Abstract:
The present invention relates to a method for forming a via in a substrate which includes the flowing steps of: (a) providing a substrate having a first surface and a second surface; (b) forming an accommodating groove and a plurality of pillars on the first surface of the substrate, the accommodating groove having a side wall and a bottom wall, the pillars remaining on the bottom wall of the accommodating groove; (c) forming a first insulating material in the accommodating groove and between the pillars; (d) removing the pillars so as to form a plurality of grooves in the first insulating material; and (e) forming a first conductive metal in the grooves. As a result, thicker insulating material can be formed in the via, and the thickness of the insulating material in the via is even.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application comprises a continuation-in-part of U.S. application Ser. No. 12/241,219, filed Sep. 30, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method for forming a via in a substrate and a substrate with a via, and more particularly to a method for forming an insulating layer on a side wall of a via in a substrate by utilizing a polymer and a substrate with the via. 
         [0004]    2. Description of the Related Art 
         [0005]      FIGS. 1 to 3  show schematic views of a conventional method for forming a via in a substrate. First, referring to  FIG. 1 , a substrate  1  is provided. The substrate  1  has a first surface  11  and a second surface  12 . Afterward, a plurality of grooves  13  are formed on the first surface  11  of the substrate  1 . An insulating layer  14  is then formed on the side wall of the grooves  13  by chemical vapor deposition, and a plurality of accommodating spaces  15  are formed. The material of the insulating layer  14  is usually silicon dioxide. 
         [0006]    Afterward, referring to  FIG. 2 , the accommodating spaces  15  are filled with a conductive metal  16 . The material of the conductive metal  16  is usually copper. Finally, the first surface  11  and the second surface  12  of the substrate  1  are ground or etched so as to expose the conductive metal  16 , as shown in  FIG. 3 . 
         [0007]    In the conventional method, the insulating layer  14  is formed by chemical vapor deposition, so that the thickness of the insulating layer  14  on the side wall of the grooves  13  is limited, and is usually under 0.5 m. Moreover, the thickness of the insulating layer  14  on the side wall of the grooves  13  is not even, that is, the thickness of the insulating layer  14  on the upper side wall of the grooves  13  is not exactly equal to that on the lower side wall of the grooves  13 . Thus, the electrical capacity is not uniform. 
         [0008]    Therefore, it is necessary to provide a method for forming a via in a substrate to solve the above problems. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed to a method for forming a via in a substrate, comprising: (a) providing a substrate having a first surface and a second surface; (b) forming an accommodating groove and a plurality of pillars on the first surface of the substrate, the accommodating groove having a side wall and a bottom wall, the pillars remaining on the bottom wall of the accommodating groove; (c) forming a first insulating material in the accommodating groove and between the pillars; (d) removing the pillars so as to form a plurality of grooves in the first insulating material; and (e) forming a first conductive metal in the grooves. 
         [0010]    In the present invention, thicker insulating material can be formed in the via. Also, the thickness of the insulating material in the via is even. Moreover, the polymer is used as an insulating material in the present invention, so polymers with different materials can be chosen for specific processes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIGS. 1 to 3  are schematic views of a conventional method for forming a via in a substrate; 
           [0012]      FIGS. 4 to 21  are schematic views of a method for forming a via in a substrate according to a first embodiment of the present invention; 
           [0013]      FIGS. 22 to 39  are schematic views of a method for forming a via in a substrate according to a second embodiment of the present invention; 
           [0014]      FIG. 40  is a schematic view of a substrate with a via according to a third embodiment of the present invention; 
           [0015]      FIGS. 41 and 42  are schematic views of a substrate with a via according to a fourth embodiment of the present invention; 
           [0016]      FIGS. 43 and 44  are schematic views of a substrate with a via according to a fifth embodiment of the present invention; and 
           [0017]      FIGS. 45 and 67  show schematic views of a method for forming a via in a substrate according to the fifth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIGS. 4 to 21  show schematic views of a method for forming a via in a substrate according to a first embodiment of the present invention. Referring to  FIG. 4 , a top view of the substrate, and  FIG. 5 , a cross-sectional view along line  5 - 5  in  FIG. 4 , first, a substrate  21  is provided. The substrate  21  has a first surface  211  and a second surface  212 . The substrate  21  is, for example, a wafer or a silicon substrate. Afterward, a groove  231  ( FIG. 6 ) is formed on the first surface  211  of the substrate  21 . The groove  231  has a side wall  232  and a bottom wall  233 . In the embodiment, a first photo resist layer  241  is formed on the first surface  211  of the substrate  21 , and a first opening  242  is formed on the first photo resist layer  241 . 
         [0019]    Referring to  FIG. 6 , the groove  231  is formed on the substrate  21  by etching according to the first opening  242 . The groove  231  is disposed on the first surface  211  of the substrate  21 , and has the side wall  232  and the bottom wall  233 . The first photo resist layer  241  is then removed. 
         [0020]    Referring to  FIG. 7 , a first conductive metal  222  is formed on the side wall  232  and the bottom wall  233  of the groove  231  and the first surface  211  of the substrate  21  by electroplating, so as to form a central groove  234 . In the embodiment, the material of the first conductive metal  222  is copper. 
         [0021]    Afterward, referring to  FIGS. 8 to 12 , a center insulating material  223  is formed in the central groove  234 . In the embodiment, the center insulating material  223  is a polymer  263 . In the present invention, the method for forming the center insulating material  223  in the central groove  234  includes but is not limited to the following three methods. 
         [0022]    The first method is that the polymer  263  is dispersed on the first surface  211  of the substrate  21 , and the position of the polymer  263  corresponds to the central groove  234 , as shown in  FIG. 8 . Alternatively, the polymer  263  can be partially dispersed at a position corresponding to the central groove  234 . Afterward, the polymer  263  is impelled into the central groove  234  by vacuuming so as to form the center insulating material  223 , as shown in  FIG. 9 . 
         [0023]    The second method is that a plurality of first vents  237  are formed to connect the central groove  234  to the second surface  212  of the substrate  21 , as shown in  FIG. 10 , a top view of the substrate  21 , and  FIG. 11 , a cross-sectional view along line  11 - 11  in  FIG. 10 . Afterward, the polymer  263  is dispersed on the first surface  211  of the substrate  21 , and the position of the polymer  263  corresponds to the central groove  234 . Alternatively, the polymer  263  can be partially dispersed at a position corresponding to the central groove  234 . The central groove  234  and the first vents  237  are then filled with the polymer  263  so as to form the center insulating material  223 . 
         [0024]    The third method is that the polymer  263  is atomized and deposited in the central groove  234  by spray coating so as to form the center insulating material  223 , as shown in  FIG. 12 . 
         [0025]    Afterward, referring to  FIG. 13 , the first conductive metal  222  and the center insulating material  223  disposed on the first surface  211  of the substrate  21  are removed by etching or grinding. 
         [0026]    Referring to  FIGS. 14 and 15 , an annular groove  235  is formed on the first surface  211  of the substrate  21 . The annular groove  235  surrounds the first conductive metal  222 . Referring to  FIG. 14 , in the embodiment, a second photo resist layer  243  is formed on the first surface  211  of the substrate  21 , and a second opening  244  is formed on the second photo resist layer  243 . The position of the second opening  244  corresponds to the groove  231 , and the diameter of the second opening  244  is larger than that of the groove  231 . Afterward, referring to  FIG. 15 , the annular groove  235  is formed on the substrate  21  by etching according to the second opening  244 . The annular groove  235  surrounds the first conductive metal  222 , and does not penetrate the substrate  21 . The second photo resist layer  243  is then removed. 
         [0027]    Referring to  FIGS. 16 to 20 , a first insulating material  221  is formed in the annular groove  235 . In the embodiment, the first insulating material  221  is polymer  261 . In the present invention, the method for forming the first insulating material  221  in the annular groove  235  includes but is not limited to the following three methods. 
         [0028]    The first method is that the polymer  261  is dispersed on the first surface  211  of the substrate  21 , and the position of the polymer  261  corresponds to the annular groove  235 , as shown in  FIG. 16 . Alternatively, the polymer  261  can be partially dispersed at a position corresponding to the annular groove  235 . Afterward, the polymer  261  is impelled into the annular groove  235  by vacuuming so as to form the first insulating material  221 , as shown in  FIG. 17 . 
         [0029]    The second method is that a plurality of second vents  238  are formed to connect the annular groove  235  to the second surface  212  of the substrate  21 , as shown in  FIG. 18 , a top view of the substrate  21 , and  FIG. 19 , a cross-sectional view along line  19 - 19  in  FIG. 18 . Afterward, the polymer  261  is dispersed on the first surface  211  of the substrate  21 , and the position of the polymer  261  corresponds to the annular groove  235 . Alternatively, the polymer  261  can be partially dispersed at a position corresponding to the annular groove  235 . The annular groove  235  and the second vents  238  are then filled with the polymer  261  so as to form the first insulating material  221 . 
         [0030]    The third method is that the polymer  261  is atomized and deposited in the annular groove  235  by spray coating so as to form the first insulating material  221 , as shown in  FIG. 20 . 
         [0031]    Afterward, referring to  FIG. 21 , part of the first surface  211  and part of the second surface  212  of the substrate  21  are removed by etching or grinding so as to expose the first conductive metal  222 , the center insulating material  223  and the first insulating material  221 . A substrate  2  with a via according to the first embodiment of the present invention is formed. In the embodiment, the via is formed by the center insulating material  223 , the first conductive metal  222  and the first insulating material  221 . In the present invention, thicker insulating material (the center insulating material  223  and the first insulating material  221 ) can be formed in the central groove  234  and the annular groove  235  of the via. Also, the thickness of the insulating material in the central groove  234  and the annular groove  235  of the via is even. Moreover, the polymer is used as an insulating material in the present invention, so polymers with different materials can be chosen for specific processes. 
         [0032]      FIGS. 22 to 39  show schematic views of a method for forming a via in a substrate according to a second embodiment of the present invention. Referring to  FIG. 22 , a top view of the substrate, and  FIG. 23 , a cross-sectional view along line  23 - 23  in  FIG. 22 , first, a substrate  31  is provided. The substrate  31  has a first surface  311  and a second surface  312 . The substrate  31  is, for example, a wafer or a silicon substrate. Afterward, referring to  FIG. 24 , an annular groove  335  and a pillar  336  are formed on the first surface  311  of the substrate  31 , and the annular groove  335  surrounds the pillar  336 . 
         [0033]    In the embodiment, a first photo resist layer  341  is formed on the first surface  311  of the substrate  31 , a first pattern  342  is formed on the first photo resist layer  341 , and the first pattern  342  is an annular opening, as shown in  FIGS. 22 and 23 . Referring to  FIG. 24 , the annular groove  335  and the pillar  336  are formed on the substrate  31  by etching according to the first pattern  342 . The annular groove  335  surrounds the pillar  336 , and the annular groove  335  does not penetrate the substrate  31 . The first photo resist layer  341  is then removed. 
         [0034]    Referring to  FIGS. 25 to 29 , a first insulating material  321  is formed in the annular groove  335 . In the embodiment, the first insulating material  321  is polymer  361 . In the present invention, the method for forming the first insulating material  321  in the annular groove  335  includes but is not limited to the following three methods. 
         [0035]    The first method is that the polymer  361  is dispersed on the first surface  311  of the substrate  31 , and the position of the polymer  361  corresponds to the annular groove  335 , as shown in  FIG. 25 . Alternatively, the polymer  361  can be partially dispersed at a position corresponding to the annular groove  335 . Afterward, the polymer  361  is impelled into the annular groove  335  by vacuuming so as to form the first insulating material  321 , as shown in  FIG. 26 . Finally, part of the polymer  361  which is outside the annular groove  335  is removed. 
         [0036]    The second method is that a plurality of second vents  338  are formed to connect the annular groove  335  to the second surface  312  of the substrate  31 , as shown in  FIG. 27 , a top view of the substrate  31 , and  FIG. 28 , a cross-sectional view along line  28 - 28  in  FIG. 27 . Afterward, the polymer  361  is dispersed on the first surface  311  of the substrate  31 , and the position of the polymer  361  corresponds to the annular groove  335 . Alternatively, the polymer  361  can be partially dispersed at a position corresponding to the annular groove  335 . The annular groove  335  and the second vents  338  are then filled with the polymer  361  so as to form the first insulating material  321 . Finally, part of the polymer  361  which is outside the annular groove  335  and the second vents  338  is removed. 
         [0037]    The third method is that the polymer  361  is atomized and deposited in the annular groove  335  by spray coating so as to form the first insulating material  321 , as shown in  FIG. 29 . Referring to  FIG. 30 , part of the polymer  361  which is outside the annular groove  335  is removed. 
         [0038]    Referring to  FIGS. 31 and 32 , the pillar  336  of the substrate  31  is removed so as to form a groove  331  on the substrate  31 . The groove  331  has a side wall  332  and a bottom wall  333 . In the embodiment, referring to  FIG. 31 , a second photo resist layer  343  is formed on the first surface  311  of the substrate  31 . A second opening  344  is formed on the second photo resist layer  343 , and the position of the second opening  344  corresponds to the pillar  336 . Afterward, the pillar  336  is removed by dry etching or wet etching according to the second opening  344 , so as to form the groove  331 . The groove  331  has the side wall  332  and the bottom wall  333 . The second photo resist layer  343  is then removed immediately or in a subsequent step. 
         [0039]    Referring to  FIG. 33 , a conductive metal  322  is formed on the side wall  332  and the bottom wall  333  of the groove  331  by electroplating, so as to form a central groove  334 . In the embodiment, the material of the first conductive metal  322  is copper. Part of the first conductive metal  322  which is outside the groove  331  is then removed immediately or in a subsequent step. 
         [0040]    Afterward, referring to  FIGS. 34 to 38 , a center insulating material  323  is formed in the central groove  334 . In the embodiment, the center insulating material  323  is a polymer  363 . In the present invention, the method for forming the center insulating material  323  in the central groove  334  includes but is not limited to the following three methods. 
         [0041]    The first method is that the polymer  363  is dispersed on the first surface  311  of the substrate  31 , and the position of the polymer  363  corresponds to the central groove  334 , as shown in  FIG. 34 . Alternatively, the polymer  363  can be partially dispersed at a position corresponding to the central groove  334 . Afterward, the polymer  363  is impelled into the central groove  334  by vacuuming so as to form the center insulating material  323 , as shown in  FIG. 35 . 
         [0042]    The second method is that a plurality of first vents  337  are formed to connect the central groove  334  to the second surface  312  of the substrate  31 , as shown in  FIG. 36 , a top view of the substrate  31 , and  FIG. 37 , a cross-sectional view along line  37 - 37  in  FIG. 36 . Afterward, the polymer  363  is dispersed on the first surface  311  of the substrate  31 , and the position of the polymer  363  corresponds to the central groove  334 . Alternatively, the polymer  363  can be partially dispersed at a position corresponding to the central groove  334 . The central groove  334  and the first vents  337  are then filled with the polymer  363  so as to form the center insulating material  323 . 
         [0043]    The third method is that the polymer  363  is atomized and deposited in the central groove  334  by spray coating so as to form the center insulating material  323 , as shown in  FIG. 38 . 
         [0044]    Afterward, referring to  FIG. 39 , part of the first surface  311  and part of the second surface  312  of the substrate  31  are removed by etching or grinding so as to expose the first conductive metal  322 , the center insulating material  323  and the first insulating material  321 . A substrate  3  with a via according to the second embodiment of the present invention is formed. 
         [0045]      FIG. 40  shows a schematic view of a substrate with a via according to a third embodiment of the present invention. The substrate  4  with a via comprises a substrate  41 , a first insulating material  421 , a center insulating material  423  and a first conductive metal  422 . 
         [0046]    The substrate  41  has a first surface  411 , a second surface  412  and a via  413 . The via  413  penetrates the substrate  41 , and has an inner side wall  414 . The first insulating material  421  is a hollow pillar disposed on the inner side wall  414  of the via  413 . The center insulating material  423  is a solid pillar, disposed at the center of the via  413 , and spaced from the first insulating material  421 . The first conductive metal  422  is disposed between the first insulating material  421  and the center insulating material  423 , and surrounds the center insulating material  423  so as to form a hollow pillar. In the embodiment, the first insulating material  421  contacts the first conductive metal  422 , and the center insulating material  423  contacts the first conductive metal  422 . That is, a three-layered structure with insulating material and conductive material in alternate layers is formed in the via  413 , and the structure includes the center insulating material  423 , the first conductive metal  422  and the first insulating material  421  from the center to the edge. The center insulating material  423  and the first insulating material  421  may be the same or different. 
         [0047]    The substrate  4  with a via further comprises a passivation layer  451  and a conducting layer  453 . The passivation layer  451  is disposed on the first surface  411  or the second surface  412  of the substrate  41 . In the embodiment, the passivation layer  451  is disposed on the first surface  411  of the substrate  41 . The passivation layer  451  has an opening  452 , so that the passivation layer  451  covers part of the first insulating material  421  and exposes part of the first insulating material  421 . The conducting layer  453  is disposed on the passivation layer  451 , and covers part of the first insulating material  421 , the first conductive metal  422  and the center insulating material  423 . 
         [0048]      FIGS. 41 and 42  show schematic views of a substrate with a via according to a fourth embodiment of the present invention.  FIG. 41  is a top view of the substrate, and  FIG. 42  is a cross-sectional view along line  42 - 42  in  FIG. 41 . The substrate  5  with a via comprises a substrate  51 , a first insulating material  521 , a center insulating material  523 , a first conductive metal  522 , a second insulating material  525  and a second conductive metal  524 . 
         [0049]    The substrate  51  has a first surface  511 , a second surface  512  and a via  513 . The via  513  penetrates the substrate  51 , and has an inner side wall  514 . The first insulating material  521  is a hollow pillar disposed on the inner side wall  514  of the via  513 . The center insulating material  523  is a solid pillar, disposed at the center of the via  513 , and spaced from the first insulating material  521 . The first conductive metal  522  is disposed between the center insulating material  523  and the second insulating material  525 , and surrounds the center insulating material  523  so as to form a hollow pillar. The second insulating material  525  is disposed between the first conductive metal  522  and the second conductive metal  524 , and surrounds the first conductive metal  522  so as to form a hollow pillar. The second conductive metal  524  is disposed between the second insulating material  515  and the first insulating material  521 , and surrounds the second insulating material  525  so as to form a hollow pillar. In the embodiment, the second insulating material  525  contacts the first conductive metal  522 , the second conductive metal  524  contacts the second insulating material  525 , and the second conductive metal  524  contacts the first insulating material  521 . That is, a five-layered structure with insulating material and conductive material in alternate layers is formed in the via  513 , and the structure includes the center insulating material  523 , the first conductive metal  522 , the second insulating material  525 , the second conductive metal  524  and the first insulating material  521  from the center to the edge. The center insulating material  523 , the first insulating material  521  and the second insulating material  525  may be the same or different. The material of the first conductive metal  522  and the second conductive metal  524  may be the same or different. 
         [0050]    Moreover, it is understood that, in the substrate  5  with a via, more layers of insulating material and conductive metal can be placed between the center insulating material  523  and the first insulating material  521 , so as to form a multi-layered structure with insulating material and conductive material in alternate layers. 
         [0051]      FIGS. 43 and 44  show schematic views of a substrate with a via according to a fifth embodiment of the present invention.  FIG. 43  is a top view of the substrate, and  FIG. 44  is a cross-sectional view along line  44 - 44  in  FIG. 43 . The substrate  6  with a via comprises a substrate  61 , a first insulating material  621  and a plurality of grooves  629 . 
         [0052]    The substrate  61  has a first surface  611 , a second surface  612  and a via  613 . The via  613  penetrates the substrate  61 , and has an accommodating groove  614 . The accommodating groove  614  has a side wall  617 . The first insulating material  621  is disposed in the via  613 , and attached to the side wall  617  of the via  613 . The grooves  629  are disposed in the first insulating material  621 . Each of the grooves  629  penetrates the first insulating material  621 , and comprises a center insulating material  627  and a first conductive metal  626 . The center insulating material  627  is a solid pillar, and disposed at the center of the grooves  629 . The first conductive metal  626  surrounds and contacts the center insulating material  627 , and contacts the first insulating material  621 . The first insulating material  621  and the center insulating material  627  may be the same or different. 
         [0053]    Moreover, it is understood that, in the substrate  6  with a via, more layers of insulating material and conductive metal may be placed between the center insulating material  627  and the first conductive metal  626  of each of the grooves  629 , or between the first conductive metal  626  and the first insulating material  621  of each of the grooves  629 , so as to form a multi-layered structure with insulating material and conductive material in alternate layers. 
         [0054]    The substrate  6  with a via further comprises a passivation layer (not shown) and a conducting layer (not shown). The passivation layer is disposed on the first surface  611  or the second surface  612  of the substrate  61 , and has a plurality of openings. The position of each of the openings of the passivation layer corresponds to each of the grooves  629 , and the diameter of each of the openings of the passivation layer is larger than that of each of the grooves  629 , so that the passivation layer covers part of the first insulating material  621  and exposes part of the first insulating material  621 . The conducting layer is disposed on the passivation layer, and covers part of the first insulating material  621 , the first conductive metal  626  and the center insulating material  627 . 
         [0055]      FIGS. 45 and 67  show schematic views of a method for forming a via in a substrate according to the fifth embodiment of the present invention. Referring to  FIG. 45 , a top view of the substrate, and  FIG. 46 , a cross-sectional view along line  46 - 46  in  FIG. 45 , first, a substrate  61  is provided. The substrate  61  has a first surface  611  and a second surface  612 . The substrate  61  is, for example, a wafer or a silicon substrate. Afterward, referring to  FIGS. 51 and 52 , an accommodating groove  614  and a plurality of pillars  636  are formed on the first surface  611  of the substrate  61 . 
         [0056]    In the embodiment, as shown in  FIGS. 44 and 45 , a first photo resist layer  71  is formed on the first surface  611  of the substrate  61 . Then, a first pattern  711  is formed on the first photo resist layer  71 . The first pattern  711  comprises a first opening  712  and a plurality of inner areas  713 . The inner areas  713  are located within the first opening  712  and spaced apart from each other. That is, the inner areas  713  do not contact each other and the side wall of the first opening  712 . 
         [0057]    In the embodiment, the first opening  712  is rectangular and the inner areas  713  are circular from top view, and there are five inner areas  713  in a first opening  712 . However, in other embodiments, two sides of the first opening  712  are curved from top view, as shown in  FIG. 47 ; there are two inner areas  713  in a first opening  712 , as shown in  FIG. 48 ; there are four inner areas  713  arranged in a array in a first opening  712 , as shown in  FIG. 49 . 
         [0058]    Referring to  FIG. 50 , the accommodating groove  614  and the pillars  636  are formed by etching the substrate  61  according to the first pattern  711 . Therefore, the accommodating groove  614  and the pillars  636  are formed at the same time. The accommodating groove  614  corresponds to the first opening  712 , and the pillars  636  correspond to the inner areas  713 . Then, the first photo resist layer  71  is removed. 
         [0059]    Referring to  FIGS. 51 and 52 , wherein  FIG. 52  is a top view of  FIG. 51 . The accommodating groove  614  has a side wall  617  and a bottom wall  615 , the pillars  636  remain on the bottom wall  615  of the accommodating groove  614 . That is, the pillars  636  protrude from the bottom wall  615  of the accommodating groove  614 . In the embodiment, the accommodating groove  614  is rectangular from top view, and the pillars  636  are solid cylinders. The accommodating groove  614  does not penetrate the substrate  61 . Each of the pillars  636  is a part of the substrate  61 , and the top surfaces of the pillars  636  are coplanar with the first surface  611  of the substrate  61 . However, the accommodating groove  614  and the pillars  636  may be in other appearance, which depends on the design of the first pattern  711 . 
         [0060]    Referring to  FIGS. 53 to 54 , a first insulating material  621  is formed in the accommodating groove  614  and between the pillars  636 . In the embodiment, the first insulating material  621  is polymer  72 , and the method for forming the first insulating material  621  includes but is not limited to the following methods. 
         [0061]    The first method is that the polymer  72  is dispersed on the first surface  611  of the substrate  61 , and the position of the polymer  72  corresponds to the accommodating groove  614 , as shown in  FIG. 53 . Alternatively, the polymer  72  can be partially dispersed at a position corresponding to the accommodating groove  614 . Afterward, the polymer  72  is impelled into the accommodating groove  614  by vacuuming so as to form the first insulating material  621 , as shown in  FIG. 54 . Finally, part of the polymer  72  which is outside the accommodating groove  614  is removed. 
         [0062]    The second method is that the polymer  72  is atomized and deposited in the accommodating groove  614  by spray coating so as to form the first insulating material  621 , as shown in  FIG. 54 . Referring to  FIG. 55 , part of the polymer  72  which is outside the accommodating groove  614  is removed. 
         [0063]    Referring to  FIGS. 56 and 57 , the pillars  636  of the substrate  61  are removed so as to form a groove  629  in the first insulating material  621 . In the embodiment, referring to  FIG. 56 , a second photo resist layer  73  is formed on the first surface  611  of the substrate  61 . A plurality of second openings  731  are formed on the second photo resist layer  73 , and the positions of the second openings  731  correspond to the pillars  636 . Preferably, the sizes of the second openings  731  are equal to those of the pillars  636  so as to expose the top surfaces of the pillars  636 . Afterward, referring to  FIG. 57 , the pillars  636  are removed by dry etching or wet etching according to the second opening  731 , so as to form the grooves  629 . The second photo resist layer  73  is then removed immediately or in a subsequent step. In the embodiment, the grooves  629  comprise side surfaces  6291  and bottom surfaces  625 . Bottom surfaces  625  of the grooves  629  and the bottom wall  615  of the accommodating groove  614  are substantially coplanar. However, in other embodiments, the bottom surfaces  625  of the grooves  629  may be higher or lower than the bottom wall  615  of the accommodating groove  614 . 
         [0064]    Referring to  FIG. 58 , a first conductive metal  626  is formed in the grooves  629 . In the embodiment, the material of the first conductive metal  626  is copper and is formed by electroplating. The first conductive metal  626  does not fill the grooves  629 , which forms a plurality of central grooves  634 . That is, the first conductive metal  626  is formed on the side surfaces  6291  and the bottom surfaces  625  of the grooves  629  so as to form the central grooves  634 . Part of the first conductive metal  626  which is dispersed on the first surface  611  is then removed immediately or in a subsequent step. 
         [0065]    Afterward, referring to  FIGS. 59 to 63 , a center insulating material  627  is formed in the central grooves  634 . In the embodiment, the center insulating material  627  is a polymer  74 . In the present invention, the method for forming the center insulating material  627  in the central grooves  634  includes but is not limited to the following three methods. 
         [0066]    The first method is that the polymer  74  is dispersed on the first surface  611  of the substrate  61 , and the position of the polymer  74  corresponds to the central grooves  634 , as shown in  FIG. 59 . Alternatively, the polymer  74  can be partially dispersed at a position corresponding to the central grooves  634 . Afterward, the polymer  74  is impelled into the central grooves  634  by vacuuming so as to form the center insulating material  627 , as shown in  FIG. 60 . 
         [0067]    The second method is that a plurality of first vents  637  are formed to connect the central grooves  634  to the second surface  612  of the substrate  61 , as shown in  FIGS. 61 and 62 , wherein  FIG. 62  is a cross-sectional view along line  62 - 62  in  FIG. 61 . Afterward, the polymer  74  is dispersed on the first surface  611  of the substrate  61 , and the position of the polymer  74  corresponds to the central grooves  634 . Alternatively, the polymer  74  can be partially dispersed at a position corresponding to the central grooves  634 . The central grooves  634  and the first vents  637  are then filled with the polymer  74  so as to form the center insulating material  627 . 
         [0068]    The third method is that the polymer  74  is atomized and deposited in the central grooves  634  by spray coating so as to form the center insulating material  627 , as shown in  FIG. 63 . 
         [0069]    Afterward, referring to  FIG. 44 , part of the first surface  611  and part of the second surface  612  of the substrate  61  are removed by etching or grinding so as to expose the first conductive metal  626 , the center insulating material  627  and the first insulating material  621 . 
         [0070]    Referring to  FIG. 58 , the first conductive metal  626  does not fill the grooves  629 . However, in other embodiment, as shown in  FIG. 64 , the first conductive metal  626  fills the grooves  629 . Therefore, the center insulating material  627  is omitted, and the first conductive metal  626  forms a plurality solid pillars. Then, referring to  FIGS. 65 and 66 , part of the first conductive metal  626  which is outside the grooves  629  is removed. Afterward, referring to  FIG. 67 , part of the first surface  611  and part of the second surface  612  of the substrate  61  are removed by etching or grinding so as to expose the first conductive metal  626 , and the first insulating material  621 . 
         [0071]    While several embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention should not be limited to the particular forms as illustrated, and that all modifications which maintain the spirit and scope of the present invention are within the scope defined in the appended claims.