JPS6348576B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a treatment device for halogen-based waste gas containing CCl ₄ , and in particular for dry etching waste gas such as CCl ₄ , which is chemically stable and difficult to process. To provide an apparatus capable of efficiently and surely removing toxic halogen gas contained in etc., and improving the durability of the device.

<Prior Art> At present, halogen-based gases are widely used not only for dry etching and doping for semiconductors, but also for optical fibers, excimer lasers, and the like.

However, this halogen-based gas is highly toxic, so after use, it must be diluted with an inert gas or gaseous fluoride, and the halogen-based waste gas must be diluted to a safe low concentration of toxic gases. need to be processed.

As a treatment device for waste gas containing halogen-based toxic gases, for example, waste gas containing _F2 can be treated with soda lime,
There are known devices that treat F2-containing waste gas at room temperature with activated alumina, etc., as well as devices that treat _F2 -containing waste gas with carbonated lime or slaked lime, as described in Japanese Patent Publication No. 54-35191. A method for treating HCl-containing gas with granular calcined dolomite is disclosed in Japanese Patent Publication No. 1983-92, and a method for treating HCl-containing gas with granular calcined dolomite is disclosed in Japanese Patent Publication No. 57-92.
-150526, respectively.

<Problems to be solved by the invention> Actually, dry etching waste gas contains Cl ₂ ,
CCl ₄ is often included in addition to BCl ₃ , SiCl _{4 ,} etc., and while the former three react relatively easily with aqueous alkaline solutions, CCl ₄ is stable and reacts with aqueous alkaline solutions as well. Therefore, there is currently no effective device for wet treatment of CCl ₄ -containing halogen waste gas.

Furthermore, as a device for dry processing the CCl ₄ -containing waste gas, a processing device filled with powdered activated carbon is known, and the activated carbon adsorbs and removes CCl ₄ .

However, in the adsorption treatment apparatus described above, there is a risk that CCl ₄ will be desorbed again, and if the treatment continues for a long time, there is also a possibility that the adsorption capacity for CCl ₄ will decrease.

On the other hand, as mentioned above, there are many types of dry processing equipment for halogen waste gases other than CCl ₄ , but even if halogen waste gas with a low concentration is brought into contact with solid processing agents such as soda lime, the Removal efficiency is often low, and the equipment often becomes corroded and cannot withstand long-term treatment.

The technical problem of the present invention is to reliably eliminate CCl ₄ , which is difficult to process, and other halogen gases even if the concentration thereof is low, and to enable long-term use of a processing device.

<Means for solving the problem> (1) As a result of various studies, starting from the idea that CCl ₄ is hydrolyzed using iron or aluminum as a catalyst, we found that CCl ₄ can be converted to CCl 4 using aluminum oxide as a reactant in the presence of water. It can be assumed that when exposed to water, a hydrolysis reaction occurs and decomposition into HCl, CO ₂ and AlCl ₃ , which are easy to treat. (2) If the solid processing agent contains water, contact with halogen gas We have newly discovered that reducing the area reduces the removal efficiency, and that the above moisture reacts with halogen gases to generate acidic gases such as HCl and HF, which accelerates corrosion of the equipment. The present invention was completed based on this.

That is, the present invention incorporates a solid treatment layer into a processing device, connects a gas introduction line to the inlet of the processing device, and connects a gas outlet line to the outlet thereof,
In a treatment device for halogen-based waste gas containing CCl ₄ , the halogen-based waste gas containing CCl ₄ is introduced through the gas introduction line, the concentration of the halogen-based gas is reduced in a solid treatment layer, and the halogen-based waste gas is led out from the gas outlet line. At least downstream of the moisture-containing aluminum oxide treatment layer, a soda lime treatment layer that has been previously dehydrated and dried is arranged in series to form a solid treatment layer, and in the first stage, CCl ₄ -containing halogen waste gas is removed. It is characterized in that CCl ₄ is decomposed and removed by passing through an aluminum oxide treatment layer, and in the second stage, other halogen gases other than CCl ₄ are removed by a soda lime treatment layer.

The soda lime filled in the solid treatment layer is in the form of granules or powder.

The soda lime is previously subjected to dehydration and drying treatment before being brought into contact with the waste gas. This treatment may be carried out by vacuum drying at room temperature, but it is preferable to heat dry at 300° C. for about 5 hours.

The above aluminum oxide is industrially α type, γ type
Type alumina, whether in granular or powder form. Further, hydrated alumina having crystal water is preferable, but hydrated alumina without crystal water may also be used. In this case, it is necessary to supplement moisture with a separate processing agent.

The above-mentioned processing apparatus may be one in which two reaction tubes are connected in series and the solid treatment layer is housed in each reaction tube, or one in which the solid treatment layer is housed all together in one reaction tube. No problem.

The solid treatment layer is formed by arranging a soda lime treatment layer in series at least on the downstream side of the aluminum oxide treatment layer, and is formed in two layers such as the aluminum oxide treatment layer → soda lime treatment layer, It is also possible to add a soda lime treatment layer upstream of the aluminum oxide treatment layer to form a three-layer structure.

<Function> When the CCl ₄ -containing halogen waste gas introduced from the gas introduction line comes into contact with the aluminum oxide treatment layer on the upstream side, the CCl ₄ contained therein is stoichiometrically hydrated by aluminum oxide and water. HCl, CO ₂ , which undergoes a decomposition reaction and is easy to treat,
It can be estimated that it will be decomposed into AlCl ₃ .

Other halogen gases except _CCl4 , such as _Cl2 ,
BCl ₃ , SiCl ₄ , F ₂ , BF ₃ and the like pass through the aluminum oxide treatment layer without being decomposed and reach the soda lime treatment layer on the downstream side.

Therefore, the soda-lime treatment layer is contacted with HCl generated by decomposition of CCl ₄ and other halogen gases other than CCl ₄ that have passed through the aluminum oxide treatment layer, and these are removed all at once.

In this case, since the soda lime has been dehydrated and dried in advance, the surface of the soda lime is not covered with moisture, and a large surface area of the soda lime that can come into contact with the waste gas can be ensured.

In addition, since most of the moisture in soda lime is removed, halogen gases in waste gas, such as
Cl ₂ , BCl ₃ , F ₂ , etc. react with this moisture to form HCl,
This eliminates the possibility of generating acidic gas such as HF and causing corrosion of the equipment.

However, corrosion of processing equipment occurs when acidic gas is generated in the presence of moisture, and HCl generated by decomposition of CCl ₄ flows from upstream into the soda lime layer from which almost all moisture has been removed. However, since it is not ionized by moisture, there is no corrosion of the equipment.

As a result, when CCl ₄ -containing halogen gas is passed through the processing equipment, CCl ₄ is first decomposed and removed in the aluminum oxide treatment layer, and other halogen gases are removed in the soda lime treatment layer, so that they are removed from the gas outlet line. In this case, halogen-based gases whose concentration is reduced to below the permissible limit are discharged.

<Effects of the invention> (1) In the aluminum oxide treatment equipment, CCl ₄
is decomposed stoichiometrically, so even if the waste gas contains _CCl4 diluted to a low concentration, as long as the reactants aluminum oxide and water are present in the treatment equipment, the hydrolysis reaction can continue effectively. ,surely
CCl ₄ can be reduced to below permissible limits.

In addition, since CCl ₄ is decomposed into other substances that are easy to process, there is no risk that CCl ₄ will be desorbed again as in _an adsorption reaction.
can be fundamentally eliminated.

Furthermore, since a large surface area of soda lime that can come into contact with waste gas can be ensured in the soda lime treatment layer, even a low concentration of halogen waste gas can be sufficiently removed to a concentration below the permissible limit.

This makes it possible to reliably eliminate dry etching waste gas and the like containing various halogen-based gases, including _CCl4 , even if the concentration thereof is low.

(2) Since most of the moisture in soda lime can be removed, no acid gas is generated even when it comes into contact with halogen-based gas, and even if HCl flows into the soda lime treatment layer from the upstream side, it will not be converted to moisture. As it is not ionized, there is no corrosion of processing equipment.
Processing can be continued for a long period of time.

(3) Since the soda lime treatment layer on the downstream side is solid, if the aluminum oxide treatment layer on the upstream side is filled with hydrated alumina, the _CCl4- containing halogen-based waste gas can be easily and quickly dry-treated.

Moreover, if the process is carried out in a dry manner, the structure of the entire apparatus can be simplified.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a schematic explanatory diagram of a processing apparatus showing a first embodiment, in which a gas introduction line 3 is connected to an inlet 2 of the processing apparatus 1 via an in/off valve 4, and a gas outlet line is connected to an outlet 5 of the processing apparatus 1. 6 is connected via an on/off valve 7.

A rotary pump 8 is connected to the gas introduction line 3 so that the CCl ₄ -containing halogen-based waste gas can be diluted with an inert gas such as N ₂ and then pumped to the processing device 1 .

As mentioned above, the CCl ₄ -containing halogen-based waste gas refers to the dry etching waste gas generated during the semiconductor manufacturing process, and specifically, in addition to containing CCl ₄ , it also contains Cl ₂ ,
Chlorine-based toxic gases such as HCl, BCl ₃ , SiCl ₄ , SiH ₂ Cl ₂ , and F ₂ , HF, BF ₃ , SiF ₄ , GeF ₄ , MoF ₆ ,
At least one type of fluorine-based toxic gas such as WF ₆ coexists.

Further, for safety, the toxic halogen gas is diluted with a predetermined gas to lower its concentration, and then introduced into the processing device as waste gas.

In addition, the above dilution gas includes N ₂ , CO ₂ , He, Ar,
An inert gas such as Ne or an inert gaseous fluoride such as CF ₄ , C ₂ F ₆ or SF ₆ is used.

The processing apparatus 1 is constructed by connecting two vertical fixed bed reaction columns 10 and 12 in series via an on/off valve 16.

An aluminum oxide treatment layer 14 filled with granular hydrated alumina is installed in the upstream reaction column 10 .

A heater is attached to the peripheral wall of the reaction tube 10, and a temperature sensor such as a CA thermocouple is embedded in the processing layer 14, so that the temperature inside the tube can be adjusted.

Further, a soda lime treatment layer 15 filled with powdered soda lime is installed in the reaction tube 12 on the downstream side, and a heater is provided inside the tube like the reaction tube 10 described above.

As mentioned above, the soda lime is dehydrated and dried in advance to remove moisture and ensure a large contact area with the waste gas.

Therefore, for example, to describe the function of the above treatment device when chlorine-based dry etching waste gas is passed through, first, the temperature of the hydrated alumina-filled reaction tube 10 is controlled.
The temperature of the soda-lime-filled reactor 12 was set at 350°C and 250°C.
℃, and the chlorine-based gas discharged from the etching apparatus is diluted with N ₂ by the rotary pump 8 and then introduced into the processing apparatus 1 through the gas introduction line 3.

When halogen-based waste gas containing CCl ₄ , Cl ₂ , BCl ₃ , etc. enters the treatment device 1 , CCl ₄ is first decomposed and removed by the aluminum oxide treatment layer 14 , and other gases pass through without undergoing a decomposition reaction. Put it away.

CCl ₄ undergoes a hydrolysis reaction to form HCl, CO ₂ ,
It is estimated that it is decomposed into AlCl ₃ , of which
AlCl ₃ is cooled along the line from the outlet of the reaction tube 10 to the downstream side and solidifies within these inner walls, while other HCl and CO ₂ reach the reaction tube 12 on the downstream side.

In the reaction tube 12, chlorine-based gases such as Cl ₂ and BCl ₃ that have passed through the upstream reaction tube 10 and the reaction tube 1
The HCl decomposed at 0 is treated with soda lime and removed below acceptable limits.

In this case, as shown by the imaginary line in FIG.
If the cut-off valve 16 is replaced with a three-way valve and the bypass line 17 is connected between the two inlet and cut-off valves 4 and 16, for example, if the halogen-based waste gas does not contain CCl ₄ , the waste gas will be It is sufficient to simply pass the gas through this bypass line 17 and treat it directly in the soda-lime-filled reactor 12.

On the other hand, FIG. 2 shows a second embodiment of the present invention, in which the processing apparatus 1 is formed from one reaction tube 18, and an aluminum oxide treatment layer 14 is provided on the upstream side of the processing apparatus.
Furthermore, a two-layer soda lime treatment layer 15 is incorporated on the downstream side thereof.

In this embodiment, only one reaction tube is required, and the structure of the entire processing apparatus can be simplified.

FIG. 3 shows a third embodiment of the present invention, in which a treatment apparatus 1 is formed of one reaction tube 20, and inside the treatment apparatus there is a soda lime treatment layer 15, an aluminum oxide treatment layer 1.
4 and a soda-lime treated layer 15 are assembled in a sandwich-like pattern.

In this embodiment, halogen-based gases other than CCl ₄ can be removed in a double manner, and it is suitable for rapidly processing a large amount of waste gas.

Furthermore, in the case of the above-mentioned three-layer treatment, one additional soda-lime-filled reaction tube 10 is connected to the upstream side of the two-layer reaction tube 18 used in the second embodiment, and this whole is formed as the treatment apparatus 1. It's okay to do that.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a schematic explanatory diagram of a processing device showing the first embodiment, FIG. 2 is a diagram corresponding to FIG. 1 showing the second embodiment, and FIG. 3
FIG. 1 is a diagram corresponding to FIG. 1 showing an embodiment. 1... Processing device, 2... Inlet of 1, 3... Gas introduction line, 5... Outlet of 1, 6... Gas outlet line, 10, 12, 18, 20... Reaction column, 14
...Aluminum oxide treatment layer, 15...Soda lime treatment layer.

Claims (1)

[Claims] 1. A solid treatment layer is installed in the treatment device, and a gas introduction line is connected to the inlet of the treatment device, and a gas outlet line is connected to the outlet of the treatment device, so that the CCl4 _- containing halogen-based waste gas is converted into the above-mentioned gas. In a treatment device for halogen-based waste gas containing CCl ₄ , which is introduced from an inlet line, the concentration of the halogen-based gas is reduced in a solid treatment layer, and then led out from a gas outlet line, at least one of the aluminum oxide treatment layers containing moisture is treated. On the downstream side, soda lime treatment layers that have been dehydrated and dried in advance are arranged in series to form a solid treatment layer, and in the first stage, the CCl ₄ -containing halogen waste gas is passed through the aluminum oxide treatment layer to convert CCl ₄ into A treatment device for halogen-based waste gas containing CCl ₄ , characterized in that the halogen-based gases other than CCl ₄ are removed by decomposition and removed in a second stage using a soda lime treatment layer. 2. The treatment device is formed from two reaction tubes connected in series, and the upstream reaction tube houses an aluminum oxide treatment layer, and the downstream reaction tube houses a soda lime treatment layer. A treatment device for halogen-based waste gas containing CCl ₄ according to claim 1. 3. Claim 1, characterized in that the treatment device is formed from one reaction tube, and an aluminum oxide treatment layer is housed in a laminated manner on the upstream side of the reaction tube and a soda lime treatment layer is housed on the downstream side. A treatment device for halogen-based waste gas containing CCl ₄ as described above. 4. The treatment device as set forth in claim 1, wherein the treatment device is formed from one reaction tube, and the reaction tube houses a soda lime treatment layer, an aluminum oxide treatment layer, and a soda lime treatment layer in the shape of a sandwich arch.
Treatment equipment for halogen waste gas containing CCl ₄ . 5 Claims 1 to 4 characterized in that the aluminum oxide accompanied by moisture is hydrated alumina.
A treatment device for halogen-based waste gas containing CCl ₄ according to any one of the above items.