JPH0421523B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for detoxifying gases containing toxic gas components such as silane, arsine, phosphine, and diborane, particularly gases emitted during semiconductor manufacturing processes. be.

Conventional technology In the semiconductor manufacturing process, silane, which is used for crystal growth, doping, film formation, etc.
Gases such as arsine, phosphine, and diborane are exhausted along with balance gases such as hydrogen, nitrogen, helium, and argon. Gases such as silane, arsine, phosphine, and diborane are toxic, so it is necessary to remove the toxic gases contained in the exhaust gases before they are released into the atmosphere.

Various methods have been known to remove these toxic gases, but most of them remove a single toxic gas component, whereas many methods remove a mixture of various components such as silane, arsine, phosphine, and diborane. It was often not applicable in cases where

Therefore, as a treatment method for exhaust gas when various types of toxic gases are mixed, (A) combustion oxidation method using a combustion furnace, more specifically, gas containing toxic gas components generated during semiconductor manufacturing is treated with city gas A method of mixing with air and burning, then cooling the combustion gas, and then absorbing the combustion products into activated carbon or absorption liquid (for example, Japanese Patent Application Laid-open No. 49-54268), (B) silane, etc. A method has been proposed in which pyrophoric gas is first combusted, and then other toxic gas components are removed using an appropriate adsorbent.

Problems to be Solved by the Invention However, the above method (A) has problems such as complicated operating operations and excessive operating costs.

In addition, in method (B) above, fine particles of SiO ₂ , which is a combustion oxide of silane, often adhere to the adsorbent in the subsequent process, causing problems such as clogging.
This method requires a complicated process for removing combustion oxides of silane, and cannot necessarily be said to be an effective method.

The present invention has been made to solve these conventional problems.

Means for Solving the Problems The present invention provides a method for detoxifying gases containing toxic gas components such as silane, arsine, phosphine, and diborane by bringing the gas into contact with activated carbon impregnated with an adsorption enhancer. A first step of removing toxic gas components other than silane in the gas is carried out, and then the gas derived from the first step is led to a silane treatment system to carry out a second step of removing silane from the gas. A method for processing gas containing toxic gas components, characterized by:

By adopting a specific process sequence in which toxic gas components other than silane are first treated, and then silane is treated, the above problems can be completely solved. I've reached it.

The method of the present invention will be explained in detail below.

First step In the present invention, first, activated carbon impregnated with an adsorption enhancer is brought into contact with a gas containing toxic gas components such as silane, arsine, phosphine, diborane, etc.
The first step is to remove toxic gas components other than silane from the gas.

Poisonous gases include hydrides and halides of elements such as silicon, arsenic, phosphorus, boron, selenium, germanium, and halogen, with typical examples being silane, arsine, phosphine, and diborane.

Examples of gases containing these toxic gases include exhaust gases used for purposes such as crystal growth, doping, and film formation in semiconductor manufacturing processes. This gas usually contains toxic gases such as silane, arsine, phosphine, diborane, etc. as minor components, and balance gases such as hydrogen, nitrogen, helium, argon, etc. as major components.

In addition, exhaust gases from the manufacturing process of optical fibers and so-called new ceramics, gases generated from coke ovens, blast furnaces, and converter furnaces, petroleum fraction cracking gas, natural gas, and gases that gush out from pumping up groundwater are also included. The method of the present invention can be applied to remove toxic gas components contained therein.

Adsorption enhancers include (a) copper compounds, such as carbonates, basic carbonates, nitrates, sulfates, phosphates, organic acid salts, hydroxides, oxides, halides, etc.; (b) copper; combination of the compound with a compound selected from alkali metal compounds, alkaline earth metal compounds, aluminium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, cadmium, lead compounds, (c) heavy Examples include chromate, (d) ammoniacal silver chromate, (e) permanganate, (f) silver nitrate, and (g) iron compounds.

Activated carbon manufactured from raw materials such as coconut shells, coal, coke, charcoal, and petroleum pit is used as the activated carbon, and its shape may be arbitrary, such as crushed, various molded shapes, and fibrous.

By impregnating the above-described adsorption enhancer with the activated carbon, an adsorption enhancer-impregnated activated carbon can be obtained. By bringing the impregnated activated carbon into contact with a gas containing toxic gas components, toxic gas components other than silane in the gas are adsorbed and removed.

Note that, depending on the type of impregnated activated carbon, some exhibit high adsorption capacity in the presence of air (oxygen), while others exhibit high adsorption capacity even when air (oxygen) is not mixed. Therefore, when the former impregnated activated carbon is used and the gas does not contain oxygen, it is required to introduce air into the gas prior to the contact between the gas and the impregnated activated carbon. However, if this is done, the silane may oxidize and become SiO ₂ and adhere to the impregnated activated carbon, causing clogging of the adsorption tower. It is desirable to dilute the system.

For the adsorption treatment using impregnated activated carbon, industrially, it is advantageous to use a method in which an adsorption tower is filled with impregnated activated carbon and gas is introduced therein. In this case, a plurality of towers are arranged in parallel, and while gas is being supplied to one tower to perform adsorption treatment, the impregnated activated carbon in the other towers is replaced or activated. Furthermore, since it is necessary to switch towers before reaching the breakthrough point, it is desirable to take appropriate means for recognizing the breakthrough point, such as installing a sensor at an appropriate position on the tower.

Second Step In the present invention, the gas derived from the first step is introduced into a silane treatment system to remove silane from the gas.

Various methods are used for the silane treatment system, including a method in which gas is brought into contact with a silane treatment agent, and a method in which silane is removed from the gas by a combustion method. It is advantageous for

When using a silane treatment agent, the treatment agent is:
Aqueous solutions of alkali hydroxides such as sodium hydroxide and potassium hydroxide are preferred; in this case, inorganic salts such as sodium chloride, potassium chloride, ammonium chloride, calcium chloride, sodium sulfate, ammonium sulfate, and sodium nitrate are used together with the alkali hydroxides. You can also do that. Industrially, it is advantageous to bring the gas derived from the first step into contact with the aqueous treatment agent solution using a device such as a jet scrubber or a rotary atomizer.

Examples Next, examples will be given to further explain the method of the present invention.

Example 1 FIG. 1 is a flow sheet showing an example of the method of the present invention, and this example is suitable when using impregnated activated carbon that has a high adsorption capacity without mixing air.

1 surrounded by a dotted line indicates a first step of collecting toxic gas components other than silane, and 2 surrounded by a dotted line indicates a second step of treating silane.

3 is a reactor, from which silane is derived,
A gas containing arsine, phosphine, diborane, etc. is introduced into the first step 1 via a vacuum pump 4 and a filter 5, which are provided as necessary.

The first step 1 consists of two adsorption towers 6 and 6 in terms of equipment.
Consists of the associated piping and valves.

The adsorption tower 6 is filled with activated carbon impregnated with an adsorption enhancer, and the gas introduced into one of the adsorption towers 6 comes into contact with the impregnated activated carbon to produce arsine, phosphine,
Poisonous gas components other than silane such as diborane are adsorbed and removed. Just before one adsorption tower 6 reaches its breakthrough point, the gas flow is switched to the other adsorption tower 6, and the contents of the previous adsorption tower 6 are replaced with fresh impregnated activated carbon or subjected to activation. Ru. The conduit 7 is a conduit for cleaning various parts of the apparatus, and an inert gas such as nitrogen gas is introduced from this conduit.
8 is a water tank for absorbing moisture from inert gas;
It will be established as necessary.

The second step 2 consists of a jet type scrubber 9 and associated equipment and piping.

The scrubber 9 contains, for example, an aqueous solution 10 of sodium hydroxide, and this aqueous solution is sent to the upper part of one end of the scrubber 9 by a pump 11 and is ejected from a nozzle 12. This eruption is
It plays the role of atomizing the aqueous solution and drawing gas into the scrubber 9 by making the system negative pressure. The sprayed aqueous solution comes into contact with the gas introduced near the nozzle 12, and the silane in the gas is removed. The treated gas is discharged from the upper space on the other end side of the scrubber 9 by a blower 13 . 14 is a filling that prevents droplets from being entrained outside the system.

The scrubber 9 can be operated in batches, but when operated continuously, the scrubber 9 is replenished with fresh sodium hydroxide aqueous solution at a constant rate and a portion of the aqueous solution 10 is discharged to the outside.

Using the above apparatus and using APRC-2 manufactured by Takeda Pharmaceutical Company Limited as the impregnated activated carbon,
5000ppm, arsine 1000ppm, phosphine
Hydrogen gas containing 1000ppm and diborane was processed, and the operation was smooth and the concentration of toxic gas components in the exhaust gas from the second process could be safely discharged into the atmosphere. We were able to reduce it below the level.

Example 2 Figure 2 is a flow sheet showing another example of the method of the present invention, and this example is suitable when using impregnated activated carbon that exhibits high adsorption capacity in the presence of air. .

In this embodiment, air is introduced through the pipe 15, thereby increasing the adsorption activity of the impregnated activated carbon filled in the adsorption tower 6. However, the inclusion of air causes oxidation of the silane in the gas, resulting in the formation of SiO ₂
may cause clogging of the adsorption tower 6 and impede the smooth operation of the adsorption tower 6.
Before air is mixed in from 5, an inert gas for dilution, such as nitrogen gas, is introduced through pipe 16.
Since the concentration of silane that causes oxidation is approximately 5000 ppm or more, the gas is diluted with an inert gas so that the silane concentration in the gas is less than that.

The meanings of other structures and quotation marks in Figure 2 are as follows.
Since it is the same as the case shown in the figure, the explanation will be omitted.

Using the above apparatus and APRC-1 manufactured by Takeda Pharmaceutical Company Limited as impregnated activated carbon, silane
5000ppm, arsine 1000ppm, phosphine
Hydrogen gas containing 1000ppm and diborane 1000ppm was treated. Note that before the supplied gas reached the adsorption tower 6, nitrogen gas was introduced through the pipe 16 to dilute the silane concentration to 1000 ppm or less, and air was introduced through the pipe 15. The gas treatment operation could be carried out smoothly, and the concentration of toxic gas components in the exhaust gas from the second step could be reduced to a level that could be safely discharged into the atmosphere.

Effect In Example 1 and FIG. 1, the gas containing toxic gas components sent from the reactor 3 comes into contact with the impregnated activated carbon in the adsorption tower 6 to remove toxic gas components other than silane such as arsine, phosphine, and diborane. is adsorbed and removed, and then silane is removed by contact with a sprayed aqueous sodium hydroxide solution in a scrubber 9, and all toxic gas components contained in the gas discharged from the reactor 3 are removed.

Furthermore, in Example 2 and FIG. 2, the gas containing toxic gas components sent from the reactor 3 is diluted with an inert gas introduced from the pipe line 16 before reaching the adsorption furnace 6, and then It is mixed with air introduced from pipe 15 and sent to adsorption tower 6, where it comes into contact with impregnated activated carbon to adsorb and remove toxic gas components other than silane, such as arsine, phosphine, and diborane. Silane is removed by contacting with an aqueous sodium hydroxide solution,
All toxic gas components contained in the gas discharged from the reactor 3 are removed.

Effects of the Invention In the present invention, unlike conventional methods, toxic gas components other than silane such as arsine, phosphine, and diborane are first removed using impregnated activated carbon in the first step, and then silane is removed in the second step. Since the array is adopted, even if the gas contains various types of toxic gas components, the toxic gas components can be efficiently removed. Further, troubles such as clogging of the adsorption tower caused by the prior art silane removal process are prevented, and the removal of toxic gas components from the gas can be carried out smoothly over a long period of time.

The method of the present invention is also advantageous in cases where the toxic gas emitted from one system is a single component, but the system is frequently switched to other systems and other types of toxic gas components are emitted. be. In other words, in the past, it was necessary to install a corresponding number of treatment facilities according to the toxic gas components, and to select a treatment system according to the change of exhaust gas, but in the present invention, the above-mentioned The first step and the second step may be performed as they are. For example, in the case of a gas containing only silane as a toxic gas component, the gas only passes through the adsorption tower 6 in the first step without affecting the impregnated activated carbon, and the silane is removed in the second step. be done. As described above, the present invention is advantageous in terms of control and equipment cost, since it is not necessary to take measures every time the type of toxic gas component is switched to a different type.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one example of the method of the present invention, and FIG. 2 is a flow sheet showing another example of the method of the present invention. DESCRIPTION OF SYMBOLS 1...First process, 2...Second process, 3...Reactor, 4...Vacuum pump, 5...Filter, 6...
...Adsorption tower, 7...Pipe line, 8...Water tank, 9...Scrubber, 10...Aqueous solution, 11...Pump, 12
... Nozzle, 13 ... Blower, 14 ... Filler, 15, 16 ... Pipe line.

Claims (1)

[Claims] 1. When detoxifying gas containing toxic gas components such as silane, arsine, phosphine, and diborane, a first step is to remove toxic gas components other than silane from the gas by bringing the gas into contact with activated carbon impregnated with an adsorption enhancer. of a gas containing a toxic gas component, the method comprises carrying out one step, and then conducting a second step of introducing the gas derived from the first step into a silane treatment system to remove silane from the gas. Processing method.