Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture
Reexamination Certificate
2000-03-24
2004-01-06
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
C423S24000R, C588S253000
Reexamination Certificate
active
06673323
ABSTRACT:
BACKGROUND
The present invention is related to an apparatus and method for reducing a hazardous gas content of an effluent from a process chamber.
Fluorocarbon, chlorofluorocarbons, hydrocarbon, and other fluorine containing gases are used in, or formed as a byproduct during, the manufacture of active and passive electronic circuitry in process chambers. These gases are toxic to humans and hazardous to the environment. In addition, they may also strongly absorb infrared radiation and have high global warming potentials. Especially notorious are persistent fluorinated compounds or perfluorocompounds (PFCs) which are long-lived, chemically stable compounds that have lifetimes often exceeding thousands of years. Some examples of PFCs are carbon tetrafluoride (CF
4
), hexafluoroethane (C
2
F
6
), octafluorocyclopropane or perfluorocyclobutane (C
4
F
8
), difluoromethane (CH
2
F
2
), hexafluorobutadiene or perfluorocyclobutene (C
4
F
6
), perafluoropropane (C
3
F
8
), trifluoromethane (CHF
3
), sulfur hexafluoride (SF
6
), nitrogen trifluoride (NF
3
), and the like. For example, CF
4
has a lifetime in the environment of about 50,000 years and can contribute to global warming for up to 6.5 million years. Thus it is desirable to have an apparatus or method that can reduce the hazardous gas content of effluents, and especially PFCs, that may be released from the process chambers.
Perfluorocompounds are utilized in numerous semiconductor fabrication processes. For example, perfluorocompounds are used in the etching of layers on substrates, such as oxide, metal and dielectric layers. Perfluorocompounds can also be used during chemical vapor deposition processes. Additionally, process chambers can be cleaned of etch or deposition residue using perfluorocompounds. These hazardous compounds are either introduced into a process chamber or are formed as byproducts within the process chamber and may be exhausted from the chamber in an effluent gas stream.
Plasma devices have been used to reduce the PFC content of effluents with limited success. Conventional attempts have not proven to adequately remove a significantly high percentage of the PFC gases from the effluent. For example, in one typical process, Ar, O
2
, and PFC-containing gas are simultaneously added in a plasma chamber at a fixed volumetric flow ratio of Ar to O
2
equal to or greater than 3. The high Ar to O
2
volumetric flow ratio in the conventional process is necessary to ignite and to adequately sustain the plasma. However, this process has a reduction efficiency of below 95% for many PFC gases and significantly below 95% for many complex mixtures of PFC gases. As a result, the conventional process may have to exhaust a higher than desired level of PFCs into the environment.
Thus, it is desirable to minimize the introduction of such harmful gases and byproducts into the environment. There is also a need to minimize the harmful content of the effluent gas released into the atmosphere in an efficient and inexpensive manner. There is a further need to reduce PFC and other harmful gases to the lowest possible levels, preferably by at least about 95%, especially for industries which widely use PFCs, even though such use is a relatively small component of the overall consumption or release of PFCs in the world.
SUMMARY
The present invention is useful for reducing a content of hazardous gases, such as PFCs, in an effluent gas, such as an effluent that results from processing of substrates, for example semiconductor wafers and other electronic devices. By hazardous gas it is meant any toxic, harmful or undesirable gas, including but not limited to PFCs, chlorofluorocarbons (CFCs), hydrocarbons, other fluorine containing gases, and other undesirable gases.
In one aspect of the invention, a method of treating a chamber effluent gas comprising a hazardous gas comprises introducing the effluent gas into a reactor, introducing an additive gas comprising at least one oxygen containing gas into the reactor, the volumetric flow rate of oxygen containing gas being selected so that the ratio of oxygen atoms in the additive gas to carbon atoms in the hazardous gas is at least about 2.4:1, and energizing the effluent and additive gas in the reactor.
In another aspect of the invention, a method of treating a chamber effluent gas comprises introducing the effluent gas into a reactor, introducing an additive gas comprising a reactive gas and an inert or non-reactive gas into the reactor at a volumetric flow ratio of inert or non-reactive gas to reactive gas of less than 3:1, and energizing the effluent and additive gas in the reactor.
In another aspect of the invention, a method of energizing an effluent gas from a chamber comprises introducing an additive gas into a reactor, the additive gas comprising an inert or non-reactive gas at a first volumetric flow rate, changing the volumetric flow rate of the inert or non-reactive gas to a second volumetric flow rate, introducing the effluent gas into the reactor, and energizing the gases in the reactor.
In another aspect of the invention, a method of treating a chamber effluent gas comprises introducing an additive gas into a reactor, the additive gas comprising a reactive gas at a first volumetric flow rate, changing the volumetric flow rate of the reactive gas to a second volumetric flow rate, introducing the effluent gas into the reactor, and energizing the gases in the reactor.
In another aspect of the invention, a method of treating a chamber effluent gas comprises detecting a condition of the effluent, introducing the effluent gas into a reactor, introducing an additive gas into the reactor at a volumetric flow rate in relation to the detected condition, and energizing the effluent and additive gas in the reactor.
In another aspect of the invention, a method of treating a chamber effluent comprising a hazardous gas comprises introducing the effluent gas into a reactor, introducing an additive gas comprising at least one oxygen containing gas into the reactor, the volumetric flow rate of oxygen containing gas being selected so that the ratio of oxygen atoms in the additive gas to sulfur atoms in the hazardous gas is at least about 2.4:1, and energizing the effluent and additive gas in the reactor.
In another aspect of the invention, a method of treating a chamber effluent gas comprising a hazardous gas comprises introducing the effluent gas into a reactor, introducing an additive gas comprising at least one oxygen containing gas into the reactor, the volumetric flow rate of oxygen containing gas being selected so that the ratio of oxygen atoms in the additive gas to nitrogen atoms in the hazardous gas is at least about 2.4:1, and energizing the effluent and additive gas in the reactor.
In another aspect of the invention, a gas treatment apparatus capable of treating a chamber effluent gas comprising a hazardous gas comprises a source of additive gas comprising an oxygen containing gas, a reactor adapted to receive the effluent gas and the additive gas, a controller adapted to control the introduction of additive gas into the reactor so that the ratio of oxygen atoms in the additive gas to carbon atoms in the hazardous gas is at least about 2.4:1, and a gas energizer adapted to energize the gases in the reactor.
In another aspect of the invention, a gas treatment apparatus capable of treating a chamber effluent gas comprises a source of additive gas comprising a reactive gas and an inert or non-reactive gas, a reactor adapted to receive the effluent gas and the additive gas, a controller adapted to control the introduction of additive gas into the reactor so that the volumetric flow ratio of inert or non-reactive gas to reactive gas is less than 3:1, and a gas energizer adapted to energize the gases in the reactor.
In another aspect of the invention, an apparatus capable of energizing an effluent gas from a chamber comprises a source of additive gas comprising an inert or non-reactive gas, a reactor adapted to receive the effluent gas and the additive gas, a controller adapted to control the in
Bhatnagar Ashish
Kaushal Tony S.
Shamouilian Shamouil
Wong Kwok Manus
Applied Materials Inc.
Janah & Associates
Johnson Edward M.
Silverman Stanley S.
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