JP2004349442A - Method and apparatus for detoxifying exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for detoxifying exhaust gas for reducing the influences resulting from thermal shock to a heater, which is caused by variation of exhaust gas inflow. <P>SOLUTION: The method for detoxifying exhaust gas is provided, wherein exhaust gas discharged from a semiconductor manufacturing device is heated and decomposed by a rod-like heat generator 20 of the electric heater 19. A nitrogen gas is supplied from a purge line 32 so that the amount of gas that flows in from a heat decomposition reactor 8 is allowed to be constant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas abatement method and an exhaust gas abatement apparatus. More specifically, the present invention relates to an exhaust gas elimination method and an exhaust gas elimination apparatus in which exhaust gas discharged from a semiconductor manufacturing apparatus is thermally decomposed by a heater.
[0002]
[Prior art]
In the semiconductor manufacturing process, various gases are used as a material gas or a cleaning gas. However, in recent years, gas used in the semiconductor manufacturing process due to problems such as environmental ISO and global warming, that is, treatment of exhaust gas. Importance is being sought, and various exhaust gas abatement apparatuses have been conventionally proposed (for example, see Patent Document 1).
[0003]
FIG. 3 schematically shows the flow of processing of exhaust gas discharged from a semiconductor manufacturing apparatus 101 such as a CVD (Chemical Vapor Deposition) apparatus.
Here, for example, when performing self-cleaning using the principle of dry etching of a processing chamber in a semiconductor material gas such as monosilane (SiH ₄ ), ammonia (NH ₃ ), and dichlorosilane (SiH ₂ Cl ₂ ) or in a semiconductor device. The used cleaning gas is exhausted from the semiconductor manufacturing apparatus by being taken into the suction port of the vacuum pump 103 through the vacuum pipe 102. The material gas or cleaning gas (hereinafter, referred to as exhaust gas) taken into the vacuum pump is inert such as nitrogen so that the concentration thereof is lower than the explosion limit, for example, in the case of monosilane, it is 1.2% or lower. The diluted exhaust gas is diluted by the gas, and the diluted exhaust gas is rendered harmless by thermal oxidative decomposition in a material gas abatement apparatus 104a or a cleaning gas abatement apparatus 104b (hereinafter, referred to as an exhaust gas abatement apparatus), and is denoted by a symbol A in FIG. It is discharged to the factory exhaust line indicated by.
[0004]
In the case of a semiconductor manufacturing apparatus having a plurality of chambers, each chamber performs processing independently, and a chamber during film formation using a semiconductor material gas and a chamber during self-cleaning using a cleaning gas. May exist at the same time. Here, if a semiconductor material gas and a cleaning gas are mixed, there is a risk of causing an explosion due to a chemical reaction. In the case of a semiconductor manufacturing apparatus having a plurality of chambers, an exhaust switching valve is provided at an exhaust port of a vacuum pump. The exhaust line 105 is configured to be switched based on a signal from the semiconductor manufacturing apparatus for starting a film forming process and a cleaning process.
[0005]
FIG. 4 is a schematic view for explaining a conventional exhaust gas abatement apparatus. The exhaust gas abatement apparatus shown here mainly includes an inlet scrubber 106, an outlet scrubber 107, and an inlet scrubber and an outlet scrubber. It comprises a thermal decomposition reactor 108 disposed therebetween, a first water tank 109a disposed below the inlet side scrubber, and a second water tank 109b disposed below the outlet side scrubber.
[0006]
Here, an exhaust gas introduction pipe 110 communicating with the discharge port of the vacuum pump is connected to the upper part (inlet part) of the inlet side scrubber, and below the exhaust gas introduction pipe, that is, near the inlet part of the inlet side scrubber. Is provided with a first shower nozzle 111, and the first shower nozzle is connected to the discharge side of the circulation pump 112.
Further, an exhaust fan 113 for exhausting gas detoxified in the exhaust gas abatement apparatus to a factory line is connected to an upper portion (exit portion) of the output side scrubber. That is, the second shower nozzle 114 is provided near the outlet of the outlet side scrubber, and the second shower nozzle is connected to the discharge side of the circulation pump.
The circulation pump is installed between the first shower nozzle and the second shower nozzle and the water tank, and is configured to pump water in the water tank to the first shower nozzle and the second shower nozzle. Have been.
[0007]
Further, the thermal cracking reactor is provided in an airtight manner integrally with each of the inlet side scrubber and the outlet side scrubber, and a first wall portion extending downward is provided at a boundary between the inlet side scrubber and the thermal cracking reactor. 115 is formed, and a partition wall 116 that separates the first water tank and the second water tank is provided at a position facing the first wall portion so as to extend upward from the bottom of the water tank. Further, a communication pipe 117 is formed which is connected to the first wall portion and the partition wall to communicate between the inlet side scrubber and the thermal decomposition reactor. That is, the exhaust gas introduced into the inlet side scrubber is guided into the communication pipe through the space between the lower end of the wall and the water surface of the first water tank.
Note that the partition does not completely separate the first water tank and the second water tank, and is formed only in a certain range necessary to guide exhaust gas to the communication pipe in the horizontal direction of the water tank. ing. That is, the water in the first water tank and the water in the second water tank can communicate with each other, and the water surfaces of both tanks are kept at the same height.
[0008]
In addition, a communication pipe is connected to an inner cylinder 118 at a lower part in the thermal decomposition reactor so as to be able to communicate with the inner cylinder. The inner cylinder extends upward inside the thermal decomposition reactor, and an upper end thereof is open. Further, the thermal decomposition reactor is provided with an electric heater 119 at an upper portion thereof, and a bar-shaped heating portion 120 of the electric heater is disposed around the inner cylinder. Further, a blower 121 for thermal oxidation reaction is connected to the inside of the thermal decomposition reactor, so that air containing oxygen required for oxidative thermal decomposition can be sent from the blower into the thermal decomposition reactor.
[0009]
A second wall 122 extending downward is also formed at the boundary between the thermal cracking reactor and the outlet side scrubber, and the exhaust gas thermally decomposed in the thermal cracking reactor passes through the second wall. It is guided to the outlet side scrubber through the space between the lower end of the part and the water surface of the second water tank. In the water tank, fresh water is constantly supplied from a water supply line indicated by reference symbol B in FIG. 4 via a valve 123, and the water supply line is also connected to an inlet side scrubber, an outlet side scrubber, and a pyrolysis reactor. This new water is also used when automatically cleaning the inside of the exhaust gas abatement system during regular maintenance.
[0010]
Hereinafter, the operation of the exhaust gas abatement apparatus configured as described above will be described.
That is, first, the overall flow of gas in the exhaust gas abatement apparatus will be described. Exhaust gas introduced from the vacuum pump into the inlet side scrubber via the exhaust gas introduction pipe is discharged from the vacuum pump at the outlet side. By the suction force of the exhaust fan installed in the scrubber, a flow is formed from the inlet side scrubber to the communication pipe, the thermal decomposition reactor, and the outlet side scrubber, and exhausted from the exhaust fan to the factory exhaust line. A pressure gauge 124 is attached to the gas inlet of the inlet side scrubber. The pressure gauge 124 monitors the pressure at the inlet, and responds to a pressure change due to a change in the gas inflow amount through an inverter 125 via an inverter 125. The exhaust capacity is changed.
[0011]
Exhaust gas introduced into the inlet side scrubber is first washed with water from a first shower nozzle with shower water, and by this washing, dust and dust in the exhaust gas are dropped into a first water tank and removed. The flushed exhaust gas flows into the inner cylinder via the communication pipe through the space between the lower end of the first wall and the water surface of the first water tank.
[0012]
Next, the exhaust gas travels upward in the inner cylinder, and is discharged from the upper end opening of the inner cylinder to the inside of the thermal decomposition reactor. Here, oxidation is caused by mixing with the air sent into the thermal decomposition reactor from the blower, and since the inside of the thermal decomposition reactor is heated by an electric heater, the oxidation reaction between the exhaust gas and oxygen in the air is performed. Is promoted, and toxic gas in the exhaust gas, for example, silane is decomposed by oxidation to form harmless silica (SiO ₂ ) powder. The reaction by-products such as silica generated by the thermal oxidative decomposition fall into the second water tank, and a part of the reaction by-products together with the exhaust gas as droplets and the water surface of the second water tank. And into the exit side scrubber.
[0013]
Subsequently, the exhaust gas and reaction by-products guided into the outlet side scrubber are washed with water by shower water from the second shower nozzle, and the reaction by-products are removed into the second water tank. The detoxified exhaust gas is discharged to an exhaust line on the factory side via an exhaust fan. Dust and reaction by-products floating on the water surface of the water tank are discharged from the overflow line 126 to the outside of the exhaust gas abatement apparatus.
[0014]
[Patent Document 1]
JP-A-2000-24447 (Pages 2-4, FIG. 2)
[0015]
[Problems to be solved by the invention]
However, since the flow rate of the exhaust gas discharged from the semiconductor manufacturing apparatus changes greatly depending on the operating state of the semiconductor manufacturing apparatus, there is a problem that the amount of the exhaust gas flowing into the exhaust gas removing device also changes greatly.
That is, when the semiconductor manufacturing apparatus is in a film forming state or a cleaning state, a semiconductor material gas or a cleaning gas and a nitrogen gas for dilution are several hundred liter / min. While the exhaust gas flows into the exhaust gas abatement apparatus at a moderate flow rate, when the semiconductor manufacturing apparatus is in a standby state, almost no exhaust gas flows into the exhaust gas abatement apparatus. When the exhaust gas is flowing, the rod-shaped heat generating portion of the electric heater is cooled by the exhaust gas and the temperature is reduced, but the electric power is controlled to a constant temperature. Further, when no exhaust gas is flowing, the rod-shaped heat generating portion is not cooled, and the electric power is controlled to a constant temperature. However, the repeated fluctuation of the exhaust gas flow rate causes a sudden temperature change to the rod-shaped heat generating portion of the electric heater in the exhaust gas abatement apparatus, and acts as a thermal shock, causing the rod-shaped heat generating portion to break or crack. There is a problem that it will. In particular, when the cleaning gas is thermally oxidized and decomposed, the rod-shaped heat generating portion is generally heated to about 900 ° C. to 1000 ° C., so that the effect of the thermal shock based on the fluctuation of the exhaust gas inflow amount is large.
[0016]
The present invention has been made in view of the above points, and provides an exhaust gas detoxification method and an exhaust gas detoxification device capable of reducing the influence of thermal shock on a heater based on fluctuations in exhaust gas inflow. It is intended to provide.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, in the method for removing exhaust gas according to the present invention, in the method for removing exhaust gas by heating and decomposing exhaust gas discharged from a semiconductor manufacturing apparatus by a heater, the flow rate of the gas to be heated is substantially constant. Thus, a conditioning gas is supplied to the heater together with the exhaust gas.
[0018]
Here, by supplying the adjustment gas together with the exhaust gas to the heater so that the flow rate of the gas to be heated becomes substantially constant, the temperature change of the heater can be reduced.
[0019]
Further, in order to achieve the above object, in the exhaust gas abatement apparatus according to the present invention, in the exhaust gas abatement apparatus that thermally decomposes the exhaust gas discharged from the semiconductor manufacturing apparatus, a heater for heating the exhaust gas, An adjusting gas supply unit configured to supply an adjusting gas to the heater; and a flow control unit configured to control a supply amount of the adjusting gas from the adjusting gas supplying unit so that a flow rate of the gas heated by the heater is substantially constant. .
[0020]
Here, a change in the temperature of the heater is reduced by a flow control unit that controls the supply amount of the adjustment gas from the adjustment gas supply unit that supplies the adjustment gas to the heater so that the flow rate of the gas heated by the heater is substantially constant. can do.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings to provide an understanding of the present invention.
[0022]
FIG. 1 is a schematic diagram for explaining an example of an exhaust gas abatement apparatus to which the present invention is applied. The exhaust gas abatement apparatus 1 shown here is mainly similar to the above-described conventional exhaust gas abatement apparatus. It comprises an inlet side scrubber 6, an outlet side scrubber 7, a thermal decomposition reactor 8, a first water tank 9a and a second water tank 9b, and an exhaust gas introduction pipe 10 is connected to the upper part of the inlet side scrubber. A first shower nozzle 11 connected to the discharge side of the circulation pump 12 is arranged near the inlet of the scrubber, and an exhaust fan 13 is connected to the upper part of the output scrubber, near the outlet of the outlet scrubber. Is provided with a second shower nozzle 14 connected to the discharge side of the circulation pump.
In addition, a partition 16 is provided at a position facing the first wall 15, and a communication pipe 17 is formed by connecting the first wall and the partition, and a communication pipe is formed at a lower portion in the thermal decomposition reactor. The point that it is communicably connected to the inner cylinder 18 is the same as the above-described conventional exhaust gas abatement apparatus. Further, the thermal decomposition reactor is provided with an electric heater 19 at an upper portion thereof, and the point that a bar-shaped heat generating portion 20 of the electric heater is disposed around the inner cylinder is also the same as the above-mentioned conventional exhaust gas abatement apparatus. . A thermal oxidation reaction blower 21 is connected to the inside of the thermal decomposition reactor.
[0023]
In addition, a nitrogen purge line 32 provided with a mass flow controller 30 and an air operated valve 31 is formed in the vicinity of the exhaust gas introduction pipe, and the nitrogen is supplied from the purge line so that the gas flow supplied to the thermal decomposition reactor is constant. Is configured to be supplied.
That is, by receiving signals related to the film forming process and the cleaning process from the semiconductor manufacturing device, such as an opening / closing signal of a gas line for supplying a gas used in the semiconductor manufacturing device, the opposing operation synchronized with the exhaust switching valve of the vacuum pump is performed. When the exhaust switching valve is open, the air operated valve is closed and nitrogen is not supplied from the purge line to the thermal decomposition reactor.When the exhaust switching valve is closed, the air operated valve is opened. Nitrogen is configured to flow from the purge line into the pyrolysis reactor. The inflow of nitrogen from the purge line when the exhaust switching valve is open is the sum of the exhaust gas flow from the semiconductor manufacturing apparatus when the exhaust switching valve is closed and the dilution nitrogen flow in the vacuum pump. Set to be equal to the flow rate.
[0024]
Here, by supplying gas from the purge line, it is sufficient that the amount of gas flowing into the thermal decomposition reactor when the exhaust switching valve is open becomes equal to the amount of gas flowing when the exhaust switching valve is closed. The gas supplied from the purge line is not necessarily required to be nitrogen gas. For example, any gas such as dry air may be used, but an inert gas such as nitrogen which does not react with other gases in consideration of safety. It is preferable to use
[0025]
Further, the gas flow rate control means for the exhaust gas abatement apparatus does not necessarily need to be a mass flow controller, and the gas flow rate may be controlled by, for example, a needle valve.
Furthermore, the gas flow path switching means for switching the gas inflow path during operation and standby of the semiconductor manufacturing apparatus used for the purge line does not necessarily need to be an air operated valve in consideration of the characteristics of the gas to be abated, A simple solenoid valve or the like may be used. That is, in one example of the exhaust gas abatement apparatus to which the present invention is applied, an air operated valve is formed in the exhaust gas abatement apparatus, and an electric device (not shown) for driving the air operated valve is provided with an exhaust gas abatement apparatus. Is formed outside the abatement system to prevent explosion due to sparks that can be generated from electrical equipment. However, if there is no danger of explosion etc. in the gas used for the purge line, a solenoid valve etc. May be used to switch the gas inflow path.
[0026]
In the exhaust gas abatement apparatus of the present invention described above, the purge line is configured to perform a reciprocal operation in synchronization with the exhaust gas switching valve of the vacuum pump so that the amount of gas flowing into the thermal decomposition reactor is constant. Meanwhile, in the conventional exhaust gas abatement apparatus, when the exhaust gas switching valve of the vacuum pump is open as shown in FIG. 2A, the amount of gas flowing into the thermal decomposition reactor is at a high level (hereinafter, H level). On the other hand, when the exhaust switching valve of the vacuum pump is closed, the fluctuation of the gas flow rate such that the amount of gas flowing into the thermal decomposition reactor becomes low level (L level) is shown in FIG. ), When the exhaust switching valve of the vacuum pump is open, the supply amount of nitrogen gas is set to L level, and when the exhaust switching valve of the vacuum pump is closed, the supply amount of nitrogen gas is set to H level. gas The amount of heat can be kept constant, and the thermal shock caused by the rapid temperature change in the rod-shaped heating part of the electric heater in the exhaust gas abatement system based on the fluctuation of the gas flow rate can be mitigated. And crack breakage can be suppressed, the life of the electric heater can be drastically improved, and the operation rate of the exhaust gas abatement apparatus can be improved and maintenance costs can be reduced.
[0027]
In addition, in the case where the semiconductor manufacturing apparatus is in a standby state as well as when the semiconductor manufacturing apparatus is in a film forming state or a cleaning state, the gas is generated by thermal decomposition in an exhaust gas abatement apparatus by flowing gas from a purge line. Blockage of the factory side exhaust line due to reaction by-products can be suppressed.
[0028]
【The invention's effect】
As described above, in the exhaust gas elimination method and the exhaust gas elimination apparatus of the present invention, it is possible to reduce the influence of thermal shock based on the fluctuation of the exhaust gas inflow amount.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining an example of an exhaust gas abatement apparatus to which the present invention is applied.
FIG. 2 is a schematic diagram for explaining an amount of gas flowing into an exhaust gas abatement apparatus.
FIG. 3 schematically shows a flow of processing of exhaust gas discharged from the semiconductor manufacturing apparatus.
FIG. 4 is a schematic view for explaining a conventional exhaust gas abatement apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exhaust gas removal device 6 Inlet side scrubber 7 Outlet side scrubber 8 Thermal decomposition reactor 9a First water tank 9b Second water tank 10 Exhaust gas introduction pipe 11 First shower nozzle 12 Circulation pump 13 Exhaust fan 14 Second Shower nozzle 15 first wall portion 16 partition wall 17 communication pipe 18 inner cylinder 19 electric heater 20 rod-shaped heating portion 21 blower for thermal oxidation reaction 30 mass flow controller 31 air operated valve 32 purge line

Claims (4)

In a method for removing exhaust gas by thermally decomposing exhaust gas discharged from a semiconductor manufacturing apparatus by a heater,
A method for abating exhaust gas, comprising supplying an adjustment gas together with the exhaust gas to the heater so that the flow rate of the gas to be heated is substantially constant. The method of claim 1, wherein the adjusting gas is an inert gas. In an exhaust gas abatement system that thermally decomposes exhaust gas discharged from semiconductor manufacturing equipment,
A heater for heating the exhaust gas,
Adjusting gas supply means for supplying an adjusting gas to the heater;
An exhaust gas abatement apparatus comprising: a flow rate control unit that controls a supply amount of the adjustment gas from the adjustment gas supply unit so that a gas flow rate heated by the heater is substantially constant. The exhaust gas abatement apparatus according to claim 3, wherein the adjustment gas is an inert gas.

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