Abstract:
The present invention generally provides an electro-chemical deposition system that is designed with a flexible architecture that is expandable to accommodate future designs rules and gap fill requirements and provides satisfactory throughput to meet the demands of other processing systems. The electro-chemical deposition system generally comprises a front-end loading station, a mainframe including one or more processing cells, and an electrolyte replenishing system fluidly connected to the one or more electrical processing cells. The electrolyte replenishing system comprises a main electrolyte supply tank and an analyzer module and dosing module coupled thereto. The analyzer module includes one or more chemical analyzers to monitor the concentrations of various chemicals in the main electrolyte supply tank. Information provided by the analyzer module is transmitted via a central control system to the dosing module. Source tanks in the dosing module communicate with the main supply tank to deliver the desired proportions of chemicals thereto. Preferably, the electrolyte analysis is performed continuously during processing to provide real-time data and electrolyte adjustments.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to deposition of a metal layer onto a wafer/substrate. More particularly, the present invention relates to an electrochemical deposition system or electroplating system for forming a metal layer on a wafer/substrate having an integrated electrolyte analyzing module. 
     2. Background of the Related Art 
     Sub-quarter micron, multi-level metallization is one of the key technologies for the next generation of ultra large scale integration (ULSI). The multilevel interconnects that lie at the heart of this technology require planarization of interconnect features formed in high aspect ratio apertures, including contacts, vias, lines and other features. Reliable formation of these interconnect features is very important to the success of ULSI and to the continued effort to increase circuit density and quality on individual substrates and die. 
     As circuit densities increase, the widths of vias, contacts and other features, as well as the dielectric materials between them, decrease to less than 250 nanometers, whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Many traditional deposition processes, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), have difficulty filling structures where the aspect ratio exceed 4:1, and particularly where it exceeds 10:1. Therefore, there is a great amount of ongoing effort being directed at the formation of void-free, nanometer-sized features having high aspect ratios wherein the ratio of feature height to feature width can be 4:1 or higher. Additionally, as the feature widths decrease, the device current remains constant or increases, which results in an increased current density in the feature. 
     Elemental aluminum (Al) and its alloys have been the traditional metals used to form lines and plugs in semiconductor processing because of aluminum&#39;s perceived low electrical resistivity, its superior adhesion to silicon dioxide (SiO 2 ), its ease of patterning, and the ability to obtain it in a highly pure form. However, aluminum has a higher electrical resistivity than other more conductive metals such as copper, and aluminum also can suffer from electromigration leading to the formation of voids in the conductor. 
     Copper and its alloys have lower resistivities than aluminum and significantly higher electromigration resistance as compared to aluminum. These characteristics are important for supporting the higher current densities experienced at high levels of integration and increase device speed. Copper also has good thermal conductivity and is available in a highly pure state. Therefore, copper is becoming a choice metal for filling sub-quarter micron, high aspect ratio interconnect features on semiconductor substrates. 
     Despite the desirability of using copper for semiconductor device fabrication, choices of fabrication methods for depositing copper into very high aspect ratio features, such as a 4:1, having 0.35μ (or less) wide vias are limited. As a result of these process limitations, plating, which had previously been limited to the fabrication of lines on circuit boards, is just now being used to fill vias and contacts on semiconductor devices. 
     Metal electroplating is generally known and can be achieved by a variety of techniques. A typical method generally comprises physical vapor depositing a barrier layer over the feature surfaces, physical vapor depositing a conductive metal seed layer, preferably copper, over the barrier layer, and then electroplating a conductive metal over the seed layer to fill the structure/feature. Finally, the deposited layers and the dielectric layers are planarized, such as by chemical mechanical polishing (CMP), to define a conductive interconnect feature. 
     FIG. 1 is a cross sectional view of a simplified typical fountain plater  10  incorporating contact pins. Generally, the fountain plater  10  includes an electrolyte container  12  having a top opening, a substrate holder  14  disposed above the electrolyte container  12 , an anode  16  disposed at a bottom portion of the electrolyte container  12  and a contact ring  20  contacting the substrate  22 . A plurality of grooves  24  are formed in the lower surface of the substrate holder  14 . A vacuum pump (not shown) is coupled to the substrate holder  14  and communicates with the grooves  24  to create a vacuum condition capable of securing the substrate  22  to the substrate holder  14  during processing. The contact ring  20  comprises a plurality of metallic or semi-metallic contact pins  26  distributed about the peripheral portion of the substrate  22  to define a central substrate plating surface. The plurality of contact pins  26  extend radially inwardly over a narrow perimeter portion of the substrate  22  and contact a conductive seed layer of the substrate  22  at the tips of the contact pins  26 . A power supply (not shown) is attached to the pins  26  thereby providing an electrical bias to the substrate  22 . The substrate  22  is positioned above the cylindrical electrolyte container  12  and electrolyte flow impinges perpendicularly on the substrate plating surface during operation of the cell  10 . 
     While present day electroplating cells, such as the one shown in FIG. 1, achieve acceptable results on larger scale substrates, a number of obstacles impair consistent reliable electroplating onto substrates having micron-sized, high aspect ratio features. Generally, these obstacles include providing uniform power distribution and current density across the substrate plating surface to form a metal layer having uniform thickness, preventing unwanted edge and backside deposition to control contamination to the substrate being processed as well as subsequent substrates, and maintaining a vacuum condition which secures the substrate to the substrate holder during processing. Also, the present day electroplating cells have not provided satisfactory throughput to meet the demands of other processing systems and are not designed with a flexible architecture that is expandable to accommodate future designs rules and gap fill requirements. 
     Additionally, current electroplating systems are incapable of performing necessary processing steps without resorting to peripheral components and time intensive efforts. For example, analysis of the processing chemicals is required periodically during the plating process. The analysis determines the composition of the electrolyte to ensure proper proportions of the ingredients. Conventional analysis is performed by extracting a sample of electrolyte from a test port and transferring the sample to a remote analyzer. The electrolyte composition is then manually adjusted according to the results of the analysis. The analysis must be performed frequently because the concentrations of the various chemicals are in constant flux. However, the foregoing method is time consuming and limits the number of analyses which can be performed. 
     Therefore, there remains a need for an electrochemical deposition system that is designed with a flexible architecture that is expandable to accommodate future designs rules and gap fill requirements and provides satisfactory throughput to meet the demands of other processing systems. There is also a need for an electrochemical deposition system that provides uniform power distribution and current density across the substrate plating surface to form a metal layer having uniform thickness and maintain a vacuum condition which secures the substrate to the substrate holder during processing. It would be desirable for the system to prevent and/or remove unwanted edge and backside deposition to control contamination to the substrate being processed as well as subsequent substrates. It would also be desirable for the system to include one or more chemical analyzers integrated with the processing system to provide real-time analysis of the electrolyte composition. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides an electrochemical deposition system that is designed with a flexible architecture that is expandable to accommodate future designs rules and gap fill requirements and provides satisfactory throughput to meet the demands of other processing systems. The electrochemical deposition system generally comprises a mainframe having a mainframe wafer transfer robot, a loading station disposed in connection with the mainframe, one or more processing cells disposed in connection with the mainframe, and an electrolyte supply fluidly connected to the one or more electrical processing cells. Preferably, the electrochemical deposition system includes a system controller for controlling an electro-chemical deposition process and related components, a spin-rinse-dry (SRD) station disposed between the loading station and the mainframe, and an electrolyte replenishing system including an integrated chemical analyzer. 
     One aspect of the invention provides an electrochemical deposition system that provides uniform power distribution and current density across the substrate plating surface to form a metal layer having uniform thickness and maintain a vacuum condition which secures the substrate to the substrate holder during processing. 
     Another aspect of the invention provides an electrochemical deposition system that prevents and/or remove unwanted edge and backside deposition to control contamination to the substrate being processed as well as subsequent substrates. 
     Still another aspect of the invention provides a real-time chemical analyzer module. The chemical analyzer module includes at least one and preferably two analyzers operated by a controller and integrated with a control system of the electro-chemical deposition system. A sample line provides continuous flow of electrolyte from a main electrolyte tank to the chemical analyzer module. A first analyzer determines the concentrations of organic substances in the electrolyte while the second analyzer determines the concentrations of inorganic substances. 
     Another aspect of the invention provides a real-time chemical analyzer module and a dosing module. The chemical analyzer module includes at least one and preferably two analyzers operated by a controller and integrated with a control system of the electrochemical deposition system. A sample line provides continuous flow of electrolyte from a main electrolyte tank to the chemical analyzer module. A first analyzer determines the concentrations of organic substances in the electrolyte while the second analyzer determines the concentrations of inorganic substances. The dosing module is then activated to deliver the proper proportions of chemicals to the main tank in response to the information obtained by the chemical analyzer module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof 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 is a cross sectional view of a simplified typical fountain plater  10  incorporating contact pins. 
     FIG. 2 is a perspective view of an electroplating system platform  200  of the invention. 
     FIG. 3 is a schematic view of an electroplating system platform  200  of the invention. 
     FIG. 4 is a schematic perspective view of a spin-rinse-dry (SRD) module of the present invention, incorporating rinsing and dissolving fluid inlets. 
     FIG. 5 is a side cross sectional view of the spin-rinse-dry (SRD) module of FIG.  4  and shows a substrate in a processing position vertically disposed between fluid inlets. 
     FIG. 6 is a cross sectional view of an electroplating process cell  240  according to the invention. 
     FIG. 7 is a partial cross sectional perspective view of a cathode contact ring. 
     FIG. 8 is a cross sectional perspective view of the cathode contact ring showing an alternative embodiment of contact pads. 
     FIG. 9 is a cross sectional perspective view of the cathode contact ring showing an alternative embodiment of the contact pads and an isolation gasket. 
     FIG. 10 is a cross sectional perspective view of the cathode contact ring showing the isolation gasket. 
     FIG. 11 is a simplified schematic diagram of the electrical circuit representing the electroplating system through each contact pin. 
     FIG. 12 is a cross sectional view of a wafer assembly  450  of the invention. 
     FIG. 12A is an enlarged cross sectional view of the bladder area of FIG.  12 . 
     FIG. 13 is a partial cross sectional view of a wafer holder plate. 
     FIG. 14 is a partial cross sectional view of a manifold. 
     FIG. 15 is a partial cross sectional view of a bladder. 
     FIG. 16 is a schematic diagram of an electrolyte replenishing system  220 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2 is a perspective view of an electroplating system platform  200  of the invention. FIG. 3 is a schematic view of an electroplating system platform  200  of the invention. Referring to both FIGS. 2 and 3, the electroplating system platform  200  generally comprises a loading station  210 , a spin-rinse-dry (SRD) station  212 , a mainframe  214 , and an electrolyte replenishing system  220 . Preferably, the electroplating system platform  200  is enclosed in a clean environment using panels such as plexiglass panels. The mainframe  214  generally comprises a mainframe transfer station  216  and a plurality of processing stations  218 . Each processing station  218  includes one or more processing cells  240 . An electrolyte replenishing system  220  is positioned adjacent the electroplating system platform  200  and connected to the process cells  240  individually to circulate electrolyte used for the electroplating process. The electroplating system platform  200  also includes a control system  222 , typically comprising a programmable microprocessor. 
     The loading station  210  preferably includes one or more wafer cassette receiving areas  224 , one or more loading station transfer robots  228  and at least one wafer orientor  230 . The number of wafer cassette receiving areas, loading station transfer robots  228  and wafer orientor included in the loading station  210  can be configured according to the desired throughput of the system. As shown for one embodiment in FIGS. 2 and 3, the loading station  210  includes two wafer cassette receiving areas  224 , two loading station transfer robots  228  and one wafer orientor  230 . A wafer cassette  232  containing wafers  234  is loaded onto the wafer cassette receiving area  224  to introduce wafers  234  into the electroplating system platform. The loading station transfer robot  228  transfers wafers  234  between the wafer cassette  232  and the wafer orientor  230 . The loading station transfer robot  228  comprises a typical transfer robot commonly known in the art. The wafer orientor  230  positions each wafer  234  in a desired orientation to ensure that the wafer is properly processed. The loading station transfer robot  228  also transfers wafers  234  between the loading station  210  and the SRD station  212 . 
     FIG. 4 is a schematic perspective view of a spin-rinse-dry (SRD) module of the present invention, incorporating rinsing and dissolving fluid inlets. FIG. 5 is a side cross sectional view of the spin-rinse-dry (SRD) module of FIG.  4  and shows a substrate in a processing position vertically disposed between fluid inlets. Preferably, the SRD station  212  includes one or more SRD modules  236  and one or more wafer pass-through cassettes  238 . Preferably, the SRD station  212  includes two SRD modules  236  corresponding to the number of loading station transfer robots  228 , and a wafer pass-through cassette  238  is positioned above each SRD module  236 . The wafer pass-through cassette  238  facilitates wafer transfer between the loading station  210  and the mainframe  214 . The wafer pass-through cassette  238  provides access to and from both the loading station transfer robot  228  and a robot in the mainframe transfer station  216 . 
     Referring to FIGS. 4 and 5, the SRD module  238  comprises a bottom  330   a  and a sidewall  330   b , and an upper shield  330   c  which collectively define a SRD module bowl  330   d , where the shield attaches to the sidewall and assists in retaining the fluids within the SRD module. Alternatively, a removable cover could also be used. A pedestal  336 , located in the SRD module, includes a pedestal support  332  and a pedestal actuator  334 . The pedestal  336  supports the substrate  338  (shown in FIG. 5) on the pedestal upper surface during processing. The pedestal actuator  334  rotates the pedestal to spin the substrate and raises and lowers the pedestal as described below. The substrate may be held in place on the pedestal by a plurality of lamps  337 . The clamps pivot with centrifugal force and engage the substrate preferably in the edge exclusion zone of the substrate. In a preferred embodiment, the clamps engage the substrate only when the substrate lifts off the pedestal during the processing. Vacuum passages (not shown) may also be used as well as other holding elements. The pedestal has a plurality of pedestal arms  336   a  and  336   b , so that the fluid through the second nozzle may impact as much surface area on the lower surface of the substrate as is practical. An outlet  339  allows fluid to be removed from the SRD module. The terms “below”, “above”, “bottom”, “top”, “up”, “down”, “upper”, and “lower” and other positional terms used herein are shown with respect to the embodiments in the figures and may be varied depending on the relative orientation of the processing apparatus. 
     A first conduit  346 , through which a first fluid  347  flows, is connected to a valve  347   a . The conduit may be hose, pipe, tube, or other fluid containing conduits. The valve  347   a  controls the flow of the first fluid  347  and may be selected from a variety of valves including a needle, globe, butterfly, or other valve types and may include a valve actuator, such as a solenoid, that can be controlled with a controller  362 . The conduit  346  connects to a first fluid inlet  340  that is located above the substrate and includes a mounting portion  342  to attach to the SRD module and a connecting portion  344  to attach to the conduit  346 . The first fluid inlet is shown with a single first nozzle  348  to deliver a first fluid  347  under pressure onto the substrate upper surface. However, multiple nozzles could be used and multiple fluid inlets could be positioned about the inner perimeter of the SRD module. Preferably, nozzles placed above the substrate should be outside the diameter of the substrate to lessen the risk of the nozzles dripping on the substrate. The first fluid inlet could be mounted in a variety of locations, including through a cover positioned above the substrate. Additionally, the nozzle may articulate to a variety of positions using an articulating member  343 , such as a ball and socket joint. 
     Similar to the first conduit and related elements described above, a second conduit  352  is connected to a control valve  349   a  and a second fluid inlet  350  with a second nozzle  351 . The second fluid inlet  350  is shown below the substrate and angled upward to direct a second fluid under the substrate through the second nozzle  351 . Similar to the first fluid inlet, the second fluid inlet may include a plurality of nozzles, a plurality of fluid inlets and mounting locations, and a plurality of orientations including using the articulating member  353 . Each fluid inlet could be extended into the SRD module at a variety of positions. For instance, if the flow is desired to be a certain angle that is directed back toward the SRD module periphery along the edge of the substrate, the nozzles could be extended radially inward and the discharge from the nozzles be directed back toward the SRD module periphery. 
     The controller  362  could individually control the two fluids and their respective flow rates, pressure, and timing, and any associated valving, as well as the spin cycle(s). The controller could be remotely located, for instance, in a control panel or control room and the plumbing controlled with remote actuators. An alternative embodiment, shown in dashed lines, provides an auxiliary fluid inlet  346   a  connected to the first conduit  346  with a conduit  346   b  and having a control valve  346   c , which may be used to flow a rinsing fluid on the backside of the substrate after the dissolving fluid is flown without having to reorient the substrate or switch the flow through the second fluid inlet to a rinsing fluid. 
     In one embodiment, the substrate is mounted with the deposition surface of the disposed face up in the SRD module bowl. As will be explained below, for such an arrangement, the first fluid inlet would generally flow a rinsing fluid, typically deionized water or alcohol. Consequently, the backside of the substrate would be mounted facing down and a fluid flowing through the second fluid inlet would be a dissolving fluid, such as an acid, including hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, or other dissolving liquids or fluids, depending on the material to be dissolved. Alternatively, the first fluid and the second fluid are both rinsing fluids, such as deionized water or alcohol, when the desired process is to rinse the processed substrate. 
     In operation, the pedestal is in a raised position, shown in FIG. 4, and a robot (not shown) places the substrate, front side up, onto the pedestal. The pedestal lowers the substrate to a processing position where the substrate is vertically disposed between the first and the second fluid inlets. Generally, the pedestal actuator rotates the pedestal between about 5 to about 5000 rpm, with a typical range between about 20 to about 2000 rpm for a 200 mm substrate. The rotation causes the lower end  337   a  of the clamps to rotate outward about pivot  337   b , toward the periphery of the SRD module sidewall, due to centrifugal force. The clamp rotation forces the upper end  337   c  of the clamp inward and downward to center and hold the substrate  338  in position on the pedestal  336 , preferably along the substrate edge. The clamps may rotate into position without touching the substrate and hold the substrate in position on the pedestal only if the substrate significantly lifts off the pedestal during processing. With the pedestal rotating the substrate, a rinsing fluid is delivered onto the substrate front side through the first fluid inlet  340 . The second fluid, such as an acid, is delivered to the backside surface through the second fluid inlet to remove any unwanted deposits. The dissolving fluid chemically reacts with the deposited material and dissolves and then flushes the material away from the substrate backside and other areas where any unwanted deposits are located. In a preferred embodiment, the rinsing fluid is adjusted to flow at a greater rate than the dissolving fluid to help protect the front side of the substrate from the dissolving fluid. The first and second fluid inlets are located for optimal performance depending on the size of the substrate, the respective flow rates, spray patterns, and amount and type of deposits to be removed, among other factors. In some instances, the rinsing fluid could be routed to the second fluid inlet after a dissolving fluid has dissolved the unwanted deposits to rinse the backside of the substrate. In other instances, an auxiliary fluid inlet connected to flow rinsing fluid on the backside of the substrate could be used to rinse any dissolving fluid residue from the backside. After rinsing the front side and/or backside of the substrate, the fluid(s) flow is stopped and the pedestal continues to rotate, spinning the substrate, and thereby effectively drying the surface. 
     The fluid(s) is generally delivered in a spray pattern, which may be varied depending on the particular nozzle spray pattern desired and may include a fan, jet, conical, and other patterns. One spray pattern for the first and second fluids through the respective fluid inlets, when the first fluid is a rinsing fluid, is fan pattern with a pressure of about 10 to about 15 pounds per square inch (psi) and a flow rate of about 1 to about 3 gallons per minute (gpm) for a 200 mm wafer. The invention could also be used to remove the unwanted deposits along the edge of the substrate to create an edge exclusion zone. By adjustment of the orientation and placement of the nozzles, the flow rates of the fluids, the rotational speed of the substrate, and the chemical composition of the fluids, the unwanted deposits could be removed from the edge and/or edge exclusion zone of the substrate as well. Thus, substantially preventing dissolution of the deposited material on the front side surface may not necessarily include the edge or edge exclusion zone of the substrate. Also, preventing dissolution of the deposited material on the front side surface is intended to include at least preventing the dissolution so that the front side with the deposited material is not impaired beyond a commercial value. 
     One method of accomplishing the edge exclusion zone dissolution process is to rotate the disk at a slower speed, such as about 100 to about 1000 rpm, while dispensing the dissolving fluid on the backside of the substrate. The centrifugal force moves the dissolving fluid to the edge of the substrate and forms a layer of fluid around the edge due to surface tension of the fluid, so that the dissolving fluid overlaps from the backside to the front side in the edge area of the substrate. The rotational speed of the substrate and the flow rate of the dissolving fluid may be used to determine the extent of the overlap onto the front side. For instance, a decrease in rotational speed or an increase in flow results in a less overlap of fluid to the opposing side, e.g., the front side. Additionally, the flow rate and flow angle of the rinsing fluid delivered to the front side can be adjusted to offset the layer of dissolving fluid onto the edge and/or frontside of the substrate. In some instances, the dissolving fluid may be used initially without the rinsing fluid to obtain the edge and/or edge exclusion zone removal, followed by the rinsing/dissolving process of the present invention described above. 
     The SRD module  238  is connected between the loading station  210  and the mainframe  214 . The mainframe  214  generally comprises a mainframe transfer station  216  and a plurality of processing stations  218 . Referring to FIGS. 2 and 3, the mainframe  214 , as shown, includes two processing stations  218 , each processing station  218  having two processing cells  240 . The mainframe transfer station  216  includes a mainframe transfer robot  242 . Preferably, the mainframe transfer robot  242  comprises a plurality of individual robot arms  244  that provides independent access of wafers in the processing stations  218  and the SRD stations  212 . As shown in FIG. 3, the mainframe transfer robot  242  comprises two robot arms  244 , corresponding to the number of processing cells  240  per processing station  218 . Each robot arm  244  includes a robot blade  246  for holding a wafer during a wafer transfer. Preferably, each robot arm  244  is operable independently of the other arm to facilitate independent transfers of wafers in the system. Alternatively, the robot arms  244  operate in a linked fashion such that one robot extends as the other robot arm retracts. 
     Preferably, the mainframe transfer station  216  includes a flipper robot  248  that facilitates transfer of a wafer from a face-up position on the robot blade  246  of the mainframe transfer robot  242  to a face down position for a process cell  240  that requires face-down processing of wafers. The flipper robot  248  includes a main body  250  that provides both vertical and rotational movements with respect to a vertical axis of the main body  250  and a flipper robot arm  252  that provides rotational movement along a horizontal axis along the flipper robot arm  252 . Preferably, a vacuum suction gripper  254 , disposed at the distal end of the flipper robot arm  252 , holds the wafer as the wafer is flipped and transferred by the flipper robot  248 . The flipper robot  248  positions a wafer  234  into the processing cell  240  for face-down processing. The details of the electroplating processing cell according to the invention will be discussed below. 
     FIG. 6 is a cross sectional view of an electroplating process cell  240  according to the invention. The processing cell  240  generally comprises a head assembly  410 , a process kit  420  and an electrolyte collector  440 . Preferably, the electrolyte collector  440  is secured onto the body  442  of the mainframe  214  over an opening  443  that defines the location for placement of the process kit  420 . The electrolyte collector  440  includes an inner wall  446 , an outer wall  448  and a bottom  447  connecting the walls. An electrolyte outlet  449  is disposed through the bottom  447  of the electrolyte collector  440  and connected to the electrolyte replenishing system  220  (shown in FIG. 2) through tubes, hoses, pipes or other fluid transfer connectors. 
     The head assembly  410  is mounted onto a head assembly frame  452 . The head assembly frame  452  includes a mounting post  454  and a cantilever arm  456 . The mounting post  454  is mounted onto the body  442  of the mainframe  214 , and the cantilever arm  456  extends laterally from an upper portion of the mounting post  454 . Preferably, the mounting post  454  provides rotational movement with respect to a vertical axis along the mounting post to allow rotation of the head assembly  410 . The head assembly  410  is attached to a mounting plate  460  disposed at the distal end of the cantilever arm  456 . The lower end of the cantilever arm  456  is connected to a cantilever arm actuator  457 , such as a pneumatic cylinder, mounted on the mounting post  454 . The cantilever arm actuator  457  provides pivotal movement of the cantilever arm  456  with respect to the joint between the cantilever arm  456  and the mounting post  454 . When the cantilever arm actuator  457  is retracted, the cantilever arm  456  moves the head assembly  410  away from the process kit  420  to provide the spacing required to remove and/or replace the process kit  420  from the electroplating process cell  240 . When the cantilever arm actuator  457  is extended, the cantilever arm  456  moves the head assembly  410  toward the process kit  420  to position the wafer in the head assembly  410  in a processing position. 
     The head assembly  410  generally comprises a wafer holder assembly  450  and a wafer assembly actuator  458 . The wafer assembly actuator  458  is mounted onto the mounting plate  460 , and includes a head assembly shaft  462  extending downwardly through the mounting plate  460 . The lower end of the head assembly shaft  462  is connected to the wafer holder assembly  450  to position the wafer holder assembly  450  in a processing position and in a wafer loading position. 
     The wafer holder assembly  450  generally comprises a wafer holder  464  and a cathode contact ring  466 . FIG. 7 is a cross sectional view of one embodiment of a cathode contact ring  466  of the present invention. In general, the contact ring  466  comprises an annular body having a plurality of conducting members disposed thereon. The annular body is constructed of an insulating material to electrically isolate the plurality of conducting members. Together the body and conducting members form a diametrically interior substrate seating surface which, during processing, supports a substrate and provides a current thereto. 
     Referring now to FIG. 7 in detail, the contact ring  466  generally comprises a plurality of conducting members  765  at least partially disposed within an annular insulative body  770 . The insulative body  770  is shown having a flange  762  and a downward sloping shoulder portion  764  leading to a substrate seating surface  768  located below the flange  762  such that the flange  762  and the substrate seating surface  768  lie in offset and substantially parallel planes. Thus, the flange  762  may be understood to define a first plane while the substrate seating surface  768  defines a second plane parallel to the first plane wherein the shoulder  764  is disposed between the two planes. However, contact ring design shown in FIG. 7 is intended to be merely illustrative. In another embodiment, the shoulder portion  764  may be of a steeper angle including a substantially vertical angle so as to be substantially normal to both the flange  762  and the substrate seating surface  768 . Alternatively, the contact ring  466  may be substantially planar thereby eliminating the shoulder portion  764 . However, for reasons described below, a preferred embodiment comprises the shoulder portion  764  shown in FIG. 6 or some variation thereof. 
     The conducting members  765  are defined by a plurality of outer electrical contact pads  780  annularly disposed on the flange  762 , a plurality of inner electrical contact pads  772  disposed on a portion of the substrate seating surface  768 , and a plurality of embedded conducting connectors  776  which link the pads  772 ,  780  to one another. The conducting members  765  are isolated from one another by the insulative body  770  which may be made of a plastic such as polyvinylidenefluoride (PVDF), perfluoroalkoxy resin (PFA), Teflon™, and Tefzel™, or any other insulating material such as Alumina (Al 2 O 3 ) or other ceramics. The outer contact pads  780  are coupled to a power supply (not shown) to deliver current and voltage to the inner contact pads  772  via the connectors  776  during processing. In turn, the inner contact pads  772  supply the current and voltage to a substrate by maintaining contact around a peripheral portion of the substrate. Thus, in operation the conducting members  765  act as discrete current paths electrically connected to a substrate. 
     Low resistivity, and conversely high conductivity, are directly related to good plating. To ensure low resistivity, the conducting members  765  are preferably made of copper (Cu), platinum (Pt), tantalum (Ta), titanium (Ti), gold (Au), silver (Ag), stainless steel or other conducting materials. Low resistivity and low contact resistance may also be achieved by coating the conducting members  765  with a conducting material. Thus, the conducting members  765  may, for example, be made of copper (resistivity for copper is approximately 2×10 −8  Ω·m) and be coated with platinum (resistivity for platinum is approximately 10.6×10 −8  Ω·m). Coatings such as tantalum nitride (TaN), titanium nitride (TiN), rhodium (Rh), Au, Cu, or Ag on a conductive base materials such as stainless steel, molybdenum (Mo), Cu, and Ti are also possible. Further, since the contact pads  772 ,  780  are typically separate units bonded to the conducting connectors  776 , the contact pads  772 ,  780  may comprise one material, such as Cu, and the conducting members  765  another, such as stainless steel. Either or both of the pads  772 ,  180  and conducting connectors  776  may be coated with a conducting material. Additionally, because plating repeatability may be adversely affected by oxidation which acts as an insulator, the inner contact pads  772  preferably comprise a material resistant to oxidation such as Pt, Ag, or Au. 
     In addition to being a function of the contact material, the total resistance of each circuit is dependent on the geometry, or shape, of the inner contact inner contact pads  772  and the force supplied by the contact ring  466 . These factors define a constriction resistance, R CR , at the interface of the inner contact pads  772  and the substrate seating surface  768  due to asperities between the two surfaces. Generally, as the applied force is increased the apparent area is also increased. The apparent area is, in turn, inversely related to R CR  SO that an increase in the apparent area results in a decreased R CR . Thus, to minimize overall resistance it is preferable to maximize force. The maximum force applied in operation is limited by the yield strength of a substrate which may be damaged under excessive force and resulting pressure. However, because pressure is related to both force and area, the maximum sustainable force is also dependent on the geometry of the inner contact pads  772 . Thus, while the contact pads  772  may have a flat upper surface as in FIG. 7, other shapes may be used to advantage. For example, two preferred shapes are shown in FIGS. 8 and 9. FIG. 8 shows a knife-edge contact pad and FIG. 9 shows a hemispherical contact pad. A person skilled in the art will readily recognize other shapes which may be used to advantage. A more complete discussion of the relation between contact geometry, force, and resistance is given in Ney Contact Manual, by Kenneth E. Pitney, The J. M. Ney Company, 1973, which is hereby incorporated by reference in its entirety. 
     The number of connectors  776  may be varied depending on the particular number of contact pads  772  (shown in FIG. 7) desired. For a 200 mm substrate, preferably at least twenty-four connectors  776  are spaced equally over 360°. However, as the number of connectors reaches a critical level, the compliance of the substrate relative to the contact ring  466  is adversely affected. Therefore, while more than twenty-four connectors  776  may be used, contact uniformity may eventually diminish depending on the topography of the contact pads  772  and the substrate stiffness. Similarly, while less than twenty-four connectors  776  may be used, current flow is increasingly restricted and localized, leading to poor plating results. Since the dimensions of the present invention are readily altered to suit a particular application (for example, a 300 mm substrate), the optimal number may easily be determined for varying scales and embodiments. 
     As shown in FIG. 10, the substrate seating surface  768  comprises an isolation gasket  782  disposed on the insulative body  770  and extending diametrically interior to the inner contact pads  772  to define the inner diameter of the contact ring  466 . The isolation gasket  782  preferably extends slightly above the inner contact pads  772  (e.g., a few mils) and preferably comprises an elastomer such as Viton™, Teflon™, buna rubber and the like. Where the insulative body  770  also comprises an elastomer the isolation gasket  782  may be of the same material. In the latter embodiment, the isolation gasket  782  and the insulative body  770  may be monolithic, i.e., formed as a single piece. However, the isolation gasket  782  is preferably separate from the insulative body  770  so that it may be easily removed for replacement or cleaning. 
     While FIG. 10 shows a preferred embodiment of the isolation gasket  782  wherein the isolation gasket is seated entirely on the insulative body  770 , FIGS. 8 and 9 show an alternative embodiment. In the latter embodiment, the insulative body  770  is partially machined away to expose the upper surface of the connecting member  776  and the isolation gasket  782  is disposed thereon. Thus, the isolation gasket  782  contacts a portion of the connecting member  776 . This design requires less material to be used for the inner contact pads  772  which may be advantageous where material costs are significant such as when the inner contact pads  772  comprise gold. Persons skilled in the art will recognize other embodiments which do not depart from the scope of the present invention. 
     During processing, the isolation gasket  782  maintains contact with a peripheral portion of the substrate plating surface and is compressed to provide a seal between the remaining cathode contact ring  466  and the substrate. The seal prevents the electrolyte from contacting the edge and backside of the substrate. As noted above, maintaining a clean contact surface is necessary to achieving high plating repeatability. Previous contact ring designs did not provide consist plating results because contact surface topography varied over time. The contact ring of the present invention eliminates, or least minimizes, deposits which would otherwise accumulate on the inner contact pads  772  and change their characteristics thereby producing highly repeatable, consistent, and uniform plating across the substrate plating surface. 
     FIG. 11 is a simplified schematic diagram representing a possible configuration of the electrical circuit for the contact ring  466 . To provide a uniform current distribution between the conducting members  765 , an external resistor  700  is connected in series with each of the conducting members  765 . Preferably, the resistance value of the external resistor  700  (represented as R EXT ) is much greater than the resistance of any other component of the circuit. As shown in FIG. 11, the electrical circuit through each conducting member  765  is represented by the resistance of each of the components connected in series with the power supply  702 . R E  represents the resistance of the electrolyte, which is typically dependent on the distance between the anode and the cathode contact ring and the composition of the electrolyte chemistry. Thus, R A  represents the resistance of the electrolyte adjacent the substrate plating surface  754 . R S  represents the resistance of the substrate plating surface  754 , and R C  represents the resistance of the cathode conducting members  765  plus the constriction resistance resulting at the interface between the inner contact pads  772  and the substrate plating layer  754 . Generally, the resistance value of the external resistor (R EXT ) is at least as much as ΣR (where ΣR equals the sum of R E , R A , R S  and R C ). Preferably, the resistance value of the external resistor (R EXT ) is much greater than ΣR such that ΣR is negligible and the resistance of each series circuit approximates R EXT    
     Typically, one power supply is connected to all of the outer contact pads  780  of the cathode contact ring  466 , resulting in parallel circuits through the inner contact pads  772 . However, as the inner contact pad-to-substrate interface resistance varies with each inner contact pad  772 , more current will flow, and thus more plating will occur, at the site of lowest resistance. However, by placing an external resistor in series with each conducting member  765 , the value or quantity of electrical current passed through each conducting member  765  becomes controlled mainly by the value of the external resistor. As a result, the variations in the electrical properties between each of the inner contact pads  772  do not affect the current distribution on the substrate, and a uniform current density results across the plating surface which contributes to a uniform plating thickness. The external resistors also provide a uniform current distribution between different substrates of a process-sequence. 
     Although the contact ring  466  of the present invention is designed to resist deposit buildup on the inner contact pads  772 , over multiple substrate plating cycles the substrate-pad interface resistance may increase, eventually reaching an unacceptable value. An electronic sensor/alarm  704  can be connected across the external resistor  700  to monitor the voltage/current across the external resistor to address this problem. If the voltage/current across the external resistor  700  falls outside of a preset operating range that is indicative of a high substrate-pad resistance, the sensor/alarm  704  triggers corrective measures such as shutting down the plating process until the problems are corrected by an operator. Alternatively, a separate power supply can be connected to each conducting member  765  and can be separately controlled and monitored to provide a uniform current distribution across the substrate. A very smart system (VSS) may also be used to modulate the current flow. The VSS typically comprises a processing unit and any combination of devices known in the industry used to supply and/or control current such as variable resistors, separate power supplies, etc. As the physiochemical, and hence electrical, properties of the inner contact pads  772  change over time, the VSS processes and analyzes data feedback. The data is compared to pre-established setpoints and the VSS then makes appropriate current and voltage alterations to ensure uniform deposition. 
     Referring to FIGS. 12 and 12A, the wafer holder  464  is preferably positioned above the cathode contact ring  466  and comprises a bladder assembly  470  that provides pressure to the backside of a wafer and ensures electrical contact between the wafer plating surface and the cathode contact ring  466 . The inflatable bladder assembly  470  is disposed on a wafer holder plate  832 . A bladder  836  disposed on a lower surface of the wafer holder plate  832  is thus located opposite and adjacent to the contacts on the cathode contact ring  466  with the substrate  821  interposed therebetween. A fluid source  838  supplies a fluid, i.e., a gas or liquid, to the bladder  836  allowing the bladder  836  to be inflated to varying degrees. 
     Referring now to FIGS. 12,  12 A, and  13 , the details of the bladder assembly  470  will be discussed. The wafer holder plate  832  is shown as substantially disc-shaped having an annular recess  840  formed on a lower surface and a centrally disposed vacuum port  841 . One or more inlets  842  are formed in the wafer holder plate  832  and lead into the relatively enlarged annular mounting channel  843  and the annular recess  840 . Quick-disconnect hoses  844  couple the fluid source  838  to the inlets  842  to provide a fluid thereto. The vacuum port  841  is preferably attached to a vacuum/pressure pumping system  859  adapted to selectively supply a pressure or create a vacuum at a backside of the substrate  821 . The pumping system  859 , shown in FIG. 12, comprises a pump  845 , a cross-over valve  847 , and a vacuum ejector  849  (commonly known as a venturi). One vacuum ejector that may be used to advantage in the present invention is available from SMC Pneumatics, Inc., of Indianapolis, Indiana. The pump  845  may be a commercially available compressed gas source and is coupled to one end of a hose  851 , the other end of the hose  851  being coupled to the vacuum port  841 . The hose  851  is split into a pressure line  853  and a vacuum line  855  having the vacuum ejector  849  disposed therein. Fluid flow is controlled by the cross-over valve  847  which selectively switches communication with the pump  845  between the pressure line  853  and the vacuum line  855 . Preferably, the cross-over valve has an OFF setting whereby fluid is restricted from flowing in either direction through hose  851 . A shut-off valve  861  disposed in hose  851  prevents fluid from flowing from pressure line  855  upstream through the vacuum ejector  849 . The desired direction of fluid flow is indicated by arrows. 
     Persons skilled in the art will readily appreciate other arrangements which do not depart from the spirit and scope of the present invention. For example, where the fluid source  838  is a gas supply it may be coupled to hose  851  thereby eliminating the need for a separate compressed gas supply, i.e., pump  845 . Further, a separate gas supply and vacuum pump may supply the backside pressure and vacuum conditions. While it is preferable to allow for both a backside pressure as well as a backside vacuum, a simplified embodiment may comprise a pump capable of supplying only a backside vacuum. However, as will be explained below, deposition uniformity may be improved where a backside pressure is provided during processing. Therefore, an arrangement such as the one described above including a vacuum ejector and a cross-over valve is preferred. 
     Referring now to FIGS. 12A and 14, a substantially circular ring-shaped manifold  846  is disposed in the annular recess  840 . The manifold  846  comprises a mounting rail  852  disposed between an inner shoulder  848  and an outer shoulder  850 . The mounting rail  852  is adapted to be at least partially inserted into the annular mounting channel  843 . A plurality of fluid outlets  854  formed in the manifold  846  provide communication between the inlets  842  and the bladder  836 . Seals  837 , such as O-rings, are disposed in the annular manifold channel  843  in alignment with the inlet  842  and outlet  854  and secured by the wafer holder plate  832  to ensure an airtight seal. Conventional fasteners (not shown) such as screws may be used to secure the manifold  846  to the wafer holder plate  832  via cooperating threaded bores (not shown) formed in the manifold  846  and the wafer holder plate  832 . 
     Referring now to FIG. 15, the bladder  836  is shown, in section, as an elongated substantially semi-tubular piece of material having annular lip seals  856 , or nodules, at each edge. In FIG. 12A, the lip seals  856  are shown disposed on the inner shoulder  848  and the outer shoulder  850 . A portion of the bladder  836  is compressed against the walls of the annular recess  840  by the manifold  846  which has a width slightly less (e.g. a few millimeters) than the annular recess  840 . Thus, the manifold  846 , the bladder  836 , and the annular recess  840  cooperate to form a fluid-tight seal. To prevent fluid loss, the bladder  836  is preferably comprised of some fluid impervious material such as silicon rubber or any comparable elastomer which is chemically inert with respect to the electrolyte and exhibits reliable elasticity. Where needed a compliant covering  857  may be disposed over the bladder  836 , as shown in FIG. 15, and secured by means of an adhesive or thermal bonding. The covering  857  preferably comprises an elastomer such as Viton™, buna rubber or the like, which may be reinforced by Kevlar™, for example. In one embodiment, the covering  857  and the bladder  836  comprise the same material. The covering  857  has particular application where the bladder  836  is liable to rupturing. Alternatively, the bladder  836  thickness may simply be increased during its manufacturing to reduce the likelihood of puncture. 
     The precise number of inlets  842  and outlets  854  may be varied according to the particular application without deviating from the present invention. For example, while FIG. 12 shows two inlets with corresponding outlets, an alternative embodiment could employ a single fluid inlet which supplies fluid to the bladder  836 . 
     In operation, the substrate  821  is introduced into the container body  802  by securing it to the lower side of the wafer holder plate  832 . This is accomplished by engaging the pumping system  159  to evacuate the space between the substrate  821  and the wafer holder plate  832  via port  841  thereby creating a vacuum condition. The bladder  836  is then inflated by supplying a fluid such as air or water from the fluid source  838  to the inlets  842 . The fluid is delivered into the bladder  836  via the manifold outlets  854 , thereby pressing the substrate  821  uniformly against the contacts of the cathode contact ring  466 . The electroplating process is then carried out. An electrolyte is then pumped into the process kit  420  toward the substrate  821  to contact the exposed substrate plating surface  820 . The power supply provides a negative bias to the substrate plating surface  820  via the cathode contact ring  466 . As the electrolyte is flowed across the substrate plating surface  820 , ions in the electrolytic solution are attracted to the surface  820  and deposit on the surface  820  to form the desired film. 
     Because of its flexibility, the bladder  836  deforms to accommodate the asperities of the substrate backside and contacts of the cathode contact ring  466  thereby mitigating misalignment with the conducting cathode contact ring  466 . The compliant bladder  836  prevents the electrolyte from contaminating the backside of the substrate  821  by establishing a fluid tight seal at a perimeter portion of a backside of the substrate  821 . Once inflated, a uniform pressure is delivered downward toward the cathode contact ring  466  to achieve substantially equal force at all points where the substrate  821  and cathode contact ring  466  interface. The force can be varied as a function of the pressure supplied by the fluid source  838 . Further, the effectiveness of the bladder assembly  470  is not dependent on the configuration of the cathode contact ring  466 . For example, while FIG. 12 shows a pin configuration having a plurality of discrete contact points, the cathode contact ring  466  may also be a continuous surface. 
     Because the force delivered to the substrate  821  by the bladder  836  is variable, adjustments can be made to the current flow supplied by the contact ring  466 . As described above, an oxide layer may form on the cathode contact ring  466  and act to restrict current flow. However, increasing the pressure of the bladder  836  may counteract the current flow restriction due to oxidation. As the pressure is increased, the malleable oxide layer is compromised and superior contact between the cathode contact ring  466  and the substrate  821  results. The effectiveness of the bladder  836  in this capacity may be further improved by altering the geometry of the cathode contact ring  466 . For example, a knife-edge geometry is likely to penetrate the oxide layer more easily than a dull rounded edge or flat edge. 
     Additionally, the fluid tight seal provided by the inflated bladder  836  allows the pump  845  to maintain a backside vacuum or pressure either selectively or continuously, before, during, and after processing. Generally, however, the pump  845  is run to maintain a vacuum only during the transfer of substrates to and from the electroplating process cell  240  because it has been found that the bladder  836  is capable of maintaining the backside vacuum condition during processing without continuous pumping. Thus, while inflating the bladder  836 , as described above, the backside vacuum condition is simultaneously relieved by disengaging the pumping system  859 , e.g., by selecting an OFF position on the cross-over valve  847 . Disengaging the pumping system  859  may be abrupt or comprise a gradual process whereby the vacuum condition is ramped down. Ramping allows for a controlled exchange between the inflating bladder  836  and the simultaneously decreasing backside vacuum condition. This exchange may be controlled manually or by computer. 
     As described above, continuous backside vacuum pumping while the bladder  836  is inflated is not needed and may actually cause the substrate  820  to buckle or warp leading to undesirable deposition results. It may, however, be desirable to provide a backside pressure to the substrate  820  in order to cause a “bowing” effect of the substrate to be processed. The inventors of the present invention have discovered that bowing results in superior deposition. Thus, pumping system  859  is capable of selectively providing a vacuum or pressure condition to the substrate backside. For a 200 mm wafer a backside pressure up to 5 psi is preferable to bow the substrate. Because substrates typically exhibit some measure of pliability, a backside pressure causes the substrate to bow or assume a convex shape relative to the upward flow of the electrolyte. The degree of bowing is variable according to the pressure supplied by pumping system  859 . 
     Those skilled in the art will readily recognize other embodiments which are contemplated by the present invention. For example, while FIG. 12A shows a preferred bladder  836  having a surface area sufficient to cover a relatively small perimeter portion of the substrate backside at a diameter substantially equal to the cathode contact ring  466 , the bladder assembly  470  may be geometrically varied. Thus, the bladder assembly may be constructed using more fluid impervious material to cover an increased surface area of the substrate  821 . 
     Referring back to FIG.  6 ,a cross sectional view of an electroplating process cell  240 , the wafer holder assembly  450  is positioned above the process kit  420 . The process kit  420  generally comprises a bowl  430 , a container body  472 , an anode assembly  474  and a filter  476 . Preferably, the anode assembly  474  is disposed below the container body  472  and attached to a lower portion of the container body  472 , and the filter  476  is disposed between the anode assembly  474  and the container body  472 . The container body  472  is preferably a cylindrical body comprised of an electrically insulative material, such as ceramics, plastics, plexiglass (acrylic), lexane, PVC, CPVC, and PVDF. Alternatively, the container body  472  can be made from a metal, such as stainless steel, nickel and titanium, which is coated with an insulating layer, such as teflon, PVDF, plastic, rubber and other combinations of materials that do not dissolve in the electrolyte and can be electrically insulated from the electrodes (i.e., the anode and cathode of the electroplating system). The container body  472  is preferably sized and adapted to conform to the wafer plating surface and the shape of the of a wafer being processed through the system, typically circular or rectangular in shape. One preferred embodiment of the container body  472  comprises a cylindrical ceramic tube having an inner diameter that has about the same dimension as or slightly larger than the wafer diameter. The inventors have discovered that the rotational movement typically required in typical electroplating systems is not required to achieve uniform plating results when the size of the container body conforms to about the size of the wafer plating surface. 
     An upper portion of the container body  472  extends radially outwardly to form an annular weir  478 . The weir  478  extends over the inner wall  446  of the electrolyte collector  440  and allows the electrolyte to flow into the electrolyte collector  440 . The upper surface of the weir  478  preferably matches the lower surface of the cathode contact ring  466 . Preferably, the upper surface of the weir  478  includes an inner annular flat portion  480 , a middle inclined portion  482  and an outer declined portion  484 . When a wafer is positioned in the processing position, the wafer plating surface is positioned above the cylindrical opening of the container body  472 , and a gap for electrolyte flow is formed between the lower surface of the cathode contact ring  466  and the upper surface of the weir  478 . The lower surface of the cathode contact ring  466  is disposed above the inner flat portion  480  and the middle inclined portion of the weir  478 . The outer declined portion  484  is sloped downwardly to facilitate flow of the electrolyte into the electrolyte collector  440 . 
     A lower portion of the container body  472  extends radially outwardly to form a lower annular flange  486  for securing the container body  472  to the bowl  430 . The outer dimension (i.e., circumference) of the annular flange  486  is smaller than the dimensions of the opening  444  and the inner circumference of the electrolyte collector  440  to allow removal and replacement of the process kit  420  from the electroplating process cell  240 . Preferably, a plurality of bolts  488  are fixedly disposed on the annular flange  486  and extend downwardly through matching bolt holes on the bowl  430 . A plurality of removable fastener nuts  490  secure the process kit  420  onto the bowl  430 . A seal  487 , such as an elastomer O-ring, is disposed between container body  472  and the bowl  430  radially inwardly from the bolts  488  to prevent leaks from the process kit  420 . The nuts/bolts combination facilitates fast and easy removal and replacement of the components of the process kit  420  during maintenance. 
     Preferably, the filter  476  is attached to and completely covers the lower opening of the container body  472 , and the anode assembly  474  is disposed below the filter  476 . A spacer  492  is disposed between the filter  476  and the anode assembly  474 . Preferably, the filter  476 , the spacer  492 , and the anode assembly  474  are fastened to a lower surface of the container body  472  using removable fasteners, such as screws and/or bolts. Alternatively, the filter  476 , the spacer  492 , and the anode assembly  474  are removably secured to the bowl  430 . 
     The anode assembly  474  preferably comprises a consumable anode that serves as a metal source in the electrolyte. Alternatively, the anode assembly  474  comprises a non-consumable anode, and the metal to be electroplated is supplied within the electrolyte from the electrolyte replenishing system  220 . As shown in FIG. 6, the anode assembly  474  is a self-enclosed module having a porous anode enclosure  494  preferably made of the same metal as the metal to be electroplated, such as copper. Alternatively, the anode enclosure  494  is made of porous materials, such as ceramics or polymeric membranes. A soluble metal  496 , such as high purity copper for electrochemical deposition of copper, is disposed within the anode enclosure  494 . The soluble metal  496  preferably comprises metal particles, wires or a perforated sheet. The porous anode enclosure  494  also acts as a filter that keeps the particulates generated by the dissolving metal within the anode enclosure  494 . As compared to a non-consumable anode, the consumable (i.e., soluble) anode provides gas-generation-free electrolyte and minimizes the need to constantly replenish the metal in the electrolyte. 
     An anode electrode contact  498  is inserted into the anode enclosure  494  to provide electrical connection to the soluble metal  496  from a power supply. Preferably, the anode electrode contact  498  is made from a conductive material that is insoluble in the electrolyte, such as titanium, platinum and platinum-coated stainless steel. The anode electrode contact  498  extends through the bowl  430  and is connected to an electrical power supply. Preferably, the anode electrical contact  498  includes a threaded portion  497  for a fastener nut  499  to secure the anode electrical contact  498  to the bowl  430 , and a seal  495 , such as a elastomer washer, is disposed between the fastener nut  499  and the bowl  430  to prevent leaks from the process kit  420 . 
     The bowl  430  generally comprises a cylindrical portion  502  and a bottom portion  504 . An upper annular flange  506  extends radially outwardly from the top of the cylindrical portion  502 . The upper annular flange  506  includes a plurality of holes  508  that matches the number of bolts  488  from the lower annular flange  486  of the container body  472 . To secure the upper annular flange  506  of the bowl  430  and the lower annular flange  486  of the container body  472 , the bolts  488  are inserted through the holes  508 , and the fastener nuts  490  are fastened onto the bolts  488 . Preferably, the outer dimension (i.e., circumference) of the upper annular flange  506  is about the same as the outer dimension (i.e., circumference) of the lower annular flange  486 .Preferably, the lower surface of the upper annular flange  506  of the bowl  430  rests on a support flange of the mainframe  214  when the process kit  420  is positioned on the mainframe  214 . 
     The inner circumference of the cylindrical portion  502  accommodates the anode assembly  474  and the filter  476 . Preferably, the outer dimensions of the filter  476  and the anode assembly  474  are slightly smaller than the inner dimension of the cylindrical portion  502  to force a substantial portion of the electrolyte to flow through the anode assembly  474  first before flowing through the filter  476 . The bottom portion  504  of the bowl  430  includes an electrolyte inlet  510  that connects to an electrolyte supply line from the electrolyte replenishing system  220 . Preferably, the anode assembly  474  is disposed about a middle portion of the cylindrical portion  502  of the bowl  430  to provide a gap for electrolyte flow between the anode assembly  474  and the electrolyte inlet  510  on the bottom portion  504 . 
     The electrolyte inlet  510  and the electrolyte supply line are preferably connected by a releasable connector that facilitates easy removal and replacement of the process kit  420 . When the process kit  420  needs maintenance, the electrolyte is drained from the process kit  420 , and the electrolyte flow in the electrolyte supply line is discontinued and drained. The connector for the electrolyte supply line is released from the electrolyte inlet  510 , and the electrical connection to the anode assembly  474  is also disconnected. The head assembly  410  is raised or rotated to provide clearance for removal of the process kit  420 . The process kit  420  is then removed from the mainframe  214 , and a new or reconditioned process kit is replaced into the mainframe  214 . 
     Alternatively, the bowl  430  can be secured onto the support flange of the mainframe  214 , and the container body  472  along with the anode and the filter are removed for maintenance. In this case, the nuts securing the anode assembly  474  and the container body  472  to the bowl  430  are removed to facilitate removal of the anode assembly  474  and the container body  472 . New or reconditioned anode assembly  474  and container body  472  are then replaced into the mainframe  214  and secured to the bowl  430 . 
     FIG. 16 is a schematic diagram of an electrolyte replenishing system  220 . The electrolyte replenishing system  220  provides the electrolyte to the electroplating process cells for the electroplating process. The electrolyte replenishing system  220  generally comprises a main electrolyte tank  602 , a dosing module  603 , a filtration module  605 , a chemical analyzer module  616 , and an electrolyte waste disposal system  622  connected to the analyzing module  6161  by an electrolyte waste drain  620 . One or more controllers control the composition of the electrolyte in the main tank  602  and the operation of the electrolyte replenishing system  220 . Preferably, the controllers are independently operable but integrated with the control system  222  of the electroplating system platform  200 . 
     The main electrolyte tank  602  provides a reservoir for electrolyte and includes an electrolyte supply line  612  that is connected to each of the electroplating process cells through one or more fluid pumps  608  and valves  607 . A heat exchanger  624  or a heater/chiller disposed in thermal connection with the main tank  602  controls the temperature of the electrolyte stored in the main tank  602 . The heat exchanger  624  is connected to and operated by the controller  610 . 
     The dosing module  603  is connected to the main tank  602  by a supply line and includes a plurality of source tanks  606 , or feed bottles, a plurality of valves  609 , and a controller  611 . The source tanks  606  contain the chemicals needed for composing the electrolyte and typically include a deionized water source tank and copper sulfate (CUSO 4 ) source tank for composing the electrolyte. Other source tanks  606  may contain hydrogen sulfate (H 2 SO 4 ), hydrogen chloride (HCl) and various additives such as glycol. The deionized water source tank preferably also provides deionized water to the system for cleaning the system during maintenance. The valves  609  associated with each source tank  606  regulate the flow of chemicals to the main tank  602  and may be any of numerous commercially available valves such as butterfly valves, throttle valves and the like. Activation of the valves  609  is accomplished by the controller  611  which is preferably connected to the system control  222  to receive signals therefrom. 
     The electrolyte filtration module  605  includes a plurality of filter tanks  604 . An electrolyte return line  614  is connected between each of the process cells and one or more filter tanks  604 . The filter tanks  604  remove the undesired contents in the used electrolyte before returning the electrolyte to the main tank  602  for re-use. The main tank  602  is also connected to the filter tanks  604  to facilitate re-circulation and filtration of the electrolyte in the main tank  602 . By re-circulating the electrolyte from the main tank  602  through the filter tanks  604 , the undesired contents in the electrolyte are continuously removed by the filter tanks  604  to maintain a consistent level of purity. Additionally, re-circulating the electrolyte between the main tank  602  and the filtration module  605  allows the various chemicals in the electrolyte to be thoroughly mixed. 
     The electrolyte replenishing system  220  also includes a chemical analyzer module  616  that provides real-time chemical analysis of the chemical composition of the electrolyte. The analyzer module  616  is fluidly coupled to the main tank  602  by a sample line  613  and to the waste disposal system  622  by an outlet line  621 . The analyzer module  616  generally comprises at least one analyzer and a controller to operate the analyzer. The number of analyzers required for a particular processing tool depends on the composition of the electrolyte. For example, while a first analyzer may be used to monitor the concentrations of organic substances, a second analyzer is needed for inorganic chemicals. In the specific embodiment shown in FIG. 16 the chemical analyzer module  616  comprises an auto titration analyzer  615  and a cyclic voltametric stripper (CVS)  617 . Both analyzers are commercially available from various suppliers. An auto titration analyzer which may be used to advantage is available from Parker Systems and a cyclic voltametric stripper is available from ECI. The auto titration analyzer  615  determines the concentrations of inorganic substances such as copper chloride and acid. The CVS  617  determines the concentrations of organic substances such as the various additives which may be used in the electrolyte and by-products resulting from the processing which are returned to the main tank  602  from the process cells. 
     The analyzer module shown FIG. 16 is merely illustrative. In another embodiment each analyzer may be coupled to the main electrolyte tank by a separate supply line and be operated by separate controllers. Persons skilled in the art will recognize other embodiments. 
     In operation, a sample of electrolyte is flowed to the analyzer module  616  via the sample line  613 . Although the sample may be taken periodically, preferably a continuous flow of electrolyte is maintained to the analyzer module  616 . A portion of the sample is delivered to the auto titration analyzer  615  and a portion is delivered to the CVS  617  for the appropriate analysis. The controller  619  initiates command signals to operate the analyzers  615 ,  617  in order to generate data. The information from the chemical analyzers  615 ,  617  is then communicated to the control system  222 . The control system  222  processes the information and transmits signals which include user-defined chemical dosage parameters to the dosing controller  611 . The received information is used to provide real-time adjustments to the source chemical replenishment rates by operating one or more of the valves  609  thereby maintaining a desired, and preferably constant, chemical composition of the electrolyte throughout the electroplating process. The waste electrolyte from the analyzer module is then flowed to the waste disposal system  622  via the outlet line  621 . 
     Although a preferred embodiment utilizes real-time monitoring and adjustments of the electrolyte, various alternatives may be employed according to the present invention. For example, the dosing module  603  may be controlled manually by an operator observing the output values provided by the chemical analyzer module  616 . Preferably, the system software allows for both an automatic real-time adjustment mode as well as an operator (manual) mode. Further, although multiple controllers are shown in FIG. 16, a single controller may be used to operate various components of the system such as the chemical analyzer module  616 , the dosing module  603 , and the heat exchanger  624 . Other embodiments will be apparent to those skilled in the art. 
     The electrolyte replenishing system  220  also includes an electrolyte waste drain  620  connected to an electrolyte waste disposal system  622  for safe disposal of used electrolytes, chemicals and other fluids used in the electroplating system. Preferably, the electroplating cells include a direct line connection to the electrolyte waste drain  620  or the electrolyte waste disposal system  622  to drain the electroplating cells without returning the electrolyte through the electrolyte replenishing system  220 . The electrolyte replenishing system  220  preferably also includes a bleed off connection to bleed off excess electrolyte to the electrolyte waste drain  620 . 
     Although not shown in FIG. 16, the electrolyte replenishing system  220  may include a number of other components. For example, the electrolyte replenishing system  220  preferably also includes one or more additional tanks for storage of chemicals for a wafer cleaning system, such as the SRD station. Double-contained piping for hazardous material connections may also be employed to provide safe transport of the chemicals throughout the system. Optionally, the electrolyte replenishing system  220  includes connections to additional or external electrolyte processing system to provide additional electrolyte supplies to the electroplating system. 
     Referring back to FIG. 2, the electroplating system platform  200  includes a control system  222  that controls the functions of each component of the platform. Preferably, the control system  222  is mounted above the mainframe  214  and comprises a programmable microprocessor. The programmable microprocessor is typically programmed using a software designed specifically for controlling all components of the electroplating system platform  200 . The control system  222  also provides electrical power to the components of the system and includes a control panel  223  that allows an operator to monitor and operate the electroplating system platform  200 . The control panel  223 , as shown in FIG. 2, is a stand-alone module that is connected to the control system  222  through a cable and provides easy access to an operator. Generally, the control system  222  coordinates the operations of the loading station  210 , the SRD station  212 , the mainframe  214  and the processing stations  218 . Additionally, the control system  222  coordinates with the controller of the electrolyte replenishing system  220  to provide the electrolyte for the electroplating process. 
     The following is a description of a typical wafer electroplating process sequence through the electroplating system platform  200  as shown in FIG. 2. A wafer cassette containing a plurality of wafers is loaded into the wafer cassette receiving areas  224  in the loading station  210  of the electroplating system platform  200 . A loading station transfer robot  228  picks up a wafer from a wafer slot in the wafer cassette and places the wafer in the wafer orientor  230 . The wafer orientor  230  determines and orients the wafer to a desired orientation for processing through the system. The loading station transfer robot  228  then transfers the oriented wafer from the wafer orientor  230  and positions the wafer in one of the wafer slots in the wafer pass-through cassette  238  in the SRD station  212 . The mainframe transfer robot  242  picks up the wafer from the wafer pass-through cassette  238  and positions the wafer for transfer by the flipper robot  248 . The flipper robot  248  rotates its robot blade below the wafer and picks up wafer from mainframe transfer robot blade. The vacuum suction gripper on the flipper robot blade secures the wafer on the flipper robot blade, and the flipper robot flips the wafer from a face up position to a face down position. The flipper robot  248  rotates and positions the wafer face down in the wafer holder assembly  450 . The wafer is positioned below the wafer holder  464  but above the cathode contact ring  466 . The flipper robot  248  then releases the wafer to position the wafer into the cathode contact ring  466 . The wafer holder  464  moves toward the wafer and the vacuum chuck secures the wafer on the wafer holder  464 . The bladder assembly  470  on the wafer holder assembly  450  exerts pressure against the wafer backside to ensure electrical contact between the wafer plating surface and the cathode contact ring  466 . 
     The head assembly  452  is lowered to a processing position above the process kit  420 . At this position the wafer is below the upper plane of the weir  478  and contacts the electrolyte contained in the process kit  420 . The power supply is activated to supply electrical power (i.e., voltage and current) to the cathode and the anode to enable the electroplating process. The electrolyte is typically continually pumped into the process kit during the electroplating process. The electrical power supplied to the cathode and the anode and the flow of the electrolyte are controlled by the control system  222  to achieve the desired electroplating results. After the electroplating process is completed, the head assembly  410  raises the wafer holder assembly and removes the wafer from the electrolyte. The vacuum chuck and the bladder assembly of the wafer holder release the wafer from the wafer holder, and the wafer holder is raised to allow the flipper robot blade to pick up the processed wafer from the cathode contact ring. The flipper robot rotates the flipper robot blade above the backside of the processed wafer in the cathode contact ring and picks up the wafer using the vacuum suction gripper on the flipper robot blade. The flipper robot rotates the flipper robot blade with the wafer out of the wafer holder assembly, flips the wafer from a face-down position to a face-up position, and positions the wafer on the mainframe transfer robot blade. The mainframe transfer robot then transfers and positions the processed wafer above the SRD module  236 . The SRD wafer support lifts the wafer, and the mainframe transfer robot blade retracts away from the SRD module  236 . The wafer is cleaned in the SRD module using deionized water or a combination of deionized water and a cleaning fluid as described in detail above. The wafer is then positioned for transfer out of the SRD module. The loading station transfer robot  228  picks up the wafer from the SRD module  236  and transfers the processed wafer into the wafer cassette for removal from the electroplating system. The above-described sequence can be carried out for a plurality of wafers simultaneously in the electroplating system platform  200  of the present invention. While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims which follow.