JP2021038454A - Exhaust gas treatment method and manufacturing method of silicon carbide polycrystal wafer - Google Patents

Abstract

To provide an exhaust gas treatment method capable of preventing a high-order chlorosilane polymer from precipitating in an exhaust pipe to suppress clogging the exhaust pipe, and a manufacturing method of a silicon carbide polycrystal water.SOLUTION: An exhaust gas treatment method includes an exhaust gas introducing step where an exhaust gas including a chlorine-containing silicon source gas exhausted from a film deposition chamber for depositing a silicon carbide polycrystal by a chemical vapor deposition is introduced into an exhaust gas treatment chamber with a silicon carbide precipitation plate at a room temperature of 1400 K-1800 K, a mole ratio controlling step where a mole ratio of carbon and silicon C:Si in the exhaust gas contacting the silicon carbide precipitation plate is controlled to 1.1-2.0:1, and a silicon carbide precipitation step where the exhaust gas after the mole ratio controlling step is reacted on the silicon carbide precipitation plate to precipitate a silicon carbide.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust gas treatment method and a method for producing a silicon carbide polycrystalline wafer. Specifically, a method for manufacturing a silicon carbide polycrystalline wafer by using a substrate processing apparatus having a vertical arrangement structure in which a plurality of silicon carbide polycrystalline substrates are arranged in a direction of stacking them with a gap between them, and exhaust gas discharged. It relates to a processing method.

Silicon carbide (SiC) is a wide bandgap semiconductor having a wide forbidden bandwidth of 2.2 to 3.3 eV, and due to its excellent physical and chemical properties, for example, high frequency electronic devices, high withstand voltage and high output. Research and development of devices (semiconductor devices) made of silicon carbide, including electronic devices and short-wavelength optical devices from blue to ultraviolet, are being actively carried out. In order to promote the practical use of SiC devices, it is required to manufacture a large-diameter silicon carbide substrate for high-quality SiC epitaxial growth. Currently, most of them are manufactured by a sublimation recrystallization method (called an improved Rayleigh method, an improved Rayleigh method, etc.) using a seed crystal, a CVD method (chemical vapor deposition method), or the like.

The method for producing a silicon carbide substrate using the CVD method is to cause a vapor phase reaction of a raw material gas, deposit a silicon carbide product on the surface of the base material to form a film, and then remove the base material. A high-purity silicon carbide substrate can be obtained. The base material is removed by cutting, polishing, or the like, but if a carbon material is used as the base material, it can be removed by heat treatment in air.

In Patent Document 1, as a method for manufacturing a silicon carbide substrate by a CVD method, a silicon carbide film is formed on the surface of a base material by a chemical vapor deposition method, and then the base material is removed to form both surfaces of the silicon carbide substrate. Further, a method for producing a silicon carbide substrate by a chemical vapor deposition method, which comprises forming a silicon carbide film, has been proposed.

_{Further, in Non-Patent Documents 1 and 2, chlorosilane-based gas such as SiCl 4} , SiHCl _3, etc. may be used as a silicon-based raw material gas in order to suppress the generation of Si particles and form SiC at high speed. Proposed. Of the chlorosilane-based gas in the raw material gas, a part of the chlorosilane-based gas is precipitated as SiC on the substrate to be formed into a film, and most of the chlorosilane gas is exhausted as waste gas without becoming SiC. Then, as the temperature of the waste gas decreases, the chlorosilane-based gas becomes a higher-order chlorosilane polymer and precipitates on the exhaust pipe or the like, which may cause the exhaust pipe or the like to be blocked.

Higher-order chlorosilane polymers not only block pipes, but are also hydrolyzed by moisture in the atmosphere, and as shown in Non-Patent Document 3, for example, incomplete hydrolysates may form explosive compounds. It is known. Therefore, care must be taken in how to handle exhaust pipes and other parts to which higher-order chlorosilanepolymer is attached, and in cleaning these.

Therefore, in Patent Document 2, in a film forming apparatus that uses methyltrichlorosilane gas as a raw material to generate SiC, the temperature of the exhaust gas discharged from the film forming apparatus is maintained at 750 ° C. to 850 ° C. without lowering. It is disclosed that this is introduced into an exhaust gas treatment device (reformer), and further, chloromethane gas is added to the exhaust gas containing chlorosilane-based gas to cause a reaction. As a result, the SiCl ₂ gas in the exhaust gas can be reformed to SiCl ₄ , SiHCl ₃ , CH ₃ SiCl ₃ , C ₂ H ₃ SiCl _{3, etc.} It is disclosed that the formation of chlorosilane polymer can be suppressed. Further, Patent Document 2 describes that precipitation of exhaust gas as solid SiC in an exhaust gas treatment apparatus and formation of solid SiC are effective in reducing the formation of higher-order chlorosilanepolymer. There is.

Japanese Unexamined Patent Publication No. 8-188408 WO2018 / 0083642

Toshio Hirai, Takashi Goto, Toshihiko Kaji Ceramics Association Magazine Vol.91, No11, (1983) 503 Yuuki Ishida J. Vac. Soc. Jpn. Vol. 54, No. 6, (2011) 346 Mitsubishi Materials Corporation Yokkaichi Factory High-purity polycrystalline silicon manufacturing facility Explosion and fire accident investigation report http://www.mmc.co.jp/corporate/ja/01/01/14-0612a.pdf

However, in the method of Patent Document 2, it is not possible to convert all the chlorosilane-based gas in the exhaust gas into solid SiC, and the higher-order chlorosilane polymer is deposited on the exhaust pipe or the like, so that the exhaust pipe or the like is blocked. It may not be possible to completely prevent this from happening. In addition, since the exhaust gas contains _{high vaporization temperature, flammable and harmful chlorosilane gas such as SiCl 4} , SiHCl ₃ , CH ₃ SiCl ₃ and C ₂ H ₃ SiCl ₃ , the exhaust gas is collected by a low temperature recovery device. There is a problem that it is necessary to collect it.

Therefore, in view of the above problems, the present invention provides an exhaust gas treatment method and silicon carbide that can prevent high-order chlorosilanepolymer from precipitating on the exhaust pipe or the like and prevent the exhaust pipe or the like from being blocked. It is an object of the present invention to provide a method for producing a polycrystalline wafer.

The exhaust gas treatment method of the present invention comprises a silicon carbide deposition plate for exhaust gas containing a chlorine-containing silicon source gas discharged from a film forming chamber for forming a silicon carbide polycrystal by chemical vapor deposition, and has a room temperature of 1400 K or more. The molar ratio of carbon to silicon in the exhaust gas in contact with the silicon carbide deposition plate, C: Si, is controlled to 1.1 to 2.0: 1 in the exhaust gas introduction step of introducing into the exhaust gas treatment chamber of 1800 K. The control step includes a silicon carbide precipitation step of reacting the exhaust gas after the molar ratio control step with the silicon carbide precipitation plate to precipitate silicon carbide.

According to the present invention, an exhaust gas treatment method and a method for producing a silicon carbide polycrystalline wafer, which can prevent high-order chlorosilanepolymer from depositing on an exhaust pipe or the like and prevent the exhaust pipe or the like from being blocked, can be used. Can be provided.

It is the schematic which shows the cross section seen from the upper surface of the silicon carbide polycrystalline wafer manufacturing apparatus 1000. It is a front schematic view which looked at the 1st surface 110 from the inside of a film forming chamber 110. It is a front schematic view which looked at the 2nd surface 120 from the inside of the film forming chamber 110. It is a schematic diagram of a substrate holder 500. It is a schematic diagram explaining the ejection of a mixed gas. It is the schematic which shows the cross section seen from the upper surface of the exhaust gas treatment apparatus 900a, 900b. It is sectional drawing of the silicon carbide polycrystalline wafer manufacturing apparatus 2000. It is the schematic which shows the cross section seen from the upper surface of the silicon carbide polycrystalline wafer manufacturing apparatus 3000. It is a schematic diagram of the silicon carbide precipitation plate 943. It is the schematic which shows the cross section seen from the upper surface of the exhaust gas treatment apparatus 900d, 900e.

As a result of diligent studies to solve the above problems, the present inventors have provided a gas treatment device having a SiC deposition plate adjacent to a SiC film forming chamber, for example, in a hot wall type CVD device. , Exhaust gas discharged from the film formation chamber is introduced into this gas treatment device, and carbon source gas is appropriately added to the exhaust gas to control the C / Si gas concentration ratio in the gas treatment device to 1.1 or more and 2.0 or less. After that, by reacting the exhaust gas with the SiC precipitation plate to form solid SiC, it is possible to prevent the higher-order chlorosilane polymer from depositing on the exhaust pipe, etc., and to prevent the exhaust pipe, etc. from being blocked. I found it.

Hereinafter, an embodiment of the exhaust gas treatment method and the method for producing a silicon carbide polycrystalline wafer of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

<Silicon Carbide Polycrystalline Wafer Manufacturing Equipment 1000>
FIG. 1 shows an outline showing a cross section of the silicon carbide polycrystalline wafer manufacturing apparatus 1000 as viewed from the upper surface as an embodiment of the silicon carbide polycrystalline wafer manufacturing apparatus that can be used in the exhaust gas treatment method and the silicon carbide polycrystalline wafer manufacturing method of the present invention. The figure is shown. The manufacturing apparatus 1000 includes a film forming chamber 100, a mixed gas ejection port 200, a mixed gas discharge port 300, a heater 400, a substrate holder 500, and an exhaust gas treatment apparatus 900.

<Film formation chamber 100>
The film forming chamber 100 has a rectangular parallelepiped inner shape composed of a first surface 110, a second surface 120 facing the first surface 110, and four side surfaces 130 connecting the first surface 110 and the second surface 120. .. By adopting a rectangular parallelepiped internal shape, when a plurality of substrates 600 are installed in the film forming chamber 100, the shapes of the gap between the substrates and the gap between the substrates and the side surface 130 are the same or similar. can do. Therefore, similarly to the mixed gas flowing between the substrates, the mixed gas flowing between the side surface 130 and the substrate can be uniformly flowed from the mixed gas ejection port 200 toward the mixed gas discharge port 300. As a result, a film that is uniform and has little variation can be formed on the substrate.

For example, when the inner shape of the film forming chamber 100 is not a rectangular parallelepiped shape but a tubular shape, the shapes of the gap between the substrate and the substrate and the shape of the gap between the substrate and the side surface 130 are significantly different. The mixed gas flowing between the side surface 130 and the mixed gas flowing between the side surface 130 and the substrate does not flow uniformly. As a result, the film formed between the substrates and the film formed between the substrates and the side surface 130 may become non-uniform, and a film having a large variation between the substrates may be formed.

The inner shape of the film forming chamber 100 may be large enough to accommodate the substrate holder 500 and the substrate 600 held in the substrate holder 500, and the mixed gas not involved in the film formation is discharged from the mixed gas outlet 200. It is preferable not to provide an extra space as much as possible so that the gas flows toward the outlet 300 and is discharged from the film forming chamber 100.

Further, the film forming chamber 100 is preferably made of graphite. If graphite is used, it can be easily processed into a rectangular parallelepiped shape, and by creating an inert atmosphere at the time of film formation, it is possible to have sufficient durability under high temperature film formation conditions.

<Mixed gas outlet 200>
The mixed gas ejection port 200 is located on or near the first surface 110 of the film forming chamber 100, and ejects a mixed gas containing a raw material gas and a carrier gas into the film forming chamber 100. It is preferable that there are a plurality of mixed gas outlets 200, but there may be one. Since there are a plurality of mixed gas ejection ports 200, the mixed gas can be ejected more uniformly into the film forming chamber 100 as compared with the case where there is only one. As an example of the mixed gas ejection port 200, it corresponds to the opening end portion where the mixed gas is ejected in the mixed gas introduction pipe 210 through which the mixed gas flows. The mixed gas ejection port 200 may be located on the first surface 110, and is in the vicinity of the first surface 110 as shown in FIG. 1, and the gas leakage of the mixed gas may occur on the inner side of the film forming chamber 100 or as a gas leak of the mixed gas. It may be outside the film forming chamber 100 on the premise that there is no such gas. As a guide, the vicinity is, for example, about 20 mm from the first surface 110 to 20 mm. In addition, a temperature control means such as a heater capable of appropriately heating the mixed gas introduction pipe 210 and a cooler capable of cooling may be provided so that the temperature of the mixed gas ejection port 200 can be controlled.

FIG. 2 shows a schematic front view of the first surface 110 as viewed from the inside of the film forming chamber 110. In FIG. 2, four mixed gas outlets 200 are arranged in a row on the first surface 110. The direction in which the four mixed gas ejection ports 200 are arranged can be matched with the direction in which the substrates 600 are arranged side by side in the substrate holder 500. It is possible to evenly discharge the mixed gas from each of the mixed gas outlets 200. The inner diameter of the mixed gas outlet 200 may be optimal depending on the number of mixed gas outlets 200 and the ejection conditions, and is not particularly limited as long as there is no problem in ejecting the mixed gas, but is set in the range of, for example, 10 mm to 25 mm. can do. Further, the distance between the adjacent mixed gas outlets 200 may be optimal depending on the number of the mixed gas outlets 200 and the ejection conditions, and is not particularly limited as long as there is no problem in ejecting the mixed gas, but is, for example, 2 mm or more. It can be set in the range of 16 mm. Further, the mixed gas ejection port 200 may be arranged on the first surface 110 by a plurality of rows and a plurality of columns.

<Mixed gas discharge port 300>
The mixed gas discharge port 300 is located on or near the second surface 120 of the film forming chamber 100, and discharges the mixed gas from the film forming chamber 100. As an example of the mixed gas discharge port 300, it corresponds to an opening end portion where the mixed gas is discharged in the mixed gas discharge pipe 310 which is circulated for discharging the mixed gas to the outside of the film forming chamber 100. The mixed gas discharge port 300 may be located on the second surface 120, and is in the vicinity of the second surface 120 as shown in FIG. 1, and the gas leakage of the mixed gas may occur on the inner side of the film forming chamber 100 or in the film forming chamber 100. It may be outside the film forming chamber 100 on the premise that there is no such gas. As a guide, the vicinity is, for example, about 20 mm from the second surface 120 to 20 mm. The temperature of a heater that can be appropriately heated, a cooler that can be cooled, or the like in order to control the temperature of the mixed gas discharge port 300 or the mixed gas discharge pipe 310 so that silicon carbide or the like does not precipitate in the mixed gas discharge port 300 or the mixed gas discharge pipe 310. A control means may be provided.

FIG. 3 shows a schematic front view of the second surface 120 as viewed from the inside of the film forming chamber 100. In FIG. 3, one mixed gas discharge port 300 is arranged in the center of the second surface 120. The mixed gas discharge port 300 may be one or a plurality of mixed gas discharge ports 300 as long as the mixed gas can be discharged without any problem even if a small amount of silicon carbide or the like is formed, but even if a small amount of silicon carbide or the like is formed. It is preferable that the opening diameter is about 1/5 to 1/2 of one side of the second surface so that the mixed gas can be discharged without any problem.

<Heater 400>
The heater 400 surrounds the four side surfaces 130 of the film forming chamber 100 and heats the film forming chamber 100. By controlling the heater 400, the temperature of the film forming chamber 100 can be controlled to a temperature suitable for forming a film on the substrate. As the heater 400, a heater useful for the thermal CVD method can be used, and for example, a tubular carbon heater or a cantal heater can be used.

<Board holder 500>
FIG. 4 shows a schematic view of the substrate holder 500. FIG. 4A is a side view of the substrate holder 500 holding the substrate 600, and FIG. 4B is a front view of the substrate holder 500 seen from the first surface 110 side inside the film forming chamber 100. The substrate holder 500 can hold a plurality of substrates 600 by stacking and holding the substrates 600 at equal intervals in a non-contact manner, and the substrate 600 is placed between the first surface 110 and the second surface 120 of the film forming chamber 100. The film formation target surface 610 can be installed in parallel with the side surface 130 of the film formation chamber 100.

In FIG. 4, the substrate holder 500 can hold the substrate 600 by sandwiching the substrate 600 from two upper and lower positions by the upper holding rod 510 and the lower holding rod 520, and both the upper holding rod 510 and the lower holding rod 520 are the substrate 600. It has grooves 511 and 521 for holding the above. However, the substrate holder is not limited to this, and the substrate can be held at three or four locations by having holding rods at the front and rear as well as at the top and bottom.

The substrate holder 500 is involved in film formation because, for example, both the upper holding rod 510 and the lower holding rod 520 are in close contact with the upper side surface 130a and the lower side surface 130b of the side surface 130 of the film forming chamber 100. It is possible to prevent a large amount of mixed gas that is not used from flowing from the mixed gas ejection port 200 toward the mixed gas discharge port 300 and being discharged in large quantities from the film forming chamber 100.

In FIG. 4B, the film forming target surface 610 of the substrate 600 is installed in parallel with the left side surface 130c and the right side surface 130d of the side surface 130 of the film forming chamber 100, and the upper side surface 130a and the lower side surface 130b. It is installed vertically. However, by changing the shape of the substrate holder 500, the film formation target surface 610 of the substrate 600 can be installed perpendicularly to the left side surface 130c and the right side surface 130d, and can be installed parallel to the upper side surface 130a and the lower side surface 130b. .. That is, the substrate 600 may be laminated in the vertical direction or may be laminated in the horizontal direction. However, if the substrate 600 is installed so that the film-forming target surface 610 faces the mixed gas ejection port 200 and the film-forming target surface 610 is parallel to the first surface 110 and the second surface 120, the substrate 600 is installed between the substrates. This is not preferable because the mixed gas does not flow uniformly.

Further, the width 700 of the gap between the film-forming target surface 610 and the left side surface 130c of the substrate 600 and the width 710 of the gap between the right side surface 130d are the same as the width 720 of each gap between the substrates 600 laminated at equal intervals. In this case, since the mixed gas flows uniformly through these gaps, it is possible to form a film having little variation in thickness between the substrates or on the same surface to be formed.

<Ejection speed of mixed gas>
FIG. 5 shows a schematic diagram illustrating the ejection of the mixed gas. It schematically shows the spread of the mixed gas when the collision between molecules in the mixed gas is ignored, and when it naturally diffuses from the mixed gas outlet 200 on the first surface without pressurizing the mixed gas. Let Vd be the diffusion rate of Vd, and Vg be the ejection rate when the mixed gas is pressurized and ejected from the mixed gas outlet 200.

When the diffusion speed Vd is faster than the ejection speed Vg, the diffusion of the mixed gas 800 proceeds slowly (FIG. 5A), so that the amount of the raw material gas supplied to the film forming chamber 100 is small and the film forming rate is slow. There is a risk of becoming. The temperature of the mixed gas outlet is lowered (for example, 1200 K or less) by providing a certain distance between the substrate 600 and the mixed gas outlet 200 in the film forming chamber 100 so that the mixed gas outlet 200 is not formed by the mixed gas. If control is attempted, it will take more time to form a film because there is a distance before the mixed gas 800 reaches the substrate 600.

In consideration of this point, in the manufacturing apparatus 1000, the ejection speed of the mixed gas ejected from the mixed gas ejection port 200 can be made faster than the diffusion speed of the mixed gas. That is, by making the ejection speed Vg faster than the diffusion velocity Vd (FIG. 5B), the mixed gas 810 is forcibly discharged from the mixed gas ejection port 200. As a result, even when the distance between the substrate 600 and the mixed gas ejection port 200 is provided to some extent in the film forming chamber 100, it is possible to suppress a decrease in the film forming speed. That is, while maintaining the same film formation rate as the conventional method, it is possible to prevent the mixed gas ejection port 200 from forming a film by the mixed gas and reducing the diameter and the mixed gas ejection port 200 from being blocked. be able to.

Forcibly discharging the mixed gas 810 from the mixed gas outlet 200 in order to make the ejection speed Vg faster than the diffusion velocity Vd is, for example, adjusting the amount of gas by an ejection speed control means such as a regulator, a compressor, or a suction device. It is possible by doing. For example, by setting the ejection speed Vg to 0.4 m / sec or more, the diameter of the mixed gas ejection port 200 becomes smaller due to the deposition of the mixed gas while maintaining the same film formation rate as the conventional method. , It is possible to easily prevent the mixed gas outlet 200 from being blocked. Further, when the ejection speed Vg is 1 m / sec or more, the film forming speed can be clearly increased as compared with the conventional method, and the film forming processing time can be shortened more effectively. When a plurality of mixed gas outlets 200 are provided in the manufacturing apparatus 1000 of the present invention, the ratio of the number of substrates 600 that can be held by the substrate holder 500 to the number of mixed gas outlets 200 is 1: 0. It is preferably .4 to 1.5. If the ratio of the number of substrates 600 that can be held by the substrate holder 500 to the number of ports of the mixed gas ejection port 200 is 1: 0.4 to 1.5, the above-mentioned uniformity of gas speed and gas flow rate is satisfied. At the same time, it is possible to prevent a decrease in the film formation rate.

In the manufacturing apparatus 1000, the shortest distance between the mixed gas ejection port 200 and the substrate holder 500 is preferably 150 mm or more. Although the optimum shortest distance differs depending on the ejection speed and gas flow rate of the mixed gas 810 and the number of mixed gas ejection ports 200, if the above shortest distance is 150 mm or more, film formation around the substrate 600 in the film forming chamber 100 The temperature around the mixed gas ejection port 200 can be sufficiently lowered from the temperature. As a result, it is possible to easily prevent the mixed gas outlet 200 from becoming smaller in diameter due to the film formation of the mixed gas and the mixed gas outlet 200 from being blocked.

<Exhaust gas treatment device 900>
The exhaust gas treatment device 900 is a device that treats the exhaust gas discharged from the film forming chamber 100. Specifically, the exhaust gas treatment device 900 is arranged downstream of the film forming chamber 100 and is a chlorine-containing silicon source in the exhaust gas in the exhaust gas treatment device 900. This is a device that deposits silicon carbide by reacting gas with carbon. By recovering the silicon in the exhaust gas as silicon carbide in the exhaust gas treatment device 900, the silicon in the exhaust gas can be diluted. Therefore, it is possible to prevent the higher-order chlorosilane polymer from being deposited in the equipment located downstream of the exhaust gas treatment device 900 such as the exhaust pipe 350 and discharging the exhaust gas discharged from the exhaust gas treatment device 900 to the outside of the production device 1000. , It is possible to prevent the inside of the equipment from being blocked.

The exhaust gas treatment device 900 is preferably arranged so as to be surrounded by the heater 400 so that the inside thereof can be adjusted to a temperature suitable for precipitation of silicon carbide.

[Embodiment 1 of exhaust gas treatment device]
FIG. 6 shows a schematic view showing a cross section of the exhaust gas treatment devices 900a and 900b as viewed from the upper surface. FIG. 6A shows an exhaust gas treatment device 900a as one aspect of the exhaust gas treatment device 900, and FIG. 6B shows an exhaust gas treatment device 900b having a mode different from that of the exhaust gas treatment device 900a.

The exhaust gas treatment device 900a has a box-shaped housing 910a, an exhaust gas introduction port 920a for introducing the exhaust gas discharged from the film forming chamber 100 into the housing 910a, and an exhaust gas introduction port 920a for discharging the exhaust gas from the inside of the housing 910a to the outside. It is provided with an exhaust gas discharge port 930a. For example, by directly connecting the exhaust gas introduction port 920a to the mixed gas discharge pipe 310 shown in FIG. 1, the exhaust gas discharged from the film forming chamber 100 can be introduced into the exhaust gas treatment device 900a. Further, by directly connecting the exhaust gas discharge port 930a to the exhaust pipe 350 shown in FIG. 1, the exhaust gas can be discharged from the exhaust gas treatment device 900a to the exhaust pipe 350.

The exhaust gas treatment device 900a can be provided with a carbon source gas introduction pipe 950a capable of introducing a carbon source gas inside the housing 910a. Thereby, the content of carbon and silicon in the exhaust gas can be adjusted so that the silicon carbide can be efficiently deposited. The exhaust gas treatment device 900a includes a detection means for detecting the contents of carbon and silicon in the exhaust gas, and a temperature measuring means and a heater 400 so that the inside of the exhaust gas treatment device 900a can be controlled to a temperature suitable for precipitation of silicon carbide. A control means may be provided.

Further, inside the housing 910a, a plurality of silicon carbide precipitation plates 940a are provided as plates for depositing silicon carbide. Since the reaction in which silicon carbide is produced by chemical vapor deposition from a chlorine-containing silicon source gas and carbon occurs only on the solid surface, in order to efficiently generate silicon carbide from the exhaust gas, the exhaust gas must be efficiently collided with the solid surface. Is preferable. Therefore, a plurality of silicon carbide precipitation plates are distributed so that the exhaust gas can be efficiently collided with the surface of the silicon carbide precipitation plate 940a to efficiently deposit silicon carbide on the surface of the silicon carbide precipitation plate 940a. It is preferable that the housing 910a is arranged inside the housing 910a so as to hinder the above.

For example, in the case of the exhaust gas treatment device 900a, a plate-shaped silicon carbide precipitation plate 941a formed in the center inside the housing 910a and a plate-shaped silicon carbide precipitation plate 941a formed so as to protrude from the inner wall of the housing 910a. A plate 942a is provided. Both the silicon carbide precipitation plates 941a and 942a are arranged so that their longitudinal directions are parallel to the intrusion direction of the exhaust gas entering from the exhaust gas introduction port 920a. Then, the silicon carbide precipitation plates 941a and 942a are alternately arranged from the exhaust gas introduction port 920a toward the exhaust gas discharge port 930a.

In FIG. 6A, three silicon carbide precipitation plates 941a are provided, but any number can be provided depending on the installation mode of the exhaust gas treatment device 900, and the number is not limited to three. Even if there is only one silicon carbide precipitation plate 941a, it is possible to precipitate silicon carbide from the exhaust gas, and it is preferable that two or more are provided, and more preferably four or more.

On the other hand, in the case of the exhaust gas treatment device 900b shown in FIG. 6B, the silicon carbide precipitation plate 941b formed in the center of the inside of the housing 910a and the plate shape formed so as to protrude from the inner wall of the housing 910a. The silicon carbide precipitation plate 942b of the above is provided. Unlike the exhaust gas treatment device 900a, the silicon carbide precipitation plate 941b has a dogleg-shaped cross section whose central portion bends toward the exhaust gas discharge port 930a, and a taper extending from the exhaust gas discharge port 930a toward the exhaust gas introduction port 920a. It is in the shape. Further, although the silicon carbide precipitation plate 942b has a plate shape like the silicon carbide precipitation plate 942a, it is installed so as to be inclined so that the tip is inclined toward the exhaust gas introduction port 920a. As a result, a region A is formed in which the exhaust gas that has entered the inside of the housing 910a cannot pass through and easily stays in the housing. Silicon carbide can be deposited more efficiently on the surface of the.

The exhaust gas treatment device 900b includes a box-shaped housing 910a, an exhaust gas introduction port 920a, an exhaust gas discharge port 930a, and a carbon source gas introduction pipe 950a, similarly to the exhaust gas treatment device 900a.

[Embodiment 2 of exhaust gas treatment device]
Further, in the manufacturing apparatus 1000 of FIG. 1, the exhaust gas treatment apparatus 900 having a box-shaped housing 910a adjacent to the film forming chamber 100 has been illustrated, but the present invention is not limited to this, and the box-shaped exhaust gas treatment apparatus 900 is installed. When there is no place, for example, the exhaust gas treatment device 900 may be provided in a shape corresponding to the vacant space of the manufacturing device.

For example, in the manufacturing apparatus 2000 shown in FIG. 7, an exhaust gas treatment device 900c is provided so as to cover the outside of the film forming chamber 100, and an exhaust pipe 350a is installed at the end of the exhaust gas treatment apparatus 900c (FIG. 7 (FIG. 7). a)). FIG. 7B is a cross-sectional view taken along the line AA'of FIG. 7A. The exhaust gas treatment device 900c covers the outside of the film forming chamber 100 and is covered with the outer cylinder 1100 inside the ceramic core tube 1300. ing.

FIG. 7 (c) is a cross-sectional view of the exhaust gas treatment device 900c in the region R of FIG. 7 (a). In the exhaust gas treatment device 900c, the space 960 through which the exhaust gas passes and the walls 970a and b that block the exhaust gas are alternately arranged. 7 (d) is a cross-sectional view of BB'of FIG. 7 (c), and FIG. 7 (e) is a cross-sectional view of CC'of FIG. 7 (c). As shown in FIGS. 7 (d) and 7 (e), the walls 970a and b are provided with passage ports 980a and 980b through which exhaust gas can pass. The passage port 980a is provided near the left and right ends of the wall 970a so that the exhaust gas flow is blocked, whereas the passage port 980b is provided near the upper and lower ends of the wall 970b.

By passing the exhaust gas through the exhaust gas treatment device 900c, silicon carbide can be deposited on the inner wall of the space 960 and the inner walls of the passage ports 980a and 980b.

The areas of the silicon carbide precipitation plates 940a and 940b vary depending on the precipitation rate of silicon carbide (that is, the consumption rate of the chlorine-containing silicon source gas), but the temperature inside the exhaust gas treatment device 900 is set to 1400K as a suitable temperature for precipitation of silicon carbide. When it is set to about 1800 K, the film formation rate of silicon carbide can be expected to be 50 to 100 μm / hr or more. When the film formation rate is 50 μm / hr, the consumption of the chlorine-containing silicon source gas is 4 mol / square meter / hr, and when the film formation rate is 100 μm / hr, the consumption of the chlorine-containing silicon source gas is 8 mol. Since it corresponds to / square meter / hr, if the exhaust gas treatment device 900 has silicon carbide precipitation plates 940a and 940b having an area capable of treating the entire amount of the chlorine-containing silicon source gas in the exhaust gas, the total amount of the chlorine-containing silicon source gas. Can be recovered as silicon carbide. Since silicon carbide is formed in the film forming chamber 100, the concentration of the chlorine-containing silicon source gas in the exhaust gas is lower than the concentration of the chlorine-containing silicon source gas in the raw material gas.

[Embodiment 3 of exhaust gas treatment device]
FIG. 9 shows a schematic view of the silicon carbide precipitation plate 943. FIG. 9A is a side sectional view of the silicon carbide precipitation plate 943, and FIG. 9B is a perspective view of the silicon carbide precipitation plate 943. Further, FIG. 10 shows a schematic view showing a cross section of the exhaust gas treatment devices 900d and 900e as viewed from the upper surface.

The reaction to produce silicon carbide by chemical vapor deposition from a chlorine-containing silicon source gas and carbon occurs only on the solid surface. Therefore, in order to efficiently generate silicon carbide from the exhaust gas, it is preferable to efficiently collide the exhaust gas with the solid surface. From this point of view, the silicon carbide precipitation plates 940a and 940b are precipitation plates in which silicon carbide is deposited with their surfaces as solid surfaces, while the silicon carbide precipitation plates 943 are filled inside. It is a precipitation plate in which silicon carbide is precipitated with the surface of carbon particles as a solid surface.

<Silicon Carbide Precipitate Plate 943>
The silicon carbide precipitation plate 943 has a hollow internal space 943a filled with carbon particles 10 and a front surface that is upstream of the internal space 943a in the direction D1 in which the exhaust gas flows and intersects the direction D1 in which the exhaust gas flows. It includes 943b and a back surface 943c that is downstream of the internal space 943a in the direction D1 in which the exhaust gas flows and intersects the direction D1 in which the exhaust gas flows. The front surface 943b is provided with an introduction port 943d for introducing the exhaust gas into the internal space 943a, and the back surface 943c is provided with an discharge port 943e for discharging the exhaust gas from the internal space 943a.

The housing 943f of the silicon carbide precipitation plate 943 may have the same shape as the silicon carbide precipitation plate 941a, or may have a different shape. In the case of FIG. 9, the housing 943f of the silicon carbide precipitation plate 943 has a cylindrical shape, the front surface 943b and the back surface 943c are circular, the radius of the internal space 943a is R, and the height of the internal space 943a is high. It is H. However, the shape of the housing 943f of the silicon carbide precipitation plate 943 can be arbitrarily changed according to the internal shape of the exhaust gas treatment device. For example, a polygonal prism shape may be used instead of the cylindrical shape.

The size of the introduction port 943d and the discharge port 943e is such that the average particle size (D ₅₀ ) 2r of the carbon particles 10 (where r is the carbon particles) so that the carbon particles 10 can be suppressed from flowing out from the internal space 943a. It is preferably smaller than the radius of 10. In particular, the size of the discharge port 943e is preferably less than the lower limit of the particle size of the carbon particles 10 so that the carbon particles 10 are not discharged from the discharge port 943e together with the exhaust gas.

Further, it is preferable that a plurality of introduction ports 943d and discharge ports 943e are provided so that exhaust gas can be easily introduced and discharged. Further, instead of the circular plate-shaped front surface 943b and back surface 943c provided with the introduction port 943d and the discharge port 943e, the carbon particles 10 are made of open carbon having a size that does not flow out from the internal space 943a. Mesh may be used. Further, if the exhaust gas is introduced and discharged and the outflow of the carbon particles 10 can be prevented, carbon felt may be used instead of the front surface 943b and the back surface 943c.

The exhaust gas treatment device may be provided with an arbitrary number of silicon carbide precipitation plates 943 depending on the installation mode. For example, only one silicon carbide precipitation plate 943 may be provided as in the exhaust gas treatment device 900d shown in FIG. 10 (a), and the silicon carbide precipitation plate 943 may be provided as in the exhaust gas treatment device 900e shown in FIG. 10 (b). You may have more than one.

Further, the silicon carbide precipitation plate 943 is replaceable, and the silicon carbide precipitation plate 943 in which silicon carbide is sufficiently precipitated by the carbon particles 10 can be replaced with a new silicon carbide precipitation plate 943 to continue the treatment of exhaust gas. It is possible.

Further, the silicon carbide precipitation plate 943 may increase or decrease the height H of the internal space 943a. When increasing or decreasing the height H, it is preferably 10 mm or more and 200 mm or less. When a plurality of silicon carbide precipitation plates 943 are provided as in the exhaust gas treatment device 900e shown in FIG. 10B, the total height H of each cylinder is preferably 10 mm or more and 200 mm or less.

If one silicon carbide precipitation plate 943 is used, the total height H of the internal space 943a is used, and if a plurality of silicon carbide precipitation plates 943 are used, the total height H is within the range of 10 mm or more and 200 mm or less. , Silicon carbide can be efficiently deposited on the carbon particles 10 in the internal space 943a. When the height H or the total height H is smaller than 10 mm, the surface area of the carbon particles 10 is not sufficient for the precipitation of silicon carbide, and the precipitation of silicon carbide is insufficient. It is not possible to prevent the chlorosilane polymer from depositing on the exhaust pipe or the like, and it may not be possible to prevent the exhaust pipe or the like from being blocked. When the height H or the total height H is larger than 200 mm, silicon carbide is deposited on the carbon particles 10 upstream in the direction D1 in which the exhaust gas flows, while silicon carbide is deposited on the carbon particles 10 downstream. If it does not precipitate, the carbon particles 10 may not be fully utilized.

(Carbon particles 10)
The average particle size (D ₅₀ ) of the carbon particles 10 is preferably 1 mm or more and 10 mm or less. When the average particle size is 1 mm or more and 10 mm or less, silicon carbide can be efficiently deposited on the carbon particles 10 in the internal space 943a. If the average particle size is smaller than 1 mm, the resistance (fluid resistance) due to the flow of exhaust gas may become too large and the efficiency of precipitation of silicon carbide may decrease. If the average particle size is larger than 10 mm, the carbon particles 10 Since the surface area required for the precipitation of silicon carbide cannot be sufficiently secured as the surface surface, it is not possible to prevent the higher-order chlorosilane polymer from being deposited on the exhaust pipe, etc. due to the insufficient precipitation of silicon carbide, and the exhaust pipe, etc. May not be prevented from being blocked.

Considering that silicon carbide is more efficiently deposited on the carbon particles 10 in the internal space 943a, the average particle size (D ₅₀ ) is 2.0 mm, and the range of D10 to D90 is 0.5 mm to 2.6 mm. It is preferable to use carbon particles 10. Further, considering that the efficiency of precipitation of silicon carbide decreases as the fluid resistance increases, for example, a sieve having a nominal diameter of 10 (ASTM: opening 2 mm) is used to remove carbon particles 10 having a particle size smaller than the average particle size. It is preferable to use carbon particles 10 having a particle size of 2.0 mm to 2.3 mm.

Further, the bulk density of the carbon particles 10, that is, the filling rate of the carbon particles in the internal space 943a is preferably larger than 40% by volume and 60% by volume or less. When the filling rate is larger than 40% by volume and 60% by volume or less, silicon carbide can be efficiently deposited on the carbon particles 10 in the internal space 943a. Considering the precipitation efficiency, when the filling rate is smaller than 40% by volume, the total volume of the gaps between the remaining carbon particles 10 becomes more than 60% by volume with respect to the internal space 943a, and the carbon particles 10 come into contact with each other. Exhaust gas may be discharged from the discharge port 943e, and due to insufficient precipitation of silicon carbide, it is not possible to prevent higher-order chlorosilane polymer from being deposited on the exhaust pipe, etc., and the exhaust pipe, etc. is blocked. It may not be possible to suppress this. Further, when the filling rate is larger than 60% by volume, the fluid resistance may become too large and the efficiency of precipitation of silicon carbide may decrease.

Here, it is preferable that the carbon particles 10 have the same particle size as possible. When the particle sizes of the carbon particles 10 are not uniform, the particle size including the silicon carbide changes due to the precipitation of silicon carbide on the surface of the carbon particles 10, so that the fluid resistance becomes too large or the internal space Carbon particles 10 that are partially unused may occur at 943a. Specifically, if carbon particles 10 having a particle size of 2.0 mm to 2.3 mm are used, it is possible to prevent the fluid resistance from becoming too large, and silicon carbide is applied to the surface of the carbon particles 10 filled in the internal space 943a. It can be deposited efficiently without waste.

The specific surface area (surface area per unit volume) of the carbon particles 10 filled in the internal space 943a sufficient for efficient precipitation of silicon carbide varies depending on the precipitation rate of silicon carbide (consumption rate of chlorine-containing silicon source gas). For example, when the temperature at which silicon carbide is deposited is 1400 K to 1800 K, it can be expected that the film formation rate of silicon carbide will be 50 to 100 μm / hr or more. Here, when the film formation rate of silicon carbide is 50 μm / hr, the consumption of the chlorine-containing silicon source gas corresponds to 4 mol / square meter / hr, and when the film formation rate of silicon carbide is 100 μm / hr. The consumption of chlorine-containing silicon source gas corresponds to 8 mol / square meter / hr. In consideration of the consumption of the chlorine-containing silicon source gas, the carbon particles 10 filled in the internal space 943a have a specific surface area equal to or larger than the specific surface area capable of treating the entire amount of the chlorine-containing silicon source gas contained in the raw material gas. Then, the entire amount of the chlorine-containing silicon source gas can be treated by precipitating silicon carbide. This is because the silicon carbide film is formed in the film forming chamber 100, so that the amount of the chlorine-containing silicon source gas in the exhaust gas is smaller than the amount of the chlorine-containing silicon source gas of the raw material gas.

In the case of the silicon carbide precipitation plate 943 using the carbon particles 10, the precipitation of silicon carbide on the surface of the carbon particles 10 occurs in the region facing the direction D1 in which the exhaust gas flows. For example, as shown in the region 11 of FIG. 10A, on the surface of the carbon particles 10, the precipitation of silicon carbide tends to occur on the upstream half surface facing the direction D1 in which the exhaust gas flows. Considering this, the specific surface area of the carbon particles 10 is preferably twice or more ^{the area (πR 2} ) of the surface 943 g of the internal space 943a of the front surface 943b of the silicon carbide precipitation plate 943.

For example, the radius of the cylindrical internal space 943a of the silicon carbide precipitation plate 943 is R, the height is H, the radius of the carbon particles 10 is r, and the relative bulk density of the carbon particles 10 filled in the internal space 943a is C (0). If <C <1), the number N of the carbon particles 10 filled in the internal space 943a can be calculated by the following formula shown in [Equation 1].

Then, the total surface area (total surface area) of the carbon particles 10 filled in the internal space 943a can be calculated by the following formula shown in [Equation 2].

^{Further, considering that the specific surface area of the carbon particles 10 is preferably twice or more the area (πR 2} ) of the surface 943 g of the internal space 943a of the front surface 943b of the silicon carbide precipitation plate 943, the total surface area is considered. Is ^{preferably 2πR 2} or more. In this case, the radius r of the carbon particles 10 can be calculated by the formula shown in [Equation 4] derived from [Equation 3].

Since the activated carbon or the like that can be used as the carbon particles 10 actually has pores, the actual specific surface area is larger than that calculated based on the particle shape of the carbon particles 10, but the carbon particles 10 The pores disappear due to the formation of silicon carbide on the surface of the material. Therefore, it is more preferable that the specific surface area of the carbon particles 10 is calculated based on the surface area obtained from the particle shape of the carbon particles 10 rather than based on the specific surface area when the carbon particles are used for gas adsorption.

When the silicon carbide precipitation plate 943 is used, silicon carbide may be deposited not only on the surface of the carbon particles 10 but also on the surface of the silicon carbide precipitation plate 943. For example, it is assumed that silicon carbide is deposited on the surface of the front surface 943b.

Each member constituting the exhaust gas treatment device 900 is preferably made of graphite so as to withstand the usage environment. With graphite, it is easy to process the exhaust gas treatment device into an arbitrary shape, and by creating an inert atmosphere during the exhaust gas treatment, it is possible to have sufficient durability under high-temperature film formation conditions. When silicon carbide is sufficiently deposited on the exhaust gas treatment device 900, the exhaust gas treatment device 900 is replaced with a new one to prevent the higher-order chlorosilane polymer from being continuously deposited on the exhaust pipe 350, etc., and the exhaust pipe 350, etc. Can be suppressed from being blocked.

(Other configurations)
The manufacturing apparatus 1000 according to the embodiment of the present invention may have a further configuration in addition to the above configuration. For example, as shown in FIG. 1, the film forming chamber 100 is fixed from the outside of the first surface 110 inside the carbon cylindrical outer cylinder 1100 and the outer cylinder 1100 in which the film forming chamber 100 is inserted. The holding jig 1200 and the outer cylinder 1100 are inserted inside, and the ceramic core tube 1300, the outer cylinder 1100, and the ceramic core tube 1300 that allow an inert gas such as Ar gas to flow between the holding jig 1200 and the outer cylinder 1100. A housing 1500 may be provided in which the fixing flanges 1400 fixed at both ends and the film forming chamber 100 are housed together with the outer cylinder 1100 and the ceramic core tube 1300. Further, although not shown, heat generation of a heater 400, a temperature measuring means such as a thermometer capable of measuring the temperature inside the film forming chamber 100, the temperature of the first surface 100, and the temperature of the mixed gas outlet 200. A control means such as a switch for controlling, a power source for generating heat, and the like can be provided.

[Exhaust gas treatment method]
Next, as an example of the exhaust gas treatment method of the present invention, an exhaust gas treatment method using the manufacturing apparatus 1000 will be described. The exhaust gas treatment method of the present invention includes an exhaust gas introduction step, a molar ratio control step, and a silicon carbide precipitation step described below.

<Exhaust gas introduction process>
In this step, the exhaust gas containing the chlorine-containing silicon source gas discharged from the film forming chamber 100 for forming the silicon carbide polycrystal by chemical vapor deposition is provided with a plurality of silicon carbide precipitation plates, and the room temperature is 1400K to 1800K. This is a step of introducing the gas into the exhaust gas treatment room (in the production apparatus 1000, the exhaust gas treatment apparatus 900).

The exhaust gas includes chlorine-containing silicon source gas and carbon source gas, which are the raw material gases of silicon carbide described below, and rare gases such as argon gas and helium gas, and hydrogen gas, which have a role of transporting these raw material gases. The carrier gas such as, etc. may be contained, and a dopant gas such as nitrogen gas or an argon gas may be appropriately contained.

(Chlorine-containing silicon source gas)
The chlorine-containing silicon source gas is not particularly limited as long as it is used for CVD growth of silicon carbide by a thermal CVD method. For example, examples of the chlorosilane gas include SiH ₃ Cl, SiH ₂ Cl ₂ , SiHCl ₃ , and SiCl ₄ , and one or a mixture of two or more of these can be preferably used. Moreover, not only the monomer of these chlorosilanes but also a dimer gas can be used.

(Carbon source gas)
As the carbon source gas, a known one can be used as in the case of the chlorine-containing silicon source gas, and in general, a hydrocarbon gas can be used. For example, it is a carbon source gas composed of a saturated hydrocarbon having 5 or less carbon atoms or an unsaturated hydrocarbon having 5 or less carbon atoms because it is in a gas state near room temperature and is convenient for handling. However, one or a mixture of two or more of these can be preferably used. In particular, one or more selected from hydrocarbons having 5 or less carbon atoms, methane, ethane, propane, butane and similar hydrocarbon gases can be appropriately used as the carbon source gas. Further, although a gas such as an aromatic hydrocarbon can be used, it should be noted that the decomposition rate is generally slow and carbon aggregates are easily formed. Further, as the carrier gas of the carbon source gas, hydrogen is preferably used because the reaction between the gases can be suppressed.

(Room temperature)
By setting the indoor temperature of the exhaust gas treatment chamber to 1400K to 1800K, the chlorine-containing silicon source gas in the exhaust gas can be effectively converted into silicon carbide. If the room temperature is less than 1400 K, the conversion to silicon carbide becomes insufficient, and higher-order chlorosilanepolymer may be deposited on the exhaust pipe 350 or the like, which may block the exhaust pipe 350 or the like. Further, if the room temperature is higher than 1800 K, the temperature may be higher than the temperature suitable for chemical vapor deposition of silicon carbide, so that the amount of conversion to silicon carbide may decrease. The room temperature of the exhaust gas treatment chamber can be controlled by using the heater 400.

<Mole ratio control process>
This step is a step of controlling the molar ratio C: Si of carbon and silicon in the exhaust gas before coming into contact with the silicon carbide precipitation plate to 1.1 to 2.0: 1. Silicon carbide deposition plate 940a, and 940b, the rate of adsorbing to a solid surface 10, such as carbon particles in the interior of the silicon carbide deposition plate 943, towards the chlorine-containing silicon source gas is earlier than the carbon source gas, particularly CH ₄ gas Has a slow adsorption rate. Therefore, when the amount of carbon in the exhaust gas is larger than the amount of silicon, the amount of silicon carbide produced increases. On the other hand, when the indoor temperature of the exhaust gas treatment chamber is 1000 ° C. (1273.15K) or higher, the vapor pressure of the chlorine-containing silicon source gas cannot be ignored, and the raw material gas composition of the film forming chamber 100 contains chlorine. If the carbon source gas is excessive as compared with the silicon source gas, the carbon amount becomes excessive as the composition ratio of the silicon carbide polycrystal film, so that it is difficult to make the carbon amount excessive in the film forming chamber 100. However, since the chlorine-containing silicon source gas may be converted to silicon carbide in the exhaust gas treatment chamber, the carbon source gas can be made excessive as the gas composition in the exhaust gas as compared with the chlorine-containing silicon source gas.

Therefore, by controlling the molar ratio C: Si of carbon and silicon in the exhaust gas before contacting the silicon carbide precipitation plates 940a, 940b, 943, etc. to 1.1 to 2.0: 1, a chlorine-containing silicon source The gas can be efficiently converted to silicon carbide. When the molar ratio C: Si is <1.1: 1, the adsorption rate on the solid surface is faster for the chlorine-containing silicon source gas than for the carbon source gas, so that the chlorine-containing silicon source gas and the carbon source gas The balance of the amount of gas becomes unbalanced, and there is a possibility that it cannot be efficiently converted to silicon carbide. When the molar ratio C: Si is> 2.0: 1, the concentration of the chlorine-containing silicon source gas in the exhaust gas becomes low, and the chlorine-containing silicon source gas becomes the silicon carbide precipitation plates 940a and 940b and silicon carbide. Since it does not effectively collide with the carbon particles 10 or the like inside the precipitation plate 943, it may not be possible to efficiently convert it into silicon carbide. The molar ratio of carbon to silicon in the exhaust gas, C: Si, can be controlled by using a detecting means for detecting the content of carbon and silicon in the exhaust gas.

In the molar ratio control step, the carbon source gas is mixed so that the molar ratio C: Si of carbon and silicon is 1.1 to 2.0: 1 with respect to the exhaust gas before contacting with the silicon carbide precipitation plate. May be good. If the molar ratio C: Si of carbon to silicon in the exhaust gas discharged from the film forming chamber 100 is 1.1 to 2.0: 1, it is not essential to mix the carbon source gas. However, when the amount of carbon in the exhaust gas is small, for example, the carbon source gas is introduced into the exhaust gas treatment chamber from the carbon source gas introduction pipe 950a, and the carbon in the exhaust gas before contacting the silicon carbide precipitation plates 940a, 940b, 943, etc. The molar ratio of C: Si to silicon can be adjusted to 1.1 to 2.0: 1.
As the carbon source gas, the gas described in the above item of carbon source gas can be used. Further, the carbon source gas before being introduced into the exhaust gas treatment chamber can be warmed so that the indoor temperature of the exhaust gas treatment chamber does not drop to less than 1400 K by introducing the carbon source gas. For example, the carbon source gas can be heated by heating the carbon source gas introduction pipe 950a using the heater 400.

<Silicon carbide precipitation process>
This step is a step of reacting the exhaust gas after the molar ratio control step with a silicon carbide precipitation plate to precipitate silicon carbide. For example, the exhaust gas can be made to collide with the silicon carbide precipitation plates 940a and 940b to deposit silicon carbide on the surfaces of the silicon carbide precipitation plates 940a and 940b. Further, the exhaust gas can be made to collide with the carbon particles 10 inside the silicon carbide precipitation plate 943 to deposit silicon carbide on the surface of the carbon particles 10. As a result of precipitating silicon carbide, it is possible to prevent high-order chlorosilanepolymer from precipitating on the exhaust pipe 350 or the like and prevent the exhaust pipe 350 or the like from being blocked.

(Other processes)
The exhaust gas treatment method of the present invention may include other steps in addition to the above steps. For example, a step of discharging the exhaust gas from the exhaust gas treatment chamber to the exhaust pipe 350 and a step of warming the carbon source gas before introducing the exhaust gas into the exhaust gas treatment chamber can be mentioned.

[Manufacturing method of silicon carbide polycrystalline wafer]
Next, the method for producing the silicon carbide polycrystalline wafer of the present invention will be described. The method for producing a silicon carbide polycrystalline wafer of the present invention includes the exhaust gas treatment method of the present invention. The exhaust gas treatment method is as described above, and the description thereof will be omitted.

The method for producing a silicon carbide polycrystalline wafer of the present invention can include, in addition to the exhaust gas treatment method of the present invention, a step for producing a silicon carbide polycrystalline wafer, such as a film forming step. Hereinafter, as an example of the method for producing a silicon carbide polycrystalline wafer of the present invention, a method for producing a silicon carbide polycrystalline wafer using the manufacturing apparatus 1000 will be described.

(Film formation process)
In the film forming step, in the film forming chamber 100, the substrates 600 are laminated on the substrate holder 500 at equal intervals in a non-contact manner, and the film forming target surface 610 is installed parallel to the side surface 130 with respect to the plurality of substrates 600. , The mixed gas 810 is ejected from the plurality of mixed gas outlets 200 into the film forming chamber 100, the mixed gas 810 is discharged from the film forming chamber 100 from the mixed gas discharge port 300, and the mixed gas 810 is discharged from the film forming target surface 610. This is a step of forming a film on the substrate 600 by circulating in a direction parallel to the above. When the film is formed in this way, it is possible to form a film having little variation in thickness between the substrates or on the same surface to be formed.

Further, the width 700 of the gap between the film-forming target surface 610 and the left side surface 130c of the substrate 600 and the width 710 of the gap between the right side surface 130d are the same as the width 720 of each gap between the substrates 600 laminated at equal intervals. In this case, since the mixed gas flows uniformly through these gaps, it is possible to form a film having less variation in thickness between the substrates or on the same surface to be formed.

For example, as described with reference to FIG. 5, it is preferable that the ejection speed Vg of the mixed gas 810 ejected from the mixed gas ejection port 200 is faster than the diffusion velocity Vd of the mixed gas 810.

In the method for producing a silicon carbide polycrystalline wafer, a chlorine-containing silicon source gas and a carbon source gas, which are raw materials for silicon carbide, serve as a raw material gas, and an argon gas or a helium gas having a role of transporting the raw material gas and these raw material gases. The mixed gas 810 is a mixture of a rare gas such as or a carrier gas such as hydrogen gas. The mixed gas 810 may further contain a dopant gas such as nitrogen gas or an argon gas as appropriate. The chlorine-containing silicon source gas, carbon source gas, carrier gas, etc. are the same as those described in the exhaust gas treatment method, and thus the description thereof will be omitted here.

Further, when forming a silicon carbide polycrystal film, the ratio of the number of carbon atoms in the carbon source gas to the number of silicon atoms in the chlorine-containing silicon source gas (C / Si) is important, and C / Si is set to 0. By controlling the ratio to 7 to 1.3, it becomes easy to epitaxially grow a thin film of silicon carbide polycrystal on the substrate 600, the growth rate can be increased, and the productivity is improved. When C / Si deviates from 0.7 to 1.3, the balance of the abundance ratios of silicon atoms and carbon atoms becomes poor, which may make it difficult to form silicon carbide polycrystals or form a film. The speed may slow down, and the amount of raw material gas that is not involved in film formation may increase and be wasted. For example, if C / Si is less than 0.7, unreacted Si may adhere to the film (droplet) in a metallic state, which causes defects. Further, if C / Si exceeds 1.3, a surface step called bunching may occur, which may adversely affect the fabrication of the device. More preferably, C / Si is 0.8 to 1.2.

The growth rate of the silicon carbide polycrystalline thin film is preferably 10 μm / hour to 70 μm / hour, and the chlorine-containing silicon source gas at that time is the concentration of the chlorine-containing silicon source gas mentioned above as a suitable example. Is preferably 1% by volume to 10% by volume, preferably 2% by volume to 4% by volume. On the other hand, for the carbon source gas, the concentration of the carbon source gas mentioned as a preferable example is preferably 0.01% by volume to 1% by volume or less, preferably 0.02% by volume to 0.06. It should be% by volume. In addition, this concentration range is an example of the case of C ₃ H ₈ as an example, and when another carbon source gas is used with this concentration range as a guide, the amount of carbon (C) is equal to the amount. It should be changed so as to be. For example, when methane (CH ₄ ) is used as the carbon source gas, the upper limit value and the lower limit value of this concentration range may be tripled, respectively.

As for the growth pressure of the silicon carbide polycrystalline thin film, the general conditions for CVD growth of the silicon carbide thin film can be adopted as they are, as with the growth temperature. For example, the growth pressure is preferably in the range of 10,000 Pa to 110,000 Pa.

Further, in the method for producing a silicon carbide polycrystalline wafer of the present invention, a plurality of Si substrates or C substrates can be used as a substrate 600, and a silicon carbide polycrystalline thin film can be grown on each of the film formation target surfaces 610. The number of substrates 600 in one film forming process is not particularly limited, but it is possible to simultaneously form a film from 5 to 10 substrates to 20 to 30 or more substrates 600.

The film thickness of the silicon carbide polycrystalline thin film to be grown on each surface of the substrate 600 can be appropriately set and is not particularly limited, but is generally in the range of 0.2 mm or more and 5 mm or less. Can be set to.

Further, in the method for producing a silicon carbide polycrystalline wafer of the present invention, the growth temperature at the time of forming a CVD film of the silicon carbide polycrystalline thin film is preferably in the range of 1400 K or more and 1800 K or less. The main object of the present invention is to produce a silicon carbide polycrystalline wafer having a crystal system of 3C. Generally, when the growth temperature is higher than 1800K, epitaxial growth may occur in the film formation of silicon carbide, and the crystal system is 4H. Hexagonal crystals may be formed together with 3C. Further, if the growth temperature is lower than 1400 K, the growth rate of silicon carbide becomes slow, and there is a possibility that the conditions are not suitable for forming a thick film. In the film formation of silicon carbide, the growth rate increases as the temperature rises. Therefore, the growth temperature is 1400 K or more as described above so that silicon carbide polycrystals having a crystal system of 3C can be formed at high speed (10 μm / Hr or more). The range should be 1800K or less.

(Other processes)
The method for producing a silicon carbide polycrystalline wafer of the present invention can include other steps in addition to the above-mentioned film forming step and exhaust gas treatment method. For example, a step of stacking the substrates 600 on the substrate holder 500 at equal intervals in a non-contact manner and installing the substrate 600 on the substrate holder 500, or a step of installing the substrate holder 500 on which the substrate 600 is installed in the film forming chamber 100. Examples thereof include a step of raising the manufacturing apparatus 1000 into a state in which a film can be formed, a step of cooling the film forming chamber 100 after the film forming step, a step of taking out the substrate after the film formation from the film forming chamber 100, and the like.

[Example]
Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. The present invention is not limited to the following contents.

[Example 1]
As the substrate 600, nine carbon substrates having a diameter of 4 inches (100 mm) and a thickness of 1 mm were prepared. Using the silicon carbide polycrystalline wafer manufacturing apparatus 1000 shown in FIG. 1, a silicon carbide polycrystalline film is formed on both sides of the substrate 600 to be a film-forming target surface 610 by a thermal CVD method to obtain a silicon carbide polycrystalline wafer. Manufactured. After manufacturing the silicon carbide polycrystalline wafer, observe the inside of the exhaust pipe 350 arranged downstream of the exhaust gas treatment device 900, and observe the inside of the exhaust pipe 350, and the presence or absence of deposits due to the chlorine-containing silicon source gas in the exhaust gas such as high-order chlorosilane polymer. It was confirmed.

<Silicon Carbide Polycrystalline Wafer Manufacturing Equipment 1000>
The outer cylinder 1100 has a tubular shape formed from graphite crucibles at both ends, and is inserted into a ceramic core tube 1300. Both ends of the ceramic core tube 1300 and the outer cylinder 1100 are sealed with a metal fixing flange 1400, and Ar gas is introduced inside to prevent oxidation of the graphite material. Then, the film forming chamber 100 is fixed to the inside of the outer cylinder 1100 by the holding jig 1200. The graphite mixed gas introduction pipe 210 is inserted and installed in the holding jig 1200 and the first surface 100 so that the mixed gas ejection port 200 is located inside the film forming chamber 100. Then, the mixed gas discharge pipe 310 made of graphite is inserted and installed on the second surface 120 so that the mixed gas discharge port 300 is located inside the film forming chamber 100. The exhaust gas discharged from the film forming chamber 100 is introduced into the housing 910a from the exhaust gas introduction port 920a via the mixed gas discharge pipe 310, and from the inside of the housing 910a to the exhaust pipe 350 via the exhaust gas discharge port 930a. It is discharged. Further, a cylindrical graphite heater 400 surrounding the ceramic core tube 1300 is installed, and a housing 1500 for accommodating the film forming chamber 100 and the exhaust gas treatment device 900a together with the outer cylinder 1100 and the ceramic core tube 1300. To be equipped with. Then, the mixed gas 810 supplied to the film forming chamber 100 can be discharged to the outside from the manufacturing apparatus 1000 by using a vacuum pump (not shown) connected to the exhaust pipe 350.

In the manufacturing apparatus 1000, the ceramic core tube 1300 has an outer diameter of 210 mm, an inner diameter of 190 mm, a uniform thickness, and a length of 700 mm. The outer cylinder 1100 has an outer diameter of 180 mm, an inner diameter of 170 mm, a uniform thickness, and a length of 700 mm. The film forming chamber 100 has a rectangular parallelepiped shape having an outer shape of 118 mm square and a length of 320 mm, an inner shape of 110 mm square and a length of 312 mm, and has a uniform thickness.

(Gas outlet 200)
As shown in FIG. 2, four mixed gas outlets 200 having an inner diameter of 12 mm are arranged in a row on the first surface 110. The four mixed gas outlets 200 are arranged at equal intervals of 22 mm at the center of the pipe. Further, the row of the mixed gas ejection ports 200 is arranged at the center of the first surface 110 in the width direction (direction orthogonal to the row).

(Exhaust gas treatment device 900a)
In Example 1, the graphite exhaust gas treatment device 900a shown in FIG. 6A was used as the exhaust gas treatment device. The exhaust gas treatment device 900a has a rectangular parallelepiped shape in which the outer shape of the housing 910a is 118 mm square and 320 mm in length, and the inner shape is 110 mm square and 312 mm in length, and the thickness is uniform. Further, three plate-shaped silicon carbide precipitation plates 941a installed in parallel in the center of the inside of the housing 910a at equal intervals are 110 mm in length and 90 mm in width, and have a uniform thickness of 4 mm. The plate-shaped silicon carbide precipitation plate 942a formed at equal intervals so as to project from the inner wall of the housing 910a and arranged between the silicon carbide precipitation plates 941a has a length of 110 mm, a width of 45 mm, and a thickness of 4 mm. Is uniform. The opening diameters of the exhaust gas introduction port 920a and the exhaust gas discharge port 930a are 56 mm, which are the same as the inner diameters of the mixed gas discharge pipe 310 and the exhaust pipe 350. The inner diameter of the carbon source gas introduction pipe 950a was set to 10 mm.

(Installation of board 600)
As shown in FIG. 4, nine substrates 600 were installed in the substrate holder 500. The substrate 600 was installed in the film forming chamber 100 in a state of being fixed to the substrate holder 500 by the grooves 511 and 521. As shown in FIG. 4B, the upper holding rod 510 of the substrate holder 500 is brought into close contact with the upper side surface 130a so that the mixed gas 810 does not enter between the upper holding rod 510 and the lower holding rod 520. The mixed gas 810 was brought into close contact with the lower side surface 130b so as not to enter the lower side surface 130b. The width of the gap 700 between the film-forming target surface 610 and the left side surface 130c of the substrate 600, the width 710 of the gap between the right side surface 130d, and the width 720 of each gap between the substrates 600 laminated at equal intervals are the same. It was set to 10 mm. The shortest distance between the mixed gas ejection port 200 and the substrate holder 500 was set to 150 mm.

(Silicon carbide polycrystalline film formation)
Ar gas was flowed between the outer cylinder 1100 and the ceramic core tube 1300 and in the housing 1500 in order to prevent oxidation of the graphite material. Then, after the inside of the film forming chamber 100 is evacuated by a vacuum pump (not shown), the film forming chamber 100 is introduced into the film forming chamber 100 at a flow rate of ^{200 cm 3 / min using a mixed gas introduction pipe 210.} The pressure inside was adjusted to atmospheric pressure (101,325 Pa). After that, the temperature inside the film forming chamber 100 was raised to 1550 K while maintaining the temperature of the first surface 110 at 1100 K or less and the temperature of the mixed gas ejection port 200 at 1200 K or less while keeping the pressure constant. Then, the flow rate of the hydrogen gas introduced into the film forming chamber 100 was increased to 3.0 liters per minute. After holding that state for 3 minutes, SiC ₄ gas is added to this hydrogen gas at 0.3 liters per minute, CH ₄ gas is added at 0.3 liters per minute, nitrogen gas is added at 1.0 liters per minute, and hydrogen gas is added every minute. 1.0 liter was mixed to obtain a mixed gas 810, and a film of a silicon carbide polycrystal film was started on the substrate 600 by thermal CVD in a state of Vg> Vd.

_{The raw material gas SiCl 4} is introduced at 0.3 liter / min, where the film formation temperature and the exhaust gas treatment temperature, that is, the internal temperature of the exhaust gas treatment device 900a are set to 1700 K, and the gas treatment efficiency of the exhaust gas is 8 mol / square meter / hr. Therefore, the amount of chlorine-containing silicon source gas introduced was 0.8 mol / hr. The area of the silicon carbide precipitation plate 941a and the silicon carbide precipitation plate 942a required for the treatment of the exhaust gas was 0.1 square meter. Further, the exhaust gas treatment device 900a is provided from the carbon source gas introduction pipe 950a so that the molar ratio C: Si of carbon and silicon in the exhaust gas in contact with the silicon carbide precipitation plate 941a and the silicon carbide precipitation plate 942a is 1.33: 1. CH ₄ gas was introduced into 0.1 liter / min. CH ₄ gas introduced into the exhaust gas treatment apparatus 900a than the carbon source gas inlet pipe 950a is a 100% pure CH ₄ gas, the carrier gas was not used.

After performing the film forming treatment for 10 hours, the supply of the mixed gas 810 and the heating by the heater 400 were stopped to cool the substrate 600 to room temperature, and then the substrate 600 on which the silicon carbide polycrystalline film was formed was taken out from the substrate holder 500. Silicon carbide was formed normally, and there was no problem in forming the film. Further, when the inside of the exhaust pipe 350 after the film formation was observed and the presence or absence of deposits due to the chlorine-containing silicon source gas in the exhaust gas such as high-order chlorosilane polymer was confirmed, it was caused by the chlorine-containing silicon source gas. There were no deposits. Due to the excess amount of carbon source gas, a small amount of soot, which is a decomposition product of carbon source gas, adhered to the inside of the exhaust pipe 350. There wasn't.

[Example 2]
Other than using the exhaust gas treatment device 900d instead of the exhaust gas treatment device 900a, the silicon carbide polycrystalline wafer manufacturing device 1000 is used in the same manner as in Example 1, and the film formation process is performed under the same method and conditions to form a film. The inside of the exhaust pipe 350 was observed later.

(Exhaust gas treatment device 900d)
In Example 2, the graphite exhaust gas treatment device 900d shown in FIG. 10A was used as the exhaust gas treatment device. The exhaust gas treatment device 900d has a cylindrical shape with an outer diameter of 176 mm and a length of 320 mm, and a cylindrical shape with an inner diameter of 168 mm and a length of 312 mm, and has a uniform thickness. The silicon carbide precipitation plate 943 is closely fixed to the inner wall of the housing 910a, and the outer diameter of the housing 943f is 168 mm and the height is 58 mm, and the radius R of the internal space 943a is 80 mm and the height is 50 mm. Activated carbon (Spherical Shirasagi X7000H-3 (particle size 0.5000 to 2.360 mm) manufactured by Osaka Gas Co., Ltd.) was used as the carbon particles 10 in the internal space 943a. The activated carbon had a particle size of 2.3 mm and was filled in the internal space 943a. Assuming that the filling rate of the activated carbon is 50% by volume, the total surface area of the charged activated carbon is 3.15 m ² , and the area of the front surface 943 b (0.08 m × 0.08 m × π = 0.2 m ² ). The specific surface area of the carbon particles 10 is sufficiently larger than the area of the front surface 943b. The introduction port 943d and the discharge port 943e are circular and have a diameter of less than 0.5 mm so that activated carbon cannot pass through.

The opening diameters of the exhaust gas introduction port 920a and the exhaust gas discharge port 930a are 56 mm, which are the same as the inner diameters of the mixed gas discharge pipe 310 and the exhaust pipe 350. The inner diameter of the carbon source gas introduction pipe 950a was set to 10 mm.

After the film was formed for 10 hours, the supply of the mixed gas 810 and the heating by the heater 400 were stopped to cool the substrate 600 to room temperature, and then the substrate 600 on which the silicon carbide polycrystalline film was formed was taken out from the substrate holder 500. Silicon carbide was formed normally, and there was no problem in forming the film. Further, when the inside of the exhaust pipe 350 after the film formation was observed and the presence or absence of deposits due to the chlorine-containing silicon source gas in the exhaust gas such as high-order chlorosilane polymer was confirmed, it was caused by the chlorine-containing silicon source gas. There were no deposits.

[Comparative Example 1]
_{The amount of SiCl 4} gas introduced into the raw material gas is 0.4 liters per minute, and the film is formed by the same method as in Example 1 except that _{CH 4} gas is not introduced into the exhaust gas treatment device 900a from the carbon source gas introduction pipe 950a. After the treatment, the inside of the exhaust pipe 350 after the film formation was observed. The molar ratio C: Si of carbon to silicon in the exhaust gas in contact with the silicon carbide precipitation plate 941a and the silicon carbide precipitation plate 942a was 1: 1. Although the silicon carbide was formed normally and there was no problem in the film formation, about 50 g of deposits due to the chlorine-containing silicon source gas as a raw material adhered to the inside of the exhaust pipe 350. No soot adhered to the inside of the exhaust pipe 350.

[Comparative Example 2]
_{The amount of SiCl 4} gas introduced into the raw material gas is 0.4 liters per minute, and the film is formed by the same method as in Example 2 except that _{CH 4} gas is not introduced into the exhaust gas treatment device 900d from the carbon source gas introduction pipe 950a. After the treatment, the inside of the exhaust pipe 350 after the film formation was observed. The molar ratio C: Si of carbon to silicon in the exhaust gas in contact with the carbon particles 10 was 1: 1. Although the silicon carbide was formed normally and there was no problem in the film formation, about 2 g of deposits due to the chlorine-containing silicon source gas as a raw material adhered to the inside of the exhaust pipe 350. No soot adhered to the inside of the exhaust pipe 350.

[Conventional example]
A silicon carbide polycrystalline wafer manufacturing device 3000 (FIG. 8) having the same configuration as the manufacturing device 1000, except that the exhaust gas treatment device 900 is not provided and the exhaust gas is discharged to the outside of the manufacturing device from the mixed gas discharge pipe 310 (FIG. 8). Was used to perform a film forming process under the same conditions as in the examples, and the inside of the mixed gas exhaust pipe 310 after the film formation was observed. Although silicon carbide was normally formed and there was no problem in forming the film, about 110 g of deposits due to the chlorine-containing silicon source gas as a raw material adhered to the inside of the mixed gas discharge pipe 310. In addition, a large amount of soot was also observed inside the exhaust pipe 350.

[Summary]
As described above, as shown in the examples, according to the exhaust gas treatment method and the method for producing a silicon carbide polycrystalline wafer of the present invention, the high-order chlorosilane polymer can be used for exhaust piping and the like while producing the silicon carbide polycrystalline wafer without any problem. It was confirmed that it was possible to prevent the precipitation in the air and suppress the blockage of the exhaust pipe and the like.

10 Carbon particles 11 Region 100 Formation chamber 110 1st surface 120 2nd surface 130 Side surface 130a Upper side 130b Lower side 130c Left side 130d Right side 200 Mixed gas outlet 210 Mixed gas introduction pipe 300 Mixed gas exhaust port 310 Mixed gas exhaust Pipe 350 Exhaust pipe 400 Heater 500 Board holder 510 Upper holding rod 511 Groove 520 Lower holding rod 521 Groove 600 Substrate 610 Film formation target surface 800 Mixed gas 810 Mixed gas 900 Exhaust gas treatment device 900a Exhaust gas treatment device 900b Exhaust gas treatment device 900c Exhaust gas treatment device 900d Exhaust gas treatment device 900e Exhaust gas treatment device 910a Housing 920a Exhaust gas introduction port 930a Exhaust gas discharge port 940a Silicon carbide precipitation plate 940b Silicon carbide precipitation plate 941a Silicon carbide precipitation plate 941b Silicon carbide precipitation plate 942a Silicon carbide precipitation plate 942b Silicon carbide precipitation plate 943 Silicon carbide deposit plate 943a Internal space 943b Front surface 943c Back surface 943a Internal space 943d Introduction port 943c Back surface 943a Internal space 943e Exhaust port 943f Housing 943g Surface 950a Carbon source gas introduction pipe 960 Space 970a Wall 970a 980b Passage port 1000 Manufacturing equipment 1100 Outer cylinder 1200 Holding jig 1300 Ceramic core tube 1400 Fixed flange 1500 Housing 2000 Manufacturing equipment 3000 Manufacturing equipment D1 direction H Height R Radiation Vg Ejection speed Vd Diffusion speed

Claims (6)

Exhaust gas containing a chlorine-containing silicon source gas discharged from a film forming chamber for forming silicon carbide polycrystals by chemical vapor deposition is introduced into an exhaust gas treatment chamber having a silicon carbide precipitation plate and having a room temperature of 1400K to 1800K. Exhaust gas introduction process and
A molar ratio control step of controlling the molar ratio C: Si of carbon and silicon in the exhaust gas in contact with the silicon carbide precipitation plate to 1.1 to 2.0: 1.
A silicon carbide precipitation step of reacting the exhaust gas after the molar ratio control step with the silicon carbide precipitation plate to precipitate silicon carbide.
Exhaust gas treatment method including. The exhaust gas treatment method according to claim 1, wherein the silicon carbide precipitation step is a step of causing the exhaust gas to collide with the silicon carbide precipitation plate to precipitate silicon carbide on the surface of the silicon carbide precipitation plate. The silicon carbide precipitation plate is
A hollow interior space filled with carbon particles,
A front surface that is upstream of the internal space in the direction in which the exhaust gas circulates and intersects the direction in which the exhaust gas circulates.
A back surface that is downstream of the internal space in the direction in which the exhaust gas circulates and intersects the direction in which the exhaust gas circulates.
An introduction port provided on the front surface for introducing the exhaust gas into the internal space,
A discharge port provided on the back surface for discharging the exhaust gas from the internal space is provided.
The exhaust gas treatment method according to claim 1, wherein the silicon carbide precipitation step is a step of causing the exhaust gas to collide with the carbon particles to precipitate silicon carbide on the surface of the carbon particles. The exhaust gas treatment method according to claim 3, wherein the specific surface area of the carbon particles is at least twice the area of the front surface. In the molar ratio control step, the carbon source gas is added so that the molar ratio C: Si of carbon to silicon is 1.1 to 2.0: 1 with respect to the exhaust gas before contacting with the silicon carbide precipitation plate. The exhaust gas treatment method according to any one of claims 1 to 4, wherein the mixture is mixed. A method for producing a silicon carbide polycrystalline wafer, which comprises the exhaust gas treatment method according to any one of claims 1 to 5.

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