US20050284751A1

US20050284751A1 - Electrochemical plating cell with a counter electrode in an isolated anolyte compartment

Info

Publication number: US20050284751A1
Application number: US10/880,103
Authority: US
Inventors: Nicolay Kovarsky; Anzhong Chang; Saravjeet Singh; You Wang; John Dukovic
Original assignee: Individual
Current assignee: Applied Materials Inc
Priority date: 2004-06-28
Filing date: 2004-06-28
Publication date: 2005-12-29
Also published as: TW200606283A; JP2008504444A; WO2006012112A3; KR101248179B1; WO2006012112A2; KR20070027753A

Abstract

A fluid processing cell for depositing a conductive layer onto a substrate is provided. The cell includes a catholyte solution fluid volume positioned to receive a substrate for plating, a first anolyte solution fluid volume at least partially ionically separated from the catholyte solution fluid volume, an anode assembly positioned in the first anolyte solution fluid volume, a second anolyte solution fluid volume, the second anolyte solution fluid volume being electrically isolated from the first anode solution fluid volume and at least partially in ionic communication with the cathode solution fluid volume, and a cathode counter electrode positioned in the second anolyte solution volume.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
Embodiments of the invention generally relate to an electrochemical plating cell.
2. Description of the Related Art
Metallization of sub 100 nanometer sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. However, metallization of sub 100 nanometer features presents several challenges to conventional metallization apparatuses and techniques. For example, conventional metallization techniques for integrated circuit applications generally include depositing a conductive seed layer onto surfaces that are to be metallized, and then electrochemically plating a conductive layer onto the seed layer to metallize and fill the features. The seed layer is often deposited by a physical vapor deposition (PVD) process and generally has a thickness of between about 300 Å and about 700 Å. However, seed layer deposition becomes increasingly difficult with sub 100 nanometer features, as the opening at the top of the features tends to close off from field or horizontal surface deposition before the sidewalls or vertical surfaces of the features are adequately metallized by the seed layer. This closure of the opening of the feature inhibits subsequent processes from metallizing or filling the main body of the feature with the desired conductive material.
Deposition of the thin seed layer required for sub 100 nanometer features also presents challenges with respect to the continuity or resistance of the thin seed layer. More particularly, since the thickness of the conductive seed layer is directly proportional to the resistance of the layer, the decreasing thicknesses of seed layers in sub 100 nanometer features results in a substantially higher seed layer resistance. This increased resistance is known to cause an edge high plating condition, i.e., thicker plating near the edge of the substrate as a result of the decreased electric field near the center of the substrate from the high seed layer resistance.
Another challenge in metallization of sub 100 nanometer features is the metallization or feature filling process that is conducted after the seed layer is deposited. Metallization of integrated circuit devices is generally conducted with an electrochemical plating process, however, the small size of the feature opening and high aspect ratio of the feature body makes it very difficult to obtain continuous bottom up fill of the main body of the feature without closing the opening of the feature and preventing subsequent plating in the feature, thus generating an unfilled void or pocket in the feature.
Therefore, there is a need for an apparatus and method for metallizing sub 100 nanometer integrated circuit devices and minimizing edge high plating effects that result from thin seed layers.

SUMMARY OF THE INVENTION

Embodiments of the invention provide an electrochemical plating cell configured to metallize sub 100 nanometer features on integrated circuit devices. The plating cell includes a fluid basin having an anolyte solution compartment and a catholyte solution compartment, an ionic membrane positioned between the anolyte solution compartment and the catholyte solution compartment, an anode positioned in the anolyte solution compartment, and a cathode electrode positioned to electrically contact and support a substrate for processing in the fluid basin. The anolyte compartment is divided into a first and second anolyte compartments, such that the anode is positioned in the first compartment and a counter electrode is positioned in the second compartment. The first and second compartments both have an anolyte fluid flow therethrough, however, the first and second compartments are electrically isolated from each other.
Embodiments of the invention may further provide an electrochemical plating cell having a fluid container having an ionic membrane positioned across the fluid container, the ionic membrane being positioned to fluidly separate a catholyte volume from a first anolyte volume in the fluid container. The plating cell further includes an anode assembly positioned in fluid communication with the first anolyte volume, a cathode substrate support member positioned to support a substrate at least partially in the catholyte volume for a plating process, a counter electrode positioned in fluid communication with a second anolyte volume, the second anolyte volume being electrically isolated from the first anolyte volume, and a vent member positioned in fluid communication with the catholyte volume, the vent member being in ionic communication with the second anolyte volume.
Embodiments of the invention may further provide a fluid processing cell for depositing a conductive layer onto a substrate. The cell generally includes a catholyte solution fluid volume positioned to receive a substrate for plating, a first anolyte solution fluid volume at least partially ionically separated from the catholyte solution fluid volume, an anode assembly positioned in the first anolyte solution fluid volume, a second anolyte solution fluid volume, the second anolyte solution fluid volume being electrically isolated from the first anode solution fluid volume and at least partially in ionic communication with the cathode solution fluid volume, and a cathode counter electrode positioned in the second anolyte solution volume.
Embodiments of the invention may further provide an electrochemical plating cell having a fluid basin having an ionic membrane positioned across a middle portion of the basin, the ionic membrane separating the fluid basin into an upper catholyte volume and a lower anolyte volume, an anode assembly positioned in the lower anolyte volume, and a cathode substrate support member removably positioned in the catholyte volume. The plating cell further includes a counter electrode positioned in an isolated anolyte volume, the isolated anolyte volume being positioned below the ionic membrane and not in direct electrical communication with the lower anolyte volume, and a counter electrode vent positioned in an upper portion of the fluid basin at a position proximate an edge of a substrate being plated in the fluid basin, the counter electrode vent being in electrical communication with the counter electrode via a fluid conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present 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 a sectional view of an exemplary electrochemical plating cell and head assembly of the invention.
FIG. 2A illustrates a schematic sectional view of an exemplary electrode and membrane configuration of the invention.
FIG. 2B illustrates a horizontal section of the exemplary plating cell showing the anolyte fluid flow patterns.
FIG. 3 illustrates another sectional view of the plating cell of the invention.
FIG. 4 illustrates a detailed sectional view of the fluid delivery conduits of the plating cell of the invention.
FIG. 5 illustrates a detailed sectional view of the fluid return conduits of the plating cell of the invention.
FIG. 6 illustrates a sectional view of the plating cell of the invention and representative electrical flux lines that are generated during plating operations.
FIGS. 7 a-7 e illustrate exemplary anode configurations that may be used in the plating cell of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is directed to a plating cell configured to support metallization processes for sub 100 nanometer integrated circuits. The plating cell generally includes a partitioned fluid basin, i.e., the fluid volume in the plating cell fluid basin is separated into a catholyte solution volume and an anolyte solution volume. An example of this type of separation of a plating cell into an anolyte volume and a catholyte volume may be found in commonly assigned U.S. patent application Ser. No. 10/627,336, filed Jul. 24, 2003 entitled “Electrochemical Processing Cell”, which is hereby incorporated by reference in its entirety. The anolyte volume of the plating cell includes at least one anode electrode and at least one counter electrode, however, the counter electrode is positioned and configured to be electrically isolated from the anode electrode.
FIG. 1 illustrates a simplified sectional view of an exemplary plating cell 100 and head assembly 102 of the invention in a processing position. FIG. 3 illustrates another sectional view of plating cell 100 of the invention without the head assembly 102. Plating cell 100 includes a head assembly 102 configured to support a substrate for plating operations in a plating cell fluid basin 108. The head assembly 102 generally includes a thrust plate member 104 and a cathode contact ring member 106. Thrust plate 104 and contact ring 106, which will be further discussed herein, are generally configured to support and electrically bias a substrate for electrochemical processing in plating cell 100. Fluid basin 108 is configured to confine an inner fluid volume 110 and to receive a substrate for plating in the fluid volume 110. Fluid basin 108 also includes an overflow weir 109 (a contiguous uppermost fluid overflow point) that spills into an outer collection volume 112 that circumscribes weir 109. Collection volume 112 operates to drain overflow plating solution from the inner volume 110 such that the plating solution may be recirculated back to inner volume 110. Fluid basin 108 optionally includes a fluid diffusion member 114 positioned across the inner volume 110 at a position below where the substrate 118 being plated is positioned. The fluid diffusion member 114 generally operates to dampen fluid flow variations in the direction of the substrate 118, as well as operating to provide a resistive element in the plating bath between the anode and the substrate. A more thorough description of the diffusion member and other plating cell components and operational characteristics may be found in commonly assigned U.S. Pat. No. 6,261,433 and commonly assigned U.S. Pat. No. 6,585,876, both of which are hereby incorporated by reference in their entireties.
Fluid basin 108 further includes a membrane 116 positioned across the fluid basin 108 at a position below where the diffusion member 114 may be positioned, if used. Membrane 116 is generally an ionic membrane, and more particularly, a cationic membrane, that is generally configured to prevent fluid passage therethrough, while allowing ions, such as copper ions, to travel through the membrane 116 toward substrate 118. As such, membrane 116 generally operates to separate a catholyte volume 119 of the plating cell 100 from an anolyte volume 120 of the plating cell 100, wherein the catholyte volume 119 is generally defined as the fluid volume between the membrane 116 and the substrate 118, and the anolyte volume 120 is defined as the fluid volume below the membrane 116 adjacent the anode. A more thorough description of the membrane 116 and the separation of the anolyte from the catholyte may be found in commonly assigned U.S. patent application Ser. No. 10/627,336, filed Jul. 24, 2003 entitled “Electrochemical Processing Cell”, which is hereby incorporated by reference in its entirety.
The anolyte volume 120 generally contains an anode assembly 122 that includes at least one electrically conductive member positioned in contact with the anolyte solution flowing through the anolyte volume 120. The conductive member may be manufactured from a soluble material, such as copper, or from an insoluble material, such as platinum or another noble metal, etc. A counter electrode assembly 124, which is generally positioned radially outward of the perimeter of anode assembly 122, may also be manufactured from either a soluble or an insoluble material, such as copper, platinum, etc.
Although anode assembly 122 and the counter electrode 124 are generally positioned such that both assemblies 122, 124 are in communication with an anolyte solution, the respective assemblies 122, 124 are also positioned and configured such that the anode assembly 122 is electrically isolated from the counter electrode 124. More particularly, an electrically insulating spacer 126 is generally positioned between anode assembly 122 and counter electrode 124. Further, the anolyte solution fluid flow that is in fluid contact with the anode assembly 122 is not the same anolyte fluid flow that is in fluid contact with the counter electrode 124, as will be further discussed herein with respect to FIG. 4. Anode assembly 122 is in electrical communication with an anodic terminal of a power supply (not shown). The cathodic terminal of the same power supply is generally in electrical communication with the contact ring 106, which is configured to electrically contact the substrate 118 and the counter electrode 124. However, although only one power supply is discussed herein with respect to supplying the cathodic bias, it is understood that more than one independently controlled power supply may be used without departing from the scope of the invention.
A plating solution, also termed a catholyte, is supplied to the catholyte volume 119 by a fluid supply conduits 133 a, 133 b which is in fluid communication with a catholyte solution tank (not shown). The catholyte solution generally includes several constituents, including, for example, water, copper sulfate, halide ions, and one or more of a plurality plating additives (levelers, suppressors, accelerators, etc.). The catholyte solution supplied by conduits 133 a, 133 b overflows the weir 109 and is collected by collection volume 112. The anolyte solution is supplied to anolyte volume 120 by an anolyte supply conduit 131 a and drained from anolyte volume 120 by an anolyte drain conduit 131 b positioned on an opposing side from the supply conduit 131 a. The positioning of the supply and drain conduits 131 a, 131 b generates directional flow of the anolyte across the upper surface of the anode 122, as described in commonly assigned U.S. patent application Ser. No. 10/268,284, filed Oct. 9, 2002 entitled “Electrochemical Processing Cell”, which is hereby incorporated by reference in its entirety.
Plating cell 100 also includes a second anolyte fluid inlet 132 a and a second anolyte fluid drain 132 b. The second anolyte fluid inlet 132 a is configured to supply an anolyte solution to the volume 135 surrounding the counter electrode 124, while not fluidly or electrically communicating with the main anolyte volume 120 contained in the volume adjacent the anode 122 and supplied by conduits 131 a, 131 b as illustrated in FIG. 2 a. Volume 135 is fluidly bound by membrane 116 on the upper side thereof. The fluid boundary is generally a result of the lack of fluid permeability of membrane 116, combined with positioning two seals 136 adjacent electrode 124, and more particularly, between the partition 126 and membrane 116, and between the cell body portion 127 outward of electrode 124 and membrane 116. The positioning of the two seals 136, which may generally be circular o-ring-type seals, operates to channel the flow of anolyte supplied by conduit 132 a around volume 135 to drain conduit 132 b. As such, the anolyte supplied by conduit 132 a generally flows through the volume 135 above the counter electrode 124 in a semicircular pattern, as illustrated by arrows “A” in FIG. 2 b. As such, the anolyte fluid circulated through the volume 135 is collected by the second anolyte drain conduit 132 b on the opposing side of the cell from which the anolyte was supplied by conduit 131 a. Alternatively, the anolyte supplied to the anolyte compartment 120 generally flows directly across the anode 122, as illustrated by arrows “B” in FIG. 2 b, and is collected by conduit 131 b. The fluid flows indicated by arrows “A” and “B” both occur below the membrane 116. Flow “A” occurs between seals 136, and flow “B” occurs across the top of the anode 122 radially inward of the inner seal 136.
Although the membrane 116 provides a fluid barrier that prevents the anolyte solution from fluidly transferring therethrough, membrane 116 allows for ionic transfer, and more particularly, for positive ionic transfer. As such, although the anolyte cannot permeate membrane 116, ions such as copper and hydrogen ions may transfer through the membrane 116 into vent conduit 140, which contains catholyte. Thus, the combination of the volume 135 above the electrode 124 and the catholyte in vent conduit 140 generates an electrical path for current to travel from the cathode contact ring (the substrate) 106 to the counter electrode 124.
FIG. 2 a illustrates the flux lines generated near the anode 122 and the counter electrode 124 during a plating process. The electrical flux immediately above the anode 122 is represented by the arrows labeled “C”. The flux above the anode 122 may be controlled by applying a different electrical power to the respective anode segments 122 a, 122 b, and 122 c. Anode segments 122 a, 122 b, 122 c may be concentric, symmetric, or any other configuration depending upon the desired flux. FIGS. 7 a-7 e illustrate exemplary anode configurations that may be used in embodiments of the invention, wherein the anode segments 1, 2, and 3 are denoted. It is understood that each of segments 1, 2, and 3 of the respective anode arrangements may be individually powered to control and/or optimize plating parameters. Returning to FIG. 2 a, the anode segments 122 a, 122 b, 122 c may also be individually powered and are not limited to any particular number, i.e., there may be between 1 and about 10 or more anode segments in a plating cell. With regard to independently powering anode segments, anode segment 122 a illustrated in FIG. 2 a has more power applied thereto than anode segment 122 b. This is evident from the density of the flux lines “C” originating from segment 122 a is greater than those originating from anode segment 122 b, thus indicating the less power is being applied to segment 122 b.
FIG. 4 illustrates an enlarged sectional view of the electrode and membrane configuration of the plating cell of FIGS. 1 and 3 on the fluid supply side of the plating cell. More particularly, arrows “F” indicate the anolyte fluid flow path for the anolyte solution that is flowing over the upper surface of anode 122. The anolyte fluid flow indicated by arrows “F” is generally supplied to conduit 131 a and directed to flow across the upper surface of anode 122 in the flow direction generally indicated by arrows “B” in FIG. 2 b. This fluid flow is generally perpendicular to any slots or elongated apertures formed into anode 122 for the purpose of receiving anode sludge or other dense fluids that may form on the anode surface during plating operations.
Arrows “G” in FIG. 4 indicate the anolyte ion flow path for the anolyte solution that is flowing over the counter electrode 124, which also generally corresponds with the fluid flow indicated by arrows “A” in FIG. 2 b. As such, the anolyte ion flow “G” is generally supplied to volume 135 by conduit 132 a, which generates a semicircular flow of fluid over the top of the counter electrode 124, below membrane 116, and between seals 136.
Arrows “E” indicate the fluid flow path for the catholyte solution that is supplied to the catholyte volume 119 of plating cell 100. The catholyte solution flows upward through conduit 132 a, then generally horizontally across at least a portion of the upper surface of membrane 116, and then upward to an opening, i.e., vent conduit 140, that communicates with the catholyte region 119. The flow of the catholyte over the upper surface of the membrane is generally configured to be at a position that overlaps the volume 135 above the counter electrode 124, which provides a current path between the catholyte and the counter electrode 124 via transmission through membrane 116. This current path generally travels from the cathode contact ring 106 through vent 140 via the catholyte solution residing therein, through membrane 116, and through the anolyte residing in volume 135 to the counter electrode 124, as indicated by arrows “H” in FIG. 6.
FIG. 5 illustrates an enlarged sectional view of the electrode and membrane configuration of the plating cell of FIGS. 1 and 3 on the fluid drain side of the plating cell. Arrows “J” illustrate the flow direction for the anolyte being removed from the anode chamber 120 adjacent the anode 122. The anolyte drain conduit 131 b is positioned to drain anolyte from the anode chamber 120 in a direction that is generally perpendicular to slots formed in the anode 122, as illustrated by arrows “B” in FIG. 2 b. Arrows “K” illustrate the flow direction of the anolyte solution over the counter electrode 124. The anolyte flowing over counter electrode 124 is removed from the volume 135 above the electrode 124 at a point that facilitates the semicircular flow pattern illustrated by arrows “A” in FIG. 2 b. Arrows “L” illustrate the catholyte flow direction for the catholyte traveling through supply conduits 131 a, 131 b to supply fresh catholyte to the catholyte chamber 119. Arrows “M” illustrate the flow direction of the anolyte being drained from volume 135 above the counter electrode 124.
In operation, counter electrode 124 is used in combination with anode member 122, which may be one of the segmented anodes illustrated in FIGS. 7 a-7 e or variations thereof, to control the electrical flux across the surface of the substrate 118 being plated. More particularly, counter electrode 124, which is also in electrical communication with a power supply (not shown) is used to selectively reduce the electric flux near the edge of the substrate 118 to prevent edge high plating. Counter electrode 124 reduces the electric flux near the edge of the substrate by supplying an additional cathodic flux source to the area proximate the edge or perimeter of the substrate 118. Counter electrode 124 supplies the additional flux, which is illustrated by arrows “H” in FIG. 6, to the area proximate the edge or perimeter of the substrate by electrically communicating with the cathode volume 119 via vent 140. Vent 140, which is generally an annular vent that circumscribes the perimeter of the substrate, is positioned to conduct flux from the counter electrode 124 to the catholyte volume 119 in a manner that reduces the quantity of flux generated by the substrate/cathode near the perimeter of the substrate. More particularly, the combination of vent 140 and counter electrode 124 being cathodically biased essentially operates to flood the perimeter of the substrate with a flux source, which prevents the anode from conducting flux directly to the perimeter edge of the substrate where vent 140 is supplying flux. As such, the electrical flux originating on the substrate 118 is increased near the center of the substrate 118, as illustrated by arrows “C” in FIG. 6, while reducing the electrical flux at the substrate surface near the perimeter of the substrate 118, as the flux represented by arrows “H” has essentially displaced the flux originating near the perimeter of the substrate 118.
This reduction in the flux near the perimeter of the substrate, which may be controlled by the cathodic bias applied to the counter electrode 124, generally operates to reduce edge or perimeter high plating characteristics of conventional plating cells. More particularly, the counter electrode 124 operates as a cathodic source near the edge of the substrate 118 via the flux traveling from counter electrode 124 through vent 140 to the anode assembly 122, and therefore, reduces the flux near the edge of the substrate. This reduced flux has been shown to reduce the plating near the perimeter of the substrate.
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, wherein the scope is determined by the claims that follow.

Claims

1. An electrochemical plating cell, comprising:

a fluid container having an ionic membrane positioned across the fluid container, the ionic membrane being positioned to fluidly separate a catholyte volume from a first anolyte volume in the fluid container;

an anode assembly positioned in fluid communication with the first anolyte volume;

a cathode substrate support member positioned to support a substrate at least partially in the catholyte volume for a plating process;

a counter electrode positioned in fluid communication with a second anolyte volume, the second anolyte volume being electrically separated from the first anolyte volume; and

a vent conduit positioned in fluid communication with the catholyte volume, the vent conduit being in ionic communication with the second anolyte volume.

2. The plating cell of claim 1, wherein the first anolyte volume is electrically isolated from the second anolyte volume by an electrically insulating partition.

3. The plating cell of claim 1, wherein the vent conduit further comprises an annular vent nozzle formed into the fluid container at a position adjacent a perimeter of the substrate during the plating process.

4. The plating cell of claim 3, wherein the vent conduit containing electrolyte solution is in electrical communication with the counter electrode.

5. The plating cell of claim 4, wherein the vent conduit extends across the ionic membrane.

6. The plating cell of claim 5, wherein the second anolyte volume is positioned in communication with a lower surface of the ionic membrane adjacent the vent conduit.

7. The plating cell of claim 5, further comprising:

a catholyte supply conduit in fluid communication with the catholyte volume and the vent conduit;

a first anolyte supply conduit in fluid communication with the first anolyte volume;

a first anolyte drain conduit in fluid communication with the first anolyte volume;

a second anolyte supply conduit in fluid communication with the second anolyte volume; and

a second anolyte drain conduit in fluid communication with the second anolyte volume.

8. The plating cell of claim 5, wherein the vent conduit is configured to supply cathodic electrical flux to an area proximate the perimeter of the substrate during a plating process.

9. The plating cell of claim 1, wherein the counter electrode is in electrical communication with a cathodic terminal of a power supply.

10. The plating cell of claim 1, wherein the membrane comprises a cationic membrane.

11. The plating cell of claim 1, wherein the counter electrode comprises an annular conductive member.

12. A fluid processing cell for depositing a conductive layer onto a substrate, comprising:

a catholyte solution fluid volume positioned to receive a substrate for plating;

a first anolyte solution fluid volume at least partially ionically separated from the catholyte solution fluid volume;

an anode assembly positioned in the first anolyte solution fluid volume;

a second anolyte solution fluid volume, the second anolyte solution fluid volume being electrically isolated from the first anode solution fluid volume and at least partially in ionic communication with the cathode solution fluid volume; and

a cathode counter electrode positioned in the second anolyte solution volume.

13. The fluid processing cell of claim 12, further comprising a cathode electrode vent positioned in an upper portion of a basin containing the catholyte solution fluid volume, the cathode electrode vent being configured to electrically connect the cathode counter electrode and catholyte solution fluid volume.

14. The fluid processing cell of claim 12, further comprising an ionic membrane positioned between the cathode solution fluid volume and the first anode solution fluid volume and between the cathode solution fluid volume and the second anode solution fluid volume.

15. The fluid processing cell of claim 13, wherein the cathode electrode vent comprises an annular opening in a wall defining the cathode solution fluid volume, the annular opening being configured to conduct electrical flux from the cathode counter electrode to the anode.

16. The fluid processing cell of claim 15, wherein the annular opening is positioned adjacent a perimeter of the substrate being processed and is configured to minimize electrical flux near the perimeter of the substrate.

17. The fluid processing cell of claim 12, wherein the anode assembly comprises a plurality of anode segments.

18. The fluid processing cell of claim 12, wherein the cathode counter electrode is in electrical communication with a cathode terminal of a power supply.

19. The fluid processing cell of claim 18, wherein the cathode terminal of the power supply is in electrical communication with the substrate and where the anode terminal of the power supply is in electrical communication with the anode assembly.

20. An electrochemical plating cell, comprising:

a fluid basin having an ionic membrane positioned across a middle portion of the basin, the ionic membrane separating the fluid basin into an upper catholyte volume and a lower anolyte volume;

an anode assembly positioned in the lower anolyte volume;

a cathode substrate support member removably positioned in the catholyte volume;

a counter electrode positioned in an isolated anolyte volume, the isolated anolyte volume being positioned below the ionic membrane and not in direct electrical communication with the lower anolyte volume; and

a counter electrode vent positioned in an upper portion of the fluid basin at a position proximate an edge of a substrate being plated in the fluid basin, the counter electrode vent being in electrical communication with the counter electrode via a fluid conduit.

21. The electrochemical plating cell of claim 20, further comprising a power supply having a cathodic terminal in electrical communication with a substrate support member and the counter electrode, and an anodic terminal in electrical communication with the anode assembly.

22. The electrochemical plating cell of claim 20, wherein the fluid conduit communicates with an upper surface of the membrane that opposes the counter electrode.