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  Method of recycling fluorine using an adsorption purification processUSPTO Application #: 20060042462Title: Method of recycling fluorine using an adsorption purification process Abstract: A method and apparatus is disclosed for producing fluorine by providing a contained fluorine precursor source located proximate to or remotely from an adsorbent bed, optionally in a replaceable unit that may be a replaceable module comprising both the fluorine source and the adsorbent bed. Fluorine derived preferably from a nitrogen trifluoride source and used to remove deposited silicon-containing impurities in reaction chambers is reclaimed from an adsorbent bed, and made available to the reaction chamber as a supplemental fluorine source to reduce the total required amount of nitrogen trifluoride source gas. The separation column adsorbent is regenerated in cyclical intervals using a reverse flow of inert gas. (end of abstract)
Agent: David A. Hey The Boc Group, Inc. - Murray Hill, NJ, US Inventors: Edward Frederick Ezell, Richard A. Hogle, Walter H. Whitlock, Graham A. McFarlane USPTO Applicaton #: 20060042462 - Class: 095047000 (USPTO) Related Patent Categories: Gas Separation: Processes, Selective Diffusion Of Gases, Selective Diffusion Of Gases Through Substantially Solid Barrier (e.g., Semipermeable Membrane, Etc.), Nitrogen Or Nitrogen Containing Compound Permeates Barrier The Patent Description & Claims data below is from USPTO Patent Application 20060042462. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present application relates to the field of gas purification and recycling. More specifically, the present invention relates to the use of recycled fluorine to supplement nitrogen trifluoride for cleaning chamber surfaces, and the purification and recycling of fluorine gas. BACKGROUND OF THE INVENTION [0002] Semiconductor chip manufacturers have long recognized the deleterious effects of deposits, such as, for example, oxide deposits on the reaction chamber walls in which the various chemical reactions and deposition processes take place during chip manufacture. As impurities build up on reaction chamber surfaces, such as interior chamber walls, the risk increases that such impurities may be co-deposited on target work piece surfaces, such as computer chips. Therefore, such chambers must be periodically cleaned during down cycles in the chip manufacturing process. [0003] One known way to clean the unwanted deposits from interior reaction chamber walls is to produce a fluorine plasma in the reaction chamber, under sub-atmospheric pressure, to remove unwanted silicon-containing oxide deposits from the interior chamber walls. While diatomic fluorine (F.sub.2) is an excellent candidate as a source for the fluorine plasma, it is highly reactive. Therefore, the fluorine plasma can be more safely obtained by dissociating other fluorine-containing compounds such as, for example, NF.sub.3, CF.sub.4, C.sub.2F.sub.6, SF.sub.6, etc. In essence, any fluorine-containing gas that can be decomposed into active fluorine species potentially can be used for chamber cleaning. [0004] Nitrogen trifluoride (NF.sub.3) has proven to be an extremely safe, useful and versatile source of elemental fluorine for reactions, and for use in apparatus cleaning protocols. However, the dramatic surge in demand for NF.sub.3 has resulted in a virtual global shortage of this relatively expensive material. In addition, most of the cleaning processes using NF.sub.3 only consume about 15% of the fluorine contained within the NF.sub.3 in the actual cleaning operation, with the remaining fluorine being exhausted, treated, neutralized and eventually discarded. [0005] Cyclical adsorption processes are generally employed for use in fluorine recycling processes. Such preferred processes include pressure swing adsorption (PSA) and temperature swing adsorption (TSA) cycles, or combinations thereof. The adsorption can be carried out in an arrangement of two or more adsorption beds arranged in parallel and operated out of phase, so that at least one bed is undergoing adsorption while another bed is being regenerated. Specific fluorine recycle applications into which the invention can be incorporated include vacuum vapor deposition and etching chamber cleaning processes, etc. [0006] The fluorine-containing source compound, any other reagents, and inert gases used in the chamber cleaning process are typically supplied as compressed gases and are admitted into the chamber using a combination of pressure controllers and mass flow controllers to effect the cleaning process. The cleaning process itself requires that a plasma be maintained upstream of, or in the chamber to break up the fluorine-containing source compound so that active fluorine ions and radicals are present to perform the cleaning chemistry. To maintain the plasma, the chamber is kept at a low pressure, typically between about 1 and 10 Torr absolute, by using a vacuum pump to remove the gaseous waste products and any unreacted feed gases that comprise the exhaust gas. The pressure in the chamber is typically controlled by regulating the flow of exhaust gas from the chamber to the chamber pump using a vacuum throttle valve and feedback controller to maintain the chamber pressure at he desired setpoint. The chamber cleaning operation is performed intermittently between deposition operations. Typically, one to five deposition operations will be performed between every chamber cleaning operation. [0007] In typical reaction chamber cleaning apparatuses the reaction gases are NF.sub.3 and argon. Typically the NF.sub.3 is dissociated into nitrogen and energetic fluorine radicals. However, the unused radicals recombine to form fluorine, which is directed from the system as waste and exhausted, such as to a facility abatement device. [0008] It would be advantageous to reclaim a portion of the fluorine waste by purifying the fluorine, discarding the impurities in the waste stream and then return the fluorine for use in the cycle. However, traditional packed column separation techniques have proven unsuitable or unreliable for use with fluorine. Fluorine's high degree of reactivity and instability makes a successful adsorbent selection (for use as adsorbent packing within a separation column) extremely difficult. The adsorbent will combust, or otherwise adversely react prematurely and unpredictably unless the materials used to make the column and the adsorbent bed are made to be non-reactive with fluorine, or are protected by a stable fluoride layer. Traditional steel columns are often too reactive, and plastic vessels and beds combust easily. Silica gels and molecular sieves are also unsuitable for fluorine separation due to their lack of stability when exposed to fluorine. SUMMARY OF THE INVENTION [0009] In one embodiment, the present invention relates to a method for recycling fluorine from a waste stream by providing a process chamber having an inner surface, said surface having contaminants and providing a stream of fluorine-containing gas from a flowing gas source into the process chamber. The contaminants are contacted with the fluorine-containing gas and removed from the process chamber inner surface to create a waste stream. The waste stream is directed from the process chamber to a purification chamber comprising an adsorption bed containing an adsorbent that adsorbs contaminants in the waste stream in the purification chamber. The waste stream is converted into a recycled fluorine source stream and directed from the purification chamber to the process chamber as a supplemental fluorine source stream. [0010] In another embodiment, the present invention is directed to a method for cleaning impurities from an inner surface of a reaction chamber by providing a process chamber having impurities on an interior surface and directing a flow of a fluorine-containing compound to the process chamber from a fluorine-containing source. The fluorine from the fluorine-containing compound is dissociated with the fluorine associating with the impurities on the interior surface of the process chamber. The fluorine is directed along with the associated impurities from the process chamber to a purification chamber, said cleaning chamber containing an amount of adsorbent onto which the impurities are adsorbed. The purified fluorine is directed from the purification chamber to the process chamber to supplement the fluorine-containing source. [0011] In yet another embodiment, the present invention relates to a method for adsorbing impurities from a fluorine-containing stream in an adsorbent bed by directing a flow of a fluorine-containing compound to a process chamber having an inner surface with impurities deposited on the inner surface and dissociating the fluorine from the fluorine-containing compound, to associate with the impurities in the process chamber. The fluorine with impurities is directed from the process chamber to a purification chamber that contains an amount of adsorbent for adsorbing the impurities onto the adsorbent. The purified fluorine is directed from the purification chamber to a fluorine storage tank. [0012] In addition, the present invention is directed to an apparatus for cleaning impurities from a reaction chamber having a process chamber having at least one inlet and one waste stream outlet, the inlet in fluid communication with a source of fluorine; a waste stream for directing a fluorine-containing compound and impurities from the process chamber in fluid communication with the process chamber; and a purification chamber having an inlet and an outlet, the purification chamber inlet in fluid communication with the waste stream outlet and preferably located downstream from the process chamber, the purification chamber comprising an amount of adsorbent, with the purification chamber outlet in fluid communication with a pathway for directing purified fluorine from the purification chamber to the process chamber. [0013] In a still further embodiment, the present invention is directed to a method for producing fluorine by providing a contained fluorine precursor source located proximate to an adsorbent bed in a replaceable unit, an electrolytic cell comprising an electrode, said cell charged with an amount of electrolyte and a power supply. Current is directed from the power supply to the electrolytic cell and then the fluorine precursor is directed to the electrolytic cell. An amount of impure fluorine is collected from the electrolyte of the electrolytic cell and directed to the adsorbent bed where impurities are absorbed from the impure fluorine on the adsorbent in the adsorbent bed while directing newly produced, purified fluorine from the adsorbent bed. [0014] In yet another embodiment, the present invention is directed to an apparatus for producing purified fluorine comprising a replaceable module, said module comprising a fluorine precursor source and an adsorbent bed chamber having an adsorbent bed. The chamber is located proximately to the fluorine precursor source. The chamber and the fluorine precursor source are in communication with an electrolytic cell for producing fluorine gas. [0015] In still further embodiments, the present invention is directed to incorporating a replaceable module comprising a fluorine precursor source and an adsorbent chamber for the production of fluorine to be directed to the aforementioned processing chamber having at least one inlet and one waste stream. [0016] In one embodiment, the present invention is directed to a chamber cleaning process that incorporates in situ, real-time purification and recycling of fluorine-containing gases, and that results in a diminished use of NF.sub.3. The present methods and apparatuses can be used to recycle the unused active fluorine species regardless of the original reagent chemical used. [0017] In a further embodiment, the present invention is directed to an adsorbent material comprising CF.sub.x (wherein x is from about 0.9 to about 1.2), and polytetrafluoroethylene (PTFE) in a ratio of about 9:1 (CF.sub.x:PTFE). In a further embodiment, an amount of pore-forming material is added to the composition. [0018] In another embodiment, the present invention is directed to a method for recycling fluorine from a waste stream. A process chamber is provided with a waste stream in fluid communication with a purification chamber, said waste stream comprising a fluorine-containing mixture containing impurities. A purification chamber is provided in fluid communication with the waste stream. The purification chamber is packed with an amount of CF.sub.x adsorbent in a separation zone, wherein x is from about 0.9 to about 1.2. The waste stream is directed from the process chamber to the purification chamber, and an amount of fluorine is separated from the fluorine-containing mixture in the purification chamber. The impurities in the waste stream are adsorbed on the CF.sub.x adsorbent in the purification chamber, and the purified fluorine is directed from the purification chamber to a storage tank, or sent directly into the process chamber. Efficient adsorption of the impurities to be captured on the CF.sub.x preferably occurs in the temperature range of from about -150.degree. C. to about 20.degree. C., more preferably from about -80.degree. C. to about 10.degree. C., and most preferably from about 40.degree. C. to about -10.degree. C. Further, the desired efficient adsorption of the impurities on the CF.sub.x preferably occurs in the pressure range of from about 300 torr to about 2000 torr, and more preferably from about 500 torr to about 1200 torr. [0019] In still another embodiment, the present invention is directed to a method for cleaning impurities from an inner surface of a reaction chamber. A reaction chamber, or process chamber is provided having impurities on an interior surface, and a flow of a fluorine-containing compound is directed to the process chamber from a fluorine-containing source. The fluorine is dissociated from the fluorine-containing compound, said fluorine associating and reacting with the impurities on the interior surface of the reaction chamber. The fluorine and impurities are directed out of the reaction chamber, preferably under vacuum, to a cleaning chamber, said cleaning chamber packed with an amount of CF.sub.x adsorbent, wherein x is from about 0.9 to about 1.2, and the CF.sub.x comprises an amount of PTFE. The impurities are adsorbed onto the CF.sub.x thereby releasing, purified fluorine from the adsorbent bed The purified fluorine is eventually directed from the purification chamber to the process chamber to supplement the fluorine-containing source in the process chamber. Efficient adsorption of the impurities to be captured on the CF.sub.x adsorbent preferably occurs in the temperature range of from about -150.degree. C. to about 20.degree. C., more preferably from about -80.degree. C. to about 10.degree. C., and most preferably from about -40.degree. C. to about -10.degree. C. Further, the desired efficient adsorption of the impurities on the CF.sub.x preferably occurs in the pressure range of from about 300 torr to about 2000 torr, and more preferably from about 500 torr to about 1200 torr. [0020] Further, the present invention is directed to a method for adsorbing impurities from a fluorine-containing stream in a regenerated adsorbent bed. A flow of fluorine-containing compounds from a fluorine-containing source is directed to a process or reaction chamber. The fluorine is dissociated from the fluorine-containing compound. The fluorine associates and reacts with the impurities in the processing chamber, for example, on the interior surface of the processing chamber. The fluorine, commingled with impurities, is directed to a purification chamber containing an amount of CF.sub.x adsorbent, wherein x is from about 0.9 to about 1.2 and the CF.sub.x comprises an amount of PTFE. The impurities are adsorbed onto the CF.sub.x and the liberated, purified fluorine is directed from the purification chamber to a fluorine storage tank. To accelerate regeneration of the CF.sub.x adsorbent bed in the purification chamber during off-cycle (when the process chamber is not being cleaned), a flow of inert gas is preferably directed through an inlet into the cleaning chamber, and the adsorbed impurities and inert compounds are removed from the CF.sub.x and exhausted from the purification chamber. [0021] Still further, the present invention is directed to an apparatus for cleaning impurities from a process chamber having at least one inlet and one waste stream. The process chamber inlet is in fluid communication with a source of fluorine. A waste stream for directing a fluorine-containing compound and impurities from the process chamber are both in fluid communication with the process chamber and a purification chamber. The purification chamber has an inlet and an outlet, the inlet being in fluid communication with the waste stream, and located downstream from the process chamber. The purification chamber comprises an amount of CF.sub.x combined with an amount of PTFE, preferably in a wt % ratio of about 9:1 (CF.sub.x:PTFE) as an adsorbent for the impurities, wherein x is from about 0.9 to about 1.2, with the purification chamber column outlet in fluid communication with a pathway for directing purified fluorine from the purification chamber to the process chamber. Continue reading... Full patent description for Method of recycling fluorine using an adsorption purification process Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of recycling fluorine using an adsorption purification process patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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