JPH0561966B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for removing silanes, and more particularly to a method for removing silanes contained in gases discharged from semiconductor manufacturing processes.

In recent years, with the development of the semiconductor industry, the amount of silanes used has increased significantly. Silanes are used in the production of crystalline silicon, amorphous silicon, silicon nitride, and silicon carbide, as well as in the production of silicon oxide films.

Typical silanes include monosilane and disilane.

Silanes have a wide flammable range and can spontaneously ignite in the air under certain conditions, making them extremely dangerous and harmful to humans if inhaled, so they must be removed before being released into the atmosphere.

[Problems to be solved by conventional technology and invention]

Conventionally, in order to treat exhaust gas containing silanes, there has been a method of wet removal by washing with an alkaline aqueous solution such as caustic soda, as shown in, for example, JP-A-56-84619 and JP-A-57-94323. has been adopted. However, wet processing is inconvenient because the equipment becomes large and handling of the alkaline aqueous solution is dangerous.

On the other hand, as shown in JP-A-58-1281468, a dry absorption treatment agent has been proposed in which a solid carrier is impregnated with an aqueous solution of caustic soda alone or with an aqueous solution of an oxidizing agent such as potassium permanganate. ing. When this treatment agent is used, it has the advantage of being able to downsize the equipment because it is a semi-dry process.
As caustic soda and potassium permanganate repeatedly precipitate on the surface of the carrier and deliquesce, the pressure loss in the filling cylinder increases, and in some cases, problems such as blockage occur, causing problems such as damage to semiconductors. Disadvantages include that the entire manufacturing process may need to be stopped. Also, related to this phenomenon, gas tends to channel, and in some cases, the removal ability is less than the data measured under ideal conditions.

[Means for solving problems]

In order to improve the shortcomings of these conventional techniques, the present inventors conducted intensive studies on methods for removing silanes contained in exhaust gas, etc., and found that silanes were added to a removal agent made by supporting copper () compounds on soda lime. They have discovered that silanes can be efficiently removed by bringing them into contact with each other, and have completed the present invention.

That is, the present invention provides a method for removing silanes in which a gas containing silanes as a harmful component is brought into contact with a removing agent. This is a method for removing silanes characterized by using the method.

The present invention is applied to mixed gases of nitrogen, hydrogen, argon, helium, air, etc., and silanes.

The silanes removed by the present invention are mainly monosilane and disilane, but it is also effective in removing halogenated silanes.

The soda lime used in the present invention is usually called soda lime, and as described in the Physical and Chemical Dictionary (Iwanami Shoten 1983, p. 761),
It is a strongly basic, white, granular solid substance that is usually made by soaking quicklime in a concentrated solution of sodium hydroxide and heating it. Soda lime is also specified as a reagent in Japanese Industrial Standard K8603. The chemical component of soda lime is mainly calcium hydroxide, which also contains a small amount of sodium hydroxide, and is also sold commercially under the name soda lime.

These commercially available soda limes are in the form of irregularly shaped granules or granules, and the moisture released at 100 to 200℃ is reduced to 19%.
Contains less than %. In the present invention, this water may be used after being evaporated, but from the viewpoint of the purifying ability of the silanes, it is preferable to keep the water as it is.

The particle size of soda lime is usually about 1.5 to 3.5 mm for commercially available No. 1 products, about 3.5 to 5.5 mm for No. 2 products, about 5.5 to 7.0 mm for No. 3 products, and for elemental analysis. The diameter is approximately 1.5 to 2.5 mm, and any of these may be used.

In the present invention, the copper() compound supported on soda lime includes copper oxide, copper hydroxide, basic copper carbonate, etc., and these compounds are one type or a mixture of two or more types. As copper oxide, CuO, which is the original copper oxide, and a compound group called CuO·nH ₂ O, which is called hydrated copper oxide, are known, and both of these are effective.

The amount of these copper () compounds supported as Cu relative to soda lime is usually 0.1% to 50%, preferably 1% to 30%. The amount of copper supported is
When the amount is less than 0.1%, the ability of the remover is not much different from that of soda lime, and it is physically difficult to support more than 50%, and the removal of the copper() compound from the soda lime is difficult. Not only is this easy to occur, but when the concentration of silanes in the gas is high, the temperature rises due to heat generation, causing powdering and reduction of the copper() compound to metallic copper, reducing the ability of the removal agent.

The copper() compounds used in the present invention can be prepared by various conventionally known methods for each compound.

For example, copper hydroxide prepared by the neutralization reaction of a copper salt such as copper sulfate, copper nitrate, copper chloride or copper acetate with an alkali hydroxide, and the neutralization reaction of a copper hydroxide with an alkali carbonate. These include basic copper carbonate prepared in this manner, and copper oxide prepared by calcining copper hydroxide or basic copper carbonate thus prepared.

If the amount of copper () compound supported is limited to 5% or less as Cu in soda lime, soda lime is impregnated with starting materials such as copper sulfate, copper nitrate, copper chloride, or copper acetate in the form of an aqueous solution. It is possible to precipitate the copper() compound mentioned above in the form of soda lime. However, rather than this method, it is preferable to separately synthesize a compound obtained by neutralizing acid groups as described above and then support the compound.

A dry method and a wet method are possible for supporting a copper() compound on soda lime, and both are effective, but the dry method is somewhat advantageous from an industrial perspective.
As an example of a dry method, powder of a copper compound such as copper oxide or basic copper carbonate can be easily supported by sprinkling it on soda lime. An example of a wet method is a method in which soda lime is sprinkled with a paste of a copper compound. This wet method has disadvantages from an industrial perspective, since it is necessary to dry the copper() compound while sprinkling it on soda lime, but it is as effective as the dry method in terms of removing silanes.

In the present invention, the removing agent made by supporting a copper() compound on soda lime is different from conventionally proposed silane removers because its main components are calcium hydroxide from soda lime and a copper() compound, so it does not have deliquescent properties. Moreover, there is no fear of clogging of the filling cylinder due to redeposition, etc., and it can withstand use for a long period of time. It also has a greater removal ability than conventionally proposed removers, and is advantageous in this respect as well.

Furthermore, when the gas to be treated contains hydride gases such as arsine, phosphine, diborane, and hydrogen selenide in addition to silanes, there is an advantage that these can also be removed together with the silanes.

In the present invention, a removing agent made of soda lime supporting a copper (2) compound is packed into a removing cylinder and used as a fixed bed. The gas containing silanes is flowed into the removal agent cylinder and brought into contact with the removal agent, thereby removing harmful components such as silanes and purifying the gas to be treated.

Although there are no restrictions on the concentration of silanes contained in the gas to be treated and the gas flow rate to which the removal method of the present invention is applied, it is generally preferable to decrease the flow rate as the concentration increases.

For example, regarding monosilane, its concentration is 10~
When it is 100%, the cylinder linear velocity of the gas to be treated is usually 10 cm/sec or less, preferably 1 cm/sec or less. Further, when the concentration is less than 10%, it is preferable that the linear velocity of the blank tube is 200 cm/sec or less.

The gases to be treated to which the removal method of the present invention can be applied are:
Usually it is in a dry state, but even if it is in a wet state, it is fine as long as it is not so wet that dew condenses inside the removal cylinder.

The contact temperature between the gas to be treated and the removal agent is preferably 100°C or higher. If the temperature is higher than this, the water content in the soda lime may become extremely low and the ability to remove silanes may decrease. Normally, room temperature or room temperature is sufficient, and there is no need for particular heating or cooling.

The pressure of the gas to be treated may be normal pressure, reduced pressure, or increased pressure, but is usually 20 kg/cm ² abs or less, preferably in the range of 0.001 to 10 kg/cm ² abs.

[Effects of the Invention] According to the removal method of the present invention, harmful components such as silanes can be efficiently removed from gases containing harmful components such as silanes discharged from semiconductor manufacturing processes in a dry state and at low temperatures.

Example 1 Aqueous solutions of copper sulfate and sodium hydroxide were mixed to form a precipitate of copper hydroxide. Next, it was thoroughly washed, dried, and then fired to prepare copper oxide. This copper oxide was sprinkled on commercially available No. 1 soda lime to make it carry 8% of the copper oxide.

A cylindrical quartz reactor 10 with an inner diameter of 19φ and a length of 400 mm as shown in Fig.
10ppm) was filled to 1 cm (8.5 ml, about 8 g), and then the copper oxide-supported soda lime prepared above was filled to a filling length of 10 cm (85 ml, about 78 g), and then the detection agent and removal agent were added in the same way. These steps were alternately repeated three times and filled, and finally, 1 cm of the detection agent was filled. Hydrogen gas containing 4.5% monosilane was supplied from the top of reactor 10 at room temperature at 170 ml/min (cavity linear velocity 1
The time required for the detection agent 6 shown in FIG. 1 to change color after flowing at a rate of 345 minutes (cm/sec) was 345 minutes. This corresponds to a monosilane treatment capacity of 31/removal agent.

Example 2 Aqueous solutions of copper sulfate and sodium carbonate were mixed to form a basic copper carbonate precipitate. Next, it was thoroughly washed and dried to prepare basic copper carbonate powder. This basic copper carbonate was sprinkled on commercially available soda lime to obtain a 15% loading.

The same reactor 10 as in Example 1 was filled in exactly the same manner as in Example 1, except that the basic copper carbonate-supported soda lime prepared here was filled in place of the copper oxide-supported soda lime of Example 1.

Nitrogen gas containing 4.5% monosilane was passed from the top of the reactor 10 at room temperature at 170 ml/min (empty linear velocity 1 cm/sec), and the time taken for the detection agent 6 in Fig. 1 to change color was measured, and the result was 345. It was hot in minutes. This means that the processing capacity of monosilane is 31/
Corresponds to an adsorbent.

Example 3 Aqueous solutions of copper sulfate and sodium hydroxide were mixed to form a copper hydroxide precipitate. Then, after thorough washing, dried hydrated copper oxide was produced. This hydrated copper oxide was sprinkled on commercially available No. 1 soda lime to achieve a 15% loading.

Instead of copper oxide-supported soda lime in Example 1,
Filling was carried out in exactly the same manner as in Example 2, except that the soda lime supporting hydrated copper oxide prepared here was filled.

Detecting agent 6 in FIG.
The time it took for the color to change was measured and was 285 minutes. This corresponds to a monosilane treatment capacity of 29/adsorbent.

Comparative Example 1 1 in place of the copper oxide-supported soda lime of Example 1
Filling was carried out in the same manner as in Example 1, except that No. 1 soda lime was used.

Detecting agent 6 in FIG.
The time it took for the color to change was measured and was 175 minutes. This corresponds to a monosilane treatment capacity of 17/soda lime.

[Brief explanation of drawings]

FIG. 1 is a side view of a reactor filled with removal agent and detection agent. In the figure, 1, 2, 3 and 4...removal agent,
5, 6, 7, 8 and 9...detecting agent, and 1
0...Reactor.

Claims (1)

[Claims] 1. A method for removing silanes in which a removal agent is brought into contact with a gas containing silanes as a harmful component, the method comprising using a removal agent made by supporting a copper() compound on soda lime. .