JPH06154535A - Method for purifying harmful gas - Google Patents

Abstract

PURPOSE:To make harmless a harmful gas of hydride such as arsine, phospine, silane, diborane and hydrogen selenide which are discharged from a semiconductor manufacturing line, by using a purifying agent of a composition of manganese dioxide, copper oxide and a silver compound as main components incorporated with potassium. CONSTITUTION:A purifying agent is composed of a composition of manganese dioxide and copper oxide as main components containing a potassium component with an addition of silver compound. The combined total content of manganese dioxide and copper oxide is 50wt.% min and the content of potassium as K2O is 2.5 to 15wt.%. The addition amount of silver compound is 0.01 to 10.0% for the total amount of the purifying agent. In addition, the concentration of a hydride gas contained in the gas is 10vol.% max. Further, time required for the contact between the gas and the purifying agent is 0.6sec. min, and the contact temperature is 100 deg.C max. The purifying agent is capable of treating a harmful gas safely without abnormal generation of heat due to a reduction reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying harmful gases, and more particularly, CVD in semiconductor manufacturing processes,
The present invention relates to a method for purifying a harmful gas, which is used for ion implantation or the like, for efficiently purifying a harmful gas containing a hydride gas before it is discharged from the system. In recent years, with the development of the semiconductor industry, the amount of highly toxic hydride-based gases such as arsine, phosphine, silane, diborane and hydrogen selenide used has been increasing. These harmful gases are indispensable as a raw material gas or a doping gas in the manufacturing process of silicon semiconductors and compound semiconductors, but all have extremely high toxicity, and the permissible concentration of each is 0.05 ppm in arsine (AsH ₃ ), Phosphine (PH ₃ ) 0.3ppm, Silane (SiH ₄ ) 5p
pm, diborane (B ₂ H ₆ ) is 0.1 ppm, and hydrogen selenide (SeH ₂ ) is 0.05 ppm. When these harmful gases are emitted from the semiconductor manufacturing line,
There is a strong demand for safety measures to prevent polluting the environment.

[0002]

2. Description of the Related Art A gas mask filled with activated carbon is known in chemical warfare to remove harmful gases such as arsine and phosphine, and various substances are impregnated on the activated carbon by utilizing the adsorption power of the activated carbon. Attempts have also been made to improve the removal capacity. For example, JP-A-60-71
Japanese Patent No. 040 discloses an adsorbent obtained by impregnating activated carbon with iodine or an iodine compound and a metal sulfate.
Further, the applicant of the present application has previously proposed a method of using a purifying agent in which a silver compound is impregnated in a composition containing manganese dioxide and copper oxide as main components (JP-A-1-254230).

[0003]

However, although adsorbents such as activated carbon can remove harmful gases such as arsine and phosphine at relatively low concentrations, they are harmful to gases in high concentrations and at high flow rates. There is a problem that the activity is too low for gas and iodine reduced by these hydride-based gases is easily scattered. Further, the purifying agent impregnated with manganese dioxide, copper oxide and a silver compound has a large capacity and can remove a high concentration of hydride gas, but since the activity is high, the temperature of the removing agent is conditioned by the heat generated by the reaction heat. Depending on the temperature, the temperature rises by 10 to 20 ° C. In particular,
When the base gas contains hydrogen, heat is easily generated due to the reduction reaction even at a low temperature of 40 ° C or lower, the temperature rises rapidly depending on the conditions, reaches a high temperature of 200 ° C or higher, and cooling equipment is required. Not only that, but it was also found that there was a problem that the purification capacity was significantly reduced.

[0004]

As a result of intensive studies to solve these problems, the present inventors have found that a gas containing a hydride gas such as arsine, phosphine, silane, diborane and hydrogen selenide as a harmful gas. By using a purifying agent containing an appropriate amount of potassium component in a composition containing manganese dioxide, copper oxide, and a silver compound as the main components, abnormal heat generation due to the reducing reaction of the purifying agent can be performed even for gas containing hydrogen. The present invention has been accomplished by finding out that there is no problem, it is safe, and that a high concentration of harmful components can be removed very efficiently. That is, in the present invention, a gas containing a hydride gas, which is a harmful component, is contacted with a purifying agent obtained by impregnating a composition containing manganese dioxide and copper oxide as main components and a potassium component with a silver compound. Is a method for purifying harmful gas.

The present invention removes hydride gases such as arsine, phosphine, silane, diborane and hydrogen selenide contained in exhaust gases such as hydrogen, nitrogen, argon and helium discharged from a semiconductor manufacturing process, and particularly to a relatively high concentration. It is applied to the rapid removal of hydride gas from harmful gas containing high reducing gas such as hydrogen.

In the present invention, the total content of manganese dioxide and copper oxide is usually 50% by weight or more, preferably 70% by weight or more. The weight ratio of copper oxide to manganese dioxide is usually 1: 0.2.
-1.2, preferably about 1: 0.3-0.8.
The mixture of manganese dioxide and copper oxide can be obtained by mixing the respective components. In addition, these mixtures are commercially available as hopcalite, so that they can be easily obtained. For example, as the hopcalite, a binary element system containing 60% by weight of manganese dioxide and 40% by weight of copper oxide is mainly commercially available. These are manganese-
Some copper contains a small amount of magnesium, aluminum, silicon, potassium, etc. mainly as an oxide.
However, the content of these potassium components is K ₂ O.
Is usually 2.0% by weight or less, and this content is difficult to control in the manufacturing process, so that the change is not large and constant.

In the present invention, the form of potassium which is one component of the purifying agent is not particularly limited, and may be any of metal, oxide, hydroxide and salt, such as potassium oxide, potassium hydroxide, potassium chloride, Examples include potassium carbonate. Of these, in general, it is preferable that they are contained in the form of oxide (K ₂ O). The content of potassium is K
_{The amount of 2} O is usually about 2.5 to 15% by weight, preferably 3.5 to 10% by weight. When it is less than 2.5%, especially in the case of a gas containing hydrogen, heat generation due to the reduction reaction becomes remarkable, while when it is more than 15% by weight, the ability to remove hydride gas is lowered.

In the present invention, a composition containing manganese dioxide and copper oxide containing a potassium component (hereinafter referred to as Mn-Cu).
A purifying agent obtained by impregnating a silver compound with (-K composition) is used. Examples of the silver compound include silver (I) oxide, silver (II) oxide, and silver salts (I) such as inorganic acid silver, organic acid silver and silver halide. Examples of the inorganic acid silver include silver carbonate, silver nitrate, silver nitrite, silver sulfate, silver sulfite, silver chlorate, silver perchlorate, silver bromate, silver iodate, silver periodate, disilver hydrogen phosphate, silver phosphate. , Silver pyrophosphate, silver metaphosphate, silver tetrafluoroborate, silver hexafluorophosphate, etc., as the silver halide, for example, silver fluoride, silver chloride, silver bromide, silver iodide, and as the organic acid silver, for example, silver acetate. , Silver oxalate, etc. Of these, silver (II) oxide, silver (I) carbonate, silver (I) oxide and mixtures thereof are preferable.

As the Mn-Cu-K composition to which the silver compound is attached, various shapes such as a crushed product, an extrusion molded product and a tablet molding can be used. The size is about 4 to 20 mesh for a crushed product, about 1.5 to 4 mmφ × 3 to 20 mm for an extruded product, and usually 3 to 6 mmφ × 3 to 6 mm for a tablet molding product. The size of is preferable. However, there are no problems with other dimensions depending on the design conditions of the device. Various methods can be used for attaching the silver compound to the Mn-Cu-K composition, and a wet method or a dry method may be used. As a simple method, there is a method of sprinkling a powdery silver compound on the Mn-Cu-K composition or a method of impregnating the silver compound as an aqueous slurry. The amount of the silver compound to be attached is usually 0.01 to 10.0% by weight as Ag based on the total amount of the cleaning agent, and preferably 0.1.
It is set to 2 to 5% by weight. If it is less than 0.01% by weight, the purifying ability is lowered, and if it is more than 10.0% by weight, the economical burden becomes large. Usually 7 to 3 for purifying agents
Moisture of about 0% by weight is contained, and these change according to the relative humidity in the air and the like, but do not particularly affect the purification performance of harmful gas.

In the present invention, the concentration of the hydride gas contained in the gas varies depending on its type, gas flow rate and the like and cannot be specified unconditionally, but it is usually 10 vol% or less, preferably 1 vol% or less. If the concentration is higher than this, the heat of reaction becomes large and a cooling device may be required.
The contact time between the gas and the purifying agent is usually 0.6 seconds or longer, preferably 3.0 seconds or longer, and these are appropriately designed in relation to the concentration of the hydride gas. The contact between the purifying agent and the gas is generally 100 ° C. or less, but it is usually operated at room temperature of about 10 ° C. to 50 ° C., and heating or cooling is not particularly required. However, after the contact is started, the temperature rises according to the concentration of reducing gas such as hydrogen or hydride gas depending on the conditions. The pressure at the time of contacting is often around normal pressure, but it is also possible to operate under reduced pressure or under increased pressure such as 1 kg / cm ² G.

In the present invention, the purifying agent is usually packed in a column for purifying harmful gas and used as a fixed bed, but it can also be used as a moving bed or a fluidized bed. When the purifying agent is filled in the purifying cylinder or the like, the packing density is usually 0.4 to 1.
The amount is about 2 g / ml, preferably about 0.5 to 1.0 g / ml. The filling length of the purifying agent varies depending on the flow rate of gas and the concentration of harmful gas, etc., but is usually 50 to 5 in practice.
The inner diameter of the purifying cylinder is set to about 100 mm and the empty cylinder linear velocity (LV) of the gas flowing in the cylinder is set to about 10 cm / sec or less. Generally, these are determined by the pressure loss of the packed bed, the contact efficiency with air and the amount of harmful gas.

[0012]

【Example】

Examples 1 to 4 (Preparation of Purifying Agent) Manganese dioxide 50% by weight, copper oxide (CuO) 22% by weight, magnesium oxide (MgO) 12.5% by weight, aluminum oxide 1 as main materials of the cleaning agent
2.5% by weight, 2% by weight potassium oxide (K ₂ O),
Commercially available Hopcalite, which is an extrusion molded product of 1.5 mmφ × 3 to 10 mm, was used. This Hopcalite 1000
A 50% aqueous solution of potassium hydroxide was sprinkled and impregnated on g, 10 g of silver (II) oxide was added in a poly container, and the mixture was attached while rotating on a ball mill stand. 80 ° C
It is dried for 4 hours, and potassium is changed to K ₂ O to 3.5-
Various purifying agents were prepared containing in the range of 10% by weight. (Measurement of reduction initiation temperature) For each of the obtained purifying agents, 740 ml was filled in a filling cylinder having an inner diameter of 56 mmφ, a thermocouple was attached to the outer wall, a heater was wound from above, and the inside of the purification cylinder was replaced with nitrogen. , Hydrogen gas 1.5L /
The temperature was gradually increased by gradually heating from room temperature (20 ° C.) while circulating at min (LV = 1 cm / sec), and a point where a remarkable temperature rise due to heat generation was observed, that is, the reduction initiation temperature was examined.

(Measurement of Purifying Ability) Next, each new purifying agent is newly added to a purification cylinder having an inner diameter of 40 mmφ.
The removal test of phosphine in hydrogen was carried out by filling up with ml. The concentration of phosphine in the outlet gas was measured using a cold atomic absorption method while flowing hydrogen gas containing 1 vol% of phosphine at 0.75 L / min (LV = 1 cm / min) at room temperature of 20 ° C., and phosphine was detected (28 ppb ) Was measured (effective treatment time). The results are shown in Table 1.

Comparative Example 1 Using a purifying agent prepared in the same manner as in Example except that the aqueous potassium hydroxide solution was not impregnated, the reduction initiation temperature and effective treatment time were measured in the same manner. However, the reduction initiation temperature was low, and the temperature exceeded 100 ° C. due to heat generation during the measurement of the effective treatment time, and a further rapid increase was observed, so the test was stopped. The results are shown in Table 1.

[0015]

Table 1 K ₂ O content Reduction start temperature Effective treatment time Weight% ℃ min Example 1 3.5 55 675 Example 2 5.0 5.0 68 682 Example 3 7.0 95 655 Example 4 10. 0 111 588 Comparative Example 1 2.0 28 25

Examples 5 to 8 (Purifying agent) Purifying agents similar to those in Examples 1 to 4 were prepared. (Measurement of Purifying Ability) Using these purifying agents, the arsine removing ability of hydrogen containing arsine instead of phosphine was measured. Arsine 1 vo at room temperature 20 ° C
0.75 L / min of hydrogen gas containing 1% (LV = 1c
m / min), the concentration of arsine in the outlet gas was measured by the cold atomic absorption method, and arsine was detected (25 pp
The time (b) was measured (effective treatment time). The results are shown in Table 2.

Comparative Example 2 Using the purifying agent prepared in the same manner as in Examples 5 to 8 except that the aqueous potassium hydroxide solution was not impregnated, the effective treatment time was similarly measured for hydrogen gas containing arsine. . However, the temperature is 100 due to the heat generation.
The test was discontinued because the temperature exceeded ℃ and a sharp rise was observed. The results are shown in Table 2.

[0018]

Table 2 K ₂ O content Effective treatment time Weight% min Example 1 3.5 880 Example 2 5.0 894 Example 3 7.0 855 Example 4 10.0 752 Comparative Example 1 2. 0 45

Examples 9 to 11 (Purifying agent) A purifying agent containing 7.0% by weight of K ₂ O similar to that in Example 3 was prepared. (Measurement of Purifying Ability) 126 ml of this purifying agent was filled in a purifying cylinder having an inner diameter of 40 mmφ, and the removing ability of silane, hydrogen selenide or hydrogen containing diborane was measured. At room temperature of 20 ° C., hydrogen containing 1 vol% of the above hydride gas was 0.75 L / min (LV = 1 cm / m).
in), the hydride gas in the outlet gas was measured, and the time (effective treatment time) until each hydride gas was detected was determined. Analysis of each hydride gas was carried out by the diaphragm electrode method using silane (detection lower limit 5 ppm) and diborane (0.1 ppm), and for hydrogen selenide, using a detection tube (1 ppm, manufactured by Komei Rikagaku Co., Ltd.). It was The results are shown in Table 3.

[0020]

Table 3 Table 3 Kind of effective treatment time of hydride gas min Example 9 Silane 401 Example 10 Hydrogen selenide 772 Example 11 Diborane 413

[0021]

INDUSTRIAL APPLICABILITY According to the present invention, as a harmful gas contained in a gas, a large amount of a relatively high concentration hydride gas such as arsine, phosphine, silane, diborane and hydrogen selenide is efficiently and It can be removed very quickly. Moreover, abnormal heat generation due to the reduction reaction does not occur, and the harmful gas from the semiconductor manufacturing apparatus can be safely treated.

Claims (7)

[Claims] 1. A gas containing a hydride gas, which is a harmful component, containing manganese dioxide and copper oxide as main components, and
A method for purifying harmful gas, which comprises bringing a composition containing a potassium component into contact with a purifying agent obtained by impregnating a silver compound. 2. The purifying method according to claim 1, wherein the total amount of manganese dioxide and copper oxide in the purifying agent is 50% by weight or more. 3. The purifying method according to claim 1, wherein the potassium component in the purifying agent is potassium oxide, and the content thereof is _2.5 to 15% by weight as K ₂ O. 4. The purification method according to claim 1, wherein the amount of the silver compound impregnated in the purification agent is 0.01 to 10% by weight as Ag. 5. The purification method according to claim 1, wherein the harmful gas is a hydrogen-based gas or a gas containing hydrogen. 6. The purification method according to claim 1, wherein the hydride gas is one or more selected from arsine, phosphine, silane, diborane and hydrogen selenide. 7. The purifying method according to claim 1, wherein the contact temperature between the gas containing a hydride gas and the purifying agent is 100 ° C. or lower.