application.  FIG. 2A  shows that a wafer device  2  has a transparent substrate  10  and a plurality of units  1  on the substrate  10 . Any two of the units  1  are spaced by a second surface  222 . A plurality of light-emitting diodes can be produced by cleaving the wafer device  2  along the second surface  222 . 
       FIG. 2B  shows the cross-sectional view of the dotted line BB′ in  FIG. 2A . The transparent substrate  10  has an upper surface  101  and a bottom surface  102 . The material of the transparent substrate  10  comprises the transparent material, such as sapphire (Al 2 O 3 ), GaN, SiC, AlN, ZnO or MgO, SiO 2 , B 2 O 3  or BaO, so the transparent substrate  10  can be penetrated by a laser beam which is able to focus on interior thereof. The damage region  1031  is formed in the interior of the substrate  10  and is distant from both of the upper surface  101  and the bottom surface  102 . The wavelength range of the laser beam comprises 350-500, 350-800, 350-1200, 500-1000, 700-1200 or 350-1500 nm. 
     A first type semiconductor layer  20  is formed on the upper surface  101 , which has a plurality of first portions  201  and a plurality of second portions  202 . On each of the plurality of first portions  201 , a light-emitting layer  30  is formed thereon, and a second type semiconductor layer  40  is formed on the light-emitting layer  30 . When the first type semiconductor layer  20  is p-type semiconductor material, the second type semiconductor layer  40  can be n-second type semiconductor. Conversely, when the first type semiconductor layer  20  is n-type semiconductor material, the second type semiconductor layer  40  can be p-type semiconductor material. The light-emitting layer  30  can be intrinsic semiconductor material, p-type semiconductor material or n-type semiconductor material. When an electrical current flows through the first type semiconductor layer  20 , the light-emitting layer  30  and the second type semiconductor layer  40 , the light-emitting layer  30  can emit a light. When the light-emitting layer  30  is Al a Ga b In 1-a-b P, the light-emitting layer  30  can emit a red, orange or yellow light. When the light-emitting layer  30  is Al c Ga d In 1-c-d N, the light-emitting layer  30  can emit a blue or green light. 
     Each of the plurality of second portions  202  of the first type semiconductor layer  20  comprises a first surface  21 , a second surface  222  and a third surface  221 . The second type semiconductor layer  40  comprises a fifth surface  41  and a fourth surface  42 . The average roughness (Ra) of the first surface  21  and the fifth surface  41  is larger than 100 nm. The average roughness (Ra) of each of the second surface  222 , the third surface  221  and that of the fourth surface  42  is in a range of 10 nm to 100 nm, and preferably is smaller than 50 nm. The second surface  222  and the third surface  221  are flatter than the first surface  21 , and the fourth surface  42  is flatter than the fifth surface  41 . The average roughness (Ra) of the first surface  21  and that of the fifth surface  41  which are larger than 100 nm can reduce the total internal reflection of the light emitted from the light-emitting layer  30  to increase the light extraction efficiency. The second surface  222 , the third surface  221  and the fourth surface  42  are formed by regionally treating the first surface  21  and the fifth surface  41  at the same time with the same process, such as wet etching or dry etching, so the difference of the average roughness (Ra) between the fourth surface  42 , or the third surface  221 , and the second surface  222  is smaller than 50 nm. Thus, the depth of the second surface  222  or the third surface  221  related to the first surface  21  is the same as that of the fourth surface  42  related to the fifth surface  41 . The depth of the second surface  222  or the third surface  221  related to the first surface  21  is in a range of 2000 Å and 10000 Å, and preferably in a range of 4000 Å and 7000 Å. And, the depth of the fourth surface  42  related to the fifth surface  41  is also in a range of 2000 Å and 10000 Å, and preferably in a range of 4000 Å and 7000 Å. 
     The first electrical pad  23  is formed on the third surface  221  and ohmically contacts the first type semiconductor layer  20 . The second electrical pad  43  is formed on the fourth surface  42  and ohmically contacts the second type semiconductor layer  40 . The first electrical pad  23  and the second electrical pad  43  are operable for conducting an electrical current from outside to flow through the first type semiconductor layer  20 , the light-emitting layer  30 , and the second type semiconductor layer  40 . The material of the first electrical pad  23  and the second electrical pad  43  comprises the metal material, such as Cu, Al, In, Sn, Au, Pt, Zn, Ag, Ti, Ni, Pb, Pd, Ge, Cr, Cd, Co, Mn, Sb, Bi, Ga, Tl, Po, Ir, Re, Rh, Os, W, Li, Na, K, Be, Mg, Ca, Sr, Ba, Zr, Mo or La, or metal alloy, such as Ag—Ti, Cu—Sn, Cu—Zn, Cu—Cd, Sn—Pb—Sb, Sn—Pb—Zn, Ni—Sn, Ni—Co, Au alloy, or Ge—Au—Ni. Because the average roughness (Ra) of the second surface  222  is in a range of 10 nm to 100 nm, and preferably is smaller than 50 nm, the laser beam can penetrate the second surface  222  to focus in the interior of the transparent substrate  10  under the upper surface  101 . For the first surface  21 , because the average roughness (Ra) thereof is larger than 100 nm, the laser beam is scattered by the first surface  21  and fails to focus in the interior of the transparent substrate  10  under the upper surface  101 . Therefore, a laser beam can penetrate the second surface  222  and focus in the interior of the transparent substrate  10  to form the plurality of damage regions  1031 . 
     A reflective layer  50  is formed on the bottom surface  102  of the transparent substrate  10 . The reflective layer  50  can reflect the light emitted from the light-emitting layer  30  to increase the light extraction efficiency. The reflective layer  50  comprises a metal layer, DBR, or the combination thereof. The reflectivity of the reflective layer  50  is larger than 70% for a laser beam, of which the wavelength region is in a range of 350 nm and 500 nm, 350 nm and 800 nm, 350 nm and 1200 nm, 500 nm and 1000 nm, 700 nm and 1200 nm or 350 nm and 1500 nm. 
     Third Embodiment 
       FIGS. 3A to 3G  schematically show a method of manufacturing the light-emitting diode in accordance with an embodiment of the present application.  FIG. 3A  shows the first step of providing a substrate  10 . The transparent substrate  10  has an upper surface  101  and a bottom surface  102 . The material of the transparent substrate  10  comprises the transparent material, such as sapphire (Al 2 O 3 ), GaN, SiC, AlN, ZnO or MgO, SiO 2 , B 2 O 3  or BaO, so the transparent substrate  10  can be penetrated by a laser beam to focus interior thereof. 
       FIG. 3B  shows the step of forming a first type semiconductor layer  20 , a light-emitting layer  30 , and a second type semiconductor layer  40  sequentially. The second type semiconductor layer  40  comprises a fifth surface  41 , and the average roughness (Ra) of the fifth surface  41  is larger than 100 nm. When the first type semiconductor layer  20  is p-type semiconductor material, the second type semiconductor layer  40  can be n-second type semiconductor. Conversely, when the first type semiconductor layer  20  is n-type semiconductor material, the second type semiconductor layer  40  can be p-type semiconductor material. The light-emitting layer  30  can be intrinsic semiconductor material, p-type semiconductor material or n-type semiconductor material. When an electrical current flows through the first type semiconductor layer  20 , the light-emitting layer  30 , and the second type semiconductor layer  40 , the light-emitting layer  30  can emit a light. When the light-emitting layer  30  is Al a Ga b In 1-a-b P, the light-emitting layer  30  can emit a red, orange or yellow light. When the light-emitting layer  30  is Al c Ga d In 1-c-d N, the light-emitting layer  30  can emit a blue or green light. 
       FIG. 3C  shows the step of pattern-etching of the second type semiconductor layer  40 , the light-emitting layer  30 , and the first type semiconductor layer  20  to reveal a first surface  21  on the first type semiconductor layer  20  by dry etching or wet etching. The average roughness (Ra) of the first surface  21  is larger than 100 nm. 
       FIG. 3D  shows the step of treating the first surface  21  and the fifth surface  41  to form a plurality of fourth surfaces  42 , a plurality of second surfaces  222  and a plurality of third surfaces  221  by dry etching or wet etching. The step of treating the first surface  21  and the fifth surface  41  comprises forming a patterned photoresist on the first surface  21  and the fifth surface  41 , etching the first surface  21  and the fifth surface  41  where is uncovered by the patterned photoresist, and removing the patterned photoresist. Etching the first surface  21  and the fifth surface  41  comprises dry etching or wet etching. The depth of each of the plurality of second surfaces  222 , or the plurality of third surfaces  221 , related to the first surface  21  is in a range of 2000 Å and 10000 Å, and preferably is in a range of 4000 Å and 7000 Å. And, the depth of each of the plurality of fourth surfaces  42  related to the fifth surface  41  is also in a range of 2000 Å and 10000 Å, and preferably is in a range of 4000 Å and 7000 Å. The average roughness (Ra) of each of the plurality of the second surfaces  222 , the plurality of the third surfaces  221  and the plurality of the fourth surfaces  42  is in a range of 10 nm to 100 nm, and preferably is smaller than 50 nm. The second surface  222  is used for defining a plurality of units  1 . 
       FIG. 3E  shows the step of forming a second electrical pad  43  on each of the plurality of fourth surfaces  42  and a first electrical pad  23  on each of the third surfaces  221 , and then forming a reflective layer  50  on the bottom surface  102 . The reflective layer  50  comprises a metal layer, DBR, or the combination thereof and has a reflectivity larger than 70%. The thickness of the reflective layer  50  is smaller than 5 μm, and preferably is in a range of 2 μm to 3 μm. Before forming the reflective layer  50  on the bottom surface  102 , the transparent substrate  10  is thinned to a range of 90 μm to 150 μm by polish, such as CMP. The plurality of first electrical pad  23  and the second electrical pad  43  are operable for conducting an electrical current from outside to flow through the first type semiconductor layer  20 , the light-emitting layer  30 , and the second type semiconductor layer  40 . The material of the first electrical pad  23  and the second electrical pad  43  comprises the metal material, such as Cu, Al, In, Sn, Au, Pt, Zn, Ag, Ti, Ni, Pb, Pd, Ge, Cr, Cd, Co, Mn, Sb, Bi, Ga, Tl, Po, Ir, Re, Rh, Os, W, Li, Na, K, Be, Mg, Ca, Sr, Ba, Zr, Mo or La, or metal alloy, such as Ag—Ti, Cu—Sn, Cu—Zn, Cu—Cd, Sn—Pb—Sb, Sn—Pb—Zn, Ni—Sn, Ni—Co, Au alloy, or Ge—Au—Ni. 
       FIG. 3F  shows the step of forming a plurality of damage regions  1031  in the transparent substrate  10  under the second surface  222  by providing a laser beam  8 . The wavelength range of the laser beam  8  comprises 350-500, 350-800, 350-1200, 500-1000, 700-1200 or 350-1500 nm. Because the average roughness (Ra) of the second surface  222  is in a range of 10 nm to 100 nm, and preferably is smaller than 50 nm, the laser beam  8  can penetrate the second surface  222  and focus in the interior of the transparent substrate  10  to cut the transparent substrate  10  without damaging the first type semiconductor layer  20 . For the first surface  21 , because the average roughness (Ra) thereof is larger than 100 nm, the laser beam  8  is scattered by the first surface  21  and fail to focus in the interior of the transparent substrate  10  under the upper surface  101 . 
       FIG. 3G  shows the step of providing a cutter  9  for cleaving the first type semiconductor layer  20 , the transparent substrate  10  and the reflective layer  50  along the second surface  222  and through the plurality of damage regions  1031  in the transparent substrate  10  under the second surface  222 . The plurality of units  1  can be separated to form a plurality of light-emitting diodes. 
     Fourth Embodiment 
     Referring to  FIG. 4 , a light bulb in accordance with an embodiment of the present application is disclosed. The bulb  600  includes a cover  602 , a lens  604 , a lighting module  610 , a lamp holder  612 , a heat sink  614 , a connecting part  616 , and an electrical connector  618 . The lighting module  610  includes a carrier  606  and a plurality of light-emitting elements  608  of any one of the above mentioned embodiments on the carrier  606 . 
     The foregoing description of preferred and other embodiments in the present disclosure is not intended to limit or restrict the scope or applicability of the inventive concepts conceived by the Applicant. In exchange for disclosing the inventive concepts contained herein, the Applicant desires all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.