Abstract:
A mold having a sub-micro, or even nano, structure is fabricated. The mold is a porous mold. With the mold, a sub-micro pattern is easily imprinted on a large surface of a substrate or a LED. No expansive equipment is necessary. The fabricating process is fast and cheap; and thus meets producer&#39;s needs.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to fabricating a mold more particularly relates to obtaining a porous aluminum oxide (AlO 2 ) mold for mass-imprinting a sub-micro structure on a light emitting diode (LED), a laser diode or a substrate with a fast speed and a cheap cost. 
       DESCRIPTION OF THE RELATED ARTS 
       [0002]    A nano pattern imprinted on a semiconductor is mainly done through electron beam lithography. This technology has a disadvantage of the slow speed that does not meet user&#39;s requirements. There is still another method for imprinting nano patterns, called a laser interferometry lithography. Its disadvantage is that pattern is hard to be imprinted evenly on a large surface. Besides, producers usually uses masks on imprinting nano pattern and thus cost is high. Hence, the prior arts do not fulfill users&#39; requests on actual use. 
       SUMMARY OF THE INVENTION 
       [0003]    The main purpose of the present invention is to fabricate a porous AlO 2  mold with pore size, pore space in between, and film thickness all controlled through process parameters. 
         [0004]    Another purpose of the present invention is to quickly and cheaply mass-imprint a sub-micro structure on a large surface of a LED, a laser diode or a substrate to meet needs of producers. 
         [0005]    To achieve the above purpose, the present invention is a method of fabricating a porous AlO 2  mold having a sub-micro structure, comprising steps of (a 1 ) obtaining an aluminum mold from an aluminum foil through annealing; (a 2 ) cleansing the aluminum mold and burnishing a surface of the aluminum mold by an electrochemical method (a 3 ) anodizing the aluminum mold and cleansing the aluminum mold with a deionized water; (a 4 ) fast-drying the aluminum mold with ethanol and forming an oxidized layer; and, (a 5 ) after being cleansed with a deionized water, removing the oxidized layer by using a phosphoric acid to obtain a porous AlO2 mold having a sub-micro structure after drying the aluminum mold in the air, where the porous AlO 2  mold has imprint methods to imprint a sub-micro structure on a LED, a substrate, etc. and to further fabricate a p-side up LED or an n-side up LED. Accordingly, a novel method of fabricating a porous AlO 2  mold having a sub-micro structure is obtained. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0006]    The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
           [0007]      FIG. 1  is the sectional view showing the porous AlO 2  mold according to the preferred embodiment of the present invention 
           [0008]      FIG. 2A  to  FIG. 2E  are the views showing the first imprint method; 
           [0009]      FIG. 3A  to  FIG. 3G  are the views showing the second imprint method; 
           [0010]      FIG. 4A  to  FIG. 4G  are the views showing the third imprint method; 
           [0011]      FIG. 5A  to  FIG. 5D  are the views showing fabricating the p-side up LED; and 
           [0012]      FIG. 6A  to  FIG. 6E  are the views showing fabricating the p-side up LED; 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
         [0014]    Please refer to  FIG. 1 , which is a sectional view showing a porous AlO 2  mold according to a preferred embodiment of the present invention. As shown in the figure, the present invention is a method of fabricating a porous aluminum oxide (AlO 2 ) mold having a sub-micro structure, comprising the following steps: 
         [0015]    (a 1 ) An aluminum foil is obtained to be processed through an annealing to obtain an aluminum mold. Through the annealing, pores  11  in the aluminum mold is arranged orderly and have even diameters. 
         [0016]    (a 2 ) After cleansing the aluminum mold, the aluminum mold is burnished on a surface by an electrochemical method, where impurities on the surface is removed and a smooth surface is obtained. 
         [0017]    (a 3 ) An anodizing is processed to the aluminum mold and then the aluminum mold is cleansed with a deionized water, where the aluminum mold can be processed with the anodizing twice; the anodizing uses a power supplier whose anode is connected with the aluminum mold and whose cathode is connected with a graphite rod; the aluminum mold is immersed in an electrolyte of a phosphoric acid, an oxalic acid or a sulfuric acid; and the electrolyte is stirred with a magnetic stirbar. 
         [0018]    (a 4 ) An ethanol is used to fast dry the aluminum mold and an ivory-white film of an oxidized layer is formed on a surface. 
         [0019]    (a 5 ) A phosphoric acid is used to remove the oxidized layer and then is washed with a deionized water to be dried in the air to obtain a porous AlO 2  mold  1 , where the porous AlO 2  mold  1  is kept being immersed in the phosphoric acid to obtain bigger pores having even diameters, 
         [0020]    Pores obtained after anodizing are usually distributed into a difform pattern. A structure thus formed on a surface of a LED obtains a difform pattern to increase roughness which is in favor of light extraction. On the contrary, if a uniform pattern is preferred, the porous AlO 2  mold needs to be pre-processed or to be anodized again. Moreover, the pore-sizes and spaces between pores of the porous AlO 2  mold are controlled by changing process parameters in the anodizing, like electrolyte used, voltage, time, etc. 
         [0021]    When the porous AlO 2  mold has pores forming a uniform pattern a light extraction efficiency is improved by forming a photonic crystal structure, which has pores with proper sizes and a proper cycle, on a surface of the n-type semiconductor and a surface of the p-type semiconductor. Besides, a proper mask can be deposed on a surface of the aluminum mold so that, in the process of anodizing, area below the mask does not have any pore, which differs from the other porous structure of areas without the mask covered. Hence, the porous AlO 2  mold can have photonic crystal resonant cavities and a special porous structure obtained with a mask. 
         [0022]    Please refer to  FIG. 2A  to  FIG. 2E , which are views showing a first imprint method. As shown in the figures, a porous AlO 2  mold according to the present invention has a first imprint method, comprising the following 
         [0023]    (b 1 ) A polymer resist  22  is coated on a surface of an object, like a first substrate  21 . 
         [0024]    (b 2 ) The object is imprinted by the porous AlO 2  mold. 
         [0025]    (b 3 ) After cooling down the temperature, the polymer resist  22  is removed through etching, and an area on the surface of the object is thus revealed. 
         [0026]    (b 4 ) In the end, the object is etched on the area to obtain a sub-micro pattern 
         [0027]    Please refer to  FIG. 3A  to  FIG. 3G  which are views showing a second imprint method. As shown in the figures, a porous AlO 2  mold according to the present invention has a second imprint method, comprising the following steps: 
         [0028]    (c 1 ) A protection layer  23  and then a polymer resist  22  are sequentially coated on a surface of an object, like a first substrate  21 . 
         [0029]    (c 2 ) The object is imprinted by the porous AlO 2  mold. 
         [0030]    (c 3 ) After cooling down the temperature, the polymer resist  22  is removed through etching to reveal the protection layer  23 ; thus, after removing the polymer resist  22 , the protection layer  23  is used as an etching barrier. 
         [0031]    (c 4 ) Then, the protection layer  23  is etched to reveal an area on the surface of the object. 
         [0032]    (c 5 ) In the end, the object is etched on the area to obtain a sub-micro pattern. 
         [0033]    Please refer to  FIG. 4A  to  FIG. 4G  which are views showing a third imprint method. As shown in the figures, a porous AlO 2  mold according to the present invention has a third imprint method, comprising the following steps: 
         [0034]    (d 1 ) A polymer resist  22  is coated on a surface of an object, like a first substrate  21 . 
         [0035]    (d 2 ) The object is imprinted by the porous AlO 2  mold. 
         [0036]    (d 3 ) After cooling down the temperature, a protection layer  23  is coated on the polymer resist and surface of the object. 
         [0037]    (d 4 ) Then, through a process of lifting-off, the polymer resist  22  together with portions of the protection layer  23  just right above the polymer resist  22  is removed to reveal an area on the surface of the object. 
         [0038]    (d 5 ) In the end, the object is etched on the area to obtain a sub-micro pattern 
         [0039]    Please refer to  FIG. 5A  to  FIG. 5D , which are views showing fabricating a p-side up LED. As shown in the figures, at first, step (e), a first substrate  31  is imprinted by a first, a second or a third imprint method according to the present invention and then the first substrate  31  is sequentially grown with epitaxy layers of an n-type semiconductor  32 , an active layer  33  and a p-type semiconductor  34 . And then, step (f), the p-type semiconductor  34  is imprinted by the first, the second or the third imprint method to obtain a sub-micro pattern. Hence, a p-side up LED is obtained. 
         [0040]    Please refer to  FIG. 6A  to  FIG. 6E  which are views showing fabricating an n-side up LED. As shown in the figures, at first, step (g), a first substrate  31  is sequentially grown with epitaxy layers of an n-type semiconductor  32 , an active layer  33  and a p-type semiconductor  34  and then the p-type semiconductor  34  is imprinted by a first, a second or a third imprint method according to the present invention. Then, step (h), a second substrate  35  is bonded on the p-type semiconductor  34  to obtain a bonded layer  36 . Then, step (i), the first substrate  31  is removed to reveal the n-type semiconductor  32 . And then, step (j), the n-type semiconductor  32  is imprinted by the first, the second or the third imprint method to obtain a sub-micro pattern. Hence, an n-side up LED is obtained. 
         [0041]    Consequently, as is described above, a first, a second or a third imprint method according to the present invention is used at various layers of a LED and different patterns are obtained on the p-type semiconduct or the p-type semiconductor and the substrate. 
         [0042]    To sum up, the present invention is a method of fabricating a porous AlO 2  mold having a sub-micro structure, where a porous AlO 2  mold is fabricated with pore size, pore space in between, and film thickness all controlled through process parameters; the porous AlO 2  mold fabricated has good mechanical and chemical characteristics; the fabrication requires no expansive equipment and is easy; and, a sub-micro structure is quickly and cheaply mass-imprinted on a large surface of a LED, a laser diode or a substrate which meets needs of producers. 
         [0043]    The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.