JPH0671529B2 - Method and apparatus for treating CVD exhaust gas - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic source such as an unreacted process gas in an exhaust gas in a CVD (chemical vapor deposition) process which is carried out in the production of semiconductors and an organic substance or CO generated by its decomposition. Contains harmful components such as. The present invention relates to purification of exhaust gas containing this harmful component to render it harmless.

[0002]

2. Description of the Related Art Conventionally, a wet scrubber or activated carbon adsorption is used for processing. The treatment with a wet scrubber has a problem that the removal rate of harmful components is low.

Further, the activated carbon adsorption system has problems that the cost of replacing the broken through activated carbon is high and CO cannot be removed. In addition, TEOS (tetraethoxysilane) and its decomposition components, organic substances, are flammable, and hydrogen gas and LPG
Although it can be processed at low cost by burning it as a combustion improver,
The flame temperature rises, the nitrogen in the exhaust gas is oxidized, and N
O _X it will be generated.

[0004]

In THE INVENTION It is an object object of the present invention to provide a cheaper running costs than conventional, to prevent NO _X generation is to provide all of the CVD exhaust gas treatment method and apparatus can detoxify harmful gas components.

[0005]

The present invention is a method and apparatus as described and described below, by which the above problems can be solved. A method for treating a CVD exhaust gas, which comprises subjecting a CVD exhaust gas to a thermal oxidative decomposition treatment, and then bringing the gas subjected to the thermal oxidative decomposition treatment into contact with an oxidation catalyst in the presence of oxygen to perform an oxidation treatment. A CVD exhaust gas, comprising: an apparatus for thermally oxidizing and decomposing CVD exhaust gas, and an apparatus which is provided at a subsequent stage of the apparatus and which performs an oxidizing treatment by bringing the gas subjected to the thermal oxidation decomposition processing into contact with an oxidation catalyst in the presence of oxygen. Processing equipment.

According to the present invention, a CVD exhaust gas is subjected to a thermal oxidative decomposition treatment, and a harmful unoxidized substance such as CO existing in the treated gas is brought into contact with a catalyst coexisting with oxygen to oxidize and detoxify the treated gas. However, since the oxidation treatment can be performed at a temperature at which NO _X is not produced,
Inexpensive treatment can be performed without causing secondary pollution.

The present invention can be constructed so that the temperature of the reaction part of the apparatus for thermally oxidizing and decomposing the thermally oxidatively decomposing substance present in the exhaust gas can be controlled, and a heating system using an electric heater is suitable.

Heating oxidatively decomposable substances in exhaust gas, for example,
Since TEOS, alcohol, aldehyde and the like have a high oxidation rate at 800 ° C. or higher, the temperature of the reaction part is preferably 800 to 1000 ° C. in consideration of the economical efficiency of the apparatus and the prevention of NO _x production.

In the treatment by the thermal oxidative decomposition apparatus used in the present invention, the CO oxidation rate in the exhaust gas is about 50% at 1000 ° C. or lower, but the Si produced by the oxidation of TEOS.
O ₂ is removed by washing with water, etc., and organic matter is removed by oxidative decomposition into CO ₂ and water.
O-oxidation, residual organic matter oxidation, etc. can be processed at high speed.

The catalyst is not particularly limited as long as it has oxidizing power, but one having CO oxidizing power is particularly preferable. Examples of the catalyst include Cu, Mn, Cu, Co, Cr and Pt.
Is preferable, and one or more of these oxides can be contained. Further, the form of these catalysts is also arbitrary, and on-thread, powdery, other materials, for example, composite materials with cellulose and the like can be used. Usually, the above-mentioned heat oxidative decomposition treatment gas inlet and oxidation treatment are carried out. A desired amount of the gas can be filled or loaded in a container provided with an outlet for the gas.

The oxide catalyst can be treated at a relatively low temperature and is particularly effective. In that case, the temperature may be 150 ° C. or higher at which the influence of moisture and residual organic matter is eliminated. Also,
From the oxidation rate of the catalyst, the SV (flow rate) of the gas subjected to the thermal oxidative decomposition treatment in the catalytic device is about 20,000 1 / h, but there is no problem, but in order to reduce the pressure loss,
It is desirable to process at 1 / h to 10,000 1 / h.

As for the oxygen supplied to the catalyst, the oxygen necessary for the thermal oxidative decomposition may be supplied to the reaction part, and the remainder consumed for the thermal oxidative decomposition may be used, or it may be supplied separately to the catalyst. You may

The CVD exhaust gas in the present invention means CVD
Mainly the exhaust gas after the CVD treatment of the process gas used in the CVD (chemical vapor deposition) method from the apparatus, but in some cases, the exhaust gas at the time of cleaning after using the gas for cleaning the CVD apparatus Can also be included.

CV for giving CVD exhaust gas in the present invention
Examples of the D raw material, that is, the process gas include known ones. For example, inorganic raw materials such as monosilane, disilane, and dichlorosilane, organic raw materials such as TEO.
S (tetraethoxysilane) and the like, which are used alone or in combination. These exhaust gases include unreacted products or their derivatives, reaction decomposition products, for example, alcohols such as H ₂ , CO and C ₂ H ₅ OH, aldehydes such as CH ₃ CHO and hydrocarbons such as C ₂ H _4. And the like are mainly contained in a metal oxide such as SiO ₂ and H by being oxidized and decomposed by heating.
It becomes ₂ O and CO ₂ . It is clear that the thermal oxidative decomposition referred to here includes mere oxidization of non-decomposable substances, for example, oxidization of simple substances such as hydrogen and metals.

As the cleaning gas, NF ₃ , CF
₄ , C ₂ F ₆ , SF ₆ , ClF _{3 and the} like. The cleaning exhaust gas is a reaction product of the cleaning gas and a substance in the CVD apparatus (unexhausted CVD treated substance, etc.), for example, SiF ₄ , cleaning gas. It is composed of a derivative and the like, and a cleaning gas and a substance in CVD physically cleaned by the cleaning gas.

The reaction conditions for the heat oxidative decomposition treatment and the conditions for introducing the exhaust gas in the present invention are not particularly limited, but at least the heat oxidatively decomposable substance contained in the exhaust gas is thermally oxidatively decomposed in the presence of oxygen. Just do it. Therefore,
When introducing the exhaust gas into the thermal oxidation decomposition apparatus, it is necessary that oxygen be present in the thermal oxidation reaction section at the same time. The method of existence of this oxygen is arbitrary, but it is usually preferable to introduce the oxygen together with the exhaust gas as an oxygen-containing gas such as air. Further, any gas can be mixed in order to adjust the conditions of thermal oxidative decomposition. For example, it is preferable that an inert gas such as nitrogen is mixed and introduced into the reaction part of the thermal oxidative decomposition apparatus in a three-layer state such that the nitrogen gas wraps the exhaust gas and oxygen wraps them. It is preferable to provide a concentric tube having a three-layer structure as the gas introduction section.

Further, the heating means in the thermal oxidative decomposition treatment is also optional, but preferably the heater heating system capable of electrically controlling the temperature as described above is desirable, and it can be usually provided in the wall of the reaction section. The temperature of the reaction part is 8
The range of 00 to 1000 ° C. is preferable. When the temperature is 1000 ° C. or higher, NO _X is generated by the oxidation of N ₂ gas, which is not preferable.

In the present invention, the exhaust gas subjected to the heat oxidative decomposition treatment may be transferred to the catalyst processing device as it is, or it may be transferred to the catalyst processing device after further optional treatment.

Particularly, 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, whereby the metal oxide fine particles such as SiO ₂ produced by the decomposition treatment. Can be removed by entrainment, removal by solubilization of water-soluble compounds such as SiF ₄ , and cooling of the processing gas. The method of this water washing treatment is arbitrary, but it is preferable to bring it into contact with the treatment gas in a spray form.

The gas obtained by subjecting the gas washed with water to catalytic treatment can be released into the environment or, if desired, subjected to other arbitrary treatments, for example, known adsorption treatments. A tube or the like can be provided in the catalyst treatment device. Further, the wash drainage is discharged to the outside of the system by drainage means such as a drain pipe, and this drainage can be further processed. These washing treatment means, discharge pipe, etc. can be provided in the thermal oxidation decomposition apparatus.

In the thermal oxidative decomposition method of the present invention, the exhaust gas is oxidatively decomposed at a high temperature so that the exhaust gas can be treated in a short time. Since it can be efficiently treated with air, nitrogen, and cooling water (which also serves as washing water), the running cost is lower than that of the dry adsorption method.

The present invention can be provided with a control device so that the above-mentioned processing steps can be continuously and automatically carried out as a series, and desired processing conditions can be appropriately selected. This control device is usually in communication with various detection devices, for example, sensors for temperature, pressure, water level, etc., and is constructed so as to be always safe and to perform optimum processing.

[0023]

In the present invention, the thermal oxidative decomposition apparatus is CVD
Exhaust gas, preferably nitrogen for sleeves, and air for oxidation flow in and are heated to 800 ° C. or higher, whereby TEOS and organic substances in the exhaust gas are oxidized and SiO ₂ , H
It becomes ₂ O and CO ₂ . Further, the generated SiO ₂ is removed by washing water which also serves to cool the exhaust gas. By the above action, all but CO, which has a low oxidation rate, is rendered harmless.

CO and the like in the exhaust gas pass through a catalyst device composed of an oxidation catalyst packed bed and the like, and are oxidized to CO _{2 and the} like to be harmless. If the catalyst is of Mn or Cu oxide type, it has an oxidizing power of CO even at room temperature, but it is desirable to heat it because the activity decreases quickly when water and organic substances coexist, and the catalyst is heated to about 150 ° C. It is sufficient to perform heat exchange between the catalyst device and the exhaust gas, and since the treatment can be performed at high SV, the catalyst device is very compact and the life of the catalyst is long.

Therefore, the treatment requires the heating electric power, water and the exchange cost of the catalyst, but the running cost can be greatly reduced as compared with the adsorption method, and the complete treatment can be performed.

[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 processing apparatus used in the method of the present invention. A CVD exhaust gas processing apparatus 1 of the present invention comprises a thermal oxidative decomposition apparatus 2 and a catalytic reaction tank 3. The thermal oxidative decomposition apparatus 2 oxidizes an exhaust gas inflow pipe 4 for introducing the CVD exhaust gas from the CVD device, a nitrogen inflow pipe 5 for introducing nitrogen for adjusting the exhaust gas oxidation, and a thermally oxidative decomposable substance in the exhaust gas. A gas introduction part 7 having a three-layer structure in which an air inflow pipe 6 for supplying oxygen is concentrically formed, and a heat source for thermally oxidizing and decomposing exhaust gas in the mixed gas discharged from the gas introduction part. A reaction part 11 having a certain ceramic heater 8 on the outer wall and having thermocouples 9 and 10 controlled in temperature, and a process gas containing a heated oxidative decomposition product produced in the reaction part 11 are washed with cooling water 12. It comprises a water washing section 13 for treatment and a drain pipe 14 for discharging waste water containing soluble substances such as F ₂ and SiF ₄ and SiO ₂ to the outside of the system.

The catalytic reaction tank 3 is provided at the subsequent stage of the thermal oxidative decomposition apparatus 2, and a processing gas which 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 for oxidizing the introduced gas such as CO to be oxidized, and the exhaust gas can be purified and rendered harmless by passing therethrough. Discharge. In addition, 17 to 19 are respective sampling pipes A, B, and C for the exhaust gas, the gas subjected to the thermal oxidative decomposition / washing treatment, and the gas subjected to the catalytic treatment.

[0029]

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

The amount of exhaust gas was 40 L (liter) / min, and the processing conditions of the thermal oxidative decomposition apparatus were as follows: reaction temperature 900 ° C., N ₂ 10
L / min, oxidizing air 20 L / min, and cooling water 4 L / min. A column filled with Cu and Mn-based catalyst was used as a catalytic reaction tank, which was heated to 150 ° C. and the outflow gas of the thermal oxidation decomposition apparatus was treated with SV5,000.

As shown in Table 1, the catalyst was sufficiently active 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 By combining a thermal oxidation decomposition apparatus and a compact catalytic reaction tank, harmful components of TEOS-based CVD exhaust gas can be completely removed, and harmful NO _x is not generated. In addition, electricity, water, nitrogen, etc. other than replacing the catalyst once every six months to one year
Since only air is required, maintenance is easy and the processing cost is low compared to the adsorption method.

Although a small amount of organic matter remains in the oxidation treatment at 1000 ° C. or lower, there is also an effect that the remaining organic matter is oxidized and completely removed in the oxidation catalyst treatment.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an NF ₃ exhaust gas treatment apparatus to which the method of the present invention is applied.

[Explanation of symbols]

 1 CVD Exhaust Gas Processing Device 2 Thermal Oxidation Decomposition Device 3 Catalytic Reaction Tank 4 Exhaust Gas Inflow Pipe 5 Nitrogen Inflow Pipe 6 Air Inflow Pipe 7 Gas Introducing Section 8 Ceramic Heater 9 Thermocouple 10 Thermocouple 12 Cooling Water 13 Rinsing Section 14 Drain 15 Supply Pipe 16 Exhaust pipe 17 Sampling pipe A 18 Sampling pipe B 19 Sampling pipe C

Claims (2)

[Claims] 1. A CVD method in which a CVD exhaust gas is subjected to a thermal oxidative decomposition treatment, and then the gas subjected to the thermal oxidative decomposition treatment is brought into contact with an oxidation catalyst in the presence of oxygen to perform an oxidizing treatment.
Exhaust gas treatment method. 2. An apparatus for thermally oxidizing and decomposing CVD exhaust gas, and an apparatus which is provided at a subsequent stage of the apparatus and which performs the oxidizing treatment by bringing the gas subjected to the thermally oxidative decomposition into contact with an oxidation catalyst in the coexistence of oxygen. Characteristic CVD exhaust gas treatment equipment.