Gas separation: processes – Solid sorption – Including reduction of pressure
Reexamination Certificate
2000-05-03
2002-06-18
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Solid sorption
Including reduction of pressure
C095S105000, C095S133000, C095S901000, C095S902000, C096S130000, C096S143000
Reexamination Certificate
active
06406519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to storage and dispensing systems for the selective dispensing of gaseous reagents, e.g., hydride and halide gases, from a vessel or storage container in which the gas component(s) are held in sorptive relationship to a solid sorbent medium, and are desorptively released from the sorbent medium in the dispensing operation. The invention relates more specifically to gas cabinet assemblies containing one or more sorbent-based gas storage and dispensing vessels of such type, coupled to a gas dispensing manifold and/or other flow circuitry, to selectively dispense the gas from the vessel and gas cabinet to a downstream process unit, e.g., a semiconductor manufacturing facility.
2. Description of the Related Art
In the manufacture of semiconductor materials and devices, and in various other industrial processes and applications, there is a need for a reliable source of hydridic and halidic gases. Many of such gases, including for example silane, germane, ammonia, phosphine, arsine, diborane, stibine, hydrogen sulfide, hydrogen selenide, hydrogen telluride, and corresponding and other halide (chlorine, bromine, iodine, and fluorine) compounds, as a result of toxicity and safety considerations, must be carefully stored and handled in the industrial process facility.
The gaseous hydrides arsine (AsH
3
) and phosphine (PH
3
) are commonly used as sources of arsenic (As) and phosphorous (P) in ion implantation. Due to their extreme toxicity and high vapor pressure, their use, transportation and storage raise significant safety concerns for the semiconductor industry. Ion implantation systems typically use dilute mixtures of AsH
3
and PH
3
at pressures as high as 1500 psig. A catastrophic release of these high pressure cylinders could pose a serious injury potential and even death to fab workers.
Based on these considerations, the ion implant user must choose between solid or gas sources for arsenic and phosphorous species. Switching from As to P on an implanter with solid sources can take as long as 90 minutes. The same species change requires only 15 minutes with gas sources. However, arsine (AsH
3
) and phosphine (PH
3
), the two most commonly used source gases, are highly toxic. Their use has recently been the focus of widespread attention due to the safety aspects of handling and processing these gases. Many ion implantation systems utilize hydride gas sources supplied as dilute mixtures (10-15%), in either 0.44 L or 2.3 L cylinders at pressures of 400-1800 psig. It is the concern over the pressure-driven release of the gases from cylinders that has prompted users to investigate safer alternatives.
U.S. Pat. No. 4,744,221 issued May 17, 1988 to Karl O. Knollmueller discloses a method of storing and subsequently delivering arsine, by contacting arsine at a temperature of from about −30° C. to about +30° C. with a zeolite of pore size in the range of from about 5 to about 15 Angstroms to adsorb arsine on the zeolite, and then dispensing the arsine by heating the zeolite to an elevated temperature of up to about 175° C. for sufficient time to release the arsine from the zeolite material.
The method disclosed in the Knollmueller patent is disadvantageous in that it requires the provision of heating means for the zeolite material, which must be constructed and arranged to heat the zeolite to sufficient temperature to desorb the previously sorbed arsine from the zeolite in the desired quantity.
The use of a heating jacket or other means exterior to the vessel holding the arsine-bearing zeolite is problematic in that the vessel typically has a significant heat capacity, and therefore introduces a significant lag time to the dispensing operation. Further, heating of arsine causes it to decompose, resulting in the formation of hydrogen gas, which introduces an explosive hazard into the process system. Additionally, such thermally-mediated decomposition of arsine effects substantial increase in gas pressure in the process system, which may be extremely disadvantageous from the standpoint of system life and operating efficiency.
The provision of interiorly disposed heating coil or other heating elements in the zeolite bed itself is problematic since it is difficult with such means to uniformly heat the zeolite bed to achieve the desired uniformity of arsine gas release.
The use of heated carrier gas streams passed through the bed of zeolite in its containment vessel may overcome the foregoing deficiencies, but the temperatures necessary to achieve the heated carrier gas desorption of arsine may be undesirably high or otherwise unsuitable for the end use of the arsine gas, so that cooling or other treatment is required to condition the dispensed gas for ultimate use.
The present invention contemplates a gas storage and dispensing system, for the storage and dispensing of reagent gases, such as hydride and halide gases, which overcomes the above-discussed disadvantages of the method disclosed in the Knollmueller patent.
The system of the invention is adapted for storage and dispensing of a wide variety of reagent gases, including hydride and halide gases, and is selectively operable at ambient temperature levels, but is able to effectively utilize the high storage (sorptive) capacity of physical adsorbents such as zeolite materials.
SUMMARY OF THE INVENTION
The present invention relates to a gas supply system. The gas supply system includes a gas cabinet defining an enclosure including therein a gas dispensing manifold and one or more adsorbent-based gas storage and dispensing vessels mounted in the enclosure and joined in gas flow communication with the gas dispensing manifold.
The enclosure may be maintained under low or negative pressure conditions for enhanced safety in the event of leakage of gas from the gas storage and dispensing vessel(s) in the enclosure. The gas supply system may be coupled to a downstream gas-consuming unit, such as a process unit in a semiconductor manufacturing facility, e.g., an ion implanter, an etch chamber, a chemical vapor deposition reactor, etc.
The adsorbent-based gas storage and dispensing system constitutes an adsorption-desorption apparatus for storage and dispensing of a gas, e.g., a gas selected from the group consisting of hydride gases, halide gases, and organometallic reagent gases, such as Group V compounds. The adsorption-desorption apparatus comprises:
a storage and dispensing vessel constructed and arranged for holding a solid-phase physical sorbent medium, and for selectively flowing gas into and out of the vessel;
a solid-phase physical sorbent medium disposed in said storage and dispensing vessel at an interior gas pressure;
a sorbate gas physically adsorbed on said solid-phase physical sorbent medium;
a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel, and constructed and arranged to provide, exteriorly of said storage and dispensing vessel, a pressure below said interior pressure, to effect desorption of sorbate gas from the solid-phase physical sorbent medium, and gas flow of desorbed gas through the dispensing assembly;
wherein the solid-phase physical sorbent medium is devoid of trace components selected from the group consisting of water, metals, and oxidic transition metal species (e.g., oxides, sulfites and/or nitrates) sufficient in concentration to decompose the sorbate gas in said storage and dispensing vessel.
In such apparatus, the solid-phase physical sorbent medium contains less than 350, preferably less than 100, more preferably less than 10, and most preferably less than 1, parts-per-million by weight of trace components selected from the group consisting of water and oxidic transition metal species, based on the weight of the physical sorbent medium.
In the apparatus of the invention, the solid-phase physical sorbent medium concentration of trace components selected from the group consisting of water and oxidic transition metal species, based on the weight of the physical sorbent med
McManus James V.
Tom Glenn M.
Advanced Technology & Materials Inc.
Chappuis Margaret
Hultquist Steven J.
Spitzer Robert H.
Zitzmann Oliver A.
LandOfFree
Gas cabinet assembly comprising sorbent-based gas storage... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas cabinet assembly comprising sorbent-based gas storage..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas cabinet assembly comprising sorbent-based gas storage... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2930343