Patent Publication Number: US-2010126849-A1

Title: Apparatus and method for forming 3d nanostructure electrode for electrochemical battery and capacitor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 61/117,535 (Attorney Docket No. 12922L), filed Nov. 24, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to apparatus and methods of forming an electrochemical battery or capacitor. Particularly, embodiments of the present invention relates to apparatus and methods for forming electrochemical batteries or capacitors having electrodes with 3D nanostructure. 
     2. Description of the Related Art 
     Electrical energy can generally be stored in two fundamentally different ways: 1) indirectly in batteries as potential energy available as chemical energy that requires oxidation and reduction of active species, or 2) directly, using electrostatic charge formed on the plates of a capacitor. Typically, ordinary capacitors store a small amount of charge due to their size and thus only store a small amount of electrical energy. Energy storage in conventional capacitors is generally non-Faradaic, meaning that no electron transfer takes place across an electrode interface, and the storage of electric charge and energy is electrostatic. 
     In an effort to form an effective electrical energy storage device that can store sufficient charge to be useful as independent power sources, or supplemental power source for a broad spectrum of portable electronic equipment and electric vehicles, devices known as electrochemical capacitors have been created. Electrochemical capacitors are energy storage devices which combine some aspects of the high energy storage potential of batteries with the high energy transfer rate and high recharging capabilities of capacitors. 
     The term electrochemical capacitor is sometimes described in the art as a super-capacitor, electrical double-layer capacitors, or ultra-capacitor. Electrochemical capacitors can have hundreds of times more energy density than conventional capacitors and thousands of times higher power density than batteries. It should be noted that energy storage in electrochemical capacitors can be both Faradaic or non-Faradaic. 
     In both the Faradaic electrochemical capacitors and non-Faradaic electrochemical capacitors, capacitance is highly dependent on the characteristics of the electrode and electrode material. Ideally, the electrode material should be electrically conducting and have a large surface area. Typically, the electrode material will be formed from porous structures to enable the formation of a large surface area that can be used either for the development of the electrical double layer for static charge storage to provide non-Faradaic capacitance or for the reversible chemical redox reaction sites to provide Faradaic capacitance. 
     An electrochemical battery is a device that converts chemical energy into electrical energy. An electrochemical battery typically consists of a group of electric cells that are connected to act as a source of direct current. 
     Generally, an electric cell consists of two dissimilar substances, a positive electrode and a negative electrode, and a third substance, an electrolyte. The positive and negative electrodes conduct electricity. The electrolyte acts chemically on the electrodes. The two electrodes are connected by an external circuit, such as a piece of copper wire. 
     The electrolyte functions as an ionic conductor for the transfer of the electrons between the electrodes. The voltage, or electromotive force, depends on the chemical properties of the substances used, but is not affected by the size of the electrodes or the amount of electrolyte. 
     Electrochemical batteries are classed as either dry cell or wet cell. In a dry cell, the electrolyte is absorbed in a porous medium, or is otherwise restrained from flowing. In a wet cell, the electrolyte is in liquid form and free to flow and move. Batteries also can be generally divided into two main types—rechargeable and nonrechargeable, or disposable. 
     Disposable batteries, also called primary cells, can be used until the chemical changes that induce the electrical current supply are complete, at which point the battery is discarded. Disposable batteries are most commonly used in smaller, portable devices that are only used intermittently or at a large distance from an alternative power source or have a low current drain. 
     Rechargeable batteries, also called secondary cells, can be reused after being drained. This is done by applying an external electrical current, which causes the chemical changes that occur in use to be reversed. The external devices that supply the appropriate current are called chargers or rechargers. 
     Rechargeable batteries are sometimes known as storage batteries. A storage battery is generally of the wet-cell type using a liquid electrolyte and can be recharged many times. The storage battery consists of several cells connected in series. Each cell contains a number of alternately positive and negative plates separated by the liquid electrolyte. The positive plates of the cell are connected to form the positive electrode and the negative plates form the negative electrode. 
     In the process of charging, each cell is made to operate in reverse of its discharging operation. During charging, current is forced through the cell in the opposite direction as during discharging, causing the reverse of the chemical reaction that ordinarily takes place during discharge. Electrical energy is converted into stored chemical energy during charging. 
     The storage battery&#39;s greatest use has been in the automobile where it was used to start the internal-combustion engine. Improvements in battery technology have resulted in vehicles in which the battery system supplies power to electric drive motors instead. 
     To make electrochemical batteries or capacitors more of a viable product, it is important to reduce the costs to produce the electrochemical batteries or capacitors, and improve the efficiency of the formed electrochemical battery or capacitor device. 
     Therefore, there is a need for method and apparatus for forming electrodes of electrochemical batteries or capacitors that have an improved lifetime, improved deposited film properties, and reduced production cost. 
     SUMMARY OF THE INVENTION 
     Embodiments described herein generally relate to an electrochemical battery and capacitor electrode structure, particularly, apparatus and methods of creating a reliable and cost efficient electrochemical battery and capacitor electrode structure that has an improved lifetime, lower production costs, and improved process performance. 
     One embodiment of the present invention provides an apparatus for plating a metal on a large area substrate comprising a chamber body defining a processing volume, wherein the processing volume is configured to retain a plating bath therein, and the chamber body has an upper opening, a plurality of jet sprays configured to dispend a plating solution to form the plating bath in the processing volume, wherein the plurality of jet sprays open to a side wall of the chamber body, a draining system configured to drain the plating bath from the processing volume, an anode assembly disposed in the processing volume, wherein the anode assembly comprises an anode emerged in the plating bath in a substantially vertical position, and a cathode assembly disposed in the processing volume, and the cathode assembly comprises a substrate handler configured position one or more large area substrates in a substantially vertical position and substantially parallel to the anode the processing volume, and a contacting mechanism configured to couple an electric bias to the one or more large area substrates. 
     Another embodiment of the present invention provides a substrate processing system comprising a pre-wetting chamber configured to clean a seed layer of a large area substrate, a first plating chamber configured to form a columnar layer of a first metal on the seed layer of the large area substrate, a second plating chamber configured to form a porous layer over the columnar layer, a rinse dry chamber configured to clean and dry the large are substrate, and a substrate transfer mechanism configured to transfer the large area substrate among the chambers, wherein each of the first and second plating chamber comprises a chamber body defining a processing volume, wherein the processing volume is configured to retain a plating bath therein, and the chamber body has an upper opening, a draining system configured to drain the plating bath from the processing volume, an anode assembly disposed in the processing volume, wherein the anode assembly comprises an anode emerged in the plating bath, and a cathode assembly disposed in the processing volume, and the cathode assembly comprises, a substrate handler configured position one or more large area substrates substantially parallel to the anode the processing volume, and a contacting mechanism configured to couple an electric bias to the one or more large area substrates. 
    
    
     
       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  is a simplified schematic view of an active region of an electrochemical capacitor unit. 
         FIG. 1B  is a simplified schematic view a lithium-ion battery cell. 
         FIG. 2  is a flow diagram of a method for forming an electrode in accordance with embodiments described herein. 
         FIG. 3  is a schematic cross-sectional view showing formation an anode according to embodiments of the present invention. 
         FIG. 4  is a flow diagram of a method for forming a porous electrode in accordance with embodiments described herein. 
         FIG. 5A  is a schematic sectional side view of a plating chamber in accordance with one embodiment of the present invention. 
         FIG. 5B  is a schematic sectional side view of the plating chamber of  FIG. 5A  in a substrate transferring position. 
         FIG. 5C  schematically illustrates a plating system using one or more plating chambers of  FIG. 5A . 
         FIG. 6A  is a schematic sectional side view of a plating chamber in accordance with one embodiment of the present invention. 
         FIG. 6B  a schematic sectional side view of a plating chamber in accordance with one embodiment of the present invention 
         FIG. 6C  schematically illustrates a plating system using one or more plating chambers of  FIG. 6A . 
         FIG. 7A  is a schematic perspective view of a plating chamber in accordance with one embodiment of the present invention. 
         FIG. 7B  is a schematic sectional side view of the plating chamber of  FIG. 7A  in plating position. 
         FIG. 7C  is a schematic view of a substrate holder in accordance with one embodiment of the present invention. 
         FIGS. 8A-8B  schematically illustrate a processing system in accordance with one embodiment of the present invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. It is contemplated that elements and/or process steps of one embodiment may be beneficially incorporated in other embodiments without additional recitation 
     DETAILED DESCRIPTION 
     Embodiments described herein generally relate to an electrode structure, particularly for an electrochemical battery or capacitor, apparatus and methods of creating a reliable and cost efficient electrochemical battery or capacitor electrode structure that has an improved lifetime, lower production costs, and improved process performance. One embodiment provides a substrate plating system comprising a first plating chamber configure to form a columnar structure on a seed layer of a substrate, and a second plating chamber configured to form a porous layer on the columnar structure. One embodiment provides a plating chamber configured to plate one or more large area substrate. In one embodiment, the plating chamber comprises a feed roll, a bottom roll and a take up roll configured to position large area substrates formed in a continuous flexible base in a processing volume, and to transfer the large area substrates in and out the processing volume. In another embodiment, the plating chamber comprises a substrate holder movably disposed in a processing volume and configured to hold one or more large area substrate, and to transfer the one or more large area substrates in and out the processing volume. 
     In an effort to achieve high plating rates and achieve desirable plated film properties, it is often desirable to increase the concentration of metal ions near the cathode (e.g., seed layer surface) by reducing the diffusion boundary layer or by increasing the metal ion concentration in the electrolyte bath. It should be noted that the diffusion boundary layer is strongly related to the hydrodynamic boundary layer. If the metal ion concentration is too low and/or the diffusion boundary layer is too large at a desired plating rate the limiting current (i L ) will be reached. The diffusion limited plating process created when the limiting current is reached, prevents the increase in plating rate by the application of more power (e.g., voltage) to the cathode (e.g., metallized substrate surface). When the limiting current is reached a low density columnar film is produced due to the evolution of gas and resulting dendritic type film growth that occurs due to the mass transport limited process. 
       FIG. 1A  illustrates a simplified schematic view of an active region  140  of an electrochemical capacitor unit  100  that can be powered by use of a power source  160 . An electrochemical capacitor unit  100  can be of any shape, e.g., circular, square, rectangle, polygonal, and size. The active region  140  generally contains a membrane  110 , porous electrodes  120  formed according to embodiments described herein, charge collector plates  150  and an electrolyte  130  that is in contact with the porous electrodes  120 , charge collector plates  150  and membrane  110 . The electrically conductive charge collector plates  150  sandwich the porous electrodes  120  and membrane  110 . 
     The electrolyte  130  that is contained between the charge collector plates  150  generally provides a charge reservoir for the electrochemical capacitor unit  100 . The electrolyte  130  can be a solid or a fluid material that has a desirable electrical resistance and properties to achieve desirable charge or discharge properties of the formed device. If the electrolyte is a fluid, the electrolyte enters the pores of the electrode material and provides the ionic charge carriers for charge storage. A fluid electrolyte requires that a membrane  110  be non-conducting to prevent shorting of the charge collected on either of the charge collector plates  150 . 
     The membrane  110  is typically permeable to allow ion flow between the electrodes and is fluid permeable. Examples of non-conducting permeable separator material are porous hydrophilic polyethylene, polypropylene, fiberglass mats, and porous glass paper. The membrane  110  can be made from an ion exchange resin material, polymeric material, or a porous inorganic support. For example, three layers of polyolefin, three layers of polyolefin with ceramic particles, an ionic perfluoronated sulfonic acid polymer membrane, such as Nafion™, available from the E.I. DuPont de Nemeours &amp; Co. Other suitable membrane materials include Gore Select™, sulphonated fluorocarbon polymers, the polybenzimidazole (PBI) membrane (available from Celanese Chemicals, Dallas, Tex.), polyether ether ketone (PEEK) membranes and other materials. 
     The porous electrodes  120  generally contain a conductive material that has a large surface area and has a desirable pore distribution to allow the electrolyte  130  to permeate the structure. The porous electrodes  120  generally require a large surface area to provide an area to form a double-layer and/or an area to allow a reaction between the solid porous electrode material and the electrolyte components, such as pseudo-capacitance type capacitors. The porous electrodes  120  can be formed from various metals, plastics, glass materials, graphites, or other suitable materials. In one embodiment, the porous electrode  120  is made of any conductive material, such as a metal, plastic, graphite, polymers, carbon-containing polymer, composite, or other suitable materials. More specifically, the porous electrode  120  may comprise copper, aluminum, zinc, nickel, cobalt, palladium, platinum, tin, ruthenium, stainless steel, titanium, lithium, alloys thereof, and combinations thereof. 
     Embodiments described herein, generally contain various apparatus and methods for increasing the surface area of an electrode by three-dimensional growth of electrode material. Advantageously, the increased surface area of the porous three-dimensional electrode provides increased capacitance with improved cycling, rapid charging using the high conductivity three-dimensional nanomaterial, and large energy and power densities. 
     In one embodiment, three dimensional growth of electrode material is performed using a high plating rate electroplating process performed at current densities above the limiting current (i L ). In one embodiment, a columnar metal layer is formed at a first current density by a diffusion limited deposition process followed by the three dimensional growth of electrode material at a second current density greater than the first current density. The resulting electrode structure has an improved lifetime, lower production cost, and improved process performance. 
       FIG. 2B  is a simplified schematic view of a lithium-ion battery cell  158 . Lithium-ion batteries are a type of electrochemical batteries. A plurality of lithium-ion battery cells  150  can be assembled together when in use. The lithium-ion battery cell  150  comprises an anode  151 , and a cathode  152 , a separator  153 , and an electrolyte  154  that is in contact with the anode  151 , the cathode  152 , the separator  153 , and an electrolyte  154  disposed between the anode  151  and the cathode  152 . 
     Both the anode  151  and the cathode  152  comprise materials into which and from which lithium can migrate. The process of lithium moving into the anode  151  or cathode  152  is referred to as insertion or intercalation. The reverse process, in which lithium moves out of the anode  151  or cathode  152  is referred to as extraction or deintercalation. When the lithium-ion battery cell  150  is discharging, lithium is extracted from the anode  151  and inserted into the cathode  152 . When the lithium-ion battery cell  150  is charging, lithium is extracted from the cathode  152  and inserted into the anode  151 . 
     The anode  151  is configured to store lithium ions  155 . The anode  151  may be formed from carbon containing material or metallic material. The anode  151  may comprise oxides, phosphates, fluorophosphates, or silicates. 
     The cathode  152  may be made from a layered oxide, such as lithium cobalt oxide, a polyanion, such as lithium iron phosphate, a spinel, such as lithium manganese oxide, or TiS 2  (titanium disulfide). Exemplary oxides may be layered lithium cobalt oxide, or mixed metal oxide, such as LiNi x Co 1-2x MnO 2 , LiMn 2 O 4 . Li It is desirable that the anode  151  has a large surface area. Exemplary phosphates may be iron olivine (LiFePO 4 ) and it is variants (such as LiFe1- x MgPO 4 ), LiMoPO4, LiCoPO 4 , Li 3 V 2 (PO 4 ) 3 , LiVOPO 4 , LiMP 2 O 7 , or LiFe 1.5 P 2 O 7 . Exemplary fluorophosphates may be LiVPO 4 F, LiAlPO 4 F, Li 5 V(PO 4 ) 2 F 2 , Li 5 Cr(PO 4 ) 2 F 2 , Li 2 CoPO 4 F, Li 2 NiPO 4 F, or Na 5 V 2 (PO 4 ) 2 F 3 . Exemplary silicates may be Li 2 FeSiO 4 , Li 2 MnSiO 4 , or Li 2 VOSiO 4 . 
     The separator  153  is configured to supply ion channels for in movement between the anode  151  and the cathode  152  while keeping the anode  151  and the cathode  152  physically separated to avoid a short. The separator  153  may be solid polymer, such as polyethyleneoxide (PEO). 
     The electrolyte  154  is generally a solution of lithium salts such as LiPF 6 , LiBF 4 , or LiClO 4 , in an organic solvents. 
     When the lithium-ion battery cell  150  discharges, lithium ions  155  moves from the anode  151  to the cathode  152  providing a current to power a load  156  connected between the anode  151  and the cathode  152 . When the lithium-ion battery cell  150  is depleted, a charger  157  may be connected between the anode  151  and the cathode  152  providing a current to drive the lithium ions  155  to the anode  151 . Since the amount of energy stored in the lithium-ion battery cell  150  defends on the amount of lithium ion  155  stored in the anode  151 , it is desirable to have as large a surface area on the anode  151  as possible. Embodiments of the present invention described below provide methods and apparatus for producing electrodes with increased surface area. 
       FIG. 2  is a flow diagram according to one embodiment described herein of a process  200  for forming an electrode in accordance with embodiments described herein.  FIG. 3  is a schematic cross-sectional view of an electrode formed according to embodiments described herein. The process  200  includes process steps  202 - 212 , wherein an electrode is formed on a substrate  220 . The process  200  may be performed with systems in accordance to embodiments of the present invention. 
     The first process step  202  includes providing the substrate  220 . The substrate  220  may comprise a material selected from the group comprising copper, aluminum, nickel, zinc, tin, flexible materials, stainless steel, and combinations thereof. Flexible substrates can be constructed from polymeric materials, such as a polyimide (e.g., KAPTON™ by DuPont Corporation), polyethyleneterephthalate (PET), polyacrylates, polycarbonate, silicone, epoxy resins, silicone-functionalized epoxy resins, polyester (e.g., MYLAR™ by E.I. du Pont de Nemours &amp; Co.), APICAL AV manufactured by Kanegaftigi Chemical Industry Company, UPILEX manufactured by UBE Industries, Ltd.; polyethersulfones (PES) manufactured by Sumitomo, a polyetherimide (e.g., ULTEM by General Electric Company), and polyethylenenaphthalene (PEN). In some cases the substrate can be constructed from a metal foil, such as stainless steel that has an insulating coating disposed thereon. Alternately, flexible substrate can be constructed from a relatively thin glass that is reinforced with a polymeric coating. 
     The second process step  204  includes optionally depositing a barrier layer over the substrate. The barrier layer  222  may be deposited to prevent or inhibit diffusion of subsequently deposited materials over the barrier layer into the underlying substrate. Examples of barrier layer materials include refractory metals and refractory metal nitrides such as tantalum (Ta), tantalum nitride (TaN x ), titanium (Ti), titanium nitride (TiN x ), tungsten (W), tungsten nitride (WN x ), and combinations thereof. Other examples of barrier layer materials include PVD titanium stuffed with nitrogen, doped silicon, aluminum, aluminum oxides, titanium silicon nitride, tungsten silicon nitride, and combinations thereof. Exemplary barrier layers and barrier layer deposition techniques are further described in U.S. Patent Application Publication 2003/0143837 entitled “Method of Depositing A Catalytic Seed Layer,” filed on Jan. 28, 2002, which is incorporated herein by reference to the extent not inconsistent with the embodiments described herein. 
     The barrier layer may be deposited by CVD, PVD, electroless deposition techniques, evaporation, or molecular beam epitaxy. The barrier layer may also be a multi-layered film deposited individually or sequentially by the same or by a combination of techniques. 
     The third process step  206  includes optionally depositing a seed layer  224  over the substrate  220 . The seed layer  224  comprises a conductive metal that aids in subsequent deposition of materials thereover. The seed layer  224  preferably comprises a copper seed layer or alloys thereof. Other metals, particularly noble metals, may also be used for the seed layer. The seed layer  224  may be deposited over the barrier layer by techniques conventionally known in the art including physical vapor deposition techniques, chemical vapor deposition techniques, evaporation, and electroless deposition techniques. 
     The fourth process step  208  includes forming a columnar metal layer  226  over the seed layer  224 . Formation of the columnar metal layer  226  includes establishing process conditions under which evolution of hydrogen results in the formation of a porous metal film. Formation of the columnar metal layer  226  generally takes place in a plating chamber using a suitable plating solution. Suitable plating solutions that may be used with the processes described herein to plate copper may include at least one copper source compound, at least one acid based electrolyte, and optional additives. 
     The plating solution contains at least one copper source compound complexed or chelated with at least one of a variety of ligands. Complexed copper includes a copper atom in the nucleus and surrounded by ligands, functional groups, molecules or ions with a strong finite to the copper, as opposed to free copper ions with very low finite, if any, to a ligand, such as water. Complexed copper sources are either chelated before being added to the plating solution, such as copper citrate, or are formed in situ by combining a free copper ion source such as copper sulfate with a complexing agent, such as citric acid or sodium citrate. The copper atom may be in any oxidation state, such as 0, 1 or 2, before, during or after complexing with a ligand. Therefore, throughout the disclosure, the use of the word copper or elemental symbol Cu includes the use of copper metal (Cu 0 ), cupric (Cu +1 ) or cuprous (Cu +2 ), unless otherwise distinguished or noted. 
     Examples of suitable copper source compounds include copper sulfate, copper phosphate, copper nitrate, copper citrate, copper tartrate, copper oxalate, copper EDTA, copper acetate, copper pyrophosphorate and combinations thereof, preferably copper sulfate and/or copper citrate. A particular copper source compound may have ligated varieties. For example, copper citrate may include at least one cupric atom, cuprous atom or combinations thereof and at least one citrate ligand and include Cu(C 6 H 7 O 7 ), Cu 2 (C 6 H 4 O 7 ), Cu 3 (C 6 H 5 O 7 ) or Cu(C 6 H 7 O 7 ) 2 . In another example, copper EDTA may include at least one cupric atom, cuprous atom or combinations thereof and at least one EDTA ligand and include Cu(C 10 H 15 O 8 N 2 ), Cu 2 (C 10 H 14 O 8 N 2 ), Cu 3 (C 10 H 13 O 8 N 2 ), Cu 4 (C 10 H 12 O 8 N 2 ), Cu(C 10 H 14 O 8 N 2 ) or Cu 2 (C 10 H 12 O 8 N 2 ). The plating solution may include one or more copper source compounds or complexed metal compounds at a concentration in the range from about 0.02 M to about 0.8 M, preferably in the range from about 0.1 M to about 0.5 M. For example, about 0.25 M of copper sulfate may be used as a copper source compound. 
     Examples of suitable tin source may be soluble tin compound. A soluble tin compound can be a stannic or stannous salt. The stannic or stannous salt can be a sulfate, an alkane sulfonate, or an alkanol sulfonate. For example, the bath soluble tin compound can be one or more stannous alkane sulfonates of the formula: 
       (RSO 3 ) 2 Sn 
     where R is an alkyl group that includes from one to twelve carbon atoms. The stannous alkane sulfonate can be stannous methane sulfonate with the formula: 
     
       
         
         
             
             
         
       
     
     The bath soluble tin compound can also be stannous sulfate of the formula: SnSO 4    
     Examples of the soluble tin compound can also include tin(II) salts of organic sulfonic acid such as methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, p-phenolsulfonic acid and like, tin(II) borofluoride, tin(II) sulfosuccinate, tin(II) sulfate, tin(II) oxide, tin(II) chloride and the like. These soluble tin(II) compounds may be used alone or in combination of two or more kinds. 
     Example of suitable cobalt source may include cobalt salt selected from cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt bromide, cobalt carbonate, cobalt acetate, ethylene diamine tetraacetic acid cobalt, cobalt (II) acetyl acetonate, cobalt (III) acetyl acetonate, glycine cobalt (III), and cobalt pyrophosphate, or combinations thereof. 
     In one embodiment, the plating solution contains free copper ions in place of copper source compounds and complexed copper ions. 
     The plating solution may contain at least one or more acid based electrolytes. Suitable acid based electrolyte systems include, for example, sulfuric acid based electrolytes, phosphoric acid based electrolytes, perchloric acid based electrolytes, acetic acid based electrolytes, and combinations thereof. Suitable acid based electrolyte systems include an acid electrolyte, such as phosphoric acid and sulfuric acid, as well as acid electrolyte derivatives, including ammonium and potassium salts thereof. The acid based electrolyte system may also buffer the composition to maintain a desired pH level for processing a substrate. 
     Optionally, the plating solution may contain one or more chelating or complexing compounds and include compounds having one or more functional groups selected from the group of carboxylate groups, hydroxyl groups, alkoxyl, oxo acids groups, mixture of hydroxyl and carboxylate groups and combinations thereof. Examples of suitable chelating compounds having one or more carboxylate groups include citric acid, tartaric acid, pyrophosphoric acid, succinic acid, oxalic acid, and combinations thereof. Other suitable acids having one or more carboxylate groups include acetic acid, adipic acid, butyric acid, capric acid, caproic acid, caprylic acid, glutaric acid, glycolic acid, formic acid, fumaric acid, lactic acid, lauric acid, malic acid, maleic acid, malonic acid, myristic acid, plamitic acid, phthalic acid, propionic acid, pyruvic acid, stearic acid, valeric acid, quinaldine acid, glycine, anthranilic acid, phenylalanine and combinations thereof. Further examples of suitable chelating compounds include compounds having one or more amine and amide functional groups, such as ethylenediamine, diethylenetriamine, diethylenetriamine derivatives, hexadiamine, amino acids, ethylenediaminetetraacetic acid, methylformamide or combinations thereof. The plating solution may include one or more chelating agents at a concentration in the range from about 0.02 M to about 1.6 M, preferably in the range from about 0.2 M to about 1.0 M. For example, about 0.5 M of citric acid may be used as a chelating agent. 
     The one or more chelating compounds may also include salts of the chelating compounds described herein, such as lithium, sodium, potassium, cesium, calcium, magnesium, ammonium and combinations thereof. The salts of chelating compounds may completely or only partially contain the aforementioned cations (e.g., sodium) as well as acidic protons, such as Na x (C 6 H 8-x O 7 ) or Na x EDTA, whereas X=1-4. Such salt combines with a copper source to produce NaCu(C 6 H 5 O 7 ). Examples of suitable inorganic or organic acid salts include ammonium and potassium salts or organic acids, such as ammonium oxalate, ammonium citrate, ammonium succinate, monobasic potassium citrate, dibasic potassium citrate, tribasic potassium citrate, potassium tartrate, ammonium tartrate, potassium succinate, potassium oxalate, and combinations thereof. The one or more chelating compounds may also include complexed salts, such as hydrates (e.g., sodium citrate dihydrate). 
     Although the plating solutions are particularly useful for plating copper, it is believed that the solutions also may be used for depositing other conductive materials, such as platinum, tungsten, titanium, cobalt, gold, silver, ruthenium, tin, alloys thereof, and combinations thereof. A copper precursor is substituted by a precursor containing the aforementioned metal and at least one ligand, such as cobalt citrate, cobalt sulfate or cobalt phosphate. 
     Optionally, wetting agents or suppressors, such as electrically resistive additives that reduce the conductivity of the plating solution may be added to the solution in a range from about 10 ppm to about 2,000 ppm, preferably in a range from about 50 ppm to about 1,000 ppm. Suppressors include polyacrylamide, polyacrylic acid polymers, polycarboxylate copolymers, polyethers or polyesters of ethylene oxide and/or propylene oxide (EO/PO), coconut diethanolamide, oleic diethanolamide, ethanolamide derivatives or combinations thereof. 
     One or more pH-adjusting agents are optionally added to the plating solution to achieve a pH less than 7, preferably between about 3 and about 7, more preferably between about 4.5 and about 6.5. The amount of pH adjusting agent can vary as the concentration of the other components is varied in different formulations. Different compounds may provide different pH levels for a given concentration, for example, the composition may include between about 0.1% and about 10% by volume of a base, such as potassium hydroxide, ammonium hydroxide or combinations thereof, to provide the desired pH level. The one or more pH adjusting agents can be chosen from a class of acids including, carboxylic acids, such as acetic acid, citric acid, oxalic acid, phosphate-containing components including phosphoric acid, ammonium phosphates, potassium phosphates, inorganic acids, such as sulfuric acid, nitric acid, hydrochloric acid and combinations thereof. 
     The balance or remainder of the plating solution described herein is a solvent, such as a polar solvent. Water is a preferred solvent, preferably deionized water. Organic solvents, for example, alcohols or glycols, may also be used, but are generally included in an aqueous solution. 
     Optionally, the plating solution may include one or more additive compounds. Additive compounds include electrolyte additives including, but not limited to, suppressors, enhancers, levelers, brighteners and stabilizers to improve the effectiveness of the plating solution for depositing metal, namely copper to the substrate surface. For example, certain additives may decrease the ionization rate of the metal atoms, thereby inhibiting the dissolution process, whereas other additives may provide a finished, shiny substrate surface. The additives may be present in the plating solution in concentrations up to about 15% by weight or volume, and may vary based upon the desired result after plating. 
     In one embodiment, the plating solution includes at least one copper source compound, at least one acid based electrolyte, and at least one additive, such as a chelating agent. In one embodiment, the at least one copper source compound includes copper sulfate, the at least one acid based electrolyte includes sulfuric acid, and the chelating compound includes citrate salt. 
     The columnar metal layer  226  is formed using a high plating rate deposition process. The current densities of the deposition bias are selected such that the current densities are above the limiting current (i L ). When the limiting current is reached the columnar metal film is formed due to the evolution of hydrogen gas and resulting dendritic type film growth that occurs due to the mass transport limited process. During formation of the columnar metal layer, the deposition bias generally has a current density of about 10 A/cm 2  or less, preferably about 5 A/cm 2  or less, more preferably at about 3 A/cm 2  or less. In one embodiment, the deposition bias has a current density in the range from about 0.5 A/cm 2  to about 3.0 A/cm 2 , for example, about 2.0 A/cm 2 . 
     The fifth process step  210  includes forming porous structure  228  on the columnar metal layer  226 . The porous structure  228  may be formed on the columnar metal layer  226  by increasing the voltage and corresponding current density from the deposition of the columnar metal layer. The deposition bias generally has a current density of about 10 A/cm 2  or less, preferably about 5 A/cm 2  or less, more preferably at about 3 A/cm 2  or less. In one embodiment, the deposition bias has a current density in the range from about 0.5 A/cm 2  to about 3.0 A/cm 2 , for example, about 2.0 A/cm 2 . 
     In one embodiment, the porous structure  228  may comprise one or more of various forms of porosities. In one embodiment, the porous structure  228  comprises macro porosity structure having pores of about 100 microns or less, wherein the non-porous portion of the macro porosity structure having pores of between about 2 nm to about 50 nm in diameter (meso porosity). In another embodiment, the porous structure  228  comprises macro porosity structure having pores of about 30 microns. Additionally, surface of the porous structure  228  may comprise nano structures. The combination of micro porosity, meso porosity, and nano structure increases surface area of the porous structure  408  tremendously. 
     In one embodiment, the porous structure  228  may be formed from a single material, such as copper, zinc, nickel, cobalt, palladium, platinum, tin, ruthenium, and other suitable material. In another embodiment, the porous structure  228  may comprises alloy of copper, zinc, nickel, cobalt, palladium, platinum, tin, ruthenium, or other suitable material. 
     Optionally, a sixth processing step  212  can be performed to form a passivation layer  230  on the porous structure  228 , as shown in  FIG. 3F . The passivation layer  230  can be formed by an electrochemical plating process. The passiviation layer  230  provides high capacity and long cycle life for the electrode to be formed. In one embodiment, the porous structure  228  comprises copper and tin alloy and the passivation layer  230  comprises a tin film. In another embodiment, the porous structure  228  comprises cobalt and tin alloy. In one embodiment, the passivation layer  230  may be formed by emerging the substrate  220  in a new plating bath configured to plating the passivation layer  230  after a rinsing step. 
     Embodiments of the present invention provide a processing system for continuously perform steps  208 ,  210 ,  212  of the process  200 .  FIG. 4  is a flow diagram of a method  250  for forming a porous electrode in accordance with embodiments described herein. Each block in method  250  is generally performed in a separated processing chamber. A substrate being processed is generally streamlined from one chamber to the next to complete the process. 
     In block  252 , a substrate deposited with a seed layer, by a PVD process or an evaporation process, is positioned in a pre-wetting chamber to remove oxides, carbon, or other contaminations before plating. Compared to PVD process, evaporation process is generally at a lower cost. 
     In block  254 , the pre-wetted substrate is emerged in a plating bath of a first plating chamber to form a columnar metal layer. 
     In block  256 , the substrate having the columnar metal layer formed thereon is removed from the first plating chamber and emerged in a plating bath of a second plating chamber to form a porous layer over the columnar metal layer. 
     In one embodiment, the columnar metal layer and the porous layer may comprise the same metal, such as copper, and the plating baths in the first and second chambers may similar or compatible in chemistry. In another embodiment, the porous layer may comprise tin and copper alloy. In another embodiment, the porous layer may comprise cobalt and tin alloy. In another embodiment, the porous layer may comprise alloy of cobalt, tin and copper. 
     In block  258 , the substrate is rinsed in a rinsing chamber to remove any residual plating path on the substrate. 
     In block  260 , the substrate is emerged in a plating bath in a third plating chamber to form a passivation thin film. In one embodiment, the passivation thin film may comprise a thin film of tin. 
     In block  262 , the substrate is rinsed and dried in a rinse-dry chamber for subsequent processing. 
       FIGS. 5-8  describe chambers and systems configured to perform formation of an electrode for an electrochemical battery or capacitor using the method  250 . 
       FIG. 5A  is a schematic sectional side view of a plating chamber  400  in accordance with one embodiment of the present invention. The plating chamber  400  is in a plating position.  FIG. 5B  is a schematic sectional side view of the plating chamber  400  in a substrate transferring position. 
     The plating chamber  400  is configured to form a metal layer  306  over a seed layer  305 , or a conductive layer, formed on a flexible base  301 . In one embodiment, the flexible base  301  is supplied to the plating chamber  400  by portion by portion. Each portion may be considered a substrate. Each substrate is generally cut from the rest of the flexible base  301  after processing. 
     In one embodiment, the plating chamber  400  is configured to deposit the metal layer  306  selectively over desired regions of the seed layer  305  using a masking plate  410 . The masking plate  410  has a plurality of apertures  413  that preferentially allow the electrochemically deposited material to form therein. In one embodiment, the masking plate  410  may define a pattern configured for a light-receiving side of the flexible solar cell. 
     The plating chamber  400  generally contains a head assembly  405 , flexible substrate assembly, an electrode  420 , a power supply  450 , a system controller  251 , and a plating cell assembly  430 . 
     The plating cell assembly  430  generally contains a cell body  431  defining a plating region  435  and an electrolyte collection region  436 . In operation it is generally desirable to pump an electrolyte “A” from the electrolyte collection region  436  through a plenum  437  formed between the electrode  420  and the support features  434  past the apertures  413  formed in the masking plate  410  and then over a weir  432  separating the plating region  435  and to the electrolyte collection region  436 , by use of a pump  440 . 
     In one embodiment, the electrode  420  may be supported on one or more support features  434  formed in the cell body  431 . In one embodiment, the electrode  420  contains a plurality of holes  421  that allow the electrolyte “A” passing from the plenum  437  to the plating region  435  to have a uniform flow distributed across masking plate  410  and contact at least one surface on the flexible base  301 . The fluid motion created by the pump  440  allows the replenishment of the electrolyte components at the exposed region  404  that is exposed at one ends of the apertures  413 . 
     The electrode  420  may be formed from material that is consumable during the electroplating reaction, but is more preferably formed from a non-consumable material. A non-consumable electrode may be made of a conductive material that is not etched during the formation the metal layer  306 , such as platinum or ruthenium coated titanium. 
     The head assembly  405  generally contains a thrust plate  414  and a masking plate  410  that is adapted to hold a portion of the flexible base  301  in a position relative to the electrode  420  during the electrochemical deposition process. In one aspect, a mechanical actuator  415  is used to urge the thrust plate  414  and the flexible base  301  against electrical contacts  412  formed on a top surface  418  of the masking plate  410  so that an electrical connection can be formed between the seed layer  305  formed on the surface of the flexible base  301  and the power supply  450  through the lead  451 . 
     In one embodiment, as shown in  FIG. 5A , the electrical contacts  412  are formed on a surface of the masking plate  410 . In another embodiment, the electrical contacts  412  may be formed from separate and discrete conductive contacts that are nested within a recess formed in the masking plate  410  when the flexible base  301  is being urged against the masking plate  410 . The electrical contacts  412  may be formed from a metal, such as platinum, gold, or nickel, or another conductive material, such as graphite, copper Cu, phosphorous doped copper (CuP), and platinum coated titanium (Pt/Ti). 
     The flexible substrate assembly  460  comprises a feed roll  461  coupled to a feed actuator, and a take-up roll  462  coupled to a take-up actuator. The flexible substrate assembly  460  is configured to feed, position portions of the flexible base  301  within the plating chamber  400  during processing. 
     In one aspect, the feed roll  461  contains an amount of the flexible base  301  on which a seed layer  305  has been formed. The take-up roll  462  generally contains an amount of the flexible base  301  after the metal layer  306 . The feed actuator and take-up actuator are used to position and apply a desired tension to the flexible base  301  so that the electrochemical processes can be performed on thereon. The feed actuator and take-up actuator may be DC servo motor, stepper motor, mechanical spring and brake, or other device that can be used to position and hold the flexible substrate in a desired position with the plating chamber  400 . 
       FIG. 5B  is a side cross-sectional view that illustrates the plating chamber  400  in transferring position to allow positioning a desired portion of the flexible base  301  containing the seed layer  305  into a desired position relative to masking plate  410  and the electrode  420  so that a metal layer  306  will be formed thereon. In on aspect, various convention encoders or other devices are used in conjunction with the feed actuator and/or take-up actuator to control and position a desired portion of the flexible base  301  containing the seed layer  305  within the head assembly  405 . 
       FIG. 5C  schematically illustrates a plating system  500  configured for plating an electrode of an electrochemical battery or capacitor using a method similar to the method  250  described above. 
     The plating system  500  generally comprises a plurality of processing chambers arranged in a line, each configured to perform one processing step to a substrate  511  formed on one portion of a continuous flexible base. 
     The plating system  500  comprises a pre-wetting chamber  501  configured to pre-wet a substrate  511  formed on a portion of the flexible base. The pre-wetting chamber  501  may be similar in structure to the plating chamber  400  of  FIG. 5A  without the electrodes  420 , the masking plate  410 , and the power supply  450  required for plating process. 
     The plating system  500  further comprises a first plating chamber  502  configured to perform a first plating process on the substrate  511  after being pre-wetted. The first plating chamber  502  is generally disposed next to the cleaning pre-wetting station. In one embodiment, the first plating process may be plating a columnar copper layer on a seed layer of formed on the substrate  511 . The first plating chamber  502  may be similar to the plating chamber  400  of  FIG. 4A  described above. 
     The plating system  500  further comprises a second plating chamber  503  disposed next to the first plating chamber  502 . The second plating chamber  503  is configured to perform a second plating process. In one embodiment, the second plating process is forming a porous layer of copper or alloys on the columnar copper layer. The second plating chamber  503  may be similar to the plating chamber  400  of  FIG. 4A  described above. 
     The plating system  500  further comprises a rinsing station  504  disposed next to the second plating chamber  503  and configured to rinse and remove any residual plating solution from the substrate  511 . The rinsing station  504  may be similar in structure to the plating chamber  400  of  FIG. 5A  without the electrodes  420 , the masking plate  410 , and the power supply  450  required for plating process. 
     The plating system  500  further comprises a third plating chamber  505  disposed next to the rinsing station  504 . The third plating chamber  505  is configured to perform a third plating process. In one embodiment, the third plating process is forming a thin film over the porous layer. The third plating chamber  505  may be similar to the plating chamber  400  of  FIG. 4A  described above. 
     The plating system  500  further comprises a rinse-dry station  506  disposed next to the third plating chamber  505  and configured to rinse and dry the substrate  511  after the plating processes and to get the substrate  511  ready for subsequent processing. The rinse-dry station  506  may be similar in structure to the plating chamber  400  of  FIG. 5A  without the electrodes  420 , the masking plate  410 , and the power supply  450  required for plating process. In one embodiment, the rinse-dry station  506  may comprise one or more vapor jets  506   a  configured to direct a drying vapor toward the substrate  511  as the substrate  511  exits the rinse-dry chamber  506 . 
     The processing chambers  501 - 506  are generally arranged along a line so that the substrates  511  can be streamlined through each chamber through feed rolls  507   1-6  and take up rolls  508   1-6  of each chamber. In one embodiment, the feed rolls  507   1-6  and take up rolls  508   1-6  may be activated simultaneously during substrate transferring step to move each substrate  511  one chamber forward. 
     Substrates are positioned in a substantially horizontal position in the description of the plating system  500  above. However, other substrate orientations, such as vertical or tilted can be used in accordance with embodiments of the present invention. 
       FIG. 6A  is a schematic sectional side view of a plating chamber  600  in accordance with one embodiment of the present invention. The plating chamber  600  is configured to form a metal layer over a seed layer  602 , or a conductive layer, formed on a flexible base  601 . Similar to the plating chamber  400  of  FIG. 5A , the flexible base  601  is supplied to the plating chamber  600  by portion by portion. Each portion may be considered a substrate. Each substrate is generally cut from the rest of the flexible base  601  after processing. 
     The plating chamber  600  generally comprises a chamber body  603  defining a processing volume  604 . The processing volume  604  is in fluid communication with one or more inlet jet  605  configured to dispense a plating solution in the processing volume  604 . The processing volume  604  is also in fluid communication with a drain  606  configured to remove the plating solution from the processing volume  604 . 
     The plating chamber  600  comprises a flexible substrate assembly  608  configured to move the flexible base  601  and to position a particular portion the flexible base  601  in the processing volume  604  to processing. The flexible substrate assembly  608  comprises a feed roll  609  disposed above the processing volume  604 , a bottom roll  610  disposed near a bottom portion of the processing volume  604 , a take-up roll  611  disposed above the processing volume  604 . Each of the feed roll  609 , the bottom roll  610 , and the take up roll  611  is configured to retain a portion of the flexible base  601 . The flexible substrate assembly  608  is configured to feed, position portions of the flexible base  601  within the plating chamber  600  during processing. 
     In one embodiment, at least the feed roll  609  and the take up roll  611  are coupled to actuators. The feed actuator and take-up actuator are used to position and apply a desired tension to the flexible base  601  so that the electrochemical processes can be performed on thereon. The feed actuator and take-up actuator may be DC servo motor, stepper motor, mechanical spring and brake, or other device that can be used to position and hold the flexible substrate in a desired position with the plating chamber  600 . 
     The plating chamber  600  also comprises an anode assembly  607  disposed in the processing volume  604 . In one embodiment, the anode assembly  607  is disposed in a substantially vertical orientation. In one embodiment, the anode assembly  607  may contains a plurality of holes that allow the plating bath passing from the inlet jets  605  to have a uniform flow distributed across a plating surface of the flexible base  601 . 
     The anode assembly  607  may be formed from material that is consumable during the electroplating reaction, but is more preferably formed from a non-consumable material. A non-consumable electrode may be made of a conductive material that is not etched during the formation a metal layer over the flexible base  601 , such as platinum or ruthenium coated titanium. 
     In one embodiment, the plating chamber  600  comprises a masking plate  613  configured to selectively expose regions of the seed layer  602  during processing. The masking plate  613  has a plurality of apertures  614  that preferentially allow the electrochemically deposited material to form therein. In one embodiment, the masking plate  613  may define a pattern configured for a light-receiving side of the flexible solar cell. 
     In one embodiment, the plating chamber  600  comprises a thrust plate  616  disposed in the processing volume  604 , substantially parallel to the anode assembly  607 . The thrust plate  616  is configured to hold a portion of the flexible base  601  in a position relative to the anode assembly  607  during the electrochemical deposition process. The thrust plate  616  is positioned on a backside of the flexible base  601  and the anode assembly  607  and masking plate  613  are positioned on a front side of the flexible base  601 . 
     In one embodiment, the thrust plate  616  is horizontally movable. During transferring stage, the thrust plate  616  is moved away from the flexible base  601  and neither the masking plate  613  nor the thrust plate  616  is in contact with the flexible base  601 . Before processing, at least one of the thrust plate  616  and the masking plate  613  is moved towards the other sandwiching the flexible base  601  in between. The thrust plate  616  ensures that the flexible base  601  is substantially parallel to the anode assembly  607  and in a desired distance from the anode assembly  607 . 
     In one embodiment, a power source  617   1  is coupled between the anode assembly  607  and the masking plate  613  to provide electric bias for a plating process. In one embodiment, a plurality of electrical contacts  615  is formed on a surface of the masking plate  613 . The power source  617   1  is coupled to the plurality of electrical contacts  615  which then provides electrical bias to the seed layer  602  when the masking plate  613  contacts the flexible base  601 . The plurality of electrical contacts  615  may be formed from separate and discrete conductive contacts that are nested within a recess formed in the masking plate  613  when the flexible base  601  is being urged against the masking plate  613 . The electrical contacts  615  may be formed from a metal, such as platinum, gold, or nickel, or another conductive material, such as graphite, copper Cu, phosphorous doped copper (CuP), and platinum coated titanium (Pt/Ti). 
     In another embodiment, a power source  617   2 , instead of the power source  617   1 , is coupled between the anode assembly  607  and the seed layer  602  directly. This is configuration is usually applicable when the seed layer  602  is continuous within each portion (substrate) and isolated from portion to portion. 
     In yet another embodiment, a power source  617   3 , instead of the power source  617   1 , is coupled between the anode assembly  607  and the feed roll  609 , which is in electrical contact with the flexible base  601 . This is configuration is usually applicable when the flexible base  601  is conductive. 
       FIG. 6B  is a schematic sectional side view of a plating chamber  600   c  in accordance with one embodiment of the present invention. The plating chamber  600   c  is similar to the plating chamber  600  of  FIG. 6A  except that the plating chamber  600   c  is configured to processing two portions of the flexible base  601  simultaneously. This is configuration can nearly double the system throughput. 
       FIG. 6C  schematically illustrates a plating system  700  using one or more plating chambers of  FIGS. 6A-6B . The plating system  700  configured for plating an electrode of an electrochemical battery or capacitor using a method similar to the method  250  described above. 
     The plating system  700  generally comprises a plurality of processing chambers arranged in a line, each configured to perform one processing step to a substrate formed on one portion of a continuous flexible base  710 . 
     The plating system  700  comprises a pre-wetting chamber  701  configured to pre-wet a portion of the flexible base  710 . The pre-wetting chamber  701  may be similar in structure to the plating chambers  600 ,  600   c  described above without the anode assembly  607 , the masking plate  613 , the thrust plate  616 , and the power source  617  required for plating process. 
     The plating system  700  further comprises a first plating chamber  702  configured to perform a first plating process the portion of the flexible base  710  after being pre-wetted. The first plating chamber  702  is generally disposed next to the cleaning pre-wetting station. In one embodiment, the first plating process may be plating a columnar copper layer on a seed layer of formed on a seed layer formed on the portion of the flexible base  710 . The first plating chamber  702  may be similar to the plating chambers  600 ,  600   c  described above. 
     The plating system  700  further comprises a second plating chamber  703  disposed next to the first plating chamber  702 . The second plating chamber  703  is configured to perform a second plating process. In one embodiment, the second plating process is forming a porous layer of copper or alloys on the columnar copper layer. The second plating chamber  703  may be similar to the plating chambers  600 ,  600   c  described above. 
     The plating system  700  further comprises a rinsing station  704  disposed next to the second plating chamber  703  and configured to rinse and remove any residual plating solution from the portion of flexible base  710  processed by the second plating chamber  703 . The rinsing station  704  may be similar in structure to the plating chambers  600 ,  600   c  described above without the anode assembly  607 , the masking plate  613 , the thrust plate  615 , and the power source  617  required for plating process. 
     The plating system  700  further comprises a third plating chamber  705  disposed next to the rinsing station  704 . The third plating chamber  705  is configured to perform a third plating process. In one embodiment, the third plating process is forming a thin film over the porous layer. The third plating chamber  705  may be similar to the plating chambers  600 ,  600   c  described above. 
     The plating system  700  further comprises a rinse-dry station  706  disposed next to the third plating chamber  705  and configured to rinse and dry the portion of flexible base  710  after the plating processes. The rinse-dry station  706  may be similar in structure to the plating chambers  600 ,  600   c  described above without the anode assembly  607 , the masking plate  613 , the thrust plate  615 , and the power source  617  required for plating process. In one embodiment, the rinse-dry station  706  may comprise one or more vapor jets  706   a  configured to direct a drying vapor toward the flexible base  710  as the flexible base  710  exits the rinse-dry station  706 . 
     The processing chambers  701 - 706  are generally arranged along a line so that portions of the flexible base  710  can be streamlined through each chamber through feed rolls  707   1-6  and take up rolls  708   1-6  of each chamber. In one embodiment, the feed rolls  707   1-6  and take up rolls  708   1-6  may be activated simultaneously during substrate transferring step to move each portion of the flexible base  710  one chamber forward. 
       FIG. 7A  is a schematic perspective view of a plating chamber  800  in accordance with one embodiment of the present invention.  FIG. 7B  is a schematic sectional side view of the plating chamber  800  of  FIG. 7A  in plating position. 
     The plating chamber  800  generally comprises a chamber body  801  defining a processing volume  802  configured retaining a plating bath for processing one or more substrates in a substantially vertical position. The processing volume  802  has a top opening  802   a  configured to allow passage of substrates being processed. The plating chamber comprises a plurality of inlet jets  803  disposed on a sidewall of the chamber body  801 . In one embodiment, the plurality of inlet jets  803  may be distributed across the sidewall. The plurality of inlet jets  803  may also be used to spray wetting solution or cleaning solution towards a substrate being processed. The plurality of inlet jets  803  are connected to a plating solution source  804 . 
     In one embodiment, the plating chamber  800  further comprises a drain  812  configured to remove processing solution from the processing volume  802 . In another embodiment, as shown in  FIG. 7B , the plating chamber  800  may comprise a catch pen  825  configured to retain plating solution overflowing from the top opening  802   a  of the processing volume  802 . In one embodiment, the plating solution retained in the catch pen  825  may be filtered and flown back to the plating solution source  804  for reuse. 
     The plating chamber  800  comprises an anode assembly  805  disposed in the processing volume  802  in a substantially vertical orientation. In one embodiment, the anode assembly  805  may be removable from the processing volume  802  for maintenance or replacement. In one embodiment, the anode assembly  805  may contains a plurality of holes that allow the plating bath passing from the inlet jets  803  to have a uniform flow distributed across the processing volume  802 . 
     The anode assembly  805  may be formed from material that is consumable during the electroplating reaction, but is more preferably formed from a non-consumable material. A non-consumable electrode may be made of a conductive material that is not etched during plating, such as platinum or ruthenium coated titanium. The advantages of non consumable anodes include low cost and maintenance for being non-consumable, inert to chemical, good for alloy combination, good for pulse condition, 
     The plating chamber  800  further comprises a cathode assembly  806  configured to transfer one or more substrates  808  and position the one or more substrates  808  in a plating position as shown in  FIG. 7B . As illustrated in  FIG. 7A , the cathode assembly  806  can be lowered into the processing volume  802  via the top opening  802   a.    
     Flexible substrates are commonly used in producing some devices, such as solar battery cells. In one embodiment, the cathode assembly  806  is configured to support one or more flexible substrates for plating. In one embodiment, the cathode assembly  806  may comprise a back plate  810  configured to provide structural support to the substrate  808 . 
     As discussed above, a plating process is generally performed to form a metal layer over a seed layer  809  formed on the substrate  808 . The cathode assembly  806  is configured to support the substrate  808  so that the seed layer  809  is facing the anode assembly  805 . 
     In one embodiment, the cathode assembly  806  comprises a masking plate  807  configured to selectively expose regions of the seed layer  809  during processing. The masking plate  807  has a plurality of apertures  807   a  that preferentially allow the electrochemically deposited material to form therein. In one embodiment, the masking plate  807  may define a pattern configured for a light-receiving side of the flexible solar cell. 
     In one embodiment, the anode assembly  805  and the cathode assembly  806  may be moved relative to each other to achieve a desired spacing between the substrate  808  and the anode assembly  805  for plating. 
     A power source  811  is coupled between the anode assembly  805  and the substrate  808  to provide a bias for electroplating. In one embodiment, a plurality of electrical contacts  807   b  is formed on a surface of the masking plate  807 . In one embodiment, the power source  811  may be connected to the substrate  808  via the electrical contacts  807   b  of the masking plate  807 . The electrical contacts  807   b  may be formed from a metal, such as platinum, gold, or nickel, or another conductive material, such as graphite, copper Cu, phosphorous doped copper (CuP), and platinum coated titanium (Pt/Ti). 
     The cathode assembly  806  may be configured to support a single substrate or multiple substrates.  FIG. 7C  is a schematic view of the cathode assembly  806  in accordance with one embodiment of the present invention. The cathode assembly  806  shown in  FIG. 7C  is configured to support  4  substrates  808 . The cathode assembly  806  comprises a supporting frame  815  on which substrates  808  may be mounted. 
       FIGS. 8A-8B  schematically illustrate a plating system  900  in accordance with one embodiment of the present invention. The plating system  900  comprises a plurality of processing chambers similar in structure to the plating chamber  800  of  FIG. 7A . The plating system  900  configured for plating an electrode of an electrochemical battery or capacitor using a method similar to the method  250  described above. 
     The plating system  900  generally comprises a plurality of processing chambers  901 ,  902 ,  903 ,  904 ,  905 ,  906  arranged in a line, each configured to perform one processing step to substrates secured on substrate holders  907   1 - 907   6 . The substrate holders  907   1 - 907   6  may be transferred by a substrate transferring mechanism  910  among the processing chambers  901 - 906 . 
     In one embodiment, the substrate holders  907   1 - 907   6  are similar to the cathode assembly  806  of the plating chamber  800  described above. 
     In one embodiment, the processing chamber  901  may be a pre-wetting chamber configured to pre-wet a substrate disposed therein. 
     The processing chamber  902  may be a plating chamber configured to perform a first plating process the portion of the substrate after being pre-wetted in the processing chamber  901 . In one embodiment, the first plating process may be configured to form a columnar metal layer over a seed layer of the substrate. 
     The processing chamber  903  may be a plating chamber configured to perform a second plating process the portion of the substrate after the plating process in the processing chamber  902 . The second plating process may be configured to form a porous layer over the columnar metal layer. 
     The processing chamber  904  may be a rinsing chamber configured to rinse and remove any residual plating solution from the substrate after the second plating process in the processing chamber  903 . 
     The processing chamber  905  may be a plating chamber configured to perform a third plating process. In one embodiment, the third plating process is configured to form a thin film over the porous layer. 
     The processing chamber  906  may be a rinse-dry station configured to rinse and dry the substrate after the third plating process. 
       FIGS. 8A-8B  illustrate a substrate transferring sequence during processing. As shown in  FIG. 8A , the substrate holder  907   6  may be transferred out of the processing chamber  906  having vapor jets  907   a  after drying, while the substrate transferring mechanism  910  is in position to pick up substrate holders  907   1 - 907   5  in the processing chambers  901 - 905  simultaneously after processes are complete in each chamber. 
     In  FIG. 8B , the substrate transferring mechanism  910  picks up the substrate holders  907   1 - 907   5  from the processing chambers  901 - 905  and moves the substrate holders  907   1 - 907   5  down the line to the next chambers. The processing chamber  901  is ready for new substrates being secured in a new substrate holder  907   7 . 
     The substrate transferring mechanism  910  drops the substrate holders  907   1 - 907   5  to the processing chambers  902 - 906  respectively. The processing chamber  901  processing the substrates secured in the substrate holder  907   7 . 
     The substrate transferring mechanism  910  moves backward to pick up the substrate holders  907   7 , and  907   1 - 907   4  to the processing chambers  901 - 905  respectively. The substrates in the substrate holder  907   5  are ready to exit the plating system  900 . These moving steps are repeated for a streamline process. 
     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.