Abstract:
In one embodiment, the present invention generally provides an apparatus and method for dispersing a chemical reagent into a plating solution. The apparatus generally includes a tank for containing the plating solution and a horizontal vessel in fluid communication with the tank, wherein the horizontal vessel has an input and an output. The apparatus further includes at least one shelf contained inside the horizontal vessel, wherein the at least one shelf extends between the input and the output and the chemical reagent rests on the at least one shelf. In another embodiment, the present invention generally provides an apparatus for dispersing a chemical reagent to a plating solution comprising a tank for containing the plating solution and a vertical vessel in fluid communication with the tank. A lower portion of the vertical vessel includes an inlet and an injector port and an upper portion of the vertical vessel includes an outlet and a manifold. The chemical reagent is positioned between the inlet and the outlet.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Embodiments of the invention generally relate to a metal plating apparatus and process, namely for the replenishment of chemical components used to electroplate copper.  
         [0003]     2. Description of the Related Art  
         [0004]     Semiconductor substrates can be plated with copper by electroplating or electroless plating processes. During the electroplating, an anode is usually placed into an electrolyte solution and the substrate is conductively coupled to a cathode. As current flows, dissolved copper ions from the electrolyte solution are reduced and plated (or deposited) on the surface of the substrate as copper metal. Traditionally, the anode is made from consumable copper metal and is continuously oxidized to provide copper ions to the plating process. Due to the consumption of the copper anode, the dimension of the copper anode is changed. Therefore the directional electrical fields produced by the anode also change accordingly. This alteration in the electric field presents a challenge to precisely control the electroplating process, especially within vias with high aspect ratios.  
         [0005]     Another electroplating process utilizes an inert or stable anode in place of a consumable anode. The use of an inert anode provides excellent control for precision plating since the anode is not consumed during the plating process. However, the inert anode does not supply a source of copper into the electrolyte solution. As the copper ions are reduced and plated from the electrolyte solution to the substrate surface, the copper ion concentration in the electrolyte solution is diminished. Therefore, as the plating process progresses, a copper source, namely copper ions, must be added to the electrolyte solution in order to continue the plating process. Copper sources are generally chosen from a variety of copper salts that include copper sulfate, copper hydroxide, copper oxide and copper phosphate.  
         [0006]     U.S. Pat. No. 5,516,414 teaches a method to maintain an alkaline copper plating solution with a desired concentration of copper ions and hydroxide ions. The &#39;414 patent discloses adding copper hydroxide powder from a conduit to an alkaline, pyrophosphate solution in a dissolving tank. Once the solution has been heated and agitated to insure that the copper hydroxide has been dissolved, the pyrophosphate solution is transferred via a pump to the plating solution. The plating solution is monitored with a meter and maintained with a basic pH between 7 and 10 by adding the alkaline, pyrophosphate solution. Though the addition of copper hydroxide powder is adequate in the realm of electroplating wires, this technique is unacceptable in a clean environment, such as a semiconductor fabrication room equipped to plate substrates. The dumping of a powdery precursor into a solution would present contamination issues for semiconductor processing in a cleanroom environment.  
         [0007]     U.S. Pat. No. 5,997,712 realizes the shortcomings of the &#39;414 patent as applied to a cleanroom. The &#39;712 patent avoids dumping the powdery precursor and teaches a method to replenish copper ions in a plating solution with the apparatus depicted in  FIG. 1A . The anolyte flows from the top of canister  2 , through a porous cartridge  4  and into a hollow cavity  6  before flowing out the bottom of canister  2 . The cartridge  4  includes a filter element that encompasses the powdery copper source. Therefore, the anolyte flows through the canister  2  and is enriched by copper ions via absorbing the copper source.  
         [0008]     However, as illustrated in  FIG. 1B , the anolyte can flow into cartridge  4  and form different phases of anolyte/copper source. The depleted anolyte  8  enters the cartridge  4  from above and flows downwardly to form a suspension  9  of anolyte/copper source. As the suspension  9  flows towards the bottom of the cartridge  4 , the suspension densifies, forming a viscous cake  10  at the bottom of the cartridge  4 . Throughout the formation of cake  10 , the flow of anolyte lessens and copper ions cease to be consistently replenished in the anolyte. Therefore, longer plate times reduce substrate throughput with this decrease of the copper concentration. Also, in the case when copper hydroxide is used as a copper source, the reduction in the hydroxyl ion addition lowers the pH of the anolyte.  
         [0009]     Therefore, there is a need for an apparatus and method to replenish chemical compounds within an electrolyte solution in a consistent and reliable manner.  
       SUMMARY OF THE INVENTION  
       [0010]     In one embodiment, the invention generally provides an apparatus for dispersing chemical reagents to a plating solution including a tank for containing the plating solution and a cartridge in fluid communication with the tank, wherein the cartridge has an input and an output. The apparatus further includes at least one shelf contained inside the cartridge. The at least one shelf may be impermeable and may extend between the input and the output such that the chemical reagent rests on the at least one shelf.  
         [0011]     In another embodiment, the invention generally provides an apparatus for dispersing a chemical reagent to a plating solution comprising a tank for containing the plating solution and a vertical cartridge in fluid communication with the tank. A lower portion of the vertical cartridge includes an inlet and an injector port and an upper portion of the vertical cartridge includes an outlet and a manifold. The chemical reagent is positioned between the inlet and the outlet.  
         [0012]     In another embodiment, the invention generally provides a method for dispersing a chemical reagent to a plating solution including flowing the plating solution from a tank through an input of a cartridge, wherein the cartridge comprises a chemical reagent disposed on at least one shelf. The plating solution flows across the chemical reagent to enrich the plating solution with the chemical reagent, whereas the chemical agent is dissolved or suspended within the plating solution. The enriched plating solution flows from the cartridge through an output to the tank.  
         [0013]     In another embodiment, the invention generally provides a method for monitoring and controlling a pH setting of a plating solution in a tank including determining a pH of the plating solution with a pH meter, transferring an aliquot of the plating solution to a vessel and pressurizing the vessel with a gas to transfer the aliquot to a cartridge. The cartridge includes an injector, a chemical reagent and a manifold. The aliquot passes through the injector, which enriches the aliquot with a portion of the chemical reagent and the enriched aliquot transfers through the manifold to the plating solution in the tank. A second pH of the plating solution is determined with the pH meter and compared with the pH setting. Enriched aliquots are transferred repeatedly to the plating solution until the second pH is equivalent to the pH setting. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     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.  
         [0015]     FIGS.  1 A-B show a cartridge inside a canister as used in the related art;  
         [0016]      FIG. 2  shows a flow diagram for a two-sectional electrochemical cell with catolyte and anolyte;  
         [0017]      FIG. 3  shows a longitude sectional view of a cartridge with horizontal shelves;  
         [0018]     FIGS.  4 A-C show cross-sectional views of cartridges with a variety of shelves;  
         [0019]     FIGS.  5 A-C show cartridge placements into an anolyte loop;  
         [0020]      FIG. 6A  shows a vertical sectional view of a cartridge with a bottom injector;  
         [0021]      FIG. 6B  shows a fragmentary vertical sectional view of a portion of the embodiment of  FIG. 6A ;  
         [0022]      FIG. 7  shows a schematic diagram of a plating system incorporating one embodiment of a cartridge with a bottom injector;  
         [0023]      FIG. 8  is a diagram illustrating the timing sequence of valve operation during a plating process;  
         [0024]      FIG. 9  shows another embodiment of a cartridge with a bottom injector incorporated into a plating system; and  
         [0025]     FIGS.  10 A-B show embodiments of injector systems including rotatable cups. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]     The present invention comprises apparatuses and methods to replenish chemical compounds in plating solutions in a consistent and reliable manner. The present invention overcomes the shortcomings of the related art as described in the background and illustrated in  FIG. 1 , mainly, by not blocking anolyte flow with cake formations. Therefore, by utilizing the various embodiments of the apparatuses and methods of the present invention, each substrate experiences more consistent plating times and anolyte chemical concentrations.  
         [0027]     Embodiments of the present invention are useful in a variety of plating systems, including electroplating and electroless plating systems. Further, various embodiments are also applicable to electroplating with soluble anodes and with insoluble anodes.  FIG. 2  shows a schematic arrangement of an electroplating system with a cell  11  containing an insoluble anode  12 . The insoluble anode  12  is made from relatively inert materials, such as platinum, titanium, titanium with a Pt-coating, palladium, nickel, stainless steel and/or carbon. The material of the insoluble anode  12  is generally configured to withstand the various process conditions involved while plating to a wafer or substrate  14 . Process conditions may have acidic or basic pH, oxidative/reductive potentials and an assortment of chemical compounds throughout the solution. In one embodiment, the insoluble anode  12  endures process conditions such as acidic plating solutions and an oxidative potential. The substrate  14  is attached to the cathode  13 , usually by a contact ring, pins, and the like (not pictured).  
         [0028]     The insoluble anode  12  and the cathode  13  are separated by a membrane  16  extending through cell  11 . The membrane  16  is an electroconductive membrane, such as an ion-exchange membrane, nano-filtration membrane, ultra-filtration membrane and others known in the art. The portion of the cell  11  containing the cathode  13  is in fluid communication with the catolyte tank  17  to recirculate the catolyte within. The catolyte is a mixture of compounds that may include, for copper plating, sulfuric copper plating electrolyte or pyrophosphoric copper plating electrolyte. A sulfuric copper plating electrolyte will generally include a mixture of copper sulfate, sulfuric acid and various organic and inorganic additives including suppressors, accelerators, levelers and brighteners. Catolyte may pass through a diffuser  15  and be more evenly distributed while flowing to the substrate  14 .  
         [0029]     The portion of the cell  11  containing the insoluble anode  12  is in fluid communication with the anolyte tank  18  and recirculates the anolyte within. For copper plating, the anolyte is a solution containing copper ions, often derived from dissolved copper salts, such as copper sulfate. Other copper ion sources include copper hydroxide, copper carbonate, copper oxide and copper phosphate.  
         [0030]     Under copper plating electrolysis, the half reaction in scheme (i) occurs on the insoluble anode  12 : 
 
H 2 O→2H + +2e − +½O 2(g) ,   (i) 
 
 while Cu 2+  ions migrate through the membrane  16  from the anolyte to the catolyte and are reduced according to the half reaction shown in scheme (ii): 
 
Cu 2+ +(SO 4 ) 2− +2e−→Cu 0 +(SO 4 ) 2− .   (ii) 
 
 The combined half reactions are represented in reaction scheme (iii): 
 
CuSO 4 +H 2 O→Cu 0 +H 2 SO 4 +½O 2(g)    (iii) 
 
 Therefore, as the electroplating process proceeds, the anolyte becomes depleted of copper ions due to the precipitation of metallic copper as well as more acidic due to the production of sulfuric acid. Also, water is consumed making the electrolyte more concentrated. 
 
         [0031]     The sulfuric acid formed in the anolyte penetrates through the membrane  16  and contaminates the catolyte. The sulfuric acid lowers the pH of the catolyte. More acidic catolyte is not desirable because the membrane loses ion selectivity between protons and copper ions. The lost of the membrane selectivity permits protons to compete with copper ions while penetrating the membrane, therefore, unbalancing the catolyte chemical concentration. To prevent the lowering of the pH of the catolyte, an alkaline compound is added. Copper hydroxide consists of a copper ion source as well as a hydroxyl source and will neutralize formed sulfuric acid, as shown by the reaction scheme (iv): 
 
Cu 2+ +2(OH) − +H 2 SO 4 →CuSO 4 +2H 2 O.   (iv) 
 
 Therefore, schemes (iii) and (iv) are combined and the proportional amount of copper hydroxide is added to the anolyte. The summed reaction is depicted in scheme (v), namely copper is consistently deposited while water and oxygen are formed as byproducts, such as: 
 
Cu(OH) 2 →Cu 0 +H 2 O+½O 2(g) .   (v) 
 
         [0032]      FIG. 3  shows a longitudinal sectional view of an embodiment of a cartridge system  20  including a cartridge  22  containing one embodiment of shelves  24  of the invention. The shelves  24  are vertically spaced apart and extend longitudinally between input  32  and output  34 . The shelves  24  may number in a range from about 1 to about 50, though preferably from about 2 to about 10.  FIGS. 3 and 4 A illustrate four horizontal substantially flat top shelves. The cartridge  22  and the shelves  24  may be made from an assortment of materials, such as plastics or metals, including stainless steel, aluminum, titanium, nickel-coated steel and various alloys, amongst others.  
         [0033]     Chemical reagents  26  are distributed across each of the shelves  24 . The chemical reagents are exposed to plating solution  28  (depicted with arrows) flowing through the cartridge  22 . The plating solution  28  enters the cartridge at least partially depleted of various chemical components, but is enriched by flowing over the chemical reagents  26  contained within the cartridge  22 . The enriching process includes the dissolving and/or suspending of chemical reagents  26  within the plating solution  28 . The chemical reagents  26  usually have a solid state of matter (e.g., powder, pellets, crystalline), but could also be a viscous liquid or a suspension. Therefore, enriched plating solution  29  emerges from the output  34 . A progressive and consistent transformation or enrichment of the plating solution occurs as plating solution  28  flows across chemical reagents  26 . In one example, the shelves  24  are impermeable to liquids (e.g., metal plate with no holes or no porosity), so the plating solution  28  passes along and not through the shelves  24 . In another example, the shelves  24  are permeable to liquids, such as ceramic or mesh, so the plating solution  28  passes along and/or through the shelves  24 .  
         [0034]     Chemical reagents  26  are compounds or mixtures of compounds selected for the process requirements of the plating solution. Plating solutions include electroless plating solutions and electroplating solutions, wherein the latter is usually the anolyte or the catolyte. Electroplating systems are utilized to deposit materials such as copper, zinc, cadmium, nickel and other metals. In one preferred embodiment, the plating solution is an anolyte within an electroplating system used to plate copper.  
         [0035]     Chemical reagents  26  useful for copper ion replenishment in a plating solution include copper hydroxide, copper oxide, copper carbonate, copper sulfate and copper phosphate and combinations thereof, preferably copper hydroxide. Generally, plating solutions, enriched or depleted, have a copper ion concentration in a range from about 5 g/L to about 70 g/L.  
         [0036]     Chemical reagents  26  are also used to replenish plating solutions of other depleted compounds and ions. In one embodiment, chemical reagents are used to control the pH of the plating solution. The pH of the solution can be raised or lowered by adding a basic or acidic compound, respectively. Chemical reagents  26  for replenishing hydroxyl ions to increase the pH include copper hydroxide, ammonium salts, sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, magnesium hydroxide, calcium hydroxide, amongst others, and combinations thereof. Therefore, in one embodiment, copper hydroxide is used to replenish copper ions and hydroxyl ions.  
         [0037]     Porous material  25  is optionally placed at either or both ends of the cartridge  22  and include porous plastics, metals, ceramics, filters, frits, membranes, wool (e.g., glass or metal), packed inert media (e.g., silica or alumina) and the like. Generally, the porous material has pores that are penetrable for enriched plating solution (suspensions), but prevents chemical reagents  26  from uncontrollably passing through the cartridge  22 . The porous material has pores with a diameter in the range from about 10 μm to about 2,000 μm.  
         [0038]     FIGS.  4 A-C show cross-sectional views of cartridge system  20  with a variety of geometries for cartridges and shelves.  FIG. 4A  shows the four flat shelves  24  of  FIG. 3  as described above.  FIG. 4B  shows shelves with longitudinal grooves  36 . The grooves  36  further segregate the chemical reagents  26  into various rows running along each shelf.  FIG. 4C  shows a cylindrical cartridge  37  containing tubular shelves  38 . Tubular shelves  38  also hold chemical reagents  26  in segregated rows. The shelves distribute (i.e., provide more surface area) chemical reagents  26 . Time exposure between the plating solution and the chemical reagent varies the degree of enrichment the plating solution endures. Therefore, the flow of the plating solution through cartridge  22  varies in a range from about 0.5 L/min to about 10 L/min, depending on the bath volume and performance.  
         [0039]     The flow of the plating solution is maintained due to part of headspace  30  provided above the top surface of the chemical reagents  26 . Generally, headspace  30  has a height in the range from about 1 cm to about 50 cm, preferably from about 5 cm to about 30 cm. Headspace  30  changes throughout the process with respect to time, since the chemical reagents  26  are consumed by the plating solution and the height of headspace increases. Also, headspace  30  changes throughout the process with respect to certain segments along the shelves. Besides consumption, chemical reagents  26  also migrate and erode along the shelves.  
         [0040]     In several examples, as depicted in FIGS.  5 A-C, cartridge system  20  is placed into anolyte loops with various configurations. In one embodiment,  FIG. 5A  shows cartridge system  20  placed into a single anolyte loop. As anolyte requires replenishment of chemical reagents (e.g., Cu 2+  or OH − ), pump  120  draws depleted anolyte from the anolyte tank  110 . With control valve  130  open, pump  120  pushes the depleted anolyte through cartridge system  20 . The anolyte emerges from the cartridge system  20  enriched with the specific chemical reagents required for the plating process (e.g., Cu(OH) 2 ). Upon exiting the cartridge system  20 , anolyte flows to the electroplating cell  100 , where the plating process commences, forming depleted anolyte, which is transferred back to the anolyte tank  110 . This cycle resumes as the anolyte is recirculated throughout the anolyte loop.  
         [0041]     In another embodiment,  FIG. 5B  shows cartridge system  20  placed into an anolyte loop also including a bypass line. The bypass line is useful when the anolyte is only partially depleted of the necessary chemical reagents. Though depleted anolyte will contain some essential chemical reagents, the concentration of the reagents is too low and affects the plating process. However, partially depleted anolyte is suited to be recirculated and used in the electroplating process prior to being enriched by cartridge system  20 . Depleted or partially depleted anolyte is determined per process parameters. As anolyte requires replenishment of chemical reagents (e.g., Cu 2+  or OH − ), pump  120  draws depleted anolyte from the anolyte tank  110 . With control valve  130  open and control valve  135  closed, pump  120  pushes the depleted anolyte through cartridge system  20 . The anolyte emerges from the cartridge system  20  enriched with the specific chemical reagents required for the plating process (e.g., Cu(OH) 2 ). Upon exiting the cartridge system  20 , anolyte flows to the electroplating cell  100 . However, with control valve  130  closed and control valve  135  opened, pump  120  pushes the partially depleted anolyte through a bypass around the cartridge system  20  and directly to the electroplating cell  100 . Upon the commencement of the plating process, depleted anolyte is transferred back to the anolyte tank  110 . This cycle resumes as the anolyte is recirculated throughout the anolyte loop.  
         [0042]     The anolyte cycle system depicted in  FIG. 5B  has an advantage over the system depicted in  FIG. 5A  due to the cartridge bypass line, namely, more control of the supplemental chemical reagent addition. Since the system of  FIG. 5B  has the bypass line, anolyte is recirculated with the option to pass through cartridge system  20 . For any of the anolyte loops depicted in FIGS.  5 A-C, the capacity of anolyte tank  110  can be increased to slow the anolyte dilution from the addition of depleted anolyte coming from cell  100 .  
         [0043]     The system depicted in  FIG. 5C  includes several anolyte loops linked together via the anolyte tank  110 . One loop includes the electroplating cell  100  in fluid communication with the anolyte tank  110 . Pump  120  circulates the anolyte within this loop. However, an auxiliary loop is also linked with the anolyte tank  110 . The auxiliary loop includes the cartridge system  20  connected to a control valve  134  and a pump  125 . In one aspect, pump  125  is a high-pressure pump. Also incorporated to the auxiliary loop is a bypass line managed by control valve  132 . Therefore in one aspect, with control valve  134  opened and control valve  132  closed, anolyte can be circulated between the anolyte tank  110  and cartridge system  20  to be enriched with chemical reagents, while the anolyte is circulated between the anolyte tank  110  and the electroplating cell  100 . In another aspect, control valve  134  is closed while control valve  132  is opened and cartridge system  20  does not replenish the supplemental chemical reagents to the system.  
         [0044]     In another embodiment, FIGS.  6 A-B show cartridge  40  as a vertical vessel in which a lower portion of the interior of the vessel expands upwardly to form an inverted conical bottom  42 . The cartridge  40  includes top  39  as a portion of housing  41 , both made from an assortment of materials, such as plastics or metals, including stainless steel, aluminum, titanium, nickel-coated steel, various alloys amongst others.  
         [0045]     At the base of the conical bottom  42 , an injector  43  is positioned in a vertical arrangement. The conical bottom  42  collects the settling chemical reagents  26  by gravitational forces. This settling process maintains the chemical reagents  26  in contact with the injector  43 . The injector has an input  45  that is in fluid communication with the electroplating system. Depleted electrolyte  28  combined with or without gas (e.g., air) passes through the input  45  and is introduced into the cartridge  40  through at least one output  47  of injector  43 . In one embodiment, there are multiple outputs  47  in a single injector  43 . The orifice that provides the output  47  generally has a diameter in the range from about 0.1 mm to about 1 mm. As depicted in  FIG. 6B , outputs  47  are less than normal (i.e., &lt;90°) relative to the plane of the axis of the conical bottom  42 . That is, the outputs  47  generally point downward, towards the conical bottom  42  and extend through the sides  48  of injector  43 . However, in one embodiment (not shown), the channels are normal or pointing upward, but have an optional flap in order to keep chemical reagent from descending into the outputs.  
         [0046]     Plating solution or electrolyte is administered into the cartridge  40  through the injector  43 . Chemical reagents  26  are disposed within the cartridge  40 , so the electrolyte travels through the chemical reagents  26  and into a headspace  49 . An under pressure (e.g., vacuum system) and/or an over pressure (e.g., compressed gas) is utilized to assist the migration of the electrolyte through the cartridge  40 . The electrolyte becomes enriched with the chemical reagents  26 , (i.e., dissolved or suspended) while passing through the cartridge  40 . The enriched electrolyte  29  accumulates near or at the headspace  49 , and then proceeds to exit the cartridge  40  through the manifold  44 . In one embodiment, the headspace  49  has enriched anolyte  29  as well as accumulated gas  46  or air. The accumulated gas  46  is bled from the headspace prior or during the flow of enriched anolyte  29 . In another embodiment, a porous material (not shown), such as sponges, porous plastics, metals, ceramics, filters, frits, membranes, wool (e.g., glass or metal), packed inert media (e.g., silica or alumina) and the alike is displaced below the manifold  44  to inhibit any large particulate of chemical reagents  26  from leaving the cartridge  40 .  
         [0047]     In another embodiment,  FIG. 7  shows a plating system  50  that includes a cartridge  40  of the invention. The enriched electrolyte  29  is added to anolyte tank  52 , which is in fluid communication with an electroplating cell  56  and pump  58  within an anolyte loop. Anolyte is depleted of reagent chemical (e.g., CU 2+  and OH − ) during the plating process within the electroplating cell  56 . Pump  58  drives the circulation of depleted anolyte to the anolyte tank  52  and enriched anolyte from the anolyte tank  52  to the electroplating cell  56 .  
         [0048]     A pH controller  54 , pH sensor  57  and a computer  55  monitor and regulate the pH of the anolyte within the anolyte tank  52 . A pH controller may be selected from a variety of commercially available models, such as dTRANSpH 01 from JUMO Process Control Inc., DP24-E Process Meter from Omega, EMIT-pH from Pathfinder Instruments, and LED pH/ORP indicator/controller from Kemko Instruments. In one embodiment, the pH is maintained in the range from about 1.0 to about 5.0, preferably, from about 2.0 to about 4.0 and more preferably from about 2.8 to about 3.0. In another embodiment, the pH is maintained at less than 3.4 to prevent chemical precipitants (e.g., copper hydroxide) from forming and clouding the anolyte.  
         [0049]     As the pH of the anolyte becomes too low, an aliquot of the anolyte is transferred from anolyte tank  52  to canister  53  via three-way valve  60 . Generally, three-way valve  61  is positioned to pressurize anolyte tank  52  with compressed gas (e.g., air) and three-way valve  60  is positioned as to accept the aliquot from the anolyte tank  52  to the canister  53 . Once the aliquot is transferred, then both valves  60  and  61  are turned off. Subsequently, three way valve  61  is positioned to pressurize the canister  53  containing the aliquot of the anolyte while three-way valve  60  is positioned to permit the flow of the aliquot into the cartridge  40  via the injector  43 . The enriched anolyte emerges from the cartridge  40  via the manifold  44  and into the anolyte tank  52 . As the enriched anolyte combines with the depleted anolyte, acidic protons are neutralized by the incoming hydroxyl ions and copper ions become more concentrated. In practice, the concentration of the anolyte will not vary much since control of the replenishment is occurring real time. That is, when valves  60  and  61  are timed and positioned correctly, the anolyte will reach a relatively constant pH with minimal flux (e.g., about 0.5 pH units). The compressed gas is delivered from a source  62 , such as a tank or an in-house line and may include air, N 2 , Ar, He, H 2  and combinations thereof.  
         [0050]      FIG. 8  is a diagram illustrating a timing sequence of valves  60  and  61  during an electroplating process useful in the plating system  50  depicted in  FIG. 7 . The timing of valves  60  and  61  is controlled by the pH controller  54  in combination with a computer  55 . The valves  60  and  61  change positions every second or so and remain synchronized as described above. When the pH of the anolyte drops to a lower limit (LL), the compressed gas (e.g., air) moves the electrolyte from canister  53  into cartridge  40 . The time t 1  is slightly longer (e.g., about a second) than that required to push all of the anolyte from canister  53 , so that a small amount of air also penetrates in to the cartridge  40 . The air provides a thorough mixing of the chemical reagents with the anolyte and enriches the suspension (e.g., copper hydroxide) near the top of the cartridge  40  within headspace  49 . This thorough mixing with the air and the conical shape of the bottom of the cartridge prevents cake formation. During time t 2 , compressed air is stopped by closing valve  61  and canister  53  is refilled with anolyte through valve  60 . During t 3 , the anolyte is injected into cartridge  40  with the timing quick enough to prevent penetration of air into the canister  53 , about a second. Canister  53  is refilled with anolyte that is subsequently injected into the cartridge  40 . Thereafter, an enriched anolyte is transferred from the cartridge  40  to the anolyte tank  52 . This cycle continues until the pH reaches a higher limit (HL), then ceases until the pH of the anolyte within the anolyte tank reaches the LL. The overall sequence repeats during the electroplating process.  
         [0051]     In another embodiment,  FIG. 9  shows a plating system  70  that includes a cartridge  40 . The enriched electrolyte  29  is added to anolyte tank  52 , which is in fluid communication with an electroplating cell  56  and pump  58  within an anolyte loop. Anolyte is depleted of reagent chemical (e.g., Cu 2+  and OH − ) during the plating process within the electroplating cell  56 . Pump  58  drives the circulation of depleted anolyte to the anolyte tank  52  and enriched anolyte from the anolyte tank  52  to the electroplating cell  56 . The depleted anolyte is temporally contained within a section  71  of the anolyte tank  52 . Section  71  is separated by partition  80  and will gather depleted anolyte as well as enriched anolyte, before flowing over into the main compartment of anolyte tank  52 .  
         [0052]     A pH controller  54 , pH sensor  57  and a computer  55  monitors and regulates the pH of the anolyte within section  71 . In one embodiment, the pH is maintained in the range from about 1.0 to about 5.0, preferably, from about 2.0 to about 4.0 and more preferably from about 2.8 to about 3.0. In another embodiment, the pH is maintained at less than 3.4 to prevent chemical precipitants (e.g., copper hydroxide) from forming and clouding the anolyte.  
         [0053]     As the pH of the anolyte becomes too low, an aliquot of the anolyte is transferred from anolyte tank  52  to canister  53  via two-way valve  76 . Pump  58  helps push the anolyte to canister  53 . Once the aliquot is transferred, then two-way valve  72  is positioned to pressurize the canister  53  containing the aliquot of the anolyte while two-way valve  78  is positioned to permit the flow of the aliquot into the cartridge  40 . The enriched anolyte flows from the cartridge  40  to section  71  of the anolyte tank  52 . As the enriched anolyte combines with the depleted anolyte, acidic protons are neutralized by the incoming hydroxyl ions and copper ions become more concentrated. Two-way valve  74  is positioned open and gas flow agitates the enriched anolyte with the depleted with the flow of gas. In practice, the concentration of the anolyte will not vary much since the replenishment is occurring in real time. That is, when valves  72 ,  74 ,  76  and  78  are timed and positioned correctly, the anolyte will reach a relatively constant pH with minimal flux (e.g., about 0.5 pH units). The compressed gas is delivered from a source  62 , such as a tank or an in-house line and may include air, N 2 , Ar, He, H 2  and combinations thereof.  
         [0054]     In one embodiment depicted in  FIG. 10A , injector system  82  includes an injector  84  with output holes  85  and a cup  86  with output holes  87 . Cup  86  is rotatable as to line-up the output holes  85  with output holes  87 . Once lined-up, anolyte will pass through holes  85  and  87  and into the cartridge. To remove cartridge  40 , output holes  85  and  87  are misaligned to turn off the excess of chemical reagents  26  from escaping the cartridge  40 .  FIG. 10A  illustrates cup  86  disposed within the injector  84 , while in another embodiment,  FIG. 10B  shows an injector  94  disposed within a cup  96  as part of injector system  92 . Also, injector  94  contains output holes  95  and cup  96  contains output holes  97 . The output holes  85  and  87  generally point horizontal while the output holes  95  and  97  point in a downwardly direction.  
         [0055]     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.