Abstract:
An island submount used for carrying at least one light-emitting element having at least one electrical contact. The island submount includes a substrate, at least one island structure having a top surface and an inclined surface, and a conductive layer. The island structure is located on the substrate and corresponds to the electrical contact. The conductive layer is formed on the surface of the island structure and at least covers the top surface, so as to be electrically connected with the electrical contact. The island submount is capable of enhancing the light extraction efficiency of the light-emitting element, and avoids the energy loss due to re-absorption when the light emerging from below the light-emitting element is reflected back to the light-emitting element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 0961364445 filed in Taiwan, R.O.C. on Sep. 28, 2007, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a submount, and more particularly to a submount having an island structure used for carrying a light-emitting element. 
         [0004]    2. Related Art 
         [0005]    The light-emitting principle of light-emitting diodes (LEDs) is to form a p-n junction with different doping modes. When electrons and holes are combined, the energy is released in the form of light, and the light is substantially a set of infinite multi-point light sources. LEDs are advantageous in high durability, long service life, light weight, and low power consumption. Besides, LEDs do not contain hazardous substances like mercury. Therefore, the illumination market has a high expectation on LEDs. 
         [0006]    The light-emitting efficiency of LEDs is generally referred to as the external quantum efficiency (EQE) of an element, which is a product of the internal quantum efficiency (IQE) and light extraction efficiency (LEE) of the element. The IQE of an element is actually the electric-optical conversion efficiency of the element, which is mainly relevant to the characteristics of the element, such as the energy band, defects and impurities of the material of the element, as well as the expitaxy composition and structure of the element. The LEE of an element is the number of the photons generated inside the element that can be actually measured outside the element after being absorbed, refracted, and reflected by the element. Thus, factors related to the LEE includes the absorption coefficient and refractive index of the material of the element, the geometrical structure and surface roughness of the element, the refractive index difference between the element and the packaging material, and the type of the element packages, and so on. The product of the above two efficiencies is the light-emitting effect of the entire element, i.e., the EQE of the element. 
         [0007]    Besides the prior art of face-up architecture, the face-down flip-chip type packages are the main trend of the future development, since the face-down flip-chip type packages can significantly improve the heat dissipation and light extraction effect. Currently, the flip-chip architecture may be classified into to two popular types including the thin film LED and the flip-chip LED. The thin film LED is mainly formed by turning over an expitaxy layer plated with a reflective layer to be fixed to a submount by a connection layer, and then stripping the growth substrate and roughening its upper surface. The flip-chip LED has a similar architecture as the above thin film LED. The main difference therebetween is that the flip-chip LED is fixed onto a submount through a plurality of metal balls, and thus a space for emerging light is formed between the expitaxy layer and the submount, so as to reduce the amount of absorption of the light emerging from below the flip-chip LED when being reflected back to the flip-chip LED. 
         [0008]      FIG. 1  is a schematic view of a prior art flip-chip architecture. Referring to  FIG. 1  the prior art of flip-chip architecture uses a metal ball  12  to fix a light-emitting element  11  onto a submount  13 . However, the light emerging from below the light-emitting element  11  may still enter the light-emitting element  11  after being reflected by the surface of the submount  13 , thus resulting in re-absorption and weakening the energy of the output light at last. 
       SUMMARY OF THE INVENTION 
       [0009]    To avoid the absorption of the light from below the light-emitting element to reflect back to the light-emitting element, the present invention provides an island submount which is a substrate having an island structure and a method thereof. 
         [0010]    The island submount of the present invention is used for carrying at least one light-emitting element having at least one electrical contact. The island submount includes a substrate, at least one island structure having a top surface and an inclined surface, and a conductive layer. The at least one island structure is located on the substrate and corresponding to at least one electrical contact of the light-emitting element. The top surface of the island structure is corresponding to the electrical contact of the light-emitting element, and the inclined surface of the island structure is used to reflect and guide the light emerging from below the light-emitting element to be emitted from the side. The conductive layer is formed on the surface of the island structure and at least covers the top surface, and is electrically connected to the electrical contact of the light-emitting element. 
         [0011]    A method for fabricating an island submount, wherein the island submount is used to carry at least one light-emitting element having at least one electrical contact, the fabrication method comprising providing a substrate, forming at least one island structure having a top surface and an inclined surface, wherein the island structure is corresponding to the electrical contact, forming a conductive layer on the substrate, wherein the conductive layer at least covers the top surface, and connecting the conductive layer covered with the top surface to the electrical contact. 
         [0012]    The island submount and the method thereof of the present invention is used to guide the light from below the light-emitting element to be emitted from the side, so as to avoid re-absorption when the light is reflected back to the light-emitting element, thus enhancing the overall LEE of the light-emitting element. 
         [0013]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present invention, and wherein: 
           [0015]      FIG. 1  is a schematic view of a prior art of flip-chip architecture; 
           [0016]      FIG. 2  is a schematic view of a first embodiment of the present invention; 
           [0017]      FIG. 3A  is a schematic view of an inclined surface of an island structure according to the present invention; 
           [0018]      FIG. 3B  is another schematic view of the inclined surface of an island structure according to the present invention; 
           [0019]      FIG. 4  is a schematic view of a second embodiment of the present invention; 
           [0020]      FIG. 5  is a schematic view of a third embodiment of the present invention; 
           [0021]      FIG. 6  is a top view of the third embodiment of the present invention; 
           [0022]      FIG. 7  is a schematic view of a fourth embodiment of the present invention; 
           [0023]      FIG. 8  is a schematic view of a fifth embodiment of the present invention; 
           [0024]      FIG. 9  is a schematic view of a sixth embodiment of the present invention; 
           [0025]      FIG. 10  is a schematic view of a seventh embodiment of the present invention; 
           [0026]      FIG. 11  is a schematic view of an eighth embodiment of the present invention; 
           [0027]      FIG. 12  is a schematic view of a ninth embodiment of the present invention; 
           [0028]      FIG. 13  is a schematic view of a tenth embodiment of the present invention; 
           [0029]      FIG. 14  is a flow chart of fabricating processes of the first embodiment of the present invention; 
           [0030]      FIG. 15  is a flow chart of fabricating processes of the second embodiment of the present invention; 
           [0031]      FIG. 16  is a flow chart of fabricating processes of the third embodiment of the present invention; 
           [0032]      FIG. 17  is a flow chart of fabricating processes of the fifth embodiment of the present invention; 
           [0033]      FIG. 18  is a flow chart of fabricating processes of the sixth embodiment of the present invention; 
           [0034]      FIG. 19  is a flow chart of fabricating processes of the seventh embodiment of the present invention; 
           [0035]      FIG. 20  is a flow chart of fabricating processes of the eighth embodiment of the present invention; 
           [0036]      FIG. 21  is a flow chart of fabricating processes of the ninth embodiment of the present invention; and 
           [0037]      FIG. 22  is a flow chart of fabricating processes of the tenth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    The features and practice of the present invention will be illustrated in detail below with the accompanying drawings. 
         [0039]    Referring to  FIG. 2 , a schematic view of a first embodiment of the present invention is shown. An island submount  100  is provided for carrying a light-emitting element  21  having an electrical contact  22 . The island submount  100  includes a substrate  23 , an island structure  24 , and a conductive layer  25 . 
         [0040]    The substrate  23  is made of a thermal conductive material, such as semiconductor, ceramic, or metal material. 
         [0041]    The island structure  24  is formed on the substrate  23  and corresponding to the electrical contact  22  of the light-emitting element  21 . The island structure  24  has a top surface  26  and an inclined surface  27 . 
         [0042]    The conductive layer  25  is covered on the top surface  26  of the island structure  24 , for electrically connecting to the electrical contact  22  of the light-emitting element  21  corresponding to the island structure  24 . The conductive layer  25  is electrically connected to the electrical contact  22  of the light-emitting element  21  through a connection layer  28 . The connection layer  28  is made of an electrical conductive material. The conductive layer  25  is made of an electrical conductive material. 
         [0043]    The island submount  100  of this embodiment further includes a reflective layer  29 . The reflective layer  29  not only covers the inclined surface  27  of the island structure  24 , but also covers the surface of the substrate  23 , so as to appropriately reflect more lights. The reflective layer  29  is used to reflect and guide the light emerging from below the light-emitting element  21  carried by the island submount  100  to be emitted from the side. The reflective layer  29  is made of a reflective material. 
         [0044]    The inclined surface  27  is a flat surface or a curved surface. Referring to  FIGS. 3A and 3B ,  FIG. 3A  is a schematic view of the inclined surface of the island structure according to the present invention, in which the inclined surface of the island structure is a concave curved surface  27   a .  FIG. 3B  is a schematic view of the inclined surface of the island structure according to the present invention, in which the inclined surface of the island structure is a convex curved surface  27   b.    
         [0045]      FIG. 4  is a schematic view of a second embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the first embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the conductive layer  25  is made of an electrically conductive and reflective material, such that the conductive layer  25  not only has excellent electrical conductivity, but also can effectively reflect the light. The conductive layer  25  is formed on the top surface  26  and the inclined surface  27  of the island structure  24 , thus simplifying the fabricating processes of the reflective layer  29 . 
         [0046]    Referring to  FIG. 5 , a schematic view of a third embodiment of the present invention is shown. An island submount  200  is provided for carrying a light-emitting element  121  having two electrical contacts  122   a ,  122   b  of opposite electrical properties. The island submount  200  includes a substrate  123 , two island structures  124   a ,  124   b , and two conductive layers  125   a ,  125   b.    
         [0047]    The substrate  123  is made of a thermal conductive material, such as semiconductor, ceramic, metal material, glass fiber, or bakelite. 
         [0048]    The two island structures  124   a ,  124   b  are formed on the substrate  123 . Each of the island structures is corresponding to an electrical contact of the light-emitting element. That is, the two island structures  124   a ,  124   b  are respectively corresponding to the two electrical contacts  122   a ,  122   b  of opposite electrical properties of the light-emitting element  121 . The two island structures  124   a ,  124   b  respective have top surfaces  126 ,  128  and inclined surfaces  127 ,  129 . 
         [0049]    The two conductive layers  125   a ,  125   b  are made of an electrically conductive and reflective material. The two conductive layers  125   a ,  125   b  are respectively covered on the top surfaces  126 ,  128  and the inclined surfaces  127 ,  129  of the two island structures  124   a ,  124   b.  The two conductive layers  125   a ,  125   b  respectively covered on the top surfaces  126 ,  128  are electrically connected to the two electrical contacts  122   a ,  122   b  of opposite electrical properties. The two conductive layers  125   a ,  125   b  are electrically connected to the two electrical contacts  122   a ,  122   b  of opposite electrical properties through connection layers  130   a ,  130   b . The connection layers  130   a ,  130   b  are made of an electrical conductive material. The two conductive layers  125   a ,  125   b  are disconnected between the two island structures  124   a ,  124   b.    
         [0050]    The third embodiment of the present invention is disclosed above and is not intended to limit the number of the elements, such as the light-emitting element, the electrical contact, the conductive layer, and the island structure of the present invention. The number of the aforementioned elements may be one or more. Referring to  FIG. 6 , a top view of the third embodiment of the present invention is shown. 
         [0051]    Referring to  FIG. 7 , a schematic top view of a fourth embodiment of the present invention is shown. The island submount  300  of this embodiment is constituted by a plurality of island submounts  200  arranged in an array. 
         [0052]    Referring to  FIG. 8 , a schematic view of a fifth embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the first embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the island submount  100  further includes a transparent protection layer  30  or a light-transmissive protection layer. The transparent protection layer  30  or the light-transmissive protection layer is covered on the reflective layer  29  corresponding to the inclined surface  27 , for protecting the reflective layer  29  from being damaged by external forces. The transparent protection layer  30  or the light-transmissive protection layer is made of a transparent or light-transmissive insulating material that allows the light emerging from the light-emitting element  21  to pass through. 
         [0053]    Referring to  FIG. 9 , a schematic view of a sixth embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the second embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the island submount  100  further includes a transparent protection layer  31  or a light-transmissive protection layer. The transparent protection layer  31  or the light-transmissive protection layer is covered on the reflective layer  25  corresponding to the inclined surface  27 , for protecting the reflective layer  25  from being damaged by external forces. The transparent protection layer  31  or the light-transmissive protection layer is made of a transparent or light-transmissive insulating material that allows the light emerging from the light-emitting element  21  to pass through. 
         [0054]    Referring to  FIG. 10 , a schematic view of a seventh embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the fifth embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the conductive layer  25  of the island submount  100  is further covered on the inclined surface  27 . 
         [0055]    Referring to  FIG. 11 , a schematic view of an eighth embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the seventh embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the island submount  100  further includes an insulating layer  32  formed between the conductive layer  25  and the substrate  23 . 
         [0056]    Referring to  FIG. 12 , a schematic view of a ninth embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the eighth embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the transparent protection layer  30  or the light-transmissive protection layer of the island submount  100  is covered on the reflective layer  29  corresponding to the inclined surface  27 , and is at the same level of a light output plane  33  below the light-emitting element  21  carried by the island submount  100  of the present invention, for carrying the light-emitting element  21 . 
         [0057]    Referring to  FIG. 13 , a schematic view of a tenth embodiment of the present invention is shown. The structure of the island submount of this embodiment has been disclosed in the eighth embodiment, and the same parts can refer to the above description and will not be described herein again. This embodiment is characterized in that the submount having the island structure  24  further includes a channel  35  penetrating from the top surface  26  of to the other side of the substrate  23  having the island structure  24 . Besides, the channel  35  has an electrical conductive substance  37  on the inner side  36  thereof, and the electrical conductive substance  37  is electrically connected to the conductive layer  25 , so as to electrically connect the electrical contact  22  to the other side of the substrate  23  having the island structure  24 . 
         [0058]    Referring to  FIG. 14 , a flow chart of fabricating processes of the first embodiment of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  41 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  42 ). A conductive layer is formed on the substrate, and the conductive layer covers the top surface of the island structure (Step  43 ). A reflective layer is formed on the substrate and covers the inclined surface (Step  44 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  45 ). 
         [0059]    Referring to  FIG. 15 , a flow chart of fabricating processes of the second embodiment of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  51 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  52 ). A conductive layer is formed on the substrate and covers the top surface and the inclined surface of the island structure (Step  53 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  54 ). 
         [0060]    Referring to  FIG. 16 , a flow chart of fabricating processes of the third embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having two electrical contacts of opposite electrical properties. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  61 ). Two island structures having a top surface and an inclined surface are formed on the substrate and corresponding to the two contacts of opposite electrical properties (Step  62 ). A conductive layer is formed on the substrate and covers the top surface and the inclined surface of the two island structures (Step  63 ). The connection portion of the conductive layer between the two island structures is removed (Step  64 ). The conductive layer covered on the top surface of the two island structures is connected to the two contacts of opposite electrical properties (Step  65 ). 
         [0061]    Referring to  FIG. 17 , a flow chart of fabricating processes of the fifth embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  71 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  72 ). A conductive layer is formed on the substrate and covers the top surface of the island structure (Step  73 ). A reflective layer is formed on the substrate and covers the inclined surface (Step  74 ). A transparent protection layer or a light-transmissive protection layer is formed on the substrate and covers the reflective layer corresponding to the inclined surface (Step  75 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  76 ). 
         [0062]    Referring to  FIG. 18 , a flow chart of fabricating processes of the sixth embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  81 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  82 ). A conductive layer is formed on the substrate and covers the top surface and the inclined surface of the island structure (Step  83 ). A transparent protection layer or a light-transmissive protection layer is formed on the substrate and covers the conductive layer corresponding to the inclined surface (Step  84 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  85 ). 
         [0063]    Referring to  FIG. 19 , a flow chart of fabricating processes of the seventh embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  91 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  92 ). A conductive layer is formed on the substrate and covers the top surface and the inclined surface of the island structure (Step  93 ). A reflective layer is formed on the substrate and covers the conductive layer corresponding to the inclined surface (Step  94 ). A transparent protection layer or a light-transmissive protection layer is formed on the substrate and covers the reflective layer corresponding to the inclined surface (Step  95 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  96 ). 
         [0064]    Referring to  FIG. 20 , a flow chart of fabricating processes of the eighth embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  101 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  102 ). An insulating layer is formed on the substrate and covers the top surface and the inclined surface of the island structure (Step  103 ). A conductive layer is formed on the substrate and covers on the insulating layer (Step  104 ). A reflective layer is formed on the substrate and covers on the conductive layer corresponding to the inclined surface (Step  105 ). A transparent protection layer or a light-transmissive protection layer is formed on the substrate and covers the reflective layer corresponding to the inclined surface (Step  106 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  107 ). 
         [0065]    Referring to  FIG. 21 , a flow chart of fabricating processes of the ninth embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  111 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  112 ). An insulating layer is formed on the substrate and covers the top surface and the inclined surface of the island structure (Step  113 ). A conductive layer is formed on the substrate and covers on the insulating layer (Step  114 ). A reflective layer is formed on the substrate and covers the conductive layer corresponding to the inclined surface (Step  115 ). A transparent protection layer or a light-transmissive protection layer is formed on the substrate and covers the reflective layer corresponding to the inclined surface, and is at the same level of a light output plane below the light-emitting element (Step  116 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  117 ). 
         [0066]    Referring to  FIG. 22 , a flow chart of fabricating processes of the tenth embodiment of the island submount of the present invention is shown. A method for fabricating an island submount is provided, in which the island submount is used for carrying a light-emitting element having an electrical contact. The fabricating method includes the following steps. First, a thermal conductive substrate is provided (Step  121 ). An island structure having a top surface and an inclined surface is formed on the substrate and corresponding to the electrical contact (Step  122 ). A channel penetrating from the top surface of the island structure to the other side of the substrate having the island structure is formed (Step  123 ). A conductive layer is formed on the substrate and covers the top surface and the inclined surface of the island structure (Step  124 ). The channel has an electrical conductive substance on the inner side thereof, and the electrical conductive substance is connected to the conductive layer, so as to electrically connect the electrical contact to the other side of the substrate having the island structure (Step  125 ). The conductive layer covered on the top surface is connected to the electrical contact (Step  126 ). 
         [0067]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.