Patent Publication Number: US-6699373-B2

Title: Apparatus for processing the surface of a microelectronic workpiece

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 09/386,197 filed on Aug. 31, 1999, now U.S. Pat. No. 6,303,010, which is a continuation application of International PCT Patent application No. PCT/US99/15847, filed on Jul. 12, 1999, which claims priority to U.S. patent application Ser. No. 09/113,723, filed Jul. 10, 1998, now U.S. Pat. No. 6,080,291, which is a CIP of U.S. patent Application Ser. No. 60/111,232, filed Dec. 7, 1998, and U.S. Patent Application Ser. No. 60/119,668, filed on Feb. 11, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     Production of semiconductor integrated circuits and other microelectronic devices from workpieces such as semiconductor wafers typically requires formation of one or more metal layers on the wafer. These metal layers are used, for example, to electrically interconnect the various devices of the integrated circuit. Further, the structures formed from the metal layers may constitute microelectronic devices such as read/write heads, etc. 
     The microelectronic manufacturing industry has applied a wide range of metals to form such structures. These metals include, for example, nickel, tungsten, solder, platinum, and copper. Further, a wide range of processing techniques have been used to deposit such metals. These techniques include, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, and electroless plating. Of these techniques, electroplating and electroless plating tend to be the most economical and, as such, the most desirable. Electroplating and electroless plating can be used in the deposition of blanket metal layers as well as patterned metal layers. 
     One of the most popular process sequences used by the microelectronic manufacturing industry to deposit a metal onto semiconductor wafers is referred to as “damascene” processing. In such processing holes, commonly called “vias”, trenches and/or other recesses are formed onto a workpiece and filled with a metal, such as copper. In the damascene process, the wafer is first provided with a metallic seed layer which is used to conduct electrical current during a subsequent metal electroplating step. If a metal such as copper is used, the seed layer is disposed over a barrier layer material, such as Ti, TiN, etc. The seed layer is a very thin layer of metal which can be applied using one or more of several processes. For example, the seed layer of metal can be laid down using physical vapor deposition or chemical vapor deposition processes to produce a layer on the order of 1,000 angstroms thick. The seed layer can advantageously be formed of copper, gold, nickel, palladium, or other metals. The seed layer is formed over a surface which is convoluted by the presence of the vias, trenches, or other recessed device features. 
     A metal layer is then electroplated onto the seed layer in the form of a blanket layer. The blanket layer is plated to form an overlying layer, with the goal of providing a metal layer that fills the trenches and vias and extends a certain amount above these features. Such a blanket layer will typically have a thickness on the order of 10,000 to 15,000 angstroms (1-1.5 microns). 
     After the blanket layer has been electroplated onto the semiconductor wafer, excess metal material present outside of the vias, trenches, or other recesses is removed. The metal is removed to provide a resulting pattern of metal layer in the semiconductor integrated circuit being formed. The excess plated material can be removed, for example, using chemical mechanical planarization. Chemical mechanical planarization is a processing step which uses the combined action of a chemical removal agent and an abrasive which grinds and polishes the exposed metal surface to remove undesired parts of the metal layer applied in the electroplating step. 
     The electroplating of the semiconductor wafers takes place in a reactor assembly. In such an assembly an anode electrode is disposed in a plating bath, and the wafer with the seed layer thereon is used as a cathode. Only a lower face of the wafer contacts the surface of the plating bath. The wafer is held by a support system that also conducts the requisite electroplating power (e.g., cathode current) to the wafer. The support system may comprise conductive fingers that secure the wafer in place and also contact the wafer seed layer in order to conduct electrical current for the plating operation. One embodiment of a reactor assembly is disclosed in U.S. Ser. No. 08/988,333 filed Sep. 30, 1997 entitled “Semiconductor Plating System Workpiece Support Having Workpiece—Engaging Electrodes With Distal Contact Part and Dielectric Cover.” 
     Several technical problems must be overcome in designing reactors used in the electroplating of semiconductor wafers. Utilization of a small number of discrete electrical contacts (e.g., 6 contacts) with the seed layer about the perimeter of the wafer ordinarily produces higher current densities near the contact points than at other portions of the wafer. This non-uniform distribution of current across the wafer, in turn, causes non-uniform deposition of the plated metallic material. Current thieving, effected by the provision of electrically-conductive elements other than those which contact the seed layer, can be employed near the wafer contacts to minimize such non-uniformity. But such thieving techniques add to the complexity of electroplating equipment, and increase maintenance requirements. 
     Another problem with electroplating of wafers concerns efforts to prevent the electric contacts themselves from being plated during the electroplating process. Any material plated to the electrical contacts must be removed to prevent changing contact performance. While it is possible to provide sealing mechanisms for discrete electrical contacts, such arrangements typically cover a significant area of the wafer surface, and can add complexity to the electrical contact design. 
     In addressing a further problem, it is sometimes desirable to prevent electroplating on the exposed barrier layer near the edge of the semiconductor wafer. Electroplated material may not adhere well to the exposed barrier layer material, and is therefore prone to peeling off in subsequent wafer processing steps. Further, metal that is electroplated onto the barrier layer within the reactor may flake off during the electroplating process thereby adding particulate contaminants to the electroplating bath. Such contaminants can adversely affect the overall electroplating process. 
     The specific metal to be electroplated can also complicate the electroplating process. For example, electroplating of certain metals typically requires use of a seed layer having a relatively high electrical resistance. As a consequence, use of the typical plurality of electrical wafer contacts (for example, six (6) discrete contacts) may not provide adequate uniformity of the plated metal layer on the wafer. 
     Beyond the contact related problems discussed above, there are also other problems associated with electroplating reactors. As device sizes decrease, the need for tighter control over the processing environment increases. This includes control over the contaminants that affect the electroplating process. The moving components of the reactor, which tend to generate such contaminants, should therefore be subject to strict isolation requirements. 
     Still further, existing electroplating reactors are often difficult to maintain and/or reconfigure for different electroplating processes. Such difficulties must be overcome if an electroplating reactor design is to be accepted for large-scale manufacturing. 
     One aspect of the present invention is directed to an improved electroplating apparatus having one or more of the following features: an improved workpiece contact assembly, a processing head having a quick-disconnect contact assembly construction, and/or a processing head having effective isolation of the moving components from the processing environment. 
     One drawback associated with copper deposition by electroplating is the fact that for very small features on microelectronic workpieces (sub 0.1 micron features), copper deposition by electroplating can lack conformality with the side walls of high aspect ratio vias and trenches, and can produce voids in the formed interconnects and plugs (vias). This is often due to the non-conformality of the copper seed layer deposited by PVD or CVD as a result, the seed layer may not be thick enough to carry the current to the bottom of high aspect ratio features. 
     An alternate process for depositing copper onto a microelectronic workpiece is known as “electroless” plating. A method of electroless plating of copper metallization onto microelectronic workpieces is disclosed in the article “Sub-Half Micron Electroless Cu Metallization,” by V. M. Dubin, et al., as published in the Materials Research Society Symposium Proceedings, volume 427, Advances Metallization For Future ULSI, 1996, herein incorporated by reference. The article describes the potential advantages of electroless Cu metallization as including lower tool costs, lower processing temperatures, higher quality deposits, superior uniformity of plating, and better via/trench filling capability. 
     According to the disclosed procedure, a blanket electroless Cu deposition was performed for via and trench filling on a workpiece having a Cu seed layer. The Cu seed layer was previously deposited by sputtering or contact displacement (wet activation process). An aluminum sacrificial layer was sputtered onto the Cu seed layer. Collimated Ti/N, uncollimated Ti, and uncollimated. Ta were used as diffusion barrier/adhesion promoter layers. After the electroless deposition of the Cu layer, chemical/mechanical polishing of the copper layer was performed to obtain inlaid copper metallization. A selective electroless CoW passivation layer was deposited on the inlaid Cu metallization. 
     According to the method disclosed in the foregoing article, the etching of the Al sacrificial layer in the same electroless Cu plating bath without transferring the wafer results in the catalytic Cu surface not being exposed to air. This purportedly avoids oxidation before the electroless Cu deposition is undertaken. After etching of the Al sacrificial seed layer, the catalytic seed layer acts as a catalytic material for electroless Cu deposition. Also, according to the disclosed method, annealing of the seedibarrier layer system at 300° C. in a vacuum improved adhesion of the seed layer. 
     Additionally, a small amount of surfactant and stabilizer was added to the copper plating solution in order to control surface tension and to retard hydrogen inclusion in the deposits, as well as to increase solution stability. Examples of surfactants are: RE 610, polyethylenglycol, NCW-601A, Triton X-100. Examples of stabilizers disclosed are: Neocuproine, 2,2′ dipyridyl, CN-, Rhodanine. 
     Other patents which describe and teach electroless metallization techniques include U.S. Pat. Nos. 5,500,315; 5,310,580; 5,389,496; and 5,139,818, all of which are hereby incorporated by reference. 
     Whereas electroless plating of copper on microelectronic workpieces offers advantages, such as good conformality the electroless deposition rate of copper is generally lower than that produced by electroplating. Accordingly, another aspect of the present invention recognizes the 
     desirability of achieving the advantageous conformality of the deposited copper in small and/or high aspect ratio features, such as vias and trenches, while at the same time having an increased overall deposition rate for increased microelectronic production throughput. This aspect of the present invention also recognizes the desirability of providing an electroless plating reactor which can be incorporated into an automated microelectronic processing tool. 
     SUMMARY OF THE INVENTIONS 
     A reactor for plating a metal onto a surface of a workpiece is set forth. The reactor comprises a reactor bowl including an electroplating solution disposed therein and an anode disposed in the reactor bowl in contact with the electroplating solution. A contact assembly is spaced from the anode within the reactor bowl. The contact assembly includes a plurality of contacts disposed to contact a peripheral edge of the surface of the workpiece to provide electroplating power to the surface of the workpiece. The contacts execute a wiping action against the surface of the workpiece as the workpiece is brought into engagement therewith The contact assembly also including a barrier disposed interior of the plurality of contacts. The barrier includes a member disposed to engage the surface of the workpiece to assist in isolating the plurality of contacts from the electroplating solution. In one embodiment, the plurality of contacts are in the form of discrete flexures while in another embodiment, the plurality of contacts are in the form of a Belleville ring contact. A flow path may be provided in the contact assembly for providing a purging gas to the plurality of contacts and the peripheral edge of the workpiece. The purging gas may be used to assist in the formation of the barrier of the contact assembly. 
     In accordance with a further aspect of the present invention, the contact assembly is connected within the reactor assembly by one rmore latching mechanisms. The latching mechanisms allow easy replacement of the contact assembly with another contact assembly of the same or of a different type. Given the construction of the disclosed contact assemblies, replacement with the same type of contact assembly reduces or otherwise eliminates the need for recalibration of the plating system thereby reducing down time of the reactor. 
     In accordance with further aspect of the inventive reactor, the reactor may comprise a processing head including the contact assembly. More particularly, the processing head may include a stator portion and a rotor portion, the rotor portion comprising the contact assembly. The contact assembly may be detachably connected to the rotor portion by at least one latching mechanism. 
     The reactor as may also include a backing member and a drive mechanism in an assembly in which the backing member and contact assembly are moved relative to one another by the drive mechanism between a workpiece loading state and a workpiece processing state. In the workpiece processing state, the workpiece is urged against the plurality of contacts of the contact assembly by the backing member. To reduce the risk of contamination from particles released by the drive mechanism, the drive mechanism may be substantially surrounded by a bellows member. 
     An integrated tool for plating a workpiece is also set forth. The integrated tool comprises a first processing chamber for plating the workpiece using an electroless plating process and a second processing chamber for plating the workpiece using an electroplating process. A robotic transfer mechanism is used that is programmed to transfer a workpiece to the first processing chamber for electroless plating thereof and, in a subsequent operation, to transfer the workpiece to the second processing chamber for electroplating thereof. A plating process that may be implemented on the foregoing tool is set forth, although the disclosed process is independent of the processing tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view through an electroplating reactor that is constructed in accordance with various teachings of the present invention. 
     FIG. 2 illustrates a specific construction of one embodiment of a reactor bowl suitable for use in the assembly illustrated in FIG.  1 . 
     FIG. 3 illustrates one embodiment of a reactor head, comprised of a stationary assembly and a rotor assembly that is suitable for use in the assembly illustrated in FIG.  1 . 
     FIGS. 4-10 illustrate one embodiment of a contact assembly using flexure contacts that is suitable for use in the reactor assembly illustrated in FIG.  1 . 
     FIGS. 11-15 illustrate another embodiment of a contact assembly using flexure contacts that is suitable for use in the reactor assembly illustrated in FIG.  1 . 
     FIGS. 16-17 illustrate two different embodiments of a “Belleville ring” contact structure. 
     FIGS. 18-20 illustrate one embodiment of a contact assembly using a “Belleville ring” contact structure, such as one of those illustrated in FIGS. 15-17, that is suitable for use in the reactor assembly illustrated in FIG.  1 . 
     FIGS. 21-23 illustrate another embodiment of a contact assembly using a “Belleville ring” contact structure, such as one of those illustrated in FIGS. 15-17, that is suitable for use in the reactor assembly illustrated in FIG.  1 . 
     FIG. 24 illustrates another embodiment of a contact assembly using a “Belleville ring” contact structure, such as one of those illustrated in FIGS. 15-17, that is suitable for use in the reactor assembly illustrated in FIG.  1 . 
     FIG. 25 illustrates a still further embodiment of a contact assembly using a “Belleville ring” contact structure, such as one of those illustrated in FIGS. 15-17, that is suitable for use in the assembly illustrated in FIG.  1 . 
     FIGS. 26 and 27 illustrate another embodiment of a contact assembly that is suitable for use in the reactor assembly illustrated in FIG.  1 . 
     FIGS. 28-32 illustrate various aspects of one embodiment of a quick-attach mechanism. 
     FIG. 33 is a cross-sectional view of the reactor head illustrating the disposition of the reactor head in a condition in which it may accept a workpiece. 
     FIG. 34 is a cross-sectional view of the reactor head illustrating the disposition of the reactor head in a condition in which it is ready to present the workpiece to the reactor bowl. 
     FIG. 35 illustrates an exploded view one embodiment of the rotor assembly. 
     FIG. 36 is a cross-sectional view of one embodiment of an electroless plating reactor suitable for use in connection with the present inventions. 
     FIGS. 37-42 illustrate various embodiments of workpiece holders suitable for use in the electroless plating reactor of FIG.  36 . 
     FIGS. 44-46 illustrate one manner in which a purging gas, such as nitrogen, can be supplied to either a workpiece holder or contact assembly that is constructed in accordance with the disclosed embodiments. 
     FIGS. 47-49 are top plan views of integrated processing tools that may incorporate electroless plating reactors and electroplating reactors in combination. 
     FIG. 50 is a flow diagram illustrating a process for plating a workpiece that incorporates both electroless and electroplating steps. 
    
    
     DETAILED DESCRIPTION OF THE INVENTIONS 
     Basic Reactor Components 
     With reference to FIGS. 1-3, there is shown a reactor assembly  20  for electroplating a microelectronic workpiece, such as a semiconductor wafer  25 . Generally stated, the reactor assembly  20  is comprised of a reactor head  30  and a corresponding reactor bowl  35 . This type of reactor assembly is particularly suited for effecting electroplating of semiconductor wafers or like workpieces, in which an electrically conductive, thin-film layer of the wafer is electroplated with a blanket or patterned metallic layer. 
     The specific construction of one embodiment of a reactor bowl  35  suitable for use in the reactor assembly  20  is illustrated in FIG.  2 . The electroplating reactor bowl  35  is that portion of the reactor assembly  20  that contains electroplating solution, and that directs the solution against a generally downwardly facing surface of an associated workpiece  25  to be plated. To this end, electroplating solution is circulated through the reactor bowl  35 . Attendant to solution circulation, the solution flows from the reactor bowl  35 , over the weir-like periphery of the bowl, into a lower overflow chamber  40  of the reactor assembly  20 . Solution is drawn from the overflow chamber typically for re-circulation through the reactor. 
     The reactor bowl  35  includes a riser tube  45 , within which an inlet conduit  50  is positioned for introduction of electroplating solution into the reactor bowl  35 . The inlet conduit  50  is preferably conductive and makes electrical contact with and supports an electroplating anode  55 . The anode  55  may be provided with an anode shield  60 . Electroplating solution flows from the inlet conduit  50  through openings at the upper portion thereof, about the anode  55 , and through an optional diffusion plate  65  positioned in operative association with the anode. The anode  55  may be consumable whereby metal ions of the anode are transported by the electroplating solution to the electrically-conductive surface of the associated workpiece, which functions as a cathode. Alternatively, the anode  55  may be inert, thereby removing the need for the anode shield  60 . 
     As shown in FIGS. 1 and 3, the reactor head  30  of the electroplating reactor  20  is preferably comprised of a stationary assembly  70  and a rotor assembly  75 . Rotor assembly  75  is configured to receive and carry an associated wafer  25  or like workpiece, position the wafer in a process-side down orientation within reactor bowl  35 , and to rotate or spin the workpiece while joining its electrically-conductive surface in the plating circuit of the reactor assembly  20 . The reactor head  30  is typically mounted on a lift/rotate apparatus  80 , which is configured to rotate the reactor head  30  from an upwardly-facing disposition, wherein it receives the wafer to be plated, to a downwardly facing disposition, wherein the surface of the wafer to be plated is positioned downwardly in reactor bowl  35 , generally in confronting relationship to diffusion plate  65 . A robotic arm  415  (sometimes referred to as including an end effector) is typically employed for placing the wafer  25  in position on the rotor assembly  75 , and for removing the plated wafer from within the rotor assembly. 
     It will be recognized that other reactor assembly configurations may be used with the inventive aspects of the disclosed reactor head, the foregoing being merely illustrative. Another reactor assembly suitable for use in the foregoing configuration is illustrated in U.S. Ser. No. 09/112,300, filed Jul. 9, 1998, now U.S. Pat. No. 6,228,232, and incorporated herein by reference. A still further reactor assembly suitable for use in the foregoing configuration is illustrated in U.S. Ser. No. 60/120,955, filed Apr. 13, 1999, and incorporated herein by reference. 
     Improved Contact Assemblies 
     As noted above, the manner in which the electroplating power is supplied to the wafer at the peripheral edge thereof is very important to the overall film quality of the deposited metal. Some of the more desirable characteristics of a contact assembly used to provide such electroplating power include, for example, the following: 
     uniform distribution of electroplating power about the periphery of the wafer to maximize the uniformity of the deposited film; 
     consistent contact characteristics to insure wafer-to-wafer uniformity; 
     minimal intrusion of the contact assembly on the wafer periphery to maximize the available area for device production; and 
     minimal plating on the barrier layer about the wafer periphery to inhibit peeling and/or flaking. 
     To meet one or more of the foregoing characteristics, reactor  20  preferably employs a ring contact assembly  85  that provides either a continuous electrical contact or a high number of discrete electrical contacts with the wafer  25 . By providing a more continuous contact with the outer peripheral edges of the semiconductor wafer  25 , in this case around the outer circumference of the semiconductor wafer, a more uniform current is supplied to the semiconductor wafer  25  that promotes more uniform current densities. The more uniform current densities enhance uniformity in the depth of the deposited material. 
     Contact assembly  85 , in accordance with a preferred embodiment, includes contact members that provide minimal intrusion about the wafer periphery while concurrently providing consistent contact with the seed layer. Contact with the seed layer is enhanced by using a contact member structure that provides a wiping action against the seed layer as the wafer is brought into engagement with the contact assembly. This wiping action assists in removing any oxides at the seed layer surface thereby enhancing the electrical contact between the contact structure and the seed layer. As a result, uniformity of the current densities about the wafer periphery are increased and the resulting film is more uniform. Further, such consistency in the electrical contact facilitates greater consistency in the electroplating process from wafer-to-wafer thereby increasing wafer-to-wafer uniformity. 
     Contact assembly  85 , as will be set forth in further detail below, also preferably includes one or more structures that provide a barrier, individually or in cooperation with other structures, that separates the contact/contacts, the peripheral edge portions and backside of the semiconductor wafer  25  from the plating solution. This prevents the plating of metal onto the individual contacts and, further, assists in preventing any exposed portions of the barrier layer near the edge of the semiconductor wafer  25  from being exposed to the electroplating environment. As a result, plating of the barrier layer and the appertaining potential for contamination due to flaking of any loosely adhered electroplated material is substantially limited. 
     Ring Contact Assemblies Using Flexure Contacts 
     One embodiment of a contact assembly suitable for use in the assembly  20  is shown generally at  85  of FIGS. 4-10. The contact assembly  85  forms part of the rotor assembly  75  and provides electrical contact between the semiconductor wafer  25  and a source of electroplating power. In the illustrated embodiment, electrical contact between the semiconductor wafer  25  and the contact assembly  85  occurs at a large plurality of discrete flexure contacts  90  that are effectively separated from the electroplating environment interior of the reactor bowl  35  when the semiconductor wafer  25  is held and supported by the rotor assembly  75 . 
     The contact assembly  85  may be comprised of several discrete components. With reference to FIG. 4, when the workpiece that is to be electroplated is a circular semiconductor wafer, the discrete components of the contact assembly  85  join together to form a generally annular component having a bounded central open region  95 . It is within this bounded central open region  95  that the surface of the semiconductor wafer that is to be electroplated is exposed. With particular reference to FIG. 6, contact assembly  85  includes an outer body member  100 , an annular wedge  105 , a plurality of flexure contacts  90 , a contact mount member  110 , and an interior wafer guide  115 . Preferably, annular wedge  105 , flexure contacts  90 , and contact mount member  110  are formed from platinized titanium while wafer guide  115  and outer body member  100  are formed from a dielectric material that is compatible with the electroplating environment. Annular wedge  105 , flexure contacts  90 , mount member  110 , and wafer guide  115  join together to form a single assembly that is secured together by outer body member  100 . 
     As shown in FIG. 6, contact mount member  110  includes a first annular groove  120  disposed about a peripheral portion thereof and a second annular groove  125  disposed radially inward of the first annular groove  120 . The second annular groove  125  opens to a plurality of flexure channels  130  that are equal in number to the number of flexure contacts  90 . As can be seen from FIG. 4, a total of 36 flexure contacts  90  are employed, each being spaced from one another by an angle of about 10 degrees. 
     Referring again to FIG. 6, each flexure contact  90  is comprised of an upstanding portion  135 , a transverse portion  140 , a vertical transition portion  145 , and a wafer contact portion  150 . Similarly, wedge  105  includes an upstanding portion  155  and a transverse portion  160 . Upstanding portion  155  of wedge  105  and upstanding portion  135  of each flexure contact  90  are secured within the first annular groove  120  of the contact mount member  110  at the site of each flexure channel  130 . Self-adjustment of the flexure contacts  90  to their proper position within the overall contact assembly  85  is facilitated by first placing each of the individual flexure contacts  90  in its respective flexure channel  130  so that the upstanding portion  135  is disposed within the first annular groove  120  of the contact mount member  110  while the transition portion  145  and contact portion  150  proceed through the respective flexure channel  130 . The upstanding portion  155  of wedge member  105  is then urged into the first annular groove  120 . To assist in this engagement, the upper end of upstanding portion  155  is tapered. The combined width of upstanding portion  135  of the flexure contact  90  and upstanding portion  155  of wedge  105  are such that these components are firmly secured with contact mount member  110 . 
     Transverse portion  160  of wedge  105  extends along a portion of the length of transverse portion  140  of each flexure  90 . In the illustrated embodiment, transverse portion  160  of wedge portion  105  terminates at the edge of the second annular groove  125  of contact mount member  110 . As will be more clear from the description of the flexure contact operation below, the length of transverse portion  160  of wedge  105  can be chosen to provide the desired degree of stiffness of the flexure contacts  90 . 
     Wafer guide  115  is in the form of an annular ring having a plurality of slots  165  through which contact portions  150  of flexures  90  extend. An annular extension  170  proceeds from the exterior wall of wafer guide  115  and engages a corresponding annular groove  175  disposed in the interior wall of contact mount member  110  to thereby secure the wafer guide  115  with the contact mount member  110 . As illustrated, the wafer guide member  115  has an interior diameter that decreases from the upper portion thereof to the lower portion thereof proximate contact portions  150 . A wafer inserted into contact assembly  85  is thus guided into position with contact portions  150  by a tapered guide wall formed at the interior of wafer guide  115 . Preferably, the portion  180  of wafer guide  115  that extends below annular extension  170  is formed as a thin, compliant wall that resiliently deforms to accommodate wafers having different diameters within the tolerance range of a given wafer size. Further, such resilient deformation accommodates a range of wafer insertion tolerances occurring in the components used to bring the wafer into engagement with the contact portions  150  of the flexures  90 . 
     Referring to FIG. 6, outer body member  100  includes an upstanding portion  185 , a transverse portion  190 , a vertical transition portion  195  and a further transverse portion  200  that terminates in an upturned lip  205 . Upstanding portion  185  includes an annular extension  210  that extends radially inward to engage a corresponding annular notch  215  disposed in an exterior wall of contact mount member  110 . A V-shaped notch  220  is formed at a lower portion of the upstanding portion  185  and circumvents the outer periphery thereof. The V-shaped notch  220  allows upstanding portion  185  to resiliently deform during assembly. To this end, upstanding portion  185  resiliently deforms as annular extension  210  slides about the exterior of contact mount member  110  to engage annular notch  215 . Once so engaged, contact mount member  110  is clamped between annular extension  210  and the interior wall of transverse portion  190  of outer body member  100 . 
     Further transverse portion  200  extends beyond the length of contact portions  150  of the flexure contacts  90  and is dimensioned to resiliently deform as a wafer, such as at  25 , is driven against them. V-shaped notch  220  may be dimensioned and positioned to assist in the resilient deformation of transverse portion  200 . With the wafer  25  in proper engagement with the contact portions  150 , upturned lip  205  engages wafer  25  and assists in providing a barrier between the electroplating solution and the outer peripheral edge and backside of wafer  25 , including the flexure contacts  90 . 
     As illustrated in FIG. 6, flexure contacts  90  resiliently deform as the wafer  25  is driven against them. Preferably, contact portions  150  are initially angled upward in the illustrated manner. Thus, as the wafer  25  is urged against contact portions  150 , flexures  90  resiliently deform so that contact portions  150  effectively wipe against surface  230  of wafer  25 . In the illustrated embodiment, contact portions  150  effectively wipe against surface  230  of wafer  25  a horizontal distance designated at  235 . This wiping action assists in removing and/or penetrating any oxides from surface  230  of wafer  25  thereby providing more effective electrical contact between flexure contacts  90  and the seed layer at surface  230  of wafer  25 . 
     With reference to FIGS. 7 and 8, contact mount member  110  is provided with one or more ports  240  that may be connected to a source of purging gas, such as a source of nitrogen. As shown in FIG. 8, purge ports  240  open to second annular groove  125  which, in turn, operates as a manifold to distribute the purging gas to all of the flexure channels  130  as shown in FIG.  6 . The purging gas then proceeds through each of the flexure channels  130  and slots  165  to substantially surround the entire contact portions  150  of flexures  90 . In addition to purging the area surrounding contact portions  150 , the purge gas cooperates with the upturned lip  205  of outer body member  100  to effect a barrier to the electroplating solution. Further circulation of the purge gas is facilitated by an annular channel  250  formed between a portion of the exterior wall of wafer guide  115  and a portion of the interior wall of contact mount member  110 . 
     As shown in FIGS. 4,  5  and  10 , contact mount member  110  is provided with one or more threaded apertures  255  that are dimensioned to accommodate a corresponding connection plug  260 . With reference to FIGS. 5 and 10, connection plugs  260  provide electroplating power to the contact assembly  85  and, preferably, are each formed from platinized titanium. In a preferred form of plugs  260 , each plug  260  includes a body  265  having a centrally disposed bore hole  270 . A first flange  275  is disposed at an upper portion of body  265  and a second flange  280  is disposed at a lower portion of body  265 . A threaded extension  285  proceeds downward from a central portion of flange  280  and secures with threaded bore hole  270 . The lower surface of flange  280  directly abuts an upper surface of contact mount member  110  to increase the integrity of the electrical connection therebetween. 
     Although flexure contacts  90  are formed as discrete components, they may be joined with one another as an integral assembly. To this end, for example, the upstanding portions  135  of the flexure contacts  90  may be joined to one another by a web of material, such as platinized titanium, that is either formed as a separate piece or is otherwise formed with the flexures from a single piece of material. The web of material may be formed between all of the flexure contacts or between select groups of flexure contacts. For example, a first web of material may be used to join half of the flexure contacts (e.g., 18 flexure contacts in the illustrated embodiment) while a second web of material is used to join a second half of the flexure contacts (e.g., the remaining 18 flexure contacts in the illustrated embodiment). Different groupings are also possible. 
     A further embodiment of a contact assembly employing flexure contacts such as those described above is illustrated in FIGS. 11-15. As illustrated in FIG. 11, contact assembly  85   b  is again adapted to accommodate a semiconductor wafer and is in many respects similar to contact assembly  85  of FIGS. 4-10. Accordingly, components in contact assembly  85   b  are referenced using the same reference numbers associated with contact assembly  85 , except that the components of contact assembly  85   b  include a “b” suffix. 
     In this embodiment, with reference to FIG. 15, an outer body member  100   b  is formed from a plastic material or the like that is electrically non-conductive and is chemically compatible with the electroplating environment. The outer body member  100   b  is provided with an annular groove  290   b  into which is provided an O-ring  295   b . As will be explained in further detail below, the O-ring  295   b  seals against face  230   b  of the semiconductor wafer  25  to assist in preventing contact between the flexure contacts  90   b  and the electroplating environment within the reactor bowl  35 . 
     The contact assembly  85   b  also includes an annular stiffening ring  300   b , a contact mount member  110   b , and a plurality of flexure contacts  90   b . Contact mount member  110   b  is in the form of an annular ring having a plurality of slots  165   b  through which contact portions  150   b  of flexures  90   b  extend. As illustrated the contact mount member has an interior diameter distal contact portions  150   b  that is greater than the interior diameter proximate contact portions  150   b . A wafer inserted into the contact assembly  85   b  is thus guided into position with contact portions  150   b  by a tapered guide wall formed at the interior of contact mount member  110   b.    
     As above the flexure contacts  90  of the illustrated embodiment are formed as discrete components each having an upstanding portion  135   b , a transverse portion  140   b , a vertical transition portion  145   b , and a contact portion  150   b . The contact portions  50   b  protrude through respective ones of the plurality of slots  165   b.    
     Integration of the foregoing components to form the contact assembly  85   b , as well as the operation of the contact assembly, is best understood with reference again to FIG.  15 . In the illustrated embodiment, the various components are clamped together by the outer body member  100   b . As illustrated, contact mount member  110   b  and outer body member  100   b  define a plurality of flexure chambers, shown generally at  130   b . Each flexure chamber includes an upwardly extending portion  120   b  that is defined on each side by chamferred members  300   b  that extend radially outward from the inner body member  110   b . The chamferred members  300   b  are designed to be engaged by nose portion  210   b  of the outer body member  100   b  through a camming action whereby nose portion  210   b  clamps the contact mount member  110   b , transverse portions  140   b  of flexures  90   b  and annular stiffening ring  300   b  against a laterally extending portion  190   b  of the outer body member  100   b . Depending on the material from which the outer body member  100   b  is formed, it may be desirable to include a notch  220   b  in the outer body member  100   b  to facilitate the camming action of the nose portion  215   b  over the one or more chamferred members  160  and, if desired, resilient deformation of the outer body member  100   b  when wafer  25  is urged into operative relationship with the overall contact assembly  85   b.    
     Optionally, a non-reactive gas, such as nitrogen, can be used to purge the flexure contacts  90   b  and the back side of wafer  25 . To this end, the wafer guide  115   b  may be provided with one or more purge ports  240   b  that serve to provide fluid communication of a purging gas to an annular manifold.  125   b  and, therefrom, through the flexure chambers  130   b  so as to substantially surround contact portions  150   b . The purge gas then flows through openings  165   b  to the peripheral edge of the semiconductor wafer  25  and to backside of the semiconductor wafer. Such measures enhance the isolation of the flexure contacts  90   b  and the backside of the semiconductor wafer  25  from the processing environment. 
     In operation, the semiconductor wafer  25  is driven against the flexure contacts  90   b  so that a face  230   b  of the semiconductor wafer  25  is sealed against the O-ring and corresponding portion of the outer body member  100   b . When driven in this manner, each flexure contact  90  is driven a vertical distance and a horizontal distance  235   b . This movement causes the flexure contacts  90   b  to wipe against the side  230   b  of the semiconductor wafer  25  thereby assisting in the removal or penetration of, for example, seed layer oxides or the like and enhancing electrical contact between the flexure contacts  90   b  and the semiconductor wafer  25 . The amount of deflection and bias can be altered as a function of the radial width of the annular stiffening ring  300   b . A large deflection can be used to accommodate large manufacturing tolerance variations while still providing proper electrical contact as well as sealing of the contact assembly  85  against the semiconductor wafer  25 . 
     In the embodiment of contact assembly  85   b , the axial force applied to the semiconductor wafer  25  is divided between the force required to deflect the flexure contacts  90  and that required to energize the seal. This provides a load path that is independent of the structure, which contains the seal thereby isolating deflection of the contacts from dependency on the deflection of the O-ring  105  to form the seal. 
     Belleville Ring Contact Assemblies 
     Alternative contact assemblies are illustrated in FIGS. 16-25. In each of these contact assemblies, the contact members are integrated with a corresponding common ring and, when mounted in their corresponding assemblies, are biased upward in the direction in which the wafer or other substrate is received upon the contact members. A top view of one embodiment of such a structure is illustrated in FIG. 16A while a perspective view thereof is illustrated in FIG.  16 B. As illustrated, a ring contact, shown generally at  610 , is comprised of a common ring portion  630  that joins a plurality of contact members  655 . The common ring portion  630  and the contact members  655 , when mounted in the corresponding assemblies, are similar in appearance to half of a conventional Belleville spring. For this reason, the ring contact  610  will be hereinafter referred to as a “Bellville ring contact” and the overall contact assembly into which it is placed will be referred to as a “Bellville ring contact assembly”. 
     The embodiment of Belleville ring contact  610  illustrated in FIGS. 16A and 16B includes 72 contact members  655  and is preferably in formed from platinized titanium. The contact members  655  may be formed by cutting arcuate sections  657  into the interior diameter of a platinized titanium ring. A predetermined number of the contact members  658  have a greater length than the remaining contact members  655  to, for example, accommodate certain flat-sided wafers. 
     A further embodiment of a Belleville ring contact  610  is illustrated in FIG.  17 . As above, this embodiment is preferably formed from platinized titanium. Unlike the embodiment of FIGS. 16A and 16B in which all of the contact members  655  extend radially inward toward the center of the structure, this embodiment includes contact members  659  that are disposed at an angle. This embodiment constitutes a single-piece design that is easy to manufacture and that provides a more compliant contact than does the embodiment of FIGS. 16A and 16B with the same footprint. This contact embodiment can be fixtured into the “Belleville” form in the contact assembly and does not require permanent forming. If the Belleville ring contact  610  of this embodiment is fixtured in place, a complete circumferential structure is not required. Rather the contact may be formed and installed in segments thereby enabling independent control/sensing of the electrical properties of the segments. 
     A first embodiment of a Bellville ring contact assembly is illustrated generally at  600  in in FIGS. 18-20. As illustrated, the contact assembly  600  comprises a conductive contact mount member  605 , a Bellville ring contact  610 , a dielectric wafer guide ring  615 , and an outer body member  625 . The outer, common portion  630  of the Bellville ring contact  610  includes a first side that is engaged within a notch  675  of the conductive base ring  605 . In many respects, the Belleville ring contact assembly of this embodiment is similar in construction with the flexure contact assembly  85  described above. For that reason, the functionality of many of the structures of the contact assembly  600  will be apparent and will not be repeated here. 
     Preferably, the wafer guide ring  615  is formed from a dielectric material while contact mount member  605  is formed from a single, integral piece of conductive material or from a dielectric or other material that is coated with a conductive material at its exterior. Even more preferably, the conductive ring  605  and Bellville ring contact  610  are formed from platinized titanium or are otherwise coated with a layer of platinum. 
     The wafer guide ring  615  is dimensioned to fit within the interior diameter of the contact mount member  605 . Wafer guide ring  615  has substantially the same structure as wafer guides  115  and  115   b  described above in connection with contact assemblies  85  and  85   b , respectively. Preferably, the wafer guide ring  615  includes an annular extension  645  about its periphery that engages a corresponding annular slot  650  of the conductive base ring  605  to allow the wafer guide ring  615  and the contact mount member  605  to snap together. 
     The outer body member  625  includes an upstanding portion  627 , a transverse portion  629 , a vertical transition portion  632  and a further transverse portion  725  that extends radially and terminates at an upturned lip  730 . Upturned lip  730  assists in forming a barrier to the electroplating environment when it engages the surface of the side of workpiece  25  that is being processed. In the illustrated embodiment, the engagement between the lip  730  and the surface of workpiece  25  is the only mechanical seal that is formed to protect the Bellville ring contact  610 . 
     The area proximate the contacts  655  of the Belleville ring contact  610  is preferably purged with an inert fluid, such as nitrogen gas, which cooperates with lip  730  to effect a barrier between the Bellville ring contact  610 , peripheral portions and the backside of wafer  25 , and the electroplating environment. As particularly shown set forth in FIGS. 19 and 20, the outer body member  625  and contact mount member  605  are spaced from one another to form an annular cavity  765 . The annular cavity  765  is provided with an inert fluid, such as nitrogen, through one or more purge ports  770  disposed through the contact mount member  605 . The purged ports  770  open to the annular cavity  765 , which functions as a manifold to distribute to the inert gas about the periphery of the contact assembly. A given number of slots, such as at  780 , corresponding to the number of contact members  655  are provided and form passages that route the inert fluid from the annular cavity  765  to the area proximate contact members  655 . 
     FIGS. 19 and 20 also illustrate the flow of a purging fluid in this embodiment of Bellville ring contact assembly. As illustrated by arrows, the purge gas enters purge port  770  and is distributed about the circumference of the assembly  600  within annular cavity  765 . The purged gas then flows through slots  780  and below the lower end of contact mount member  605  to the area proximate Bellville contact  610 . At this point, the gas flows to substantially surround the contact members  655  and, further, may proceed above the periphery of the wafer to the backside thereof. The purging gas may also proceed through an annular channel  712  defined by the contact mount member  605  and the interior of the compliant wall formed at the lower portion of wafer guide ring  615 . Additionally, the gas flow about contact members  655  cooperates with upturned lip  730  effect a barrier at lip  730  that prevents electroplating solution from proceeding therethrough. 
     When a wafer or other workpiece  25  is urged into engagement with the contact assembly  600 , the workpiece  25  first makes contact with the contact members  655 . As the workpiece is urged further into position, the contact members  655  deflect and effectively wipe the surface of workpiece  25  until the workpiece  25  is pressed against the upturned lip  730 . This mechanical engagement, along with the flow of purging gas, effectively isolates the outer periphery and backside of the workpiece  25  as well as the Bellville ring contact  610  from contact with the plating solution. 
     A further embodiment of a Bellville ring contact assembly is shown generally at  600   b  of FIGS. 21-23. In this embodiment, a separate barrier member  620   b  is employed. In most other respects, Bellville ring contact assembly  600   b  is substantially similar to Bellville ring contact assembly  600  above. Accordingly, similar components of assembly  600   b  are labeled with the same reference numbers as assembly  600  above, except that the similar components of assembly  600   b  include a “b” suffix. 
     As particularly illustrated in FIG. 22, barrier member  620   b  includes a transverse section  632   b , an angled section  637   b  and an upturned lip  642   b . Transverse section  632   b  of barrier member  620   b  is disposed in an annular groove  720   b  disposed in the outer body member  625   b . Annular groove  720   b  is defined at its lower end by a transverse extending flange  710   b  having an angled wall  685   b  that contacts the barrier member  620   b  at the end of transverse section  632   b  that meets the angled section  637   b . This assists in stiffening the barrier member  620   b  to insure proper engagement with the lower face of wafer  25 . 
     Like assembly  600 , assembly  600   b  is preferably adapted to distribute a purging gas therethrough. FIG. 23 illustrates one manner in which a flow of the purging gas can be provided through Bellville ring contact assembly  600   b . As illustrated, outer body member  625   b  and contact mount member  605   b  join to define the requisite flow passages. 
     With particular reference to FIG. 22, the contact members  655   b  of the Bellville ring contact  610   b  protrude beyond the barrier member  620   b . When a wafer or other workpiece  25  is urged into engagement with the contact assembly  600   b , the workpiece  25  first makes contact with the contact members  655   b . As the workpiece is urged further, the contact members  655   b  deflect and effectively wipe the surface of workpiece  25  until the workpiece  25  is pressed against the barrier member  620   b . This mechanical engagement, along with the flow of purging gas, effectively isolates the outer periphery and backside of the workpiece  25  as well as the Bellville ring contact  610   b  from contacting the plating solution. 
     Another embodiment of a Bellville ring contact assembly is shown generally at  600   c  of FIG.  24 . This embodiment is substantially similar to contact assembly  600   b  and, as such, similar reference generals are used to designate similar parts, except that the components of contact assembly  600   c  include a “c” suffix. 
     The principal difference between contact assembly  600   c  and  600   b  can best be understood with reference to a comparison between FIG.  22  and FIG.  24 . As illustrated, the principal difference relates to the shape of the flange  710   c  and the elastomeric seal member  620   c . In the embodiment of contact assembly  600   c , the flange  710   c  and elastomeric seal member  620   c  are co-extensive with one another. As such, the seal against the bottom surface of the wafer  25  is not as compliant. Nevertheless, this structure abuts the bottom of the wafer to effectively form a barrier against the plating solution, particularly when used in conjunction with a purging gas. 
     A cross-sectional view of a still further embodiment of a Bellville ring contact assembly is a shown generally at  600   d  of FIG.  25 . In this embodiment, an O-ring  740  is disposed in a corresponding notch  745  of the outer body member  625   d  to form a sealing arrangement against the surface of workpiece  25  when the workpiece is urged against the contacts  655   d  Bellville ring contact  610   d . The O-ring  740   d  is dimensioned to protrude beyond lip  730   d  of the outer body member  625   d . Lip  730   d  of the outer body member  625   d  thereby assists in backing-up the O-ring seal. 
     Bellville ring contact assembly  600   d , unlike the other contact assemblies described above, does not necessarily include a wafer guide ring. Rather, assembly  600   d  illustrates the use of one or more securements  750  that are used to fasten the various components to one another and the interior wall of contact mount member  605   d  is slanted to provide the wafer guide surface. 
     Other Contact Assemblies 
     FIGS. 26 and 27 illustrate further embodiments of plating contacts and peripheral seal members. With reference to FIG. 26, the arrangement includes the plating contact, which is provided in the form of an annular contact member or ring  834  for mounting on the rotor assembly of the electroplating apparatus. While the annular contact ring is illustrated as being circular in configuration, it will be understood that the annular contact ring can be non-circular in configuration. An annular seal member  836  is provided in operative association with the annular contact ring, and as will be further described, cooperates with the contact ring to provide continuous sealing of a peripheral region of the workpiece which is positioned in electrically-conductive contact with the annular contact ring. 
     The annular contact ring  834  includes a mounting portion  838  by which the contact ring is mounted for rotation on the rotor assembly of the electroplating apparatus. The contact ring is also electrically joined with suitable circuitry provided in the rotor assembly, whereby the contact ring is electrically joined in the circuitry of the electroplating apparatus for creating the necessary electrical potential at the surface of the wafer  25  (the cathode) for effecting electroplating. The annular contact ring further includes a depending support portion  840 , and an annular contact portion  842  which extends inwardly of the mounting portion  838 . The annular contact portion  842  defines a generally upwardly facing contact surface  844  which is engaged by the wafer  25  to establish electrical contact between the contact ring and the seed layer of the wafer. It is contemplated that the annular contact portion  842  of the contact ring provide substantially continuous electrically-conductive contact with a peripheral region of the associated wafer or other workpiece. 
     The annular contact ring  834  is preferably configured to promote centering of workpiece  25  on the contact ring and its associated seal member. The contact ring preferably includes an inwardly facing conic guide surface  835  for guiding the workpiece into centered (i.e., concentric) relationship with the contact ring and associated seal member. The conic guide surface  835  acts as an angled lead-in (preferably angled between about 2 degrees and 15 degrees from vertical) on the contact ring inner diameter to precisely position the outside diameter of the workpiece on the contact diameter (i.e., ensure that workpiece is as concentric as possible on the contact ring). This is important for minimizing the overlap of the contact and its associated seal onto the surface of the workpiece, which can be quite valuable if it comprises a semiconductor wafer. 
     The annular seal member  836  of the present construction is positioned in operative association with the annular contact ring  834 , whereby a peripheral region of the wafer  25  is sealed from electroplating solution in the electroplating apparatus. The wafer  25  can be held in position for electrical contact with the annular contact ring  834  by an associated backing member  846 , with disposition of the wafer in this fashion acting to position the wafer in resilient sealing engagement with the peripheral seal member  36 . 
     The peripheral seal member  836  is preferably formed from polymeric or elastomeric material, preferably a fluoroelastomer such as AFLAS, available from the 3M Company. The seal member  836  preferably includes a portion having a substantially J-shaped cross-sectional configuration. In particular, the seal member  836  includes a generally cylindrical mounting portion  848  which fits generally about support portion  840  of annular contact ring  34 , and may include a skirt portion  49  which fits generally about mounting portion  38  of the contact ring. The seal member further includes a generally inwardly extending, resiliently deformable seal lip  850 , with the mounting portion  838  of the seal lip  850  together providing the portion of the seal member having a J-shaped cross-sectional configuration. As illustrated in FIG. 26, the annular seal lip  850  initially projects beyond the contact portion  842  of the annular contact ring in a direction toward the wafer  25  or other workpiece. As a result, the deformable seal lip is resiliently biased into continuous sealing engagement with the peripheral region of the wafer when the wafer is positioned in electrically-conductive contact with the contact portion of the contact ring. 
     In the embodiment of the present invention illustrated in FIG. 26, the annular seal lip  850  has an inside dimension (i.e., inside diameter) less than an inside dimension (i.e., inside diameter) of the contact portion  842  of the annular contact ring  834 . By this arrangement, the seal lip  850  engages the wafer radially inwardly of the contact portion  842 , to thereby isolate the contact portion from plating solution in the electroplating apparatus. This arrangement is preferred when it is not only desirable to isolate a peripheral region of the wafer or other workpiece from the electroplating solution, but to also isolate the annular contact ring from the solution, thereby minimizing deposition of metal on the annular contact ring during electroplating. 
     The seal member  836  is preferably releaseably retained in position on the annular contact ring  834 . To this end, at least one retention projection is provided on one of the seal member and contact ring, with the other of the seal member and contact ring defining at least one recess for releaseably retaining the retention projection. In the illustrated embodiment, the seal member  836  is provided with a continuous, annular retention projection  852 , which fits within an annular recess  854  defined by annular contact ring  834 . The polymeric or elastomeric material from which the seal member  836  is preferably formed promotes convenient assembly of the seal member onto the contact ring by disposition of the projection  852  in the recess  854 . 
     FIG. 27 illustrates an annular contact ring  934  embodying the principles of the present invention, including a mounting portion  938 , a depending support portion  940 , and an inwardly extending annular contact portion  942 , having a contact surface  944  configured for electrically-conductive contact with a peripheral region of an associated wafer  25  or other workpiece. This embodiment differs from the previously-described embodiment, in that the associated peripheral seal member, designated  936 , including a seal lip that engages the workpiece outwardly (rather than inwardly of) the associated annular contact ring. 
     The annular seal member  934  has a generally J-shaped cross-sectional configuration, and includes a generally cylindrical mounting portion  948 , and a resiliently deformable annular seal lip  950  which extends radially inwardly of the mounting portion. As in the previous embodiment, the deformable seal lip  950  initially projects beyond the contact portion  942  in a direction toward the wafer  25 , so that the seal lip  950  is resiliently biased into continuous engagement with the peripheral region of the wafer when the wafer is positioned in electrically-conductive contact with the contact portion  942  of the contact ring  934 . In this embodiment, the seal ring  950  has an inside dimension (i.e., inside diameter) greater than the inside dimension (i.e., inside diameter) of the annular contact portion  942 . By this arrangement, the annular contact portion engages the workpiece radially inwardly of the seal lip. Attendant to positioning of the wafer  25  in electrically-conductive contact with the annular contact portion  942 , the deformable seal lip  950  of the peripheral seal member is deformed generally axially of the cylindrical mounting portion  948  thereof. The seal member is thus maintained in sealing contact with the peripheral portion of the wafer, whereby edge and rear surfaces of the wafer are isolated from plating solution within the electroplating apparatus. 
     As in the previous embodiment, the peripheral seal member  936  is configured for releasable retention generally within the annular contact ring  934 . To this end, the annular seal member  936  includes a continuous annular retention projection  952  which is releaseably retained within a continuous annular recess  954  defined by the annular contact ring  934 . This arrangement promotes efficient assembly of the seal member and contact ring. 
     Rotor Contact Connection Assembly 
     In many instances, it may be desirable to have a given reactor assembly  20  function to execute a wide range of electroplating recipes. Execution of a wide range of electroplating and electroless plating recipes may be difficult, however, if the process designer is limited to using a single contact assembly construction. Further, the plating contacts used in a given contact assembly construction must be frequently inspected and, sometimes, replaced. This is often difficult to do in existing electroplating reactor tools, frequently involving numerous operations to remove and/or inspect the contact assembly. The present inventor has recognized this problem and has addressed it by providing a mechanism by which the contact assembly  85  is readily attached and detached from the other components of the rotor assembly  75 . Further, a given contact assembly type can be replaced with the same contact assembly type without re-calibration or readjustment of the system. 
     To be viable for operation in a manufacturing environment, such a mechanism should accomplish several functions including: 
     1. Provide secure, fail-safe mechanical attachment of the contact assembly to other portions of the rotor assembly; 
     2. Provide electrical interconnection between the contacts of the contact assembly and a source of electroplating power; 
     3. Provide a seal at the electrical interconnect interface to protect against the processing environment (e.g., wet chemical environment); 
     4. Provide a sealed path for purge the asked to the contact assembly; and 
     5. Minimize use of tools or fasteners which can be lost, misplaced, or used in a manner that damages the electroplating equipment. 
     FIGS. 28 and 29 illustrate one embodiment of a quick-attach mechanism that meets the foregoing requirements. For simplicity, only those portions of the rotor assembly  75  necessary to understanding the various aspects of the quick-attach mechanism are illustrated in these figures. 
     As illustrated, the rotor assembly  75  may be comprised of a rotor base member  205  and a removable contact assembly  1210 . Preferably, the removable contact assembly  1210  is constructed in one of the manners set forth above. The illustrated embodiment, however, employs a continuous ring contact, such as shown in FIG.  26 . 
     The rotor base member  1205  is preferably annular in shape to match the shape of the semiconductor wafer  25 . A pair of latching mechanisms  1215  are disposed at opposite sides of the rotor base member  1205 . Each of the latching mechanisms  1215  includes an aperture  1220  disposed through an upper portion thereof that is dimensioned to receive a corresponding electrically conductive shaft  1225  that extends downward from the removable contact assembly  1210 . 
     The removable contact assembly  210  is shown in a detached state in FIG.  28 . To secure the removable contact assembly  1210  to the rotor base member  1205 , an operator aligns the electrically conductive shafts  1225  with the corresponding apertures  1220  of the latching mechanisms  1215 . With the shafts  1225  aligned in this manner, the operator urges the removable contact assembly  1210  toward the rotor base member  1205  so that the shafts  1225  engage the corresponding apertures  1220 . Once the removable contact assembly  1210  is placed on the rotor base member  1205 , latch arms  1230  are pivoted about a latch arm axis  1235  so that latch arm channels  1240  of the latch arms  1230  engage the shaft portions  1245  of the conductive shafts  1235  while concurrently applying a downward pressure against flange portions  1247 . This downward pressure secures the removable contact assembly  1210  with the rotor base member  1205 . Additionally, as will be explained in further detail below, this engagement results in the creation of an electrically conductive path between electrically conductive portions of the rotor base assembly  1205  and the electroplating contacts of the contact assembly  1210 . It is through this path that the electroplating contacts of the contact assembly  1210  are connected to receive power from a plating power supply. 
     FIGS. 30A and 30B illustrate further details of the latching mechanisms  1215  and the electrically conductive shafts  1225 . As illustrated, each latching mechanism  1215  is comprised of a latch body  1250  having aperture  1220 , a latch arm  1230  disposed for pivotal movement about a latch arm pivot post  1255 , and a safety latch  1260  secured for relatively minor pivotal movement about a safety latch pivot post  1265 . The latch body  1250  may also have a purge port  270  disposed therein to conduct a flow of purging fluid through corresponding apertures of the removable contact assembly  1210 . An O-ring  1275  is disposed at the bottom of the flange portions of the conductive shafts  1225 . 
     FIGS. 31A-31C are cross-sectional views illustrating operation of the latching mechanisms  1215 . As illustrated, latch arm channels  1240  are dimensioned to engage the shaft portions  1245  of the conductive shafts  1225 . As the latch arm  1230  is rotated to engage the shaft portions  1245 , a nose portion  1280  of the latch arm  1230  cams against the surface  1285  of safety latch  1260  until it mates with channel  1290 . With the nose portion  1280  and corresponding channel  1290  in a mating relationship, latch arm  1230  is secured against inadvertent pivotal movement that would otherwise release removable contact assembly  1210  from secure engagement with the rotor base member  1205 . 
     FIGS. 32A-32D are cross-sectional views of the rotor base member  1205  and removable contact assembly  1210  in an engaged state. As can be seen in these cross-sectional views, the electrically conductive shafts  1225  include a centrally disposed bore  1295  that receives a corresponding electrically conductive quick-connect pin  1300 . It is through this engagement that an electrically conductive path is established between the rotor base member  1205  and the removable contact assembly  1210 . 
     As also apparent from these cross-sectional views, the lower, interior portion of each latch arm  1230  includes a corresponding channel  305  that is shaped to engage the flange portions  1247  of the shafts  1225 . Channel  1305  cams against corresponding surfaces of the flange portions  1247  to drive the shafts  1225  against surface  1310  which, in turn, effects a seal with O-ring  1275 . 
     Rotor Contact Drive 
     As illustrated in FIGS. 33 and 34, the rotor assembly  75  includes an actuation arrangement whereby the wafer or other workpiece  25  is received in the rotor assembly by movement in a first direction, and is thereafter urged into electrical contact with the contact assembly contact by movement of a backing member  1310  toward the contact assembly, in a direction perpendicular to the first direction. FIG. 35 is an exploded view of various components of the rotor assembly  75  and stationary assembly  70  of the reactor head  30 . 
     As illustrated, the stationary assembly  70  of the reactor head  30  includes a motor assembly  1315  that cooperates with shaft  1360  of rotor assembly  75 . Rotor assembly  75  includes a generally annular housing assembly, including rotor base member  1205  and an inner housing  1320 . As described above, the contact assembly is secured to rotor base member  1205 . By this arrangement, the housing assembly and the contact assembly  1210  together define an opening  1325  through which the workpiece  125  is transversely movable, in a first direction, for positioning the workpiece in the rotor assembly  175 . The rotor base member  1205  preferably defines a clearance opening for the robotic arm as well as a plurality of workpiece supports  1330  upon which the workpiece is positioned by the robotic arm after the workpiece is moved transversely into the rotor assembly by movement through opening  1325 . The supports  1330  thus support the workpiece  25  between the contact assembly  1210  and the backing member  1310  before the backing member engages the workpiece and urges it against the contact ring. 
     Reciprocal movement of the backing member  1310  relative to the contact assembly  1210  is effected by at least one spring which biases the backing member toward the contact assembly, and at least one actuator for moving the backing member in opposition to the spring. In the illustrated embodiment, the actuation arrangement includes an actuation ring  1335  which is operatively connected with the backing member  1310 , and which is biased by a plurality of springs, and moved in opposition to the springs by a plurality of actuators. 
     With particular reference to FIG. 33, actuation ring  1335  is operatively connected to the backing member  1310  by a plurality (three) of shafts  1340 . The actuation ring, in turn, is biased toward the housing assembly by three compression coil springs  1345  which are each held captive between the actuation ring and a respective retainer cap  1350 . Each retainer cap  1350  is held in fixed relationship with respect to the housing assembly by a respective retainer shaft  1355 . By this arrangement, the action of the biasing springs  1345  urges the actuation ring  1335  in a direction toward the housing, with the action of the biasing springs thus acting through shafts  1340  to urge the backing member  1335  in a direction toward the contact assembly  1210 . 
     Actuation ring  1335  includes an inner, interrupted coupling flange  1365 . Actuation of the actuation ring  1335  is effected by an actuation coupling  3170  (FIG. 34) of the stationary assembly  70 , which can be selectively coupled and uncoupled from the actuation ring  1335 . The actuation coupling  1370  includes a pair of flange portions  1375  that can be interengaged with coupling flange  1365  of the actuation ring  1335  by limited relative rotation therebetween. By this arrangement, the actuation ring  1335  of the rotor assembly  75  can be coupled to, and uncoupled from, the actuation coupling  1370  of the stationary assembly  70  of the reactor head  30 . 
     With reference again to FIGS. 33 and 34, actuation coupling  1370  is movable in a direction in opposition to the biasing springs  1345  by a plurality of pneumatic actuators  1380  (shown schematically) mounted on a stationary, upper plate  1381  (see FIG. 1) of the stationary assembly  70 . Each actuator  1380  is operatively connected with the actuation coupling  1370  by a respective linear drive member  1385 , each of which extends generally through the upper plate  381  of the stationary assembly  70 . There is a need to isolate the foregoing mechanical components from other portions of the reactor assembly  20 . A failure to do so will result in contamination of the processing environment (here, a wet chemical electroplating environment). Additionally, depending on the particular process implemented in the reactor  20 , the foregoing components can be adversely affected by the processing environment. 
     To effect such isolation, a bellows assembly  1390  is disposed to surround the foregoing components. The bellows assembly  1390  comprises a bellows member  395 , preferably made from Teflon, having a first end thereof secured at  1400  and a second end thereof secured at  1405 . Such securement is preferably implemented using the illustrated liquid-tight, tongue-and-groove sealing arrangement. The convolutes  1410  of the bellows member  1395  flex during actuation of the backing plate  1310 . 
     FIG. 34 illustrates the disposition of the reactor head  30  in a condition in which it may accept a workpiece, while FIG. 33 illustrates the disposition of the reactor head in a condition in which it is ready to process the workpiece in the reactor bowl  35 . 
     Operation of the reactor head  30  will be appreciated from the above description. Loading of workpiece  25  into the rotor assembly  75  is effected with the rotor assembly in a generally upwardly facing orientation, such as illustrated in FIG. 2 with the processing head in a condition shown in FIG.  34 . Workpiece  25  is moved transversely through the opening  325  defined by the rotor assembly  75  to a position wherein the workpiece is positioned in spaced relationship generally above supports  330 . A robotic arm  415  is then lowered (with clearance opening  325  accommodating such movement), whereby the workpiece is positioned upon the supports  330 . The robotic arm  415  can then be withdrawn from within the rotor assembly  75 . 
     The workpiece  25  is now moved perpendicularly to the first direction in which it was moved into the rotor assembly. Such movement is effected by movement of backing member  1310  generally toward contact assembly  1210 . It is presently preferred that pneumatic actuators  1380  act in opposition to biasing springs  1345  which are interposed between the inner housing  1320  and the spring plate  1311  of the backing member  1310 . Thus, actuators  1380  are operated to allow conjoint movement of the actuator coupling  1370  and the actuator ring  1335  to permit springs  1345  to bias and urge the backing member  310  toward contact  1210 . 
     In the preferred form, the connection between actuation ring  1335  and backing member  1310  by shafts  1340  permits some “float”. That is, the actuation ring and backing member are not rigidly joined to each other. This preferred arrangement accommodates the common tendency of the pneumatic actuators  1380  to move at slightly different speeds, thus assuring that the workpiece is urged into substantial uniform contact with the electroplating contacts of the contact assembly  210  while avoiding excessive stressing of the workpiece, or binding of the actuation mechanism. 
     With the workpiece  25  firmly held between the backing member  310  and the contact assembly  210 , lift and rotate apparatus  80  of FIG. 2 rotates the reactor head  30  and lowers the reactor head into a cooperative relationship with reactor bowl  35  so that the surface of the workpiece is placed in contact with the surface of the plating solution (i.e., the meniscus of the plating solution) within the reactor vessel. 
     Depending on the particular electroplating process implemented, it may be useful to insure that any gas which accumulates on the surface of the workpiece is permitted to vent and escape. Accordingly, the surface of the workpiece may be disposed at an acute angle, such as on the order of two degrees from horizontal, with respect to the surface of the solution in the reactor vessel. This facilitates venting of gas from the surface of the workpiece during the plating process as the workpiece, and associated backing and contact members, are rotated during processing. Circulation of plating solution within the reactor bowl  35 , as electrical current is passed through the workpiece and the plating solution, effects the desired electroplating of a metal layer on the surface of the workpiece. 
     The actuation of the backing member  1310  is desirably effected by a simple linear motion, thus facilitating precise positioning of the workpiece, and uniformity of contact with the contacts of the contact assembly  1210 . The isolation of the moving components using a bellows seal arrangement further increases the integrity of the electroless plating process. 
     A number of features of the present reactor facilitate efficient and cost-effective electroplating of workpieces such as semiconductor wafers. By use of a contact assembly having substantially continuous contact in the form of a large number of sealed, compliant discrete contact regions, a high number of plating contacts are provided while minimizing the required number of components. The actuation of the backing member  310  is desirably effected by a simple linear motion, thus facilitating precise positioning of the workpiece, and uniformity of contact with the contact ring. The isolation of the moving components using a bellows seal arrangement further increases the integrity of the electroplating process. 
     Maintenance and configuration changes are easily facilitated through the use of a detachable contact assembly  1210 . Further, maintenance is also facilitated by the detachable configuration of the rotor assembly  75  from the stationary assembly  70  of the reactor head. The contact assembly provides excellent distribution of electroplating power to the surface of the workpiece, while the preferred provision of the peripheral seal protects the contacts from the plating environment (e.g., contact with the plating solution), thereby desirably preventing buildup of plated material onto the electrical contacts. The perimeter seal also desirably prevents plating onto the peripheral portion of the workpiece. 
     Electroless Plating Reactor 
     With reference to FIG. 36, there is shown a reactor assembly  20   b  for electroless plating on a microelectronic workpiece or workpiece, such as a semiconductor wafer  25 . Generally stated, the reactor assembly  20   b  is comprised of a reactor head or processing head  30   b  and a corresponding reactor bowl  35   b . This type of reactor assembly is particularly suited for effecting electroless plating of semiconductor wafers or like workpieces, in which a pre-applied thin-film seed layer of the wafer is plated with a blanket metallic layer. 
     The electroless plating reactor bowl  35   b  is that portion of the reactor assembly  20   b  that contains electroless plating solution, and that directs the solution against a generally downwardly facing surface of the workpiece  25   b  to be plated. To this end, electroless plating solution S is introduced into the reactor bowl  35   b . The solution S flows from the reactor bowl  35   b , over a weir-like inside wall  36   b  of the bowl, into a lower overflow channel  40   b  of the reactor assembly  20 . The solution S exits the channel  40   b  through an outlet nozzle  41 . The outlet nozzle  41   b  is connected by a conduit  42   b  to an outlet valve block  43   b  which can direct the solution S through one or two outlet passages  44   b . An exhaust passage  45   b  directs gases to an exhaust nozzle  46   b  for collection, treatment and/or recycling. Solution can be drawn from the overflow chamber and collected, typically for recirculation back through the reactor. 
     Electroless plating solution flows from one or more inlet conduits  50   b  through a valve block  54   b  and then through a bottom opening  55   b  of the reactor bowl  35   b . The solutionS contacts the downwardly facing, process side of the wafer  25 . 
     The reactor head  30   b  of the reactor  20   b  is preferably constructed in the same manner as the electroplating reactor  20  of FIG.  1  and is comprised of a stationary assembly  70   b  and a rotor assembly  75   b . Rotor assembly  75   b  is configured to receive and carry the wafer  25  or like workpiece, position the wafer in a process-side down orientation within the reactor bowl  35   b , and to rotate or spin the workpiece during processing. The reactor head  30   b  is typically mounted on a lift/rotate apparatus  80   b , which is configured to rotate the reactor head  30  from an upwardly-facing disposition (see FIG.  2 ), in which it receives the wafer to be plated, to a downwardly facing disposition, as shown in FIG. 35, in which the surface of the wafer to be plated is positioned downwardly in reactor bowl  35   b . A robotic arm  415 , including an end effector, is typically employed for placing the wafer  25  in position on the rotor assembly  75   b , and for removing the plated wafer from the rotor assembly. 
     Unlike electroplating reactor  20 , electroless plating reactor  20   b  does not conduct electrical power to the surface of wafer  25 . As such, a workpiece support is used in lieu of an electrical contact assembly  85 . To this end, the workpiece support may be constructed in the same fashion as any of the contact assemblies described above, except that the conductive structures (i.e., those constructed of platinized titanium or and other conductive metal) are constructed from a dielectric material that is compatible with the electroplating environment. As above, such workpiece holders preferably include provisions for providing a flow of an inert fluid, such as nitrogen, to the peripheral regions and backside of the wafer. 
     As particularly illustrated in FIGS. 37 through 41, the workpiece holder assembly  2085  may be generally comprised of several discrete components. An outer ring  2095  is formed from a plastic material or the like that is electrically non-conductive and is formed from a material that is chemically compatible with the electroless plating environment. The outer ring  2095  may, for example, be composed of PVDF. When the workpiece that is to be plated is a circular semiconductor wafer, the outer ring  2095 , as well as the other portions of the workpiece holder assembly  2085 , are formed as annular components that, when joined together, form a bounded central open region  2093  that exposes the surface of the semiconductor wafer that is to be plated. 
     The outer ring  2095  is provided with a radially extending end wall  95   a  having an oblique end region  2095   b  which forms an annular inside surface  2096  onto which is provided an annular seal element  2098 . The seal element is adhesively adhered or molded or otherwise attached to the inside surface. As will be explained in further detail below, the seal element  2098  seals against the face  2025   a  of the semiconductor wafer  25  to assist in preventing the plating environment within the reactor bowl  35  from penetrating behind the wafer surface  25   a  which is to be plated. The annular sea] element is preferably composed of AFLAS elastomer. 
     The outer ring  2095  surrounds a base ring  2100  which has a large body portion  2100   a  providing an inside groove  2100   b  and an outside groove  2100   c . The base ring is preferably composed of stainless steel. The large body portion is connected to a collar portion  2100   d  which extends toward the inside surface  2096 . The collar portion  2100   d  is turned inwardly at a lip  100   e . A retainer ring  2102 , preferably composed of polypropylene, is located within the base ring  2100 . The retainer ring  2102  includes a centering flange  2102   a , a conically extending wall  2102   b , and an outside rib  2102   c  which interfits into the inside groove  2100   b  of the base ring  2100 . 
     Located above the centering flange  2102   a , and below the seal element  2098  is a “Belleville” spring  2104 . The Belleville spring is annular in overall shape and generally rectangular in cross-section, and formed having a shallow frustoconical shape. The spring  2104  is held in place by the retainer ring  2102  and can be slightly pre-loaded (slightly flattened) by the retainer ring  2102  against the seal element  2098 , The spring  2104  includes an outside annular notch  2104   a , and an inside annular notch  2104   b . The spring  2104  is preferably composed of plastic. 
     Two connector shafts  2225  are threaded into threaded holes  2226  diametrically oriented across the workpiece holding assembly  2085 , and formed into the base ring  2100 . The shafts  2225  include tool engagement shoulders  2227  for tightening the shafts  2225  into the base ring  100 . 
     Preferably, workpiece support  2085  includes a plurality of passages for providing a purging gas to the peripheral regions of the wafer radially exterior of the seal element  2098  as well as to the back side of the wafer  25 . To this end, as illustrated in FIGS. 40 and 41, the workpiece support  2085  includes an annular channel  2137  that is in fluid communication with a purge port (not illustrated) and effectively functions as a manifold. A plurality of slots  2139  are formed in the interstitial region between the outer ring  2095  and the base ring  2100  to provide fluid communication between the annular channel  2137  and region  2141  proximate the peripheral edge regions of the wafer  25 . Together, seal member  2098  and the flow of purging gas assist in forming a barrier between the electroplating environment and the peripheral regions and backside of wafer  25 . Further distribution of the purging gas is affected through an annular channel  2143  formed between the exterior of retainer ring  2102  and base ring  2100 . 
     During loading of the wafer  25  into the workpiece holding assembly  2085 , the wafer  25  progresses upwardly in the direction Y 1  to the position shown in FIG.  40 . The wafer is radially guided or centered by the conically shaped wall  2102   b  to its position shown in FIG.  40 . In the position shown in FIG. 40, the wafer  25  engages the inside annular notch  2104   b  of the spring  2104 . By action of a backing member  310 , described above, the wafer  25  is pressed upwardly, acting to flex the spring  2104  into the position shown in FIG.  41 . 
     The flexing or flattening of the spring  2104 , as shown in FIG. 41, causes the wafer  25  to be partially received within the notch  2104   b , and the lip  2100   e  to be received in the outside notch  2104   a . The wafer face  25   a  is pressed against the seal element  2098  which is in turn held in place by the annular inside surface  2096  of the outer ring  2095 . When the backing member  310  is released, the spring  2104 , under influence of its own resilient spring energy, will return to its configuration shown in FIG.  40  and partially push the wafer  25  in the direction Y 2 . From the position shown in FIG. 40 absent the force exerted by the backing member  310 , the wafer  25  will proceed by gravity supported on the retracting backing member  310  along the direction Y 2 . 
     A further embodiment of a workpiece holder is illustrated at  2085   b  of FIGS. 42 and 43. As illustrated, workpiece support  2085   b  is substantially similar to workpiece support  2085  of FIGS. 37-41. There are, however, three notable differences. First, a separate seal element  2098  is not employed in this embodiment. Rather, outer ring  2095   b  includes an annular extension  2146  that terminates in an upturned lip  2149  that engages surface  25   a  of wafer  25 . Second, upturned lip  2149  assists in removing wafer  25  from the wafer holder  2085   b  by providing a biasing force in the direction of the arrow X when backing member  310  is disengaged from the wafer  25 . As a result, Belleville ring member  2104  is not employed in this embodiment. Finally, an annular lip  2151  is provided on retainer ring  2102   b  to as a limit member that sets the limits to which wafer  25  may be moved into engagement with wafer holder  2085   b.    
     The embodiment illustrated in FIGS. 42 and 43, like wafer holder  2085 , also includes a plurality of flow channels for the provision of a purging gas. Given the substantial similarities between wafer holder  2085  and wafer holder  2085   b , similar structures are labeled with similar reference news in the embodiment of wafer holder  2085   b.    
     Purge Gas Supply to Contact and Holder Assemblies 
     When any of the contact assemblies or workpiece holders described above include a fluid communication network that provides a purging gas, such as nitrogen, it must be supplied from a source exterior to the contact assembly or workpiece holder. FIGS. 44-46 illustrate one manner in which such a fluid communication network may be supplied with a purging gas. 
     With reference to FIGS. 44 and 45, the rotor assembly  75  may be provided with a fluid communication channel or tube  710  having an inlet at  720  that receives the purging gas and communicates it to one or more purge ports  725  that are disposed proximate the peripheral regions of the workpiece holder or contact assembly, shown here as assembly  85   a . In the illustrated embodiment, a tube  710  is used for such fluid communication. The tube  710  extends through the hollowed center of drive shaft  360  and then proceeds from the region of drive shaft  360  that is proximate the workpiece holder or contact assembly to at least one purge port  725  (two purge ports being used in the illustrated embodiment). In the alternative, the fluid communication path represented here by tube  710  may comprise one or more channels that are formed as hollow regions in solid body portions of the rotor assembly  75 . For example, as noted above, the purge gas may be supplied directly through a hollowed region of drive shaft  360  as opposed to an intermediate tube. Depending on the particular implementation of the rotor assembly  75 , communication of the purging gas may then proceed to the purge port through a corresponding tube or through a hollow channel formed in a substantially solid body member that spans therebetween. 
     Communication of the purging gas from purge port  725  to the isolated regions of the corresponding workpiece holder or contact assembly is illustrated in FIG.  46 . As shown, purge port  725  opens to a purge passageway  735  that is disposed through an outer housing of the rotor assembly  75 . The purge passageway  735  opens to an inlet port  740  of the workpiece holder or contact assembly (such inlet ports are also illustrated in the embodiments of the workpiece holders and contact assemblies described above). From such inlet ports, the purge gas flows through the particular holder or contact assembly in the manner described above. 
     Integrated Plating Tool 
     FIGS. 47 through 49 are top plan views of integrated processing tools, shown generally at  1450 ,  1455 , and  1500  that may incorporate electroless plating reactors and electroplating reactors as a combination for plating on a microelectronic workpiece, such as a semiconductor wafer. Processing tools  1450  and  1455  are each based on tool platforms developed by Semitool, Inc., of Kalispell, Mont. The processing tool platform of the tool  450  is sold under the trademark LT-210™, the processing tool platform of the tool  1455  is sold under the trademark LT-210C™, and the processing tool  1500  is sold under the trademark EQUINOX™. The principal difference between the tools  1450 ,  1455  is in the footprints required for each. The platform on which tool  1455  is based has a smaller footprint than the platform on which tool  1455  is based. Additionally, the platform on which tool  1450  is based is modularized and may be readily expanded. Each of the processing tools  1450 ,  4155 , and  1500  are computer programmable to implement user entered processing recipes. 
     Each of the processing tools  1145 ,  1455 , and  1500  include an input/output section  1460 , a processing section  1465 , and one or more robots  1470 . The robots  1470  for the tools  1450 ,  1455  move along a linear track. The robot  1470  for the tool  1500  is centrally mounted and rotates to access the input/output section  1460  and the processing section  1465 . Each input/output section  1460  is adapted to hold a plurality of workpieces, such as semiconductor wafers, in one or more workpiece cassettes. Processing section  1465  includes a plurality of processing stations  1475  that are used to perform one or more fabrication processes on the semiconductor wafers. The robots  1470  are used to transfer individual wafers from the workpiece cassettes at the input/output section  1460  to the processing stations  1475 , as well as between the processing stations  1475 . 
     One or more of the processing stations  1475  can be configured as electroless plating reactor  1475   a  such as heretofore described, and one or more of the processing stations can be configured as electroplating assemblies,  1475   b  such as the electroplating reactor described above. For example, each of the processing tools  1450  and  1455  may include three electroless plating reactors, three electroplating reactors and one or more pre-wet/rinse station or other processing vessel. The pre-wet/rinse station is preferably one of the type available from Semitool, Inc. It will now be recognized that a wide variation of processing station configurations may be used in each of the individual processing tools  450 ,  455 , and  500  to execute electroless plating and electroplating processes. As such, the foregoing configurations are merely illustrative of the variations that may be used. 
     Plating Method Using Electroless Plating and Electroplating 
     According to a method of the present invention, workpieces, such as semiconductors wafers, having first been processed to have a seed layer applied thereon, are electrolessly plated and then electroplated. The method is schematically described in FIG.  50 . 
     A barrier layer is first applied (step  1 ) to features on a surface of a workpiece. The barrier layer can be applied by PVD or CVD processes. A seed layer is then applied (step  2 ) onto the barrier layer. The seed layer is preferably a Cu seed layer applied by a PVD or CVD processes. After the seed layer is applied, the workpiece can be placed in an electroless plating reactor as described below. An electroless plating bath is provided in the reactor and the workpiece is exposed to the plating bath to plate a conductive layer, preferably copper, thereon (step  3 ). The conductive layer is applied as a blanket to the extent that small and high aspect ratio vias and trenches are filled, but not to the extent that large vias and trenches are completely filled. By terminating the electroless plating at this point, a shorter time period in the overall process can be achieved. The workpiece having the electrolessly plated conductive layer thereon is then removed from the electroless plating reactor and transferred to an electroplating reactor wherein a further conductive layer, preferably copper is applied over the electrolessly plated conductive layer (step  4 ). The electroplating process has a higher deposition rate and has adequate filling conformality to fill the larger trenches and vias. 
     The electroless plating recipe can be a known recipe such as disclosed in the background section of this application in the article by V. M. Dubin, et al., or as describe in U.S. Pat. Nos. 5,500,315; 5,310,580; 5,389,496; or 5,139,818, all incorporated herein by reference. Further, the foregoing processing sequence can be carried out in any of the tools illustrated in FIGS. 47-49. 
     Numerous modifications may be made to the foregoing system without departing from the basic teachings thereof. Although the present invention has been described in substantial detail with reference to one or more specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.