Measuring and testing – Gas analysis
Reexamination Certificate
1998-08-28
2004-04-06
Cygan, Michael (Department: 2855)
Measuring and testing
Gas analysis
C073S023310, C073S03200R, C422S094000, C422S095000
Reexamination Certificate
active
06715338
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for detecting a flammable gas in a gas mixture and more particularly, relates to an apparatus and a method for detecting a flammable gas in an exhaust gas flown from a process machine by utilizing an ignitor and a temperature sensor for igniting the flammable gas in a reactor chamber and then sensing a temperature rise caused by the ignition of the flammable gas so that the exhaust gas flow may be shut-off.
BACKGROUND OF THE INVENTION
In the fabrication of semiconductor devices, a semi-conducting wafer must be processed in a large number of processing steps for producing integrated circuit chips. These processing steps may amount to as many as several hundred. The various processing steps are conducted in a variety of processing machines to carry out various chemical or physical reactions on the semi-conducting wafer. In the various fabrication steps an effluent or exhaust gas from the process machine must be treated either in a chemical reaction process or in an absorption or condensation process before it can be released into a factory exhaust system and subsequently into the atmosphere. A large number of reactant gases and their reaction products utilized in the semiconductor fabrication industry are highly flammable or highly toxic. The gases exhausted out of a process chamber may include gases that have not been reacted or have been partially reacted and therefore, must be treated before they can be released into the factory exhaust system or into the atmosphere.
Exhaust gas treatment systems have been used for converting toxic gases into nontoxic substances. One of such gas treatment systems is a gas reactor column (GRC) designed to eliminate hazardous gases from the exhaust of semiconductor process chambers. A gas reactor column may be a hot-bed type reactor that treats a variety of gases in a single cartridge without creating additional effluent disposal problems. These types of gas reactor columns, while efficient in converting toxic gases into non-toxic gases, are not particularly useful in treating flammable gas components in an exhaust gas mixture.
Another method of treating exhaust gases is the use of an absorption unit which functions on the principle of gas absorption into a porous substance without chemical reactions taking place. This type of physical absorption process can be carried out by using a bed of porous substance such as activated carbon for absorbing certain components in exhaust gases, specifically those of low boiling temperature and of foul-smelling. While the low boiling temperature gases, i.e., those having a boiling temperature of less than 100° C., can be successfully removed by an absorption apparatus filled with a substance such as activated carbon, the high boiling temperature gases, i.e., those are likely flammable, cannot be effectively removed by the absorption apparatus.
Still other methods combines a conventional absorption method and a conventional condensation method. For instance, one of such apparatus for carrying out a combined absorption/condensation method is shown in FIG.
1
. Apparatus
10
, shown in
FIG. 1
, utilizes an absorption apparatus for absorbing the low boiling temperature gases in an exhaust gas mixture and a condensation apparatus for condensing the high boiling temperature components in the exhaust gas mixture. For instance, the dual-stage apparatus
10
for treating an exhaust gas from a semiconductor fabrication machine consists of a condensation unit
20
and an absorption unit
30
. Exhaust gas
12
from a fabrication machine is fed through a flow control valve
14
, a filter
16
into a condenser
28
which is part of the condensing unit
20
. The condensing unit
20
consists of the condenser
28
, a liquid collection tank
32
and a pump
34
. The liquid collection tank
32
collects the condensed liquid from condenser
28
through pipe
36
and pumps it away by pump
34
. A city water supply
38
may be used, either with or without refrigeration, as the cooling water in condenser
28
. Normally high boiling temperature components of the exhaust gas
12
are removed by the condensing unit
20
. However, for high boiling temperature gases such as BMOS (C
2
H
6
SO) and NMP (C
3
H
9
NO), the efficiency of removal by the condensing unit
20
is less than 70%.
At the output end of the condensing unit
20
, partially treated exhaust gas
42
exits and is fed into an absorption unit
30
. The absorption unit
30
is constructed of an absorption bed
52
which contains a porous material such as activated carbon, or any other suitable porous material. The inlet and the outlet pressure of the absorption bed
52
is monitored by a differential pressure gauge
54
. The monitoring of the differential pressure is important since it provides an indication when the absorption medium, i.e., the activated carbon, needs to be replaced or replenished. The exhaust gas
58
exiting the absorption bed
52
is taken away by a blower
62
and fed into a factory exhaust system for releasing to the atmosphere.
The conventional exhaust gas treatment system
10
of
FIG. 1
is not efficient in removing the high boiling temperature components, i.e., the high flammability gases, in the exhaust gas mixture. This presents a serious problem in that not only the high boiling temperature gases pollute the environment when released to the atmosphere, the high flammability gases also create a serious fire or explosion hazard in the factory exhaust system. When an explosion or fire occurs in the factory exhaust system, fire propagates to all process machines that are connected in fluid communication with the factory exhaust line. The potential fire hazard can therefore cause destruction of an entire fabrication facility when the factory exhaust line is connected to a large number of process chambers.
It is therefore an object of the present invention to provide an apparatus capable of detecting flammable gas components in a gas mixture exhausted from a semiconductor fabrication machine so that the flammable gas components may be prevented from entering a factory exhaust system.
It is another object of the present invention to provide a method for detecting the flammable gas components in a gas mixture exhausted from a semiconductor fabrication machine and for preventing the flammable gas components from entering a factory exhaust system.
It is a further object of the present invention to provide an apparatus for detecting flammable gas components in a gas mixture by utilizing a reactor chamber in which the flammable gas components may be ignited.
It is another further object of the present invention to provide an apparatus for detecting flammable gas components in a gas mixture by using a reactor chamber equipped with an electronic ignitor and a temperature sensor.
It is still another object of the present invention to provide an apparatus for detecting a flammable gas in a gas mixture by utilizing a reactor chamber equipped with an electronic ignitor, a temperature sensor and a valve means for shutting off the supply of the flammable gas when the temperature sensor senses a temperature rise.
It is yet another object of the present invention to provide an apparatus for detecting a flammable gas in a gas mixture by utilizing a reactor chamber equipped with an electronic ignitor, a temperature sensor and a two-way solenoid valve capable of switching an input to the reactor chamber from an exhaust gas to ambient air.
It is still another further object of the present invention to provide a method for detecting a flammable gas in a gas mixture by igniting the flammable gas in a reactor chamber and detecting a temperature rise of the gas mixture.
It is yet another further object of the present invention to provide a method for detecting a flammable gas in a gas mixture by igniting in a reactor chamber the flammable gas and detecting a temperature rise of more than 30° C. such that an input to the reactor chamber can be switched to ambient air by a two-way so
Cygan Michael
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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