Abstract:
The invention relates to apparatus and methods for generating and recycling fluorine. The applicants recognized that a fluorine separator, used either alone or in combination with a plasma generator can produce sufficient quantities of fluorine at its point of use for thin film processing. The fluorine separator can take the form of a condenser, a membrane separation device, a fluorine ion conductor comprising a solid electrolyte, or a combination of the foregoing. In some embodiments, reaction products comprising fluorine are passed to the fluorine separator. In other embodiments, separated fluorine is passed, either alone or in conjunction with additional feed stock comprising fluorine, to a plasma generator. The fluorine separator allows fluorine to be recycled and waste products to be eliminated from the system.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to fluorine generation and recirculation and, more particularly, fluorine generation and recirculation at its point of use.  
         BACKGROUND INFORMATION  
         [0002]    Fluorine, in its atomic and molecular state, is highly reactive and toxic. Most laboratories prefer not to use fluorine due to the dangers and expense of the necessary safety equipment associated with its use. Some industries, nonetheless, find that fluorine fills an important role better than other known chemistries.  
           [0003]    Traditionally, molecular fluorine is generated from HF electrolytically. NF 3  has also been used to generate fluorine, particularly in thin film processing industries, such as semiconductor and flat panel display fabrication. Both HF and NF 3 , however, are toxic and require expensive special handling.  
           [0004]    If fluorine could be generated from a nontoxic, inert compound that contains fluorine, the danger and expense associated with the use of fluorine could be substantially reduced. For example, the piping and distribution system for such a compound need not comply with the stringent requirements associated with the piping and distribution of HF or NF 3 . The closer to its point of use that fluorine could be generated, the less danger its use would pose.  
           [0005]    Moreover, if fluorine could be recovered from the byproducts of its use, then fluorine could be used more efficiently. Fluorine recovery would minimize the total amount of fluorine source compound required for a particular application. Fluorine recovery could also minimize the risks and costs associated with the distribution of fluorine.  
           [0006]    Accordingly, there is a need to safely generate fluorine as close to its the point of use as possible; a need to generate fluorine from a nontoxic, inert compound that contains fluorine; and a need to recover fluorine from the byproducts of its use.  
         SUMMARY OF THE INVENTION  
         [0007]    The applicants recognized that a fluorine separator, used either alone or in combination with a plasma generator, can produce sufficient quantities of fluorine at its point of use for thin film processing. The fluorine separator can take the form of a condenser, a membrane separation device, a fluorine ion conductor comprising a solid electrolyte, or a combination of the foregoing.  
           [0008]    The fluorine separator can be used with a variety of gases comprising fluorine—such as F 2 , HF, SF 6 , NF 3 , CF 4 , C 2 F 6 , C 3 F 8 , and other fluorine compounds. Of the gases comprising fluorine, CF 4 , C 3 F 8 , C 2 F 6 , and SF 6 , for example, may be considered inert transport mediums for fluorine. Moreover, the fluorine separator, again used either alone or in combination with a plasma generator, makes fluorine recirculation possible.  
           [0009]    In general, in one aspect, the invention is an apparatus for producing a flux of atomic fluorine for use in a process chamber featuring a housing, an electrochemical cell, and an adapter. The housing has an inlet for receiving a gas comprising fluorine. The electrochemical cell has at least one electrode and, proximate to the at least one electrode, a fluorine ion conductor comprising a solid electrolyte. The electrochemical cell separates fluorine from the gas comprising fluorine. The electrochemical cell is at least partially disposed within the housing and has an outlet channel. The adapter connects the outlet channel to the process chamber. In one embodiment, the adapter connects the outlet channel to the process chamber via a plasma generator.  
           [0010]    In various embodiments of the foregoing, the electrochemical cell forms a tube or a plate. In some embodiments of the foregoing, the electrode comprises a cathode and the cell further comprising an anode proximate to the fluorine ion conductor. In these embodiments, the anode may comprise a thin film. The thin film may be characterized by a porosity or a pattern that minimizes the formation of molecular fluorine at the anode. A thick conductive grid may be disposed relative to the thin film. In some embodiments, the anode comprises a porous nickel or stainless steel.  
           [0011]    In general, in another aspect, the invention is an apparatus for generating fluorine gas featuring a plasma generator and a fluorine separator. The plasma generator has an inlet for receiving a feed stock comprising fluorine and an outlet. The plasma generator forms a plasma that dissociates the feed stock into reaction products. The fluorine separator has an inlet connected to the outlet of the plasma generator for receiving reaction products and a fluorine outlet. The fluorine separator may be a membrane separation device, a condenser, a fluorine ion conductor comprising a solid electrolyte, or a combination of the foregoing. The fluorine separator separates fluorine from the reaction products.  
           [0012]    Embodiments of the foregoing apparatus may have a variety of additional elements or connections to achieve various purposes. For example, the apparatus may include a flow control device that directly or indirectly connects to the fluorine outlet of the fluorine separator. Similarly, embodiments of the apparatus may include a second plasma generator that directly or indirectly connects to the fluorine outlet. The inlet of the fluorine separator, in some embodiments, is connected to the outlet of the plasma generator via a process chamber. In one embodiment, the fluorine outlet is indirectly connected to the inlet of the plasma generator thereby enabling fluorine gas to be recycled. For example, the fluorine outlet may be connected to the inlet of the plasma generator via a buffer volume.  
           [0013]    In general, in another aspect, the invention is an apparatus for producing a fluorine gas for use in a process chamber. The invention features a solid electrolyte for separating fluorine from a feed stock comprising fluorine, a pressure control mechanism, and an adapter. The solid electrolyte is partially electronically conductive, meaning that it conducts electrons to some extent, as well as ions, and has an inlet side for receiving the feed stock and an outlet side. (As used herein, “electronically conductive” refers to a medium that conducts electrons.) The pressure control mechanism is proximate to the inlet side of the solid electrolyte. The pressure control mechanism maintains a partial pressure of the feed stock on the inlet side of the solid electrolyte higher than the partial pressure of fluorine on the outlet side. The adapter connects the outlet side of the solid electrolyte to the process chamber, directly or via a plasma generator.  
           [0014]    In a similar aspect, the invention is a method of producing a flux of atomic fluorine for use in a process chamber. In the method, a fluorine ion conductor comprising a solid electrolyte having an inlet side and an outlet side is provided. A feed stock comprising fluorine is received at the inlet side of the fluorine ion conductor. Fluorine is separated from the feed stock comprising fluorine with the fluorine ion conductor. Fluorine is provided to the process chamber from the outlet side of the fluorine ion conductor.  
           [0015]    In general, in another aspect, the invention is a method for generating fluorine gas. A feed stock comprising fluorine is dissociating into reaction products with a plasma, and fluorine is separated from the reaction products with a fluorine separator. The fluorine separator is a membrane separation device, a fluorine ion conductor comprising a solid electrolyte, or a condenser.  
           [0016]    In general, in another aspect, the invention is a method of recirculating fluorine gas. Exhaust from a process chamber is received. Fluorine is separated from a gas comprising fluorine with a fluorine ion conductor comprising a solid electrolyte. Molecular or atomic fluorine is compressed to drive recirculation.  
           [0017]    Various embodiments of the foregoing methods further include one or more of the following steps: dissociating molecular fluorine into atomic fluorine with a plasma; providing atomic fluorine to the process chamber; or draining the unwanted products of the separating step away from the fluorine. The exhaust, in one embodiment, is chamber clean exhaust. In alternative embodiments, the compression may be accomplished with the fluorine ion conductor and/or a pump.  
           [0018]    In some embodiments of the foregoing, pressure control is used to inhibit fluorine recombination on the outlet side of the fluorine separator. For example, in one such apparatus, a pressure control mechanism inhibits fluorine recombination on the outlet side. The pressure control mechanism may comprises a pump. Pressure on the outlet side of the fluorine separator may be maintained at or below 100 torr, or at or below 20 torr.  
           [0019]    Similarly, in some embodiments of the foregoing, temperature control is used to inhibit fluorine recombination on the outlet side of the fluorine separator. For example, in one such apparatus, a temperature control mechanism controls the temperature of at least one surface. The surface may be that of the electrolyte or of the fluorine outlet channel.  
           [0020]    The foregoing and other aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings in which:  
         [0022]    [0022]FIG. 1 is an apparatus for generating fluorine gas in accordance with one embodiment of the invention;  
         [0023]    [0023]FIG. 2 is an apparatus for generating fluorine gas in accordance with another embodiment of the invention;  
         [0024]    [0024]FIG. 3 is a general schematic of an electrochemical cell in accordance with one embodiment of the invention;  
         [0025]    [0025]FIGS. 4A, 4B,  4 C,  4 D, and  4 E are different views of a fluorine separator based on the electrochemical cell of FIG. 3;  
         [0026]    [0026]FIG. 5 is an apparatus for generating fluorine gas with a fluorine separator in accordance with the invention; and  
         [0027]    [0027]FIG. 6 is an apparatus for generating and recycling fluorine gas in accordance with the invention. 
     
    
     DESCRIPTION  
       [0028]    Referring to FIG. 1, an apparatus for generating fluorine gas  100 , in accordance with one embodiment of the invention, features a plasma generator  130  and a fluorine separator  160 . The plasma generator  130 , in various embodiments, is a microwave plasma generator, an RF inductively coupled plasma generator, an RF toroidal inductively coupled plasma generator, or an RF capacitively coupled plasma generator. The plasma generator  130  may, for example, be an ASTRON™ or Rapid™ reactive gas generator. The plasma generator  130  comprises an inlet  132  and an outlet  134 . A feed stock comprising fluorine is received at the inlet  132  of the plasma generator  130 . The plasma generator  130  forms a plasma that dissociates the feed stock into reaction products. The reaction products exit the plasma generator  130  via the outlet  134 . The plasma generator  130 , in various embodiments, operates at or below atmospheric pressure.  
         [0029]    In FIG. 1, the fluorine separator  160  is a condenser that cools and condenses at least some of the reaction products. The condenser  160  comprises an inlet  162  and a fluorine outlet  164 . The inlet  162  of the condenser  160  is connected to the outlet  134  of the plasma generator. The condenser  160  receives reaction products via the inlet  162 . In one embodiment, the condenser  160  further comprises an unwanted products outlet (not shown) out of which the unwanted products of condenser drain. In another embodiment, the unwanted products drain away from the fluorine via the plasma generator and a waste outlet  136 .  
         [0030]    In various applications, the feed stock is one or more gases comprising fluorine—such as F 2 , HF, SF 6 , NF 3 , CF 4 , C 2 F 6 , C 3 F 8 , and other fluorine compounds. Gases that are not necessarily recirculated, and may be freshly provided to a system, are referred to as feed stock. Of the gases comprising fluorine, CF 4 , C 2 F 6 , C 3 F 8  and SF 6 , for example, may be considered inert transport mediums for fluorine. In various applications, the reaction products comprise a compound that includes sulfur or carbon. Where the feed stock comprises SF 6 , the reaction products may include F 2 , S x F y , and S in gas and liquid phases.  
         [0031]    In various applications, a reactant gas is introduced to the plasma generator  130  in addition to the feed stock comprising fluorine. In these applications, the plasma generator  130  forms a plasma that dissociates or excites the reactant gas, as well as the feed stock comprising fluorine. The reactant gas may be introduced to the plasma generator  130  via the inlet  132 . The reactive gas in some applications is O 2 . The separation of fluorine from the reactions products may result in unwanted S 2  and/or SO 2 .  
         [0032]    In one embodiment of apparatus  100 , the condenser  160  separates and delivers F 2 , and a second plasma generator (not shown) forms a plasma that dissociates the F 2  into atomic fluorine. The atomic fluorine from such an embodiment may be introduced into a process chamber.  
         [0033]    In some embodiments of apparatus  100 , a mass flow control device (not shown) regulates the flow of fluorine through the outlet  164 . The mass flow control device may be directly or indirectly connected to the fluorine outlet  164 . The mass flow control device can be a pressure control device, can simply incorporate a pressure control device or may only regulate flow independent of pressure. The device may serve to control the pressure at the fluorine outlet  164 .  
         [0034]    In some embodiments of apparatus  100 , the inlet  162  of the condenser  160  is connected to the outlet  134  of the plasma generator via a process chamber (not shown). This arrangement allows the condenser  160  to separate fluorine from the reaction products of the process chamber. When the fluorine outlet  164  is also connected to the inlet  132  of the plasma generator  130  via a pump or other compressing device, the apparatus  100  enables fluorine gas to be recycled. In one such embodiment, the fluorine outlet  164  is connected to the inlet  132  of the plasma generator  130  via a buffer volume (not shown). The buffer volume includes an enclosed volume along with appropriate control valves and sensors. The buffer volume can store a quantity of fluorine—so that there may be a delay before the fluorine is reused.  
         [0035]    A method of generating fluorine gas features dissociating a feedstock comprising fluorine into reaction products with a plasma, and separating fluorine from the reaction products with a fluorine separator. The method may take advantage of the apparatus  100  of FIG. 1 or a group of elements with similar functions. For example, although the apparatus  100  of FIG. 1 features the condenser  160  to separate fluorine from the reaction products, the method does not require the condenser. The method may use a membrane separation device, a fluorine ion conductor comprising a solid electrolyte, a condenser, or a combination of the foregoing to accomplish the separation.  
         [0036]    Referring to FIG. 2, an apparatus  200  for generating fluorine gas, in accordance with another embodiment of the invention, features a plasma generator  230 , a first fluorine separator  260 , and a second fluorine separator  280 . The plasma generator  230  comprises an inlet  232  and an outlet  234 , and is structurally and functionally similar to plasma generator  130  described with respect to FIG. 1. Likewise, the first fluorine separator  260  is a condenser that comprises an inlet  262  and an outlet  264 , and that is structurally and functionally similar to the condenser  160  described with respect to FIG. 1. The condenser  160  can also serve the purpose of cooling the gas before it reaches the second separator  280 .  
         [0037]    In the embodiment depicted in FIG. 2, the second fluorine separator  280  is a membrane separation device. The membrane separation device  280  comprises an inlet side  282  and an outlet side  284 . The inlet side  282  of the membrane separation device  280  is connected to the outlet  264  of the condenser  260 . In one such embodiment, the membrane separation device  280  is used in conjunction with the condenser  260  because the condenser  260  is not completely effective in separating fluorine from the reaction products. Atomic fluorine dissociated by the plasma in the plasma generator  230  recombines into molecular flourine before reaching the membrane separation device  280 . Accordingly, the membrane separation device  280  serves to separate molecular fluorine from the reaction products.  
         [0038]    In one embodiment of FIG. 2, the membrane separation device  280  features a means for allowing particles with a diameter of about 1.4 Å, but not particles with a diameter substantially greater than 1.4 Å, to pass. Molecular fluorine has a diameter of diameter of about 1.4 Å, which is small in comparison to most of the other likely products of dissociation. For example, SF 6  has a diameter of about 5 Å and O 2  has a diameter of about 3.3 Å. In alternative embodiments, the membrane separation device  280  features a porosity or channels with the appropriate characteristic. In some such embodiments, the temperature of the membrane is controlled to establish the desired permeability in the membrane. In the embodiment of FIG. 2, a gradient in the partial pressure of fluorine between the inlet side  282  and an outlet side  284  of the membrane separation device  280  may be used, additionally or alternatively, to accelerate the passage.  
         [0039]    In Carbon Membrane Separator for Elimination of SF 6  Emissions From Gas-Insulated Electrical Utilities, which is hereby incorporated by reference, Dagan et al. from Carbon Membranes, Ltd. of Arava, Israel describe the production of carbon molecular sieve membranes and their use to separate O 2  and N 2  from SF 6 . Similar techniques may be used to produce a molecular sieve membrane to separate F 2  from other, likely larger, molecules and particles.  
         [0040]    In general, the apparatus  200  of FIG. 2 may feature the same variations in embodiments and applications that were described with respect to the apparatus  100  of FIG. 1. Additionally, in an alternative embodiment of an apparatus for generating fluorine gas, a membrane separation device  280 , such as described with respect to FIG. 2, replaces the condenser  160  described with respect to FIG. 1. In a second alternative embodiment, the apparatus  200  comprises a condenser  260 , but does not incorporate the membrane separation device  280 .  
         [0041]    [0041]FIG. 3 illustrates a general schematic of an electrochemical cell  300  for separating fluorine from gas comprising fluorine as incorporated into an embodiment of the invention. FIG.  3  features an electrode ( 330  or  370 ) and a fluorine ion conductor  350  comprising a solid electrolyte proximate to the electrode. The solid electrolyte, in some embodiments, comprises Pb 2 Sn 2 F 4  The solid electrolyte, in some embodiments, is partially electronically conductive with diffused or distributed electronic conductivity. The electrode may be formed from any appropriate electrode material known in the art. In various embodiments, the cell  300  takes the form of a tube, a plate, or a disc.  
         [0042]    In some embodiments, the cell  300  features a separate power supply  380  and a second electrode proximate to the solid electrolyte  350 . The power supply  380  is electrically connected to both electrodes and thereby causes one electrode to act as a cathode  330  and the other to act as an anode  370 .  
         [0043]    In some embodiments, the anode  370  of FIG. 3 comprises a thin film. An anode film is thin, for purposes of the invention, if it allows fluorine ions and/or atoms to pass. The anode material, in such embodiments, may comprise porous nickel or Stainless Steel. The thin film, in various embodiments, is characterized by a porosity or pattern that has openings spaced to minimize the formation of molecular fluorine proximate the anode  370 . In some embodiments, the anode  370  features a thick conductive grid. The grid improves heat dissipation and mitigates power loss. In some such embodiments, portions of a single thick conductive layer on the solid electrolyte are removed to create an anode  370  comprising a thin film and a thick conductive grid. In other embodiments, the thin film and the conductive grid form separate layers.  
         [0044]    In another embodiment, the cell  300  alternatively comprises a means for applying an electrical field to a surface of the solid electrolyte  350 . Fluorine ions can thereby be extracted directly from the surface of the solid electrolyte  350 . In a similar embodiment, a thin, doped layer of the solid electrolyte  350  acts an anode  370  and the electrode acts as a cathode.  
         [0045]    In operation, the solid electrolyte  350  of the cell  300  separates fluorine from a gas comprising fluorine. The fluorine is ionized, producing two negative ions, proximate to the cathode  330 . Fluorine ions are then transported through the solid electrolyte  350  toward the anode  370 . The influence of a field on the solid electrolyte  350  can accelerate the transportation. Power supply  380 , for example, can create an electrical field across the solid electrolyte  350  that accelerates the transportation. Additionally or alternatively, a gradient in the partial pressure of fluorine between the cathode side  310  and the anode side  390  of the fluorine ion conductor  350  may accelerate the transportation.  
         [0046]    In most applications, the fluorine ion gives up its electron to the anode  370 , and then recombines with another fluorine atom to form molecular fluorine. In these applications, the cell  300  can be used to separate molecular flourine from gas comprising fluorine, and to compress the molecular fluorine to the desired pressure. The cell  300  electrochemically transports the low pressure gas on the cathode side  310  of the cell  300  to a higher pressure on the anode side  390  of the cell  300 . The use of the cell  300  in this fashion may eliminate the requirement for a separate, mass flow control device to compress the molecular fluorine.  
         [0047]    In certain applications, the pressure and/or temperature at the anode side  390  of the ion conductor  350  are controlled to inhibit the formation of molecular fluorine. At an appropriately low pressure and/or high temperature, the fluorine atoms can be desorbed without recombination. The probability of two fluorine atoms coming together is reduced at low pressure and the time spent by an atom on a material surface, where recombination is most likely to occur, is reduced at high temperature. In some such applications, the pressure at the anode side  390  of the ion conductor  350  is maintained at or below 100 torr. In related applications, the pressure at the anode side  390  of the ion conductor  350  is maintained at or below 20 torr.  
         [0048]    A difference in partial pressure of fluorine between the two sides of the electrochemical cell produces a potential difference, which drives ions from the high partial pressure side to the low partial pressure side. In such a case, one can provide a circuit from the anode to the cathode—thereby returning the electrons that were carried across the cell by the negative fluorine ions. This return circuit can be external to the cell (e.g., by a wire). Alternatively, the circuit can pass back through the cell if some electron conductivity is built into the electrolyte or cell structure.  
         [0049]    [0049]FIGS. 4A, 4B,  4 C,  4 D, and  4 E are different views of a fluorine separator  400  in accordance with one embodiment of the invention. FIG. 4A illustrates a three-dimensional view of the housing  415  of the fluorine separator  400 . The housing  415  in the embodiment of FIG. 4A comprises an inlet  410  for receiving a gas comprising fluorine, a fluorine outlet  420 , and an unwanted products outlet (not shown, but situated opposite the inlet  410 ). FIG. 4B illustrates the same three-dimensional view of the fluorine separator  400  shown in FIG. 4A, but with its housing  415  removed to reveal its internal structure. A number of plates  430  are mechanically attached to a supportive sidewall  440  that forms a component in the housing  415 . Each plate  430  comprises a number of layers. FIG. 4C is a top view of the housing  415  of the fluorine separator  400  identifying the I-I′ location. FIG. 4D is a cross-sectional side view of the internal structure of the fluorine separator  400  at the I-I′ location. FIG. 4D illustrates the same plates  430  shown in FIG. 4B in a cross-sectional side view. The mechanical attachment of the plates  430  to the supportive sidewall  440  is again shown.  
         [0050]    [0050]FIG. 4E is a more detailed cross-sectional side view of a single plate  430  within the internal structure of the fluorine separator  400 . As FIG. 4E shows, the fluorine separator  400  shown in FIG. 4 comprises a plurality of electrochemical cells  300  as described with respect to FIG. 3. Each cell  300  is disposed within the housing  415 . Each cell comprises an outer electrode  432 , a solid electrolyte  434 , and an inner electrode  436  on a metal mount  438  and a thermal mount  439 . Both of the electrodes  432  and  436  allow the passage of fluorine ions. The metal mount  438  and the thermal mount  439  comprise buried gas channels  426  that connect to the cell  300 . Each buried gas channel  426  also connects to a central gas channel  424  within the structural element  439  that supports the plate  430 . The central gas channel  424  within each plate  430  connects to a central gas channel  422  within the sidewall  440  that routes fluorine to the fluorine outlet  420 . As illustrated in the embodiment of FIG. 4E, each plate  430  may have an electrochemical cell on its top and bottom surface.  
         [0051]    In operation, the inlet  410  of the fluorine separator  400  receives a gas comprising fluorine. The gas interacts with the electrochemical cells within the housing  415 . Fluorine is separated from the gas, transported through the cells to a buried gas channel  426 , to the central gas channel  424  within the plate, to the central gas channel  422  within the sidewall  440 , and then to the fluorine outlet  420 . Fluorine exits the fluorine separator  400  via the fluorine outlet  420 . Typically, the fluorine separator  400  will produce a molecular fluorine flux at the fluorine outlet  420 . As explained with respect to FIG. 3, however, the characteristics of the anode and the conditions on the anode side of the electrochemical cell may inhibit the formation of molecular fluorine, thereby allowing an atomic fluorine flux to be created at the fluorine outlet  420 . The byproducts of the fluorine separation exit the outer housing of the fluorine separator  400  via the waste products outlet (not shown).  
         [0052]    Various embodiments of fluorine separators comprising a solid electrolyte feature a temperature control mechanism that controls the temperature of at least one surface. The temperature control mechanism of the fluorine separator  400 , for example, may be the thermal mount  439 . The thermal mount  439  may control the temperature of a surface of the solid electrolyte  434 , of the buried gas channel  426 , and/or of the central gas channel  424  within the plate. The temperature control mechanism, in alternative embodiments, is active or passive. Temperature control can be useful in inhibiting the formation of molecular fluorine. Also, temperature control can optimize the ionic conductivity of the electrolyte.  
         [0053]    In an embodiment for one application, an adapter (not shown) proximate to the fluorine outlet  420  connects the outlet  420  to a process chamber. The adapter may, for example, receive a pipe that connects to the process chamber. The fluorine produced by operation of the fluorine separator  400  is thereby provided to the process chamber. In one application, the flux of atomic fluorine from the fluorine separator  400  is used directly in a thin film process, such as chamber cleaning or product etching. Alternately, molecular fluorine from the fluorine separator is provided to the process chamber via a plasma generator that dissociates the molecular fluorine into atomic fluorine. The flux of fluorine from the fluorine separator  400  can also be used in other applications. These applications include fluorination of plastics and production of fluoride gases and materials.  
         [0054]    The fluorine separator  400  can be used in the apparatus of FIG. 1 instead of condenser  160 . Similarly, the fluorine separator  400  can also be used in the apparatus of FIG. 2 as the second fluorine separator  280 . The fluorine separator  400  can also replace both the fluorine separator  280  and the plasma generator  230 . This embodiment can be useful for feed stock and reactive gases that can be dissociated directly by the electrochemical cell at the inlet side of the fluorine ion conductor.  
         [0055]    [0055]FIG. 5 is an apparatus  500  for generating fluorine gas in accordance with one embodiment of the invention. The apparatus can comprise an optional plasma generator  520  and a fluorine separator  540 . The plasma generator  520  has an inlet  523  for a feed stock comprising fluorine and an outlet  526  for the reaction products. The plasma generator  520  is structurally and functionally similar to the plasma generator  130  described with respect to FIG. 1.  
         [0056]    The fluorine separator  540  has an inlet  544 , which connects to the outlet  526  of the plasma generator  520  for receiving reaction products, and a fluorine outlet  543 . In various embodiments, the fluorine separator  540  is structurally and functionally similar to the condenser  160  described with respect to FIG. 1, the condenser  260  or the membrane separation device  280  described with respect to FIG. 2, or the electrochemical cell  300  described with respect to FIG. 3. In one embodiment, the fluorine separator  540  is structurally and functionally similar to the fluorine separator  400  described with respect to FIG. 4.  
         [0057]    In operation, feed stock comprising fluorine, such as SF 6  or CF 4 , is introduced into the plasma generator  520  via the inlet  523 . In some applications, a reactive gas may also be introduced into the plasma generator  520  via the inlet  523 . The plasma generator dissociates the feed stock comprising fluorine, and any reactive gas that may be present, into reaction products with a plasma. The reaction products may include molecular fluorine, atomic fluorine, carbon compounds, SF 6 , SF 4 , S, and SO 2  in addition to other products. The reaction products exit the plasma generator  520  via outlet  526  and are introduced into the fluorine separator  540  via inlet  544 . The fluorine separator  540  separates fluorine from the reaction products and allows flourine to pass through the fluorine outlet  543 . The fluorine separator  540 , in the embodiment of FIG. 5, also has an unwanted products outlet  546  through which unwanted products are allowed to pass.  
         [0058]    In embodiments in which the fluorine separator  540  of FIG. 5 generates an atomic fluorine flux, further fluorine dissociation is unnecessary and fluorine from the fluorine separator  540  can be introduced into a process chamber  590  via ducts and gas distribution components such as a showerhead. The atomic fluorine may be used in the process chamber  590 , for example, to clean the process chamber.  
         [0059]    In embodiments in which the fluorine separator  540  of FIG. 5 generates a molecular fluorine flux, further fluorine dissociation may be necessary to ensure that fluorine reaches the process chamber  590  in its most effective form. In these embodiments, a second plasma generator  580  may be added to the apparatus  500 . The second plasma generator  580  may again be structurally and functionally similar to the plasma generator  130  described with respect to FIG. 1.  
         [0060]    In such embodiments, molecular fluorine is introduced into the second plasma generator  580  via an inlet  563 . The second plasma generator  580  dissociates the molecular fluorine into atomic fluorine with a plasma. Due to the reactivity of atomic fluorine, it may be preferable to have the output of the second plasma generator  580  closely connected to the process chamber  590 . In one embodiment, for example, the second plasma generator  580  is mounted directly onto the process chamber  590 . In another embodiment, for example, the distance between the second plasma generator  580  and the process chamber  590  is minimized. In a third embodiment, equipment involved in the fluid flow is arranged so that the second plasma generator  580  is the equipment closest to the process chamber  590 .  
         [0061]    [0061]FIG. 6 schematically illustrates an apparatus  600  for generating and recycling fluorine gas in accordance with the invention. The apparatus  600  comprises a plasma generator  620 , a fluorine separator  660 , a means for introducing fluorine compound feedstock  610 , a means for allowing waste products to be exhausted  670 , and a plurality of connections that enable fluorine gas to be recycled. FIG. 6 illustrates an embodiment in which the apparatus  600  is used to generate fluorine for use in a process chamber  640  and to recycle fluorine from the process chamber exhaust.  
         [0062]    The plasma generator  620  in apparatus  600  has an inlet  622  through which fluorine compound feedstock may be introduced. The plasma generator  620 , which is structurally and functionally similar to the plasma generator  130  described with respect to FIG. 1, dissociates the feedstock into the products of dissociation. The plasma generator  620  also has an outlet  624  for the products of dissociation. As illustrated in FIG. 6, the fluorine compound feedstock need not be introduced into the apparatus  600  at the inlet  622 .  
         [0063]    The fluorine separator  660  in apparatus  600  has an inlet  662  and a fluorine outlet  664 . As illustrated in FIG. 6, the inlet  662  may be connected to the outlet  624  of the plasma generator  620  via the process chamber  640 . In other embodiments, the device that is consuming fluorine is interchanged with the plasma generator  620 . The fluorine separator  660  separates fluorine from the other byproducts of the use of fluorine. In some embodiments, such as illustrated in FIG. 6, the fluorine separator  660  also has a waste products outlet  666  that enables byproducts of the fluorine separation to be exhausted from the apparatus  600 . In other embodiments, the apparatus  600  includes a similar outlet near the fluorine separator  660  or at another appropriate location.  
         [0064]    In various embodiments, the fluorine separator  660  is structurally and functionally similar to the condenser  160  described with respect to FIG. 1, the condenser  260  or the membrane separation device  280  described with respect to FIG. 2, or the electrochemical cell  300  described with respect to FIG. 3. In the embodiment illustrated in FIG. 6, the fluorine separator  660  comprises an array of tubes comprising electrochemical cells  300  such as described with respect to FIG. 3. In one embodiment, the fluorine separator  660  is structurally and functionally similar to the fluorine separator  400  described with respect to FIG. 4.  
         [0065]    As illustrated in FIG. 6, the apparatus  600  comprises a connection between the fluorine outlet  664  of the fluorine separator  660  and the inlet  622  of the plasma generator  620 . That connection enables the fluorine produced by the fluorine separator  660  to be recycled. The connection in some embodiments comprises a buffer volume  680 .  
         [0066]    The buffer volume accumulates fluorine so that it may be used at a rate and time different from the rate and time at which it is separated from the chamber exhaust. In the embodiment of FIG. 6, the fluorine produced by the fluorine separator  660  mixes with the feedstock comprising fluorine at a junction  615  prior to reaching the inlet  622  of the plasma generator  620 . Additional gases for use in the apparatus  600 , such as reactive gases, may also be introduced at the junction  615  or the inlet  622  of the plasma generator  620 .  
         [0067]    For recirculation, exhaust is received from the process chamber, fluorine is separated from the gas comprising fluorine with fluorine separator comprising a solid electrolyte, and molecular fluorine is compressed to drive the recirculation process. Additionally, in operation of the apparatus  600  of FIG. 6, feedstock comprising fluorine is received. A reactant gas may also be received. The plasma generator  620  dissociates the feedstock comprising fluorine into a variety of products including atomic fluorine with a plasma. The atomic fluorine is provided to the process chamber  640 . The process chamber  640  uses atomic fluorine, in one embodiment to clean the chamber, and produces exhaust. The fluorine separator  660  separates fluorine from the exhaust. This fluorine is recirculated to the plasma generator  620  for reuse, while the unwanted products that are (at least partially) depleted of fluorine are exhausted from apparatus  600 . Other embodiments may use a plurality of fluorine separators downstream of the process chamber  640 .  
         [0068]    Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims.