US20150068911A1

US20150068911A1 - Copper plating apparatus, copper plating method and method for manufacturing semiconductor device

Info

Publication number: US20150068911A1
Application number: US14/098,794
Authority: US
Inventors: Fumitoshi Ikegaya; Toshiyuki Morita
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2013-09-12
Filing date: 2013-12-06
Publication date: 2015-03-12

Abstract

A copper plating apparatus according to an embodiment includes a plating tank configured to have a copper member and a plating member being disposed in an interior of the plating tank, a blocking film configured to partition the interior of the plating tank into an anode chamber where the copper member is to be disposed and a cathode chamber where the plating member is to be disposed, the blocking film being configured to transmit copper ions and not transmit an additive agent, a supply unit configured to supply the additive agent to the anode chamber, and a power supply configured to apply a voltage between the copper member and the plating member.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from U.S. Provisional Patent Application 61/876,976, filed on Sep. 12, 2013; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a copper plating apparatus, a copper plating method and a method for manufacturing a semiconductor device.

BACKGROUND

Conventionally, interconnects, etc., are formed by plating copper on a silicon substrate when manufacturing a semiconductor device. Due to the shrinking of semiconductor devices in recent years, it is also necessary to increase the precision of the copper plating. Further, it is necessary to reduce the processing cost of the copper plating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing a copper plating apparatus according to an embodiment;

FIG. 2 is a flowchart showing the copper plating method according to the embodiment;

FIG. 3A to FIG. 3D are drawings showing the copper plating method according to the embodiment; and

FIG. 4 is a graph showing the change over time of the dust count of a comparative example, where the horizontal axis is the plating processing time after placing a new copper member, and the vertical axis is the dust count.

DETAILED DESCRIPTION

A copper plating apparatus according to an embodiment includes a plating tank configured to have a copper member and a plating member being disposed in an interior of the plating tank, a blocking film configured to partition the interior of the plating tank into an anode chamber where the copper member is to be disposed and a cathode chamber where the plating member is to be disposed, the blocking film being configured to transmit copper ions and not transmit an additive agent, a supply unit configured to supply the additive agent to the anode chamber, and a power supply configured to apply a voltage between the copper member and the plating member.
A copper plating method according to an embodiment includes disposing a copper member in an anode chamber of a plating tank, supplying plating liquid including an additive agent to the anode chamber, disposing a first plating member in a cathode chamber partitioned from the anode chamber by a blocking film configured to transmit copper ions and not transmit the additive agent, and supplying the plating liquid including the additive agent to the cathode chamber. The method includes applying a voltage to cause the copper member to be positive and the first plating member to be negative to perform copper plating on the first plating member and form a black film at a surface of the copper member. The method includes replacing the first plating member with a second plating member after the black film is formed. And the method includes applying a voltage to cause the copper member to be positive and the second plating member to be negative to perform copper plating on the second plating member while supplying the additive agent to the cathode chamber without supplying the additive agent to the anode chamber.
An embodiment of the invention will now be described with reference to the drawings.
FIG. 1 is a drawing showing a copper plating apparatus according to the embodiment.
As shown in FIG. 1, a plating cell 10, a plating liquid supply unit 11, an additive agent supply unit 12, and a plating liquid recovery unit 13 are provided in the copper plating apparatus 1 according to the embodiment. In the copper plating apparatus 1, multiple plating cells 10 are provided for one set of the plating liquid supply unit 11, the additive agent supply unit 12, and the plating liquid recovery unit 13.
The plating liquid supply unit 11 is a unit that supplies a plating liquid 106 (VMS: Vergin Make up Solution) not including an additive agent 107 (referring to FIG. 3A) to the plating cell 10. The plating liquid 106 is, for example, an aqueous copper sulfate solution. The additive agent supply unit 12 is a unit that supplies the additive agent 107 to the plating liquid 106. The additive agent 107 includes, for example, an accelerator that promotes the plating, a suppressor that suppresses the plating, and a leveler that levels the plating layer. The accelerator includes, for example, SPS (bis 3-sulfopropyl disulfide disodium). The suppressor includes, for example, PEG (polyethylene glycol). The leveler includes, for example, various dielectrics. The plating liquid recovery unit 13 is a unit that recovers the used plating liquid 106. A pump (not shown) and a filter (not shown) are provided in the plating liquid supply unit 11; and a pump (not shown) and a filter (not shown) are provided in the additive agent supply unit 12.
An external tank 20 is provided in the plating cell 10; and a plating tank 21 is provided inside the external tank 20. A blocking film 22 is provided in the interior of the plating tank 21. The interior of the plating tank 21 is partitioned into an anode chamber 23 and a cathode chamber 24 by the blocking film 22; the anode chamber 23 is positioned at the lower portion of the plating tank 21 interior; and the cathode chamber 24 is positioned at the upper portion of the plating tank 21 interior. The blocking film 22 is a film, e.g., a membrane, e.g., an ion exchange film, that transmits copper ions and does not transmit the polymer material that is the component of the additive agent 107.
A resistance film 25 is provided inside the cathode chamber 24 of the plating tank 21. The resistance film 25 is made of an insulating material such as a resin, a ceramic, etc., is a plate in which many fine holes are formed, and is a film used to provide resistance to the flow of the copper ions. The plating thickness formed on the silicon wafer becomes uniform by interposing the resistance film 25 between the anode and the cathode. Stepped portions for holding the blocking film 22 and the resistance film 25 are formed at the inner side surface of the plating tank 21. To this end, the inner diameter of the plating tank 21 decreases downward in stages.
Also, a power supply plate 26 is provided at the bottom portion of the plating tank 21 to hold a copper member 100, which is used as the plating material, and to apply a potential to the copper member 100. Above the plating tank 21, a holder 27 is provided to hold a silicon wafer 102, which is the plating member, cause the silicon wafer 102 to rotate, and apply a potential. A power supply 28 is provided outside the external tank 20 to apply a voltage between the power supply plate 26 and the holder 27 to cause the power supply plate 26 to be positive and cause the holder 27 to be negative.
In the plating cell 10, a bath 31 that holds the plating liquid, pumps 32 and 33 that cause the plating liquid to flow, and filters 34 and 35 that remove dust from the plating liquid are provided outside the external tank 20.
Further, a conduit 41 is connected between the anode chamber 23 of the plating tank 21 and the pump 32; a conduit 42 is connected between the pump 32 and the filter 34; and a conduit 43 is connected between the filter 34 and the anode chamber 23. Thereby, an anode-side circulation water path 37 in which the plating liquid 106 circulates in the order of (anode chamber 23-conduit 41-pump 32-conduit 42-filter 34-conduit 43-anode chamber 23) is made.
Also, a conduit 44 is connected between the bottom portion of the external tank 20 and the bath 31; a conduit 45 is connected between the bath 31 and the pump 33; a conduit 46 is connected between the pump 33 and the filter 35; and a conduit 47 is connected between the filter 35 and the cathode chamber 24 of the plating tank 21. Thereby, a cathode-side circulation water path 38 in which the plating liquid 106 circulates in the order of (cathode chamber 24-external tank 20-conduit 44-bath 31-conduit 45-pump 33-conduit 46-filter 35-conduit 47-cathode chamber 24) is made.
On the other hand, a conduit 48 is connected between the plating liquid supply unit 11 and the anode chamber 23. A valve 49 is provided partway through the conduit 48. A conduit 57 is connected between the bath 31 and a portion of the conduit 48 that is more on the plating liquid supply unit 11 side than is the valve 49. A valve 58 is provided partway through the conduit 57. A conduit 51 is connected between the additive agent supply unit 12 and the bath 31. A valve 52 is provided partway through the conduit 51. A conduit 53 is connected between the additive agent supply unit 12 and the conduit 41. A valve 54 is provided partway through the conduit 53. Thereby, the additive agent supply unit 12 can supply the additive agent 107 to the anode-side circulation water path 37 via the conduit 53 and the valve 54.
A conduit 55 is connected between the anode chamber 23 and the bath 31. A valve 56 is provided partway through the conduit 55. A conduit 59 is interposed between the bath 31 and the plating liquid recovery unit 13. A valve 60 is provided partway through the conduit 59.
The operation of the copper plating apparatus 1, i.e., a copper plating method according to the embodiment, will now be described. The copper plating method according to the embodiment is a portion of a method for manufacturing a semiconductor device.
FIG. 2 is a flowchart showing the copper plating method according to the embodiment.
FIG. 3A to FIG. 3D are drawings showing the copper plating method according to the embodiment.
In FIG. 3A to FIG. 3D, the additive agent 107 is schematically illustrated by the gray circles.
First, as shown in FIG. 1, the copper plating apparatus 1 is prepared. In the copper plating apparatus 1 at this stage, the blocking film 22 and the resistance film 25 are not mounted inside the plating tank 21; the copper member 100 and the silicon wafer 102 are not mounted as well; and the plating liquid 106 is not introduced. Further, all of the valves are closed.
Then, as shown in step S1 of FIG. 2, a new copper member 100 is prepared; and the surface of the copper member 100 is cleaned. For example, the surface of the copper member 100 is etched using sulfuric acid or aqueous hydrogen peroxide; and subsequently, water rinse is performed.
Continuing as shown in step S2, the copper member 100 is placed inside the anode chamber 23 of the plating tank 21 and connected to the power supply plate 26.
Then, as shown in step S3, the anode chamber 23 interior is filled with the plating liquid 106 (the VMS) that does not include the additive agent 107. Specifically, the pump (not shown) inside the plating liquid supply unit 11 is caused to operate; the valve 49 is opened; and the pump 32 is caused to operate. Thereby, the plating liquid 106 (the VMS) is supplied from the plating liquid supply unit 11 to the interior of the anode chamber 23 via the conduit 48; and the plating liquid 106 circulates through the anode-side circulation water path 37. When the anode chamber 23 is filled with the plating liquid 106, the valve 49 is closed.
Continuing as shown in step S4, the additive agent 107 is supplied to the conduit 41 by opening the valve 54. Thereby, the additive agent 107 flows into the anode-side circulation water path 37, mixes with the plating liquid 106, and is supplied to the interior of the anode chamber 23. At this time, the concentration of the additive agent 107 in the plating liquid 106 is set to be, for example, not less than 1 ppm. Subsequently, the valve 54 is closed.
Then, as shown in step S5 of FIG. 2 and FIG. 3A, the plating cell 10 is assembled. Specifically, the blocking film 22 is mounted inside the plating tank 21; and the resistance film 25 is mounted. Then, a dummy silicon wafer 101 is mounted to the holder 27. Then, the plating liquid 106 is supplied to the interior of the anode chamber 23 by opening the valve 49. The plating liquid 106 that is supplied to the interior of the anode chamber 23 passes through the blocking film 22, enters the cathode chamber 24 as well, and fills the entire plating tank 21.
Continuing, the plating liquid 106 and the additive agent 107 that overflow from the plating tank 21 accumulate at the bottom portion of the external tank 20 and are returned to the bath 31 via the conduit 44. Also, by opening the valve 60, a portion of the plating liquid 106 and the additive agent 107 can be recovered into the plating liquid recovery unit 13 via the conduit 59. Thereby, new plating liquid 106 is constantly supplied to the interior of the plating cell 10.
Further, by causing the pump 33 to operate, the plating liquid 106 is circulated inside the cathode-side circulation water path 38. Then, by causing the additive agent supply unit 12 to operate and by opening the valve 52, the additive agent 107 is introduced to the interior of the bath 31 and is supplied to the interior of the cathode chamber 24 via the cathode-side circulation water path 38. Therefore, at this stage as shown in FIG. 3A, a mixed liquid of the plating liquid 106 and the additive agent 107 is supplied to both the interior of the anode chamber 23 and the interior of the cathode chamber 24. However, the plating liquid 106 and the additive agent 107 that are inside the anode chamber 23 and the plating liquid 106 and the additive agent 107 that are inside the cathode chamber 24 are circulated independently through the circulation water paths. Although the plating liquid 106 can move between the anode chamber 23 and the cathode chamber 24 via the blocking film 22, the movement of the additive agent 107 is blocked by the blocking film 22.
Then, as shown in step S6 of FIG. 2 and FIG. 3B, a voltage is applied by the power supply 28 to cause the copper member 100 to be positive and the silicon wafer 101 to be negative. Thereby, a copper plating layer 110 is formed by copper plating being performed on the surface of the dummy silicon wafer 101. At this time, monovalent copper ions (Cu⁺) and bivalent copper ions (Cu²⁺) are produced from the copper member 100 and reach the silicon wafer 101 by moving through the plating liquid 106. Then, the ions bond with electrons at the surface of the silicon wafer 101 and precipitate as simple copper.
At this time, foreign matter 112 forms at the copper plating layer 110 due to the monovalent copper ions (Cu⁺). The formation of the foreign matter 112 reduces the uniformity of the copper plating layer 110 and mixes into the plating liquid 106 to become dust. On the other hand, inside the anode chamber 23, a black film 108 is formed on the surface of the copper member 100 by the additive agent 107 reacting with the copper. The black film 108 is made of, for example, a mixture of Cu₂Cl₂, Cu₂O, and Cu₃P.
In this process, it is favorable for the plating amount for the silicon wafer 101 to be not less than (S×14) coulombs, where the surface area of the region where the surface of the copper member 100 contacts the plating liquid 106 is S (cm²). Thereby, the black film 108 can be reliably formed. For example, in the case where the copper member 100 is a circular plate having a diameter of 300 mm and one face of the copper member 100 contacts the plating liquid 106, the surface area S is about 706.5 cm². In such a case, because 706.5×=9891, it is sufficient to perform plating of 10 kilocoulombs or more. If necessary, a plurality of the dummy silicon wafers 101 may be used sequentially.
Then, as shown in step S7 of FIG. 2, the quality of the copper plating layer 110 formed on the silicon wafer 101 is inspected. Then, if the quality is defective, the flow returns to step S6; and the plating processing of the dummy silicon wafer 101 is continued. On the other hand, if the quality is good, the flow proceeds to step S8 to transition to the main plating processing.
Continuing as shown in step S8 of FIG. 2 and FIG. 3C, the dummy silicon wafer 101 is removed from the holder 27; and the silicon wafer 102 for the main plating is mounted. Because, the additive agent 107 is not supplied to the interior of the anode chamber 23 after the start of the plating processing of the dummy shown in step S6, the concentration of the additive agent 107 of the plating liquid 106 inside the anode chamber 23 decreases as the plating processing of the dummy progresses. On the other hand, because the additive agent 107 is supplied continuously to the interior of the cathode chamber 24 via the conduit 51, the concentration of the additive agent 107 inside the cathode chamber 24 is substantially constant.
Then, as shown in step S9 of FIG. 2 and FIG. 3D, copper plating of the silicon wafer 102 is performed by the power supply 28 again applying the voltage. At this time, although the additive agent 107 is supplied to the interior of the cathode chamber 24 via the conduit 51, the additive agent 107 is not supplied to the interior of the anode chamber 23. Although the copper plating layer 110 is formed on the surface of the silicon wafer 102 by the plating processing, the monovalent copper ions (Cu⁺) substantially are not produced because the surface of the copper member 100 is covered with the black film 108; and, accordingly, the foreign matter 112 substantially does not form. Also, the additive agent 107 that remained inside the anode chamber 23 is consumed by the copper plating processing and substantially no longer exists.
Thus, the copper plating layer 110 can be formed on the surface of the silicon wafer 102 for the main plating. Then, when the plating processing of one silicon wafer 102 ends, the silicon wafer 102 is removed from the copper plating apparatus 1; a new silicon wafer 102 is mounted to the copper plating apparatus 1; and the plating processing is continued. Thus, the plating processing can be performed sequentially for multiple silicon wafers 102 until the copper member 100 is consumed and can no longer be used. When the copper member 100 is replaced, the main plating processing shown in step S9 is performed after re-implementing the preparation processes shown in steps S1 to S8 described above.
Then, a conductive member such as an interconnect, etc., can be formed on the silicon wafer 102 by selectively forming the copper plating layer 110 on the silicon wafer 102 in step S9, or by uniformly forming the copper plating layer 110 in step S9 and subsequently performing patterning. Thereafter, the semiconductor device can be manufactured by performing the necessary processing.
Effects of the embodiment will now be described.
In the embodiment, the plating liquid 106 including the additive agent 107 is supplied to the interior of the anode chamber 23 in the dummy plating process shown in step S6 of FIG. 2 and FIG. 3B. Therefore, the black film 108 can be formed quickly on the surface of the copper member 100. Thereby, in the main plating process shown in step S9 of FIG. 2 and FIG. 3D, the production of the monovalent copper ions can be suppressed; and the formation of the foreign matter 112 on the silicon wafer 102 can be suppressed. As a result, a uniform copper plating layer 110 can be formed on the silicon wafer 102. Further, dust that is due to the foreign matter 112 coming off into the plating liquid 106 can be prevented from occurring.
Also, in the embodiment, after introducing a constant amount of the additive agent 107 into the anode chamber 23 at the start of the dummy plating process, the plating processing is performed by supplying only the plating liquid 106 to the interior of the anode chamber 23 without supplying the additive agent 107. Thereby, the black film 108 can be prevented from being formed to be excessively thick; and the black film 108 can be prevented from coming off and becoming dust. Also, the cost of the plating processing can be suppressed because the additive agent 107 that is inside the anode chamber 23 is not consumed excessively. On the other hand, because the additive agent 107 is supplied continuously to the interior of the cathode chamber 24, the copper plating layer 110 can be formed stably.
A comparative example will now be described.
FIG. 4 is a graph showing the change over time of the dust count of the comparative example, where the horizontal axis is the plating processing time after placing a new copper member, and the vertical axis is the dust count.
In the comparative example, the plating processing was performed using a new copper member 100 by supplying the plating liquid 106 not including the additive agent 107 to the interior of the anode chamber 23 and by supplying the plating liquid 106 including the additive agent 107 to the interior of the cathode chamber 24.
As a result, as shown in FIG. 4, after a constant amount of time has elapsed after the start of the plating processing, the dust count inside the plating liquid 106 greatly increases and subsequently decreases. It is considered that the increase of the dust count is because the black film 108 is not formed on the surface of the copper member 100, monovalent copper ions are formed, and the foreign matter 112 forms on the silicon wafer because the additive agent 107 is not supplied to the interior of the anode chamber 23. When the foreign matter 112 forms at the copper plating layer 110, open defects occur easily for interconnects in the case where the interconnects are formed from the copper plating layer 110.
Further, it is considered that the reason that the dust count decreased after increasing once is because the additive agent 107 entered the anode chamber 23 little by little via the blocking film 22; and thereby, the black film 108 was formed. Therefore, it also may be considered to perform the plating processing by utilizing this phenomenon and waiting until the dust count decreases. However, in such a case, it is necessary to continue the plating processing of the dummy until the black film 108 is formed by the additive agent 107 leaking into the anode chamber 23 and the formation of the foreign matter 112 decreases sufficiently; and the productivity of the plating processing decreases. In an example, dummy plating processing for several days is necessary until the black film 108 is formed by the additive agent 107 leaking via the blocking film 22 and the dust count decreases. Conversely, according to the embodiment described above, transition to the main plating processing is possible when the plating processing of the dummy is performed for several minutes.
It also may be considered to not provide the blocking film 22 and to perform the plating processing by supplying the plating liquid 106 including the additive agent 107 to the entire interior of the plating tank 21. However, in such a case, the black film 108 that has become too thick comes off, mixes into the plating liquid 106, and causes defects such as embedding defects, etc. Moreover, the consumption of the additive agent 107 is high; and the cost of the plating processing increases. Further, it is necessary to frequently replace the filters 34 and 35 because the dust increases; and this also causes the cost to increase.
According to the embodiment described above, a copper plating apparatus, a copper plating method, and a method for manufacturing the semiconductor device can be realized to perform inexpensive and high-precision copper plating.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.

Claims

What is claimed is:

1. A copper plating apparatus, comprising:

a plating tank configured to have a copper member and a plating member disposed in an interior of the plating tank;

a blocking film configured to partition the interior of the plating tank into an anode chamber where the copper member is to be disposed and a cathode chamber where the plating member is to be disposed, the blocking film being configured to transmit copper ions and not transmit an additive agent;

a supply unit configured to supply the additive agent to the anode chamber; and

a power supply configured to apply a voltage between the copper member and the plating member.

2. The copper plating apparatus according to claim 1, further comprising:

an anode-side circulation water path configured to circulate plating liquid for the anode chamber; and

a cathode-side circulation water path configured to circulate plating liquid for the cathode chamber,

the supply unit being configured to supply the additive agent to the anode-side circulation water path.

3. The copper plating apparatus according to claim 1, wherein the blocking film is an ion exchange film.

4. A copper plating method, comprising:

disposing a copper member in an anode chamber of a plating tank, supplying plating liquid including an additive agent to the anode chamber, disposing a first plating member in a cathode chamber partitioned from the anode chamber by a blocking film configured to transmit copper ions and not transmit the additive agent, and supplying the plating liquid including the additive agent to the cathode chamber;

applying a voltage to cause the copper member to be positive and the first plating member to be negative to perform copper plating on the first plating member and form a black film at a surface of the copper member;

replacing the first plating member with a second plating member after the black film is formed; and

applying a voltage to cause the copper member to be positive and the second plating member to be negative to perform copper plating on the second plating member while supplying the additive agent to the cathode chamber without supplying the additive agent to the anode chamber.

5. The copper plating method according to claim 4, wherein the additive agent contains an accelerator configured to promote the copper plating, a suppressor configured to suppress the copper plating, and a leveler configured to level a copper plating layer.

6. The copper plating method according to claim 4, wherein the additive agent contains polyethylene glycol.

7. The copper plating method according to claim 4, wherein the additive agent contains bis 3-sulfopropyl disulfide disodium.

8. The copper plating method according to claim 4, wherein a concentration of the additive agent in the plating liquid supplied to the anode chamber in the supplying of the plating liquid is not less than 1 ppm.

9. The copper plating method according to claim 4, wherein the plating amount for the first plating member in the forming of the black film is set to be not less than (S×14) coulombs, where the surface area of a region where the surface of the copper member contacts the plating liquid is S (cm²).

10. The copper plating method according to claim 4, wherein the second plating member is a silicon wafer.

11. A method for manufacturing a semiconductor device, comprising:

disposing a copper member in an anode chamber of a plating tank, supplying a plating liquid including an additive agent to the anode chamber, disposing a plating member in a cathode chamber partitioned from the anode chamber by a blocking film configured to transmit copper ions and not transmit the additive agent, and supplying the plating liquid including the additive agent to the cathode chamber;

applying a voltage to cause the copper member to be positive and the plating member to be negative to perform copper plating on the plating member and form a black film at a surface of the copper member;

replacing the plating member with a silicon wafer after the black film is formed; and

applying a voltage to cause the copper member to be positive and the silicon wafer to be negative to perform copper plating on the silicon wafer while supplying the additive agent to the cathode chamber without supplying the additive agent to the anode chamber.

12. The method for manufacturing the semiconductor device according to claim 11, wherein the additive agent contains an accelerator configured to promote the copper plating, a suppressor configured to suppress the copper plating, and a leveler configured to level a copper plating layer.

13. The method for manufacturing the semiconductor device according to claim 11, wherein the additive agent contains polyethylene glycol.

14. The method for manufacturing the semiconductor device according to claim 11, wherein the additive agent contains bis 3-sulfopropyl disulfide disodium.

15. The method for manufacturing the semiconductor device according to claim 11, wherein a concentration of the additive agent in the plating liquid supplied to the anode chamber in the supplying of the plating liquid is not less than 1 ppm.

16. The method for manufacturing the semiconductor device according to claim 11, wherein the plating amount for the plating member in the forming of the black film is set to be not less than (S×14) coulombs, where the surface area of a region where the surface of the copper member contacts the plating liquid is S (cm²).