Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1990-12-03
1993-05-25
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
422171, 423210, 423240S, 423241, B01D 5300, B01D 5334
Patent
active
052137678
DESCRIPTION:
BRIEF SUMMARY
The purpose of the invention is to convert certain hazardous gaseous effluents by chemical reactions into safer solid or gaseous products. Preferably the chemical reagents used are solids and hence reduce the risk of carry-over contamination from the gas conditioning equipment. The solid chemical reagents used are easier and safer to handle than liquid reagents. The solid reagents lend themselves readily to encapsulation in exchangeable cartridges.
The gaseous effluents can be the gases that come from etching of semi-conductor devices or from PECVD (Plasma Enhanced Chemical Vapour Deposition) on to semi-conductor materials: similar gases and vapours are used in several stages of manufacture in the semi-conductor manufacturing process. The effluent gases (and vapours) from reactive ion etching and plasma etching include Chlorine, Silicon tetrachloride, Copper chloride (CuCl), Aluminium Chlorides (i.e. AlCl.sub.3), Silicon tetraflouride, trifluoromethane (CHF.sub.3), Carbonyl fluoride (COF.sub.2), Carbonyl chloride (COCl.sub.2), Boron trichloride (BCl.sub.3), Boron tribromide (BBr.sub.3), Hydrogen chloride (HCl), Carbon tetra-chloride (CCl.sub.4), chlorofluoro carbon gases and others.
Additional gases and vapours that are sometimes found in the effluent of PECVD operations include Silane (SiH.sub.4), dichlorosilane (SiCl.sub.2 H.sub.2), tetraethlorthosilicate (Si(OC.sub.2 H.sub.5).sub.4), Diborane (B.sub.2 H.sub.6), Trimethyl borate (B(OCH.sub.3).sub.3), Phosphine (PH.sub.3), Trimethylphosphite (P(OCH.sub.3).sub.3), Arsine (AsH.sub.3) and others.
The current practice is to allow these gases/vapours to enter an exhaust duct to be transported to a wet scrubber positioned at the exhaust end of the lines. This method is occasionally supplemented by local placement of scrubbers. For etching these may be either:
(a) Of the activated charcoal type to trap the acid gases. This method can trap up to 15% of its charcoal weight of Cl.sub.2. The product is charcoal with the effluent gases trapped but not converted to safer products and some of these effluent gases will be liberated if the charcoal is burnt.
(b) Of the wet type; there are several designs of wet scrubber, most using either a Venturi stage or a packed tower or a combination of both. These designs have been used for larger applications: when placed local to the source of the contamination they present the danger of contamination of the process chamber with their aqueous solutions of caustic type media. The contamination can result from a back streaming type of mechanism or from a massive suckback
(c) The chemical filter type utilizing a combination of adsorption and chemical adsorption. These are expensive and do not have a good capacity per unit volume.
PECVD scrubbers can be as above but often have a Burn box gas conditioning unit introduced locally. These units burn the effluent gases to form their oxides and water vapour. They suffer from blockage problems and there are normally large volumes of oxides to contend with.
The chemical exhaust gas conditioning unit of this invention operates in two main sections and an optional third section. The effluent gases pass first through a section in which the active chemical component is elemental silicon Second, through a section in which the active component is lime, or soda lime (calcium oxide or calcium hydroxide). Third, and optionally, through a section in which the active components are lime and copper oxides (CuO or Cu.sub.2 O). These sections can be housed in a single container (FIG. 1) or compartmentalised in different containers (FIG. 2) so that the gases can flow from one to the next. Alternatively the sections can be combined, the silicon mixed with the lime/soda lime in a single reactor.
Broadly stated from one aspect the invention consists in apparatus for treatment of exhaust gases, comprising means for exposing the gases to silicon, or a silicon rich alloy or substance, and means for then exposing the gases to calcium oxide or a calcium oxide compound or calcium oxide containing material, or a sod
REFERENCES:
patent: 4036940 (1977-07-01), McLane
patent: 4442077 (1984-04-01), Foster et al.
patent: 4535072 (1985-08-01), Kitayama et al.
patent: 4629611 (1986-12-01), Fan
patent: 4684510 (1987-08-01), Harkins
Selamoglu, N.; Mucha, J. A.; Flamm, D. L.; Ibbotson, D. E.; "Catalyzed Gaseous Etching of Silicon" Mater. Res. Soc. Symp. Proc., 75 (Photon, Beam, Plasma Stimul. Chem. Processes Surf.), 459-465 (1987).
Smith James R.
Timms Peter L.
Blythe Stephanie
BOC Limited
Cassett Larry R.
Roseblum David M.
Warden Robert J.
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