Title:
Method and apparatus for acid and additive breakdown removal from copper electrodeposition bath
Kind Code:
A1


Abstract:
A method and apparatus for removing waste material from a plating solution is disclosed. The invention generally provides a plating cell having an electrolyte inlet and an electrolyte drain, an electrolyte storage unit in fluid communication with the electrolyte inlet, and a diffusion dialysis chamber in fluid communication with the electrolyte drain and the electrolyte storage unit. The diffusion dialysis chamber is generally configured to receive at least a portion of used electrolyte solution and remove waste material therefrom in order to provide a refreshed electrolyte solution to the electrolyte storage unit. A method generally includes supplying an electrolyte solution to a copper plating cell, plating copper onto a substrate in the plating cell with the electrolyte solution, removing used electrolyte solution from the plating cell, and refreshing a portion of the used electrolyte solution with a diffusion dialysis device.



Inventors:
Kovarsky, Nicolay Y. (Sunnyvale, CA, US)
Lubomirsky, Dmitry (Cupertino, CA, US)
Application Number:
10/739891
Publication Date:
06/23/2005
Filing Date:
12/18/2003
Assignee:
APPLIED MATERIALS, INC.
Primary Class:
Other Classes:
204/237
International Classes:
C25D21/18; C25D21/22; (IPC1-7): C25D21/18
View Patent Images:
Related US Applications:



Primary Examiner:
ZHENG, LOIS L
Attorney, Agent or Firm:
PATTERSON & SHERIDAN, LLP - - APPLIED MATERIALS (HOUSTON, TX, US)
Claims:
1. An electrochemical plating system, comprising: a plating cell; and a diffusion dialysis device in fluid communication with the plating cell, the diffusion dialysis device configured to remove waste material from an electrolyte solution.

2. The plating system of claim 1, wherein the diffusion dialysis device comprises alternating diluted acid cells and electrolyte cells separated by anionic membranes, the electrolyte cells passing the electrolyte solution therethrough and the diluted acid cells removing the waste material.

3. The plating system of claim 2, wherein the anionic membrane comprises a matrix having a positive charge inside and a selected porosity for selectively passing acids and at least some organic molecules.

4. The diffusion dialysis device of claim 2, wherein the pore size of the anionic membrane is between 50 and 100 angstroms.

5. The plating system of claim 2, wherein the anionic membranes allow negatively charged ions and at least some waste material within the electrolyte solution to diffuse therethrough into the diluted acid cells.

6. The plating system of claim 2, wherein the waste material comprises organic additive breakdown product.

7. The plating system of claim 2, wherein the anionic membranes are more permeable to accelerator and its breakdown products than leveler and its breakdown products and less permeable to suppressor and its breakdown products.

8. The plating system of claim 2, wherein the anionic membranes prevent positively charged copper ions from passing therethrough.

9. The plating system of claim 2, wherein the diffusion dialysis devise comprises between about 25 and about 100 total collective electrolyte cells and diluted acid cells.

10. The plating system of claim 1, wherein the plating cell is divided into a catholyte compartment and an anolyte compartment by a cation membrane, the catholyte compartment for circulating the electrolyte solution therethrough.

11. The system of claim 1, further comprising an electrodialysis cell that receives the electrolyte solution from the diffusion dialysis device.

12. The system of claim 11, wherein the electrodialysis cell comprises at least one cationic membrane between cells having an electrolyte solution containing waste material and cells having a refreshed electrolyte solution.

13. The plating system of claim 1, further comprising an electrolyte storage unit.

14. A diffusion dialysis device for extracting waste material from an electrolyte solution, comprising: a housing having a plurality of anionic membranes positioned therein to define alternating electrolyte cells and diluted acid cells; and a deionized water loop comprising: a supply conduit that supplies a controlled concentration of acid to the diluted acid cells; and a return conduit that receives an outflow from the diluted acid cells.

15. The diffusion dialysis device of claim 14, wherein each anionic membrane comprises a matrix having a positive charge inside and a selected porosity to extract waste material comprising organic breakdown product and acid.

16. The diffusion dialysis device of claim 15, wherein the anionic membranes allow negatively charged ions and at least some of the waste material within the electrolyte solution to diffuse therethrough into the diluted acid cells.

17. The plating system of claim 15, wherein the anionic membranes are more permeable to accelerator and its breakdown products than leveler and its breakdown products and less permeable to suppressor and its breakdown products.

18. The diffusion dialysis device of claim 15, wherein the anionic membranes prevent positively charged copper ions from passing therethrough.

19. The diffusion dialysis device of claim 15, wherein the pore size of the anionic membranes is between 50 and 100 angstroms.

20. A method for plating copper, comprising: supplying an electrolyte solution to a plating cell; plating onto a substrate in the plating cell with the electrolyte solution; removing used electrolyte solution from the plating cell; and refreshing a portion of the used electrolyte solution with a diffusion dialysis device.

21. The method of claim 20, wherein the refreshing a portion of the used electrolyte with the diffusion dialysis devise comprises: receiving the used electrolyte solution in an electrolyte cell of the diffusion dialysis device; urging negative sulfate ions and organic additive breakdown waste material through an anionic membrane into a diluted acid cell; and removing a refreshed electrolyte solution from the electrolyte cell.

22. The method of claim 21, wherein urging comprises maintaining a concentration gradient across the electrolyte cell and the diluted acid cell.

23. The method of claim 20, further comprising receiving the refreshed electrolyte solution in an electrodialysis cell that removes additional organic additives and organic additive breakdown products from the refreshed electrolyte solution.

24. The method of claim 20, wherein the plating cell is divided into a catholyte compartment and an anolyte compartment by a cation membrane, the catholyte compartment for circulating the electrolyte solution therethrough.

25. A method for replenishing a copper plating solution, comprising: receiving a portion of a used electrolyte solution in an electrolyte cell of a diffusion dialysis device; urging negatively charged sulfate ions and organic additive breakdown waste material into a diluted acid cell adjacent the electrolyte cell to provide a refreshed electrolyte solution, wherein the diluted acid cell and the electrolyte cell are separated by an anionic membrane; and returning the refreshed electrolyte solution to the copper plating solution.

26. The method of claim 25, wherein urging comprises maintaining a concentration gradient across the electrolyte cell and the diluted acid cell.

27. The method of claim 25, wherein the receiving step comprises receiving the used electrolyte solution in up to 100 electrolyte cells within a single diffusion dialysis device.

28. The method of claim 25, wherein a collective total of the electrolyte cells and the diluted acid cells is between about 25 and about 100.

Description:

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to removing organic waste material and acid from semiconductor electrolyte solutions.

2. Description of the Related Art

Metallization for sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. More particularly, in devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio interconnect features with a conductive material, such as copper or aluminum. Conventionally, deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) have been used to fill these interconnect features. However, as interconnect sizes decrease and aspect ratios increase, void-free interconnect feature fill via conventional metallization techniques becomes increasingly difficult. As a result, plating techniques such as electrochemical plating (ECP) and electroless plating have emerged as viable processes for filling sub-quarter micron sized high aspect ratio interconnect features in integrated circuit manufacturing processes.

In an ECP process, sub-quarter micron sized high aspect ratio features formed on a substrate surface may be efficiently filled with a conductive material, such as copper. ECP plating processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate, and then the surface features of the substrate are exposed to an electrolyte solution, while an electrical bias is applied between the substrate and an anode positioned within the electrolyte solution. The electrolyte solution is generally rich in ions to be plated onto the surface of the substrate, and therefore, the application of the electrical bias causes these ions to be urged out of the electrolyte solution and to be plated as a metal on the seed layer. The plated metal, e.g., copper, grows in thickness and forms a copper layer over the seed layer that operates to fill the features formed on the substrate surface. The concentration of chemicals in the electrolyte solution must be maintained within a narrow operation window to achieve void free filling of the features.

In order to facilitate and control this plating process, several additives may be utilized in the electrolyte plating solution. For example, a typical electrolyte solution used for copper electroplating may consist of copper sulfate solution, which provides the copper to be plated, having sulfuric acid and copper chloride added thereto. The sulfuric acid may generally operate to modify the acidity and conductivity of the solution. The electrolytic solutions also generally contain various organic molecules, which may be accelerators, suppressors, levelers, brighteners, etc. These organic molecules are generally added to the plating solution in order to facilitate formation of void-free high aspect ratio features and planarized copper deposition. Accelerators, for example, may be sulfide-based molecules that locally accelerate electrical current at a given voltage where they absorb. Suppressors may be polymers of polyethylene glycol, mixtures of ethylene oxides and propylene oxides, or block copolymers of ethylene oxides and propylene oxides which tend to reduce electrical current at the sites where they absorb (the upper edges/corners of high aspect ratio features), and therefore, slow the plating process at those locations, which reduces premature closure of the feature before the feature is completely filled. Levelers may be nitrogen containing, long chain polymers which operate to facilitate planar plating. Additionally, the plating bath usually contains a small amount of chloride, generally between about 20 and about 60 ppm, which provides negative ions needed for adsorption of suppressor molecules on the cathode, while also facilitating proper anode corrosion.

Although the various organic additives facilitate the plating process and offer a control element over the interconnect formation process, they also present a challenge since the additives are known to eventually break down and become waste material in the electrolyte solution that is no longer useful and may even be a contaminant. Conventional plating systems traditionally dealt with these organic waste materials via bleed and feed methods (periodically replacing a portion of the electrolyte), extraction methods (filtering the electrolyte with a charcoal filter), photochemical decomposition methods (using UV in conjunction with ion exchange and acid-resistant filters), and/or ozone treatments (dispensing ozone into the electrolyte). However, these conventional methods are known to be inefficient, expensive to implement and operate, bulky, and/or tend to generate hazardous materials or other kinds of contaminants as byproducts.

Recently, electrodialysis cells (EDC) have been used to substantially remove all of the organic additives from at least a portion of the electrolyte solution in the plating process as discussed in detail in U.S. patent application Ser. No. 10/074,569, which is herein incorporated by reference in its entirety. Substantially all of the additives are removed since membranes used in the EDC are sufficiently dense such that the additives fail to penetrate through the membranes. The EDC requires an electrical supply and may lack the ability to remove acids. However, it may be desirable to remove acids that accumulate during the plating process and to remove certain organic additives and/or organic waste at a faster rate than other organic additives based on the breakdown rates of the various organic additives. For example, the accelerators breakdown faster than the levelers which breakdown faster than the suppressors. Further, it may be desirable in certain applications to remove only a percentage of the organic additives and/or organic waste from the entire electrolyte solution rather than all of the organic additives from a portion of the electrolyte solution.

Therefore, there exists a need for a method and apparatus for removing additive breakdown waste material from semiconductor electroplating baths, wherein the method and apparatus addresses the deficiencies of conventional devices.

SUMMARY OF THE INVENTION

The invention generally provides a plating cell having an electrolyte inlet and an electrolyte drain, an electrolyte storage unit in fluid communication with the electrolyte inlet, and a diffusion dialysis chamber in fluid communication with the electrolyte drain and the electrolyte storage unit. The diffusion dialysis chamber is generally configured to receive at least a portion of used electrolyte solution and remove waste material therefrom in order to provide a refreshed electrolyte solution to the electrolyte storage unit. The method generally includes supplying an electrolyte solution to a copper plating cell, plating copper onto a substrate in the plating cell with the electrolyte solution, removing used electrolyte solution from the plating cell, and refreshing a portion of the used electrolyte solution with a diffusion dialysis device.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 illustrates an exemplary plating system incorporating a diffusion dialysis device (DDD).

FIG. 2 illustrates a schematic view of the DDD in FIG. 1.

FIG. 3 illustrates an exemplary plating system incorporating the DDD and an electrodialysis cell (EDC).

FIG. 4 illustrates a schematic view of the EDC shown in FIG. 3.

FIG. 5 illustrates a schematic view of an alternative EDC.

FIG. 6 illustrates an alternative plating system configuration that incorporates the DDD.

FIG. 7 is a graph showing the rate of removal by the DDD of sulfuric acid from an electrolyte solution.

FIG. 8 is a graph showing the rate of removal of additives and breakdown products from the additives by the DDD from the electrolyte solution.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention generally relates to removal of organic waste material and acid from an electrolyte solution during a plating process with a diffusion dialysis device (DDD). FIG. 1 illustrates an exemplary plating system 100 that includes a diffusion dialysis device (DDD) 110 in conjunction with a plating cell 101 such as an electrochemical plating (ECP) cell, an electroless plating cell, or other plating cell configuration. The plating cell 101 includes a fluid inlet 105 configured to deliver an electrolyte solution or plating processing fluid to the plating cell 101 and a fluid outlet or drain 106 configured to receive the electrolyte solution from the plating cell 101. The electrolyte solution enters the plating cell 101 via the inlet 105 that is in fluid communication with an electrolyte solution storage unit 102. A fluid pump 104 positioned between the storage unit 102 and the plating cell 101 circulates the electrolyte solution to the plating cell 101. The fluid outlet 106 of the plating cell 101 returns used electrolyte solution to the storage unit 102 through a fluid conduit 11 1. The fluid conduit 111 may include a slipstream, bypass, or diverter fluid conduit 112 attached thereto. The diverter fluid conduit 112 receives a portion of or the entire used electrolyte solution returned from the processing cell 101 to the storage unit 102 via the drain 106. The diffusion dialysis device 110 positioned along the diverter fluid conduit 112 includes an input for accepting the electrolyte solution flowing through the diverter fluid conduit 112 and an output coupled to a fluid conduit 113 for returning the electrolyte solution to the storage unit 102. In this manner, the electrolyte solution continually circulates through an electrolyte circulation loop.

During typical operational periods, the plating cell 101 may receive and/or circulate therethrough approximately 100 liters of electrolyte solution per hour. Thus, the DDD 110 receives any portion of this used electrolyte solution or the entire used electrolyte solution. As the used electrolyte solution passes through the DDD 110, the DDD 110 removes a portion of the organic additives, waste material from the organic additive breakdown, and acid from the used electrolyte solution to provide a refreshed electrolyte solution. The refreshed electrolyte solution is reintroduced into the fluid storage unit 102 for subsequent use in plating operations. The DDD 110 captures the extracted acids and waste material for disposal. In this manner, the DDD 110 operates to decrease or eliminate the frequency of replacement of the electrolyte solution by retaining copper ions within the electrolyte solution, removing organic additive breakdown waste material, and removing acid accumulated in the electrolyte solution. If needed, acid and additives may be reintroduced to the refreshed electrolyte solution in order to compensate for the loss of these components by the DDD 110.

FIG. 2 illustrates a schematic view of the DDD 110 shown in FIG. 1. The DDD 110 includes an outer housing 200 having a plurality of anionic membranes 206 that separate and define electrolyte cells 202 and diluted acid cells 204 within the DDD 110. The electrolyte cells 202 and the diluted acid cells 204 alternate across the DDD 110. Although only four electrolyte cells 202 and diluted acid cells 204 are shown, the DDD 110 may include any number of anionic membranes 206 that define any number of alternating electrolyte cells 202 and diluted acid cells 204. For example, embodiments of the DDD 110 may include between 3 and about 500 total number of electrolyte cells 202 and diluted acid cells 204. Configuration of the anionic membranes 206 within the housing 200 of the DDD 110 may include any known configuration for diffusion dialysis currently used for free acid recovery.

The anionic membranes 206 can be any type of anion-exchange membrane such as any one of many commercially available membranes. For example, Asahi Glass Company produces a wide range of polystyrene based ion-exchange membranes under the trade name Selemion such as anion membranes AMV, AMT, and AMD. Other companies manufacture similar ion-exchange membanes, such as Solvay (France), Sybron Chemical Inc. (USA), Ionics (USA), and FuMA-Tech (Germany) etc. Each anionic membrane 206 comprises a matrix having a positive charge inside and a selected porosity for selectively passing molecules therethrough. In one embodiment, the pore size of the anionic membrane is preferably greater than 50 angstroms and most preferably about 100 angstroms. Thus, the anionic membrane 206 permits water, hydrogen ion, disassociated sulfate ion, and organic additive penetration due to the negative or neutral charge and/or size of these molecules. However, disassociated copper ion penetration is negligible since the copper ions are repelled by the anionic membrane 206 having the same charge. The diffusion rate of the different organic additives through the anionic membranes 206 varies depending on the size and charge of the organic additives. For example, small and negative or neutral charged organic additives such as sulfur containing accelerators and brighteners penetrate through the anionic membrane 206 faster than the organic additives containing nitrogen such as levelers. Further, the polymeric structures of some organic additives such as suppressors substantially lack the ability to pass through the anionic membranes 206 due to their large sizes. Since the contamination material from the various organic additives is caused by their breakdown, the contamination material typically has a smaller chain length than the original organic additive. Thus, the smaller chain length of the contamination material permits the contamination material to penetrate through the anionic membranes 206.

In operation, the conduit 112 supplies used electrolyte solution from the plating cell 100 (shown in FIG. 1) to each of the electrolyte cells 202 through inlets 205 along the housing 200 of the DDD 110. In one embodiment, the inlets 205 are integral with the housing 200 such that the conduit 112 supplies used electrolyte solution to one location along the housing 200. The housing 200 includes individual frame chambers that sandwich the anionic membranes 206 between adjacent frame chambers. Passages through the walls of each frame chamber align with apertures in the anionic membranes 206 and passages in adjacent frame chambers to pass the used electrolyte solution across the length of the DDD 110. Ports connecting the interior of the frame chambers or the electrolyte cells 202 to the appropriate passages in the housing 200 provide the individual inlets 205. This design may be used for all of the inlets and outlets to the DDD 110 described herein.

As shown, the used electrolyte solution includes disassociated copper ions (Cu2+), hydrogen ions (H+), disassociated sulfate ions (SO42−), and organic additives and their breakdown products (Org). A diluted acid solution having a higher pH than the electrolyte solution circulates through the diluted acid cells 204. The diluted acid solution circulates through the DDD 110 by use of a supply tank 208, a pump 210, and fluid conduits connecting the supply tank 208 to inlets 201 and outlets 203 disposed in the housing 200 to provide flow through each of the diluted acid cells 204. SO42−, H+, and Org within the electrolyte cells 202 migrate across the anionic membranes 206 based on diffusion across the concentration gradient between the electrolyte cells 202 and the diluted acid cells 204. The diffusion of SO42−, H+, and Org from the electrolyte cells 202 to the diluted acid cells 204 effectively removes a portion of the acid and the organic additives from the electrolyte solution while leaving the Cu2+ min the electrolyte solution. The amount of the various organic additives (e.g. accelerator, leveler, and suppressor) extracted from the electrolyte solution depends on their diffusion rate through the anionic membranes 206. During operation, the electrolyte solution passes through the electrolyte cells 202 where a portion of the SO42−, H+, and Org is removed prior to the refreshed electrolyte solution exiting the electrolyte cells 202 through outlets 207 along the housing 200 of the DDD 110.

The supply tank 208, the conduits, the pump 210, and the diluted acid cells 204 provide a deionized (DI) water loop that circulates through the diluted acid cells 204 of the DDD 110. To maintain the concentration level of the acid circulating through DI water loop, the supply tank 208 refreshes by draining and discarding the diluted acid solution that contains acids and organic additives extracted from the electrolyte solution. Fresh deionized (DI) water adds to the supply tank to maintain the total volume of the diluted acid solution. In this manner, the concentration of acid within the supply tank 208 and diluted acid cells 204 remains sufficiently low to promote diffusion across the anionic membranes 206. Preferably, the supply tank 208 refreshes when the acid concentration therein reaches more than about 1 to 10 grams per liter.

FIG. 3 illustrates the plating system 100 of FIG. 1 incorporating the DDD 110 in conjunction with an electrodialysis cell (EDC) 103. The plating system 100 functions the same as described above except that the refreshed electrolyte solution that exits the DDD 110 first passes through the EDC prior to returning to the storage unit 102. The DDD 110 removes part of the organic additives and acid as described herein. Next, the EDC 103 completely removes the organic additives and returns the copper sulfate and the remaining acid to the storage tank 102 for reuse. In this manner, a combination of the DDD 110 and the EDC 103 removes a portion of the acid and all the organic additives. Since the DDD 110 substantially lacks the ability to remove some of the levelers and polymeric organic additives such as suppressors, the combination of the DDD 110 and EDC 103 provides for their removal from the electrolyte solution.

FIG. 4 shows a schematic view of the EDC 103 for use with the DDD 110 as illustrated in FIG. 3. The '569 application that is incorporated by reference and entitled “Apparatus and Method for Removing Contaminants from Semiconductor Copper Electroplating Baths” describes the use of the EDC for removal of waste material. The used electrolyte solution enters the EDC 103 via conduit 408 from the DDD 110. The conduit 408 supplies the used electrolyte into a plurality of depletion cells or chambers 405 in the EDC 103. While the used electrolyte is supplied to the depletion cells 405, a cathode 402 and an anode 403 apply an electrical bias across the EDC 103. The application of the electrical bias across the EDC 103 operates to urge ions in the used electrolyte solution towards the respective poles, i.e., positive ions urge in the direction of the cathode, while negative ions urge in the direction of the anode. Therefore, the Cu2+ along with the H+ urge in the direction of the cathode 402. Similarly, the SO42− urges in the direction of the anode 403. However, although the respective ions are urged in the direction of the respective poles, the linear distance the respective ions travel is limited by the positioning of anionic and cationic membranes 409, 410. More particularly, the positive copper and hydrogen ions in depletion cells 405 urge towards cathode 402 and pass into the neighboring concentration chambers 404 since the membranes separating depletion chambers 405 and concentration chambers 404 are cationic membranes 410. Similarly, the negatively charged sulfate ions urge towards the anode 403 and pass through the anionic membranes 409 into the neighboring concentration chambers 404. As a result of the alternating positioning of the cationic and anionic membranes 410, 409, positive copper ions and negative sulfate ions diffuse into concentration chambers 404 where these ions combine to form concentrated copper sulfate-sulfuric acid solution (CuSO4/H2SO4). The electrolyte solution waste material (organic breakdown products, impurities, solid particles, etc.) remain in depletion chambers 405 and are discarded via conduit 413. The concentrated copper sulfate within the concentration chambers 404 may then be removed via conduit 414 and returned to the storage unit 102 (shown in FIG. 3) for reuse.

FIG. 5 shows a schematic view of an alternative EDC 500 which may be used with the DDD 110 as illustrated in FIG. 3. Anionic membranes 509 used in the EDC 500 may not possess a sufficiently small porosity to completely prevent the passage of organics such as breakdown products from accelerator and leveler into the purified electrolyte. Unlike the configuration of the EDC 103 shown in FIG. 4, at least one cation membrane 510 separates the organic additives within depletion cells 505 from purified electrolyte cells 504 that contain the electrolyte for reuse. Therefore, the EDC 500 operates to provide a purified electrolyte solution based on the non-permeability of cation membranes 510 with respect to the organics such as accelerator and high-molecular weight leveler. A conduit 408 supplies the used electrolyte into a plurality of depletion cells 505 in the EDC 500. While the used electrolyte is supplied to the depletion cells 505, a cathode 502 and an anode 503 apply an electrical bias across the EDC 500 to urge ions in the used electrolyte solution towards the respective poles. Therefore, the Cu2+ along with the H+ urge in the direction of the cathode 502, and the SO42− urges in the direction of the anode 503. The positive copper and hydrogen ions in depletion cells 505 urge towards cathode 502 and pass into the neighboring purified electrolyte cells 504 since the membranes separating depletion cells 505 and purified electrolyte cells 504 are cationic membranes 510. The negatively charged sulfate ions and some of the organic additives and their breakdown products within the depletion cells 505 urge towards the anode 503 and pass through the anionic membrane 509 into a neighboring waste cell 507. Acid at a controlled concentration (e.g. 5-50 g/L) and supplied via conduit 508 circulates through acid cells 506 adjacent the purified electrolyte cells 504 and opposite the depletion cells 505. The sulfate ions within the acid cells 506 pass through the anionic membranes 509 separating the acid cells 506 and the purified electrolyte cells 504 in order to replenish the purified electrolyte. DI water may enter the waste cells 507 and the purified electrolyte cells 504 to aid flow through the EDC 500. The electrolyte solution waste material (organic breakdown products, impurities, solid particles, etc.) that remains in depletion cells 505 or is transferred to waste cells 507 is discarded via conduit 511. In this manner, the EDC 500 may return more than 95% of purified CuSO4/H2SO4 for reuse through conduit 414 to the storage unit 102 (shown in FIG. 3).

FIG. 6 illustrates an alternative plating system 500 that incorporates the DDD 110. The plating system 500 generally includes a plating cell 501 configured to fluidly isolate an anode 522 of the plating cell 501 from a cathode 523 or plating electrode of the plating cell 501 via a cation exchange membrane 512 positioned between the substrate being plated and the anode 522 of the plating cell 501. U.S. patent application Ser. No. 10/187,027, entitled “Electroplating Cell with Copper Acid Correction Module for Substrate Interconnect Formation,” which is herein incorporated by reference in its entirety, describes in detail a plating system using this type of divided plating cell. The plating cell 501 provides a first fluid solution (anolyte) to an anolyte compartment 508, i.e., the volume between the upper surface of the anode 522 and the lower surface of the membrane 512, and a second fluid solution (catholyte) to a catholyte compartment 510, i.e., the volume of fluid positioned above the upper membrane surface. The anode 522 may generally be soluble, e.g., a copper anode, or insoluble, e.g., platinum. The catholyte includes copper sulfate, sulfuric acid, copper chloride, and additives similar to the electrolyte solution described in FIG. 1. However, during electrolysis hydrogen ions and copper ions move through the membrane 512 into the catholyte compartment 510. As a result, the concentration of acid in the catholyte increases and must be removed. Therefore, the use of the DDD 110 as described herein effectively removes the build up of acid in the catholyte along with the build up of waste material from the breakdown of the organic additives.

FIG. 7 is a graph showing the rate of removal by the DDD 110 of sulfuric acid from an electrolyte solution. The electrolyte solution used to obtain the graph contained 0.85M CuSO4 and 0.3M H2SO4. In operation, one square meter of anionic membrane 206 within the DDD 110 extracts between about 20 and 60 grams of acid from the electrolyte solution per hour. The rate of acid extraction depends on the quality of the anionic membrane 206, flow rates through the DDD 110, and the concentration of acid accumulated in the DI water loop. As shown in the graph in FIG. 7, acid may need to be added to the electrolyte solution if insufficient acid is not produced during the plating process to compensate for the loss of acid.

FIG. 8 is a graph showing the rate of removal of organic additives and their breakdown products by the DDD from the electrolyte solution. The electrolyte solution contained 6.5 milliliters per liter of accelerator, 3 milliliters per liter of suppressor, and 4 milliliters per liter of leveler. As shown, the DDD 110 removes accelerator faster than leveler and leveler faster than suppressor. Therefore, the DDD 110 becomes most effective when the accumulation of accelerator's breakdown is faster than that of leveler's and negligibly low for suppressor. During typical plating processes, the breakdown products from accelerator accumulates faster than the breakdown products from leveler, and the breakdown products from suppressor accumulates negligibly within the electrolyte solution. Therefore, the DDD 110 extracts the various organic breakdown products at a rate that mirrors their rate of accumulation within the electrolyte solution.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.