Abstract:
A manufacturing method of an epitaxial substrate includes the steps of: forming a sacrificial layer, which has a first micro/nano structure, on a substrate; and forming a buffer layer on the sacrificial layer. The sacrificial layer comprises a plurality of micro/nano particles, and the first micro/nano structure is formed after the plurality of micro/nano particles are removed. An epitaxial substrate and a manufacturing method of a light emitting diode (LED) apparatus are also disclosed.

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). 096137372 filed in Taiwan, Republic of China on Oct. 5, 2007, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The invention relates to an epitaxial substrate and a manufacturing method thereof and, in particular, to a manufacturing method of a light emitting diode apparatus. 
         [0004]    2. Related Art 
         [0005]    A light emitting diode (LED) apparatus is a light emitting element made of semiconductor material. Since the LED apparatus advantageously has small size, low power consumption, no radiation, no mercury, long lifetime, high response speed and high reliability, the application range thereof covers the fields of the information electronic product, the communication electronic product, the consumer electronic product, the vehicle product, the illumination product and the traffic sign with the advancing technology. 
         [0006]    Generally speaking, the LED must have an epitaxy multilayer grown on an epitaxial substrate, wherein an N-type epitaxial layer, an active layer and a P-type epitaxial layer are grown on the epitaxial substrate in sequence. In order to decrease the number of defects generated when the N-type epitaxial layer is directly growing on the flat epitaxial substrate, however, an epitaxial substrate having periodic holes is manufactured to prevent the defects from being formed. 
         [0007]      FIGS. 1A to 1G  show manufacturing processes of a LED apparatus  1 . 
         [0008]    As shown in  FIG. 1A , the LED apparatus  1  is composed of a substrate  11 , a buffer layer  12  and a mask layer  13 . The buffer layer  12  is disposed between the substrate  11  and the mask layer  13 . 
         [0009]    As shown in  FIG. 1B , the mask layer  13  is formed with a plurality of hollow portions H 1  by anode aluminum oxide processing or etching in the prior art. 
         [0010]    As shown in  FIG. 1C , the buffer layer  12  is etched with the mask layer  13  serving as an etching mask so that the buffer layer  12  has hollow portions H 2  corresponding to the hollow portions H 1 . In addition, the mask layer  13  is removed after the buffer layer  12  is etched. 
         [0011]    As shown in  FIG. 1D , an epitaxy multilayer  14  is formed on the buffer layer  12  and the hollow portions H 2 . The epitaxy multilayer  14  includes an N-type epitaxial layer  141 , an active layer  142  and a P-type epitaxial layer  143 . An N-type epitaxial layer  141  is formed on the buffer layer  12  and in the hollow portions H 2 . Next, the active layer  142  is formed on the N-type epitaxial layer  141 , and then the P-type epitaxial layer  143  is formed on the active layer  142 . 
         [0012]    Referring to  FIG. 1E , a thermoconductive adhesive layer  16  is formed on a thermoconductive substrate  15 . Then, as shown in  FIG. 1F , the thermoconductive adhesive layer  16  and the P-type epitaxial layer  143  are combined together. Finally, as shown in  FIG. 1G , the LED apparatus  1  is turned over and the substrate  11  is removed by the laser lift-off technology. 
         [0013]    In the conventional semiconductor manufacturing technology, however, complicated manufacturing steps have to be performed to form the nano-level hollow portions H 1  by etching or electron beam exposure. Thus, the production yield is decreased. In addition, the apparatus cost for the laser lift-off technology is also very high. Therefore, it is an important subject to provide an epitaxial substrate, a manufacturing method of the epitaxial substrate and a manufacturing method of a LED apparatus capable of simplifying semiconductor manufacturing steps. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention is to provide an epitaxial substrate, a manufacturing method of the epitaxial substrate and a manufacturing method of a LED apparatus capable of simplifying semiconductor manufacturing steps. 
         [0015]    To achieve the above, the present invention discloses a manufacturing method of an epitaxial substrate including the steps of: forming a sacrificial layer, which has a first micro/nano structure, on a substrate, and forming a buffer layer on the sacrificial layer. 
         [0016]    In addition, the present invention further discloses a manufacturing method of an epitaxial substrate including the steps of: forming a buffer layer on a substrate; forming a sacrificial layer, which has a first micro/nano structure, on the buffer layer; etching the buffer layer with the sacrificial layer serving as an etching mask so that the buffer layer has a second micro/nano structure corresponding to the first micro/nano structure; and removing the sacrificial layer by etching or calcination. 
         [0017]    To achieve the above, the present invention also discloses an epitaxial substrate including a substrate and a buffer layer. The buffer layer is disposed on the substrate and has a micro/nano structure. 
         [0018]    Moreover, the present invention also discloses a manufacturing method of a light emitting diode (LED) apparatus including the steps of: providing an epitaxial substrate having a micro/nano structure; forming a first semiconductor layer on the micro/nano structure of the epitaxial substrate; forming an active layer on the first semiconductor layer; and forming a second semiconductor layer on the active layer. 
         [0019]    As mentioned above, the epitaxial substrate, the manufacturing method thereof and the manufacturing method of the LED apparatus according to the present invention have the following features. First, the sacrificial layer having the micro/nano structure is disposed on the buffer layer or the substrate. Next, the nano-particles are removed by etching or calcination so that the buffer layer or the substrate has the micro/nano holes. In addition, compared with the prior art, in which the epitaxial substrate is removed by the laser lift-off technology, the epitaxial substrate is removed by etching in the manufacturing method of the LED apparatus of the present invention. Thus, the manufacturing processes can be simplified, and the production yield can be enhanced according to the epitaxial substrate, the manufacturing method thereof and the manufacturing method of the LED apparatus of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0021]      FIGS. 1A to 1G  show manufacturing processes of the conventional LED apparatus; 
           [0022]      FIG. 2  is a flow chart showing a manufacturing method of an epitaxial substrate according to a first embodiment of the present invention; 
           [0023]      FIGS. 3A to 3C  show manufacturing processes of the epitaxial substrate according to the first embodiment of the present invention; 
           [0024]      FIG. 4  is a flow chart showing a manufacturing method of an epitaxial substrate according to a second embodiment of the present invention; 
           [0025]      FIGS. 5A to 5F  show manufacturing processes of the epitaxial substrate according to the second embodiment of the present invention; 
           [0026]      FIG. 6  is a flow chart showing a manufacturing method of an epitaxial substrate according to a third embodiment of the present invention; 
           [0027]      FIGS. 7A to 7F  show manufacturing processes of the epitaxial substrate according to the third embodiment of the present invention; 
           [0028]      FIG. 8  is a flow chart showing a manufacturing method of a LED apparatus according to a preferred embodiment of the present invention; and 
           [0029]      FIGS. 9A to 9E  show manufacturing processes of the LED apparatus according to the preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
         [0031]    Referring to  FIG. 2 , a manufacturing method of an epitaxial substrate according to a first embodiment of the present invention includes steps S 11  to S 13 . Illustrations will be made with reference to  FIGS. 2 and 3A  to  3 C. 
         [0032]    As shown in  FIG. 3A , a sacrificial layer  22  is formed on a substrate  21  in the step S 11 . In this embodiment, the sacrificial layer  22  is formed by mixing metal oxide  221  and a plurality of micro/nano particles  222  with the properly adjusted ratio so that the micro/nano particles  222  are periodically arranged in the metal oxide  221 . 
         [0033]    The material of the micro/nano particle  222  includes metal, dielectric material, organic material or inorganic material. The micro/nano particle  222  may be a nano-ball, a nano-column, a nano-hole, a nano-point, a nano-line or a nano-concave-convex structure. Herein, the micro/nano particle  222  is the nano-ball, and the material of the metal oxide  221  includes aluminum oxide. 
         [0034]    As shown in  FIG. 3B , the micro/nano particle  222  is removed by etching or calcination in the step S 12 . At this time, the sacrificial layer  22  has a first micro/nano structure. As shown in  FIG. 3C , a buffer layer  23  is formed on the sacrificial layer  22  in the step S 13 . In this embodiment, the buffer layer  23  includes aluminum nitride or gallium nitride. 
         [0035]    It is to be noted that the order of the steps can be changed according to the actual requirement of the manufacturing processes. 
         [0036]    As shown in  FIG. 4 , a manufacturing method of an epitaxial substrate according to a second embodiment of the present invention includes steps S 21  to S 25 . Illustrations will be made with reference to  FIGS. 4 and 5A  to  5 E. 
         [0037]    As shown in  FIG. 5A , a sacrificial layer  32  is formed on a substrate  31  in the step S 21 . Herein, the sacrificial layer  32  has a first micro/nano structure. The first micro/nano structure is formed by stacking, sintering, anode aluminum oxide (AAO) processing, nano-imprinting, transfer printing, hot pressing, etching or electron beam writer (E-beam writer) processing. 
         [0038]    In this embodiment, the first micro/nano structure has a plurality of micro/nano particles including at least one nano-ball, nano-column, nano-hole, nano-point, nano-line or nano-concave-convex structure. Herein, the first micro/nano structure is the nano-ball, and the material of the micro/nano particle may include metal, dielectric material, organic material or inorganic material. The micro/nano particles are arranged in a periodic manner, non-periodic manner, continuous manner, non-continuous manner, gap-free manner, gap-containing manner, equally spaced manner or unequally spaced manner. 
         [0039]    As shown in  FIG. 5B , a buffer layer  33  is formed on the sacrificial layer  32  in the step S 22 . Herein, the thickness of the buffer layer  33  is smaller than that of the sacrificial layer  32 , and the buffer layer  33  includes aluminum nitride or gallium nitride. 
         [0040]    As shown in  FIG. 5C , the sacrificial layer  32  is removed by etching or calcination in the step S 23 . Accordingly, the buffer layer  33  has a second micro/nano structure corresponding to the first micro/nano structure. 
         [0041]    As shown in  FIG. 5D , the substrate  31  is etched with the buffer layer  33  serving as an etching mask in the step S 24 . Accordingly, the substrate  31  has a third micro/nano structure corresponding to the second micro/nano structure. As shown in  FIG. 5E , the buffer layer  33  is removed by etching in the step S 25 . 
         [0042]    In addition, the user can select one of the structures in  FIGS. 5C to 5E  as the epitaxial substrate according to the actual requirement, and an epitaxy multilayer (to be described in the following) is formed on the epitaxial substrate. 
         [0043]    It is to be noted that the order of the above-mentioned steps is not particularly limited and can be changed according to the requirement of the manufacturing processes. 
         [0044]    In addition, as shown in  FIG. 5F , what is different from the above-mentioned structures is that a sacrificial layer  32 A having nano-balls arranged side by side is formed on the substrate  31 , and then a buffer layer  33 A is formed on the sacrificial layer  32 A. 
         [0045]    As shown in  FIG. 6 , a manufacturing method of an epitaxial substrate according to a third embodiment of the present invention includes steps S 31  to S 36 . Illustrations will be made with reference to  FIGS. 6 and 7A  to  7 F. 
         [0046]    As shown in  FIG. 7A , a buffer layer  42  is formed on a substrate  41  in the step S 31 . In this embodiment, the material of the buffer layer  42  can be aluminum nitride or gallium nitride. 
         [0047]    As shown in  FIG. 7B , a sacrificial layer  43  is formed on a buffer layer  43  in the step S 32 . In this embodiment, the sacrificial layer  43  has a first micro/nano structure, which is manufactured by stacking, sintering, anode aluminum oxide processing, nano-imprinting, transfer printing, hot pressing, etching or electron beam exposure. 
         [0048]    Herein, the first micro/nano structure has a plurality of micro/nano particles including at least one nano-ball, a nano-column, a nano-hole, a nano-point, a nano-line or a nano-concave-convex structure. In this embodiment, the first micro/nano structure is the nano-ball, and the material of the micro/nano particle includes metal, dielectric material, organic material or inorganic material. 
         [0049]    As shown in  FIG. 7C , the buffer layer  42  is etched with the sacrificial layer  43  serving as an etching mask in the step S 33 . Accordingly, the buffer layer  42  has a second micro/nano structure corresponding to the first micro/nano structure. 
         [0050]    As shown in  FIG. 7D , the sacrificial layer  43  is removed by etching or calcination in the step S 34 . As shown in  FIG. 7E , the substrate  41  is etched with the buffer layer  42  serving as an etching mask in the step S 35  so that the substrate  41  has a third micro/nano structure corresponding to the second micro/nano structure. As shown in  FIG. 7F , the buffer layer  42  is removed by etching in the step S 36 . 
         [0051]    In addition, the user can select one of the structures in  FIGS. 7D to 7F  as the epitaxial substrate according to the actual requirement, and an epitaxy multilayer (to be described in the following) is formed on the epitaxial substrate. 
         [0052]    It is to be noted that the order of the steps can be changed according to the actual requirement of the manufacturing processes. 
         [0053]    As mentioned hereinabove, the manufacturing method of the LED apparatus of the present invention can be performed based on the epitaxial substrate in the above-mentioned embodiment. As shown in  FIG. 8 , the manufacturing method includes steps S 41  to S 46 . Illustrations will be made with reference to  FIGS. 8 and 9A  to  9 F. 
         [0054]    As shown in  FIG. 9A , an epitaxial substrate  61  having a micro/nano structure is provided in the step S 41 . Herein, the epitaxial substrate  61  is the epitaxial substrate of the second embodiment in  FIG. 5B  and includes the substrate  31 , the sacrificial layer  32  and the buffer layer  33 . 
         [0055]    Next, as shown in  FIG. 9B , an epitaxy multilayer  63  is formed on the buffer layer  33  in the step S 42 . The epitaxy multilayer  63  includes a first semiconductor layer  631 , an active layer  632  and a second semiconductor layer  633  in sequence. In this embodiment, the first semiconductor layer  631  is formed on the buffer layer  33 . Next, the first semiconductor layer  631  is formed on the active layer  632 , and then the second semiconductor layer  633  is formed on the active layer  632 . In addition, the first semiconductor layer  631  and the second semiconductor layer  633  can be an N-type epitaxial layer and a P-type epitaxial layer or can be the P-type epitaxial layer and the N-type epitaxial layer, respectively. 
         [0056]    As shown in  FIG. 9C , a thermoconductive adhesive layer (also referred to as a bonding layer)  65  is formed on a thermoconductive substrate  64  in the step S 43 . In this embodiment, the material of the thermoconductive substrate  64  includes silicon, gallium arsenide, gallium phosphide, silicon carbide, boron nitride, aluminum, aluminum nitride, copper or combinations thereof. The material of the thermoconductive adhesive layer  65  can be selected from the group consisting of various metallic or non-metal materials or combinations thereof, such as gold, soldering paste, tin-silver paste or silver paste. 
         [0057]    It is to be noted that the thermoconductive adhesive layer  65  can be formed on the thermoconductive substrate  64 , the second semiconductor layer  633 , or the thermoconductive substrate  64  and the second semiconductor layer  633  simultaneously. 
         [0058]    As shown in  FIG. 9D , the second semiconductor layer  633  is combined with the thermoconductive substrate  64  through the thermoconductive adhesive layer  65  in the step S 44 . Finally, as show in  FIG. 9E , the LED apparatus  6  formed in the step S 44  is turned over in the step S 45  and the epitaxial substrate  61  is removed by etching. 
         [0059]    It is to be noted that the order of the steps can be changed according to the actual requirement of the manufacturing processes. 
         [0060]    Herein, the manufacturing method of the LED apparatus is only described according to the above-mentioned examples, wherein the epitaxial substrate used in the manufacturing processes is, for example but not limited to, any one of the epitaxial substrates according to the first to third embodiments, or other epitaxial substrates manufacturing according to the concept of the present invention. 
         [0061]    In summary, the epitaxial substrate, the manufacturing method thereof and the manufacturing method of the LED apparatus according to the present invention have the following features. First, the sacrificial layer having the micro/nano structure is disposed on the buffer layer or the substrate. Next, the nano-particles are etched by etching or calcination so that the buffer layer or the substrate has the micro/nano holes. In addition, compared with the prior art, in which the epitaxial substrate is removed by the laser lift-off technology, the epitaxial substrate is removed by etching in the manufacturing method of the LED apparatus of the present invention. Thus, the manufacturing processes can be simplified, and the production yield can be enhanced according to the epitaxial substrate, the manufacturing method thereof and the manufacturing method of the LED apparatus of the invention. 
         [0062]    Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.