Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1999-02-04
2001-01-16
Bueker, Richard (Department: 1763)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S169000
Reexamination Certificate
active
06174499
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for treatment of exhaust gas having been generated in manufacturing processes for semiconductor devices, and more particularly to a method and an apparatus for treatment of unreacted PFC gas to avoid direct discharge of the unreacted PFC gas to an atmosphere.
In the semiconductor device manufacturing processes, a PFC gas or a freon gas comprising carbon and fluorine has been used. The PFC gas has been used, for example, as an etching gas in the dry etching process or a cleaning gas in the plasma CVD apparatus. The PFC gas is much higher in global warming power coefficient (GWP) by about a few thousands than that or carbon dioxide, for which reason if the used PFC gas is discharged directly to atmosphere, then a certain influence on the global atmospheric system is concerned. It has been required to control the direct discharge of the used PFC gas to the atmosphere.
In the conventional dry etching apparatus, PFC gases such as CF
4
, C
2
F
6
are used as etching gases. As illustrated in
FIG. 1
, a PFC gas is introduced as a source gas into a dry etching apparatus
1
. PFC gas is then decomposed by a radio frequency plasma whereby not only etching species or etchants but also unreacted PFC gas and etching reaction products are generated. The etching species or etchants are used for the dry etching process. On the other hand, the unreacted PFC gas and reaction products are discharged by a pump
2
from a reaction chamber in the dry etching apparatus
1
. The discharged unreacted PFC gas and etching reaction products are fed to a removal apparatus
3
for removing the reaction products.
If the C
2
F
6
gas is used as an etching gas for etching a silicon oxide film, then etching reaction gases such as SiF
4
, COF
2
are generated. In order to remove such undesired etching reaction gases, it is effective to use an adsorption removal method by use of adsorbents such as zeolite or activated carbon for removal thereof. Since, however, the unreacted PFC gas is chemically stable, the unreacted PFC gas is not adsorbed onto the adsorbents such as zeolite or activated carbon, for which reason conventionally the unreacted PFC gas is obliged to be discharged directly.
The plasma etching apparatus used for the manufacturing processes of the semiconductor device has a low decomposition ratio of 20%, for which reason the majority of the introduced PFC gas is discharged as the unreacted PFC gas. As described above, since the unreacted PFC gas is chemically stable, it is difficult to adsorb the unreacted PFC gas onto the adsorbent, for which reason the unreacted PFC gas is directly discharged to the atmosphere without any treatment or any process. The discharge of the unreacted PFC gas raises the serious problem with providing a great deal of influence to the global atmospheric system. In order to prevent this problem, an additional apparatus is required for compulsory treatment of the unreacted PFC gas to avoid direct discharge of the unreacted PFC gas into the atmosphere.
In order to decompose the unreacted PFC gas, it has been proposed to practice a combustion decomposition method, wherein the unreacted PFC gas is heated up to a high temperature of 1000° C.-1200° C. It has been concerned that this heat treatment at such high temperature may raise another serious problem with safety.
In the above circumstances, it has been required to develop a novel method and apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere with safety and without substantial influence to a global atmospheric system.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel method for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere for providing no substantial influence to a global atmospheric system.
It is a further object of the present invention to provide a novel method for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere with safety.
It is a still further object of the present invention to provide a novel apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere for providing no substantial influence to a global atmospheric system.
It is yet a further object of the present invention to provide a novel apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere with safety.
It is a further more object of the present invention to provide a novel inexpensive apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof.
It is moreover object of the present invention to provide a novel simply structured apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof.
It is another object of the present invention to provide a novel dry etching system provided with an additional apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere for providing no substantial influence to a global atmospheric system.
It is still another object of the present invention to provide a novel dry etching system provided with an additional apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof to an atmosphere with safety.
It is yet another object of the present invention to provide a novel dry etching system provided with an inexpensive apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof.
It is further another object of the present invention to provide a novel dry etching system provided with an additional simply structured apparatus for treatment of the unreacted PFC gas to avoid direct discharge thereof.
The above and other objects, features and advantages of the present invention will be apparent from the following descriptions.
The present invention provides a method of treatment of a freon gas consisting only of carbon and fluorine, wherein the freon gas is exposed to a plasma to decompose and chemically activate the freon gas. The freon gas having been chemically activated is then made into contact with a reactant to form a reaction product.
The present invention also provides an apparatus for treatment of a freon gas consisting only of carbon and fluorine. The apparatus comprises a reaction chamber, a freon gas introducing device connected to the reaction chamber for introducing a freon gas into the reaction chamber, and a plasma generator for generating a plasma in the reaction chamber so that the plasma decomposes and chemically activates the freon gas.
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Bueker Richard
Fieler Erin
NEC Corporation
Young & Thompson
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