Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture
Reexamination Certificate
1999-08-23
2001-08-21
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
C423S230000, C423S24000R, C095S116000, C095S148000, C095S131000, C095S133000, C095S136000, C206S000600, C206S000700
Reexamination Certificate
active
06277342
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
This invention relates generally to storage and dispensing systems for the selective dispensing of gaseous compounds, in particular hazardous hydride and halide gases, from a storage container in which the gaseous compounds are held in sorptive relationship to a solid sorbent medium, and are desorptively released from the sorbent medium in the dispensing operation.
The semiconductor manufacturing industry uses a number of hazardous specialty gases for doping, etching and thin-film deposition. For example, phosphine (PH
3
) and arsine (AsH
3
) are needed for numerous semiconductor fabrication processes, though their use poses significant safety and environmental challenges due to their high toxicity and pyrophoricity (i.e., spontaneous inflammability in air). The storage and transport of highly toxic or pyrophoric materials as compressed or liquefied gases in metal cylinders is often unacceptable because of the possibility of developing a leak or catastrophic rupture of the container which could lead to injuries or death. It would be preferable to have a reliable source of these gases wherein the gases are maintained at or below atmospheric pressure during shipping and storage. Also, since many semiconductor processes using specialty gases are operated below ambient pressure, positive gauge pressures of these gases may not be needed, even when in use.
In order to mitigate some of these safety issues, on-site electrochemical generation of such gases has been described. See, e.g., U.S. Pat. Nos. 4,178,224, 5,158,656, 5,425,857 and 5,474,659. Because of difficulties in the on-site synthesis of these gases, a better technique has been developed where the gas is physisorbed or chemisorbed on a support, thereby reducing the vapor pressure of the gas to render it safer. For example, U.S. Pat. No. 5,518,528 to Tom et al. discloses such a process wherein PH
3
and AsH
3
are adsorbed on physical sorbent and chemisorbent materials, such as strongly basic adsorbents dispersed in, but not covalently bonded to a support. The strong bases presumably react at the surface with the weakly acidic protons on the hydride gas molecules.
It would be more desirable to have a system where the hazardous specialty gas could be reversibly immobilized by undergoing a chemical reaction with the bulk of the solid sorbent. This approach has the potential for higher sorption capacities compared to the surface adsorption and chemisorption approaches of the prior art. The ability to tune the chemical reactivity of the sorbent also provides far greater control over the equilibrium pressure of the hazardous gas over the solid.
All references cited herein are incorporated herein by reference in their entireties.
BRIEF SUMMARY OF THE INVENTION
The invention addresses at least the aforementioned problems by providing a method for delivering a basic gas, said method comprising:
providing a support comprising at least one polymer sufficiently acidic to protonate said basic gas;
contacting said support with said basic gas, whereby said basic gas is protonated by said at least one polymer and condensed to form a solid salt sorbed by said support; and
deprotonating said sorbed solid salt to regenerate said basic gas, whereby said delivery of said regenerated basic gas is effected,
wherein said basic gas has a proton affinity of less than 866 kJ/mol, and said at least one polymer has a first Hammett acidity value more negative than a second Hammett acidity value of a conjugate acid of said basic gas.
Preferably, the proton affinity of said basic gas is about 607 kJ/mol to about 837 kJ/mol, more preferably from 628 kJ/mol to 795 kJ/mol.
In certain embodiments, the basic gas is a hydride or halide, and/or is selected from the group consisting of silane, germane, phosphine, trifluorophosphine, arsine, stibine, hydrogen sulfide, hydrogen selenide and hydrogen telluride. Preferably, the basic gas is phosphine or arsine.
Preferably, the first Hammett acidity value is from −17 to 6.5, more preferably from −14 to 2, even more preferably from −12.5 to −7. In certain embodiments, the first Hammett acidity value is −12 or more negative than −12.
In certain embodiments, the at least one polymer is selected from the group consisting of polymeric sulfonic acids, polymeric perfluoroalkylsulfonic acids, fluorinated sulfonic acid polymers, cross-linked sulfonated polystyrene-divinylbenzene macroreticular copolymers, carboxylic acid polymers halogenated carboxylic acid functionalized polymers and mixtures thereof.
In certain embodiments, the at least one polymer is selected from the group consisting of polymeric sulfonic acids, polymeric perfluoroalkylsulfonic acids, fluorinated sulfonic acid polymers and mixtures thereof.
In certain embodiments, the at least one polymer is a perfluorinated sulfonic acid represented by the following Formula I:
where m is from 0 to 2, preferably from 0 to 1, n is from 0.0 to 4.0, preferably from 0.0 to 2.0, and x is from 10 to 10,000, preferably from 500 to 5,000.
In certain embodiments, the at least one polymer is a fluorinated sulfonic acid represented by the following Formula II:
where q is from 0.0 to 9.0, preferably from 0.0 to 1.0 and y is from 10 to 10,000, preferably from 500 to 5,000.
In certain embodiments, the at least one polymer is a cross-linked sulfonated polystyrene-divinylbenzene macroreticular copolymer represented by the following Formula III:
where s is from 0.0 to 0.75, preferably from 0.0 to 0.50, more preferably from 0.0 to 0.1, t is from 0.25 to 1.0, preferably from 0.5 to 0.95, more preferably from 0.8 to 0.93, and u is from 0.0 to 0.25, preferably from 0.01 to 0.16, more preferably from 0.07 to 0.09.
In certain embodiments, the solid salt is heated to effect said deprotonating.
In certain embodiments, the solid salt is contacted with a competitive base compound to effect said deprotonating, said competitive base compound having a proton affinity greater than that of said basic gas. In some of these embodiments, the competitive base compound has a proton affinity of at least 866 kJ/mol, and/or is ammonia.
The invention also provides an apparatus adapted to deliver a basic gas according to the aforementioned method, said apparatus comprising:
a container containing said support and adapted to selectively contain said basic gas; and
a valve in fluid communication with said container, and adapted to selectively convey said basic gas into and out of said storage and dispensing vessel.
REFERENCES:
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patent: 5425857 (1995-06-01), Bouchard et al.
patent: 5458674 (1995-10-01), Barsotti
patent: 5474659 (1995-12-01), Cadet et al.
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patent: 5707424 (1998-01-01), Tom et al.
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patent: 6132492 (2000-10-01), Hultquist et al.
patent: 6177058 (2001-01-01), Singh et al.
Portfield, “Inorganic Chemistry” at p. 252, Table 5.6 (Addison-Wesley Publ. 1984). ISBN 0-201-05660-7.
(Olah et al., “Perfluorinated Resinosulfonic Acid (Nalon-H®) Catalysis in Synthesis,” 7Synthesis513 (1986) Jul.
Stull, “Vapor Pressure of Pure Substances Organic Compounds,” 39Ind. Eng. Chem.517-540 Apr. (1947). vol. 39 No. 4.
Brown et al., “Boiling Point Data” in Nist Standard Reference Database No. 69, Eds. Mallard et al., Feb. 1997, National Institute of Standards and Technology, Gaithersburg MD, 20899).
Pearlstein Ronald Martin
Rogers Steven Arthur
Air Products and Chemicals Inc.
Chase Geoffrey L.
Griffin Steven P.
Vanoy Timothy C.
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