JPH04290527A - Method and device for treating waste cvd gas - Google Patents

Abstract

PURPOSE:To prevent the formation of NOx and to make all harmful gases harmless at a low running cost by heating, oxidizing and decomposing a waste CVD gas and then oxidizing the treated gas by contact with an oxidation catalyst in the presence of oxygen. CONSTITUTION:The waste CVD gas treating device 1 is formed with a heating, oxidizing and decomposing device 2 and a catalytic reaction vessel 3. The waste gas from a waste gas inlet pipe 4, the nitrogen from a nitrogen inlet pipe 5 and the air from an air inlet pipe 6 are introduced into the reaction part 11 of the device 2 to heat, oxidize and decompose the waste gas. The treated gas contg. the reaction product is washed with cooling water 12 in a washing part 13, the waste water contg. the solubles such as F2 and SiF4, SiO2, etc., is discharged outside the system, the waste gas is introduced into the catalytic reaction vessel 3 to oxidize CO, etc., hence the waste gas is cleaned and made harmless. Consequently, the formation of NOx is prevented at a low running cost, and all the harmful gases are made harmless.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention focuses on organic sources such as unreacted process gases and organic substances and CO produced by their decomposition in the exhaust gas of CVD (chemical vapor deposition) processes carried out in the manufacture of semiconductors. Contains harmful ingredients such as The present invention relates to purifying exhaust gas containing harmful components to render it harmless.

0002

2. Description of the Related Art Conventionally, treatment has been carried out using a wet scrubber, activated carbon adsorption, or the like. The problem with wet scrubber treatment is that the removal rate of harmful components is low.

[0003] Furthermore, the activated carbon adsorption method has problems in that it is expensive to replace activated carbon that has broken through and that CO cannot be removed. In addition, TEOS (tetraethoxysilane) and its decomposed organic substances are flammable, and hydrogen gas and LPG
Cheap treatment can be achieved by burning such substances as combustion improvers, but
As the temperature of the flame increases, nitrogen in the exhaust gas is oxidized and becomes N.
OX will be generated.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a CVD exhaust gas treatment method and apparatus capable of preventing NOX generation and rendering all harmful gas components harmless at a lower running cost than conventional methods.

[0005]

[Means for Solving the Problems] The present invention is a method and apparatus described in (1) and (2) below, which can solve the above problems. (2) A method for treating CVD exhaust gas, which comprises subjecting CVD exhaust gas to a heating oxidation decomposition treatment, and then bringing the heated oxidation decomposition treated gas into contact with an oxidation catalyst in the presence of oxygen for oxidation treatment. (1) A CVD device characterized by comprising a device for heating and oxidizing and decomposing CVD exhaust gas, and a device provided after the device for oxidizing the heated and oxidizingly decomposed gas by bringing it into contact with an oxidation catalyst in the presence of oxygen. Exhaust gas treatment equipment.

[0006] The present invention subjects CVD exhaust gas to thermal oxidative decomposition treatment, and brings harmful unoxidized substances, mainly CO, present in the treated gas into contact with a catalyst coexisting with oxygen, thereby oxidizing and detoxifying the treated gas. However, since the oxidation treatment can be performed at a temperature that does not produce NOX,
It does not cause secondary contamination and can be processed at low cost.

[0007] The present invention can be constructed so that the temperature of the reaction section of an apparatus for thermally oxidatively decomposing substances existing in exhaust gas can be controlled, and a heating method using an electric heater is suitable.

[0008] Heat-oxidative decomposable substances in exhaust gas, for example,
Since TEOS, alcohol, aldehyde, etc. oxidize rapidly at temperatures above 800°C, the temperature of the reaction section should be 800 to 1000°C, considering the economical efficiency of the equipment and the prevention of NOX formation.
is preferred.

In the treatment by the thermal oxidation decomposition equipment used in the present invention, the oxidation rate of CO in the exhaust gas is about 50% at temperatures below 1000°C, but the oxidation rate of CO in the exhaust gas is about 50%.
Since O2 is removed by washing with water or the like, and organic matter is removed by oxidative decomposition into CO2 and water, CO oxidation, residual organic matter oxidation, etc. can be processed at high speed in the subsequent catalyst treatment device.

[0010] The catalyst is not particularly limited as long as it has an oxidizing power, but a catalyst having a CO oxidizing power is particularly preferred. Examples of the catalyst include Cu, Mn, Cu, Co, Cr, and Pt.
oxides are preferred, and one or more of these oxides may be included. Further, the form of these catalysts is also arbitrary, and can be threaded, powdered, or a composite material with other materials such as cellulose, etc., and is usually connected to the inlet of the gas that has been subjected to the thermal oxidation decomposition treatment and the oxidation treatment. It can be used by filling or loading a desired amount into a container provided with an outlet for the gas.

The oxide catalyst can be processed at relatively low temperatures and is particularly effective. In that case, the temperature may be 150° C. or higher, which eliminates the influence of moisture and residual organic matter. In addition, from the oxidation rate in the catalyst, the SV (flow velocity) of the gas that has been heated and oxidized and decomposed in the catalyst device is around 20,000 1/h, but there is no problem with it.
It is desirable to process from 1/h to 10,000 1/h.

[0012] Here, the oxygen present in the catalyst may be supplied by supplying the oxygen necessary for thermal oxidative decomposition to the reaction part and using the remaining amount consumed in the thermal oxidative decomposition, or by separately supplying the oxygen to the catalyst. You may also do so.

[0013]CVD exhaust gas in the present invention refers to CVD
This mainly includes CVD-treated exhaust gas of process gas used in the CVD (chemical vapor deposition) method from the equipment, but in some cases, exhaust gas from cleaning after using the gas for cleaning the CVD equipment. can also be included.

CV for providing CVD exhaust gas in the present invention
The raw material D, that is, the process gas, includes known ones, such as inorganic raw materials such as monosilane, disilane, dichlorosilane, etc., and organic raw materials such as TEO
There are S (tetraethoxysilane) and the like, and one or more of these may be used alone or in combination. These exhaust gases include these unreacted substances, their derivatives, and reaction decomposition products, such as H2, CO, alcohols such as C2 H5 OH, aldehydes such as CH3 CHO, and C2 H4.
It contains substances that can be decomposed by heating and oxidation such as hydrocarbons, etc., and when it is decomposed by heating and oxidation, it mainly becomes metal oxides such as SiO2, H2O and CO2. Thermal oxidative decomposition referred to here refers to the mere oxidation of something that cannot be decomposed, for example,
It is clear that the term also includes the oxidation of simple substances such as hydrogen and metals.

[0015] As the cleaning gas, NF3, C
Examples include F4, C2 F6, SF6, ClF3, etc., and the cleaning exhaust gas is a combination of cleaning gas and C
It consists of reactants with substances inside the VD apparatus (unexhausted CVD treated substances, etc.), such as SiF4, cleaning gas derivatives, etc., and cleaning gases and substances inside the CVD physically cleaned by the cleaning gas.

The reaction conditions for the thermal oxidative decomposition treatment in the present invention, the conditions for introducing the exhaust gas, etc. are not particularly limited, but at least the thermal oxidative decomposable substances contained in the exhaust gas are thermally oxidized and decomposed in the presence of oxygen. That's fine. Therefore,
When the exhaust gas is introduced into the thermal oxidation decomposition device, it is necessary that oxygen is present in the thermal oxidation reaction section at the same time. This oxygen may be present in any manner, but it is usually preferable to introduce the oxygen together with the exhaust gas as an oxygen-containing gas, such as air. Furthermore, any gas may be mixed in order to adjust the conditions for thermal oxidative decomposition. For example, it is preferable to mix an inert gas such as nitrogen and introduce the nitrogen gas into the reaction section of the thermal oxidative decomposition device in a three-layered state, in which the nitrogen gas envelops the exhaust gas and the oxygen surrounds them. It is preferable to provide these gas introduction portions with three concentric tube layers.

[0017] The heating means used in the thermal oxidative decomposition treatment is also arbitrary, but preferably a heater heating method capable of electrically controlling the temperature as described above is preferable, and can usually be provided within the wall of the reaction section. In addition, the temperature of the reaction section is 8
The temperature range is preferably from 00 to 1000°C. If the temperature is over 1000℃, NOX will be generated due to oxidation of N2 gas, so
Undesirable.

In the present invention, the exhaust gas subjected to the thermal oxidative decomposition treatment can be directly transferred to the catalyst treatment device, or can be further subjected to any other treatment before being transferred to the catalyst treatment device, depending on its composition.

In particular, in the present invention, it is preferable to bring the exhaust gas subjected to the thermal oxidative decomposition treatment into contact with water, that is, to subject it to a water washing treatment. Removal by entrainment, solubilization of water-soluble compounds such as SiF4, cooling of the processing gas, etc. can be performed. Although the method for this water washing treatment is arbitrary, it is preferable to contact the treatment gas in the form of a spray.

The water-washed gas subjected to catalytic treatment can be released into the environment, or can be further subjected to any other treatment as desired, such as known adsorption treatment, and can be discharged by any exhaust means, such as exhaust gas. A tube or the like can be provided in the catalyst treatment device. Furthermore, the washing wastewater is discharged out of the system through a drainage means such as a drain pipe, but this wastewater can be further processed. These water washing treatment means, discharge pipes, etc. can be provided in the heating oxidation decomposition apparatus.

The thermal oxidative decomposition method of the present invention oxidizes and decomposes the exhaust gas at high temperatures, so it can be processed in a short time, so even if there is a large amount of CVD exhaust gas, the removal efficiency is high. , air, nitrogen, and cooling water (which also serves as washing water) can be used to efficiently process the process, so the running cost is lower than that of the dry adsorption method.

[0022] The present invention can be provided with a control device so that the above processing steps are carried out continuously and automatically as a series, and desired processing conditions can be appropriately selected. This control device is usually connected to various sensing devices, such as sensors for temperature, pressure, water level, etc., and is configured to ensure safe and optimal processing at all times.

[0023]

[Operation] In the present invention, the thermal oxidation decomposition device is equipped with a CVD
The exhaust gas, preferably nitrogen for the sleeve, and air for oxidation flow in and are heated to 800°C or higher, thereby oxidizing TEOS and organic substances in the exhaust gas to form SiO2 and H2.
It becomes O, CO2. Further, the generated SiO2 is removed by washing water that also serves as a cooling for the exhaust gas. Due to the above-mentioned action, all substances other than CO, which has a low oxidation rate, are rendered harmless.

[0024] CO and the like in the exhaust gas pass through a catalytic device consisting of an oxidation catalyst packed bed, etc., where they are oxidized to CO2 and become harmless. If the catalyst is based on Mn or Cu oxides, it will have the ability to oxidize CO even at room temperature, but if moisture or organic matter coexists, the activity will drop quickly, so it is desirable to heat the catalyst to about 150°C. The reason for this is that heat exchange between the catalyst device and the exhaust gas is performed, and since the process can be performed at a high SV, the catalyst device is very compact and the life of the catalyst is long.

[0025] Therefore, although the treatment requires electricity for heating, water, and the cost of replacing the catalyst, the running cost can be significantly reduced compared to the adsorption method, and complete treatment can be achieved.

[0026]

EXAMPLE A specific example of the present invention will be described with reference to FIG. 1, but the present invention is not limited thereto.

FIG. 1 shows an example of a treatment apparatus used in the method of the present invention, and the CVD exhaust gas treatment apparatus 1 of the present invention is composed of a heating oxidation decomposition apparatus 2 and a catalytic reaction tank 3. The thermal oxidation decomposition device 2 includes an exhaust gas inflow pipe 4 for introducing CVD exhaust gas from the CVD device, a nitrogen inflow pipe 5 for introducing nitrogen for adjusting exhaust gas oxidation, and oxidizing thermal oxidation decomposable substances in the exhaust gas. A three-layered gas introduction section 7 concentrically configured with an air inflow pipe 6 for supplying oxygen to the gas, and a heat source for heating, oxidizing and decomposing the exhaust gas in the mixed gas released from the gas introduction section. A temperature-controlled reaction section 11 having a ceramic heater 8 on the outer wall and equipped with thermocouples 9 and 10, and a processing gas containing heated oxidation decomposition products generated in the reaction section 11 are washed with cooling water 12. Water washing section 13 for processing, F2, SiF4
It is composed of a drain pipe 14 for discharging waste water containing soluble substances such as SiO2, etc., to the outside of the system.

The catalytic reaction tank 3 is provided downstream of the thermal oxidation decomposition device 2, and the treated gas that has been washed with water is introduced into the catalytic reaction tank 3 through a supply pipe 15. The catalytic reaction tank 3 is
It is filled with an oxidation catalyst that oxidizes the introduced gas to be oxidized, such as CO, and by passing it through, the exhaust gas can be purified and rendered harmless. Discharge. Note that 17 to 19 are sampling tubes A, B, and C for exhaust gas, gas subjected to thermal oxidative decomposition/washing treatment, and gas subjected to catalyst treatment.

[0029]

[Experimental Example] A treatment test was conducted using the exhaust gas treatment device shown in Figure 1. Table 1 shows the treatment results of CVD exhaust gas using TEOS as a process gas.

[0030] The amount of exhaust gas is 40 L (liter)/min, the processing conditions of the heating oxidation decomposition device are a reaction temperature of 900°C, and N2 1
0 L/min, oxidizing air 20 L/min, and cooling water 4 L/min. Further, a column filled with a Cu, Mn-based catalyst was used as a catalytic reaction tank, and this was heated to 150° C. to treat the outflow gas from the thermal oxidation decomposition device at SV5,000.

As shown in Table 1, the catalyst had sufficient activity even after half a year. The exhaust gas treatment time during this period was 2 to 6 hours/day.

[0032]

[Table 1]

[0033]

Effects of the Invention: Harmful components of TEOS-based CVD exhaust gas can be completely removed by combining a thermal oxidation decomposition device and a compact catalytic reaction tank, and no harmful NOX is generated. Also,
Besides replacing the catalyst once every six months to a year, this method only requires electricity, water, nitrogen, and air, so maintenance is easy and the treatment cost is lower than that of the adsorption method.

[0034] In the oxidation treatment at 1000°C or lower, some organic substances remain, but the oxidation catalyst treatment has the effect that the remaining organic substances are oxidized and completely removed.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an NF3 exhaust gas treatment apparatus to which the method of the present invention is applied.

[Explanation of symbols]

1 CVD exhaust gas treatment equipment 2 Heating oxidation decomposition equipment 3 Catalytic reaction tank 4 Exhaust gas inflow pipe 5 Nitrogen inflow pipe 6 Air inflow pipe 7 Gas introduction part 8 Ceramic heater 9 Thermocouple 10 Thermocouple 12 Cooling water 13 Water washing section 14 Drain pipe 15 Supply pipe 16 Exhaust pipe 17 Sampling tube A 18 Sampling tube B 19 Sampling tube C

Claims (2)

[Claims] 1. A CV characterized in that after CVD exhaust gas is subjected to heating oxidation decomposition treatment, the gas subjected to heating oxidation decomposition treatment is brought into contact with an oxidation catalyst in the coexistence of oxygen to perform oxidation treatment.
D Exhaust gas treatment method. 2. A device comprising a device for thermally oxidizing and decomposing CVD exhaust gas, and a device provided after the device for oxidizing the heated, oxidatively decomposed gas by contacting it with an oxidation catalyst in the coexistence of oxygen. Features of CVD exhaust gas treatment equipment.