Patent Publication Number: US-2007111519-A1

Title: Integrated electroless deposition system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/192,933, which claims benefit of U.S. Provisional Patent Application Ser. No. 60/648,004. U.S. patent application Ser. No. 11/192,933 is a continuation-in-part of co-pending U.S. patent application Ser. Nos. 10/996,342 and 10/965,220, which claim benefit of U.S. Provisional Patent Application Ser. No. 60/539,491, and co-pending U.S. patent application Ser. No. 11/043,442. The disclosure of each of the above-referenced patent applications are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Embodiments of the invention generally relate to an electroless deposition system for semiconductor processing.  
      2. Description of the Related Art  
      Metallization of sub-100 nanometer sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. More particularly, in devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with several million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling sub-micron high aspect ratio interconnect features with a conductive material, such as copper, wherein a high aspect ratio is greater than about 10:1. At these dimensions, conventional deposition techniques, such as chemical vapor deposition and physical vapor deposition, cannot reliably fill interconnect features like trenches or vias. As a result, plating techniques, i.e., electrochemical plating and electroless plating, have emerged as promising processes for void-free filling of sub-100 nanometer sized high aspect ratio interconnect features in integrated circuit manufacturing processes. Additionally, electrochemical and electroless plating processes have emerged as promising processes for depositing or repairing pre-plating seed layers and depositing post-plating layers, such as capping layers.  
      In order to further reduce the size of devices on integrated circuits, it has become necessary to use conductive materials having low resistivity and insulators having low k (dielectric constant&lt;4.0) to reduce the capacitive coupling between adjacent metal lines. Currently, copper and its alloys have become the metals of choice for sub-micron interconnect technology because copper has a lower resistivity than aluminum, (1.7 μΩ-cm compared to 3.1 μΩ-cm for aluminum), and a higher current carrying capacity and significantly higher electromigration resistance. These characteristics are important for supporting the higher current densities experienced at high levels of integration and increased device speed. Further, copper has a good thermal conductivity and is available in a highly pure state.  
      Although copper is a popular interconnect material, copper suffers by diffusing into neighboring layers, such as dielectric layers. The resulting undesirable presence of copper causes dielectric layers to become conductive and electronic devices to fail. Therefore, barrier materials are used to control copper diffusion. The barrier layer typically includes a refractory metal nitride and/or silicide, such as titanium or tantalum. Of this group, tantalum nitride is one of the most desirable materials for use as a barrier layer. Tantalum nitride has one of the lowest electrical resistivities of the metal nitrides and is also a good barrier to prevent copper diffusion, even when relatively thin layers are formed (e.g., 20 Å or less). A tantalum nitride layer is typically deposited by conventional deposition techniques, such as physical vapor deposition (PVD), atomic layer deposition (ALD) and chemical vapor deposition (CVD). A negative characteristic of Tantalum nitride is poor adhesion to a copper layer deposited thereon. Poor adhesion of subsequent deposited copper layer(s) can lead to poor electromigration in the formed device and possibly process contamination issues in subsequent processing steps, such as chemical mechanical polishing (CMP). It is believed that exposure of the tantalum nitride layer to sources of oxygen and other contamination will cause the exposed surface of the tantalum nitride layer to oxidize, thus preventing the formation of a strong bond to the subsequently deposited copper layer. Also, dielectric deposition processes typically contain carbon, which becomes incorporated into the dielectric layer. Carbon incorporation is often detrimental to the completion of wet chemical processes since the deposited film tends to be hydrophobic, reducing or preventing fluids from wetting and depositing a film having desirable properties. Therefore, a process and apparatus is needed for depositing a barrier layer or adhesion layer that strongly bonds to carbon-containing dielectric layers and subsequently deposited copper layers.  
      Another problem with the use of copper and its alloys is that copper readily oxidizes when exposed to air and is also vulnerable to chemical corrosion and deterioration due to subsequent processing steps. Copper interconnects are adversely affected by oxidation and other forms of deterioration and seed layers suffer from widely different levels of oxidation when queue times vary between lots.  
      A method of protecting copper interconnects from subsequent processing steps is to form a capping layer over copper interconnects. One problem with previous capping layer methods is inadequate pre-treatment of the substrate prior to electroless deposition of the capping layer and inadequate post-treatment of the capping layer, which may cause contamination problems and/or selectivity problems. One example of contamination includes watermarks remaining on hydrophobic films that contain copper, cobalt, and other metals. The presence of this type of contamination can seriously affect subsequent electroless deposition as well as other processing steps. Another problem with using capping layers to protect interconnects is the potential creation of shorts between closely spaced interconnects.  FIG. 1A  illustrates a substrate structure  100  with parallel interconnects  101 ,  102  and  103 . The substrate structure  100  is shown after being planarized by a chemical mechanical polishing (CMP) process. Even after rigorous cleaning, contamination in the form of copper particles  104   a  is generally present on the surface of substrate structure  100 .  FIG. 1B  depicts substrate structure  100  after a metallic capping layer, such as capping layer  105 , has been formed on top of parallel interconnects  101 ,  102 , and  103  by an electroless deposition process. Because the presence of any metal can act as a site of autocatalytic (electroless) deposition, copper particles  104   a  will experience significant deposition as well. In regions of closely spaced interconnects, these now enlarged metallic particles  104   b  ( FIG. 1B ) can create electrical leakage between the parallel interconnects  101 ,  102  and  103 . Also, the slightly irregular edge  106   a  of a parallel interconnect  101  will be exaggerated during the deposition of capping layer  105 , forming more irregular edge  106   b  and further reducing the distance  107  required to create leakage between interconnects.  
      Another problem facing manufacturers of ultra-large scale integrated circuits is the filling of very high and very low aspect ratio features on the same device at the same time.  FIG. 1C  is a schematic side view of a substrate structure  110  with sub-micron high aspect ratio (i.e., &gt;10:1) features, such as high aspect ratio features  111 , and a low aspect ratio feature  112 , both requiring copper fill. FIGS.  1 C-E show low aspect ratio feature with a depth-to-width ratio of approximately 1:5, but for some device features this ratio may be as much as 1:100 or more, such as for contact pads.  FIG. 1D  illustrates substrate structure  110  after a typical electroless copper plating process. Electroless copper film  115  of thickness  114  has been conformally deposited on substrate structure  110  via an electroless plating process. High aspect ratio features  111  are filled since the width  113  of high aspect ratio features  111  is no more than twice the thickness  114  of the electroless copper film  115 . Low aspect ratio feature  112  is only partially filled, however. Either an extended electroless fill process must be used, or another method of filling large, low aspect ratio features such as  112  must be used. Electroless deposition of films that can fill such large substrate features can require prohibitively long deposition times, e.g. one or more orders of magnitude longer than the time required to fill high aspect ratio features  111 . Application of a second plating method to fill low aspect ratio features such as  112  typically requires the added expense and complexity of processing substrates on an additional processing platform. In addition, electroless copper film  115  will be subject to degradation via oxidation prior to the secondary plating process.  
      Another problem related to oxidation is the formation of a native oxide on exposed electrical contacts during the fabrication of electronic devices. A native oxide typically forms when a substrate surface is exposed to oxygen. Oxygen exposure occurs when the substrate is moved between processing chambers at atmospheric conditions, or when removed from a substrate processing system between processing steps, or when a small amount of oxygen remaining in a processing chamber contacts the substrate surface. Native oxides may also result if the substrate surface is contaminated during etching. Native oxides typically form an undesirable film on the substrate surface. Native oxide films are usually very thin, such as between 5 and 20 angstroms, but thick enough to cause difficulties in subsequent fabrication processes. Such difficulties usually affect the electrical properties of semiconductor devices formed on the substrate. For example, a particular problem arises when native silicon oxide films are formed on exposed contact surfaces (e.g., source or drain connection points), such as those shown in  FIG. 1C . Exposed contact surfaces are present at the bottom of high aspect ratio features  111  and low aspect ratio feature  112  prior to performing interconnect metallization processes, such as electroless gap fill. Such contact surfaces are typically metallic materials subject to rapid native oxide growth. In some cases, contact surfaces may consist of a pure silicon surface that is subject to native oxide growth. Native oxides are electrically insulating and are undesirable at interfaces with device contacts or interconnecting electrical pathways because they cause high electrical contact resistance. This results in lower substrate yields and increased failure rates due to overheating at the electrical contacts. The native oxide film can also prevent adhesion of other layers that are subsequently deposited on the substrate. It is desirable to have a method for removing native oxides and other contaminants on exposed device contacts—particularly those found in sub-micron high-aspect features. Current methods include sputter etching and wet etch processes using hydrofluoric acid. Conventional sputter etching performs poorly in features having aspect ratios smaller than about 4:1 and can damage delicate silicon layers by physical bombardment.  
      Ultra-large scale integrated circuits may also suffer from high contact resistance as devices on integrated circuits are further reduced in size. High contact resistance can be the result of native oxide formation on contact surfaces, contamination, the formation of seams and voids, and barrier layer resistance. As noted above, native oxide may form on exposed contact surfaces such as those present at the bottom of high aspect ratio features  111  and low aspect ratio feature  112  shown in  FIG. 1C . Contamination may be present inside high aspect ratio features  111  from previous process steps because it is difficult to remove from such features. Seams may form between conductive layers deposited in a device feature, such as a contact surface. Seam formation results in high contact resistance despite the low resistivity of the individual layers formed thereon. Similarly, unwanted voids tend to form in high aspect ratio contacts when the contacts are filled with tungsten using conventional CVD methods. Voids greatly increase electrical resistance and may also be displaced into subsequent layers formed on the device. With smaller device sizes, the barrier layer makes up increasingly more cross-sectional area of a contact or via. Because barrier layers generally posses worse-than-optimal electrical resistance, contact resistance increases exponentially with decreasing size when conventional barrier layers are used.  
      Yet another problem that occurs during the manufacture of ultra-large scale integrated circuits is the depletion of silicon at the silicon contact interface through silicidation, i.e., diffusion into the contact interface by the conductive material filling the contact feature and the subsequent formation of a silicide by the conductive fill material.  
      Further, a functional and efficient integrated platform for electroless deposition processes capable of depositing uniform layers with minimal defects has not been developed. Therefore, there is a need for methods and apparatus that incorporate electroless deposition processes onto substrate-processing platforms capable of: 
          forming capping layers on interconnect features with minimal defects and minimal oxidation of the interconnect features;     removing native oxide and other contaminants on exposed contacts at the bottom of high aspect ratio features and depositing electroless Cobalt or Nickel for fill;     removing electroless cobalt or nickel overgrowth after contact fill;     cleaning oxides from highly doped silicon substrates at the source and drain connection points, depositing a thin film of cobalt, nickel, or both cobalt and nickel on the connection points, and annealing the substrate to form a first stage silicide;     depositing a barrier layer or adhesion layer that strongly bonds to carbon-containing dielectric layers and subsequently deposited copper layers;     depositing seed layers on substrate structures prior to copper interconnect deposition;     filling interconnect features with electroless copper deposition;     sequentially depositing a seed layer on a substrate structure and then filling the interconnect features with electroless copper deposition;     sequentially depositing a seed layer on a substrate structure and then filling the interconnect features with electrochemical (ECP) copper deposition;     sequentially depositing a seed layer on a substrate structure, filling the high aspect ratio interconnect features with electroless copper deposition, and filling large, low aspect ratio features with ECP overfill deposition; and     performing the above processes at an efficient rate.        

     SUMMARY OF THE INVENTION  
      Embodiments of the invention provide methods for integrating electroless seed layer deposition and ECP gap fill on a single platform, integrating electroless seed deposition and electroless gap fill on a single platform, depositing a capping layer over interconnects on a substrate without forming leakage paths between the interconnects, and integrating a brush box and vapor dryer into an electroless deposition system for post-deposition cleaning of substrates. One embodiment provides a method for filling high aspect ratio and low aspect ratio substrate features on a single platform. Another embodiment provides a method for cleaning silicon contacts and forming a stable silicide at the contacts without exposure to air. In some aspects, methods include pre-deposition cleaning treatments via plasma-enhanced dry etch or supercritical fluid chambers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
       FIG. 1A  (Prior Art) is a schematic perspective diagram of a substrate structure that has been cross-sectioned for clarity.  
       FIG. 1B  (Prior Art) is a schematic perspective diagram of the structure of  FIG. 1A  after the deposition of a capping layer on the substrate structure.  
       FIG. 1C  is a schematic side view of a substrate structure prior to copper film deposition.  
       FIG. 1D  is a schematic side view of the substrate structure in  FIG. 1C  after the deposition of a copper film via a typical electroless plating process.  
       FIG. 1E  is a schematic side view of the substrate structure in  FIG. 1D  after the deposition of a second copper film via an ECP overfill process.  
       FIGS. 1F-1K  illustrate schematic cross-sectional views of an integrated circuit fabrication sequence formed by processes described herein.  
       FIG. 2  is a schematic plan view of an exemplary deposition system.  
       FIG. 2A  is a schematic plan view of an exemplary deposition system.  
       FIG. 2B  illustrates a sectional view of an exemplary plating cell.  
       FIG. 3  is a perspective diagram of an exemplary substrate bevel cleaning chamber.  
       FIG. 4  is a partial perspective view of an exemplary substrate spin rinse dry cell.  
       FIG. 5A  illustrates a selective electroless deposition process sequence.  
       FIG. 5B  illustrates a non-selective electroless deposition process sequence.  
       FIG. 5C  illustrates a selective electroless deposition process sequence for high aspect ratio contact fill.  
       FIG. 6  is a perspective view of an exemplary electroless plating twin cell.  
       FIG. 7  is a perspective view of an exemplary twin electroless plating twin cell with processing enclosure removed for clarity.  
       FIG. 8  is a sectional view of an exemplary pair of electroless processing stations.  
       FIG. 8A  is a side perspective view of an exemplary brush box scrubbing device that may be used in embodiments of the invention.  
       FIG. 9  is a schematic side view of one embodiment of a vapor drying apparatus illustrating the progression of a substrate through the vapor drying apparatus.  
       FIG. 9A  is a perspective view of a running beam and a flipper robot for substrate transfer into a brush box chamber and a vapor dryer chamber.  
       FIG. 9B  is a flow chart summarizing the different methods of vertical substrate handling required for embodiments of the invention.  
       FIG. 10  is a flow chart of a substrate process sequence for one embodiment of the invention.  
       FIG. 11  is a schematic plan view of an exemplary deposition system.  
       FIG. 11A  is a schematic plan view of an exemplary deposition system.  
       FIGS. 12A, 12B ,  12 C,  12 D, and  12 E are flow charts of substrate process sequences for one embodiment of the invention.  
       FIG. 13  is a flow chart of a substrate process sequence for one embodiment of the invention.  
       FIG. 14  illustrates a cross-sectional view of a capacitively coupled plasma processing chamber that may be incorporated into embodiments of the invention.  
       FIG. 14A  illustrates a cross-sectional view of a plasma processing chamber adapted to deposit a ruthenium-containing layer on a substrate.  
       FIG. 15  is a flow chart of a substrate process sequence for one embodiment of the invention.  
       FIG. 16  is a flow chart of a substrate process sequence for one embodiment of the invention.  
       FIG. 17  is a flow chart of a substrate process sequence for one embodiment of the invention.  
       FIGS. 18A and 18B  illustrate a cross-sectional view of a process chamber that may be adapted to deposit reducing and catalytic layers on a substrate.  
       FIGS. 18C and 18D  illustrate a cross-sectional view of a process chamber that may be adapted to deposit reducing, catalytic, and ECP layers on a substrate.  
       FIG. 19  illustrates a partial cross sectional view of an illustrative processing chamber for heating, cooling, and etching.  
       FIG. 20  is a schematic cross-sectional view of an exemplary supercritical clean chamber that may be used in embodiments of the invention.  
      FIGS.  21 A-E are schematic cross-sectional views of a silicon contact illustrating a process of forming a silicide thereon using the inventive method.  
       FIG. 22  illustrates a processing sequence for forming a silicide on a silicon contact as described within an embodiment herein.  
       FIG. 23  illustrates a top perspective view of an exemplary annealing chamber of the invention with the cover or lid portion of the chamber removed so that the internal components are visible.  
      For clarity, identical reference numerals have been used, where applicable, to designate identical elements that are common between figures. 
    
    
     DETAILED DESCRIPTION  
      Embodiments of the invention generally provide methods of depositing materials onto semiconductor substrates by using one or more electroless, ECP, CVD and/or ALD processing chambers. More particularly, embodiments of the invention allow formation of capping layers with low defects and low oxidation of interconnect features, deposition of a barrier layer on substrates, deposition and/or repair of seed layers on substrates, electroless fill of interconnect features, and sequential filling of high and low aspect ratio interconnect features on a substrate, using electroless and ECP processes. Other embodiments of the invention allow the removal of native oxides and other contaminants on exposed contacts at the bottom of high aspect ratio features and the subsequent deposition of cobalt and/or nickel to fill such contacts. In one aspect, nickel silicide is formed after an oxide cleaning step and before a cobalt fill step to prevent further silicidation of diffused cobalt into silicon contacts. In another aspect, a nickel or cobalt layer is deposited onto a silicon contact and subsequently annealed to form a stable first stage silicide that may be exposed to air without danger of oxidation.  
      A typical sequence for forming an interconnect includes depositing one or more non-conductive layers, etching at least one of the layer(s) to form one or more features therein, depositing a barrier layer in the feature(s) and depositing one or more conductive layers, such as copper, to fill the feature.  
       FIG. 1F  illustrates a cross-sectional view of substrate  120  having an interconnect feature, or aperture  122 , formed into a dielectric layer  121  on the surface of the substrate  120 . Substrate  120  may comprise a semiconductor material such as, for example, silicon, germanium, or silicon germanium, for example. The dielectric layer  121  may be an insulating material, such as silicon dioxide, silicon nitride, SOI, silicon oxynitride and/or carbon-doped silicon oxides, such as SiO X C y , for example, BLACK DIAMOND™ low-k dielectric, available from Applied Materials, Inc., located in Santa Clara, Calif. Aperture  122  may be formed in substrate  120  using conventional lithography and etching techniques to expose contact layer  123 . Contact layer  123  may include copper, tungsten, aluminum or alloys thereof.  
      To prevent copper diffusion into dielectric layer  121 , barrier layer  124  may be formed on the dielectric layer  121  and in aperture  122 , as depicted in  FIG. 1G . Barrier layer  124  may be formed using a suitable deposition process including ALD, chemical vapor deposition (CVD), physical vapor deposition (PVD) or combinations thereof. In one embodiment, barrier layer  124  may be formed by a chamber of the cluster tool.  
      Rather than directly depositing a bulk conductive material, such as copper, onto barrier layer  124  to fill aperture  122 , a reducing layer  126  which promotes adhesion, may first be formed on barrier layer  124 , as depicted in  FIG. 1H . To form a reducing layer  126  on barrier layer  124 , the surface of barrier layer  124  is modified by use of a plasma deposition process. In one embodiment, this plasma deposition process may be conducted in the same deposition chamber as the barrier layer deposition process, described above.  
      To prepare substrate  120  for subsequent deposition of conductive layers via electroless and/or electrochemical plating, a catalytic layer  128  is deposited on barrier layer  124  as depicted in  FIG. 1l . Catalytic layer  128  is formed by exposing reducing layer  126  to a catalytic metal-containing precursor. Reducing layer  126  chemically reduces the catalytic metal-containing precursor to form catalytic layer  128  on barrier layer  124 . Catalytic layer  128  contains the respective metal from the precursor, allowing formation of subsequent conductive layers on the substrate via electroless and/or electrochemical deposition.  
      Conductive layers such as seed layer  129  and/or bulk layer  130  may then be deposited on substrate  120  as shown in  FIGS. 1J and 1K , respectively. Alternately, seed layer  129  may be deposited on substrate  120  followed by a bulk conductive layer, such as bulk layer  130  (not shown). Embodiments of the invention may deposit seed layer  129  and/or bulk layer  130  by an electroless plating process. In one aspect, bulk layer  130  may be deposited via an electrochemical plating process.  
      General Cluster Tool Description  
      The cluster tool generally contains a wet processing platform in communication with a substrate loading area and together with the loading area, comprises a substrate plating system. The loading area, or “dry side”, is generally configured to receive substrate-containing cassettes and transfer substrates received from the cassettes to the wet processing platform for wet processing. The loading area typically includes “dry side” processing chambers for treatment of substrates before and/or after wet processing, such as barrier layer deposition chambers and anneal chambers. The dry side may also contain a robot configured to transfer substrates between the cassettes, the wet processing platform, and the dry side processing chambers. The wet processing platform generally includes at least one substrate transfer robot and a plurality of substrate processing chambers, for example, ECP cells, IBC chambers, SRD chambers, electroless plating cells, etc. The various embodiments may include different combinations of wet and dry substrate-processing chambers. In one aspect, the cluster tool will allow for pre-treatment of a dry substrate, such as barrier layer deposition, wet processing of the substrate, such as seed layer deposition, electrochemical and/or electroless gap fill, and surface and/or bevel cleaning and drying, and any necessary post-deposition processing, such as anneal. Applications of the above processes suitable for substrate structure deposition include barrier layer deposition, electroless seed deposition, electroless seed repair, electroless seed and electroless interconnect fill (e.g. bulk fill), electroless seed and ECP interconnect fill, electroless capping deposition, and electroless high aspect ratio interconnect fill followed by ECP low aspect ratio interconnect fill.  
       FIG. 2  illustrates one example of a cluster tool  200  that may perform electroless deposition. Cluster tool  200  includes a factory interface  230  that includes a plurality of substrate loading stations  234  configured to interface with and retain substrate containing cassettes (hereafter referred to as cassettes). A factory interface robot  232  is positioned in the factory interface  230  and is configured to access and transfer a substrate  226  into and out of the cassettes positioned on the substrate loading stations  234 . The factory interface robot  232  also extends into a link tunnel  215  that connects the factory interface  230  to a wet processing platform  213 . The position of factory interface robot  232  allows for access to substrate loading stations  234  to retrieve substrates therefrom, and to then deliver the substrate  226  to an in-station  972  (see  FIG. 2A  for position of in-station  972 ) disposed on the wet processing platform  213  and typically located above or adjacent processing station  214  (In-station  972  is depicted in  FIGS. 2A and 9A ). Similarly, factory interface robot  232  may be used to transfer a substrate  226  into or out of processing stations  214  and  216  or processing stations  235  and  235   a . Processing stations  235  and  235   a  may include one or more stacked dry process chambers, such as anneal, barrier layer deposition, catalytic layer deposition, supercritical clean or dry etch chambers. Barrier layer and catalytic layer deposition take place prior to wet processing of a substrate and the annealing process typically takes place after wet processing. An anneal chamber that may be adapted to perform various aspects of the invention described herein is described below in conjucntion with  FIG. 23  and further described in U.S. patent application Ser. No. 10/996,342, filed Nov. 22, 2004, which is incorporated by reference in its entirety to the extent not inconsistent with the claimed aspects of the invention. When removing substrate  226  from processing stations  214 ,  216 ,  235  or  235   a , factory interface robot  232  may then deliver substrate  226 , which is clean and dry, back to one of the cassettes positioned on the substrate loading stations  234  for removal from cluster tool  200 .  
      Wet processing platform  213 , also referred to as the mainframe, includes a centrally positioned mainframe substrate transfer, such as mainframe robot  220 . Mainframe robot  220  generally includes one or more blades  222  and  224  configured to support and transfer substrates. Additionally, mainframe robot  220  and the blades  222  and  224  are generally configured to independently extend, rotate, pivot, and vertically move so that the mainframe robot  220  may simultaneously insert and remove substrates to/from the plurality of processing stations  202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214  or  216  positioned on wet processing platform  213 . Similarly, factory interface robot  232  also includes the ability to rotate, extend, pivot, and vertically move its substrate support blade, while also allowing for linear travel along the robot track  250   b  that extends from the factory interface  230  to the wet processing platform  213 .  
      Generally, the processing stations  202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214 , or  216  may be any of a number of processing chambers utilized in a substrate processing system. More particularly, the processing chambers on the integrated wet processing platform may be configured as ECP cells, rinsing chambers, IBC chambers, SRD chambers, substrate surface cleaning chambers (which collectively includes cleaning, rinsing, and etching chambers), electroless plating chambers (which includes pre- and post-clean chambers, activation chambers, deposition chambers, etc.), brush box chambers and vapor dryer chambers. Each of the various configurations of the wet processing platform and the factory interface will be discussed below.  
      Each of the respective processing stations  202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214  and  216  and factory interface robot  232  and mainframe robot  220  are generally in communication with a system controller  211 , which may be a microprocessor-based control system configured to receive inputs from both a user and/or various sensors positioned on the cluster tool  200  and appropriately control the operation of cluster tool  200  in accordance with the inputs and/or a predetermined processing recipe. Additionally, the processing stations  202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214  and  216  are also in communication with a fluid delivery system (not shown) configured to supply the necessary processing fluids to the respective processing cell stations during processing, which is also generally under the control of system controller  211 . An exemplary processing fluid delivery system may be found in commonly assigned U.S. patent application Ser. No. 10/438,624, entitled “Multi-Chemistry Electrochemical Processing System,” filed on May 14, 2003, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      Cluster Tool Configurations  
      In an effort to provide a cluster tool that can deposit a seed layer on substrate structures, fill high and low aspect ratio interconnect features with metal and/or selectively form a capping layer over interconnect features, various embodiments of cluster tools may be created. These embodiments are capable of performing one or more of the above processes with high throughput, low defects, minimal oxidation of copper interconnect features and superior adhesion between deposited layers.  
      A. Hybrid Electroless/Electrochemical Plating System  
      1. Applications of Cluster Tool Configuration  
      One embodiment, as illustrated in  FIG. 2 , of a cluster tool  200  generally includes an electroless plating, electrochemical plating, substrate bevel clean, and spin-rinse drying type processing chambers. Optionally, it may include an ALD barrier processing chamber and/or catalytic layer deposition processing chamber located at processing station  235  prior to performing wet processing. Optionally, it may also include a plasma-enhanced dry etch chamber positioned at processing station  235   a  for removal of native oxide prior to barrier or catalytic layer deposition. This configuration of plating cluster tool  200  allows the sequential deposition of multiple films on a substrate within a single cluster tool, for example, an ALD or CVD barrier layer formed on substrate structures, such as tantalum nitride (TaN), an electroless copper seed layer formed on the substrate structures or a barrier layer, and lastly ECP copper fill of interconnect features on the substrate. In one embodiment, the catalytic layer is a Ruthenium-containing layer deposited without the use of carbon-containing precursors. Ruthenium-containing catalytic layers offer superior adhesion to subsequent metal layers over the prior art.  
      This configuration of the cluster tool  200  has advantages over conventional barrier layer, seed layer and gap fill deposition sequences that are performed in separate substrate processing systems, since it reduces the total substrate processing time and hardware costs are greatly reduced. Also, this configuration of plating cluster tool  200  deposits metal layers with improved electrical properties, better defect performance and greater adhesion than metal layers formed on a substrate via multiple substrate processing systems. The sequential formation of a reducing and/or catalytic layer on the barrier layer in the same chamber (i.e., without breaking vacuum) greatly reduces exposure of the barrier layer to oxidation and moisture prior to seed layer deposition, thus improving adhesion of subsequent metal layers. Oxidation of the seed layer surface prior to gap fill deposition is controlled and minimized because gap fill is performed immediately after seed layer formation. Processing substrates in a single cluster tool results in fewer defects compared to processing substrates in multiple processing systems. Hence, this configuration provides better device performance, at a lower cost per substrate processed, and the process is less complicated than the prior art.  
      In one aspect, this configuration allows the sequential deposition of four layers on a substrate: a barrier layer and/or an electroless seed layer formed on substrate structures, followed by electroless fill of sub-micron high aspect ratio features on the substrate, such as high aspect ratio features  111  in  FIG. 1C , followed by ECP fill of low aspect ratio interconnect features on the substrate, such as low aspect ratio feature  112  in  FIG. 1C . This configuration allows an ECP overfill process to fill low aspect ratio features on a substrate immediately after high aspect ratio features on the substrate are filled via an electroless process. The results of an ECP overfill process are illustrated in  FIG. 1E . Referring to  FIG. 1E , substrate structure  110  is shown after the deposition of an electroless seed layer (not shown), an electroless copper film  115 , and an ECP film  116 . Both high and low aspect ratio features ( 111  and  112 , respectively) are filled with copper with minimal oxidation formed between electroless copper film  115  and the ECP film  116 . Hence, with this embodiment, four deposition steps can be performed sequentially in the same cluster tool, thus reducing the number of processing platforms required, minimizing the amount and variation of oxidation that occurs between each deposition step, improving defect performance, improving adhesion of metal films to the barrier layer, and improving electrical properties of deposited metal layers.  
      2. Description of Cluster Tool Configuration  
       FIG. 2  illustrates one embodiment of a cluster tool  200 . In this embodiment, processing station  235  may be configured as an ALD or CVD chamber for the deposition of a barrier layer and/or catalytic layer prior to wet processing. An exemplary ALD chamber is described in greater detail below in conjunction with  FIGS. 14 and 14 A. In one aspect, processing station  235   a  may contain a plasma-enhanced dry etch chamber for removal of native oxide prior to barrier layer deposition. An exemplary dry etch chamber is described in greater detail below in conjunction with  FIG. 19 . Referring to  FIG. 2 , processing stations  214  and  216  may be configured as an interface between wet processing platform  213  and the generally dry processing stations positioned in factory interface  230  of the plating cluster tool  200 . As such, substrates are introduced into wet processing platform  213  by being placed in a holding location, know as an in-station  972  (shown in  FIG. 9A ) which holds substrates for future wet processing. The in-station  972  is typically located above or below processing stations  214  and  216 . In this configuration, the processing stations  214  and  216  may include an SRD chamber that is adapted to perform the final wet processing steps on a substrate before the substrate leaves wet processing platform  213 . An exemplary SRD chamber is described in greater detail below in conjunction with  FIG. 4 .  
      In one embodiment, processing stations  202  and  204  are an electroless plating twin cell, processing stations  206  and  208  are standard IBC chambers, and processing stations  210  and  212  are two ECP cells. This configuration is also shown in  FIG. 2A . An exemplary electroless plating twin cell, IBC chamber and ECP cell are described in greater detail below. These configurations for processing stations  202 / 204 ,  206 / 208 , and  210 / 212  may be rearranged without affecting the functionality of the invention and are defined above only for purposes of description. For example, in order to optimize substrate throughput, the pair of processing stations  202 / 204  and  206 / 208  may both be configured as electroless twin plating cells, the processing stations  210 / 212  may consist of two ECP cells, and processing stations  214  and  216  may be configured as a single SRD and IBC chamber, respectively. The electroless twin cell located at processing stations  202  and  204  is contained by a processing enclosure  302  (described below) and also may include an internal substrate transfer shuttle  605  (described below) for substrate transfers between the first and second processing stations inside each enclosure  302 . ECP cells located at processing stations  210  and  212  are typically not in a processing enclosure  302  and generally do not require an internal substrate transfer shuttle  605  between them.  
      3. Process Sequences  
      a) Electroless Seed and ECP Gap Fill  
      An example of a typical substrate processing sequence for a hybrid electroless/electrochemical plating platform is detailed in the flow chart illustrated in  FIG. 10  and results in the deposition of an electroless seed layer and an ECP gap fill layer on a substrate. As noted above, the exemplary hybrid electroless/electrochemical plating platform is configured with processing stations  202  and  204  as an electroless plating twin cell, processing stations  206  and  208  as IBC chambers, processing stations  210  and  212  as ECP cells, and processing stations  214  and  216  as combination SRD chambers/in-stations (shown in  FIGS. 2 and 2 A). Optionally, processing station  235  is configured as an ALD/CVD pre-treatment chamber and processing station  235   a  is configured as a dry etch or supercritical clean chamber.  
      In Step  1000 , if desired, native oxide and other contaminants are removed from the substrate in a dry etch chamber or supercritical clean chamber positioned at processing station  235   a  and the substrate is then pre-treated with a barrier layer, a reducing layer, and/or a catalytic layer in a chamber positioned at processing station  235  prior to wet processing. The processes for deposition of barrier, reducing and catalytic layers on substrates are described below in conjunction with  FIGS. 1F-1K . The dry etch chamber and process is described below in conjunction with  FIG. 19 . The supercritical clean chamber is described below in conjunction with  FIG. 20 .  
      In step  1001 , factory interface robot  232 , also known as the “dry” robot, places a substrate at the in-station associated with processing stations  214  or  216 . In step  1002 , mainframe robot  220 , also known as the “wet” robot, transfers the substrate to processing station  202  in the electroless plating twin cell. All electroless deposition processes take place in an electroless processing station, such as processing stations  202  and  204 , with the substrate being transferred between processing stations  202  and  204  via internal substrate transfer shuttle  605  as necessary. In process sequences where activation type processes, e.g., preparatory cleaning, activation and post-activation clean steps, are performed, the activation type processes may be performed in the first processing station of the twin plating cell, processing station  202 , and the electroless plating step may be performed in the second processing station, processing station  204 .  
      In some process sequences, the reducing layer and catalytic layer formation steps may be performed in the first processing station, i.e. processing station  202 , and the electroless plating step may be performed in the second processing station, i.e. processing station  204 .  
      In cases where no chemical compatibility issues are present between the various cleaning, activation and plating solutions being used, all electroless deposition can take place in a single processing station. Processing stations  202  and  204  then act as two independent electroless plating cells. In this case, step  1002  includes transferring the substrate from one of the in-stations by mainframe robot  220  to either processing station  202  or  204 . Further, if the substrate has been pre-treated with a catalytic layer in processing station  235  prior to wet processing, processing stations  202  and  204  may also act as two independent electroless plating cells.  
      In step  1003 , mainframe robot  220  transfers the substrate to either of the ECP cells located at processing stations  210  or  212  so that an ECP gap fill process can be performed to fill the interconnect features such as parallel interconnects  101 , 102 , and  103 , illustrated in  FIGS. 1A and 1B .  
      In step  1004 , upon completion of ECP deposition, the substrate is transferred to IBC chamber positioned at station  206  or  208  for removal of the unwanted deposition on the substrate edge and bevel. An exemplary IBC chamber and process are described below in conjunction with  FIG. 3 . An exemplary IBC chamber and process are described more fully in commonly assigned U.S. patent application Ser. No. 10/826,492, entitled “Integrated Bevel Clean Chamber,” filed on Apr. 16, 2004, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      In step  1005 , mainframe robot  220  transfers the substrate to SRD chamber positioned at processing stations  214  or  216  for final rinsing and drying. An exemplary SRD chamber and process are described below in conjunction with  FIG. 4 . A description of an exemplary SRD chamber that may be used in embodiments of the invention may be found in commonly assigned U.S. application Ser. No. 10/616,284 entitled “Multi-Chemistry Plating System,” filed on Jul. 8, 2004, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      In step  1006 , after the SRD process is complete, factory interface robot  232  removes the substrate from the SRD and the wet processing platform  213 .  
      Hence, this embodiment of plating cluster tool  200  allows the sequential deposition of an electroless seed layer on a substrate followed by ECP fill of interconnect features on the substrate. Optionally, a barrier and or catalytic layer may be deposited on the substrate immediately prior to wet processing, improving adhesion of the subsequent metal layers. This configuration thus allows the amount and variation of oxidation of the seed layer prior to gap fill deposition to be minimized and also reduces the number of processing platforms required to complete three deposition steps on a substrate structure.  
      In one embodiment, in an effort to maximize substrate processing throughput, the cluster tool  200  may be configured to include two electroless twin plating cells instead of one electroless twin plating cell. In the configuration, the cluster tool may contain, for example, two electroless twin plating cells located at processing stations  202 / 204  and  206 / 208 , two ECP cells located at processing stations  210 / 212 , a single IBC chamber at processing station  216  and a single SRD chamber at processing station  214 . The same substrate processing sequence in  FIG. 10  is followed.  
      b) Electroless Gap Fill and ECP Overfill  
      Alternately, the hybrid electroless/electrochemical plating configuration may be used for electroless gap fill of high aspect ratio features and then ECP overfill of low aspect ratio features, as illustrated in  FIG. 1E . The substrate processing sequence is similar to the sequence shown in  FIG. 10 , except step  1002 . In addition to ALD deposition of a barrier layer and electroless deposition of a seed layer, step  1002  may also include an electroless gap fill of high aspect ratio features step on a substrate. Hence, this configuration of the cluster tool  200  allows the sequential deposition of an ALD barrier layer, an electroless seed layer, and an ECP gap fill layer or the sequential deposition of an ALD barrier layer, an electroless seed layer and electroless gap fill of high aspect ratio features, followed by ECP gap fill of large, low aspect ratio features. In each case, both the amount and variation of oxidation of the first copper layer prior to ECP gap fill are minimized and only a single processing platform is required to complete three or four deposition steps on a substrate structure. Adhesion of metal layers to the TaN barrier is also improved.  
      In one aspect, the electroless gap fill of high aspect ratio contacts to a source or drain connection point may include the selective deposition of cobalt- or nickel-based alloys. Such a high aspect ratio contact is similar to aperture  122  and contact layer  123  in  FIG. 1F , except that in this instance contact layer  123  consists of a doped-silicon source or drain connection. Preferably, an initial thin layer of nickel or cobalt is deposited at the bottom of the source or drain contact to form a nickel or cobalt silicide covering contact layer  123 . This may obviate the need for a barrier layer between the source or drain connection point and the bulk conductive layer, i.e., bulk layer  130 , in  FIG. 1K , since the nickel silicide may prevent further silicidation of the source or drain, i.e., contact layer  123 , by stopping diffusion of the bulk layer  130  into the contact layer  123  and the formation of a silicide during subsequent process steps. Preferably, the bulk layer  130  is deposited in the same process chamber immediately after the initial thin layer of cobalt or nickel is formed at the bottom of the high aspect ratio contact to minimize oxidation. Both of these deposition steps take place in step  1002  as shown in  FIG. 10 .  
      In another aspect, the electroless gap fill of high aspect ratio features  111  shown in  FIG. 1C  may be completed by a selective electroless deposition process. The substrate processing sequence is similar to the sequence shown in  FIG. 10 , except that step  1002  consists of a bottom-up electroless fill process rather than a conformal fill process. A description of an exemplary bottom-up deposition process that may be used in embodiments of the invention may be found in commonly assigned U.S. application Ser. No. 60/663,493 [9916L] entitled “Deposition Processes Within a High Aspect Ratio Contact,” filed on Mar. 18, 2005, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      4. Description of Process Chambers  
      Embodiments of the invention include the incorporation of multiple substrate processing chambers onto a single cluster tool, including ECP, IBC, SRD, electroless, plasma-enhanced dry etch, and ALD or CVD chambers. Examples of these chambers and the processes performed on substrates therein are provided below.  
      a) ECP Cell  
      In one aspect of the invention, process step  1003  is performed in ECP cells that are used to fill interconnect structures on substrates with a conductive material, such as copper. ECP plating processes are generally two stage processes. A seed layer is first formed over the surface features of the substrate via PVD, CVD, or ALD processes. Then the surface features of the substrate are exposed to an electrolyte solution while an electrical bias is applied between the seed layer and a copper anode positioned within the electrolyte solution. The electrolyte solution contains ions to be plated onto the surface of the substrate and the application of a cathodic type electrical bias causes these ions in the electrolyte solution to be plated onto the seed layer. Conventional electro-chemical plating cells generally utilize an overflow weir-type plater containing a plating solution, generally termed a catholyte solution. The substrate is positioned facedown in the catholyte solution during plating and an electrical plating bias is applied between the substrate and an anode positioned in a lower portion of the plating cell. This bias causes metal ions in the catholyte to go through a reduction that causes the ions to be plated on the substrate. Transferring substrates to and from such a facedown plating cell configuration generally requires a robot, such as mainframe robot  220 , that is capable of rotating substrates from faceup to face down and vice versa.  
       FIG. 2B  illustrates a sectional view of an exemplary plating cell, hereinafter referred to as plating cell  200 B. The plating cell  200 B generally includes a plating head assembly  210 B, a frame member  203 B, an outer basin  201 B and an inner basin  202 B positioned within outer basin  201 B. The plating head assembly  210 B includes a rotatable contact ring  211 B for supporting and rotating a substrate during immersion into the catholyte solution and during plating. The rotatable contact ring  211 B may be adapted to make electrical contact around the periphery of the substrate so that the necessary electrical plating bias may be applied to the substrate. The frame member  203 B of plating cell  200 B supports an annular base member  204 B on an upper portion thereof. Base member  204 B includes a disk-shaped anode  205 B. Inner basin  202 B is generally configured to contain a catholyte solution that is used to plate a metal, e.g., copper, onto a substrate during an electrochemical plating process. During the plating process, the plating solution is generally continuously supplied to inner basin  202 B, and therefore, the plating solution continually overflows the uppermost point  206 B, generally termed a “weir”, of inner basin  202 B and is collected by outer basin  201 B and drained therefrom for chemical management and re-circulation. Plating cell  200 B may be positioned at a tilt angle, i.e., the frame member  203 B of plating cell  200 B may be elevated on one side such that the components of plating cell  200 B are tilted between about 3° and about 30°. Since frame member  203 B is elevated on one side, the upper surface of base member  204 B is generally tilted from the horizontal at an angle that corresponds to the tilt angle of frame member  203 B relative to a horizontal position.  
      In an exemplary ECP process, a substrate may be transferred into a plating cell, such as plating cell  200 B for example, and positioned face-down on rotatable contact ring  211 B. Plating head assembly  210 B moves downward until the substrate is immersed in the catholyte solution filling inner basin  202 B, typically while being rotated by the rotatable contact ring  211 B between about 5 rpm and about 60 rpm. The catholyte solution may have between about 5 g/l and 50 g/l of sulfuric acid, a copper concentration between about 25 g/l and 70 g/l, and a chlorine concentration between about 30 ppm and about 60 ppm. The catholyte solution may also include additional additives, such as levelers, suppressors, or accelerators. During plating, a plating bias, typically between about 1 VDC and about 10 VDC, is applied to the substrate. The substrate may be rotated between about 10 rpm and about 100 rpm during the plating process step by rotatable contact ring  211 B. Plating takes place for between about 30 sec and about 5 minutes, depending on the thickness of plated film desired. The plating bias is then removed and the substrate is positioned above the catholyte solution and uppermost point  206 B of inner basin  202 B for removal from plating cell  200 B. Prior to removal from plating cell  200 B, the substrate may be rotated between about 100 and 1000 rpm for between about 1 second and about 10 seconds in order to remove excess catholyte solution from the substrate. An exemplary ECP cell and plating process is further described in commonly assigned U.S. patent application Ser. No. 10/627,336 entitled “Electrochemical Processing Cell,” filed on Jul. 24, 2003, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      b) IBC Chamber  
      In one aspect of the invention, IBC chambers are used for removing deposition at the edge, or bevel, of a substrate and unwanted contamination from the backside of a substrate without damaging structures formed on one or more surfaces of the substrate. This process is generally performed on a substrate after a conductive material has been deposited on the substrate, such as ECP processes or electroless deposition processes. IBC chambers typically include a container, a rotatable substrate support disposed in the container and capable of rotating a substrate at a relatively high rotational velocity, i.e., 500 rpm or higher, and a fluid delivery assembly configured to precisely deliver a liquid etchant to a peripheral portion of the substrate and to deliver a rinsing agent, such as de-ionized (Dl) water, to the entire substrate.  
      In operation, the IBC chamber can be used to rinse and clean substrates. The cleaning operation may be conducted on both the production surface and the non-production surface of the substrate, or on either surface individually. The cleaning chamber may also be used to clean excess material from the bevel portion of the substrates, i.e., the portion of the conductive layer deposited near the perimeter on the production surface, or topside, and partially onto the backside of the substrate. This process is often termed bevel clean or edge bead removal in the semiconductor art. In another embodiment, the IBC chamber may be used as a combination IBC/SRD chamber, wherein the final rinse and dry function of an SRD chamber, described below and in conjunction with  FIG. 4 , is incorporated into an exemplary IBC chamber  300  described below in conjunction with  FIG. 3 . No additional features are required to perform the final rinse and dry function of an SRD chamber in the exemplary IBC chamber  300  as described below.  
       FIG. 3  illustrates an isometric view of an exemplary IBC chamber  300 . The upper components of the exemplary IBC chamber  300  generally include a chamber bowl or chamber having a drain basin  309  in communication with the lower portion of wall  301 . The chamber bowl is generally manufactured from a plastic material, a nylon-type material, or metal material coated with a non-metal. The material is generally selected to be non-reactive with the etchant solutions that are used to remove a desired material from the substrate surface. Drain basin  309  is generally configured to receive a processing fluid thereon, and channel the processing fluid to a fluid drain (not shown). A central portion of drain basin  309  includes a substrate chuck  303 , which is configured to rotate substrates being processed in the chamber and/or actuate them vertically. Drain basin  309  also includes a plurality of substrate centering pins  304  extending upward therefrom. Substrate centering pins  304  are generally positioned radially around the perimeter of drain basin  309  in an equal spacing arrangement, for example and are designed to precisely locate the substrate in the chamber for optimum cleaning of the bevel. Exemplary IBC chamber  300  further includes at least one rinsing solution dispensing arm  305 , along with at least one etching solution dispensing arm  306 . Generally, both rinsing solution dispensing arm  305  and etching solution dispensing arm  306  are pivotally mounted to a perimeter portion of exemplary IBC chamber  300 , and include a longitudinally extending arm having at least one fluid dispensing nozzle positioned on a distal terminating in thereof. The nozzles are positioned to dispense the respective processing fluids onto a first or upper side of a substrate positioned on the substrate chuck  303 . The operation of rinsing solution dispensing arm  305  and etching solution dispensing arm  306  is generally controlled by a system controller, which is configured to precisely position (via pivotal actuation and/or vertical actuation of the respective arms) the distal end of the respective arms over a specified radial position of a substrate being processed, which allows for fluid dispensed from the nozzles positioned at the respective ends of arms  306  and  306  to be dispensed onto precise radial locations of a substrate being processed in exemplary IBC chamber  300 . The fluids dispensed on the substrate may be a rinsing solution, e.g., Dl water, or acid solution, e.g., an H 2 SO 4 -containing solution. Further, rinsing solution dispensing arm  305  and etching solution dispensing arm  306  may include a mechanism configured to prevent fluid leakage from the nozzles when the nozzles are not activated. For example, the nozzles may include a vacuum port or suck back valve (not shown) that is configured to receive unwanted fluid drips during off times. Alternatively, nozzles may include a gas aperture that is configured to blow unwanted droplets of fluid away from the substrate surface.  
      In a typical bevel clean, or IBC process, a substrate is positioned face-up in an IBC chamber, such as IBC  300 . The process of positioning a substrate in IBC  300  generally includes insertion, centering, and chucking. The insertion process is conducted by a substrate transfer robot, such as mainframe robot  220 . Centering is performed by substrate centering pins  304 . A vacuum chuck then holds substrate in place throughout processing. The pre-rinse process includes rotating the substrate between about 150 rpm and about 250 rpm between about 8 seconds and 20 seconds while Dl water is dispensed onto the topside of the substrate via rinsing solution dispensing arm  305  at a flow rate of between about 1 l/min and 2 l/min. The substrate is then rotated between about 2000 rpm and about 3500 rpm for about 5 seconds to remove residual Dl water. An etchant solution is then applied to the bevel of the substrate via etching solution dispensing arm  306  for between about 10 seconds and about 25 seconds at a flow rate of between about 20 cc/min and about 40 cc/min. The flow of etchant solution may be through a relatively fine nozzle having an aperture with an inner diameter between about 0.25 and 0.5 inches. The nozzle is positioned between about 1 mm and 3 mm from the substrate surface for precise dispensing of etchant solution onto the substrate bevel. A typical etchant solution consists of between about 15 and 25 parts H 2 SO 4 , between about 350 and 450 parts H 2 O 2  and about 1400 parts H 2 O. After etchant dispense is complete, rinsing solution is dispensed onto the topside of the substrate at a flow rate of between about 1 l/min and about 2.5 l/min for between about 3 seconds and about 10 seconds while the substrate is rotated between about 100 rpm and 300 rpm. After this rinse step, all liquid dispense is terminated and the substrate is rotated between about 400 rpm and about 4000 rpm to partially or completely dry the substrate.  
      An exemplary IBC chamber and bevel cleaning method is described in more detail in commonly assigned U.S. patent application Ser. No. 10/826,492, entitled “Integrated Bevel Clean Chamber,” filed on Apr. 16, 2004, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      In addition to substrate bevel cleaning, rinsing, and drying, the IBC chamber described above in conjunction with  FIG. 3  may also perform other wet processes on substrates, such as an SC-1 clean for removing organic contaminants, an HF-based native oxide clean, or an acid strip process, all of which are described below in conjunction with FIGS.  21 A-F.  
      c) SRD Chamber  
      In one embodiment of the invention, ie., a hybrid electroless/ electrochemical plating platform, SRD chambers are used for the final rinse and spin dry of substrates after wet processing. In operation, SRD chambers generally operate to receive a substrate therein, rinse the substrate with a rinsing fluid, and dry the substrate via spinning the substrate to centrifugally urge fluid off of the substrate surface, while optionally dispensing a drying gas into the cell containing the substrate to further facilitate the drying process. This process is typically performed after completing all wet processing steps on a substrate and immediately prior to transferring the substrate from a wet processing region of a cluster tool.  
       FIG. 4  illustrates a partial perspective and sectional view of SRD  400 , an exemplary substrate spin rinse dry chamber  400 . SRD  400  includes a fluid bowl  401 . SRD  400  further includes a rotatable hub  402  centrally positioned in the fluid bowl  401 . Rotatable hub  402  includes a generally planar upper surface that has a plurality of backside fluid dispensing nozzles  408  formed thereon and at least one gas dispensing nozzle  410  formed thereon. A plurality of upstanding substrate support fingers  403  are positioned radially around the perimeter of rotatable hub  402 . Fingers  403  are configured to rotatably support a substrate  404  at the bevel edge thereof for processing in SRD  400 . A fluid dispensing arm  450  may be pivotally mounted to the side wall such that a distal end of the arm having a fluid dispensing nozzle positioned thereon may be pivoted to a position over a substrate being processed in the chamber. The fluid dispensing arm  450  is configured to pivot outward over the substrate surface and dispense a processing fluid, typically Dl water, onto the substrate surface proximate the center of the substrate. As noted above, in some embodiments of substrate plating cluster tool, the SRD function as described in exemplary SRD chamber  400  can instead be integrated into an IBC chamber without modifying the exemplary IBC chamber  300 . A more detailed description of an exemplary SRD chamber that may be used in embodiments of the invention may be found in previously referenced U.S. application Ser. No. 10/616,284 entitled “Multi-Chemistry Plating System,” filed on Jul. 8, 2003.  
      In a typical SRD process, a substrate is positioned face-up in an SRD chamber, such as SRD  400 , on support fingers  403 . In the pre-rinse step, rotatable hub  402  spins the substrate between about 900 rpm and 1700 rpm for between about 2 seconds and about 6 seconds while between about 600 ml and about 1500 ml is dispensed onto the topside and the backside of the substrate via fluid dispensing arm  550  and backside fluid dispensing nozzles  408 . In the backside clean step, rotatable hub  402  rotates the substrate between about 40 rpm and 90 rpm for between about 10 seconds and about 20 seconds while between about 200 ml and 500 ml of a cleaning solution, such as ElectraClean™ solution, is applied to the substrate backside and between about 1000 ml and about 1500 ml of rinsing solution is dispensed onto the topside of the substrate. In the post rinse step, between about 1000 ml and 1500 ml of rinsing solution is dispensed on the substrate topside and between about 600 ml and about 1000 ml of rinsing solution is dispensed on the substrate backside while the substrate is rotated at between about 40 rpm and about 90 rpm for about 10 seconds to 16 seconds. In the dry step, all liquid flow is terminated and the substrate is rotated at between 2000 rpm and about 3000 rpm for between about 10 seconds and about 20 seconds. Optionally, between about 2 cfm and about 4 cfm of a dry purge gas may be introduced into the chamber during this step for about 4 seconds to enhance the substrate drying process.  
      d) Electroless Plating Chambers  
      Generally, embodiments of the cluster tool include at least one electroless plating cell. In one aspect, a pair of electroless plating cells are grouped together to advantageously perform an electroless deposition process on a substrate. The pair of electroless plating cells, or electroless plating twin cell, comprise two substrate processing cells positioned on the wet processing platform  213  (see  FIG. 2 ) inside one of the processing enclosures  302 . Processing enclosure  302  is described more fully below in conjunction with  FIG. 6 . Each pair of cells may include electroless plating or plating support cells, e.g., electroless plating cells, electroless activation cells, and/or substrate rinse or clean cells.  
      In one embodiment, in each processing enclosure  302  there may be two independent electroless plating cells in which the necessary pre-deposition, deposition, and post-deposition processes are all carried out on a substrate in each cell. In this configuration, substrates are transferred into, processed, and transferred out of each processing cell independently.  
      Alternately, the two cells inside a processing enclosure  302  may comprise a sequential electroless twin cell, wherein one cell is an activation cell, the other is an electroless deposition cell, and the substrate is transferred from the activation cell to the deposition cell via a robot internal to processing enclosure  302 . Hence, the entire series of processes required to perform electroless deposition on a substrate, i.e., activation, pre-cleaning, electroless deposition, and post cleaning, is carried out inside a single processing enclosure  302 , but the individual processes are divided between the two processing cells that comprise the twin electroless plating cell.  
       FIG. 6  is a perspective view of an exemplary electroless twin cell with the substrate processing hardware of the electroless plating cells omitted for clarity. In this embodiment, processing stations  210  and  212  (as defined in  FIG. 2 ) are shown in an processing enclosure  302 , however other processing chamber station pairs on wet processing platform  213  may be also operate as electroless twin cells, depending on the embodiment of the invention. An processing enclosure  302  defines a controlled processing environment around the pair of processing stations  210  and  212 . The processing enclosure  302  may include a central interior wall  608  that generally bisects the processing volume into two equally sized processing volumes, processing volume  612  and processing volume  613 . Although the central interior wall  608  is optional, when it is implemented, the central interior wall  608  generally creates a processing volume  612  above processing station  210  and a processing volume  613  above processing station  212 . The processing volumes  612  and  613  are substantially isolated from each other by the central interior wall  608 , however, a lower portion of the central interior wall  608  includes a slot  610  formed therein. The slot  610  is sized to accommodate an internal substrate transfer shuttle  605  that is positioned between processing stations  210  and  212 . The internal substrate transfer shuttle  605  is generally configured to transfer substrates between the respective processing stations ( 210     212 ) without requiring the use of the mainframe robot  220 . Internal substrate transfer shuttle  605  may be a vacuum chuck-type substrate support member that is configured to pivot about a point such that a distal substrate supporting end of internal substrate transfer shuttle  605  moves in the direction of arrow  603  (shown in  FIG. 2 ) to transfer substrates between the respective processing stations  210  and  212 . The processing volumes  612  and  613  also include a valved port  604  that is configured to allow a robot, such as mainframe robot  220  to access the respective processing volumes  612  or  613  to insert and remove substrates therefrom.  
      Each processing enclosure  302  also includes an environmental control assembly  615  (shown in  FIG. 6  removed from contact with the processing enclosure  302  for clarity) positioned on an upper portion of the processing volumes  612  and  613 . The environmental control assembly  615  includes a processing gas source configured to provide a processing gas to the processing volumes  612  and  613 . The processing gas source is generally configured to provide a controlled volume of an inert gas, such as nitrogen, helium, hydrogen, argon, and/or mixtures of these or other gases commonly used in semiconductor processing, to the processing volumes  612  and  613 . Thus, environmental control assembly  615  purges the interior of processing volumes  612  and  613  of gases that may degrade the electroless plating process, such as oxygen. The environmental control assembly  615  further includes a particle filtration system, such as a HEPA-type filtration system. The particle filtration system is used to remove particulate contaminants from the process gas entering the processing volumes  612  and  613 . The particle filtration system is also used to generate a generally linear and equal flow of the processing gas toward processing stations below. The environmental control assembly  615  may further include devices configured to control humidity, temperature, pressure, etc. in the respective processing volumes  612  and  613 . The system controller  211  may be used to regulate the operation of the environmental control assembly and exhaust port  614 , along with other components of the cluster tool  200  (shown in  FIG. 2 ), to control the oxygen content within the processing volumes  612  and  613  in accordance with either a processing recipe or inputs received from sensors or detectors (not shown) positioned in the processing volumes  612  and  613 . Each processing station (processing stations  210  and  212  in  FIG. 2 ) inside a processing enclosure  302  also includes at least one exhaust port  614 , which is positioned to facilitate uniform flow of the processing gas from the gas supply in environmental control assembly  615  toward the processing stations  210  and  212  respectively. Optionally, multiple radially positioned ports (not shown) may be instead be positioned around the processing stations  210  and  212 .  
      The combination of the environmental control assembly  615 , the exhaust port  614 , and the system controller  211  also allows cluster tool  200  to control the oxygen content of the processing volumes  612  and  613  during specific processing steps, wherein one processing step may require a first oxygen content for optimal results and a second processing step may require a second oxygen content for optimal results, where the first and second oxygen contents are different from each other. In addition to the oxygen content, system controller  211  may be configured to control other environmental parameters of the processing enclosure, such as temperature, humidity, pressure, etc. as desired for a particular processing sequence. These specific parameters may be modified by heaters, chillers, humidifiers, dehumidifiers, vacuum pumps, gas sources, air filters, fans, etc., all of which may be included in the environmental control assembly  615  and positioned in fluid communication with the processing volumes  612  and  613  and controlled by the system controller  211 . Hence, processing enclosure  302  provides an environmentally controlled enclosure for each electroless deposition cell therein.  
      i) Selective Electroless Plating Process  
      A selective electroless deposition process sequence, e.g., the capping layer process or bottom-up contact fill, generally includes preparatory cleaning, electroless deposition, post-deposition clean, and optionally cleaning the bevel edge of the substrate. In one aspect, the selective deposition process may include activation and post-activation clean steps. The selective electroless deposition process may be performed in exemplary electroless twin cells located at processing stations  210  and  212  as described above. In addition, vapor drying of the substrate may also be performed as part of the process sequence before or between preparatory cleaning steps, immediately prior to the electroless deposition step, or subsequent to substrate bevel clean. An exemplary vapor dryer method and apparatus is described below.  
      A selective electroless deposition process sequence  500  for forming a capping layer on a copper-filled interconnect is illustrated in  FIG. 5A  and described below.  
      Step  501 , Preparatory Cleaning: When selectively depositing a layer on interconnect features, preparatory cleaning is necessary to ensure that no metallic residues are present on exposed dielectric surfaces of the substrate structure prior to electroless deposition. As illustrated in  FIGS. 1A and 1B , if metallic residues are not removed, electroless deposition of the capping material may occur on these metallic residues and possibly cause an electrical short between the devices formed on or above the substrate structure  100 . Preparatory cleaning also removes surface oxides and residues from previous process steps from the metallic surfaces of the substrate structure that may inhibit the electroless deposition process. Preparatory cleaning steps may include application of a dielectric clean solution to the substrate structure, brush cleaning of the substrate surface either in situ or in an external brush box chamber, application of megasonic or ultrasonic energy to the substrate structure, and application of a metal cleaning solution to the substrate structure. Rinsing and vapor drying may generally be performed after any of these steps.  
      In a typical preparatory cleaning process, a substrate is transferred into an electroless deposition chamber or activation chamber—as described below in conjunction with  FIGS. 7 and 8 —and a dielectric clean solution is applied to the surface of the substrate at approximately 20° C. and subsequently rinsed off with a rinsing solution. The dielectric clean solution may include one or more acids, such as citric acid, HF, and/or HCI, as well as corrosion inhibitors to prevent corrosion of exposed conductive surfaces on the substrate. A preferred aqueous pre-clean solution may contain citric acid with a pH value from about 1.7 to about 3.0. More heavily oxidized surfaces generally require longer cleaning times and/or a lower pH value pre-clean solution. The rinsing solution is typically Dl water. The substrate is rotated in the chamber via a rotatable substrate support between about 50 and 200 rpm during the application of the dielectric clean solution and rinsing solution and is then rotated between about 500 and 2000 rpm to substantially remove the rinsing solution. The dielectric clean solution and the rinsing solution are applied using one or more fluid dispensing arms, described below in conjunction with  FIG. 8 . Specific cleaning solution application times and concentrations vary depending on the material make-up of substrate structure  100  and parallel interconnects  101 ,  102 , and  103  (see  FIG. 1A ). Generally, a thickness of less than about 50 Å from the parallel interconnects  101 ,  102  and  103  and the substrate structure  100  is etched by the dielectric clean solution.  
      A description of dielectric solution chemistries and processes of cleaning the substrate structure as described herein may be found in commonly assigned U.S. patent application Ser. No. 10/970,839, entitled, “Electroless Cobalt Alloy Deposition Process,” filed on Oct. 21, 2004, and commonly assigned U.S. patent application Ser. No. 10/967,644, entitled, “Selective Self-initiating Electroless Capping of Copper With Cobalt-Containing Alloys,” filed Oct. 15, 2004, both of which are incorporated by reference herein to the extent not inconsistent with the claimed aspects and description herein. An exemplary apparatus and method for in situ brush cleaning of substrates and suitable metal cleaning solutions are disclosed in commonly assigned U.S. patent application Ser. No. 11/004,014, entitled “Method And Apparatus For Electroless Capping With Vapor Drying,” filed on Dec. 2, 2004, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention. For situations when in situ brush cleaning is not performed in the electroless twin cell, an exemplary brush box chamber for brush cleaning of substrates is described below in conjunction with  FIG. 8A .  
      Step  502 , Activation: When an activation step is used, the electroless deposition process generally involves the application of an activation solution to the surface of the substrate structure, which deposits an activation metal seed layer on all the exposed metal portions of a substrate structure, for example the top surfaces of parallel interconnects  101 ,  102 , and  103  in  FIG. 1A . Any oxidation of the exposed metal portions of a substrate structure after the above cleaning processes may be detrimental to proper deposition of the activation seed layer. Therefore, a short waiting time, i.e., less than about 15 seconds, is desired between the preparatory cleaning of the substrate and the application of the activation seed layer and these two process steps are preferably performed sequentially in the same chamber. The presence of a substantially inert gas environment also minimizes oxidation of exposed metal surfaces after preparatory cleaning and prior to activation seed layer deposition. Due to incompatibilities of the chemistries typically used in the metal cleaning step and the activation step, in some cases these processes may be carried out in two or more different processing stations, for example  210  and  212  in environmentally controlled processing enclosure  302  ( FIG. 2 ). Hence, an electroless plating twin cell allows preparatory cleaning and activation steps to be performed on a substrate in different processing stations with very little oxidation. The waiting time between processes in processing stations  210  and  212  is short; only a few seconds are required for the substrate to be transferred between the processing stations  210  and  212 . The low oxygen environment inside processing enclosure  302  further minimizes unwanted oxidation of the substrate structure after preparatory cleaning in processing station  210  and prior to activation seed layer deposition in processing stations  212 . It is important to note that when there are no chemical incompatibilities between the chemistries used in the various steps of the electroless plating process, i.e., the dielectric clean, metal clean, activation, post-activation clean, deposition, and post-deposition clean, then the entire electroless plating process may be carried out in the same processing station. Hence, processing stations  210  and  212  can instead be used as two independent electroless processing stations and no substrate transfer between the two is required.  
      In a typical activation process, the substrate has just been transferred into an electroless deposition chamber as described above. The substrate is rotated between about 50 and 200 rpm and an activation solution is applied to the surface at approximately 20° C. via one or more fluid dispensing arms, described below in conjunction with  FIG. 8 . The application time necessary to form a suitable activation metal seed layer varies depending on activation solution concentration and composition, but is generally between about 30 seconds and 1 minute. A description of chemistries and methods for performing an activation process may be found in previously referenced U.S. patent application Ser. No. 10/970,839, entitled, “Electroless Cobalt Alloy Deposition Process” and in U.S. patent application Ser. No. 10/967,644, entitled, “Selective Self-Initiating Electroless Capping of Copper With Cobalt-Containing Alloys.” 
      Step  503 , Post Activation Clean: Post-activation clean may be performed by applying a post-activation clean solution to the substrate structure as well as optionally brushing the substrate structure and/or applying ultrasonic or megasonic energy to the substrate structure. Post activation solutions typically include one or more acids, requiring this step to be performed in a processing station  210  or  212  that only uses other compatible chemistries. As noted above, the entire electroless deposition process may be performed on a substrate in either processing station  210  or  212  if there are no chemical compatibility issues between any of the processing solutions.  
      For a post activation clean process that does not involve brushing of the substrate structure or the application of ultrasonic or megasonic energy, the substrate is typically rotated via a rotatable substrate support between about 50 and 200 rpm while a post-activation clean solution is applied to the substrate surface and subsequently rinsed off using one or more fluid application arms. Application time of the post-activation clean solution varies depending on the concentrations and composition of the activation solution and post-activation clean solution, but is typically about 30 seconds to 2 minutes in length. Substrate brush cleaning and/or ultrasonic or megasonic cleaning may take place in a dedicated cleaning chamber, such as a brush box chamber, described below in conjunction with  FIG. 8A . The post-activation clean removes any excess activation solution so that when depositing a capping layer, the activation metal seed layer remains primarily on the exposed portions of interconnect features. Remaining activation solution on the dielectric portions of the substrate structure may cause undesirable electroless deposition. A short waiting time between the end of the activation process and the post-activation clean is also beneficial for the electroless plating process and generally both steps are performed sequentially in the same processing station.  
      Step  504 , Electroless Deposition: A conductive layer may be deposited by application of an electroless deposition solution to the substrate structure. When an activation step is used, the deposition takes place on the activation metal seed layer. This step may be conducted in one or both of the processing stations  210  or  212  located in processing enclosure  302 . Metals that may be deposited include copper, cobalt and nickel, among others. Since the electroless deposition process is highly temperature dependent, temperature control of the substrate and deposition solution is critical to the process and methods and apparatus for temperature control in an exemplary electroless deposition processing station are detailed below in conjunction with  FIGS. 7 and 8 . A more detailed description of chemistries, processes, and methods for depositing an activation metal seed layer, completing a post-activation clean step, and depositing an electroless layer may be found in previously referenced U.S. patent application Ser. No. 10/970,839, entitled, “Electroless Cobalt Alloy Deposition Process” and in U.S. patent application Ser. No. 10/967,644, entitled, “Selective Self-Initiating Electroless Capping of Copper With Cobalt-Containing Alloys,” filed Oct. 21, 2004.  
      Step  505 , Post-Deposition Clean: As stated above, it is critical to remove conductive material that has accumulated on dielectric surfaces of a substrate structure during the electroless deposition process when forming a capping layer. A post-deposition clean process may be performed by applying a post-deposition clean solution to the substrate structure subsequent to electroless deposition. The post-deposition clean solution may be applied to the surface of the substrate via one or more fluid delivery arms for 1 to 60 seconds while the substrate is rotated between about 50 and 500 rpm. Post-deposition clean solutions may be slightly acidic clean solutions, such as ElectraClean™ solution, available from Applied Materials Inc. of Santa Clara, Calif. or a CX-100 solution available from Wako Chemicals USA, Inc. of Richmond, Va. Alternately, the post-deposition clean solution may be slightly basic,i.e., with a pH value between about 7.5 and 9.5. Additionally, scrubbing the surface of the substrate with a brush-like material and/or applying sonic energy to the substrate structure may also be part of the post-deposition clean process. Both substrate scrubbing and sonic cleaning may be performed in-situ but are typically performed in a dedicated post-deposition clean chamber, such as a brush box.  
      In a typical post-deposition clean process, the substrate is rotated between about 50 and 200 rpm in the deposition chamber via a rotatable substrate support and an electroless deposition solution is applied to the surface via one or more fluid dispensing arms for about 1 to 60 seconds. The substrate is then rinsed in-situ, i.e., rotated between about 50 and 200 rpm while rinse solution is applied to the substrate surface. The substrate is then spun dry, i.e., rotated between about 500 and about 2000 rpm for between about 5 seconds and 60 seconds. The substrate is then removed from the electroless deposition chamber and transferred to a brush box chamber integrated on the wet processing platform of the invention and external to the electroless plating twin cell. In the brush box chamber, the surface of the substrate is brush cleaned using roller-type brushing devices. An exemplary brush box chamber is described below in conjunction with  FIG. 8A . A detailed description of solutions that may be used for this process as well as an exemplary apparatus and method for in situ brush cleaning of substrates and suitable metal cleaning solutions may be found in previously referenced U.S. patent application Ser. No. 11/004,014, entitled “Method And Apparatus For Electroless Capping With Vapor Drying.” 
      Step  506 , Bevel Clean: The portion of the conductive layer deposited near the perimeter on the topside, on the substrate bevel, and partially onto the backside of the substrate may be removed by means of an IBC chamber, described above in conjunction with  FIG. 3 , or in-situ. Unwanted process residues and deposition may also be removed from the backside of the substrate during this step. An exemplary method and apparatus for performing a bevel clean process in an IBC chamber is described above in conjunction with  FIG. 3 .  
      Alternatively, process sequence  520  in  FIG. 5C  illustrates a selective electroless deposition process sequence for bottom-up contact fill with nickel or cobalt-tungsten alloy, such as for high aspect ratio features  111  shown in  FIG. 1C . The process steps are illustrated in  FIG. 5C  and described below.  
      Step  521 , Pre-treatment: Removal of native oxides on contact surfaces is necessary prior to electroless deposition for acceptable contact resistance for high aspect ratio features. Aspects of the invention may use a plasma-enhanced dry etch chamber, described below in conjunction with  FIG. 19 , or a super-critical clean chamber, described below in conjunction with  FIG. 20 , positioned in processing station  235  or  235   a  for native oxide removal. Alternately, a plasma pre-treatment process, such as a plasma-soak process, may be conducted in a process chamber capable of plasma vapor deposition, wherein the contact surface is exposed to a reducing plasma or reducing vapor in an ALD or CVD chamber positioned in processing station  235  or  235   a . An exemplary plasma pre-treatment process and an exemplary vapor pre-treatment process that may be used in embodiments of the invention are described below in conjunction with  FIGS. 14 and 14 A, and in previously referenced U.S. patent application Ser. No. 60/663,493 [9916L]. In another aspect, the substrate surface is exposed to a wet clean process to remove native oxides formed thereon. The wet clean process may be an in situ process performed in the same processing cell as a subsequent electroless deposition process.  
      Step  522 , Ruthenium-Containing Layer Formation: A ruthenium-containing layer, preferably ruthenium oxide, is selectively deposited on the contact surface by exposing the substrate to a ruthenium tetroxide vapor. The ruthenium-containing layer may be deposited on the substrate by use of a vapor deposition process, such as an in situ generated process, or in a liquid deposition process, such as an aqueous solution or suspension. The former method may be performed in an ALD or CVD deposition chamber positioned at processing station  235  or  235   a , preferably in the same chamber wherein step  521  is performed on the substrate. The latter method, i.e., the liquid deposition process, may be performed in the same processing cell as the aqueous cleaning method described in step  521 . Ruthenium tetroxide is a strong oxidant and therefore readily reacts with any exposed metal oxide layers (e.g., tungsten oxide and other contact layer materials) to form a consistent and catalytic active layer of ruthenium oxide selectively on the bottom of the contact. Formation of a ruthenium-containing layer on a substrate is described in greater detail below in conjunction with  FIG. 14A  and in previously referenced U.S. patent application Ser. No. 60/663,493 [9916L].  
      Step  523 , Ruthenium-Containing Layer Reduction: The ruthenium-containing layer, preferably ruthenium oxide, is exposed to a reductant, forming a catalytic ruthenium metal layer on the bottom surface of the contact. The ruthenium oxide layer may be exposed to a reducing plasma, such as a hydrogen-containing plasma, to form metallic ruthenium layer from the ruthenium-containing layer on the bottom surface of the contact. This process may be performed in an ALD or CVD deposition chamber positioned at processing station  235  or  235   a , preferably in the same chamber wherein step  522  is performed on the substrate. Alternately, the ruthenium oxide layer may be exposed to a vapor deposition process to remove oxygen and form a ruthenium metal layer on the bottom surface of the contact, preferably in the same vapor deposition chamber that performed step  522  on the substrate. An exemplary plasma pre-treatment process and an exemplary vapor pre-treatment process that may be used in embodiments of the invention are described below in conjunction with  FIG. 14  and in previously referenced U.S. patent application Ser. No. 60/663,493 [9916L].  
      Step  524 , Electroless Deposition: This step is similar to electroless deposition step  504  described above, except that nickel or cobalt-tungsten alloys are the preferred materials for bottom-up fill of high aspect ratio contacts. A more detailed description of chemistries, processes, and methods for depositing a bottom-up contact fill may be found in previously referenced U.S. patent application Ser. No. 60/663,493 [9916L].  
      Step  525 , Post Deposition Clean: This step is similar to step  505 , described above. Optionally, for embodiments of the invention that contain a brush box chamber, a post deposition clean may be performed on the substrate in which electroless cobalt and nickel overgrowth is removed via an optimized brush box process. This final clean step eliminates the need for an additional CMP process to be performed on the substrate when electroless cobalt and/or nickel deposition is used for contact fill.  
      ii) Non-Selective Electroless Plating Process  
      The non-selective electroless deposition of a metal layer on a substrate generally includes the formation of a catalytic layer on a substrate and electroless deposition of the metal layer onto the catalytic layer. A non-selective electroless deposition process sequence  510  is illustrated in  FIG. 5B  and described below.  
      Step  511 , Reducing Layer Formation: In some embodiments, a reducing layer may be formed on the substrate prior to non-selective electroless deposition. The reducing layer is formed on a substrate by modifying the surface of the substrate by a plasma deposition process. Reducing layer formation may take place in an ALD or CVD chamber prior to wet processing of the substrate. One method and apparatus that may be used to form a reducing layer is described below in conjunction with  FIGS. 1F-1K  and  14  and in the commonly assigned U.S. patent application Ser. No. 60/648,004 [9906L], entitled “Deposition of an Intermediate Catalytic Layer on a Barrier Layer for Copper Metallization,” by Timothy W. Weidman, filed Jan. 27, 2005, which is incorporated by reference herein in its entirety to the extent not inconsistent with the claimed aspects and description herein.  
      Step  512 , Catalytic Layer Formation: The catalytic layer may be formed by different methods. In one embodiment, the catalytic layer is formed from the reducing layer of step  511  either in an ALD or CVD chamber. An exemplary plasma-enhanced ALD chamber and process is described below in conjunction with  FIGS. 1H and 14 . In another embodiment, the catalytic layer is formed from the reducing layer of step  511  by a liquid deposition process. In this case, the catalytic layer may be formed on the substrate in an electroless plating cell, for example one processing station of an electroless plating twin cell, such as processing station  210 . In another embodiment, the catalytic layer may be formed directly on a substrate via a liquid deposition process in a processing station of an electroless plating twin cell, for example processing station  210 . The metal ion source for this process may be nickel, cobalt, palladium, ruthenium, rhenium and/or copper. The metal source used for this process may be a sulfate, chloride, or nitrate. The electroless deposition may then be completed in the second processing station of the twin cell, for example processing station  212 . In another embodiment, described below in conjunction with  FIG. 14A , a ruthenium-containing catalytic layer may be formed directly onto the substrate without a reducing layer being present.  
      Step  513 , Electroless Deposition: This step is similar to electroless deposition step  504  described above. A conductive layer may be deposited by application of an electroless deposition solution to the substrate structure. The deposition takes place on the catalytic seed layer. This step may be conducted in one or both of the exemplary processing stations  210  or  212  located in processing enclosure  302 . A description of chemistries, processes, and methods for depositing an electroless layer may be found in previously referenced U.S. patent application Ser. No. 10/970,839, entitled, “Electroless Cobalt Alloy Deposition Process” and in U.S. patent application Ser. No. 10/967,644, entitled, “Selective Self-Initiating Electroless Capping of Copper With Cobalt-Containing Alloys.” 
      Step  506 , Bevel Clean: This is identical to step  506  described above and shown in  FIG. 5A . In addition, vapor drying of the substrate may also be performed as part of the process sequence after the substrate bevel clean step. A suitable vapor-drying process and apparatus are described below in conjunction with  FIG. 9 .  
      iii) Electroless Plating Chamber  
       FIG. 7  is a perspective view of an exemplary electroless plating twin cell with processing enclosure  302  removed for clarity. In operation, embodiments of the deposition station  700  may be used to perform a dielectric clean process, a metal clean process, an electroless activation process, a catalytic layer deposition process, an electroless plating process, a post clean process, a post-deposition bevel clean process and/or other processing steps that may be used in an electroless process. The deposition station  700  generally represents an embodiment of the processing cells illustrated in  FIGS. 2 and 6 . Electroless processing stations  702  and  704  correspond to electroless processing stations  210  and  212 , respectively. The processing stations  702  and  704  illustrated in deposition station  700  may be an electroless activation station and an electroless deposition station, respectively. Alternatively, each processing station  702  and  704  may each be configured to perform all steps of the electroless deposition process. Internal substrate transfer shuttle  605  is positioned between processing stations  702  and  704  and is configured to transfer substrates between the respective processing stations  702  and  704 . Each of processing stations  702  and  704  includes a rotatable substrate support assembly  714  that is configured to support a substrate  701  for processing in the respective station in a face up orientation, i.e., the processing surface of the substrate  701  is facing away from the support assembly  714 . In other embodiments, the process chamber may be utilized in a face down configuration without varying from the basic scope of the invention. In  FIG. 7 , processing station  702  does not have a substrate  701  illustrated on the substrate support assembly  714 , while processing station  704  has a substrate  701  supported on the support assembly  714  to show the respective stations in both a loaded and empty states. Generally, the hardware configuration of the respective processing stations  702  and  704  will be the same, however, embodiments of the invention are not limited to configurations where the processing stations  702  and  704  have identical hardware therein. For example, the inventors contemplate that the deposition station, ie., processing station  704  may incorporate the functionality of an IBC chamber, which is further described herein, while the activation station, i.e., processing station  702  may be configured with no post-plating bevel clean capability.  
      Processing stations  702  and  704  are typically configured with a substrate support assembly  714 , which comprises substrate support fingers  712  and lift assembly  713  (shown in  FIG. 8 ), for transferring and precisely centering substrates in the processing station. Processing stations  702  and  704  each include a fluid dispensing arm  706  and  708 , respectively, that is configured to pivot over the substrate  701  during processing to dispense a processing fluid onto the front side or production surface of the substrate  701 . The fluid dispensing arms  706  and  708  may also be configured to be positioned precisely with respect to the substrate vertically. The vertical and/or angular position of the fluid dispensing portion of the arms  706  and  708  may be adjusted during processing of a substrate if desired. The dispensing arms  706  and  708  may include more than one fluid conduit therein, and as such, the dispensing arms  706  and  708  may be configured to dispense multiple fluid solutions therefrom onto the substrate  701 . In one embodiment, one or both dispensing arms  706  and  708  include a fluid conduit and fluid application nozzle configured to perform an in situ bevel clean process and/or final rinse on substrates subsequent to electroless deposition.  
       FIG. 8  is a sectional view of an exemplary pair of processing stations  702  and  704 . The sectional view of  FIG. 8  also illustrates the processing enclosure  302  that defines the processing volumes  612 ,  613  that are divided by the central interior wall  608 , as described above with respect to  FIG. 6 . Because substrate temperature is critical to the electroless process, each of the processing stations  702  and  704  includes a substrate processing platen assembly  703  that forms a substantially horizontal upper surface configured to be positioned immediately below a substrate during processing ( FIG. 8 ). The upper surface of platen assembly  703  consists of a diffusion member  703 A that evenly distributes fluids dispensed to the backside of a substrate.  
      In a typical electroless deposition process, a substrate  701  (shown in  FIG. 7 ) is transferred into processing station  704  and is secured by fingers  712 . Fingers  712  vertically position the substrate  701  just above platen assembly  703 . Because of the sensitivity to temperature of this process, the substrate, as well as fluids applied to the substrate surface, may be temperature-controlled. The substrate temperature may be controlled by filling the space between the fluid diffusion member and the substrate  701  with a temperature-controlled fluid dispensed by conduit  709  to platen assembly  703 . The fluid contacts the backside of the substrate  701  and transfers heat thereto to heat the substrate during the electroless plating process and maintain the substrate at a constant temperature, preferably between about 70° C. and about 85° C. Fingers  712  then rotate substrate  701  at a suitable rpm for evenly distributing process fluids dispensed thereon, i.e., 30-100 rpm, and fluid dispensing arm  708  pivots over substrate  701  and dispenses approximately 150 ml of an electroless deposition solution onto the front side, or production surface, of the substrate  701  for between about 5 seconds and 20 seconds. After the application of the electroless plating solution to the surface of the substrate, the rotation of the substrate is then slowed to less than about 10 rpm for a period of time between about 30 seconds and about 70 seconds while plating onto the substrate takes place. Plating time of the electroless deposition solution onto the substrate is strongly dependent on substrate and electroless deposition solution temperature as well as concentration and composition of the electroless deposition solution. The electroless deposition solution may be at a temperature between about 80° C. and about 95° C. and contain a conditioning solution, a cobalt-containing solution, and a buffered reducing solution mixed in a volumetric ratio in Dl water of 2:1:1:6, respectively. In the case of a capping layer, the typical deposition rate is between about 100 Å/min and about 200 Å/min. The substrate is then rinsed and dried by an SRD process such as the SRD process described above in conjunction with  FIG. 4 .  
      A more detailed description of an exemplary electroless twin cell that may be used in embodiments of the invention may be found in commonly assigned U.S. patent application Ser. No. 10/996,342, entitled “Method And Apparatus For Electroless Deposition of Metals Onto Semiconductor Substrates,” filed on Nov. 22, 2004, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      e) Chamber for Barrier, Reducing and Catalytic Layer Deposition  
      i) General Description of Chamber  
      To reduce electromigration and improve adhesion of subsequent metal layers, embodiments of the invention include treatment of substrates prior to wet processing in wet processing platform  213 , such as the deposition of a barrier layer, a reducing layer and/or a catalytic layer. In one embodiment, all of these substrate pre-treatments may be performed in a single ALD, CVD or vapor deposition chamber, preferred examples of which are described below. In other embodiments, barrier layer and/or reducing layers may be formed on a substrate via an ALD, CVD or vapor deposition process while the catalytic layer may be formed in a fluid processing chamber as described above.  
      In one embodiment, a standard capacitively-coupled or inductively-coupled plasma deposition chamber may be used for barrier layer, reducing layer and catalytic layer deposition on substrates. Such a chamber typically includes a sub-atmospheric process region located above a temperature-controlled substrate support and beneath a conductive showerhead, which acts as a plasma-controlling device. A process gas supply provides process gas to the process region through the showerhead. In other embodiments, a remote plasma source may be used. In another embodiment, a deposition chamber contains a ruthenium tetroxide generating apparatus (described below in conjunction with  FIG. 14A ) that is adapted to deposit a ruthenium-containing layer on a substrate surface without the use of carbon-containing precursors.  
      ii) Barrier, Reducing and Catalytic Layer Deposition Process  
      Referring to  FIGS. 1F-1K , pre-treatment of a substrate  120  may generally include depositing a barrier layer  124  on a substrate surface, exposing the barrier layer  124  to a soak process to form a reducing layer  126 , depositing a catalytic layer  128  on barrier layer  124  by exposing reducing layer  126  to a catalytic metal-containing precursor and depositing conductive layers such as seed layer  129  and/or bulk layer  130  on catalytic layer  128 . In one embodiment, barrier layer  124  (e.g., TaN) is deposited by an ALD or CVD process. Barrier layer  124  is exposed to a reductant during a soak process that may include phosphine, diborane or silane. A reducing layer is then formed on the barrier layer. Reducing layer  126  is exposed to a catalytic metal-containing precursor to deposit catalytic layer  128  on barrier layer  124 . In one example, the catalytic metal-containing precursor is introduced to the substrate by a liquid deposition process, performed in an electroless plating twin cell, described above. In another example, the catalytic metal-containing precursor is introduced to the substrate by a vapor phase deposition process, preferably in the same chamber in which barrier layer  124  and reducing layer  126  were deposited on substrate  120 . This embodiment has the added advantage of minimizing exposure of barrier layer  124  to oxygen or moisture, which improves adhesion of subsequent metal layers. In another embodiment, a catalytic layer  128  containing ruthenium may be deposited directly onto barrier layer  124  or dielectric layer  121  with no reducing layer  126  present. This embodiment requires no carbon-containing precursors for formation of catalytic layer  128 , improving adhesion of subsequent conductive layers. Catalytic layer  128  contains a catalytic metal that may include ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, alloys thereof or combinations thereof. Thereafter, a conductive layer, such as seed layer  129  and/or bulk layer  130  is deposited on catalytic layer  128 . For example, seed layer  129  may be a copper or ruthenium seed layer or a secondary barrier layer, such as a cobalt tungsten phosphide layer. Bulk layer  130  may be a copper-containing conductive layer deposited by electroless deposition or electrochemical deposition. This process sequence is described below and illustrated in  FIGS. 1F-1K  with cross-sectional views of a substrate structure at different stages of the sequence. Alternately, reducing, catalytic and conductive layers may be deposited as described above on substrate structures without a barrier layer.  
      Barrier layer  124  may be formed on the dielectric layer  121  and in aperture  122 , as depicted in  FIG. 1G . Barrier layer  124  may include one or more barrier materials such as, tantalum, tantalum nitride, tantalum silicon nitride, titanium, titanium nitride, titanium silicon nitride, tungsten nitride, silicon nitride, ruthenium nitride, derivatives thereof, alloys thereof and combinations thereof. Barrier layer  124  may be formed using a suitable deposition process including ALD, CVD, PVD or combinations thereof. For example, tantalum and/or tantalum nitride is deposited as barrier layer  124  by an ALD process as described in commonly assigned U.S. patent application Ser. No. 10/281,079, filed Oct. 25, 2002, and is herein incorporated by reference. In one example, a Ta/TaN bilayer may be deposited as barrier layer  124 , wherein the tantalum layer and the tantalum nitride layer are independently deposited by ALD, CVD and/or PVD processes. The above ALD process may be performed in a dry side pre-treatment chamber of cluster tool  200 , such as an ALD chamber located at processing station  235 .  
      Embodiments of ALD have been described above as the deposition of a binary compound of tantalum nitride utilizing pulses of two reactants, wherein a “pulse” is a quantity of a particular compound that is intermittently or non-continuously introduced into a reaction zone of a processing chamber. In the deposition of other elements or compounds, pulses of two or more reactants may also be used. For example, an ALD process for the tertiary compound tantalum silicon nitride utilizes pulses of tantalum, silicon and nitrogen precursors.  
      A typical process of depositing a TaN barrier layer by an ALD process includes providing pulses of a tantalum-containing compounds, such as PDMAT (Ta[NMe 2 ] 5 ) with a flow rate in a range from about 20 sccm to about 1,000 sccm and with a pulse time of about 2 seconds or less. Pulses of ammonia may be provided with a flow rate in a range from about 20 sccm and about 1,000 sccm and with a pulse time of about 1 second or less. An argon purge gas may have a flow rate in a range from about 100 sccm to about 1,000 sccm and may be continuously provided or pulsed into the process chamber. The time between pulses of the tantalum-containing compound and the nitrogen-containing compound may be about 5 seconds or less, preferably in a range from about 0.5 seconds to about 2 seconds. The substrate is preferably maintained with a temperature in a range from about 50° C. to about 350° C. at a chamber pressure in a range from about 1.0 Torr to about 50.0 Torr. A more detailed description of ALD formation of a barrier layer on a substrate and precursors useful for this process are disclosed in commonly assigned U.S. patent application Ser. No. 60/648,004 [9906L]entitled “Deposition of an Intermediate Catalytic Layer on a Barrier Layer For Copper Metallization,” filed on Jan. 27, 2005, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the present invention.  
      To form a reducing layer  126  on barrier layer  124 , as depicted in  FIG. 1H , barrier layer  124  is exposed to a volatile reducing precursor (VRP), preferably diborane, phosphine, silane, hydrazine, hydrogen, or combinations thereof. This is referred to as a soak process. The soak process for forming reducing layer  126  may be performed by exposing barrier layer  124  to the VRP directly or diluted in a carrier gas, for example in a vapor deposition chamber. The soak process may be conducted in the same deposition chamber as the barrier layer deposition process, described above. Alternately, reducing layer  126  is formed on barrier layer  124  by a plasma soak process. The plasma soak process includes exposing barrier layer  124  to a reducing plasma (i.e., a reductant or derivative thereof in the plasma state of matter) to form reducing layer  126 . Preferably, the reductant is silane, diborane, phosphine or combinations thereof. In this case a chamber capable of plasma vapor deposition is necessary, for example the substrate may be placed into a plasma enhanced ALD (PE-ALD) a plasma enhanced CVD (PE-CVD) or HDP-CVD chamber. An exemplary plasma vapor deposition chamber is described below.  
      In a typical process of forming a reducing layer  126  on a barrier layer  124 , barrier layer  124  is exposed to a plasma-soak process for a pre-determined time. The soak process may occur for about 5 minutes or less. During the soak process, the substrate is maintained at a temperature in a range from about 20° C. to about 350° C. and the process chamber is maintained at a pressure in a range from about 0.1 Torr to about 750 Torr. The VRP may be diluted in a carrier gas, such as helium, argon or nitrogen. The carrier gas may be provided at a flow rate in a range between about 100 sccm and about 5,000 sccm. The VRP may be provided at a flow rate in a range from about 5 sccm to about 500 sccm. The plasma may be formed using RF power delivered to the plasma generating devices utilized in the plasma chamber, e.g., a showerhead in a capacitively coupled chamber, where the RF power ranges from 100 W to 10,000 W at an RF frequency between about 0.4 kHz and about 10 GHz. A more detailed description of forming a reducing layer on a substrate and precursors useful for this process are disclosed previously referenced U.S. patent application Ser. No. 60/648,004 [9906L], entitled “Deposition of an Intermediate Catalytic Layer on a Barrier Layer For Copper Metallization.” 
      A catalytic layer  128  is deposited on barrier layer  124  as depicted in  FIG. 1l . Catalytic layer  128  is formed by exposing reducing layer  126  to a catalytic metal-containing precursor. Reducing layer  126  chemically reduces the catalytic metal-containing precursor to form catalytic layer  128  on barrier layer  124  containing the respective metal from the precursor. In one example, the catalytic metal-containing precursor is delivered to reducing layer  126  by a vapor deposition process, such as an ALD process or a CVD process. The process chamber may be a typical vapor deposition chamber as used during ALD, CVD or PVD processes. Preferably, the catalytic layer forming chamber is the same chamber in which the barrier and reducing layers were also deposited on the substrate. Alternatively, the catalytic metal-containing precursor is delivered to reducing layer  126  by a liquid deposition process, such as an aqueous solution containing the precursor dissolved therein. In embodiments of the invention using a liquid deposition process to form catalytic layer  128 , the process is conducted in an electroless plating cell, described above.  
      Catalytic layer  128  includes at least one catalytic metal and usually contains the oxidized remnants of the reducing layer  126 . The catalytic metal may include ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, osmium, alloys thereof or combinations thereof. Generally, the chemical reaction between reducing layer  126  and the catalytic metal-containing precursor forms the metallic form of the catalytic metal (e.g., Ru 0  or Co 0 ) and/or the respective boride, phosphide, silicide, nitride and combinations thereof. The catalytic layer adheres to the barrier layer as well as to the subsequently deposited conductive layer, such as a seed layer  129  or a bulk layer  130 , illustrated in  FIGS. 1J and 1K , respectively.  
      A typical process of forming a catalytic layer  128  on barrier layer  124  involves exposing reducing layer  126  to a vaporized catalytic metal-containing precursor. The vapor deposition process is conducted at a temperature high enough to vaporize the catalytic metal-containing precursor and drive the reduction reaction to completion. The temperature range varies according to the particular catalytic metal-containing precursor used during the deposition. Generally, the substrate is maintained in a range from about 25° C. to about 350° C., preferably from about 50° C. to about 250° C. The process chamber may be a typical vapor deposition chamber as used during ALD, CVD or PVD processes. The process chamber is maintained at a pressure relative to the temperature, precursor and particular process. Generally, the pressure is maintained in a range from about 0.1 Torr to about 750 Torr. The catalytic metal-containing precursor is exposed to reducing layer  126  from about 1 second to about 120 seconds. The catalytic metal-containing precursor may be delivered purely or diluted in a carrier gas that includes nitrogen, hydrogen, argon, helium or combinations thereof. In one example, a reducing plasma is exposed to the substrate for 10 seconds at a flow rate of about 500 sccm, consisting of 450 sccm helium carrier gas and 50 sccm silane.  
      Seed layer  129  is deposited as the conductive layer on catalytic layer  128  and may be deposited using conventional deposition techniques, such as ALD, CVD, PVD, electroless, or electroplating. Preferably, seed layer  129  is deposited immediately after deposition of catalytic layer  128 , minimizing oxidation of catalytic layer  128  and improving overall adhesion of subsequently deposited conductive layers. Hence, in the preferred embodiment of the invention, seed layer  129  is deposited on a substrate in the same cluster tool in which catalytic layer  128  is deposited on the substrate, ideally in the same processing chamber. In one aspect, wherein the catalytic metal-containing precursor is delivered to reducing layer  126  by a liquid deposition process, seed layer  129  is a copper seed layer deposited on a substrate by an electroless deposition process in the same electroless plating twin cell that deposited catalytic layer  128  on the substrate. Seed layer  129  may have a thickness range from about a single molecular layer to about 100 Å. Generally, seed layer  129  contains copper, ruthenium, cobalt, tantalum or other metal or alloy known to exhibit good adhesion to a subsequent bulk layer  130 . A typical method and apparatus for depositing a seed layer  129  via an electroless deposition process is described above in conjunction with  FIGS. 7 and 8 .  
      Ruthenium oxides may be used for the formation of catalytic and/or bulk conductive layers, ruthenium tetroxide (RuO 4 ) being the preferred ruthenium compound used for this process. Ruthenium tetroxide may be prepared with an in situ generation process, described below in conjunction with  FIG. 14A , by exposing a metallic ruthenium source to an oxidizing gas, such as ozone. The in situ generated ruthenium tetroxide is immediately introduced into the process chamber. Ruthenium tetroxide is a strong oxidant and therefore readily reacts with the reducing layer to form a ruthenium-containing catalytic layer on the barrier layer or dielectric layer.  
      iii) Ruthenium Layer Deposition Process  
      A ruthenium-containing layer may be selectively or non-selectively deposited on device features formed on the surface of a substrate by use of a ruthenium tetroxide-containing gas. It is believed that the selective or non-selective deposition of a ruthenium-containing layer on the surface of the substrate is strongly dependent on the temperature and type of surfaces that are exposed to the ruthenium tetroxide containing gas. It is also believed that by controlling the temperature of a substrate at a desired temperature below, for example about 180 ° C., a ruthenium layer will selectively deposit on certain types of surfaces. At higher temperatures, for example greater than 180° C., the ruthenium deposition process from a ruthenium tetroxide containing gas becomes much less selective and thus will allow a blanket film to deposit on all types of surfaces. In one aspect, the deposition of a ruthenium containing layer is used to promote the adhesion and filling of subsequent layers on the surface of the substrate. In another aspect, the properties of the ruthenium containing layer deposited on the surface of the substrate is specially tailored to fit the needs of the devices formed on the surface of the substrate. Typical desirable properties include the formation of crystalline or amorphous metallic ruthenium layers on the surface of the substrate so that the formed layer(s) can act as a barrier layer, a catalytic layer for subsequent electroless or electroplating processes, or even fill a desired device feature. Another desirable property of a ruthenium-containing layer is the formation of a ruthenium dioxide layer (RuO 2 ) on the surface of the substrate to, for example, promote selective bottom up growth of an electroless and/or electroplated layer, or form an electrode that is compatible ferroelectric oxides (e.g., BST, etc.), piezoelectric materials (e.g., PZT, etc.) used to form various Micro-Electro-Mechanical Systems (MEMS) devices.  
      In general, a ruthenium-containing catalytic layer with desirable properties is formed on a barrier layer or a dielectric layer by generating a ruthenium tetroxide containing gas and exposing a temperature controlled surface of a substrate to the gas. This involves forming a ruthenium tetroxide gas, collecting the gas in a source vessel, purging the source vessel of excess oxygen, heating the source vessel and delivering the ruthenium tetroxide-containing gas to the process chamber to form the catalytic layer. As noted above, in various aspects of the invention it may be desirable to selectively or non-selectively form a metallic ruthenium layer or a ruthenium dioxide layer on the surface of the substrate to form a ruthenium containing layer. An exemplary apparatus and method of forming a ruthenium tetroxide containing gas to form a ruthenium containing layer on a surface of a substrate is described herein.  
      In an exemplary vapor deposition process, the deposition gas, containing ruthenium tetroxide, is delivered to the surface of the substrate having a reducing layer containing P—H functional groups formed thereon. The reducing layer containing P—H functional groups may be formed by use of a phosphine soak process or phosphine plasma soak process. During the process the substrate is maintained at a temperature of about 200° C. After exposing the reducing layer to the ruthenium tetroxide containing gas for about 60 seconds, a ruthenium phosphide layer is formed on the barrier layer. Alternately, a ruthenium-containing catalytic layer may be formed directly onto a barrier layer or dielectric layer with no reducing layer.  
      iv) Exemplary Barrier, Reducing and Catalytic Layer Deposition Chamber  
      The barrier, reducing and catalytic layer deposition described above may be performed in a plasma processing chamber.  FIG. 14  illustrates an exemplary capacitively coupled plasma chamber, chamber  1450 . A sidewall  1405 , a ceiling  1406  and a base  1407  enclose chamber  1450  and form a process area  1421 . A temperature-controlled substrate pedestal  1415 , which supports a substrate  1422 , mounts to the base  1407  of chamber  1450 . A vacuum pump  1435  controls the pressure within chamber  1450 , typically holding the pressure below 5 milliTorr (mT). A gas distribution showerhead  1410  consists of a gas distribution plenum  1420  connected to the gas supply  1425  and communicating with the processing region  1427  over the substrate  1422  through plural gas nozzle openings  1430 . The gas distribution showerhead  1410 , made from a conductive material (e.g., anodized aluminum, etc.), acts as a plasma controlling device by use of the attached impedance match element  1475  and RF power source  1490 . A bias RF generator  1462  applies RF bias power to the temperature-controlled substrate pedestal  1415  and substrate  1422  through an impedance match element  1464 . With the appropriate gases provided by gas supply  1425 , the barrier layer, reducing layer and/or catalytic layer deposition described above may all be performed in chamber  1450 .  
      v) Exemplary Ruthenium Layer Deposition Chamber  
      In general, the method and apparatus described herein is adapted to selectively or non-selectively deposit a ruthenium containing layer on device features formed on the surface of a substrate by use of a ruthenium tetroxide containing gas. In a preferred embodiment of the invention, a deposition chamber  600 , illustrated in  FIG. 14A , is used to generate and deposit a ruthenium-containing catalytic layer on a substrate. Deposition chamber  600  is similar to chamber  1450  described above and identical reference numerals have been used to designate elements common to each chamber. In one embodiment, the ruthenium containing layer is formed on a surface of a substrate by creating ruthenium tetroxide in an external vessel and then delivering the generated ruthenium tetroxide gas to a surface of a temperature controlled substrate positioned in a processing chamber.  
      The deposition chamber  600  generally contains a process gas delivery system  601  and a sealed processing chamber  603 A. The sealed processing chamber  603 A generally contains all of the components described above in conjunction with  FIG. 14  and also a temperature controlled substrate support  623 , a remote plasma source  670  and the process gas delivery system  601  connected to the inlet line  1426 . The temperature controlled substrate support  623  generally contains a conductive block  624 , a heat exchanging device  620  and a temperature controller  621 . The conductive block has a substrate supporting surface  624 A and is attached and sealed to the base  1407  to form a sealed processing chamber  603 A.  
      In one embodiment of the deposition chamber  600 , a process gas delivery system  601  is adapted to deliver a fluid to the processing region  1427  so that a catalytic or adhesion layer can be formed on the substrate surface. The process gas delivery system  601  generally contains one or more gas sources  611 A-E, an ozone generating device  612 B, a processing vessel  630 , a source vessel assembly  640 , and an outlet line  660  attached to the inlet line  1426  of the sealed processing chamber  603 A. The one or more gas sources  611 A-E are generally sources of various carrier and/or purge gases that may be used during processing in the sealed processing chamber  603 A. The one or more gases delivered from the gas sources  611 A-E may include, for example, nitrogen, argon, helium, hydrogen, or other similar gases.  
      In one embodiment of the process gas delivery system  601 , the processing vessel  630  contains a vessel  631 , a temperature controlling device  634 A, an input port  635  and an output port  636 . The vessel  631  is generally an enclosed region made of or coated with glass, ceramic or other inert material that will not react with the processing gas formed in the vessel  631 . The vessel  631  contains a volume of a ruthenium metal (item “A”), preferably in a porous-solid or pellet form, to promote the formation of ruthenium tetroxide when the ozone gas is delivered to the vessel  631 . The temperature controlling device  634 A generally contains a temperature controller  634 B and a heat exchanging device  634 C, which are adapted to control the temperature of the vessel  631  at a desired processing temperature during the ruthenium tetroxide generation process. Typically, the ruthenium metal “A” contained in vessel  631  is maintained at a temperature between about 20° C. and 60° C. to enhance ruthenium tetroxide formation in vessel  631 . In one aspect, the heat exchanging device  634 C is a temperature controlled fluid heat exchanging device, a resistive heating device and/or a thermoelectric device that is adapted to heat and/or cool the vessel  631  during different phases of the process.  
      In one embodiment, a remote plasma source  672  is connected to the processing vessel  630  via the RPS inlet line  673  so that in different phases of the ruthenium tetroxide formation process the ruthenium metal can be regenerated by injecting H radicals into the vessel  631  to reduce any formed oxides on the surface of the ruthenium metal. Regeneration is necessary when an undesirable layer of ruthenium dioxide (Ru 0   2 ) is formed on a significant portion of the exposed ruthenium metal contained in the vessel  631 .  
      Referring to  FIG. 14A , the source vessel assembly  640  generally contains a source vessel  641 , a temperature controller  642 , an inlet port  645  and an outlet port  646 . The source vessel  641  is adapted to collect and retain the ruthenium tetroxide generated in the processing vessel  630 . The source vessel  641  is generally lined, coated or made from a glass, ceramic, plastic (e.g., Teflon, polyethylene, etc.), or other material that will not react with the ruthenium tetroxide and has desirable thermal shock and mechanical properties. When in use the temperature controller  642  cools the source vessel  641  to a temperature less than 20° C. to condense the ruthenium tetroxide gas on to the walls of the source vessel. The temperature controller  642  generally contains a temperature controller device  643  and a heat exchanging device  644 , which are adapted to control the temperature of the source vessel  641  at a desired processing temperature.  
      In operation, deposition chamber  600  forms a ruthenium-containing layer on a substrate. Initially, ruthenium tetroxide gas is formed and collected in the source vessel  641 . Ozone generated in ozone generating device  612 B is then delivered to the ruthenium metal contained in vessel  631  to form a flow of ruthenium tetroxide gas, which is collected in the source vessel  641 . Therefore, an ozone containing gas, typically containing between about 10 wt. % and 20 wt. % of ozone, flows across the ruthenium metal which causes ruthenium tetroxide to be formed and swept away by the flowing gas. During this process the gas flow path is from the ozone generating device  612 B, in the input port  635 , across the ruthenium metal (item “A”), through the output port  636  in the vessel  631  through the process line  637  and into the source vessel  641 . Cooling the ruthenium tetroxide and causing it to condense or solidify on the walls of the source vessel  641 , the unwanted oxygen-and ozone-containing components in the ruthenium tetroxide-containing gas can be separated and removed.  
      Oxygen- and ozone-containing components in the ruthenium tetroxide-containing gas are separated and removed while the walls of the source vessel are maintained at a temperature of 20° C. or below. This is performed by closing the ozone isolation valve  612 A and flowing one or more purge gasses from the one or more of the gas sources  611  B-C through the processing vessel  630 , into the process line  637 , through the source vessel  641  and then through the exhaust line  651  to the exhaust system  650 . Removal of these unwanted oxygen and unreacted ozone components is especially important where copper interconnects are exposed on the surface of the substrate, since copper has a high affinity for oxygen and is corroded easily in the presence of an oxidizing species.  
      In one embodiment, ruthenium tetroxide is delivered to sealed processing chamber  603 A after the source vessel  641  has been purged and valve  637 A is closed to isolate the source vessel  641  from the processing vessel  630 . Prior to delivery of ruthenium tetroxide to sealed processing chamber  603 A, the source vessel  641  is heated to a temperature to cause the condensed or solidified ruthenium tetroxide to form ruthenium tetroxide gas at which time the one or more of the gas sources  611  (e.g., items  611  D-E), the isolation valve  638 , the isolation valve  639  and process chamber isolation valve  661  are opened, causing a ruthenium tetroxide containing gas to flow into the inlet line  1426 , through the gas distribution showerhead  1410 , into a processing region  1427  and across the substrate  1422  so that a ruthenium-containing layer can be formed on a substrate surface. Alternately, a ruthenium tetroxide-containing gas is formed when a nitrogen containing gas is delivered from the gas source  611 D and a hydrogen-containing gas is delivered from the gas source  611 E through the source vessel and to the sealed processing chamber  603 A. In another embodiment, the remote plasma source  670  is utilized to enhance the process of forming a metallic ruthenium layer via the injection of H radicals, generated by the remote plasma source, into the processing region  1427  to reduce any formed oxides on the surface of the ruthenium metal. In another embodiment, process gas delivery system  601  includes multiple source vessel assemblies  640 , which alternately collect and dispense the generated ruthenium tetroxide. This avoids interruption of substrate processing in chamber  1450  when one source vessel must collect ruthenium tetroxide.  
      In a typical process for depositing a ruthenium-containing layer, a plasma is generated during the deposition process to improve the deposited ruthenium-containing layer&#39;s properties. A typical process using a remote plasma source (RPS) may include using 1000 sccm of H 2 , 1000 sccm of argon, an RF power of 350 W and a frequency of about 13.56 MHz.  
      A more detailed description of a ruthenium tetroxide deposition apparatus and method that may be used in embodiments of the invention may be found in commonly assigned U.S. patent application Ser. No. 60/648,004 [9906L], entitled “Deposition of an Intermediate Catalytic Layer on a Barrier Layer For Copper Metallization,” filed Jan. 27, 2005.  
      vi) Combined Vapor/Liquid Deposition Chambers  
      In another embodiment, the reducing and catalytic layers described above may be deposited on a substrate in a fluid deposition chamber  1800 , described below and shown in  FIGS. 18A and 18B . Because both vapor and liquid deposition may take place in fluid deposition chamber  1800 , the reducing and catalytic layers may be deposited via vapor deposition processes and subsequent conductive layers may be deposited via electroless and/or electrochemical deposition. Hence, formation of a reducing layer, a catalytic layer and a seed layer may all be performed in a single chamber.  
       FIGS. 18A and 18B  illustrate a schematic cross-sectional view of fluid deposition chamber  1800 , which is one embodiment of a combined vapor/liquid deposition chamber that may be useful to deposit conductive layers using vapor deposition and electroless or electroplating processes as described previously. The fluid deposition chamber  1800  processes substrates in a processing region  155  that is formed by the temperature-controlled substrate support  1812 , the substrate “W”, a seal  154  and the lower wall  148  of moveable processing shield  150 .  
      In one embodiment, a process gas source  161  containing a gas reservoir  160  and valve  159  and/or a liquid source  127  containing liquid reservoirs  128   a - 128   f  and valve  129   b  are adapted to deliver one or more processing fluids to the injection port  144 , into the processing region  155 , across the substrate surface, through the holes  152  and into the evacuation region  153  where the process gas is directed to the waste collection system  151 . In one example, a plating solution may be collected and recirculated across the surface of the substrate by use of a collection tank system  1849 , which is adapted to recirculate collected plating solution. The fluid deposition chamber  1800  further includes a drain  1827  in order to collect and expel fluids used in the fluid deposition chamber  1800 . The bottom  1807  of the processing compartment  1806  may comprise a sloped surface to aid the flow of fluids used in the fluid deposition chamber  1800  towards an annular channel in communication with the drain  1827  and to protect the substrate support assembly  1813  from contact with fluids.  
      In one embodiment, forming a reducing layer and a catalytic layer are performed sequentially in fluid deposition chamber  1800 , described herein. A substrate is transferred into fluid deposition chamber  1800  and placed on the substrate receiving surface  1814  by use of a robot (not shown) and the lift pins  1818 . Next the moveable processing shield  150  is then moved into position where it contacts the substrate receiving surface  1814 , or the substrate surface, to form the processing region  155 . The pressure in the evacuation region  153 , and processing region  155 , is then lowered by use of the pump (not shown) in waste collection system  151 . A processing fluid is then delivered to the processing region  155  from a process gas source  161  that is connected to the injection port  144 . In one example, the processing gas contains ruthenium tetroxide to form a ruthenium-containing layer on the surface of the substrate. This corresponds to reducing layer  126  in  FIG. 1H .  
      After forming reducing layer  126 , the processing region  155  may then be purged with a carrier gas (e.g., argon, nitrogen, etc.) to remove any of the remnants of the processing gas. Next an electroless or electroplating solution may be delivered to the processing region  155  from the liquid source  127  so that a catalytic layer  128  can be formed from reducing layer  126  on the substrate surface.  
      Referring to  FIGS. 18C and 18D , in one embodiment of the fluid deposition chamber  1800 , one or more electrical contacts (not shown) are embedded in the seal  154  of the moveable processing shield  150  and an anode  163  is placed in contact with the processing fluid (see item “A”) so that a plating current can be delivered to the reducing layer so that the catalytic layer can be deposited using an electroplating process. The metal ions in the processing fluid will be plated on the reducing layer by applying a negative bias to the reducing layer surface relative to the anode  163  by use of a power supply (not shown). Further, a bulk conductive layer, corresponding to metal bulk layer  130  in  FIG. 1K , may subsequently be deposited.  
      A more detailed description of a combined liquid/vapor deposition chamber may be found in the commonly assigned U.S. patent application Ser. No. 10/059,572, entitled “Electroless Deposition Apparatus” by Stevens et al., filed Jan. 28, 2002, and previously referenced U.S. patent application Ser. No. 60/648,004 [9906L], entitled “Deposition of an Intermediate Catalytic Layer on a Barrier Layer For Copper Metallization,” which are incorporated by reference herein in their entirety to the extent not inconsistent with the claimed aspects and description herein.  
      f) Plasma-Assisted Dry Etch Chamber for Contact Clean  
      i) General Description of Chamber  
      To remove native oxide and other contaminants formed on exposed contact surfaces prior to the electroless deposition process and to improve adhesion of subsequent metal layers, embodiments of the invention include a treatment of substrates prior to wet processing in wet processing platform  213 , namely a plasma-assisted dry etch treatment, also known as a SiCoNi clean, as described below and in conjunction with  FIG. 19 . The substrate dry clean treatment is performed in a chamber adapted to perform a chemical etch clean and in-situ anneal on substrates and is preferably located on the dry side of cluster tool  200  (as shown in  FIG. 2 ), such as processing station  235 .  
      The dry etch chamber may perform a plasma-enhanced chemical etch process with both substrate heating and cooling all within a single processing environment, including an anneal or heat treating process.  FIG. 19  illustrates a partial cross sectional view of a processing chamber  1900 . The dry etch chamber is a vacuum chamber containing a lid assembly  200   a , a substrate support member  310   a  which is temperature-controlled, a chamber body  112   a  which is temperature-controlled, and a processing zone  140   a . The processing zone  140   a  is the region between the lid assembly  200   a  and the substrate support member  310   a . The substrate support member  310   a  is generally adapted to support and control the temperature of the substrate during processing. The lid assembly  200   a  contains a process gas supply panel (not shown) as well as a first and second electrode (elements  240   a  and  220   a ) that define a plasma cavity for generating plasma external to the processing zone  140   a . The process gas supply panel (not shown) provides reactive gas to the plasma cavity, through the second electrode  220   a  and into the processing zone  140   a . The second electrode  220   a  is positioned over the substrate and adapted to heat the substrate after the plasma-assisted dry etch process is complete.  
      ii) Plasma-Assisted Dry Etch Process  
      An exemplary dry etch process for removing native oxides on a surface of the substrate using an ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ) gas mixture performed within a dry etch processing chamber will now be described.  
      The dry etch process begins by placing a substrate, such as a semiconductor substrate, into a dry etch processing chamber. Preferably, the substrate is held to the support assembly  300   a  of the substrate support member  310   a  during processing via a vacuum or electrostatic chuck. The chamber body  112   a  is preferably maintained at a temperature of between 50° C. and 80° C., more preferably at about 65° C. This temperature of the chamber body  112   a  is maintained by passing a heat transfer medium through fluid channels  113   a  located in the chamber body. During processing, the substrate is cooled below 65° C., such as between 15° C. and 50° C., by passing a heat transfer medium or coolant through fluid channels  113 a formed within the substrate support. In another embodiment, the substrate is maintained at a temperature of between 22° C. and 40° C. Typically, the substrate support is maintained below about 22° C. to reach the desired substrate temperatures specified above.  
      The ammonia and nitrogen trifluoride gases are then introduced into the dry etching chamber to form a cleaning gas mixture. The amount of each gas introduced into the chamber is variable and may be adjusted to accommodate, for example, the thickness of the oxide layer to be removed, the geometry of the substrate being cleaned, the volume capacity of the plasma and the volume capacity of the chamber body  112   a . In one aspect, the gases are added to provide a gas mixture having at least a 1:1 molar ratio of ammonia to nitrogen trifluoride. In another aspect, the molar ratio of the gas mixture is at least about 3 to 1 (ammonia to nitrogen trifluoride). Preferably, the gases are introduced in the dry etching chamber at a molar ratio of from 5:1 (ammonia to nitrogen trifluoride) to 30:1. More preferably, the molar ratio of the gas mixture is of from about 5 to 1 (ammonia to nitrogen trifluoride) to about 10 to 1. The molar ratio of the gas mixture may also fall between about 10:1 (ammonia to nitrogen trifluoride) and about 20:1.  
      A purge gas or carrier gas may also be added to the gas mixture. Any suitable purge/carrier gas may be used, such as argon, helium, hydrogen, nitrogen, or mixtures thereof, for example. Typically, the overall gas mixture is from about 0.05% to about 20% by volume of ammonia and nitrogen trifluoride. The remainder being the carrier gas. In one embodiment, the purge or carrier gas is first introduced into the chamber body  112   a  before the reactive gases to stabilize the pressure within the chamber body.  
      The operating pressure within the chamber body can be variable. Typically, the pressure is maintained between about 500 mTorr and about 30 Torr. Preferably, the pressure is maintained between about 1 Torr and about 10 Torr. More preferably, the operating pressure within the chamber body is maintained between about 3 Torr and about 6 Torr.  
      An RF power of from about 5 and about 600 Watts is applied to the first electrode to ignite a plasma of the gas mixture within the plasma cavity. Preferably, the RF power is less than 100 Watts. More preferable is that the frequency at which the power is applied is very low, such as less than 100 kHz. Preferably, the frequency ranges from about 50 kHz to about 90 kHz.  
      The plasma energy dissociates the ammonia and nitrogen trifluoride gases into reactive species that combine to form a highly reactive ammonia fluoride (NH 4 F) compound and/or ammonium hydrogen fluoride (NH 4 F.HF) in the gas phase. These molecules then flow through the second electrode  220   a  to react with the substrate surface to be cleaned. In one embodiment, the carrier gas is first introduced into the dry etch chamber, a plasma of the carrier gas is generated, and then the reactive gases, ammonia and nitrogen trifluoride, are added to the plasma.  
      Not wishing to be bound by theory, it is believed that the etchant gas, NH 4 F and/or NH 4 F.HF, reacts with the native oxide surface to form ammonium hexafluorosilicate (NH 4 ) 2 SiF 6 , NH 3 , and H 2 O products. The NH 3 , and H 2 O are vapors at processing conditions and removed from the chamber by a vacuum pump attached to the chamber. A thin film of (NH 4 ) 2 SiF 6  is left behind on the substrate surface.  
      After performing the plasma processing step, the substrate support is elevated to an anneal position in close proximity to the heated second electrode. The heat radiated from the second electrode  220   a  should be sufficient to dissociate or sublimate the thin film of (NH 4 ) 2 SiF 6  into volatile SiF 4 , NH 3 , and HF products. These volatile products are then removed from the chamber by the vacuum pump  125   a  attached to the system. Typically, a temperature of 75° C. or more is used to effectively sublimate and remove the thin film from the substrate. Preferably, a temperature of 100° C. or more is used, such as between about 115° C. and about 200° C.  
      The thermal energy to dissociate the thin film of (NH 4 ) 2 SiF 6  into its volatile components is convected or radiated by the second electrode. A heating element  270   a  is directly coupled to the second electrode  220   a , and is activated to heat the second electrode and the components in thermal contact therewith to a temperature between about 75° C. and 250° C. In one aspect, the second electrode is heated to a temperature of between 100° C. and 150° C., such as about 120° C.  
      The distance between the upper surface of the substrate having the thin film thereon and the second electrode  220   a  is not critical and is a matter of routine experimentation. A person of ordinary skill in the art can easily determine the spacing required to efficiently and effectively vaporize the thin film without damaging the underlying substrate. It is believed, however, that a spacing of between about 0.254 mm (10 mils) and 5.08 mm (200 mils) is effective.  
      Once the film has been removed from the substrate, the chamber is purged and evacuated. The cleaned substrate is then removed from the chamber by lowering the substrate to the transfer position, de-chucking the substrate, and transferring the substrate through a slit valve opening.  
      iii) Exemplary Plasma-Assisted Dry Etch Chamber  
       FIG. 19  is a partial cross sectional view showing an illustrative processing chamber  1900 . In one embodiment, the processing chamber  1900  includes a chamber body  112   a , a lid assembly  200   a , and a support assembly  300   a . The lid assembly  200   a  is disposed at an upper end of the chamber body  112   a , and the support assembly  300   a  is at least partially disposed within the chamber body  112   a . The processing chamber  1900  and the associated hardware are preferably formed from one or more process-compatible materials, such as aluminum, anodized aluminum, nickel plated aluminum, nickel plated aluminum 6061-T6, stainless steel, as well as combinations and alloys thereof.  
      The chamber body  112   a  includes a slit valve opening  160   a  formed in a sidewall thereof to provide access to the interior of the processing chamber  1900 . The slit valve opening  160   a  is selectively opened and closed to allow access to the interior of the chamber body  112   a  by a substrate handling robot (not shown).  
      In one or more embodiments, the chamber body  112   a  includes a fluid channel  113   a  formed therein for flowing a heat transfer fluid therethrough. The heat transfer fluid can be a heating fluid or a coolant and is used to control the temperature of the chamber body  112   a  during processing and substrate transfer. The temperature of the chamber body  112 a is important to prevent unwanted condensation of the gas or byproducts on the chamber walls. Exemplary heat transfer fluids include water, ethylene glycol, or a mixture thereof. An exemplary heat transfer fluid may also include nitrogen gas.  
      The chamber body  112   a  can further include a liner  133   a  that surrounds the support assembly  300   a . The liner  133   a  is preferably removable for servicing and cleaning. The liner  133   a  can be made of a metal such as aluminum, or a ceramic material. However, the liner  133   a  can be any process compatible material. The liner  133   a  can be bead blasted to increase the adhesion of any material deposited thereon, thereby preventing flaking of material which results in contamination of the processing chamber  1900 . In one or more embodiments, the liner  133   a  includes one or more apertures  135   a  and a pumping channel  129   a  formed therein that are in fluid communication with a vacuum system. The apertures  135   a  provide a flow path for gases into the pumping channel  129   a , which provides an egress for the gases within the processing chamber  1900 .  
      The vacuum system may include a vacuum pump  125   a  and a throttle valve  127   a  to regulate flow of gases through the processing chamber  1900 . The vacuum pump  125   a  is coupled to a vacuum port  131   a  disposed on the chamber body  112   a  and therefore, in fluid communication with the pumping channel  129   a  formed within the liner  133   a . The apertures  135   a  allow the pumping channel  129   a  to be in fluid communication with a processing zone  140   a  within the chamber body  112   a . The processing zone  140   a  is defined by a lower surface of the lid assembly  200   a  and an upper surface of the support assembly  300   a , and is surrounded by the liner  133   a . The apertures  135   a  may be uniformly sized and evenly spaced about the liner  133   a.    
      In operation, one or more gases exiting the processing chamber  1900  flow through the apertures  135   a  formed through liner  133   a  into the pumping channel  129   a . The gas then flows within the pumping channel  129   a  and through the vacuum port  131   a  into the vacuum pump  125   a.    
      Referring to  FIG. 19 , the lid assembly  200   a  includes a number of components stacked on top of one another. In one or more embodiments, the lid assembly  200   a  includes a lid rim  210   a , gas delivery assembly which acts as the second electrode  220   a , and a top plate  250   a . The second electrode  220   a  is coupled to an upper surface of the lid rim  210   a  and is arranged to make minimum thermal contact therewith. The components of the lid assembly  200   a  are preferably constructed of a material having a high thermal conductivity and low thermal resistance, such as an aluminum alloy with a highly finished surface. Preferably, the thermal resistance of the components is less than about 5×10 −4  m 2  K/W.  
      The second electrode  220   a  may include a distribution plate or showerhead (not shown). Typically, the distribution plate is substantially disc-shaped and includes a plurality of apertures or passageways thereby providing an even distribution of the gas across the surface of the substrate as the flow of gas exits lid assembly  200   a . The second electrode  220   a  may further include a blocker assembly (not shown) disposed adjacent the distribution plate. The blocker assembly provides an even distribution of gas to the backside of the distribution plate.  
      A gas supply panel (not shown) is typically used to provide the one or more gases to the processing chamber  1900 . The particular gas or gases that are used depend upon the process or processes to be performed within the processing chamber  1900 . Illustrative gases can include, but are not limited to one or more precursors, reductants, catalysts, carriers, purge, cleaning, or any mixture or combination thereof. Typically, the one or more gases introduced to the processing chamber  1900  flow into the lid assembly  200   a  and then into the chamber body  112   a  through the second electrode  220   a . Depending on the process, any number of gases can be delivered to the processing chamber  1900 , and can be mixed either in the processing chamber  1900  or before the gases are delivered to the processing chamber  1900 .  
      In use, one or more process gases are introduced into the second electrode  220   a  from the gas supply panel (not shown), flow around and through the blocker assembly (not shown), then enter the processing zone  140   a  of processing chamber  1900  and meet the exposed surface of the substrate disposed on the support assembly  300   a.    
      Still referring to  FIG. 19 , the lid assembly  200   a  can further include a first electrode  240   a  to generate a plasma of reactive species within the lid assembly  200   a . In one embodiment, the first electrode  240   a  is supported on the top plate  250   a  and is electrically isolated therefrom. In one or more embodiments, the first electrode  240   a  is coupled to a power source  241   a  while the second electrode  220   a  is connected to ground (ie. the second electrode  220   a  serves as an electrode). Accordingly, a plasma of one or more process gases can be generated in the volumes between the first electrode  240   a  and the second electrode  220   a  (the gas delivery assembly in this example). The plasma is well confined or contained within the lid assembly  200   a . Accordingly, the plasma is a “remote plasma” since no active plasma is in direct contact with the substrate disposed within the chamber body  112   a . As a result, plasma damage to the substrate is avoided because the plasma is sufficiently separated from the substrate surface.  
      Any power source capable of activating the gases into reactive species and maintaining the plasma of reactive species may be used for power source  241   a . For example, radio frequency (RF), direct current (DC), or microwave (MW) based power discharge techniques may be used. Alternatively, a remote activation source may be used, such as a remote plasma generator, to generate a plasma of reactive species which are then delivered into processing chamber  1900 .  
      Second electrode  220   a  may be heated depending on the process gases and operations to be performed within the processing chamber  1900 . In one embodiment, a heating element  270   a , such as a resistive heater for example, can be coupled to the second electrode  220   a  or the distribution plate. Regulation of the temperature may be facilitated by a thermocouple coupled to the second electrode  220   a  or the distribution plate.  
      The support assembly  300   a  may be at least partially disposed within the chamber body  112   a . The support assembly  300   a  can include a substrate support member  310   a  to support a substrate (not shown in this view) for processing within the chamber body  112   a . The substrate support member  310   a  can be coupled to a lift mechanism (not shown) which extends through a bottom surface of the chamber body  112   a . The lift mechanism (not shown) can be flexibly sealed to the chamber body  112   a  by a bellows (not shown) that prevents vacuum leakage from around the lift mechanism. The lift mechanism allows the substrate support member  310   a  to be moved vertically within the chamber body  112   a  between a process position and a lower, transfer position. The transfer position is slightly below slit valve opening  160   a  formed in a sidewall of the chamber body  112   a . In one or more embodiments, the substrate support member  310   a  has a flat, circular surface or a substantially flat, circular surface for supporting a substrate to be processed thereon. The substrate support member  310   a  is preferably constructed of aluminum. The substrate support member  310   a  can be moved vertically within the chamber body  112   a  so that a distance between substrate support member  310   a  and the lid assembly  200   a  can be controlled.  
      In one or more embodiments, the substrate (not shown) may be secured to the substrate support member  310   a  using an electrostatic or vacuum chuck. In one or more embodiments, the substrate may be held in place on the substrate support member  310   a  by a mechanical clamp (not shown), such as a conventional clamp ring. Preferably, the substrate is secured using an electrostatic chuck  
      Substrate support member  310   a  may include one or more bores (not shown) formed therethrough to accommodate a lift pin (not shown). Each lift pin is typically constructed of ceramic or ceramic-containing materials, and are used for substrate-handling and transport.  
      The temperature of the support assembly  300   a  is controlled by a fluid circulated through one or more fluid channels  360   a  embedded in the body of the substrate support member  310   a . Preferably, the fluid channel  360   a  is positioned about the substrate support member  310   a  to provide a uniform heat transfer to the substrate receiving surface of the support member  310   a . The fluid channel  360   a  and can flow heat transfer fluids to either heat or cool the substrate support member  310   a . Any suitable heat transfer fluid may be used, such as water, nitrogen, ethylene glycol, or mixtures thereof. The support assembly  300   a  can further include an embedded thermocouple (not shown) for monitoring the temperature of the support surface of the substrate support member  310   a.    
      In operation, the substrate support member  310   a  can be elevated to close proximity of the lid assembly  200   a  to control the temperature of the substrate being processed. As such, the substrate can be heated via radiation emitted from the lid assembly  200   a  or the distribution plate, which are heated by heating element  270   a . Alternatively, the substrate can be lifted off the substrate support member  310   a  to close proximity of the heated lid assembly  200   a  using the lift pins.  
      A more detailed description of a plasma-assisted dry etch chamber and process that may be contained in some configurations of the invention may be found in commonly assigned U.S. patent application Ser. No. 60/547,839 entitled “In-Situ Dry Clean Chamber For Front End Of Line Fabrication,” filed on Feb. 22, 2005, which is hereby incorporated by reference in its entirety to the extent not inconsistent with the claimed invention.  
      g) Supercritical Clean Chamber  
      In some aspects of the invention, immediately prior to deposition process steps, organic and other contaminants are removed from substrate surfaces in a dry side chamber via a supercritical clean process. Various gases, such as carbon dioxide, in their supercritical fluid state have been shown to replace organic solvents in cleaning applications. For substances that exhibit supercritical fluid properties, when the substance is above its critical point, i.e., above the critical temperature and critical pressure, the phase boundary between the gas phase and liquid phase disappears, and the substance exists in a single supercritical fluid phase. In the supercritical fluid phase, a substance assumes some of the properties of a gas and some of the properties of a liquid. For example, supercritical fluids have diffusivity properties similar to gases but solvating properties similar to liquids. Therefore, supercritical fluids have good cleaning properties and may be used to clean substrate structures that have geometries difficult to clean with standard wet-clean methods, such as high aspect ratio contacts.  
      The term “supercritical fluid” as used herein refers to a substance above its critical point. The term “dense fluid” as used herein refers to a substance at or below its critical point. Dense fluid preferably comprises a substance at or near its critical point. In certain embodiments, a dense fluid comprises a substance that is at a state in which its density is at least 1/5  the density of the substance at its critical point.  
      In one aspect, a substrate may be processed by applying a supercritical fluid thereto. In another aspect, a substrate may be processed by applying a dense fluid thereto without the substance reaching a supercritical state. In still another apsect, a substrate may be processed by applying a substance thereto in which the substance is phase modulated between a supercritical fluid state and a dense fluid state. A dense fluid may have a high solvating and diffusivities properties similar to a supercritical fluid.  
      One method of cleaning substrate structures consists of applying a supercritical fluid thereto, such as a carbon dioxide fluid at a pressure greater than about 1,000 psi and at a temperature of at least about 31° C. The carbon dioxide fluid may further include a co-solvent, such as methanol, surfactants, chelating agents, and combinations thereof. Cleaning of the substrate structure via this method may be accomplished without the need for a wet clean.  
       FIG. 20  is a schematic cross-sectional view of an exemplary chamber, hereinafter referred to as supercritical clean chamber  2100 , which may be used in embodiments of the invention. Supercritical clean chamber  2100  is adapted to apply a supercritical fluid and/or a dense fluid to a substrate. Supercritical clean chamber  2100  contains a sealed process enclosure  2108 , a substrate support  2114  disposed in the sealed process enclosure  2108  and optionally one or more sonic transducers  2115  attached to the substrate support  2114 . The sonic transducers  2115  create acoustic or sonic waves directed towards the surface of a substrate to help agitate the fluid during processing. Heating elements  2132  are disposed proximate or inside the walls of supercritical clean chamber  2100  to heat the fluid to the desired temperature during processing. The supercritical and/or dense fluid is transferred to the sealed process enclosure  2108  through a fluid line  2123  by a pump/compressor  2126  at a desired pressure, typically between about 1,000 psi and 5,000 psi and temperature, typically at least about 31° C., and is applied to the substrate via a showerhead or diffuser plate (not shown) located in the sealed process enclosure  2108 . Optimum exposure time of the substrate to the supercritical fluid varies depending on the geometry of the substrate structure, such as aspect ratio, and type of contamination to be removed therefrom. Optionally, heating elements  2143  may heat the carbon dioxide fluid to a desired temperature as the fluid is being transferred though the fluid line  2123 .  
      A detailed description of an exemplary supercritical clean chamber that may be used in embodiments of the invention may be found in commonly assigned U.S. patent application Ser. No. 11/038,456 entitled “Using Supercritical and/or Dense Fluids in Semiconductor Applications,” filed on Jan. 18, 2005, which is hereby incorporated by reference in its entirety.  
      B. Electroless Deposition System with SRD and In Situ IBC  
      1. Applications of Cluster Tool Configuration  
       FIG. 11  illustrates one embodiment of a cluster tool  200  that generally includes electroless plating chambers and spin-rinse drying chambers. Optionally, it may include ALD barrier layer, reducing layer, and/or catalytic layer deposition prior to wet processing. Optionally, it may also include a plasma-enhanced dry etch chamber or supercritical clean chamber for removal of native oxide prior to barrier or catalytic layer deposition. This configuration of cluster tool  200  may be used to process substrate structures with ALD or CVD tantalum nitride (TaN), an electroless copper electroless seed layer deposition and/or seed layer repair, fill interconnect features with electroless gap fill deposition, deposit both seed layer and gap fill sequentially, or deposit a capping layer, such as cobalt, on extant interconnect features. In instances when this embodiment is used either for interconnect gap fill or for forming a seed layer that will be followed by electroless gap fill, the cluster tool may also be configured with IBC capability incorporated into the electroless plating twin cells, allowing the necessary post-deposition cleaning of substrates prior to removal from the wet processing platform.  
      2. Description of Cluster Tool Configuration  
       FIG. 11  illustrates cluster tool  200 , which generally includes electroless plating and spin-rinse drying. In this embodiment, processing stations  214  and  216  may be configured as an interface between the wet processing platform  213  and the generally dry processing stations or factory interface  230  of the plating cluster tool  200 . As such, substrates are introduced into wet processing platform  213  by being placed in an in-station  972  while waiting for wet processing. The in-station  972  is typically located above or below processing stations  214  and  216  (not shown in  FIG. 11  for clarity, see  FIG. 11A ). In addition to the in-stations, processing stations  214  and  216  each include an SRD chamber which performs the final wet processing steps on a substrate before the substrate leaves wet processing platform  213 . Alternatively, processing stations  214  and  216  may instead consist of a combination IBC/SRD chamber, wherein the bevel clean process is performed on a substrate followed immediately by the final rinse and dry process. In this embodiment, processing stations  202  and  204  may comprise an electroless plating twin cell, processing stations  206  and  208  a second electroless plating twin cell, and processing stations  210  and  212  a third electroless plating twin cell. Each electroless twin cell is contained by a processing enclosure  302 . Each twin cell also includes a substrate transfer shuttle (not shown in  FIG. 11  for clarity, see  FIG. 6 ) for substrate transfers between the first and second processing stations inside each processing enclosure  302 . Alternately, each electroless plating twin cell may also include the functionality of an IBC chamber, i.e. the post-deposition cleaning of unwanted material and contamination from the bevel portion and backside of a substrate.  
      Processing stations  235  and  235   a , which are located on the dry side of the cluster tool, may be configured as an ALD or CVD chamber for the deposition of a barrier layer and/or catalytic layer prior to wet processing. In some embodiments, the catalytic layer so formed is a ruthenium-containing layer deposited without the use of carbon-containing precursors. In another embodiment, a dry etch chamber or supercritical clean chamber is positioned at processing station  235  or  235   a.    
      3. Process Sequences  
      Typical substrate processing sequences for this embodiment of the invention are detailed in the flow charts illustrated in  FIGS. 12A, 12B ,  12 C,  12 D, and  12 E.  
      a) Single Layer Metal Deposition  
      When the cluster tool  200  is used for depositing a single layer of metal on substrates, i.e., either a seed layer, gap fill, or an interconnect capping layer, then it may be advantageous to have all of the electroless deposition processes performed on a substrate take place in a single electroless plating twin cell. In one aspect, the second and third electroless twin cells may also operate in parallel with the first twin cell and perform the same deposition process on other substrates going through a desired process sequence. The substrate processing sequences for this scenario are shown in  FIGS. 12A, 12B , and  12 C.  
      In Step  1200 , a substrate is pre-treated with a barrier layer, a reducing layer, and/or a catalytic layer in chamber positioned at processing station  235  prior to wet processing. In one aspect, the chamber positioned at processing station  235  may use the ruthenium tetroxide-based process described above to deposit the catalytic layer. In another aspect, native oxide is removed from the substrate prior to pre-treatment with a barrier, reducing and/or catalytic layer in a dry etch chamber or supercritical clean chamber positioned in factory interface  230 .  
      In step  1201 , factory interface robot  232  places a substrate at the in-station  972  associated with processing stations  214  or  216 .  
      In step  1202 , mainframe robot  220  transfers the substrate to the first processing station of one of the electroless twin plating cells, i.e., processing station  202 ,  206 , or  210 . Hence, a substrate may undergo the deposition step  1202  in any one of the electroless twin cells and then continue on to step  1203 . In this configuration, a substrate is not processed in more than one twin cell. As part of the process of electroless deposition, the substrate may be transferred as necessary between processing stations internally within an electroless twin cell via internal substrate transfer shuttle  605 , i.e., between processing stations  202  and  204 ,  206  and  208 , or  210  and  212 . As described above, electroless deposition process steps may be divided between the two processing stations in an electroless twin chamber or all deposition process steps may be performed in each electroless processing station.  
      If the substrate is treated in step  1202  with interconnect gap fill, then the IBC process also is necessary. In one aspect, a dedicated IBC chamber may perform the IBC process on substrates. In another aspect, either the electroless plating cells or the SRD chambers may include the functionality of an IBC chamber, as described above in conjunction with  FIGS. 3 and 4 . The IBC process removes unwanted deposition from the substrate bevel and residual contamination from the substrate backside. Either the IBC process is performed on substrates in an electroless plating cell immediately after the electroless deposition of step  1202 , or the IBC process is performed after the substrate is transferred to an external IBC chamber, i.e., with a dedicated IBC or a combined IBC/SRD chamber. Hence there are three possible processing sequences for this embodiment of the invention, depending on what IBC process is required. These sequences are illustrated in  FIGS. 12A, 12B , and  12 C. Process steps  1200 ,  1201 , and  1202  are identical for all three of these sequences.  
       FIG. 12A  illustrates a substrate processing sequence I which no IBC process is performed, for example the invention is used for deposition of an electroless capping layer, such as capping layer  105 , depicted in  FIG. 1B . After completing process steps  1200 - 1202 , process step  1204  is performed. In step  1204 , mainframe robot  220  transfers the substrate to SRD chamber positioned at processing station  214  or  216 , wherein the final rinsing and drying of the substrate take place. In step  1205 , after the SRD process is complete, factory interface robot  232  removes the substrate from the SRD and wet processing platform  213 . This embodiment of the invention allows the high throughput deposition sequence either used to form an interconnect capping layer or an electroless seed layer on substrates by applying multiple electroless twin cells in parallel.  
       FIG. 12B  illustrates the substrate processing sequence when the IBC process is desired and some or all of the electroless plating cells are configured to perform the IBC process described in conjunction with  FIGS. 7 and 8 . In step  1203   b , after completing process steps  1200 - 1202 , the substrate undergoes the IBC process prior to being transferred out of the twin cell. In step  1204 , mainframe robot  220  transfers the substrate to SRD chamber positioned at processing stations  214  or  216 , wherein the final rinsing and drying of the substrate take place. In step  1205 , after the SRD process is complete, factory interface robot  232  removes the substrate from the SRD and wet processing platform  213 . By using up to 3 electroless twin plating cells in parallel, this embodiment of the invention allows high throughput electroless gap fill of interconnect features on substrates and in situ substrate bevel clean prior to removal from the wet processing platform.  
       FIG. 12C  illustrates the substrate processing sequence when the IBC process is desired and wet processing platform  213  is configured with combined IBC/SRD chambers. In step  1203 c, after completing process steps  1200 - 1202 , mainframe robot  220  transfers the substrate to IBC/SRD chamber positioned at processing station  214  or  216 , wherein the IBC process is performed on the substrate. In step  1204 , the substrate undergoes the final SRD process in the IBC/SRD chamber. In step  1205 , after the SRD process is complete, factory interface robot  232  removes the substrate from the IBC/SRD and wet processing platform  213 . By using up to 3 electroless twin plating cells in parallel, this this embodiment of the invention allows high throughput electroless gap fill of interconnect features on substrates and in situ substrate bevel clean prior to removal from the wet processing platform.  
      b) Multiple Layer Metal Deposition  
      In one embodiment of the cluster tool  200 , it may be beneficial to have each substrate processed in two or more electroless plating cells. In this configuration, one or two of the electroless twin cells may be dedicated to seed layer deposition and/or repair and the remaining electroless twin cell or cells is/are dedicated to gap fill deposition. As an example, twin cells positioned at processing stations  202 / 204  and  206 / 208  may be configured for seed layer deposition and twin cell positioned at processing stations  210 / 212  may be configured for gap fill deposition (see  FIG. 11 ). These configurations for the pairs of processing stations  202 / 204 ,  206 / 208 , and  210 / 212  may be rearranged without affecting the functionality of the invention and are defined above only for purposes of description.  
      The processing sequence for this application of the invention is illustrated in  FIG. 12D . Steps  1200 ,  1201 ,  1204 , and  1205  are identical to the steps described above in  FIGS. 12A, 12B , and  12 C. In this processing sequence, however, the electroless deposition takes places in two steps,  1202   a  and  1202   b . In step  1202   a , the substrate is transferred from one of the in-stations to processing station  202  or  206  for seed layer deposition. In step  1202   b , after seed layer deposition is completed in twin cell positioned in processing stations  202 / 204  or  206 / 208 , the substrate is transferred to processing station  210 / 212  for gap fill deposition. In one aspect, each processing station in each electroless twin cell may then act as an independent electroless plating cell. In this case, in step  1202   a  seed layer deposition may take place in any one of four processing stations:  202 ,  204 ,  206 , or  208  and in step  1202   b , the electroless gap fill deposition may take place in either processing station  210  or  212 . Further, if the substrate has been pre-treated with a catalytic layer in processing station  235  prior to wet processing, processing stations  202 ,  204 ,  206 , or  208  may act as independent electroless plating cells.  
      Because the electroless gap fill process of step  1202   b  typically results in unwanted deposition on the substrate bevel, an IBC process (step  1203 ) may be performed on substrates prior to their removal from wet processing platform  213 .  
      In the processing sequence shown in  FIG. 12D , step  1203  may be performed as described above in either step  1203   b  or  1203   c , depending on the configuration of wet processing platform  213 . Either the electroless twin cells or the SRD chambers will need to have the capability of performing an IBC process incorporated into them.  
      In steps  1204  and  1205 , the substrate is given a final rinse, dried, and transferred out of wet processing platform  213 . This embodiment of the invention allows sequential deposition of an electroless seed layer on a substrate and electroless gap fill of the interconnect features on the substrate, followed by in situ bevel clean of the substrate prior to removal from the wet processing platform. In one aspect, a barrier layer may be deposited on the substrate immediately prior to wet processing, improving adhesion of the subsequent metal layers. The process of sequential deposition minimizes both the amount and variation of oxidation of the seed layer prior to gap fill over the prior art. Additionally, only a single processing platform is required to complete three deposition steps on a substrate structure, reducing system cost and fabrication facility cost.  
      c) Electroless Deposition with Intermediate Rinse  
      A third substrate processing sequence for this embodiment of the invention includes performing an intermediary spin-rinse-dry process on substrates after processing in the first processing station of an electroless twin cell and before processing in the second processing station. This processing sequence may be beneficial for electroless plating chemistries for which a completely clean and dry substrate is preferred for the second electroless plating process. This substrate processing sequence is illustrated in  FIG. 12E . Steps  1200 ,  1201 ,  1203 , and  1204  are identical to the steps described in  FIGS. 12A, 12B , and  12 C.  
      As shown in  FIG. 12E , step  1202   c  follows step  1201  (i.e., the substrate is transferred into wet processing platform  213 ). In step  1202   c , the substrate is transferred to the first processing station of an electroless twin cell, e.g. processing station  202 ,  206 , or  210 , and and an electroless process is performed therein. The process performed on the substrate may be a complete electroless deposition process or some combination of the initial steps thereof, e.g. preparatory clean, activation, and post-activation clean for selective deposition, or catalytic layer deposition for non-selective deposition.  
      In step  1202   d , the substrate is transferred to an SRD chamber, such as SRD  400 , wherein the substrate is rinsed and/or dried via the SRD process described in conjunction with  FIG. 4 .  
      In step  1202   e , the substrate is transferred to the second processing station of the electroless twin cell, e.g., processing station  204 ,  208 , or  212 , and is processed therein. The process performed on the substrate may be the completion of the electroless deposition process already begun on the substrate, or, if a first metal layer was deposited in step  1202   c , a second metal layer may be deposited via electroless plating. Alternately, in embodiments in which the IBC process is required and the electroless plating twin cells include the functionality of an IBC chamber, the final deposition step, i.e.  1202   e , may also include performing the IBC process on the substrate via the IBC process described in conjunction with  FIG. 3 .  
      In steps  1204  and  1205 , the substrate is given a final rinse, dried, and transferred out of wet processing platform  213 . For embodiments of the invention in which processing stations  214  and  216  are combination IBC/SRD chambers, the step  1204  may include both the IBC and SRD processes.  
      4. Description of Process Chambers  
      Embodiments of the invention include the incorporation of multiple substrate processing chambers onto a single cluster tool, including electroless, SRD and ALD or CVD chambers. Examples of these chambers and the processes performed on substrates therein have been described previously.  
      C. Electroless Deposition System with Brush Box and SRD  
      1. Applications of Cluster Tool Configuration  
      In one embodiment, illustrated in  FIGS. 11 and 11 A by the cluster tool  200  includes an electroless plating chamber, a brush box substrate clean chamber and a spin-rinse drying chamber. This configuration allows deposition of capping layers on high density interconnect features with low defects, because it remove loose metallic particles formed on the substrate surface during electroless deposition. Other applications include deposition of an electroless seed layer deposition of electroless gap fill.  
      2. General Description of Cluster Tool Configuration  
      In one embodiment, processing station  214  acts as the interface between the wet processing platform  213  and the generally dry processing stations or factory interface  230  of the plating cluster tool  200 . As such, the SRD chamber for wet processing platform  213  and an in-station  972  are located at processing station  214 , as shown in  FIG. 11A . The in-station  972  may be located either above or below the SRD chamber. In one aspect, processing station  216  is configured as a brush box  216   a  for post-deposition cleaning of substrates (see  FIG. 11A ). Brush box  216   a  may be configured to accept substrates that are oriented either horizontally or vertically. In this embodiment, processing stations  202  and  204  comprise an electroless plating twin cell, processing stations  206  and  208  comprise a second electroless plating twin cell, and processing stations  210  and  212  comprise a third electroless plating twin cell. These configurations for the pairs of processing stations  202 / 204 ,  206 / 208 , and  210 / 212  may be rearranged without affecting the functionality of the invention and are defined above only for purposes of description. Each electroless twin cell is contained by a processing enclosure  302 . Each twin cell also includes a substrate transfer shuttle (not shown for clarity) for substrate transfers between the first and second processing stations inside each processing enclosure  302 . Alternately, each electroless plating twin cell may also includes the functionality of an IBC chamber, i.e. the post-deposition cleaning of unwanted material and contamination from the bevel portion and backside of a substrate. This configuration of wet processing platform  213  may be used to deposit an electroless capping layer on interconnect features, process substrate structures with electroless seed layer deposition, fill interconnect features with electroless gap fill deposition, or to deposit both seed layer and gap fill on a substrate sequentially.  
      For non-selective electroless deposition, dry side processing station  235  may be configured as an ALD or CVD chamber for the deposition of a barrier layer and/or catalytic layer prior to wet processing. Optionally, a pre-deposition dry etch chamber positioned at processing station  235   a  may also be included in factory interface  230  for the removal of native oxide from the substrate (see  FIG. 11 ).  
      3. Process Sequence  
      A typical substrate processing sequence  1300  for this embodiment of the invention is detailed in the flow chart illustrated in  FIG. 13 .  
      In step  1301 , one or more electroless deposition steps may be completed on the substrate. Any of the substrate processing sequences detailed in  FIGS. 12A, 12B , or  12 C,  12 D, or  12 E may be used to complete electroless deposition for this embodiment of the invention, i.e., steps  1201  and  1202 , or steps  1201 ,  1202   a , and  1202   b , or steps  1201 ,  1202   c ,  1202   d , and  1202   e . However, rather than transferring the substrate directly to an SRD chamber when electroless deposition is complete (as shown in  FIGS. 12A, 12B , and  12 C), a brush box substrate clean is first performed. Alternately, in embodiments in which the electroless plating twin cells include the functionality of an IBC chamber, the final deposition step, i.e.,  1202 ,  1202   b , or  1202   e , may also include performing the IBC process on the substrate as described above.  
      In step  1302 , main frame robot  220  transfers the substrate from an electroless plating cell to brush box  216   a , wherein a substrate surface brush clean process, described below in conjunction with  FIG. 8A , is performed to remove any unwanted surface contamination, for example the enlarged metallic particles  104   b  depicted in  FIG. 1B .  
      In step  1303 , the substrate is transferred to the SRD chamber and the final rinse and dry process is performed via the SRD process described in conjunction with  FIG. 4 .  
      In step  1304 , the substrate is transferred out of wet processing platform  213  from the SRD. The incorporation of a brush box chamber on wet processing platform  213  makes possible the formation of low-defect capping layers on interconnect features.  
      4. Description of Brush Box Chamber  
      In one configuration of cluster tool  200 , a brush box chamber is used for post-deposition clean of substrates prior to their removal from the wet processing platform. Brush box chambers are generally used to remove residual contaminants from the surface of a substrate after the CMP process. Brush box chambers conventionally clean or scrub residue substrate surfaces via mechanical scrubbing devices, which may employ polyvinyl acetate (PVA) brushes, brushes made from other porous or sponge-like material, or brushes made with nylon bristles, etc. However, configurations of cluster tool  200  may also use brush box chambers for the removal of loosely bound metallic contamination that has formed on the surface of a substrate during the electroless deposition process, such as the enlarged metallic particles  104   b  (shown in  FIG. 1B ). This procedure can greatly reduce defects associated with the electroless deposition of capping layers on interconnect features.  
      Typically, brush box chambers clean a vertically-oriented substrate by lowering the substrate between cylindrical, rotating brushes. The substrate itself may also be rotated by means of powered rollers on which the substrate rests. Liquid cleaning solutions are applied to the substrate by spray nozzles and/or through the scrubber brushes.  
       FIG. 8A  is a side perspective view of an exemplary brush box scrubbing device, hereinafter referred to as scrubbing device  11 , that may be used in embodiments of the invention. The scrubbing device  11  comprises a pair of PVA brushes  13   a  and  13   b . Each brush comprises a plurality of raised nodules, hereinafter referred to as nodules  15 , across the surface thereof, and a plurality of valleys  17  located among the nodules  15 . The PVA brushes  13   a  and  13   b  are supported by a pivotal mounting (represented generally by reference number  18 ) adapted to move the PVA brushes  13   a  and  13   b  into and out of contact with the substrate W 1  supported by the substrate support  19 , thus allowing the PVA brushes  13   a  and  13   b  to move between closed and open positions so as to allow a substrate W 1  to be extracted from and inserted therebetween as described below. The scrubbing device  11  also comprises a substrate support  19  adapted to support and further adapted to rotate a substrate W 1 . In one aspect, the substrate support  19  may comprise a plurality of rollers  19   a - c  each having a groove adapted to support the substrate W 1  vertically. A first motor M 1  is coupled to the PVA brushes  13   a  and  13   b  and adapted to rotate the PVA brushes  13   a  and  13   b . A second motor M 2  is coupled to the substrate support rollers  19   a - c  and adapted to rotate the rollers  19   a - c . The scrubbing device  11  may further comprise a plurality of spray nozzles  21  coupled to a source  23  of fluid via a supply pipe  25 . The spray nozzles  21  may be positioned to spray a fluid (e.g., Dl water, SC 1 , dilute hydrofluoric acid, or any other liquid solution used for cleaning) at the surfaces of the substrate W 1  or at the PVA brushes  13   a  and  13   b  during substrate scrubbing. Alternatively or additionally, fluid may be supplied through the PVA brushes  13   a  and  13   b  themselves as is conventionally known.  
      In a typical brush clean process, a substrate W 1  may be positioned onto the substrate support  19 , for example by substrate edge gripper device  971 , described below in conjunction with  FIG. 9A . PVA brushes  13   a  and  13   b  may be positioned apart to allow a substrate W 1  to be positioned onto the substrate support  19 . Once substrate W 1  is resting on the substrate support rollers  19   a - c  of substrate support  19 , substrate support rollers  19  PVA brushes  13   a  and  13   b  are rotated at a rate that rotates substrate W 1  between about 20 rpm and about 200 rpm. PVA brushes  13   a  and  13   b  are rotated at a rate between about 120 rpm and 400 rpm and are moved into contact with substrate W 1 . A spray fluid, described above, is then applied to the substrate either via spray nozzles  21 , through PVA brushes  13   a  and  13   b , or both, for between about 30 seconds and about 200 seconds while PVA brushes  13   a  and  13   b  continue to scrub the surface of substrate W 1 . The substrate W 1  is cleaned by the frictional and drag forces generated between the rotating PVA brushes  13   a  and  13   b , and by the cleaning/rinsing action of the fluid. PVA brushes  13   a  and  13   b  are then positioned away from substrate W 1  and substrate support rollers  19   a - c  stop rotating to allow removal of substrate W 1  from the brush box chamber. A substrate-handling robot, such as substrate edge gripper device  971 , then removes substrate W 1  from the brush box chamber.  
      A detailed description of an exemplary brush box chamber that may be used in embodiments of the invention may be found in commonly assigned U.S. Pat. No. 6,558,471, entitled “Scrubber Operation,” filed on Jan. 26, 2001, which is hereby incorporated by reference in its entirety.  
      D. Electroless Deposition System with IBC and SRD Chambers  
      One embodiment of the wet processing platform  213 , illustrated in  FIGS. 2 and 2 A, generally includes an electroless plating chamber, a substrate bevel clean chamber, and a spin-rinse drying chamber. Optionally, this embodiment may also include ALD barrier layer deposition prior to wet processing.  
      1. Applications of Cluster Tool Configuration  
      This configuration may be used to process substrate structures with barrier layer deposition and electroless seed layer deposition and/or seed layer repair, fill high aspect ratio interconnect features with electroless gap fill deposition, or deposit both seed layer and gap fill on a substrate sequentially. Advantages in substrate processing throughput may also be realized due to the use of dedicated SRD and IBC chambers. This is because the IBC chamber is typically a throughput bottleneck and this configuration provides two IBC chambers.  
      2. General Description of Cluster Tool Configuration  
      In this embodiment, processing stations  214  and  216  may be configured as an interface between the wet processing platform  213  and the generally dry processing stations or factory interface  230  of the cluster tool  200 . As such, substrates are introduced into wet processing platform  213  by being placed in an in-station  972  while waiting for wet processing. The in-station  972  is typically located above or below processing stations  214  and  216 , as shown in  FIG. 2A . In addition to the in-stations, processing stations  214  and  216  each include an SRD chamber which performs the final wet processing steps on a substrate before the substrate leaves wet processing platform  213 . In this embodiment, processing station  235  may be configured as an ALD or CVD chamber for the deposition of a barrier layer and/or catalytic layer prior to wet processing. In some embodiments, the catalytic layer so formed is a ruthenium-containing layer deposited without the use of carbon-containing precursors. Processing stations  202  and  204  comprise an electroless plating twin cell configured for seed layer deposition or repair, processing stations  210  and  212  comprise a electroless plating twin cell configured for gap fill deposition, and processing stations  206  and  208  are standard IBC chambers. These configurations for the pairs of processing stations  202 / 204 ,  206 / 208 , and  210 / 212  may be rearranged without affecting the functionality of the invention and are defined above only for purposes of description. Each electroless twin cell is contained by a processing enclosure  302 . Each twin cell may also include an internal substrate transfer shuttle  605  for transferring substrates between the first and second processing stations inside each processing enclosure  302 . This configuration of wet processing platform  213  is typically used to sequentially process substrate structures with barrier layer and electroless seed layer deposition and/or seed layer repair followed by electroless gap fill. Sequential deposition minimizes both the amount and variation of oxidation of the seed layer prior to gap fill over the prior art. Electroless gap fill has the added benefit of being capable of filling high aspect ratio features. Additionally, only a single processing platform is required to complete three deposition steps on a substrate structure. Further, because the most time-consuming process, i.e., the IBC process, is performed by dedicated IBC chambers and is not incorporated into either the SRD chambers or the electroless plating twin cells, throughput may be increased for the deposition of some films.  
      3. Process Sequence  
      A processing sequence is illustrated in  FIG. 15 .  
      In step  1501 , factory interface robot  232  places a substrate at the in-station  972  associated with processing stations  214  or  216 .  
      In step  1502 , mainframe robot  220  transfers the substrate to processing station  202  for seed layer deposition.  
      In step  1503 , mainframe robot  220  transfers the substrate to processing station  210  for electroless gap fill of interconnect features. All electroless deposition processes necessary for seed layer deposition take place in the twin cell located at processing stations  202 / 204  and all electroless deposition processes necessary for gap fill take place in twin cell located at processing stations  210 / 212 . The substrate is transferred between processing stations  202  and  204  or  210  and  212  via internal substrate transfer shuttle  605  as necessary. Typically, the reducing layer and catalytic layer formation steps are performed in the first processing station of the seed layer twin cell, i.e. processing station  202  via the reducing layer and catalytic layer formation processes described above in conjunction with  FIG. 14 . The electroless plating step is performed in the second processing station, i.e. processing station  204  using the electroless deposition process described above in conjunction with  FIG. 7 . Alternatively, when the substrate has been processed with a catalytic layer prior to wet processing, all electroless deposition can take place in a single processing station. Processing stations  202  and  204  then act as two independent seed layer plating cells. Processing stations  210  and  212  typically act as two independent gap fill plating cells in this configuration and generally do not require substrate transfers via internal substrate transfer shuttle  605 . Hence, step  1502  includes transferring the substrate from one of the in-stations to either processing station  202  or  204  for seed layer deposition/repair and step  1503  includes transferring the substrate to either processing station  210  or  212  for gap fill deposition.  
      In step  1504 , upon completion of gap fill deposition, the substrate is transferred to the IBC chamber positioned at processing stations  206  or  208  for removal of unwanted deposition on the substrate edge and bevel via the IBC process described in conjunction with  FIG. 3 . In step  1505 , mainframe robot  220  transfers the substrate to SRD chamber positioned at processing station  214  or  216  for final rinsing and drying via the SRD process described in conjunction with  FIG. 4 .  
      In step  1506 , after the SRD process is complete, factory interface robot  232  removes the substrate from the SRD and the wet processing platform  213 .  
      E. Electroless Deposition Platform with Brush Box and Vapor Dryer  
      1. Applications of Cluster Tool Configuration  
      One embodiment of the invention is illustrated in  FIGS. 11 and 11 A by exemplary wet processing platform  213  and generally includes electroless plating, brush box substrate clean and vapor drying chambers, also known as solvent drying chambers. This configuration of cluster tool  200  may be used to deposit capping layers on interconnect features. This embodiment may also process substrate structures with electroless seed layer deposition, fill interconnect features with electroless gap fill deposition, or deposit both seed layer and gap fill sequentially. In this case, the dry side processing station  235  may be configured as an ALD/CVD pre-treatment chamber for deposition of a barrier layer and/or catalytic layer. In some embodiments, the catalytic layer so formed is a ruthenium-containing layer deposited without the use of carbon-containing precursors. In some aspects, a plasma-enhanced dry etch is performed on the substrate in a chamber positioned in processing station  235   a  inside factory interface  230  prior to deposition.  
      This embodiment of the invention allows the formation of capping layers over interconnect features without the defects caused by watermarks, which are created during a conventional spin-rinse-dry process. Also, capping layers formed with this embodiment of the invention are much less likely to include leakage paths between the capped interconnects due to the post-deposition brush box cleaning process. This configuration of cluster tool  200  may also be used to sequentially process substrate structures with electroless seed layer deposition followed by electroless gap fill. Sequential deposition minimizes both the amount and variation of oxidation of the seed layer prior to gap fill. Electroless gap fill has the added benefit of being capable of filling high aspect ratio features using the process method described above in Step  504  and in conjunction with  FIGS. 7 and 8 . Additionally, only a single processing platform is required to complete two deposition steps on a substrate structure. Further, this embodiment of the invention removes most surface particles from substrates and eliminates watermark-related defects caused by SRD chambers when rinsing hydrophobic substrates.  
      2. General Description of Cluster Tool Configuration  
      In this embodiment, processing station  214  may act as the interface between the wet processing platform  213  and the generally dry processing stations or factory interface  230  of the cluster tool  200 . As such, the vapor dryer chamber for wet processing platform  213  and an in-station  972  are located at processing station  214 . The in-station  972  (shown in  FIG. 9A ) may be located above the vapor dryer chamber and holds substrates for future wet processing (as shown in  FIG. 11 ). The vapor dryer performs the final wet processing step on substrates processed by wet processing platform  213  and includes a substrate platform that serves as a holding location for clean, dry substrates which are subsequently removed from wet processing platform  213 . Processing station  216  is configured as a brush box chamber for post-deposition cleaning of substrates. The brush box located at processing station  216  may be configured to accept substrates that are oriented either horizontally or vertically. In this embodiment, processing stations  202  and  204  comprise an electroless plating twin cell, processing stations  206  and  208  comprise a second electroless plating twin cell, and processing stations  210  and  212  comprise a third electroless plating twin cell.  
      In another configuration, the brush box  216   a  and vapor dryer  216   b  are configured together at processing station  216 , as shown in  FIG. 11A . In-station  972  is still located in processing station  214 . After the final vapor dry process step is completed on a substrate, the substrate is transferred to the vapor dryer substrate platform located in factory interface  230 , as shown in  FIG. 11A .  
      One embodiment of the invention may be used wherein the vapor dryer and brush box are not located at processing stations  214  and  216  respectively, but are both located at processing stations  202 / 204  or  210 / 212 . The vapor dryer and brush box are more serviceable in this embodiment due to the improved access from the side of wet processing platform  213 .  
      3. Process Sequences  
      a) Capping Layer Deposition  
      When this configuration is used for depositing a capping layer on a substrate, then all electroless deposition processes may take place in a single electroless plating twin cell. The second and third electroless twin cells may operate in parallel with the first twin cell and perform the same deposition process on other substrates. A typical substrate processing sequence for depositing a capping layer with this embodiment of the invention is detailed in the flow chart illustrated in  FIG. 16 . Steps  1200  and  1201  in  FIG. 16  are identical to steps  1200  and  1201  in  FIG. 12  and are described above.  
      Step  1602  is similar to step  1202  described above in conjunction with FIGS.  12 A-C, except that selective electroless deposition is performed on the substrate, i.e., the formation of a capping layer on exposed interconnect features. Alternately, the selective electroless plating step  1602  may also include additional vapor drying steps, wherein the substrate is removed from the electroless plating cell by mainframe robot  220 , transferred to vapor dryer positioned at processing station  214  and processed therein, and returned via mainframe robot  220  to the appropriate electroless cell for completion of the electroless plating process. These additional vapor drying steps may occur prior to the preparatory clean step, as described above in Step  501 , of the electroless plating process.  
      In step  1603 , upon completion of capping layer deposition, the substrate is transferred to the brush box  216   a  or to a brush box chamber located at processing station  216  to remove any unwanted contamination from the surface of the substrate. The brush box process is described above in conjunction with the brush box chamber description and  FIG. 8A .  
      In step  1604 , after the brush box substrate clean is complete, the substrate is transferred to vapor dryer  214   a  or to a vapor dryer positioned at processing station  214  for the final vapor dry process, which is described below in conjunction with the vapor dryer chamber description.  
      In step  1605 , after the vapor dry process is complete, factory interface robot  232  removes the substrate from the vapor dryer substrate platform and the wet processing platform  213 .  
      b) Multiple Metal Layer Deposition  
      When this embodiment of the invention is used for depositing multiple layers of metal on substrates, e.g., a seed layer followed sequentially by other electroless deposition processes, then each substrate is processed by more than one twin electroless cell. In this application of the invention, one or two of the electroless twin cells are dedicated to seed layer deposition and the remaining electroless twin cell or cells is/are dedicated to gap fill deposition. As an example, twin cells positioned at processing stations  202 / 204  and  206 / 208  may be configured for seed layer deposition and twin cell positioned at processing stations  210 / 212  may be configured for gap fill deposition. These configurations for the pairs of processing stations  202 / 204 ,  206 / 208 , and  210 / 212  may be rearranged without affecting the functionality of the invention and are defined above only for purposes of description. The processing sequence for this application of the invention is illustrated in  FIG. 17 . Steps  1200 ,  1201 ,  1202   a , and  1202   b  are identical to steps  1200 ,  1201 ,  1202   a , and  1202   b  in  FIG. 12B  and described above. Alternately, the electroless plating step  1202  may also include additional vapor drying steps, wherein the substrate is removed from the electroless plating cell by mainframe robot  220 , transferred to vapor dryer positioned at processing station  214  and processed therein, and returned via mainframe robot  220  to the appropriate electroless cell for completion of the electroless plating process. These additional vapor drying steps may occur prior to the dielectric clean and/or prior to the metal clean steps, which are included in the preparatory clean step. The preparatory clean step is part of the electroless plating process and is described above in Step  501  in conjunction with  FIGS. 7 and 8 . Steps  1603 ,  1604 , and  1605  in  FIG. 17  are identical to steps  1603 ,  1604 , and  1605  in  FIG. 16  and described above. In instances when this embodiment is used either for interconnect gap fill or for forming a seed layer that will be followed by electroless gap fill, it should be noted that the cluster tool must also be configured with IBC capability incorporated into the electroless plating twin cells, allowing the necessary post-deposition cleaning of substrates prior to removal from the wet processing platform.  
      4. Description of Process Chambers  
      Embodiments of the invention include the incorporation of multiple substrate processing chambers onto a single cluster tool, including electroless, brush box, vapor dryer and ALD or CVD chambers. Examples of most of these chambers and the processes performed on substrates therein have been described previously. A general description of vapor dryer chambers and vertical substrate handling is provided below.  
      a) Vapor Dryer Chamber  
      The vapor drying process is typically performed after completing a metal deposition process, e.g., the electroless capping layer process, to prevent watermarks and to remove any residue on the substrate from prior processes. Vapor drying may also be used in lieu of a final spin-rinse-dry prior to removing a substrate from a wet processing platform. Vapor drying includes introducing a surface tension-reducing volatile compound, such as a volatile organic compound (VOC), to the substrate structure. For example, a VOC may be introduced with a carrier gas (e.g., nitrogen gas) in the vicinity of the liquid adhering to a substrate structure. The introduction of the VOC results in surface tension gradients which cause the liquid to flow off of the substrate, leaving it dry. In one embodiment, the VOC is isopropyl alcohol (IPA). In other embodiments, the VOC may be other alcohols, ketones, ethers, or other suitable compounds.  
       FIG. 9  is a schematic side view of one embodiment of a vapor drying apparatus  911  illustrating a progression of a substrate W° through the vapor drying apparatus  911 . The progression of the substrate (W°, W′, W″, W′″, and W″″) is illustrated by showing the substrate at different positions (W°, W′, W″, W′″, and W″″) as it passes through the vapor drying apparatus  911 . The vapor drying apparatus  911  includes a submersion chamber  918  and an upper separation wall  924  that separates a rinsing section  926  from a drying section  928 . In operation, a robot capable of holding a substrate vertically (such as a running beam robot, described in embodiments of the invention, below) loads a substrate W° into the rinsing section  926  via a load port  934 . Nozzles  930  and  932  spray Dl water onto both sides of the substrate W° to remove contaminates therefrom. To aid in removing particles from the rinsing section  926  (i.e., to minimize re-contamination of the substrate), fluid  927  such as Dl water or a cleaning solution may be continuously supplied, for example, to the lower portion of the submersion chamber  918  so that fluid continuously overflows to an overflow weir  920  surrounding the submersion chamber  918 . Subsequently, the running beam robot (not shown) releases the substrate W′ which is received onto a cradle  936 , and then retracts from the rinsing section  926  to its home position (not shown), above the load port  934 . An optical sensor (not shown) detects the presence of the substrate W′ on the cradle  936 , and signals an actuator to actuate a linkage system that causes the cradle  936  to rotate from a vertical position to an inclined position (e.g., 9°), for subsequent elevation through the drying section  928 . Using a pusher  944 , the substrate W″ is lifted towards an unload port  937 . As substrate W″ is lifted, the substrate edges lean by the force of gravity on the two parallel inclined guides  946  (only one shown) which are submerged in the fluid. As the substrate W′″ is lifted out of the fluid  927 , a pair of spray mechanisms  950  spray an IPA vapor and nitrogen mixture at the meniscus that forms on both sides of the substrate W′″. The specific angle of the flow of the IPA and nitrogen mixture may vary depending upon the type of material on the substrate to be dried. As the substrate W′″ exits the drying section  928  it pushes a catcher  960  causing the catcher  960  to move upward as the pusher  944  moves the substrate W′″ onto the substrate platform  958 , after which a finger  962  may lock to secure the substrate W′″ on the substrate platform  958 , thereby allowing the pusher  944  to retract. After the substrate W′″ is secured on the substrate platform  958 , the substrate platform  958  rotates to its horizontal position, also known as the output position, where a substrate handling robot (not shown in  FIG. 9 , but for example could be factory interface robot  232 ,  FIG. 2 ) may remove the substrate W″″ from substrate platform  958 . The substrate platform  958  then returns to its vertical position ready to receive the next processed substrate when it is elevated from the drying section  928 .  
      Examples of exemplary vapor drying processes are further described in the commonly assigned U.S. Pat. No. 6,328,814, filed Mar. 26, 1999 and U.S. patent application Ser. No. 10/737,732, entitled “Scrubber With Integrated Vertical Marangoni Drying”, filed Dec. 16, 2003, which is incorporated by reference in its entirety to the extent not inconsistent with the present disclosure.  
      It is believed that vapor drying the substrate structure before and/or after depositing a capping layer by selective electroless deposition assists in the removal of contaminants and other residue from prior processing steps. Such contaminants may cause, for example, watermarks and other surface defects. The residual compounds are difficult to remove with aqueous solutions from the low-k dielectric portion of the substrate structure since the low-k dielectric portion is a hydrophobic surface. Vapor drying with a volatile organic compound aids in removing contaminants from these surfaces along with any residual water—an important step in preventing electroless deposition of capping material on unwanted regions of substrate structures. Additionally, vapor drying may be used in conjunction with other deposition processes unrelated to capping layers in order to minimize watermarks and other residues and to speed drying time. A detailed description of embodiments of an apparatus and method of vapor drying is disclosed in commonly assigned U.S. Patent Application Publication Number 2003/0121170, entitled “Single Wafer Dryer and Drying Methods,” which is incorporated in its entirety to the extent not inconsistent with the present disclosure.  
      In addition to post deposition rinsing and drying, a vertically-oriented vapor dryer may also perform other wet processes on substrates, such as an SC-1 clean for removing organic contaminants or an HF-based native oxide clean, described below in conjunction with FIGS.  21 A-F.  
      b) Vertical Substrate Handling  
      Substrates cleaned vertically in brush box chambers and vapor dryers benefit from the assistance of gravity in removing particles and other contaminants from the substrate. Hence, the most effective configuration for brush box chambers and vapor dryer chambers is for vertically oriented substrates. Some embodiments of the invention include brush box chambers and vapor dryers configured for vertically oriented substrates. The 90 degree difference in substrate orientation between plating cells and brush box and vapor dryer chambers requires more than the traditional horizontally orientated substrate transfer mechanisms. Exemplary methods of combined vertical/horizontal substrate transfer as they are incorporated into embodiments of the invention are described below.  
      Embodiments of the invention require transfer of substrates from a conventional, horizontal substrate transfer robot, i.e., mainframe robot  220 , to processing chambers that typically require vertical orientation of the substrate, such as a brush box chamber and/or a vapor dryer chamber.  
       FIG. 9A  illustrates the apparatus required for substrate transfer into a brush box chamber, from a brush box chamber into a vapor dryer chamber, and from a vapor dryer out of wet processing platform  213 . Brush box chamber  975  and vapor dryer  974  are shown in processing stations  216  and  214 , respectively, on wet processing platform  213 . In-station  972  is shown configured above vapor dryer  974 . Running beam  250  and flipper robot  251  are shown in  FIG. 9A  and also in  FIG. 11 .  
      Transfer of a substrate from horizontal transfer robot, such as mainframe robot  220 , into a brush box chamber requires rotation of the substrate to a vertical orientation and a downward vertical motion into the brush box chamber. One method is to use a conventional horizontal transfer robot (not shown in  FIG. 9A ) that is also configured for rotating substrates to vertical orientation in conjunction with a brush box chamber that includes the added capability of transferring substrates downward into the brush box chamber. This requires a brush box chamber with a dedicated robot (not shown) for inserting substrates into brush box chamber  975 . More typically, the substrate is rotated to vertical either by the horizontal transfer robot or by flipper robot  251 . When the vertical orientation is performed by the horizontal transfer robot, the substrate may be placed in a vertical substrate holding station, also known as a crescent (not shown). When the vertical orientation is performed by flipper robot  251 , the horizontal transfer robot hands off a horizontal substrate to flipper robot  251 , which then rotates the substrate into vertical orientation. Running beam  250 , which is disposed directly over flipper robot  251 , brush box chamber  975 , and vapor dryer  974 , is used for vertical transfers of the substrate into and out of brush box chamber  975  and into vapor dryer  974  (See  FIG. 9A ). After vertical orientation, the substrate may be located on flipper robot  251  or in a vertical holding station (not shown). Vertical beam  970  moves along running beam rail  976  until directly over the substrate. The substrate  973   b  is removed by substrate edge gripper device  971 , which may move vertically along vertical beam  970 . Vertical beam  970  then moves along running beam rail  976  until directly over brush box chamber  975  and substrate edge gripper device  971  transfers the substrate  973   c  vertically downward into brush box chamber  975 . After cleaning in brush box chamber  975  is complete, substrate edge gripper device  971  removes substrate  973   b  vertically from brush box chamber  975 . Vertical beam  970  then moves along running beam rail  976  until directly over vapor dryer  974 . Substrate edge gripper device  971  transfers the substrate vertically downward into vapor dryer  974 . After cleaning in vapor dryer  974  is complete, substrate  973   d  is held on substrate platform  958  (shown more clearly in  FIG. 9A  and in  FIG. 2A ) where it awaits transfer out of wet processing platform  213  by factory interface robot  232  (see  FIG. 11 ).  
      The substrate transfer sequence above is summarized in the flow chart in  FIG. 9B . In step  9001 , electroless deposition is complete and the mainframe robot  220  holds a substrate horizontally. In step  9002  the mainframe robot rotates the substrate to vertical and transfers the substrate to a brush box robot (not shown), which then lowers the substrate into brush box chamber  975 . Alternately, in step  9003 , mainframe robot  220  rotates the substrate and transfers it to a vertical holding station. Alternatively, in step  9004 , mainframe robot  220  does not rotate the substrate to vertical and instead hands off the substrate to flipper robot  251 , which rotates the substrate to vertical. In step  9005 , running beam  250  transfers the substrate to brush box chamber  975 . In step  9006 , running beam  250  transfers the substrate to vapor dryer  974 . In step  9007 , the substrate is transferred from vapor dryer  974  out of the wet processing platform  213 .  
      F. Electroless Deposition Platform with Anneal Chamber  
      1. Applications of Cluster Tool Configuration  
      One embodiment of the invention is illustrated in  FIG. 11 , wherein exemplary cluster tool  200  is configured with oxide removal, electroless plating and anneal chambers. An optional configuration may include an acid strip chamber as well. This configuration of cluster tool  200  may be used to form a high quality, contact level connection to devices formed on a silicon-based substrate with an electroless silicide process. Exposed silicon-based materials that may be processed thereby include single crystal silicon, polysilicon, single crystal silicon-germanium, and polycrystalline silicon-germanium. Devices that may benefit from the electroless suicide process provided herein include transistors, memory elements, solar cell contacts and silicon contacts.  
      FIGS.  21 A-E are schematic cross-sectional views of a silicon contact  2150  illustrating a process of forming a silicide thereon using the inventive apparatus and method. Referring to  FIG. 21A , silicon contact  2150  is formed in a dielectric layer  2152 , wherein dielectric layer  2152  is formed on a substrate  2153 . Silicon contact  2150  may be formed in dielectric layer  2152  using conventional lithography and etching techniques to expose a portion of the surface of substrate  2153 . Substrate  2153  may composed of any of a number of conducting or semi-conducting, silicon-based materials, including single-crystal silicon, single-crystal silicon-germanium containing up to 50% atomic concentration germanium, polysilicon, and polysilicon-germanium. In this example, substrate  2153  is a single-crystal silicon substrate. A native oxide layer  2151  fills the bottom of silicon contact  2150  due to exposure of the silicon-based material of substrate  2153  to air via silicon contact  2150 . Other contaminants, such as thin layers of organic contaminants, may also be present on the surface of native oxide layer  2151 , but for clarity are not illustrated.  
      In order to create a high-quality, oxide-free and stable silicide on the exposed surface of substrate  2153 , a number of processes must be performed thereon, including native oxide removal, electroless metal deposition, rinse/dry, and anneal. It may also be beneficial to remove organic contaminants from the surface of substrate  2153  prior to these processes and to perform an acid strip following these processes.  
      As described above in conjunction with  FIG. 20 , organic contaminants on the surface of native oxide layer  2151  may be removed by the application of a supercritical fluid to the substrate in a supercritical clean chamber positioned on cluster tool  200 , such as supercritical clean chamber  2100 . Alternatively, native oxide  2151  may be removed in a wet clean chamber by an SC-1 cleaning process, also known as the RCA-1 clean. The SC-1 process is a wet cleaning decontamination process based on sequential oxidative desorption and complexing with H 2   0   2 , NH 4 OH, and water. The SC-1 cleaning chemistry and procedure are known in the art and easily implemented on any of the wet processing chambers previously described herein, including SRD, IBC, electroless deposition, and vapor dryer chambers. These chambers are described above in conjunction with  FIGS. 4, 3 ,  7 , and  9 , respectively.  
      After SC-1 clean, a native oxide clean is performed on silicon contact  2150  to remove native oxide layer  2151 .  FIG. 21 B  illustrates silicon contact  2150  after native oxide layer  2151  has been removed, leaving a silicon surface  2154  that is oxide-free.  
      In one aspect, native oxide layer  2151  is removed by an HF-based wet cleaning process, known as an HF last, or HFL process. The HF last process is a silicon surface preparation sequence in which HF etching of native oxide is performed at the end of the sequence leaving a silicon surface  2154  that is hydrogen-terminated (i.e., covered with a silicon-hydride mono-layer). The HF last process is known in the art and may be implemented in a horizontally-oriented wet processing chamber, such as an IBC chamber (described above in conjunction with  FIG. 3 ) or an electroless deposition chamber (described above in conjunction with  FIG. 7 ). The HF last process may also be carried out in a vertically aligned wet clean chamber, such as a vapor dryer chamber. In a preferred aspect, native oxide layer  2151  is selectively removed with little or no etching damage occurring to dielectric layer  2152 . In this aspect, a silicon hydride layer is formed by exposing native oxide layer  2151  to a solution containing an acid fluoride solution and an additive, such as ethanolamine (NH 2 (CH 2 ) 2 OH, also known as EA), diethanolamine (C 4 H 11 NO 2 , also known as DEA), or triethanolamine (C 4 H 5 HO 3 , also known as TEA). In general, one or more of these additives will tend to interact with the fluoride ions so that they become partially complexed and comparatively less active towards higher density silicon oxides, silicate, or silicon-containing materials on substrate  2153 , such as dielectric layer  2152 . One example of cleaning solution may be formed by mixing an aqueous solution containing a 1:1 solution of DEA and concentrated HF, having an adjusted pH of between about 4 and about 4.5. A more detailed description of solutions and methods of selectively removing native oxide from a silicon-based material is disclosed in commonly assigned U.S. Provisional Patent Application Ser. No. 60/731,624 [APPM10659L], entitled “Method of Selectively Depositing a Thin Film Material at a Semiconductor Interface,” filed Oct. 28, 2005, which is incorporated in its entirety to the extent not inconsistent with the present disclosure.  
      In another aspect, a plasma-assisted dry etch process is used, as described above in conjunction with  FIG. 20 . In a preferred aspect, the plasma-assisted dry etch process described above does not include a final substrate anneal step to sublimate the thin film of (NH 4 ) 2 SiF 6  into volatile SiF 4 , NH 3 , and HF products. Instead, the thin film of (NH 4 ) 2 SiF 6  is left on the surface of substrate  2153  which, upon contact with water, breaks down into a dilute HF solution, leaving a silicon hydride layer on silicon surface  2154 .  
      After the removal of native oxide layer  2151 , a cobalt and/or nickel layer is deposited onto silicon surface  2154  by a selective electroless deposition process as described above in conjunction with  FIG. 5C .  FIG. 21C  illustrates silicon contact  2150  after a metallic layer  2156  has been deposited therein. Metallic layer  2156  may consist of cobalt, nickel, or a combination thereof. It is important to note that a native oxide layer  2151  will quickly reform on silicon surface  2154  if silicon surface  2154  is exposed to air or other oxygen-containing gases. Depending on relative humidity, native oxide layer  2151  may be reformed in a matter of minutes or hours, therefore it is important to avoid exposure of silicon surface  2154  to oxygen, or, if such exposure is unavoidable, to limit the exposure time to a few minutes or seconds.  
      The selective electroless deposition process is generally a low-temperature, liquid phase reaction that deposits thin films of metal onto a hydride surface at ambient pressure and low temperature. The desired metal, such as cobalt or nickel, is selectively deposited onto silicon surface  2154  from a deposition solution since the film growth process involves a chemical reaction with a hydride surface bond, which is only present on silicon surface  2154 . The silylation reaction involves a solution phase-delivered metal complex that inserts itself between the silicon and hydrogen in the Si—H bond, creating two new bonds to the metal center and thereby increasing the oxidation state of the metal by two electrons. Therefore the deposited metal film is chemically bonded to the silicon surface. Exemplary solvents for the deposition solution may include acetonitrile or propylene glycol monomethyl ether. The complexed metal component(s) of the deposition solution is selected so that it will react with a silicon hydride bond. Exemplary metal complexes include cobalt tetracarbonyl, nickel dicyclooctadiene, and tungsten carbonyl. A more detailed description of a process for electroless deposition of a metal layer on a silicon surface is disclosed in previously referenced U.S. Provisional Patent Application Ser. No. 60/731,624 [APPM10659L], which is incorporated in its entirety to the extent not inconsistent with the present disclosure.  
      A rinsing and drying process may follow the electroless deposition process. In one aspect, a final drying process is carried out with a vapor dryer, as described above in conjunction with  FIG. 9 , to limit oxidation of the newly formed metal layer. To further limit oxidation of metallic layer  2156 , formation of a first stage silicide, described below in conjunction with  FIG. 21 D , should be performed as quickly as possible thereafter. Exposure of substrate  2153  to oxygen may be further limited by performing the electroless deposition and the first stage silicide formation in an oxygen-free atmosphere. Optimally, substrate  2153  is not exposed to oxygen between electroless deposition and silicide formation.  
      After deposition of metallic layer  2156 , a self-aligned, first stage silicide is formed by an anneal process, as illustrated in  FIG. 21D . When silicon contact  2150  is annealed to a sufficient temperature, atoms from metal layer  2156  diffuse into substrate  2153 , forming a second stage silicide region  2157  and leaving an excess metal layer  2156 A. For example, when metal layer  2156  is a nickel layer, annealing substrate  2153  at about 350° C. generates a Ni 2 Si region in substrate  2153  adjacent metal layer  2156 . Similarly, when metal layer  2156  is a cobalt layer, annealing substrate  2153  at about 450° C. generates a CoSi region in substrate  2153  adjacent metal layer  2156 .  
      After first stage anneal, an acid strip may be performed on substrate  2153  to remove excess metal layer  2156 A. The acid strip process is well known in the art and may be implemented in a horizontally-oriented wet processing chamber, such as an IBC chamber or an electroless deposition chamber.  FIG. 21E  illustrates silicon contact  2150  after an acid strip process has removed an excess metal layer therefrom.  
      For some metals the second stage anneal temperature is relatively low, ie., about 450° C. to about 550° C., allowing a second stage anneal to be performed on cluster tool  200 . Nickel is one such metal. Referring to  FIG. 21F , a second stage anneal of substrate  2153  forms a second stage silicide region  2157 A, which in the case of nickel, consists of NiSi.  
      2. General Description of Cluster Tool Configuration  
      In this embodiment, cluster tool  200  is configured generally the same as the electroless deposition platform with brush box and vapor dryer, described above in conjunction with  FIG. 11 , except that no processing station is configured as a brush box. Referring to  FIG. 11 , wet processing chambers are preferably positioned on wet processing platform  213  and dry processing stations are preferably positioned in factory interface  230  of the cluster tool  200 . For this embodiment, wet processing chambers may include a combined SC-1 and native oxide wet clean chamber, an electroless deposition chamber, an SRD or vapor dryer chamber, and in some configurations an acid strip chamber. Dry processing chambers may include a plasma-assisted dry etch chamber for native oxide removal, a supercritical clean chamber, and an anneal chamber. A vertically oriented vapor dryer chamber, i.e., a “dip tank” style solvent dry chamber, is a preferred chamber for rinsing and drying substrates after electroless deposition since oxidation of freshly deposited metal layers is minimized thereby. An exemplary vapor dryer that may be adapted for this configuration is described above in conjunction with  FIG. 9 .  
      In a preferred configuration, a dip tank style chamber performing SC-1 clean and native oxide wet clean is paired with an electroless deposition chamber inside an environmentally controlled enclosure, such as processing enclosure  302 , described above in conjunction with  FIG. 6 . In this configuration, a substrate may undergo electroless deposition immediately after removal of native oxide from a silicon-based surface on said substrate. Referring to  FIG. 11 , processing enclosure  302  may contain processing stations  210 ,  212  configured as a wet clean chamber (for a combined SC-1 clean and native oxide wet clean) and as an electroless deposition chamber, respectively.  
      In another aspect, native oxide is removed from a substrate in a plasma-assisted dry etch chamber. In one configuration, the plasma-assisted dry etch chamber is positioned in factory interface  230 . Because configuring factory interface  230  to maintain an oxygen-free environment is problematic, some exposure to oxygen may take place after the native oxide removal process when the plasma-assisted dry etch chamber is positioned in factory interface  230 . But because the staging of substrates between the dry etch chamber and an electroless deposition chamber may be controlled so that queue time in air is limited to a matter of seconds, re-oxidation of substrates is minimized. Further, the duration of oxygen exposure for each substrate processing in cluster tool  200  may be substantially the same, minimizing process variation associated with substrates having significantly different exposure times. Substrate staging to limit queue time in air is described in detail below in conjunction with  FIG. 22 . It is important to note that when native oxide removal and electroless deposition are performed on different processing systems, significant oxidation prior to electroless deposition is unavoidable. In another configuration, a processing station contained in a processing enclosure may be configured as the plasma-assisted dry etch chamber, such as processing station  210  in processing enclosure  302 . As in the preferred configuration, processing station  212  is configured as an electroless deposition chamber, so that no air exposure is necessary when transferring a substrate between the plasma-assisted dry etch chamber and the electroless deposition chamber.  
      In a preferred aspect, multiple electroless deposition chambers are contained in wet processing platform  213  and are each paired with a native oxide removal chamber inside a processing enclosure. For example, processing stations  202 ,  204  may make up one such chamber pair, processing stations  206 ,  208  a second, and processing stations  210 ,  212  a third. Processing stations  214 ,  216  are configured as SRD chambers or vapor dryer chambers. A running beam  250  and a flipper robot  251  (described above in conjunction with  FIG. 9A ) may be positioned in wet processing platform  213  to enable transferal of substrates between vapor dryer or native oxide clean chambers (configured as vertically oriented dip tanks) and horizontally oriented processing chambers, such as electroless deposition chambers.  
      3. Process Sequence  
      An exemplary substrate process sequence  2200  for forming a silicide on a silicon contact is detailed in the flow chart illustrated in  FIG. 22 .  
      In step  2201 , organic contamination may be removed from the surface of a substrate, such as substrate  2153 , illustrated in  FIG. 21A . In one aspect, an SC-1 clean process is used and may be carried out in a horizontally or vertically oriented wet processing chamber positioned on wet processing platform  213 , which is illustrated in  FIG. 11A . Wet processing chambers capable of this process step include SRD, IBC, electroless deposition, and vapor dryer chambers. In another aspect, organic contamination is removed by the application of a supercritical fluid, wherein the supercritical clean chamber is positioned on cluster tool  200  in factory interface  230 .  
      In step  2202 , native oxide formed on silicon contacts, such as native oxide layer  2151 , is removed from a substrate prior to electroless metal deposition. In a preferred aspect, native oxide is removed by the HF-based wet cleaning process described above in conjunction with  FIG. 21B . In this aspect, step  2202  is performed in the same wet processing chamber as step  2201 . In addition to requiring fewer chambers, native oxide removal can take place immediately after organic contamination removal, minimizing the possibility of recontamination between process steps. Such a dual-use cleaning chamber may be a horizontally oriented wet processing chamber, such as an IBC chamber, or it may be a vertically oriented chamber, such as a vapor dryer chamber. In another aspect, native oxide is removed in a plasma-assisted dry etch chamber, which is a separate chamber from the SC-1 clean chamber.  
      In step  2203 , a metal layer is selectively deposited on the silicon hydride layer of the oxide-free contact by an electroless process, as described above in conjunction with  FIG. 21C . In a preferred aspect, a pre-clean chamber (which is adapted to perform SC-1 and native oxide cleans) is paired with an electroless deposition chamber. Both processing chambers are contained in an environmentally controlled enclosure to prevent oxidation of the silicon contact prior to deposition, allowing formation of a high quality, contact level connection to devices formed on the silicon-based substrate with an electroless silicide process. Because the silicon hydride layer formed on the substrate prior to metal deposition is so easily oxidized, the pairing of a pre-clean chamber with an electroless deposition chamber inside an oxygen-free environment eliminates any queue time issues associated with this silicide formation process; in a nitrogen-purged environment, more than 10 minutes are required for significant oxide re-growth. In another aspect, a plasma-assisted dry etch chamber is paired with an electroless deposition chamber in an environmentally controlled enclosure. In yet another aspect, a plasma-assisted dry etch chamber is not positioned in the same enclosure as the electroless deposition chamber, but is instead located in the factory interface  230 . In this aspect, queue time for substrates may be controlled to minimize oxidation. For example, after step  2202 , a substrate may be held inside the oxygen-free environment of the plasma-assisted dry etch chamber until an electroless deposition chamber is available. The substrate may be then be transferred directly from one oxygen-free environment to another, minimizing unwanted oxidation by exposing the substrate to air for only a few seconds.  
      In step  2204 , a first stage silicide is formed via an anneal process. The anneal process is performed in an anneal chamber, an example of which is described below in conjunction with  FIG. 23 . The anneal chamber may be positioned in factory interface  230  of cluster tool  200 , for example in processing stations  235  and/or  235   a . Because the anneal process for producing a first stage silicide is relatively time-consuming, multiple anneal chambers may be positioned in factory interface  230  so that system throughput is not reduced. In one example, multiple anneal chambers are vertically stacked in processing station  235 . It is important to note that until the first stage silicide is formed, the freshly deposited metal layer is easily oxidized. Because all processing chambers for the silicide formation process are positioned on the same platform, i.e., cluster tool  200 , queue time, and therefore oxygen exposure, is controllable for substrates that are between step  2203  (metal deposition) and step  2204  (silicide formation). Substrates may be staged in the manner described above in step  2203 . For example, if an anneal chamber is not available for processing when a substrate completes step  2203 , the substrate may be held in the oxygen-free environment of the electroless deposition chamber until an anneal chamber is available.  
      In step  2205 , an acid strip process may remove any excess metal remaining in the silicon contacts of a substrate. Step  2205  may be performed in a number of wet processing chambers contained in cluster tool  200 , including IBC and electroless deposition chambers. In a preferred aspect, a dedicated chamber is used for the acid strip process to minimize impact on throughput.  
      In step  2206 , a second stage silicide may be formed for some metals in the same anneal chamber used in step  2204  to form the first stage silicide. This is the case for nickel. For metals requiring higher temperatures than about 600° C. for forming a second stage silicidation, step  2206  is typically performed on a separate substrate processing system, such as a rapid thermal processing (RTP) system.  
      4. Description of Anneal Chamber  
      Embodiments of the invention include the incorporation of multiple substrate processing chambers onto a single cluster tool to enable a silcidation process to be performed on source and drain gates with short and controlled queue times and without unwanted oxidation taking place between steps in the silicidation process. Chambers required for the silicidation process include one or more pre-clean chambers (supercritical clean, plasma-assisted dry etch, vapor dryer, or IBC), an electroless deposition chamber, and an anneal chamber. Optionally, an acid strip chamber may also be included. Examples of most of these chambers and the processes performed on substrates therein have been described previously. A general description of an exemplary anneal chamber is provided below.  
       FIG. 23  illustrates a top perspective view of an exemplary annealing chamber  2399  of the invention with the cover or lid portion of the chamber removed so that the internal components are visible. The annealing chamber  2399  generally includes a chamber body  2301  that defines an enclosed processing volume  2300 . The enclosed processing volume  2300  includes a heating plate  2302  and a cooling plate  2304  positioned therein proximate each other. A substrate transfer mechanism  2306  is positioned adjacent the heating and cooling plates and is configured to receive a substrate from outside the processing volume  2300  and transfer the substrate between the respective heating and cooling plates during an annealing process. The substrate transfer mechanism  2306  generally includes pivotally mounted robot assembly having a substrate support member/blade  2308  positioned at a distal end of a pivotal arm of the robot. The blade  2308  includes a plurality of substrate support tabs  2310  that are spaced from the blade  2308  and configured to cooperatively support a substrate thereon. Each of the support tabs  2310  are generally spaced vertically (generally downward) from a main body portion  2308  of the blade, which generates a vertical space between blade  2308  and tabs  2310 . This spacing allows for a substrate to be positioned on the tabs  2310  during a substrate loading process.  
      The chamber body  2301  of the annealing chamber, which may be manufactured from aluminum, for example, generally defines an interior processing volume  2300 . Chamber body  2301  generally includes a plurality of fluid conduits (not shown) formed therethrough, wherein the fluid conduits are configured to circulate a cooling fluid to reduce the temperature of the chamber body  2301 . The cooling fluid may be supplied to the fluid conduits formed into the chamber body  2301  and circulated through the chamber body  2301  by cooling fluid connections (not shown)  
      The cooling plate  2304  generally includes a substantially planar upper surface configured to support a substrate thereon. The upper surface includes a plurality of vacuum apertures  2322 , which are selectively in fluid communication with a vacuum source (not shown) and may generally be used to generate a reduced pressure in order to secure or vacuum chuck a substrate to the upper surface of cooling plate  2304 . The interior portion of the cooling plate may include a plurality of fluid conduits formed therein, wherein the fluid conduits are in fluid communication with the cooling fluid source used to cool the chamber body  2301 . The cooling plate may be used to rapidly cool a substrate positioned thereon.  
      The heating plate  2302 , in similar fashion to the cooling plate  404 , also includes a substantially planar upper substrate support surface. The substrate support surface includes a plurality a vacuum apertures  2322  formed therein, each of the vacuum apertures  2322  being selectively in fluid communication with a vacuum source (not shown)and may be used to vacuum chuck or secure a substrate to the heating plate  2302  for processing. The interior of the heating plate  2302  includes a heating element (not shown), wherein the heating element is configured to heat the surface of the heating plate  2302  to a temperature of between about 100° C. to about 500° C. Additionally, one or more of the vacuum apertures  2322  may also be in fluid communication with a heated gas supply, and as such, one or more of the apertures may be used to dispense a heated gas onto the backside of the substrate during processing.  
      The annealing chamber may include a pump down aperture  2324  positioned in fluid communication with the processing volume  2300 . The pump down aperture  2324  is selectively in fluid communication with a vacuum source (not shown) and is generally configured to evacuate gases from the processing volume  2300 . Additionally, the annealing chamber generally includes at least one gas dispensing port  2326  or gas dispensing showerhead positioned proximate the heating plate  2302 . The gas dispensing port is selectively in fluid communication with a processing gas source and is configured to dispense a processing gas into the processing volume  2300 . The vacuum pump down aperture  2324  and the gas dispensing nozzle may be utilized cooperatively or separately to minimize ambient gas content in the annealing chamber, i.e., both of the components or one or the other of the components may be used.  
      In operation, once a substrate is transferred into annealing chamber  2399  and is supported by the tabs  2310 , the external robot blade  2312  may be retracted from the processing volume  2300  and the access door  2314  may be closed to isolate the processing volume  2300  from ambient atmosphere. In this example, once the door  2314  is closed, a vacuum source in communication with the pump down aperture  2324  may be activated and caused to pump a portion of the gases from the processing volume  2300 . During the pumping process, or shortly thereafter, the gas dispensing port  2326  may be opened to allow the processing gas to flood the processing volume  2300 . The process gas is generally an inert gas that is known not to react under the annealing processing conditions. This configuration, i.e., the pump down and inert gas flooding process, is generally configured to remove as much of the oxygen from the annealing chamber/processing volume as possible, as the oxygen is known to cause oxidation to the substrate surface during the annealing process. The vacuum source may be terminated and the gas flow stopped when the chamber reaches a predetermined pressure and gas concentration, or alternatively, the vacuum source may remain activated during the annealing process and the gas delivery nozzle may continue to flow the processing gas into the processing volume.  
      While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.