Abstract:
An LED and manufacturing method therefor. The LED comprises a compound semiconductor structure having first and second compound layers and active layer, first and second electrode layers atop the second compound semiconductor layer and connected to the two compound. An insulating layer is coated in regions other than where the first and second electrode layers are located. A conducting adhesive layer is formed atop the non-conductive substrate, connecting the same to the first electrode layer and insulating layer. Formed on one side surface of the non-conductive substrate and adhesive layer is a first electrode connection layer connected to the conducting adhesive layer. A second electrode connection layer on the other side surface is connected to the second electrode layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2010-0113478, filed on Nov. 15, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to light-emitting devices and methods of manufacturing the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Light-emitting devices, such as light-emitting diodes (LEDs), refer to semiconductor devices that may create various colors of light by constituting a light source through a PN junction of a compound semiconductor. For example, nitride-based LEDs using III-V compound semiconductors such as GaN, InN, and AlN are widely used as light-emitting devices for emitting blue light. Such light-emitting devices have advantages in that they have a long lifespan, are easily made small and light, have a strong directivity of light, and are driven at a low voltage. Also, such light-emitting devices may be applied in various fields because they are strong against impact and vibration, do not need to be preheated, are driven simply, and are packaged in various forms. 
         [0006]    There is suggested vertical light-emitting devices which are formed by stacking compound semiconductor layers on an insulating substrate, such as a sapphire substrate that is known to be the most likely substrate satisfying lattice matching conditions for crystal growth, and removing the insulating substrate. Such vertical light-emitting devices are divided into vertical light-emitting devices in which an n-type electrode and a p-type electrode are disposed on the same surface of a compound semiconductor structure and vertical light-emitting devices in which an n-type electrode and a p-type electrode are disposed on different surfaces of a compound semiconductor structure. The vertical light-emitting devices in which the n-type electrode and the p-type electrode are disposed on the same surface of the compound semiconductor structure have advantages in that current spreading is improved and a light passage is prevented from being blocked by the electrodes. 
       SUMMARY 
       [0007]    Provided are light-emitting devices and methods of manufacturing the same which facilitate a manufacturing process and reduce manufacturing cost by forming a connection layer on a side surface of a light-emitting device. 
         [0008]    Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
         [0009]    According to an aspect of the present invention, a light-emitting device includes: a compound semiconductor structure which includes a first compound semiconductor layer, an active layer, and a second compound semiconductor layer; a first electrode layer and a second electrode layer which are disposed on a top surface of the second compound semiconductor layer and are respectively electrically connected to the first compound semiconductor layer and the second compound semiconductor layer; an insulating layer which is coated on a portion other than portions where the first electrode layer and the second electrode layer are located; a conducting adhesive layer which is formed on a top surface of a non-conductive substrate and connects the non-conductive substrate to the first electrode layer and the insulating layer; a first electrode connection layer which is formed on one side surfaces of the non-conductive substrate and the conducting adhesive layer and is connected to the conducting adhesive layer; and a second electrode connection layer which is formed on the other side surfaces of the non-conductive substrate and the conducting adhesive layer and is connected to the second electrode layer. 
         [0010]    According to another aspect of the present invention, a method of manufacturing a light-emitting device includes: forming a compound semiconductor structure by stacking a first compound semiconductor layer, an active layer, and a second compound semiconductor layer on a substrate; forming a first electrode layer and a second electrode layer, which are respectively electrically connected to the first compound semiconductor layer and the second compound semiconductor layer, on a top surface of the compound semiconductor structure; coating an insulating layer on a portion other than portions where the first electrode layer and the second electrode layer are located; adhering a non-conductive substrate to the insulating layer and the first electrode layer by using a conducting adhesive layer; exposing a portion of the conducting adhesive layer and a portion of a top surface of the second electrode layer; connecting a first electrode connection layer to the conducting adhesive layer; and connecting a second electrode connection layer to the second electrode layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0012]      FIG. 1  is a cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a cross-sectional view of a light-emitting device according to another embodiment of the present invention; and 
           [0014]      FIGS. 3 through 15  are cross-sectional views for explaining a method of manufacturing the light-emitting device of  FIG. 1 , according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  is a cross-sectional view of a light-emitting device according to an embodiment of the present invention. 
         [0016]    Referring to  FIG. 1 , the light-emitting device includes a compound semiconductor structure  110  and an electrode structure disposed on both side surfaces of the compound semiconductor structure  110 . 
         [0017]    The compound semiconductor structure  110  includes a first compound semiconductor layer  111 , an active layer  112 , and a second compound semiconductor layer  113  which are grown on a predetermined substrate  100  (see  FIG. 4 ). The substrate  100  may be removed as will be described below (see  FIG. 12 ). 
         [0018]    The compound semiconductor structure  110  may be a nitride semiconductor diode which is formed by growing III-V compound semiconductors such as GaN, InN, and AlN. Such nitride semiconductors may be formed by using an insulating substrate such as a sapphire substrate that is known to be the most likely substrate satisfying lattice matching conditions for crystal growth. The first compound semiconductor layer  111  may have n-type conductivity, and the second compound semiconductor layer  113  may have p-type conductivity. If needed, the first compound semiconductor layer  111  may have p-type conductivity, and the second compound semiconductor layer  113  may have n-type conductivity. The active layer  112  is disposed between the first compound semiconductor layer  111  and the second compound semiconductor layer  113 . The active layer  112  may have, for example, a multi-quantum well structure. The multi-quantum well structure may include a plurality of quantum well layers and a plurality of quantum barrier layers formed between the quantum well layers. In detail, if the compound semiconductor structure  110  is a gallium nitride-based light-emitting diode, the first compound semiconductor layer  111  may be formed of GaN doped with a p-type impurity, the second compound semiconductor layer  113  may be formed of GaN doped with a p-type impurity, and the active layer  112  may be formed by stacking a plurality of quantum well layers formed of InGaN and a plurality of quantum barrier layers formed of GaN. Electrons and holes injected through the first compound semiconductor layer  111  and the second compound semiconductor layer  113  combine with each other in the active layer  112  to emit light L. 
         [0019]    The electrode structure includes a first electrode layer  130  and a second electrode layer  140  disposed on the second compound semiconductor  113 , and a first electrode connection layer  181  and a second electrode connection layer  182  respectively electrically connected to the first electrode layer  130  and the second electrode layer  140 . 
         [0020]    The first electrode layer  130  is electrically connected to the first compound semiconductor layer  111  through a via-hole  110   a  (see  FIG. 4 ) extending from the second compound semiconductor layer  113  to the first compound semiconductor layer  111 . The via-hole  110   a  may be formed to have a mesa structure or a vertical structure by using etching. One or more via-holes  110   a  may be formed. 
         [0021]    The second electrode layer  140  is disposed on the second compound semiconductor layer  113  and is electrically connected to the second compound semiconductor layer  113 . The second electrode layer  140  may be disposed on a portion of the second compound semiconductor layer  113  where the via-hole  110   a  is not formed. 
         [0022]    The insulating layer  120  is coated on a portion other than portions of a top surface of the compound semiconductor structure  110  where the second electrode layer  140  and the first electrode layer  130  are formed. The first electrode layer  130  is insulated from the active layer  112 , the second compound semiconductor layer  113 , and the second electrode layer  140  due to the insulating layer  120 . 
         [0023]    A conducting adhesive layer  150  is coated on a top surface of a non-conductive substrate  160 , and the non-conductive substrate  160  is adhered to bottom surfaces of the first electrode layer  130  and the insulating layer  120  by applying a predetermined heat and pressure. 
         [0024]    A portion of a top surface of the conducting adhesive layer  150  and a portion of a top surface of the second electrode layer  140  are exposed to the outside. The first electrode connection layer  181  and the second electrode connection layer  182  are disposed on both side surfaces of the non-conductive substrate  160  and the conducting adhesive layer  150 . The first electrode connection layer  181  contacts one of the side surfaces of the conducting adhesive layer  150  and the non-conductive substrate  160 , and one end of the first electrode connection layer  181  contacts the exposed portion of the top surface of the conducting adhesive layer  150 . The second electrode connection layer  182  is disposed to surround the other side surfaces of the conducting adhesive layer  150  and the non-conductive substrate  160 , and one end of the second electrode connection layer  182  contacts the exposed portion of the top surface of the second electrode layer  140 . 
         [0025]    The first electrode connection layer  181  and the second electrode connection layer  182  may be formed by depositing a metal, and the metal may be deposited by using E-beam, sputtering, or plating. 
         [0026]    In this case, if both the first electrode connection layer  181  and the second electrode connection layer  182  contact the conducting adhesive layer  150 , the first electrode connection layer  181  and the second electrode connection layer  182  are connected and short-circuited. In order to prevent this, an insulating film  170  is disposed between the second electrode connection layer  182 , and the non-conductive substrate  160  and the conducting adhesive layer  150 . Since the insulating film  170  is disposed to directly contact the side surfaces of the non-conductive substrate  160 , the conducting adhesive layer  150 , and the second electrode layer  140 , the second electrode connection layer  182  is prevented from contacting the non-conductive substrate  160  and the conducting adhesive layer  150 . The insulating film  170  may be formed of SiOx or SixNy, or polymer, polyimide, or epoxy-based material. 
         [0027]    Accordingly, the first electrode connection layer  181  is electrically connected to the first electrode layer  130  through the conducting adhesive layer  150 , the second electrode connection layer  182  is electrically connected to the second electrode layer  140 , and the first electrode connection layer  181  and the second electrode connection layer  182  are short-circuited due to the insulating film  170 . 
         [0028]    A package  200  is adhered to a bottom surface of the non-conductive substrate  160  using a conductive adhesive layer  183 . In this case, the first electrode connection layer  181  and the second electrode connection layer  182  are electrically connected to the conductive adhesive layer  183  by contacting the conductive adhesive layer  183 . A via-hole  210  is formed in the package  200  and the conductive adhesive layer  183  to reach the non-conductive substrate  160 . Accordingly, the first electrode connection layer  181  and the second electrode connection layer  182  are short-circuited due to the via-hole  210 . A protective layer  190  is formed to surround the compound semiconductor structure  110 . 
         [0029]      FIG. 2  is a cross-sectional view of a light-emitting device according to another embodiment of the present invention. 
         [0030]    Referring to  FIG. 2 , the light-emitting device is basically identical to the light-emitting device of  FIG. 1  in configuration. However, a protective layer  290  is formed to surround not only the compound semiconductor structure  110  but also portions of the first electrode connection layer  181 , the second electrode connection layer  182 , and the conductive adhesive layer  183  which are exposed. The protective layers  190  and  290  for protecting the compound semiconductor structure  110  and so on from the external environment may be formed of a transparent material through which light is transmitted so as not to disturb light extraction. 
         [0031]    In the above configurations, since it is difficult and costly to form a via-hole in the non-conductive substrate  160 , the via-hole may not be formed in the non-conductive substrate  160  as shown in the embodiments. A manufacturing process may be facilitated and manufacturing cost may be reduced by forming an electrode on a side surface of the non-conductive substrate  160 . 
         [0032]      FIGS. 3 through 15  are cross-sectional views for explaining a method of manufacturing the light-emitting device of  FIG. 1 , according to an embodiment of the present invention. Although one light-emitting device is manufactured for convenience of explanation in  FIGS. 3 through 15 , a plurality of light-emitting devices may be actually integrally formed on a wafer and then may be cut into individual light-emitting devices. 
         [0033]    Referring to  FIG. 3 , the compound semiconductor structure  110  is formed by sequentially growing the first compound semiconductor layer  111 , the active layer  112 , and the second compound semiconductor layer  113  on a top surface of the substrate  100 . 
         [0034]    The substrate  100  may be one suitable for a compound semiconductor to be grown by using crystal growth. For example, if a nitride semiconductor single crystal is to be grown, the substrate  100  may be selected from a sapphire substrate, a zinc oxide (ZnO) substrate, a gallium nitride (GaN) substrate, a silicon carbide (SiC) substrate, and an aluminum nitride (AlN) substrate. Although not shown in  FIG. 2 , a buffer layer (not shown) may be formed between the substrate  100  and the first compound semiconductor layer  111 . The buffer layer, which is a layer for improving lattice matching with the substrate  100  before growing the first compound semiconductor layer  111 , may be generally formed of AlN/GaN. 
         [0035]    The compound semiconductor structure  110  may be formed by growing III-V compound semiconductors such as GaN, InN, or AlN by using crystal growth. For example, if the compound semiconductor structure  110  is a gallium nitride-based light-emitting diode, the first compound semiconductor layer  111 , the active layer  112 , and the second compound semiconductor layer  113  may be each formed of a semiconductor material having a formula represented as AlxInyGa(1-x-y)N (where 0≦x≦1, 0≦y≦1, 0≦x+y≦1), and may be formed by using epitaxial growth using metal organic chemical vapor deposition (MOCVD) equipment. That is, the first compound semiconductor layer  111  may be formed as a GaN or GaN/AlGaN layer doped with a first conductive impurity such as silicon (Si), germanium (Ge), or tin (Sn). The active layer  112  may be formed as an InGaN/GaN layer having a multi-quantum well structure, or one quantum well layer or a double hetero structure. The second compound semiconductor layer  113  may be formed as a GaN or GaN/AlGaN layer doped with a second conductive impurity such as magnesium (Mg), zinc (Zn), or beryllium (Be). 
         [0036]    Next, referring to  FIG. 4 , a portion of the compound semiconductor structure  110  where the first electrode layer  130  (see  FIG. 1 ) is to be formed is etched to a predetermined depth from the second compound semiconductor layer  113  to form the via-hole  11   a  and expose a portion of the first compound semiconductor layer  111 . The via-hole  110   a  may be formed to have a mesa structure or a vertical structure. A plurality of the via-holes  110   a  may be formed to correspond to a plurality of the first electrode layers  130 . Next, a passivation layer  121  is coated by using a well-known deposition method on an entire top surface of the compound semiconductor structure  110 . For example, the passivation layer  121  may be formed by depositing SiO 2  to a thickness of about 6000 Å by using plasma enhanced chemical vapor deposition (PECVD). 
         [0037]    Next, referring to  FIG. 5 , a portion of the first compound semiconductor layer  111  is exposed by etching a portion of the passivation layer  121  which is formed at the bottom of the via-hole  110   a . The etching may be performed by using reactive ion etching (RIE) and a buffered oxide etchant (BOE). Next, the first electrode layer  130  is formed on the exposed portion of the first compound semiconductor layer  111 . For example, the first electrode layer  130  may be formed by depositing an Al/Ti/Pt layer to a thickness of 200 nm/1200 nm/20 nm. In this case, current spreading to the first compound semiconductor layer  111  may be improved by forming a plurality of the first electrode layers  130 . 
         [0038]    Referring to  FIG. 6 , a portion of the second compound semiconductor layer  113  is exposed by etching a portion of the passivation layer  121  other than a portion surrounding the first electrode layer  130 . The etching may be performed by using, for example, RIE and a BOE. Next, the second electrode layer  140  is formed on the exposed portion of the second compound semiconductor layer  113 . In this case, the second electrode layer  140  is formed to be spaced apart from the first electrode layer  130 . The second electrode layer  140  may act as a reflective film formed of a metal having both ohmic characteristics and light reflecting characteristics, or may be formed as layers formed by sequentially stacking metals having ohmic characteristics and light reflecting characteristics. For example, the second electrode layer  140  may be formed by depositing a Ni/Ag/Pt/Ti/Pt layer to a thickness of 0.5 nm/250 nm/50 nm/300 nm/50 nm. 
         [0039]    Next, referring to  FIG. 7 , an insulating material layer  122  is coated to a predetermined thickness on the top surface of the compound semiconductor structure  110 . The insulating material layer  122  is coated on a region including the first electrode layer  130 , the second electrode layer  140 , and the passivation layer  121 . The insulating material layer  122  may be formed by, for example, depositing SiO 2  to a thickness of about 8000 Å by using PECVD. The passivation layer  121  and the insulating material layer  122  may be formed of the same material, and constitute the insulating layer  120  with respect to the first electrode layer  130  and the second electrode layer  140 . 
         [0040]    A portion of the insulating material layer  122  covering a top surface of the first electrode layer  130  is removed, and an Al/Ti/Pt layer for forming the first electrode layer  130  is filled in the removed portion, to integrally form the first electrode layer  130 . Then, the first electrode layer  130  is exposed to the outside of the insulating material layer  122 . Accordingly, while the first electrode layer  130  is exposed to the outside of the insulating material layer  122 , the second electrode layer  140  is blocked from the outside due to the insulating material layer  120 . 
         [0041]    Referring to  FIG. 8 , the conducting adhesive layer  150  is coated on a top surface of the non-conductive substrate  160 , and then the non-conductive substrate  160  is adhered to the first electrode layer  130  and the insulating layer  120  by applying a predetermined heat and pressure. The non-conductive substrate  160  is adhered to the conducting adhesive layer  150  by applying a heat higher than 300° C. and a predetermined pressure to the first electrode layer  130  and the insulating layer  120 . Then, while the first electrode layer  130  contacts the conductive adhesive layer  160 , the second electrode layer  140  is separated from the conductive adhesive layer  160  due to the insulating layer  120 . 
         [0042]    Since a heat higher than 300° C. is applied during adhesion to the non-conductive substrate  160  that acts as a final support layer for the light-emitting device, it is preferable that the non-conductive substrate  160  has a thermal expansion coefficient that is similar to that of the substrate  100 . 
         [0043]    Referring to  FIG. 9 , a portion of the conducting adhesive layer  150  is exposed by etching portions of the insulating layer  120 , the compound semiconductor structure  110 , and the substrate  100  adjacent to the first electrode layer  130 . A portion of the second electrode layer  140  is exposed by etching portions of the compound semiconductor structure  110  and the substrate  100  disposed on a top surface of the second electrode layer  140 . The etching may be performed by using, for example, RIE and a BOE. 
         [0044]    Referring to  FIG. 10 , the insulating film  170  is formed to a predetermined thickness on side surfaces of the second conductive layer  140 , the conducting adhesive layer  150 , and the non-conductive substrate  160 . Accordingly, the side surfaces of the second electrode layer  140 , the conducting adhesive layer  150 , and the non-conductive substrate  160  are surrounded by the insulating film  170 . The insulating film  170  may be formed SiOx or SixNy, or polymer, polyimide, or epoxy-based material. 
         [0045]    Referring to  FIG. 11 , the first electrode connection layer  181  is formed to surround the exposed portion of the top surface of the conducting adhesive layer  150  and the side surface of the non-conductive substrate  160 . The second electrode connection layer  182  is formed to surround the insulating film  170  and the exposed portion of the top surface of the second electrode layer  140 . The first electrode connection layer  181  and the second electrode connection layer  182  may be formed by depositing a metal, such as copper, nickel, or chromium, and the metal may be deposited by using E-beam, sputtering, or plating. In this case, one end of the first electrode connection layer  181  is formed on the top surface of the conducting adhesive layer  150  to be spaced apart by a predetermined interval from the insulating layer  120 . One end of the second electrode connection layer  182  is formed on the top surface of the second electrode layer  140  to be spaced apart by a predetermined interval from the second compound semiconductor layer  113 . This is to have a space for forming the protective layer  190  (see  FIG. 13 ) that is to be formed to surround the compound semiconductor structure  110 . 
         [0046]    Next, referring to  FIG. 12 , the substrate  100  is removed from the compound semiconductor structure  110 . Since the top surface of the compound semiconductor structure  110  is a surface for extracting light, the substrate  100  is removed in order to improve light extraction efficiency. Although not shown, a concave-convex structure may be formed on the top surface of the compound semiconductor structure  110  in order to improve light extraction efficiency. 
         [0047]    Referring to  FIG. 13 , the protective layer  190  is formed to surround the compound semiconductor structure  110 . The protective layer  190  for protecting the compound semiconductor structure  110  from the external environment may be formed of a transparent material through which light is transmitted so as not to disturb light extraction. 
         [0048]    Referring to  FIG. 14 , the conductive adhesive layer  183  is coated on a top surface of the package  200 , and then the package  200  is adhered to the first electrode connection layer  181 , the non-conductive substrate  160 , the insulating film  170 , and the second electrode connection layer  182 . In this case, the first electrode connection layer  181  and the second electrode connection layer  182  are adhered and connected to the conductive adhesive layer  183 . 
         [0049]    Referring to  FIG. 15 , a portion of the non-conductive substrate  160  is exposed by forming the via-hole  210  that passes through the package  200  and the conductive adhesive layer  183 . In this case, the first electrode connection layer  181  and the second electrode connection layer  182  are short-circuited due to the via-hole  210 . The via-hole  180  may be formed by using various methods such as drilling, ultrasonic milling, laser drilling, sand blasting, or dry etching, or a combination of the methods.