JPH0457368B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for purifying exhaust gas, and more particularly to a method for purifying gas containing toxic components discharged from semiconductor manufacturing processes. In recent years, with the development of the semiconductor industry and the optoelectronics industry, the amount of highly toxic hydrides used such as arsine, phosphine, ciborane, and hydrogen selenide has increased. These toxic components are essential substances as raw materials or doping gases in silicon semiconductor and compound semiconductor manufacturing industries, optical fiber manufacturing industries, and the like. Exhaust gas discharged from semiconductor manufacturing processes or optical fiber manufacturing processes often contains unreacted toxic components. Since each of these components is extremely harmful to living organisms, it is necessary to remove them before the gas is discharged in order not to damage the environment. [Prior art and problems to be solved] Methods for removing these toxic components include a wet method in which they are absorbed and decomposed using a scrubber, and a wet method in which exhaust gas is passed through a cylinder filled with a purifying agent such as an adsorbent or oxidizing agent. There are known methods for removing it. In general, the wet method has the drawback that maintenance of the equipment is expensive due to corrosion caused by the absorbing liquid and difficulty in post-treatment. In addition, as a method of using a purifying agent, nitrates such as silver nitrate are supported on a porous carrier,
Alternatively, a porous carrier impregnated with a metal chloride such as iron dioxide is used as an adsorbent to oxidatively remove phosphine and arsine (Japanese Patent Application Laid-open No.
56-89837) is known. However, although this method solves the various drawbacks of the wet method, it requires pre-wetting treatment of the exhaust gas from the CVD (chemical vapor deposition) process, etc.
This has the disadvantage that the device becomes complicated. Furthermore, a method of treating arsine, phosphine, etc. using three types of adsorbents in which inorganic silicate is impregnated with an aqueous alkali solution, an aqueous oxidizing agent solution, or an aqueous solution of an alkali and an oxidizing agent (Japanese Patent Publication No. 59-198-1)
49822) has also been proposed. Like the above-mentioned method, this method is also a process in a wet state and has the same drawbacks as the wet method. [Means and effects for solving the problem] As a result of intensive research to compensate for the shortcomings of these conventional techniques, the present inventors have developed a method that combines cupric oxide with oxides such as silicon, aluminum, and zinc oxide. They discovered that when the obtained purifying agent was brought into contact with exhaust gas containing toxic components, these toxic components could be efficiently removed, and after further research, they completed the present invention. That is, the present invention provides (1) a method for purifying exhaust gas that removes toxic components from a gas containing one or more of arsine, phosphine, ciborane, and hydrogen selenide as toxic components; A method for purifying exhaust gas, which comprises bringing the exhaust gas into contact with a purifying agent containing respective oxides of copper and (b) silicon and/or aluminum, and
(2) In an exhaust gas purification method for removing toxic components from a gas containing diborane and/or hydrogen selenide as toxic components, the gas is brought into contact with a purification agent containing cupric oxide and zinc oxide. This is a unique method for purifying exhaust gas. Since the purifying agent used in the present invention can remove toxic components from completely dried gas without any problem, there is no need for wetting treatment, which is a great advantage. The present invention applies to gases containing nitrogen gas, hydrogen gas or air, and one or more hydrides such as arsine, phosphine, diborane and hydrogen selenide. The purifying agent used in the present invention includes (a) cupric oxide and
(b) A composition containing at least one of silicon oxide and aluminum oxide. Furthermore, a composition containing cupric oxide and zinc oxide can also be used as a purifying agent for purifying diborane and hydrogen selenide. There is no particular restriction on the blending ratio of silicon oxide, aluminum oxide or zinc oxide to cupric oxide, but the atomic ratio of each metal is M/(M+Cu).
Usually 0.03~0.55, preferably 0.045~
It is 0.35. In the formula, Cu indicates the number of atoms of copper, and M indicates the number of atoms of silicon, aluminum, or zinc (when two or more of these components are used, the total number of atoms). Various methods can be applied to prepare the purifying agent. For example, hydroxides and oxides obtained by adding alkalis such as caustic soda, caustic potash, sodium carbonate, sodium bicarbonate, and ammonia to nitrates, sulfates, chlorides, and organic acid salts of copper, zinc, and aluminum, respectively. Precipitates such as intermediates are calcined to form oxides, which are used as purifying agents. Alternatively, for example, silica sol as silicon oxide, alumina sol as aluminum oxide, etc. may be mixed with cupric oxide powder, kneaded in a kneader, and dried to form a purifying agent. These oxides include copper hydroxide, zinc hydroxide, aluminum hydroxide, hydrated copper oxide (e.g. 4CuO・H ₂ O), or basic copper carbonate [Cu
(OH) ₂・nCuCO ₃ )] and basic zinc carbonate [Zn
Although some intermediates such as (OH) ₂ ·nZnCO ₃ ] often remain, their presence does not impede the removal of toxic components. These purifying agents may be used as they are or after being molded, or they may be supported on a carrier such as silica, silica alumina, diatomaceous earth, or calcium hydroxide; It is preferable to use a molded product or to crush this molded product into an appropriate size. As a molding method, a conventionally known dry method or wet method can be used. Further, during molding, a small amount of water, graphite, lubricant, etc. may be used as necessary. Although there is no particular restriction on the shape of the molded product, typical examples include a spherical shape, a cylindrical shape, and a cylindrical shape. The cleaning agent used in the present invention is filled into a cylinder. Gas containing toxic components (hereinafter referred to as gas to be treated) is flowed into this cylinder and brought into contact with a purifying agent, whereby various hydrides, which are toxic components, are removed and purified. There are no particular limitations on the concentration of hydrides in the gas to be treated and the flow rate of the gas to which the purification method of the present invention is applied. Generally, it is preferable to decrease the flow rate as the velocity increases. For example, if the gas to be treated is hydrogen-based, the concentration of toxic components contained is 10% or more, and the flow rate is 20%.
If the temperature exceeds cm/sec, the purifying agent may be reduced by hydrogen due to heat generation, and its activity may be lost.In such cases, it is recommended to take measures such as cooling the adsorption column before operation. preferable. The gases to be treated to which the purification method of the present invention can be applied are:
Usually in a dry state, but even in a wet state,
It is sufficient that the inside of the cleaning agent filling cylinder is not so damp as to cause dew condensation. There is no particular restriction on the contact temperature between the gas to be treated and the purifying agent, but it is usually at room temperature or room temperature and there is no need for particular heating or cooling. The pressure of the gas to be treated is not particularly limited, and is usually normal pressure, but may be under reduced pressure or pressurized state. [Example] Examples 1 and 2 Alumina sol or silica sol was added to cupric oxide powder with an atomic ratio of aluminum or silicon to copper of 93:7 (copper:aluminum), copper:silicon (copper:silicon).
The mixture was added in a ratio of 92:8, kneaded in a kneader, calcined at 350°C, and then molded into tablets of 6 mmφ x 6 mmH to prepare purifying agents. A hard polyvinyl chloride purification cylinder with an inner diameter of 13 mmφ x 200 mmH was filled with 1 g of the purification agent, and nitrogen gas containing 1 vol% arsine was flowed into the purification cylinder at a rate of 3/h as the gas to be treated. In each case, the time until breakthrough and the amount of saturated purification were measured. To detect breakthrough, detect the gas at the outlet of the purification tube using an arsine detection tube (manufactured by Gastech, No. 19L, lower detection limit).
0.05ppm), and the time was defined as the point at which traces were observed. The results are shown in Table 1. Examples 3 and 4 A mixture obtained by mixing copper nitrate and zinc nitrate at a metal atomic ratio of 9:1 was added to ion-exchanged water.
It was dissolved to a concentration of 20% by weight. On the other hand, to obtain these metal oxides, a stoichiometric amount of sodium carbonate was made into a 20% by weight aqueous solution. While stirring the nitrate mixed solution in a stirring tank, an aqueous sodium carbonate solution was added dropwise to form a mixed precipitate of basic copper carbonate and basic zinc carbonate. After filtering and washing the precipitate, it was dried at 120°C and then calcined at 350°C to obtain a mixture of cupric oxide and zinc oxide. This mixture was molded into pellets of 6 mmφ x 6 mmH, crushed, sieved,
28mesh was used as a purifying agent. 1 g of purification agent is filled into a hard polyvinyl chloride purification cylinder with an inner diameter of 13 mmφ x 200 mmH, and diborane or hydrogen selenide is added to the purification cylinder as the gas to be treated.
Nitrogen gas containing 1 vol% was flowed at a rate of 3/h, and the time until breakthrough and the saturated purification amount were measured when each purifying agent was filled. For diborane (RIKEN) as a detection tube for monitoring
CH-181 manufactured by Dräger, detection limit 0.1 ppm), for hydrogen selenide (No. 167 manufactured by Komei Rikagaku Co., Ltd., detection limit 0.1 ppm)
0.05ppm) was used. The results are shown in Table 1. As described above, it can be seen that gas containing various hydrides as toxic components discharged from semiconductor manufacturing processes can be efficiently purified in a dry state by the purification method of the present invention.

〔Effect of the invention〕

The purification method of the present invention has the following excellent features and is extremely useful industrially. (1) The amount and speed of removal of toxic components per unit weight of the purifying agent is large. (2) Various hydrides can be almost completely removed regardless of their concentration. (3) Purification operations can be performed at room temperature or room temperature;
No special heating or cooling is required. (4) Since the purifying agent contains virtually no moisture, stable purifying performance can always be obtained.

Claims (1)

[Scope of Claims] 1. A method for purifying exhaust gas for removing toxic components from a gas containing one or more of arsine, phosphine, ciborane, and hydrogen selenide as toxic components, wherein the gas is (a) cupric oxide. and (b) a method for purifying exhaust gas, which comprises bringing the exhaust gas into contact with a purifying agent containing respective oxides of silicon and/or aluminum. 2. An exhaust gas purification method for removing toxic components from a gas containing diborane and/or hydrogen selenide as toxic components, characterized by bringing the gas into contact with a purifying agent containing cupric oxide and zinc oxide. How to purify exhaust gas.