Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1995-02-23
1997-09-30
Kim, Christopher
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
422174, 417244, 417266, 417345, 110345, B01D 5000
Patent
active
056723229
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for converting reactive gases which are sucked in at a low inlet pressure and are expelled at a higher outlet pressure by a single dry multi-stage pump, in which method the reactive gases are physically and/or chemically converted into non-reactive components two stages of a dry multi-stage pump.
Such a method is disclosed in the European Patent Application No. 0 448 750 and is used, in particular, in the production of, for example, chips, LC screens and the like, or in the application of coatings to products of all kinds. In this case, a starting material is treated in a reactor with the aid of chemical or physical processes or a combination of such processes. Generally, a low to very low pressure (approximately 10.sup.-1 -1000 Pa) prevails in the reactor and gases which are, for example, deposited on the starting material or are used in some other way by the treatment processes are supplied for the treatment of the surface of the starting material. For a number of reasons, such as, for example, to obtain a uniform distribution of the substances to be deposited on the surface of a wafer and to increase the production rate, such gases are supplied in excess. Generally, only approximately 15% of the gas supplied is used in the reactor, whereas the remainder and the gaseous reaction products are expelled again. The remaining gas or effluent is expelled into the atmosphere via a pipe, a vacuum pump, preferably only one multi-stage pump, and an expelling pipe system. The gases or gas mixtures used in the reactor, such as silane and ammonia, tetraethoxysilane, tungsten hexafluoride and hydrogen, dichlorosilane and ammonia, titanium chloride and dichlorosilane, and tetradimethyl-aminotitanium and ammonia are generally toxic, corrosive and flammable. The gaseous reaction products usually contain solids which may damage the vacuum pump and may block the expelling pipe system, which may result in explosions.
Solid dust particles are liberated in the treatment processes in the reactor and may be produced by the gases reacting in the pipe from the reactor to the pump and in the pump itself under the influence of the temperature prevailing therein, solid particles being released. In the case of silane, for example, glassy solid particles are produced by oxidation.
Because the pressure of the gases sucked in by the dry multi-stage pump is very low and the flow rate is high, only a few reactions occur in the first stages of the pump and few solids are released therein. However, when the pressure becomes higher in the subsequent pump stages and the dwell time of the reactive gases in the pump therefore becomes longer, said gases will react and large amounts of solid dust particles will be released which may damage the pump and may block the expelling pipe system situated downstream of the pump. The proposal made in the abovementioned European application provides a solution to these problems in that the reactive gases are converted with the aid of physical and/or chemical processes in a chamber designed for the purpose at a pressure situated between the intake pressure and the delivery pressure of the pump.
Such a method provides the advantage that the conditions prevailing in the cheer in which the reactive gases are converted into nonreactive gases and solids can be optimally controlled by the compression stage or stages to be carried out upstream of said conversion, and moreover that the conversion process cannot affect the processing conditions in the reactor because the chamber in which the conversion takes place is adequately shielded from the reactor by the compression stage or stages to be carried out between the reactor and the conversion chamber.
Another advantage is that the use of flushing gases, which are used to reduce the concentration of the reactive gases in the pump in order to reduce the reaction tendency, can be completely eliminated or can at least be reduced. Because the pressure in the first compression stage or stages is still very low and the dwell time of the re
REFERENCES:
patent: 5131825 (1992-07-01), Bachmann et al.
Abstract of JP 58-006231 dated Jan. 13, 1983 -"Patent Abstracts of Japan", vol. 7, No. 69 (C-158), Mar. 23, 1983.
Abstract of JP 60-101544 dated Jun 5, 1985 -Database WPIL, Section Ch, Week 8529, Derwent Publications Ltd., London, GB; Class G08, AN 85-173743.
Kim Christopher
Leybold AG
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