JPH0419886B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an advanced treatment method for silane-based exhaust gas. More specifically, the present invention relates to an advanced exhaust gas treatment method in which exhaust gas of a silane-based gas for semiconductor manufacturing is subjected to contact treatment by passing through a packed layer of metal oxide. The development of today's semiconductor industry is remarkable, and
Technological innovations such as LSI, compound semiconductors, and amorphous solar cells continue to advance rapidly, and the amount of gas used in semiconductor manufacturing is also increasing. Such semiconductor manufacturing gases, especially silane gases such as monosilane (SiH ₄ ), disilane (Si ₂ H ₆ ), and trisilane (Si ₃ H ₈ ), can be thermally decomposed, photolyzed,
By methods such as plasma decomposition, single crystal silicon,
It is an essential gas for forming polycrystalline silicon, amorphous silicon, silicon oxide films, silica nitride films, etc. However, such gases are reactive,
In addition to being highly pyrophoric, monosilane, for example, is highly toxic as it can severely irritate the respiratory tract upon absorption, and if released to the outside in high concentrations,
The negative effects on the human body and the natural environment are immeasurable. Therefore, in Japan, regulations on the concentration of silane-based gases in exhaust gas in the semiconductor industry are being tightened for the purpose of maintaining a good working environment and preventing destruction of the natural environment. Furthermore, strict regulations are being implemented in the United States, with the American Board of Industrial Hygienists setting the concentration of monosilane in the working environment at 0.5 ppm. Normally, for semiconductor manufacturing, silane-based gases diluted from several percent to several tens of percent with gases such as hydrogen, helium, argon, and nitrogen are often used, but sometimes undiluted 100% silane-based gases are used. Gas may also be used. Semiconductor manufacturing equipment is broadly classified into normal pressure method and reduced pressure method depending on the method of film growth. (1) In the case of the normal pressure method, a large amount of gas containing a high concentration of silane gas is discharged, but it is usually treated with a device that mixes the exhaust gas with air and burns it, or oxidizes the exhaust gas. Method of contact treatment with alkaline aqueous solution (JP-A-56-84619, JP-A No. 57-
After reducing the silane gas concentration as much as possible using methods such as No. 94323), it is released into the atmosphere. On the other hand, the reduced pressure method has the advantage of being mass-producible and producing a thin, uniform film, but since a vacuum pump is interposed between the reaction chamber (film forming chamber) and the exhaust gas treatment equipment, unreacted silane gas is This can cause problems such as pump failure, deterioration, and fire. For this reason, methods have been adopted such as installing a metal filter made of aluminum or the like heated to a high temperature between the reaction chamber and the vacuum pump to treat the silane gas (Japanese Patent Laid-Open No. 53-99071). However, in the exhaust gas that can be treated by these conventional methods such as combustion, contact treatment with an aqueous alkali hydroxide solution, or treatment using a metal filter,
High concentration of silane gas of 5ppm or more remains,
This figure cannot be overlooked from the standpoint of protecting the natural environment and occupational safety and health. In addition, the method using a metal filter has additional limitations such as the need to heat it to 600°C or higher. Therefore, it is a method that can be used not only in the normal pressure method but also in the reduced pressure method, and that eliminates at least the silane gas in the exhaust gas.
This is because the development of a technology that completely removes down to 0.5 ppm, preferably 0.1 ppm is expected. That is, an object of the present invention is to provide a method for almost completely removing silane-based gas from exhaust gas from semiconductor manufacturing equipment, and the gist thereof is to provide a method for almost completely removing silane-based gas from exhaust gas from semiconductor manufacturing equipment. By passing the exhaust gas through a packed bed mainly composed of solid metal oxides and treating it, the concentration of silane gas in the exhaust gas is reduced to at least 0.5 ppm or less, preferably 0.1 ppm or less, that is, substantially This is a method that can reduce the content to zero. The present invention will be explained in detail below. The solid metal oxide used in the packed bed of the present invention includes elements other than hydrogen and francium in group a of the periodic table; elements other than Ra in group a; elements other than boron in group a; and excluding carbon in group A. Elements; Va group elements excluding nitrogen, phosphorus, and arsenic; B group; b
Group: Particles of oxides of metal elements of transition elements including lanthanum-based and actinium-based thorium and uranium, which are used alone, as a mixture, or with a metal supported thereon. In the present invention, exhaust gas containing silane gas is aerated through the packed bed mainly composed of the metal oxide, but in this case, the metal oxide particles are made fine and the particle size is 0.1 m ² /g. With a surface area of more than
It is desirable to improve the gas-solid contact ability with silane gas. Furthermore, in order to improve the exhaust gas processing ability of the metal oxide, it is effective to feed the exhaust gas while heating the packed bed. However, depending on the type of metal oxide, there are some that do not require heating at all and can sufficiently perform their exhaust gas removal function even at room temperature. Depending on the desired removal rate, this may not necessarily be necessary. In addition, as shown in the examples, in the treatment method using a metal oxide in the present invention,
When the temperature of the packed bed is 200°C or less, the concentration of silane gas in the exhaust gas can be reduced to 0.1 ppm or less, that is, below the detection limit. Although one series of packed beds is sufficient for carrying out the present invention, from the viewpoint of operations such as regeneration and replacement of the packing material, a plurality of parallel packed beds are used, and each one is a processing layer and a regeneration layer. It is desirable to switch between them. In actual semiconductor manufacturing, a silicon film is often doped with boron, phosphorus, etc. using a silane-based gas, but according to the present invention, gases such as phosphine, diborane, arsine, etc. used as such doping gases can also be doped. It has the advantage that it can be removed together with the silane gas. Hereinafter, the present invention will be specifically explained with reference to Examples. Examples 1-50 Figure 1 shows the experimental apparatus used in the examples. 1 was a 25 mmφ x 450 mm quartz tube, and 150 ml of solid metal particles were filled in this tube so that the height of the packed bed was 300 mm to form a packed bed 2. The packed bed portion can be heated in an electric furnace 3 in a range from room temperature to 800°C. Pure monosilane gas was diluted with nitrogen gas to prepare a monosilane-containing gas at a predetermined concentration and stored in the gas reservoir 4. Next, this gas was passed through a flow meter 5, a needle valve 6, and a pump 7 to be aerated into a packed bed 2 mainly composed of solid metal oxide (sieved to have a uniform particle size). The packed bed outlet gas 8 was collected and the monosilane concentration in the gas was analyzed. Analysis was performed using a gas chromatograph equipped with a photoionization detector. The separation column is Porapak-T, and the detection limit for monosilane is 0.1 ppm.
The experimental results are shown in Table 1. In FIG. 1, 8 is a supply port for purging N ₂ gas, and 9 is also an outlet. Examples 51 to 100 Pure disilane gas was diluted with nitrogen gas to adjust a disilane-containing gas at a predetermined concentration. Next, experiments were conducted in the same manner as in Examples 1 to 50 using the same apparatus. Note that the detection limit of disilane analysis by gas chromatography is 0.1 ppm. The experimental results are shown in the second
Shown in the table. Examples 101 to 110 Monosilane or disilane was diluted with nitrogen gas to a predetermined concentration, mixed with an equivalent amount of air, and partially combusted. Monosilane or disilane was analyzed in the same manner as in Examples 1 to 50. . The experimental results are shown in Table 3. Comparative Examples 1 to 12 Experiments were conducted in the same manner as Examples 1 to 50 by passing the monosilane- or disilane-containing gas used in the Examples through a packed bed of glass, natural crystal, and silver sand. The experimental results are shown in Table 4.

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[Table] *Indicates non-detection Same below

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【table】 [Brief explanation of drawings]

FIG. 1 is a flow sheet diagram showing an apparatus for carrying out the present invention.

Claims (1)

[Claims] 1. The exhaust gas containing the silane gas discharged from the semiconductor device is passed through a packed bed mainly composed of solid metal oxide, and the concentration of the silane exhaust gas is efficiently removed to at least 0.5 ppm or less. An advanced treatment method for exhaust gas.