JPH0312219A - Removal of toxic component - Google Patents

Abstract

PURPOSE:To remove ozone and silanes simultaneously and efficiently by using a removing agent comprised of soda lime and a cupric compound carried on the soda lime in removal of toxic components of ozone and silanes contained in a gas. CONSTITUTION:Soda lime is amorphous particle or granular condition and used preferably under water-retaining condition. As a cupric compound to be carried on the soda lime, cupric oxide, cupric hydroxide, basic cupric carbonate, etc., can be used and one or a mixture of more than one of them are used. The amount (as Cu) of the cupric compound to be carried on the soda lime is normally about 0.1-50% and preferably about 1-30%. The method to carry the compound can be selected either dry- or wet-method and in either case, sufficient effect as a removal agent is achieved. The removal agent is conventionally filled in a removal column and a gas containing toxic components such as ozone, silanes, etc., is led to the column and brought into contact with the removal agent so as to remove the toxic components. The temperature at the time of contacting the gas and the removal agent is normally <=100 deg.C.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for removing harmful components, and more particularly to a method for removing harmful components at the same time as ozone and silane contained in gases emitted from semiconductor manufacturing processes. Concerning a method for removing components.

Utilizing its oxidizing power, ozone is used in various ways in semiconductor manufacturing processes, etc., but recently it has been used to create silicon oxide by reacting with monosilane or disilane (hereinafter collectively referred to as silane) at relatively low temperatures. It is used in the film deposition process (CVD).

Ozone is ACG IH (American Conf
erence of Governmental Indu
0 at the permissible concentration of strial HyginisLs).
．． It is considered to be 1PP-, and 100p in the semiconductor manufacturing process.
Since ozone of about 5% pn+ is used, it is necessary to remove the gas before discharging it in order not to damage the environment.

On the other hand, silane has a wide flammability range and can spontaneously ignite in the air depending on the conditions, making it extremely dangerous.Also, the permissible concentration is set at 5 ppm, so this treatment is essential.

[Conventional technology]

Conventionally, methods for removing ozone include, for example, a method in which ozone-containing gas is decomposed and removed using fibrous activated carbon (Japanese Unexamined Patent Publication No. 49-82593), and a method in which a refractory inorganic oxide carrier contains a transition metal salt. A method using an ozone decomposition catalyst impregnated with a solution and fired (Japanese Patent Application Laid-Open No. 53-146
88 Publication) and the like are known.

On the other hand, as a method for treating gas containing silane,
A wet method in which silane is removed by washing the gas with an alkaline aqueous solution such as caustic soda (Japanese Unexamined Patent Publication No. 56-84619), and a solid carrier is impregnated with a caustic soda aqueous solution alone or an aqueous solution containing potassium permanganate. Dry method of removing gas by bringing it into contact with the absorbent (Japanese Patent Application Laid-open No. 58
-128146).

[Problem to be solved]

However, all of these methods treat ozone or silane alone, and do not simultaneously treat ozone and silane contained in exhaust gas.

[Means to solve the problem]

As a result of intensive research, the present inventors have applied a removing agent made by supporting a copper compound on soda lime as disclosed in Japanese Patent Application Laid-Open No. 152515/1987, which was previously filed as a method for removing silanes. They discovered that ozone can be efficiently removed at the same time as silane, and completed the present invention.

That is, the present invention provides a method for removing harmful components in which ozone and silane are removed by bringing a gas containing ozone and silane as harmful components into contact with a removing agent. This is a method for removing harmful components, which is characterized by using a chemical agent.

The present invention applies to gases containing ozone and silane, such as nitrogen, hydrogen, argon, helium and air.

The harmful components removed by the present invention are ozone and silanes, such as monosilanes, disilanes, and halogenated silanes.

The soda lime used in the present invention is generally called soda lime, and is described in the Rikagaku Encyclopedia (Iwanami Shoten, 1983).
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, as described in 1996, p. 761). Soda lime is also specified as a reagent in Japanese Industrial Standards K8603.

The chemical component of soda lime is mainly calcium hydroxide.
This substance 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 particles or granules, and water is liberated at 100 to 200°C, or remains in a water-retaining state in terms of ozone and silane removal ability. It is preferable to use

The grain size of soda lime is usually about 1.5 to 3.5 a+m for the commercially available No. 1 product, and about 3.5 m for the No. 2 product.
．． 5-5.5m+1.3 product is about 5.5-7.0mm, and any of these may be used.

In the present invention, the copper (n) compound supported on soda lime includes copper oxide, copper hydroxide, basic copper carbonate, etc., and the compound is one or a mixture of two or more of these.

As copper oxide, in addition to CuO, which is the original copper oxide, a group of compounds called CuO-nH2O, which is called hydrated copper oxide, are known, and all of them are effective.

Copper(II) compounds can be prepared by various conventionally known methods for each compound. Copper hydroxide prepared by the neutralization reaction of a copper(II) salt such as copper sulfate, copper nitrate, copper chloride or copper acetate with an alkali hydroxide, and copper hydroxide prepared by the neutralization reaction of a copper hydroxide with an alkali carbonate. or copper oxide obtained by calcining copper hydroxide or basic copper carbonate prepared in this way.

The amount of these copper (II) compounds supported on soda lime is usually 0.1 to 50%, preferably 1 to 30% as Cu. If the supported amount of copper is less than 0.1%, ozone removal becomes difficult and silane removal efficiency also decreases.

On the other hand, if the supported amount is greater than 50%, not only will the copper(II) compound be more likely to peel off, but when the concentration of silane is high, the temperature will rise due to heat generation, causing powdering and copper (II)
II) Reduction of the compound to metallic copper occurs, reducing the ability to remove both ozone and silane.

The amount of copper (II) compound supported on soda lime is Cu
If the amount is less than 5%, the copper(II) compound can be precipitated on the soda lime by impregnating the soda lime with a starting material such as copper sulfate, copper nitrate, copper chloride or copper acetate in the form of an aqueous solution. . However, rather than this method, it is preferable to support the compound obtained by neutralizing the acid group as described above while keeping it intact.

There are a dry method and a wet method as a supporting method, and either method can be used to obtain a sufficient effect as a removing agent. As a dry method, soda lime can be easily supported, for example, by sprinkling powder of a copper(II) compound such as copper oxide or basic copper carbonate. As a wet method, for example, IR (
[) There is a method of sprinkling a paste of the compound on soda lime, but since it is necessary to dry it while sprinkling it on soda lime, it is slightly disadvantageous from an industrial perspective compared to the dry method.

In the present invention, since the main components of the removing agent are calcium hydroxide and copper (II) compounds in soda lime, it does not have deliquescent properties like caustic alkali, and even when filled in the removing cylinder, it does not cause re-precipitation. The filling cylinder does not become clogged and can withstand long-term use.

Furthermore, if the gas contains hydride gases such as arsine, phosphine, hydrogen selenide, and diborane in addition to ozone and silane, there is also the advantage that these can also be removed at the same time.

In the present invention, the removal agent is usually filled in a removal cylinder, and the harmful components in the residue are removed by flowing a gas containing harmful components through the cylinder and bringing it into contact with the removal agent.

There is no particular restriction on the flow rate of the gas, but for example, when the combined concentration of ozone and silane is 10 to 100%, the linear velocity (LV) of the gas is usually 10 cm/sec or less,
Preferably it is 1 cm/sec or less, and the concentration is 1 cm/sec or less.
When it is less than 0%, the linear velocity (LV) is 200 cm.
/sec or less is preferable. Note that both ozone and silane create an explosive mixture, so these areas must be avoided.

The gas to be treated in the present invention is usually in a dry state, but even if it is in a wet state, it is sufficient that it is not so wet as to cause dew condensation within the removal cylinder.

The contact temperature between the gas and the removal agent is usually 100°C or less. If the temperature is higher than this, the removal ability may decrease due to the dissipation of the water constantly contained in soda lime. Usually, the room temperature is 60°C or less, and there is no need for particular heating or cooling.

Moreover, the pressure during treatment may be normal pressure, reduced pressure, or increased pressure, and is 20 kg/crd abs for boat fishing, preferably 0.001 to 10 kg/co! ABS range.

〔Effect of the invention〕

The purification method of the present invention can simultaneously and efficiently remove ozone and silane contained as harmful components in exhaust gas discharged from semiconductor manufacturing processes and the like.

Furthermore, since it is a dry method and the device is basically just a removal tube filled with a removal agent, it is compact and can be easily installed in narrow spaces.

〔Example〕

Example 1 Aqueous solutions of copper sulfate and sodium hydroxide were mixed to form a precipitate of hydroxide steel. Wash this precipitate with water for 3
After repeating the process several times, it was dried at 150°C for 5 hours, and then dried at 300°C.
Copper oxide (Cub) was obtained by firing at °C for 10 hours. A removing agent was prepared by sprinkling this copper oxide on commercially available No. 1 soda lime to support it at 8 wt%.

As shown in Figure 1, inner diameter 19+u+φ, length 300I
In a IIIll quartz cylinder 1, from the bottom, ozone detection agent 2 containing indigo as a discoloration component (lower detection limit 0.lppm)
>1 c @ (filling amount 2.8 d, 2 g), remover 3 at 5
cm (14 ctn, 13 g), 1 cm of detecting agent 4, 5 ctn of removing agent 5, and 1 cm of detecting agent 6 were sequentially stacked and filled to form a removal cylinder 7.

Oxygen containing 0.5% ozone was placed in the removal tube 7 at room temperature (2
850m/mia (LV 5cm) at 0°C
/sec) from top to bottom and the time taken for the detection agent 2 to change color was measured and was 3100 minutes.

When converted into ozone treatment capacity, this is 465,171 removers.

Subsequently, a detector (TO-4000, manufactured by Bionics ■) with a monosilane measurement range of 0 to 15 PPIll was attached to the outlet of this removal cylinder 7, and argon containing 0.5% monosilane was heated at room temperature (20°C). 850 rnQ/r
rm (LV 5 cm/sec) and the time required for the concentration of monosilane to reach 5 ppm was measured and was 110 minutes. This is converted into monosilane processing capacity of 16.5 ffl/1 removal agent.

Example 2 Argon containing 0.5% monosilane was poured into the removal cylinder 7 similar to that used in Example 1 for 850 m at room temperature (30°C).
The time taken for the monosilane concentration to reach 5 ppm by flowing at a flow rate of LV 5 cm/sec was 110 minutes. Converting this into monosilane processing capacity, it is 16.5 ρ/g removal.

Subsequently, oxygen containing 0.5% ozone was added to this removal cylinder 7 at room temperature (20°C) at a rate of 850 m/ml (L V5
The time taken for the detection agent 2 to change color after flowing at a rate of 3000 minutes (cm/see) was measured and was 3000 minutes.

When converted into ozone treatment capacity, this is 450,171 removers.

Example 3 Argon (including oxygen) containing 0.1% monosilane and 0.01% ozone was placed in the same removal cylinder 7 as used in Example 1 at room temperature (20°C) at 850 m/tm ( L
When the time taken for the concentration of monosilane to reach 5ρp and the time taken for the detection agent 2 to change color was measured by flowing the solution at There was no discoloration of the detecting agent at this point, and breakthrough did not occur.

Comparative Example 1 Instead of the removing agent used in the example, only No. 1 soda lime was filled, and oxygen containing 0.5% ozone was reduced by 850/111iII (LV 5) at room temperature (20°C).
The time taken for the detection agent 2 to change color after flowing at a flow rate of 1 minute and 37 seconds was measured. Converting this to ozone processing capacity is 0.21. ,/becomes a ρ remover.

Comparative Example 2 Manganese nitrate [Mn(NO3)2.6HzO17,26
g was dissolved in 20 mQ of water, 40 g of commercially available granular alumina was mixed with this aqueous solution, stirred well, and then dried at 100° C. for 1 hour. Put this thing in an electric furnace and put it in the air for 65 minutes.
The mixture was heated and baked at ℃ for 5 hours to obtain a removing agent.

This removing agent was filled into cylinder 1 in the same manner as in the example, and 0.
Argon containing 5% monosilane at room temperature (20°C)
850-/m (LV 5cm/sec)
When the time required for the detection agent 2 to change color was measured, it instantly reached 5 ppm. There was no ability to process monosilane at all.

Comparative Example 3 A removal test was conducted in the same manner as in the example using activated carbon as a removal agent.

85 argon containing 0.5% monosilane at room temperature.
0d/ym (LV5cn/see), and the time taken for monosilane in the outlet gas to reach 5ρPI11 was measured, and it was 20 minutes. Monosilane has a processing capacity of 3 as a silt removal agent. Moreover, the remover started to burn soon after being taken out into the air.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the removal cylinder. The numbers in the drawings are as follows. 1. Cylinder 2.4 and 6. Detection agent 3 and 4. Remover 7. removal tube

Claims (1)

[Claims] In a method for removing ozone and silane by bringing a gas containing ozone and silane as harmful components into contact with a removing agent, a removing agent made by supporting a copper (II) compound on soda lime is used. Features a method for removing harmful components.