Abstract:
A light-emitting device comprises a semiconductor layer sequence comprising a first semiconductor layer having a first electrical conductivity, a second semiconductor layer having a second electrical conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer; a plurality of protruding structures; a plurality of beveled trenches in the semiconductor layer sequence and respectively accommodating the plurality of protruding structures; a dielectric layer on the second semiconductor layer and an inner sidewall of the plurality of beveled trenches, wherein the dielectric layer comprises a surface perpendicular to a thickness direction of the semiconductor layer sequence; a metal layer formed along the inner sidewall of the plurality of beveled trenches and extending to the surface of the dielectric layer, wherein the metal layer is insulated from the second semiconductor layer by the dielectric layer; and a first electrode formed on the plurality of protruding structures.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 14/093,924, filed on Dec. 2, 2013, now pending, which claims the right of priority based on U.S. application Ser. No. 13/221,369, filed on Aug. 30, 2011, and U.S. provisional application Ser. No. 61/378,197, filed on Aug. 30, 2010, and the contents of which are hereby incorporated by references in their entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    The application relates to a light-emitting device, and more particularly, to a light-emitting device with a connection structure. 
       DESCRIPTION OF BACKGROUND ART 
       [0003]    The light-emitting diode (LED) is a solid state semiconductor device, which has been broadly used as a light-emitting device. The light-emitting device structure at least comprises a p-type semiconductor layer, an n-type semiconductor layer, and an active layer. The active layer is formed between the p-type semiconductor layer and the n-type semiconductor layer. The structure of the light-emitting device generally comprises III-V group compound semiconductor such as gallium phosphide, gallium arsenide, or gallium nitride. The light-emitting principle of the LED is the transformation of electrical energy to optical energy by applying electrical current to the p-n junction to generate electrons and holes. Then, the LED emits light when the electrons and the holes combine. 
         [0004]      FIG. 1  illustrates a cross-sectional diagram of a conventional light-emitting device before bonding process. The light-emitting device comprises a semiconductor layer sequence  10   a  provided with a first main side  18  and a second main side  181 , comprising a first semiconductor layer  11 , a second semiconductor layer  13 , and an active layer  12  formed between the first semiconductor layer  11  and the second semiconductor layer  13 , which can produce electromagnetic radiation. A trench is formed in the semiconductor layer sequence  10   a  by wet etch or dry etch. A dielectric layer  14  is formed on the inner sidewall of the trench to electrically insulate the second semiconductor layer  13  and the active layer  12 . Then, an electrically conductive material is filled into the insulated trench, so a first metal layer  15  is formed. A reflecting layer  16  is formed between the semiconductor layer sequence  10   a  and the dielectric layer  14 . A void  17  is an area not occupied by the first metal layer  15 . A first connection layer  101  formed on a carrier substrate  102  is used to connect the first metal layer  15 . The first connection layer  101  and the first metal layer  15  are connected together in an electrically conductive manner. As shown in  FIG. 1 , after forming the first connection layer  101  and the first metal layer  15 , the semiconductor layer sequence  10   a  is connected to the carrier substrate  102  by metal bonding or glue bonding. 
         [0005]      FIG. 2A  illustrates a cross-sectional diagram of a conventional light-emitting device  20 . As shown in  FIG. 2A , connecting failure problem arises in the bonding process.  FIG. 2A  shows the result of the bonding process after a first metal layer  25  is connected to a first connection layer  201 . However, because the trench is deep, it is not easy to fill the trench with electrically conductive material, and the profile of the trench is concave after the filling process. While the first metal layer  25  is connected to the first connection layer  201  of a carrier substrate  202 , a void  204  is formed between the first metal layer  25  and the first connection layer  201 . Thus, the connection area between the first metal layer  25  and the first connection layer  201  is small and the resistance of the light-emitting device  20  is therefore raised. As shown in  FIG. 2B , the peripheral area of the trench  200  is occupied by the first metal layer  25 , and the internal area not occupied by the first metal layer  25  forms the void  204 . 
       SUMMARY OF THE APPLICATION 
       [0006]    An object of the present application is to reduce the size of the void formed in the filling process of the trench and increase the connection area between the first metal layer and the first connection layer of the carrier substrate for electrical characteristics and light emission efficiency improvement. 
         [0007]    A light-emitting device of an embodiment of the present application comprises a semiconductor layer sequence provided with a first main side, a second main side, and an active layer; a beveled trench formed in the semiconductor layer sequence, having a top end close to the second main side, a bottom end, and an inner sidewall connecting the top end and the bottom end. In the embodiment, the inner sidewall is an inclined surface. The light-emitting device further comprises a dielectric layer disposed on the inner sidewall of the beveled trench and the second main side; a first metal layer formed on the dielectric layer; a carrier substrate; and a first connection layer connecting the carrier substrate and the semiconductor layer sequence. 
         [0008]    A light-emitting device comprises a semiconductor layer sequence comprising a first semiconductor layer having a first electrical conductivity, a second semiconductor layer having a second electrical conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer; a plurality of protruding structures; a plurality of beveled trenches in the semiconductor layer sequence and respectively accommodating the plurality of protruding structures; a dielectric layer on the second semiconductor layer and an inner sidewall of the plurality of beveled trenches, wherein the dielectric layer comprises a surface perpendicular to a thickness direction of the semiconductor layer sequence; a metal layer formed along the inner sidewall of the plurality of beveled trenches and extending to the surface of the dielectric layer, wherein the metal layer is insulated from the second semiconductor layer by the dielectric layer; and a first electrode formed on the plurality of protruding structures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  illustrates a cross-sectional diagram of a conventional light-emitting device before bonding process; 
           [0010]      FIG. 2A  illustrates a cross-sectional diagram of a conventional light-emitting device; 
           [0011]      FIG. 2B  illustrates a top-view diagram of a trench shown in  FIG. 2A ; 
           [0012]      FIG. 3A  illustrates a cross-sectional diagram according to the first embodiment of the present application; 
           [0013]      FIG. 3B  illustrates a top-view diagram of a beveled trench shown in  FIG. 3A ; 
           [0014]      FIG. 4A  illustrates a cross-sectional diagram according to the second embodiment of the present application; 
           [0015]      FIG. 4B  illustrates a top-view diagram of a beveled trench shown in  FIG. 4A ; 
           [0016]      FIG. 5A  illustrates a cross-sectional diagram according to the third embodiment of the present application; and 
           [0017]      FIG. 5B  illustrates a top-view diagram of a beveled trench shown in  FIG. 5A . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]    The embodiment of the application is illustrated in detail, and is plotted in the drawings. The same or the similar part is illustrated in the drawings and the specification with the same number. 
         [0019]      FIG. 3A  illustrates a cross-sectional diagram of a light-emitting device  30  according to the first embodiment of the present application. In the embodiment, the light-emitting device  30  comprises a semiconductor layer sequence  30   a  provided with a first main side  39 , a second main side  391 , and an active layer  32 ; a beveled trench formed in the semiconductor layer sequence  30   a,  having a top end  306  close to the second main side  391 , a bottom end  305 , and an inner sidewall  307  connecting the top end  306  and the bottom end  305 . In the embodiment, the inner sidewall  307  is an inclined surface. The light-emitting device  30  further comprises a dielectric layer  34  disposed on the inner sidewall  307  of the beveled trench and the second main side  391 ; a first metal layer  35  formed on the dielectric layer  34 ; a carrier substrate  302 ; and a first connection layer  301  connecting the carrier substrate  302  and the semiconductor layer sequence  30   a.  The semiconductor layer sequence  30   a  further comprises a first semiconductor layer  31  having a first electrical conductivity formed near the first main side  39 , and a second semiconductor layer  33  having a second electrical conductivity formed near the second main side  391 , wherein the active layer  32  is interposed between the first semiconductor layer  31  and the second semiconductor layer  33 . The material of the active layer  32  can comprise InGaN-based material, AlGaAs-based material, or AlInGaP-based material. 
         [0020]    The beveled trench is formed in the semiconductor layer sequence  30   a  by wet etch or dry etch. The bottom end  305  of the beveled trench is formed in the first semiconductor layer  31  of the semiconductor layer sequence  30   a,  and the top end  306  of the beveled trench is formed close to the second main side  391 . The area near the top end  306  of the beveled trench is larger than the area near the bottom end  305  of the beveled trench. The dielectric layer  34  is formed on the inner sidewall  307  of the beveled trench to electrically insulate the second semiconductor layer  33  and the active layer  32 . The material of the dielectric layer  34  comprises silicon oxide, silicon nitride, magnesium oxide, tantalum oxide, titanium oxide, or polymer. In addition, in order to increase the luminous efficiency, a reflecting layer  36  is interposed between the semiconductor layer sequence  30   a  and the dielectric layer  34 . The material of the reflecting layer  36  comprises metal or metal alloy. 
         [0021]    Then, the beveled trench is filled by the first metal layer  35 . The material of the first metal layer  35  comprises metal like Ni, Au, Ti, Cr, Au, Zn, Al, Pt, or the combination thereof. During the filling process of the first metal layer  35 , a concave area is formed. Thus, a second filling process of the beveled trench is performed via an additional local electro-plating process, wherein the first metal layer  35  functions as the seed layer, and a conductive protruding structure  38  is formed selectively on the concave area of the beveled trench by the electro-plating process. The material of the conductive protruding structure  38  comprises conductive metal like Ni, Au, Ti, Cr, Au, Zn, Al, Pt, or the combination thereof. Therefore, the total connecting area between the first metal layer  35  and the first connection layer  301  is enlarged as shown in  FIG. 3B  compared with  FIG. 2B , and the connection resistance can be reduced. As shown in  FIG. 3B , the top view of the beveled trench  300  is circular or elliptic, and the top view of the conductive protruding structure  38  is circular or elliptic. The circumference of the conductive protruding structure  38  is smaller than the circumference of the beveled trench. The conductive protruding structure  38  is accommodated in the beveled trench. A void  304  disposed between the first metal layer  35  and the conductive protruding structure  38  is not filled by the first metal layer  35  or the material of the conductive protruding structure  38 . As shown in  FIG. 3B , the peripheral area of the beveled trench  300  is occupied by the first metal layer  35 , the internal area of the beveled trench  300  is occupied by the conductive protruding structure  38 , and the void  304  is formed between the first metal layer  35  and the conductive protruding structure  38 . With the conductive protruding structure  38 , the total connection area between the first metal layer  35  and the first connection layer  301  is enlarged as shown in  FIG. 3B  compared with  FIG. 2B , and the connection resistance is reduced. 
         [0022]    After forming the first metal layer  35  and the conductive protruding structure  38 , the semiconductor layer sequence  30   a  is connected to the carrier substrate  302  by the first connection layer  301 . The material of the first connection layer  301  comprises metal like Au, Sn, Cr, Zn, Ni, Ti, Pt, or the combination thereof. The carrier substrate  302  is a conductive substrate comprising metal or metal alloy like Cu, Al, Sn, Zn, Cd, Ni, Co, W, Mo, or the combination thereof The light-emitting device  30  according to the embodiment of the present application further comprises a first electrode  303  formed on the carrier substrate  302  and electrically connected to the first semiconductor layer  31 , and a second electrode  37  electrically connected to the second semiconductor layer  33 . 
         [0023]      FIG. 4A  illustrates a cross-sectional diagram of a light-emitting device  40  according to the second embodiment of the present application. In the embodiment, the light-emitting device  40  comprises a semiconductor layer sequence  40   a  provided with a first main side  49 , a second main side  491 , and an active layer  42 ; a beveled trench formed in the semiconductor layer sequence  40   a  having a top end  406  close to the second main side  491 , a bottom end  405 , and an inner sidewall  407  connecting the top end  406  and the bottom end  405 . In the embodiment, the inner sidewall  407  is an inclined surface. The light-emitting device  40  further comprises a dielectric layer  44  disposed on the inner sidewall  407  of the beveled trench and the second main side  491 ; a first metal layer  45  formed on the dielectric layer  44 ; a carrier substrate  402 ; and a first connection layer  401  connecting the carrier substrate  402  and the semiconductor layer sequence  40   a.  The semiconductor layer sequence  40   a  further comprises a first semiconductor layer  41  having a first electrical conductivity formed near the first main side  49 , and a second semiconductor layer  43  having a second electrical conductivity formed near the second main side  491 , wherein the active layer  42  is interposed between the first semiconductor layer  41  and the second semiconductor layer  43 . The material of the active layer  42  can comprise InGaN-based material, AlGaAs-based material, or AlInGaP-based material. 
         [0024]    The beveled trench is formed in the semiconductor layer sequence  40   a  by wet etch or dry etch. The bottom end  405  of the beveled trench is formed in the first semiconductor layer  41  of the semiconductor layer sequence  40   a,  and the top end  406  of the beveled trench is formed close to the second main side  491 . The area near the top end  406  of the beveled trench is larger than the area near the bottom end  405  of the beveled trench. Partial of the semiconductor layer sequence  40   a  in the beveled trench is remained by the conventional lithography and etch method, that is, there is a conductive protruding structure  48  formed in the beveled trench. The conductive protruding structure  48  comprises a layer sequence substantially comprising the same material as the semiconductor layer sequence  40   a.  The material of the layer sequence of the conductive protruding structure  48  comprises one or more than one element selecting from a group consisting of gallium (Ga), aluminum (Al), indium (In), phosphor (P), nitrogen (N), zinc (Zn), cadmium (Cd), arsenide (As), silicon (Si), and selenium (Se). Because not all of the semiconductor layers in the beveled trench are etched away, the space needed to be filled is not deep as the structure shown in  FIG. 2A , and it is easier for the first metal layer  45  to fill the space in the beveled trench. The material of the first metal layer  45  comprises Ni, Au, Ti, Cr, Au, Zn, Al, Pt, or the combination thereof. Similarly, the total connecting area between the first metal layer  45  and the first connection layer  401  is enlarged as shown in  FIG. 4B  compared with  FIG. 2B  and the connection resistance can be reduced. As shown in  FIG. 4B , the top view of the beveled trench  400  is circular or elliptic, and the top view of the conductive protruding structure  48  is circular or elliptic. The circumference of the conductive protruding structure  48  is smaller than the circumference of the beveled trench  400 . A void  404  disposed in the first metal layer  45  is not filled by the first metal layer  45  or the material of the conductive protruding structure  48 . As shown in  FIG. 4B , the peripheral area of the beveled trench  400  is occupied by the first metal layer  45 , the internal area  45 ′ of the beveled trench  400  is occupied by the same material of the first metal layer  45 , and the void  404  is formed in the first metal layer  45 . With the conductive protruding structure  48 , the total connection area between the first metal layer  45  and the first connection layer  401  is enlarged as shown in  FIG. 4B  compared with  FIG. 2B , and the connection resistance is reduced. 
         [0025]    The dielectric layer  44  is formed on the inner sidewall  407  of the beveled trench and the surface of the conductive protruding structure  48  to electrically insulate the second semiconductor layer  43  and the active layer  42 . The material of the dielectric layer  44  comprises silicon oxide, silicon nitride, magnesium oxide, tantalum oxide, titanium oxide, or polymer. In addition, in order to increase the luminous efficiency, a reflecting layer  46  is interposed between the semiconductor layer sequence  40   a  and the dielectric layer  44 . The material of the reflecting layer  46  comprises metal or metal alloy. 
         [0026]    After forming the first metal layer  45  and the conductive protruding structure  48 , the semiconductor layer sequence  40   a  is connected to the carrier substrate  402  by the first connection layer  401 . The material of the first connection layer  401  comprises metal like Au, Sn, Cr, Zn, Ni, Ti, Pt, or the combination thereof. The carrier substrate  402  is a conductive substrate comprising metal or metal alloy like Cu, Al, Sn, Zn, Cd, Ni, Co, W, Mo, or the combination thereof The light-emitting device  40  according to the embodiment of the present application further comprises a first electrode  403  formed on the carrier substrate  402  and electrically connected to the first semiconductor layer  41 , and a second electrode  47  electrically connected to the second semiconductor layer  43 . 
         [0027]      FIG. 5A  illustrates a cross-sectional diagram of a light-emitting device  50  according to the third embodiment of the present application. In the embodiment, the light-emitting device  50  comprises a semiconductor layer sequence  50   a  provided with a first main side  60 , a second main side  601 , and an active layer  52 ; a beveled trench formed through the semiconductor layer sequence  50   a,  having a top end  506  close to the second main side  601 , a bottom end  505 , and an inner sidewall  507  connecting the top end  506  and the bottom end  505 . In the embodiment, the inner sidewall  507  is an inclined surface. The light-emitting device  50  further comprises a dielectric layer  54  disposed on the inner sidewall  507  of the beveled trench and the second main side  601 ; a first metal layer  55  formed on the dielectric layer  54 ; a carrier substrate  502 ; and a first connection layer  501  connecting the carrier substrate  502  and the semiconductor layer sequence  50   a.  The semiconductor layer sequence  50   a  further comprises a first semiconductor layer  51  having a first electrical conductivity formed near the first main side  60  of the semiconductor layer sequence  50   a,  and a second semiconductor layer  53  having a second electrical conductivity formed near the second main side  601  of the semiconductor layer sequence  50   a,  wherein the active layer  52  is interposed between the first semiconductor layer  51  and the second semiconductor layer  53 . The material of the active layer  52  can comprise InGaN-based material, AlGaAs-based material, or AlInGaP-based material. 
         [0028]    During the filling process of the beveled trench, the beveled trench cannot be fully filled with the conductive material because there is some gas remained in the beveled trench. After the conductive material is filled into the beveled trench, the conductive material is solidified by cooling. In the cooling process, the gas goes out and the concave area forms. Therefore, in the embodiment of the present application, the beveled trench is formed through the semiconductor layer sequence  50   a  by wet etch or dry etch. The area near the top end  506  of the beveled trench is larger than the area near the bottom end  505  of the beveled trench. The bottom end  505  of the beveled trench is formed on the first main side  60 , and the top end  506  of the beveled trench is formed near the second main side  601 . 
         [0029]    The dielectric layer  54  is formed on the inner sidewall  507  of the beveled trench to electrically insulate the second semiconductor layer  53  and the active layer  52 . The material of the dielectric layer  54  comprises silicon oxide, silicon nitride, magnesium oxide, tantalum oxide, titanium oxide, or polymer. In addition, in order to increase the luminous efficiency, a reflecting layer  56  is interposed between the semiconductor layer sequence  50   a  and the dielectric layer  54 . The material of the reflecting layer  56  comprises metal or metal alloy. 
         [0030]    In the light-emitting device  50  of the present application, there is no remaining gas left in the beveled trench, and the first metal layer  55  can overflow the whole beveled trench to make a back connection  59 . The back connection  59  comprising the same material as the first metal layer  55  is formed on the first main side  60  and electrically connected to the first semiconductor layer  51 . That is, the first semiconductor layer  51  is electrically connected to the first connection layer  501  by the first metal layer  55  through the first main side  60  without any vacant space there between. Therefore, the total connecting area between the first metal layer  55  and the first connection layer  501  is enlarged as shown in  FIG. 5B  compared with  FIG. 2B , and the connection resistance can be reduced. As shown in  FIG. 5B , the top view of the beveled trench  500  is circular or elliptic, and the beveled trench  500  is fully filled by the first metal layer  55  without any vacant space. 
         [0031]    After forming the first metal layer  55  in the beveled trench, the semiconductor layer sequence  50   a  is connected to the carrier substrate  502  by the first connection layer  501 . The material of the first connection layer  501  comprises metal like Au, Sn, Cr, Zn, Ni, Ti, Pt, or the combination thereof. The carrier substrate  502  is a conductive substrate comprising metal or metal alloy like Cu, Al, Sn, Zn, Cd, Ni, Co, W, Mo, or the combination thereof. 
         [0032]    The light-emitting device  50  according to the embodiment of the present application further comprises a first electrode  503  formed on the carrier substrate  502  and electrically connected to the first semiconductor layer  51 , and a second electrode  57  electrically connected to the second semiconductor layer  53 . 
         [0033]    The principle and the efficiency of the present application illustrated by the embodiments above are not the limitation of the application. Any person having ordinary skill in the art can modify or change the aforementioned embodiments. Therefore, the protection range of the rights in the application will be listed as the following claims.