Abstract:
A light-emitting device and method for manufacturing the same are described. A method for manufacturing a light-emitting device comprising the steps of: providing a substrate; forming a light-emitting structure on the substrate, wherein the light-emitting structure comprising a plurality of chip areas and a plurality of street areas; forming a conductive structure between the substrate and the light-emitting structure; removing a part of the light-emitting structure in the street areas to expose a sidewall in the chip areas; forming a first passivation layer on the light-emitting structure in the chip areas; and forming a second passivation layer in the street areas, the sidewalls of the light-emitting structure, and the sidewalls of the first passivation layer.

Description:
TECHNICAL FIELD 
       [0001]    The present application relates to a light-emitting device and a method for manufacturing the same, and more particularly to a III-V compound semiconductor light-emitting device with a passivation layer. 
       BACKGROUND 
       [0002]    The light radiation theory of light-emitting device is to generate light from the energy released by the electrons moving between the n-type semiconductor layer and the p-type semiconductor layer. Because the light radiation theory of light-emitting device is different from the incandescent light which heats the filament, the light-emitting device is called a “cold” light source. 
         [0003]    Moreover, the light-emitting device is more sustainable, long life-time, light and handy, and less power consumption, therefore it is considered as a new light source for the illumination market. The light-emitting device applies to various applications like the traffic signal, backlight module, street light and medical instruments, and is gradually replacing the traditional lighting sources. 
         [0004]    A vertical light-emitting device fails easily due to a high reverse leakage current. There are several reasons contributing to a high reverse leakage current in the light-emitting device, for example, the metal migration from the conductive structure to the top of the light-emitting device, and the metal impurity attached to the sidewall of the light-emitting structure. 
       SUMMARY 
       [0005]    The present application provides a method for manufacturing a light-emitting device to avoid the light-emitting device is failed due to a high reverse leakage current. 
         [0006]    The present application provides a method for manufacturing a light-emitting device comprising the steps of: providing a substrate; forming a light-emitting structure on the substrate, wherein the light-emitting structure comprising a plurality of chip areas and a plurality of street areas; forming a conductive structure between the substrate and the light-emitting structure; removing a part of the light-emitting structure in the street areas to expose a sidewall in the chip areas; and forming a passivation layer on the light-emitting structure in the chip areas and on the conductive structure in the street areas. 
         [0007]    The present application provides a method for manufacturing a light-emitting device comprising the steps of: providing a substrate; forming a light-emitting structure on the substrate, wherein the light-emitting structure comprising a plurality of chip areas and a plurality of street areas; forming a conductive structure between the substrate and the light-emitting structure; removing a part of the light-emitting structure in the street areas to expose a sidewall in the chip areas; forming a first passivation layer on the light-emitting structure in the chip areas; and forming a second passivation layer on the conductive structure in the street areas, the sidewalls of the light-emitting structure, and the sidewalls of the first passivation layer. 
         [0008]    According to the aforementioned aspects, the present application provides a method for manufacturing a light-emitting device comprising the steps of: dry etching a portion of the light-emitting structure in the street areas; and wet etching the remained portion of the light-emitting structure in the street areas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The foregoing aspects and many of the attendant advantages of this application are more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0010]      FIG. 1  through  FIG. 14  are schematic flow diagrams showing the process for manufacturing a light-emitting device  1  in accordance with a first embodiment of the present application; and 
           [0011]      FIG. 15  through  FIG. 28  are schematic flow diagrams showing the process for manufacturing a light-emitting device  2  in accordance with a second embodiment of the present application. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    The present application discloses a light-emitting device and a method for manufacturing the same. In order to make the illustration of the present application more explicit, the following description is stated with reference to  FIG. 1  through  FIG. 28 . 
         [0013]      FIG. 1  through  FIG. 14  are schematic flow diagrams showing the process for manufacturing a light-emitting device  1  in accordance with a first embodiment of the present application. As  FIG. 1  shows, a growth substrate  11  is provided for the epitaxial growth of epitaxial materials formed thereon, wherein a material of the growth substrate  11  may be Sapphire. A light-emitting structure  101  is grown on the growth substrate  11  by, for example, metal organic chemical vapor deposition (MOCVD) method, liquid phase deposition (LPD) method, or molecular beam epitaxy (MBE) method. In the embodiment, the light-emitting structure  101  comprises a first conductivity type group III-V compound semiconductor layer  12 , an active layer  13 , and a second conductivity type group III-V compound semiconductor layer  14  stacked on the growth substrate  11 . For example, the first conductivity type group III-V compound semiconductor layer is n-type AlInGaN series material, the active layer is AlInGaN series material, and the second conductivity type group III-V compound semiconductor layer is p-type AlInGaN series material. 
         [0014]    As  FIG. 2  shows, a reflective layer  15  is deposited on the partial region of the second conductivity type group III-V compound semiconductor layer  14  of the light-emitting structure  101 . Next, a conductive region  16  is deposited on the reflective layer  15  and on other partial region of the second conductivity type group III-V compound semiconductor layer  14  that is not covered by the reflective layer  15 . Next, a conductive substrate  21  and a connecting region  22  formed thereon are provided as shown in  FIG. 3 . The conductive region  16  is connected with the conductive substrate  21  by the connecting region  22  as  FIG. 4  shows. There are chip areas A and street areas B in the structure as shown in  FIG. 4 . The street areas B are used for sequent chip dicing process. The conductive region  16  facilitates the electrical conduction between the light-emitting structure  101  and the conductive substrate  21 , and can optionally reflect the light emitted from the light-emitting structure  101  so the reflective layer  15  can be omitted. The connecting region  22  connects the conductive region  16  and the conductive substrate  21 , and forms a conductive structure  17  with the conductive region  16 . Next, the growth substrate  11  is removed by laser irradiation, lapping, or dry etching with inductively coupled plasma etching, as shown in  FIG. 5   
         [0015]    A mask layer  23  is formed on the light-emitting structure  101 , as shown in  FIG. 6 . A photoresist layer  24  is formed on the mask layer  23  in the chip areas A, as shown in  FIG. 7 . The mask layer  23  and a portion of the first conductivity type semiconductor layer  12  in the street areas B are dry etched by inductively coupled plasma etching, as shown in  FIG. 8 . And a remained portion of the first conductivity type semiconductor layer  12 , active layer  13 , and the second conductivity type semiconductor layer  14  in the street areas B are wet etched by using a solution containing H 3 PO 4 , as shown in  FIG. 9 . After the wet etching, a tilt sidewall  20  of the light-emitting structure  101  is formed in the chip areas A wherein a tilt angle θ of the tilt sidewall  20  between the conductive substrate  21  and the light-emitting structure  101  is around 40°-80°. Next, the photoresist layer  24  and the mask layer  23  on the light-emitting structure  101  in the chip areas A are removed, as shown in  FIG. 10 . A passivation layer  25  is then formed on the light-emitting structure  101  in the chip areas A and on the conductive structure  17  in the street areas B, as shown in  FIG. 11 . 
         [0016]    In  FIG. 12 , a through-hole  26  is formed through the passivation layer  25  to expose part of the first conductivity type semiconductor layer  12  in the chip areas A. Next, as  FIG. 13  shows, an electrode  27  is formed by filling a metal material in the through-hole  26  and protrudes the through-hole  26 . A plurality of light-emitting devices is formed by dicing along cutting lines C in the street areas B, as shown in  FIG. 13 . Now, the fabrication of a light-emitting device  1  is substantially completed as shown in  FIG. 14 . 
         [0017]      FIG. 15  through  FIG. 28  are schematic flow diagrams showing the process for manufacturing a light-emitting device  2  in accordance with a second embodiment of the present application. As  FIG. 15  shows, a growth substrate  11  is provided for the epitaxial growth of epitaxial materials formed thereon, wherein a material of the growth substrate  11  may be Sapphire. A light-emitting structure  101  is grown on the growth substrate  11  by, for example, metal organic chemical vapor deposition (MOCVD) method, liquid phase deposition (LPD) method, or molecular beam epitaxy (MBE) method. In the embodiment, the light-emitting structure  101  comprises a first conductivity type group III-V compound semiconductor layer  12 , an active layer  13 , and a second conductivity type group III-V compound semiconductor layer  14  stacked on the growth substrate  11 . For example, the first conductivity type group III-V compound semiconductor layer is n-type AlInGaN series material, the active layer is AlInGaN series material, and the second conductivity type group III-V compound semiconductor layer is p-type AlInGaN series material. 
         [0018]    As  FIG. 16  shows, a reflective layer  15  is deposited on the partial region of the second conductivity type group III-V compound semiconductor layer  14  of the light-emitting structure  101 . Next, a conductive region  16  is deposited on the reflective layer  15  and on other partial region of the second conductivity type group III-V compound semiconductor layer  14  that is not covered by the reflective layer  15 . Next, a conductive substrate  21  and a connecting region  22  formed thereon are provided as shown in  FIG. 17 . The conductive region  16  is connected with the conductive substrate  21  by the connecting region  22  as  FIG. 18  shows. There are chip areas A and street areas B in the structure as shown in  FIG. 18 . The street areas B are used for sequent chip dicing process. The conductive region  16  facilitates the electrical conduction between the light-emitting structure  101  and the conductive substrate  21 , and can optionally reflect the light emitted from the light-emitting structure  101  so the reflective layer  15  can be omitted. The connecting region  22  connects the conductive region  16  and the conductive substrate  21 , and forms a conductive structure  17  with the conductive region  16 . The growth substrate  11  is removed by laser irradiation, lapping, or dry etching with inductively coupled plasma etching, as shown in  FIG. 19 . 
         [0019]    A first passivation layer  25   a  is formed on the light-emitting structure  101 , as shown in  FIG. 20 . A photoresist layer  24  is formed on the first passivation layer  25   a  in the chip areas A, as shown in  FIG. 21 . The first passivation layer  25   a  and a portion of the first conductivity type semiconductor layer  12  on the street areas B are dry etched by inductively coupled plasma etching, as shown in  FIG. 22 . And a remained portion of the first conductivity type semiconductor layer  12 , active layer  12 , and the second conductivity type semiconductor layer  14  in the street areas B are wet etched by using a solution containing H 3 PO 4 , as shown in  FIG. 23 . After the wet etching, a tilt sidewall  20  of the light-emitting structure  101  is formed in the chip areas A wherein a tilt angle θ of the tilt sidewall  20  between the conductive substrate  21  and the light-emitting structure  101  is around 40°-80°. A second passivation layer  25   b  is formed on the photoresist layer  24  in the chip areas A and on the conductive structure  17  in the street areas B, as shown in  FIG. 24 . The second passivation layer  25   b  and the photoresist layer  24  in the chip areas A are removed and the first passivation layer  25   a  is exposed, as shown in  FIG. 25 . 
         [0020]    In  FIG. 26 , a through-hole  26  is formed through the first passivation layer  25   a  to expose part of the first conductivity type semiconductor layer  12  in the chip areas A. Next, as  FIG. 27  shows, an electrode  27  is formed by filling a metal material in the through-hole  26  and protrudes the through-hole  26 . A plurality of light-emitting devices is formed by dicing along cutting lines C in the street areas B, as shown in  FIG. 27 . Now, the fabrication of a light-emitting device  2  is substantially completed as shown in  FIG. 28 . 
         [0021]    The conductive region  16  can be a single-layer structure or multiple layers structure. The material of the conductive region  16  may be metals or metal alloys. The material of the connecting region  22  may be Al, Au, Pt, Zn, Ag, Ni, Ge, In, Sn, Ti, Pb, Cu, Pd, or alloys of the aforementioned metals. In another embodiment, the material of the connecting region  22  may be silver glue, spontaneous conductive polymer, polymer materials mixed with conductive materials, or anisotropic conductive film (ACF). The material of the mask layer  23 , the passivation layer  25 , the first passivation layer  25   a,  and the second passivation layer  25   b  comprises dielectric material, and it may be SiO 2 , Al 2 O 3 , Si 3 N 4 , ZrO 2 , and TiO 2 . In another embodiment, the refraction index of the passivation layer  25 , the first passivation layer  25   a,  and the second passivation layer  25   b  is different from the light-emitting structure  101 . The passivation layer  25 , the first passivation layer  25   a,  and the second passivation layer  25   b  can be a single-layer structure or multiple layers structure. In another embodiment, the passivation layer  25 , the first passivation layer  25   a,  and the second passivation layer  25   b  comprises a DBR structure. The material of the electrode  27  comprises metal material, and it can be Cr, Ti, Ni, Pt, Cu, Au, Al, W, Sn, or Ag. The material of the conductive substrate  21  can be germanium (Ge), copper (Cu), aluminum (Al), molybdenum (Mo), tungsten copper (CuW), silicon aluminum (SiAl), gallium arsenide (GaAs), indium phosphide (InP), silicon carbide (SiC), silicon (Si), gallium nitride (GaN), aluminum nitride (AlN) or diamond-like carbon (DLC). 
         [0022]    In the above embodiments of this application, a first passivation layer  25   a  is formed by one step lithography process on the top of the light-emitting structure  101 , therein it can avoid the failure of the light-emitting device due to a high reverse leakage current, and can avoid metal impurity attached to the sidewall of the light-emitting structure  101  in the chip areas A. Using a dry etching process and a wet etching process to etch the mask layer  23 , the first passivation layer  25   a,  and the light-emitting structure  101  in the street areas B. After the wet etching, a tilt sidewall  20  of the light-emitting structure is formed in the chip areas and can decrease the critical angle of total reflection in the light-emitting structure, so the light extraction of the light-emitting device is increased. 
         [0023]    In accordance with the embodiments in the application, the first conductivity type group III-V compound semiconductor layer  12  and the second conductivity type group III-V compound semiconductor layer  14  are two single-layer structures or two multiple layers structure (“multiple layers” means two or more than two layers) having different electrical properties, polarities, dopants for providing electrons or holes respectively. If the first conductivity type group III-V compound semiconductor layer  12  and the second conductivity type group III-V compound semiconductor layer  14  are composed of the semiconductor materials, the conductivity type can be any two of p-type, n-type, and i-type. The active layer  13  disposed between the first conductivity type group III-V compound semiconductor layer  12  and the second conductivity type group III-V compound semiconductor layer  14  is a region where the light energy and the electrical energy could transfer or could be induced to transfer. 
         [0024]    In another embodiment of this application, the light emission spectrum of the light-emitting device  1  after transferring can be adjusted by changing the physical or chemical arrangement of one layer or more layers in the active layer. The material of the active layer  13  can be AlGaInP or AlGaInN. The structure of the active layer  13  can be a single heterostructure (SH), a double heterostructure (DH), a double-side double heterostructure (DDH), or a multi-quantum well (MQW) structure. Besides, the wavelength of the emitted light could also be adjusted by changing the number of the pairs of the quantum well in a MQW structure. 
         [0025]    In one embodiment of this application, a buffer layer (not shown) could be optionally formed between the growth substrate  11  and the first conductivity type group III-V compound semiconductor layer  12 . The buffer layer between two material systems can be used as a buffer system. For the structure of the light-emitting device, the buffer layer is used to reduce the lattice mismatch between two material systems. On the other hand, the buffer layer could also be a single layer, multiple layers, or a structure to combine two materials or two separated structures where the material of the buffer layer can be organic, inorganic, metal, semiconductor, and so on, and the function of the buffer layer can be as a reflection layer, a heat conduction layer, an electrical conduction layer, an ohmic contact layer, an anti-deformation layer, a stress release layer, a stress adjustment layer, a bonding layer, a wavelength converting layer, a mechanical fixing structure, and so on. The material of the buffer layer can be MN, GaN, or other suitable materials. The fabricating method of the buffer layer can be sputter or atomic layer deposition (ALD). 
         [0026]    A contact layer (not shown) can also be optionally formed on the second conductivity type group III-V compound semiconductor layer  14 . The contact layer is disposed on the side of the second conductivity type group III-V compound semiconductor layer  14  away from the active layer  13 . Specifically speaking, the contact layer could be an optical layer, an electrical layer, or the combination of the two. An optical layer can change the electromagnetic radiation or the light from or entering the active layer  13 . The term “change” here means to change at least one optical property of the electromagnetic radiation or the light. The abovementioned property includes but is not limited to frequency, wavelength, intensity, flux, efficiency, color temperature, rendering index, light field, and angle of view. An electrical layer can change or be induced to change the value, density, or distribution of at least one of the voltage, resistance, current, or capacitance between any pair of the opposite sides of the contact layer. The composition material of the contact layer includes at least one of oxide, conductive oxide, transparent oxide, oxide with 50% or higher transmittance, metal, relatively transparent metal, metal with 50% or higher transmittance, organic material, inorganic material, fluorescent material, phosphorescent material, ceramic, semiconductor, doped semiconductor, and undoped semiconductor. In certain applications, the material of the contact layer is at least one of indium tin oxide (ITO), cadmium tin oxide (CTO), antimony tin oxide, indium zinc oxide, zinc aluminum oxide, and zinc tin oxide. If the material is relatively transparent metal, the thickness is about 0.005 mm-0.6 mm. 
         [0027]    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 application without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present application covers modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents. 
         [0028]    Although the drawings and the illustrations above are corresponding to the specific embodiments individually, the element, the practicing method, the designing principle, and the technical theory can be referred, exchanged, incorporated, collocated, coordinated except they are conflicted, incompatible, or hard to be put into practice together. 
         [0029]    Although the present application has been explained above, it is not the limitation of the range, the sequence in practice, the material in practice, or the method in practice. Any modification or decoration for present application is not detached from the spirit and the range of such.