fig4 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 fig4 , a top view of the substrate , and fig5 , a cross - sectional view along line 5 - 5 in fig4 , 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 ( fig6 ) 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 . referring to fig6 , 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 . referring to fig7 , 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 . afterward , referring to fig8 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 . 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 fig8 . 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 fig9 . 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 fig1 , a top view of the substrate 21 , and fig1 , a cross - sectional view along line 11 - 11 in fig1 . 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 . 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 fig1 . afterward , referring to fig1 , 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 . referring to fig1 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 fig1 , 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 fig1 , 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 . referring to fig1 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 . 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 fig1 . 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 fig1 . 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 fig1 , a top view of the substrate 21 , and fig1 , a cross - sectional view along line 19 - 19 in fig1 . 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 . 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 fig2 . afterward , referring to fig2 , 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 . fig2 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 fig2 , a top view of the substrate , and fig2 , a cross - sectional view along line 23 - 23 in fig2 , 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 fig2 , 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 . 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 fig2 and 23 . referring to fig2 , 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 . referring to fig2 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 . 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 fig2 . 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 fig2 . finally , part of the polymer 361 which is outside the annular groove 335 is removed . 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 fig2 , a top view of the substrate 31 , and fig2 , a cross - sectional view along line 28 - 28 in fig2 . 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 . 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 fig2 . referring to fig3 , part of the polymer 361 which is outside the annular groove 335 is removed . referring to fig3 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 fig3 , 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 . referring to fig3 , 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 . afterward , referring to fig3 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 . 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 fig3 . 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 fig3 . 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 fig3 , a top view of the substrate 31 , and fig3 , a cross - sectional view along line 37 - 37 in fig3 . 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 . 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 fig3 . afterward , referring to fig3 , 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 . fig4 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 . 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 . 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 . fig4 and 42 show schematic views of a substrate with a via according to a fourth embodiment of the present invention . fig4 is a top view of the substrate , and fig4 is a cross - sectional view along line 42 - 42 in fig4 . 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 . 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 . 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 . fig4 and 44 show schematic views of a substrate with a via according to a fifth embodiment of the present invention . fig4 is a top view of the substrate , and fig4 is a cross - sectional view along line 44 - 44 in fig4 . the substrate 6 with a via comprises a substrate 61 , a first insulating material 621 and a plurality of grooves 629 . 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 . 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 . 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 . fig4 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 fig4 , a top view of the substrate , and fig4 , a cross - sectional view along line 46 - 46 in fig4 , 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 fig5 and 52 , an accommodating groove 614 and a plurality of pillars 636 are formed on the first surface 611 of the substrate 61 . in the embodiment , as shown in fig4 and 46 , 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 . 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 fig4 ; there are two inner areas 713 in a first opening 712 , as shown in fig4 ; there are four inner areas 713 arranged in a array in a first opening 712 , as shown in fig4 . referring to fig5 , 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 . referring to fig5 and 52 , wherein fig5 is a top view of fig5 . 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 , and there is a completely empty space between the pillars 636 . 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 . referring to fig5 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 . 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 fig5 . 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 fig5 . finally , part of the polymer 72 which is outside the accommodating groove 614 is removed . 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 fig5 . referring to fig5 , part of the polymer 72 which is outside the accommodating groove 614 is removed . referring to fig5 and 57 , all of the pillars 636 of the substrate 61 are removed completely so as to form a groove 629 in the first insulating material 621 . in the embodiment , referring to fig5 , 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 fig5 , all of the pillars 636 are removed completely 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 . referring to fig5 , 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 . afterward , referring to fig5 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 . 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 fig5 . 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 fig6 . 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 fig6 and 62 , wherein fig6 is a cross - sectional view along line 62 - 62 in fig6 . 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 . 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 fig6 . afterward , referring to fig4 , 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 . referring to fig5 , the first conductive metal 626 does not fill the grooves 629 . however , in other embodiment , as shown in fig6 , 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 fig6 and 66 , part of the first conductive metal 626 which is outside the grooves 629 is removed . afterward , referring to fig6 , 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 . 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 .