# Patent

## Title
Method for forming vias in a substrate

## Abstract

The present invention relates to a method for forming vias in a substrate, including the following steps: (a) providing a substrate having a first surface and a second surface; (b) forming a groove on the substrate; (c) filling the groove with a conductive metal; (d) removing part of the substrate which surrounds the conductive metal, wherein the conductive metal is maintained so as to form an accommodating space between the conductive metal and the substrate; (e) forming an insulating material in the accommodating space; and (f) removing part of the second surface of the substrate to expose the conductive metal and the insulating material. In this way, thicker insulating material can be formed in the accommodating space, and the thickness of the insulating material in the accommodating space is even.

## Background
This application is a continuation of U.S. application Ser. No. 12/183,140, flied Jul. 31, 2008, which issued as U.S. Pat. No. 7,816,265, and which claims priority to TAIWAN 096128415, filed on Aug. 2, 2007.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming vias in a substrate, and more particularly to a method for forming an insulating layer on the side wall of vias in a substrate by using polymer.
2. Description of the Related Art
FIGS. 1 to 3 show schematic views of a conventional method for forming vias 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 is 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 is formed. The material of the insulating layer 14 is usually silicon dioxide.
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.
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 μm. 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.
Therefore, it is necessary to provide a method for forming vias in a substrate to solve the above problems.
SUMMARY OF THE INVENTION
The present invention is directed to a method for forming vias in a substrate, which comprises the following steps: (a) providing a substrate having a first surface and a second surface; (b) forming a groove on the substrate; (c) filling the groove with a conductive metal; (d) removing part of the substrate which surrounds the conductive metal, wherein the conductive metal is maintained so as to form an accommodating space between the conductive metal and the substrate; (e) forming an insulating material in the accommodating space; and (f) removing part of the second surface of the substrate to expose the conductive metal and the insulating material.
In the present invention, thicker polymer can be formed in the accommodating space. Also, the thickness of the insulating material in the accommodating space is even. Moreover, the polymer is used as an insulating material in the present invention, so that the polymers with different materials can be chosen for specific processes.



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 to 3 are schematic views of a conventional method for forming vias in a substrate;
FIGS. 4 to 19 are schematic views of a method for forming vias in a substrate according to a first embodiment of the present invention; and
FIGS. 20 to 27 are schematic views of a method for forming vias in a substrate according to a second embodiment of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
FIGS. 4 to 19 show the schematic views of the method for forming vias in a substrate according to the first embodiment of the present invention. Referring to FIG. 4, a top view of the substrate 2, and FIG. 5, a cross-sectional view of the substrate 2 along line 5-5 in FIG. 4, first, a substrate 2 is provided. The substrate 2 has a first surface 21 and a second surface 22. The substrate 2 is, for example, a wafer or made from silicon. Afterward, a first photo resist layer 23 is formed on the first surface 21 of the substrate 2, and a first opening 231 is formed on the first photo resist layer 23. In the embodiment, the first opening 231 is circular from the top view. It is understood that the first opening 231 may be square from the top view.
Referring to FIG. 6, a groove 24 is formed on the substrate 2 according to the first opening 231 by etching or other methods, and the groove 24 does not penetrate the substrate 2. Afterward, the first photo resist layer 23 is removed. Then, referring to FIG. 7, the groove 24 is filled with a conductive metal 25. In the embodiment, the material of the conductive metal 25 is copper, and the conductive metal 25 fills up the groove 24 by electroplating. It is understood that the conductive metal 25 may not fill up the groove 24, and forms a central groove 26, that is, the conductive metal 25 is formed on the side wall of the groove 24 only, as shown in FIG. 8.
Referring to FIG. 9, the conductive metal 25 which is outside the groove 24 is removed by etching or grinding so as to expose the first surface 21 of the substrate 2. Then, referring to FIGS. 10 to 12, part of the substrate 2 which surrounds the conductive metal 25 is removed, and the conductive metal 25 is maintained so as to form an accommodating space 28 between the conductive metal 25 and the substrate 2. In the embodiment, the accommodating space 28 is formed by the following methods. Referring to FIG. 10, a top view of the substrate 2, and FIG. 11, a cross-sectional view of the substrate 2 along line 11-11 in FIG. 10, first, a second photo resist layer 27 is formed on the first surface 21 of the substrate 2. A second opening 271 is then formed on the second photo resist layer 27, and is at a position corresponding to the groove 24. The second opening 271 is larger than the first opening 231 (FIGS. 4 and 5) so as to expose the conductive metal 25. In the embodiment, the second opening 271 is circular and has a central axis, the groove 24 is circular and has a central axis, and the central axes of the second opening 271 and the groove 24 are the same, that is, the central axis of the second opening 271 is the central axis of the groove 24. It is understood that the central axes of the second opening 271 and the groove 24 may not be the same, but the conductive metal 25 must be exposed. Then, referring to FIG. 12, part of the substrate 2 which surrounds the conductive metal 25 is removed by etching or other methods, and the conductive metal 25 is maintained so as to form an accommodating space 28 between the conductive metal 25 and the substrate 2. The accommodating space 28 surrounds the conductive metal 25. The second photo resist layer 27 is then removed.
Referring to FIGS. 13 to 18, an insulating material is formed in the accommodating space 28. In the embodiment, the insulating material is polymer 29. However, the insulating material may be silicon dioxide or other material with a property of insulation. In the present invention, the method for forming the polymer 29 in the accommodating space 28 includes but is not limited to the following three methods.
The first method is that the polymer 29 is dispersed on the first surface 21 of the substrate 2, and the position of the polymer 29 corresponds to the accommodating space 28, as shown in FIG. 13. Afterward, the polymer 29 is sucked into the accommodating space 28 by vacuuming, as shown in FIG. 14. Finally, part of the polymer 29 which is outside the accommodating space 28 is removed, as shown in FIG. 18.
The second method is that a plurality of vents 30 is formed to connect the accommodating space 28 to the second surface 22 of the substrate 2, as shown in the top view of FIG. 15. Afterward, the polymer 29 is dispersed on the first surface 21 of the substrate 2, and the position of the polymer 29 corresponds to the accommodating space 28. The accommodating space 28 and the vents 30 are then filled with the polymer 29, as shown in FIG. 16. Finally, part of the polymer 29 which is outside the accommodating space 28 and the vents 30 is removed.
The third method is that the polymer 29 is atomized and deposited in the accommodating space 28 by spray coating, as shown in FIG. 17. Finally, part of the polymer 29 which is outside the accommodating space 28 is removed, as shown in FIG. 18.
It should be noted that in the previous steps, if the conductive metal 25 does not fill up the groove 24, it forms a central groove 26 instead, as shown in FIG. 8. In the above-mentioned three methods, the polymer 29 fills up both the accommodating space 28 and the central groove 26.
Finally, referring to FIG. 19, part of the second surface 22 of the substrate 2 is removed by etching or grinding so as to expose the conductive metal 25 and the insulating material (the polymer 29). Part of the first surface 21 of the substrate 2 may preferably be removed by etching or grinding at the same time.
FIGS. 20 to 27 show the schematic views of the method for forming vias in a substrate according to the second embodiment of the present invention. Referring to FIG. 20, a top view of the substrate 4, and FIG. 21, a cross-sectional view of the substrate 4 along line 21-21 in FIG. 20, first, a substrate 4 is provided. The substrate 4 has a first surface 41 and a second surface 42. The substrate 4 is, for example, a wafer or made from silicon. Afterward, a first photo resist layer 43 is formed on the first surface 41 of the substrate 4, and a first opening 431 is formed on the first photo resist layer 43.
Referring to FIG. 22, a groove 44 is formed on the substrate 4 according to the first opening 431 by etching or other methods, and the groove 44 does not penetrate the substrate 4. Afterward, the first photo resist layer 43 is removed. Then, referring to FIG. 23, the groove 44 is filled with a conductive metal 45. In the embodiment, the material of the conductive metal 45 is copper, and the conductive metal 45 fills up the groove 44 by electroplating. It is understood that the conductive metal 45 may not fill up the groove 44.
Referring to FIGS. 24 to 25, part of the substrate 4 which surrounds the conductive metal 45 is removed, and the conductive metal 45 is maintained to form an accommodating space 48 between the conductive metal 45 and the substrate 4. In the embodiment, the accommodating space 48 is formed by the following methods. First, referring to FIG. 24, a second photo resist layer 47 is formed on the second surface 42 of the substrate 4. A second opening 471 is then formed on the second photo resist layer 47, and is at a position corresponding to the groove 44. The second opening 471 is larger than the first opening 431 (FIG. 21). In the embodiment, the second opening 471 is circular and has a central axis, the groove 44 is circular and has a central axis, and the central axes of the second opening 471 and the groove 44 are the same, that is, the central axis of the second opening 471 is the central axis of the groove 44. It is understood that the central axes of the second opening 471 and the groove 44 may not be the same. Then, referring to FIG. 25, part of the substrate 4 which surrounds the conductive metal 45 is removed by etching or other methods, and the conductive metal 45 is maintained so as to form an accommodating space 48 between the conductive metal 45 and the substrate 4. The accommodating space 48 surrounds the conductive metal 45. The second photo resist layer 47 is then removed.
Referring to FIG. 26, an insulating material is formed in the accommodating space 48. In the embodiment, the material of the insulating material is polymer 49. However, the material of the insulating material may be silicon dioxide or other material with a property of insulation. In the present invention, the method for forming the polymer 49 in the accommodating space 48 includes but is not limited to the three methods described above in the first embodiment.
Finally, referring to FIG. 27, part of the second surface 42 of the substrate 4 is removed by etching or grinding to expose the conductive metal 45 and the insulating material (the polymer 49). Part of the first surface 41 of the substrate 4 may preferably be removed by etching or grinding at the same time.
In the present invention, thicker insulating material (polymer 29, 49 for example) can be formed in the accommodating space 28, 48. Also, the thickness of the insulating material (polymer 29, 49 for example) in the accommodating space 28, 48 is even. Moreover, the polymer 29, 49 is used is as an insulating material in the present invention, so that the polymers with different materials can be chosen for specific processes.
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.

## Claims

1. A method for forming vias in a substrate, comprising:
(a) providing a substrate having a first surface and a second surface;
(b) forming a groove on the substrate;
(c) filling the groove with a conductive metal;
(d) removing part of the substrate which surrounds the conductive metal, wherein the conductive metal is maintained so as to form an accommodating space between the conductive metal and the substrate;
(e) forming an insulating material in the accommodating space; and
(f) removing part of the second surface of the substrate to expose the conductive metal and the insulating material.

2. The method for forming vias in a substrate according to claim 1, wherein the substrate is made from silicon.

3. The method for forming vias in a substrate according to claim 1, wherein Step (b) further comprising:
(b1) forming a first photo resist layer on the first surface of the substrate;
(b2) forming a first opening on the first photo resist layer; and
(b3) forming the groove on the substrate according to the first opening.

4. The method for forming, vias in a substrate according to claim 3, further comprising a step of removing the first photo resist layer after Step (b3).

5. The method for forming vias in a substrate according to claim 1, wherein the groove does not penetrate the substrate.

6. The method for forming vias in a substrate according to claim 1, wherein the groove is formed by etching.

7. The method for forming vias in a substrate according to claim 1, wherein the conductive metal fills up the groove.

8. The method for forming vias in a substrate according to claim 1, wherein the conductive metal does not fill up the groove so as to form a central groove, and the insulating material fills up the accommodating space and the central groove.

9. The method for forming vias in a substrate according to claim 1, further comprising a step of removing the conductive metal which is outside the groove after Step (c).

10. The method for forming vias in a substrate according to claim 1, wherein Step (d) further comprising:
(d1) forming a second photo resist layer on the first surface of the substrate;
(d2) forming a second opening on the second photo resist layer, wherein the position of the second opening corresponds to the groove; and
(d3) removing part of the substrate which surrounds the conductive metal, wherein the conductive metal is maintained so as to form an accommodating space between the conductive metal and the substrate.

11. The method for forming vias in a substrate according to claim 10, wherein the second opening is larger than the groove, and a central axis of the second opening is a central axis of the groove.

12. The method for forming vias in a substrate according to claim 1, wherein Step (d) further comprising:
(d1) forming a second photo resist layer on the second surface of the substrate;
(d2) forming a second opening on the second photo resist layer, wherein the position of the second opening corresponds to the groove; and
(d3) removing part of the substrate which surrounds the conductive metal, wherein the conductive metal is maintained so as to form an accommodating space between the conductive metal and the substrate.

13. The method for forming vias in a substrate according to claim 12, wherein the second opening is larger than the groove, and a central axis of the second opening is a central axis of the groove.

14. The method for forming vias in a substrate according to claim 1, wherein in Step (d), part of the substrate which surrounds the conductive metal is removed by etching, and the conductive metal is not etched.

15. The method for forming vias in a substrate according to claim 1, wherein the insulating material is polymer.

16. The method for forming vias in a substrate according to claim 15, wherein Step (e) further comprising:
(e1) dispersing the polymer at a position corresponding to the accommodating space; and
(e2) sucking the polymer into the accommodating space by vacuuming.

17. The method for forming vias in a substrate according to claim 15, wherein Step (e) further comprising:
(e1) forming a plurality of vents to connect the accommodating space to the second surface of the substrate;
(e2) dispersing the polymer at a position corresponding to the accommodating space; and
(e3) tilling the accommodating space and the vents with the polymer.

18. The method for forming vias in a substrate according to claim 15, wherein the polymer is atomized and deposited in the accommodating space by spray coating.

19. The method for forming vias in a substrate according to claim 1, wherein Step (f) further comprising:
removing part of the first surface of the substrate by etching or grinding.

20. The method for forming vias in a substrate according to claim 1, wherein the second surface of the substrate is etched or ground.