Abstract:
For producing ultra pure materials a first station has a porous gas distributor. A material supply supplies material to the porous gas distributor. A gas source supplies gas to the distributor and through the distributor to the material in contact with the distributor. A heater adjacent the porous gas distributor heats and melts the material as gas is passed through the material. Dopant and a treatment liquid is or solid supplied to the material. Treated material is discharged from the first station into a second station. A second porous gas distributor in the second station distributes gas through the material in the second station. A crucible receives molten material from the second station for casting, crystal growing in the crucible or for refilling other casting or crystal growth crucibles. The material and the porous gas distributor move with respect to each other. One porous gas distributor is cylindrical and is tipped. The material supply is positioned above a lower end of the cylindrical porous gas distributor, and the discharge is positioned adjacent an opposite, raised end of the distributor. The cylindrical distributor is tippable for emptying material. Multiple parallel stations discharge multiple materials into a subsequent station or crucible.

Description:
[0001]    This is a continuation-in-part of patent application Ser. No. 09/505,432 filed Feb. 16, 2000, which is a continuation-in-part of Ser. No. 09/392,647 filed Sep. 9, 1999. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates material purification The material can be any material either used in its elemental form, chemical compounds, and their combinations in the form of an alloy. The purified material will be used for product fabrication, casting of various shapes and sizes, as well as raw material for growing crystals.  
           [0003]    Purity of the material and compositional uniformity are some of the most important characteristics in crystal growth and product performance. The quality of final products are controlled at the beginning by carefully purifying, precisely doping and controllably mixing elements to produce crystals and alloys of known quality and predictable characteristics.  
           [0004]    Needs exist for improved purification and treatment of materials in powder and molten and solid states.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides methods and apparatus for ultra purification of materials.  
           [0006]    The present invention provides improvements for precisely controlling purity, quality, uniformity and chemical composition of crystals and alloys.  
           [0007]    Powder is dispensed on a porous gas distributor in a reduced pressure chamber at a first station. Drying and reactive gases flow through the porous distributor and through the powder. Ultra purification takes place by drying and reactive gas treatment. The powder is transferred into a second station. In another embodiment, the temperature of the first part is increased so that melting occurs. Purification continues following melting. The molten material is transferred into a second station, which is a liquid purification chamber, either by conveyor or by gravity directed flow by tilting of the first section. Purification by reactive gas treatment continues. The liquid purification chamber may be placed at a lower position and have volume suitable to accommodate the liquefied material from the first station. The liquid purification chamber is contained within the same or a separate reduced pressure chamber. A pump or pumps withdraw the reactive gas and impurities are thereby carried out of the powdered or molten material. A dopant controller allows for controlling the dopant level, if any.  
           [0008]    When the chamber is filled to a desired level, the liquid material purification process begins. Reactive gases, liquid or solid materials are used during this cycle. This cycle may be a follow-up cycle or parallel cycle to the one for powder purification. Reactive gases are introduced through a porous distributor. When appropriate material properties have been obtained, the liquefied material may be doped and transferred to a third station or chamber, which is a purified liquid-receiving chamber. The third chamber may be at the same level or at a lower level for gravity flow transfer. The third chamber may be either:  
           [0009]    a crystal growth crucible;  
           [0010]    a molten material storage for continuous casting or crystal growth; or  
           [0011]    a chamber for casting the material in certain shapes and sizes.  
           [0012]    All chambers may have tilt mechanisms for providing for easy material transfer from one chamber into the next in controlled flow. All chambers may be in one large vacuum chamber or in separate vacuum chambers that allow for material transfer and handling.  
           [0013]    Several purification stations may feed the cast/refill/crystal grower, either to provide continuous operation or to provide a proper mix of distinct elements or compounds to form molten material for various alloy products. The mixing may be at the beginning or may be continuous to ensure proper element ratio in the alloy and constant dopant level, if any, in the alloy.  
           [0014]    Purification station cascades may be employed for specific applications.  
           [0015]    One purification station has a vacuum chamber containing a cylindrical or other rotating porous gas distributor, a material supply line, a gas supply line, a dopant supply line, a vacuum line, heaters, a tilting mechanism, a rotation mechanism, a liquid dispensing line, a control panel for all of the above, and other control data related issues.  
           [0016]    The material to be purified is supplied through the supply line. After a required quantity has been introduced, the processing of the material begins. Drying and chemical treatment of the material, as well as doping and mixing of all components, is accomplished during this step.  
           [0017]    When the purification has been completed, the material may be transferred to a crystal growth crucible or other applications having need of the purified material.  
           [0018]    The material may be subjected to a melting and purification process in its molten state. If the space allows, more material may be added to achieve a certain melt level in the chamber. When all the material has been melted and outgassed, the purification procedure is conducted. If the final product to be delivered needs dopant, suitable amounts of dopant and reactive materials are added to the melt. The rotation of the chamber containing the material provides for proper mixing of the reactive materials and/or the dopant.  
           [0019]    When the material has the desired properties, it is delivered to a casting station or to a refilling station, or directly to a crystal grower for batch or continuous crystal growth.  
           [0020]    Multiple cascade purification stations may be employed to achieve increased levels of purity of single elements or single compounds, or to form special alloys and to maintain desired single element quality, single compound quality and/or alloy quality and composition.  
           [0021]    The purification station cascade can be enclosed in one vacuum chamber, or each station can be enclosed in a separate vacuum chamber. Means of material transfer are used to move material from one station to another or to an application such as crystal grower, casting station or other not specified application.  
           [0022]    Purification station cascades may be used in the Pandelisev Crystal Grower (U.S. Pat. No. 5,993,540) or in a Standard Bridgman-Stockbarger approach, or in a Bridgman-Stockbarger process employing an embedded purification station.  
           [0023]    Embedded purification station cascade consisting of plurality of purification stations may be considered for certain applications. They can be all housed in a separate vacuum chambers and will have the capability to communicate the material from one station to another in a controlled manner. Or they can be placed one adjacent to another in horizontal or vertical or semi-vertical arrangement within a large vacuum chamber or within the chamber of crystal grower having Bridgman-Stockbarger or Pandelisev (continuous or batch type) crystal grower.  
           [0024]    The invention provides methods and apparatus for producing ultrapure materials. The first station has a chamber and a porous gas distributor in the chamber. The chamber may be elliptical, hexagonal and may be rectangular or have conical or truncated cone shape. A material supply supplies material to the chamber. A gas source connected to the porous distributor supplies gas to the distributor and through the distributor to the material in contact with the distributor. A heater(s) adjacent to the chamber heats the material as gas is passed through the material. One or more discharge ports on the bottom and/or the sides of the chamber discharges the treated material from the first station into a second purification station, material storage or to crystal growth crucible for continuous or batch type growth of single crystal or casting applications. A dopant controller supplies/controls the dopant levels of the material. A treatment liquid or solid supply supplies treatment liquid or solid to the material.  
           [0025]    A second station is positioned adjacent or under the discharge of the first station. The second station has a chamber and a porous gas distributor in the chamber. The chamber may have elliptical. hexagonal and may be rectangular of having conical or truncated cone shape. Through the discharge port(s) of the first station material is supplied to the second chamber. A gas source connected to the porous distributor supplies gas to the distributor and through the distributor to the material in contact with the distributor. A heater(s) adjacent to the chamber heats the material as gas is passed through the material. One or more discharge ports on the bottom and/or the sides of the chamber discharges the treated material from the first station into a second purification station. material storage or to crystal growth crucible for continuous or batch type growth of single crystal or casting applications. A dopant controller supplies/controls the dopant levels of the material. A treatment liquid or solid supply supplies treatment liquid or solid to the material.  
           [0026]    A third purification station, material storage or a crystal growth crucible for continuous or batch-type growth of single crystal or casting applications may be placed adjacent or under the second station.  
           [0027]    Multiple first stations may discharge multiple materials into a second station. Multiple second stations may discharge molten material into the third station crucible.  
           [0028]    These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 shows a cascaded purification apparatus within a vacuum chamber.  
         [0030]    [0030]FIG. 2 shows a rotating purification apparatus.  
         [0031]    [0031]FIG. 3 shows stacked purification stations.  
         [0032]    [0032]FIG. 4 shows stacked purification stations embedded in a Bridgman-Stockbarger system.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Referring to FIG. 1, a purification system is generally indicated by the numeral  1 . A vacuum chamber  3  surrounds the apparatus. Alternatively, individual vacuum chambers may surround each element of the apparatus.  
         [0034]    A porous gas distributor  5  is positioned above a conveyor  7 . A gas inlet tube  9  with valves  11  and  12  controls gas that is provided through the porous gas distributor. The distributor  5  may be a porous plate, a series of porous plates, tubes or poles or a porous grid.  
         [0035]    A material supply  13  contains a powdered starter material  15 . A valve  17  and dispenser  19  form a layer  21  of the powdered material on the conveyor  7 . The powdered material moves along the porous gas distributor  5  as the conveyor moves. A heater  23  heats the powdered material while the chamber is evacuated and gas is distributed through the material to outgas and treat the material and to purify the material.  
         [0036]    An example of the gas that might be distributed through distributor  5  is an inert gas or a reactive gas such as vapors of various reactants mixed with inert gas. For example, argon may be bubbled through an acid to carry some of the acid vapors through the porous gas distributor and through the material. The heater  23  may be incrementally raised in temperature towards the discharge end  25  of the conveyor  7  so that liquid molten material  27  is discharged from the first station  29 .  
         [0037]    A dopant supply  31  with a dopant injector  33  is supplied at the first station  29  to supply dopant material to the powdered or molten material.  
         [0038]    In the second stage  35 , molten material  37  is maintained in a liquid condition by heaters  39 . Dopant  41  is supplied through director  43  to the molten material as required. The porous plate  45  is connected to the gas supply  8  to supply purification gases through the porous gas distributor  45  and to bubble the gases through the molten material  37 .  
         [0039]    When the material is ready for discharge, valve  47  on discharge line  49  is opened, and the molten material is flowed to a crucible  51 . Heaters  53  maintain the temperature of the liquid above the melting temperature, and porous gas distributor  55  is connected to a gas supply  10  to bubble reactive gas through the molten material  57  in the crucible  51 . The crucible  51  may be used for casting or crystal growth, or as a supply of molten material to a grower or casting apparatus.  
         [0040]    Dopant or reactive liquid or solids may be supplied from source  61  through tube  63  to the molten material  57  within the crucible  51 . Heater  65  may be used to open and close the valve  47  to flow molten material  37  from second station  35  into the crucible  51 .  
         [0041]    Several first and second stations may be used to supply one crucible  51  so that the material from different stations may be mixed. Alternatively, several first stations may supply a second station in which the molten material is mixed before the molten material is released to the crucible  51 .  
         [0042]    Referring to FIG. 2, a relatively movable porous gas distributor  71  moves with respect to a crucible  73 . Either the crucible or the porous gas distributor may oscillate, both may oscillate, or one or both may rotate with respect to the other. As shown in FIG. 2, the porous gas distributor rotates within the crucible. The porous gas distributor  71  and the crucible  73  have openings for admitting or discharging the crystal material. Alternatively, the porous gas distributor  71  is formed with radial ribs on its sides  75  or longitudinal slats  77  or paddles on its cylindrical sides, so that the material may freely flow into and out of the porous gas distributor cylinder. Gas supplies  79  extend through gimbals (not shown) that support the porous gas distributor for oscillation or rotation with respect to the crucible  73 . The longitudinal slats  77  may be shaped in such a way as to give the best stirring effect. For example, the slats may be formed as paddles or foils or may be inclined to provide mixing of the powder and molten material within the crucible.  
         [0043]    Insulation  81  surrounds the crucible, and a heater  83  is embedded in the insulation to maintain the crucible at the desired temperature for treatment of the material. Material is supplied from a supply  85  through a valve  87  and a distributor  89 . Dopant or treatment liquid or solid may be supplied from supply  91  through treatment tube  93 .  
         [0044]    A vacuum line  95  and valve  96  are connected to the chamber  97  to maintain vacuum within the vacuum chamber  97 . Gas piping  80  and valves  82  are connected to the initial stage  111  for supplying or venting gas from the initial stage. The discharge line  99  and a valve  101  control discharge of the treating material into a holding crucible  103 , where it is held in molten form  105  by heaters  107  within a vacuum chamber  109 .  
         [0045]    One or more of the initial stages  111  may be connected to supply the crucible  103  with distinct materials to form alloys.  
         [0046]    The crucible  103  is used as a molten supply to supply crystal growers or casting apparatus for crystals, or the crucible  103  may be the crystal growth crucible itself.  
         [0047]    [0047]FIG. 3 shows stacked purification stations  121 . The stack  121  has at least one station; FIG. 3 shows three stations  123 ,  125  and  127 . All the stations  123 ,  125  and  127  and the crucible  129  may be contained in one vacuum chamber  131 . Alternatively, separate vacuum chambers may be used for each station and the crucible. Alternatively, as shown in FIG. 3, the stations  123 ,  125  and  127  may be contained within one vacuum chamber  131 , while the crucible  129  is outside the vacuum chamber.  
         [0048]    The stacked stations  121  are inside or outside the crystal grower  129  for continuous shaped crystal growth, continuous plate growth, casting chamber growth, or crucible batch plate growth. The stacked stations are suitable for stand alone units that are used for refill of any type of crystal growth system, material casting system, or the like.  
         [0049]    The gas supply  133  and the reactive gas supply  135  come from the top of the main crucible, as shown in FIG. 3, and may have multiple entry ports in the porous distributors. Each chamber may be connected to one or more than one reactive gas or inert gas sources. Each station may have its own independent gas line circuit, sources, and valves. Reactive gas may flood the whole vacuum chamber.  
         [0050]    As shown in FIG. 3, valves  137  and  139  outside the vacuum chamber  131  control the supply of gas and reactive gas. Reactive gas supply  135  supplies the porous distributors  141 ,  143  and  145  of each station  123 ,  125  and  127  individually. The gas supply  133  floods the entire chamber  131 . Vacuum inlet  171  and valve  173  are used to create and maintain a vacuum in the chamber  131 .  
         [0051]    A purification station  123 ,  125  and  127  may have an open top, or a lid. The purification station  131  may be independently heated, or it may be heated by a common heating assembly. As shown in FIG. 3, each purification station has its own heating assembly  179 ,  181  and  183 . Alternatively, one heating assembly may be used to heat the entire chamber  131 .  
         [0052]    The plug assembly and the transfer tube with valve has a tube with a plug and a heater controlled shut-off valve. The purification chamber might have more than one plug assembly or valve. The material transfer may be through openings  147 ,  149  and  151  on the bottom or sides of the stations. As shown in FIG. 3, material transfer may also be accomplished through the use of discharge tubing  175  located on the side of a purification station. A valve  177  may be used to control the discharge of material through the discharge tubing  175 . Plug assemblies  153 ,  155  and  157  may be used to control transfer of material through the openings to the next purification station. The transfer may be facilitated by gravity or by other means, such as a suction transfer or a similar method.  
         [0053]    The dopant controller may provide various dopants, and the means for controlling their concentrations. This port may also be used to provide purification reactive material in both liquid and solid form. As shown, each purification station may have its own dopant distributor  159 ,  161  and  163 .  
         [0054]    Material is provided to the first purification station  123  from a material distributor  165  through supply  167 . A valve  169  may be used to control the flow of the material. The material to be purified may be in any liquid or in any solid.  
         [0055]    [0055]FIG. 4 shows a stacked purification station  201  embedded in a Bridgman-Stockbarger system. The stack  201  has at least one station; FIG. 4 shows three stacked purification stations  203 ,  205  and  207 . As shown in FIG. 4, all the stations  203 ,  205  and  207  and the crucible  209  are contained in one vacuum chamber  211 . Alternatively, separate vacuum chambers may be used for each station and the crucible. The stacked stations  203 ,  205  and  207  are inside or outside the crystal grower  209  for continuous shaped crystal growth, continuous plate growth, casting chamber growth, or crucible batch plate growth. The stacked stations are suitable for stand alone units that are used for refill of any type of crystal growth system, material casting system, or the like.  
         [0056]    An embedded purification station may consist of a heater surrounded (from one or all sides) porous distributor. In that case the feed material and dopant, if any, will be added directly to the crucible. That kind of an arrangement will be excellent for purification and melt solid interface stabilization in Bridgman-Stockbarger configuration. One or more purification stations having this geometry or the chamber type described earlier can be used. The height of each station, as well as their cross-section, can vary depending on the particular application.  
         [0057]    The gas supply  213  and the reactive gas supply  215  come from the top of the main crucible  209 , as shown in FIG. 4, and may be controlled through the use of valves  217  and  219  on the gas supplies. The gas supplies  213  and  215  may have one inlet, as shown in FIG. 4, or multiple entry ports into the porous distributors  219 ,  221  and  223  of the purification stations  203 ,  205  and  207 . Each purification station may be connected to one or more than one reactive gas or inert gas sources. Each station may have its own independent gas line circuit, sources, and valves. Gas or reactive gas may flood the whole vacuum chamber  211 . Vacuum inlet  257  and valve  259  are used to create and control a vacuum in the chamber  211 .  
         [0058]    A purification station  203 ,  205  and  207  may have an open top, or a lid. The purification station may be independently heated, or it may be heated by a common heating assembly. FIG. 4 shows independent heaters  227 ,  229  and  231  for the purification stations  203 ,  205  and  207 .  
         [0059]    The plug assembly and the transfer tube with valve has a tube with a plug and a heater controlled shut-off valve. Each purification station may have more than one plug assembly or valve. The material transfer may be through openings  233 ,  235  and  237  on the bottom or sides of the stations. Plug assemblies  239 ,  241  and  243  may be used to control transfer of material through the openings to the next purification station. The transfer may be facilitated by gravity or by other means, such as a suction transfer or a similar method.  
         [0060]    The dopant controller may provide various dopants, and the means for controlling their concentrations. This port may also be used to provide purification reactive material in both liquid and solid form. As shown, each purification station may have its own dopant distributor  245 ,  247  and  249 .  
         [0061]    The material to be purified may be in powder, liquid or solid form. The purified material may be a powder, a liquid, or a solidified material, or in any combination thereof. Material is provided to the first purification station  203  from a material distributor  251  through supply  253 . A valve  255  may be used to control the flow of the material.  
         [0062]    The solidified material portion may polycrystalline material, or it may be a single crystal.  
         [0063]    The material may be any liquid substance, and any solid substance made from one or more chemical elements.  
         [0064]    The material being processed may have several forms. For example, the material being purified is a single crystal, polycrystalline material or powder material.  
         [0065]    The material being purified may have uniform material properties over the entire body, or may have desired composition within certain sections of the body.  
         [0066]    In preferred embodiments, the material being purified may be alkali halide material, sodium iodide, cesium iodide, calcium fluoride or barium fluoride. In one preferred embodiment, the material purified may be silicon, silicon and germanium, Si x Ge 1−x  solid solution, silicon and silicon carbide Si x (SiC) 1−x , silicon and silicon dioxide Si x (SiO 2 ) 1−x , silicon and any ceramic, silicon and any oxide Si x (oxide) 1−x , silicon and any metal Si x M 1−x , silicon and any alloy Si x A 1−x , any combination therebetween. The material purified may be mixed with organic and/or inorganic substances to form a slurry, or solid substance in form of powder, shot or any size and shape material suitable for the process. The material purified may preferably be any substance for making elements for wafer processing and wafer processing equipment.  
         [0067]    The material purified may preferably be any substance containing silicon or silicon compound for making elements for wafer processing and wafer processing equipment.  
         [0068]    The product produced by further processing the material may be a wafer boat or any process chamber element.  
         [0069]    The product produced by further processing the material may be a wafer or other process chamber or part of a wafer or other process chamber. The product produced by further processing the material may be a scintillator. The material being processed may be doped or undoped sodium iodide or Cesium iodide. The material being processed may be a composite of many compounds, and the end product a scintillator, or an optical lens material.  
         [0070]    The material being processed may be any substance for making optical elements. The material processed may be any scintillation oxide material.  
         [0071]    In the environment for the material processing, the processing and heat treatment may be in vacuum. The processing and heat treatment may be in reduced pressure of one or more inert gases, or of one or more reactive gases. The processing and heat treatment may be in reduced pressure of one or more reactive and inert gases, of one or more inert and reactive gas mixtures. The processing and heat treatment may be in desired pressures of one or more inert and/or reactive gas mixtures suitable for the process and product being made.  
         [0072]    Reactive gases or reactive substances can be chemical compounds that react with the substance being purified. The reactive substance can be gaseous, liquid or solid elements or compounds.  
         [0073]    The reactive substance can be an elemental gas or an organic or inorganic gaseous compound in its neutral or ionized state. The reactive substance can be elemental gas or organic or inorganic gaseous compound mixture in its neutral or ionized state. The reactive substance can be elemental gas or organic or inorganic gaseous compound mixture in its neutral or ionized state mixed with a carrier gas.  
         [0074]    The reactive gas can be fluorine gas, F 2 . The reactive gas can be fluorine gas, F 2 , mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0075]    The reactive gas can be fluorine gas, F 2 , in its atomic state mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0076]    The reactive gas can be fluorine gas, F 2  in its atomic state obtained via chemical reaction and/or passing fluorine gas through a ion generator.  
         [0077]    The reactive gas can be fluorine gas, F 2 , in its atomic state obtained via chemical reaction and or passing fluorine gas through an ion generator mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form. The ion generator can be a plasma generator.  
         [0078]    The reactive gas can be fluorine gas, F 2 , in its molecular and atomic state obtained via chemical reaction and/or passing fluorine gas through a plasma generator where only part of the gas is dissociated into atoms or where some of the atoms recombine after the ionization and form neutral molecules.  
         [0079]    The reactive gas can be fluorine gas, F 2  in its molecular and atomic state obtained via chemical reaction and or passing fluorine gas through a plasma generator, where only part of the gas is dissociated into atoms or where some of the atoms recombine after the ionization and form neutral molecules mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0080]    In some embodiments, the reactive gas is a mixture between fluorine atoms and fluorine molecules obtained through two different sources and combined for purification purposes. The reactive gas is a mixture between fluorine atoms and fluorine molecules obtained through two different sources and combined for purification purposes mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form. The reactive gas is a mixture between fluorine atoms, fluorine molecules and other fluorine organic or inorganic molecules in neutral or charged state.  
         [0081]    In other embodiments, the reactive gas is a mixture between fluorine atoms, fluorine molecules and other fluorine organic or inorganic molecules in neutral or charged state mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form. The reactive gas is a mixture between fluorine atoms, fluorine molecules and other fluorine organic or inorganic molecules in neutral or charged state and/or their ions created by passing them through an ionization apparatus. The reactive gas is a mixture between fluorine atoms, fluorine molecules and other fluorine organic or inorganic molecules in neutral or charged state or their ions created by passing them through an ionization apparatus mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0082]    The reactive gas can be carbon tetrafluoride, CF 4 . The reactive gas can be carbon tetrafluoride gas, CF 4 , mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0083]    The reactive gas can be fluorine gas, F2, fluorine in its atomic state and CF 4 .  
         [0084]    The reactive gas can be fluorine gas, F2, fluorine in its atomic state and CF 4  mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form. The reactive gas can be CF 4  gas, ionized CF 3  radicals, and fluorine in its atomic and molecular state obtained via chemical reaction and or passing fluorine gas through a ion generator.  
         [0085]    The reactive gas can be CF 4  gas, ionized CF 3  radicals, and fluorine in its atomic and molecular state obtained via chemical reaction and or passing fluorine gas through a ion generator mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form. The ion generator can be a plasma generator.  
         [0086]    In some embodiments, the reactive gas is a mixture between fluorine atoms, and CF 4  molecules obtained through two different sources and combined for purification purposes.  
         [0087]    The reactive gas is a mixture between fluorine atoms, fluorine molecules and CF 4  obtained through two different sources and combined for purification purposes mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0088]    The reactive gas is a mixture between carbon tetrafluoride, carbon tetrafluoride radicals such as CF 3  or other, fluorine atoms and molecules and other fluorine organic or inorganic molecules in neutral or charged state.  
         [0089]    The reactive gas is a mixture between carbon tetrafluoride, carbon tetrafluoride radicals such as CF 3  or other, fluorine atoms and molecules and other fluorine organic or inorganic molecules in neutral or charged state mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0090]    The reactive gas is a mixture between carbon tetrafluoride, carbon tetrafluoride radicals such as CF 3  or other, fluorine atoms and molecules and other fluorine organic or inorganic molecules in neutral or charged state and/or their ions created by passing them through an ionization apparatus.  
         [0091]    The reactive gas is a mixture between carbon tetrafluoride, carbon tetrafluoride radicals such as CF 3  or other, fluorine atoms and molecules and other fluorine organic or inorganic molecules in neutral or charged state and/or their ions created by passing them through an ionization apparatus mixed with carrier gas that can be any inert gas or any suitable inorganic or organic compound in gaseous form.  
         [0092]    While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.