JP4463541B2 - SEALING AGENT, METHOD OF JOINING REACTION CONTAINER USING THE SEALING AGENT, REACTION CONTAINER - Google Patents

Description

The present invention relates to a sealing agent that joins a joining portion of a carbon container for silicon production, a reaction container joining method using the sealing agent, and a reaction container.
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  It is known that polycrystalline silicon is produced by precipitation from source gases such as chlorosilanes and hydrogen.

  In this production method, a reaction vessel made of a carbon material is used as a reaction vessel because it comes into contact with chlorosilanes or a silicon melt, from the viewpoint of high temperature resistance, chemical resistance, and contamination of impurities.

  In view of the purity of the product, it is the best method to use a monolith without a joint as the reaction vessel. However, the carbon material has characteristics that it is brittle and difficult to process. Further, in order to form an integral product, a large frame mold is required, so that it is difficult to directly produce a large reaction vessel.

  For this reason, for example, a plurality of short cylindrical parts are stacked into a straight cylinder, or a plurality of rectangular plate-like parts circulate around the circumference to form a cylindrical shape. As a result, a reaction vessel was constructed.

  However, when silicon becomes a molten liquid, it is highly permeable and leaks from the gaps between the parts, reducing the reaction efficiency and coming into contact with the leaked molten silicon. The gas supply pipe, its cooling means, heat insulating material, etc. may be damaged.

  In addition, there is a problem that silicon is solidified in the joint portion, and as a result, the joint portion is damaged.

  For this reason, there is a problem that long-term continuous operation cannot be performed if silicon leaks. Moreover, in such a case, it will be necessary to stop production and inspect equipment.

  Furthermore, in terms of the purity of the product, when the leaked silicon enters the reactor system again, the purity of the product in contact with the outer wall of the reactor, the heating means, the source gas supply pipe and its cooling means, the heat insulating material, etc. Inferior silicon precipitates sometimes contaminate high purity polycrystalline silicon.

  For these reasons, it has been an object to develop a method for suppressing leakage of molten silicon.

  As a result of intensive studies to solve the above problems, the present inventors have found that if the sealing part containing a material that is difficult to wet with respect to the silicon melt is filled in the joint portion of the carbon container, the silicon melt enters and leaks. I found that there was nothing to do.

That is, the present invention is characterized in that a sealing agent containing a ceramic material powder having a contact angle with a silicon melt of 45 ° or more is used for joining the reaction vessels . A ceramic material having such a contact angle has liquid repellency with respect to the silicon melt, so that silicon does not enter.

As such a ceramic material, at least one selected from boron nitride, silicon nitride, aluminum nitride and silica is preferable. Since these ceramic materials do not dissolve in silicon, they do not contaminate the generated silicon.

A reaction vessel bonding method according to the present invention is a method for bonding a bonding portion of a carbon reaction vessel for obtaining silicon as a melt from a silicon source gas containing chlorosilanes and hydrogen in a heated reaction vessel. ,
The sealing agent is used for joining the joint portion of the reaction vessel that comes into contact with the silicon melt.

  In addition, the carbon reaction container according to the present invention is characterized in that the parts are joined to each other by filling the sealant in the gap between the joints constituted by a plurality of parts. The effect of the present invention is particularly manifested when the joint portion of the reaction vessel has a screw shape.

  In JP-A-2002-321037, in a silicon casting method in which a silicon melt is poured into a mold and solidified, a mold release agent containing silicon nitride, silicon carbide, and silicon oxide is applied to the inner surface of the mold. It is disclosed. That is, in the method disclosed in this publication, silicon nitride or the like is used as a mold release agent for a silicon ingot. However, there is no disclosure of a sealing agent as in the present invention.

  According to the present invention, the joint between the parts constituting the carbon-made reaction vessel for silicon production is joined with the specific sealant. For this reason, when manufacturing polycrystalline silicon, a silicon melt and source gas are repelled by a junction and do not enter.

  Therefore, when such a reaction vessel is used, a long-time precipitation reaction operation becomes possible. In addition, since the sealing agent is difficult to elute into polycrystalline silicon, it is possible to obtain silicon that is very excellent in terms of purity.

A reaction vessel bonding method according to the present invention is a method for bonding a bonding portion of a carbon reaction vessel for obtaining silicon as a melt from a silicon source gas containing chlorosilanes and hydrogen in a heated reaction vessel. ,
The sealing agent is used for joining the joint portion of the reaction vessel that comes into contact with the silicon melt.

  Hereinafter, embodiments of the present invention will be specifically described.

Sealant The sealant according to the present invention contains a powder of a ceramic material having liquid repellency (resistance to wettability) with respect to a silicon melt.

  In the present invention, a ceramic material having such a contact angle of 45 ° or more, preferably 90 ° or more is used.

  As for the contact angle, a flat plate made of ceramic used as a sealant is placed in a sealed chamber, and is replaced with internal argon gas and heated to 1450 ° C. The contact angle of the silicon droplet is measured from above the plate through the observation window.

  When the joint portion of the reaction vessel is used by using the powder of the material having such a contact angle as a sealant, the silicon melt can be effectively repelled, so that silicon does not enter the joint portion. These ceramic materials can also make it difficult for silicon deposition source gases (chlorosilanes) to enter the joint.

The ceramic material having such a contact angle is preferably at least one ceramic material selected from boron nitride, silicon nitride, aluminum nitride, and silica. These may be used as a mixture of two or more kinds, or may be a composite of two or more kinds of ceramics. These have high liquid repellency with respect to a silicon melt, and do not mix as impurities in the deposited high purity silicon when silicon is produced. When two or more kinds are mixed or used in combination, the contact angle of the mixture / composite is preferably within the above range.

  The average particle size of the ceramic material powder is appropriately selected according to the size of the gap between the joints, but usually the one in the range of 0.001 to 200 μm, preferably 0.005 to 150 μm is used.

  In the present invention, the average particle size is measured with a Coulter counter (product surface: manufactured by Coulter Electronics Co., Ltd.).

  When silicon nitride powder is used as a sealant, the average particle size of the silicon nitride powder is desirably in the range of 0.5 to 100 μm, preferably in the range of 1 to 50 μm.

  Moreover, when using silica powder as a sealing agent, it is desirable to be in the range of 0.001 to 0.1 μm, preferably 0.003 to 0.03 μm.

  Moreover, when using silicon nitride powder, it is preferable to use it mixed with silica fine particles. When used in combination with silica fine particles, the silica fine particles melt and function as a binder, and the silicon nitride powder is held together, so that the filling efficiency of silicon nitride is increased and the gaps in the sealant can be filled. For this reason, it can suppress effectively that molten silicon and its reaction material leak from a junction part. Further, since the silicon nitride powder is fixed with silica, the silicon nitride powder is not detached from the sealed joint into the reaction vessel.

  The sealing agent according to the present invention is used by spraying the ceramic powder as it is on the seal portion.

  Further, if necessary, the ceramic powder may be dispersed in a solvent and pasted into a joint, or may be applied in a liquid form and sprayed.

  The solvent is not particularly limited as long as the ceramic powder does not react and easily volatilizes when filled with a sealant. Specific examples include water, alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and phenols such as phenol and cresol.

As the dispersant, known ones can be used without particular limitation. Specifically, polyvinyl alcohol, cellulose, and the like that easily decompose and evaporate with heat during silicon production are suitable.

  In the case of dispersing in a solvent (including paste form), the solid content concentration is not particularly limited as long as it can be handled as a liquid or a paste.

Joining method The joining method of the reaction container according to the present invention uses the sealing agent for joining the joint part of the reaction container that comes into contact with the silicon melt.

  Specifically, in the present invention, as shown in FIGS. 1 to 4, the parts are joined to each other by filling the gap or groove in the joint between the parts of the reaction vessel with the sealing agent. 1-4, reference numeral 1 denotes a part, 2 denotes a gap, and 3 denotes a sealant.

  The method for filling the sealing agent is not particularly limited, and a known method can be adopted.

  In the case of a powdery sealant, a known method such as an air blowing method is employed. In the case of a paste-like / liquid sealing agent, a known coating method such as a brush coating method or a dipping method is employed. Further, after the application, heat treatment may be performed to remove the solvent / dispersant.

  The filling amount of the sealing agent is not particularly limited, and the sealing property against the silicon melt can be sufficiently maintained even if the sealing agent powder is sandwiched between the joint portions.

Reaction vessel The shape of the reaction vessel according to the present invention is not particularly limited as long as it is composed of a plurality of parts and joined with the sealing agent.

  FIG. 5 and FIG. 6 are partial oblique views showing a typical embodiment of the reaction vessel used in the present invention.

The reaction vessel shown in FIG. 5 is a reactor formed by arranging rectangular plate-like parts 1 in the longitudinal direction. Moreover, the reaction container shown by FIG. 6 is a reaction container formed by arranging the parts divided into cylindrical shapes in the longitudinal direction. Note that the cylindrical part shown in FIG. 6 may be divided in the circumferential direction. (That is, it may be divided in the longitudinal direction)
The material of the part 1 constituting the reaction vessel is not particularly limited as long as it is for carrying out a reaction for depositing high-purity silicon therein, but a material made of a carbon material is usually used.

  In addition to the plate-shaped and cylindrical parts described above, various parts can be combined according to the shape of the reaction vessel.

For example, an octagonal columnar reaction vessel in which eight rectangular plate-like parts shown in FIG. 5 are joined may be mentioned. If six rectangular plate parts are joined, a hexagonal column shaped reaction vessel is formed. Further, if the number of plate-like parts is increased, it can be made closer to a cylindrical shape.

  Furthermore, if trapezoidal plate-shaped parts are used instead of rectangular plate-shaped parts, an octagonal pyramid-shaped reaction vessel can be formed as shown in FIG.

Further, as shown in FIG. 8, when the rectangular parts are provided with joints in the longitudinal direction and the longitudinal direction is formed of a plurality of rectangles, a reaction vessel extending in the longitudinal direction can be produced.

  Examples of the shape of the joint between the parts include a fitting shape (FIG. 1), a fitting shape (FIG. 2), a screw shape (FIGS. 3 and 4), etc. as shown in FIGS. There is no particular limitation.

  In the present invention, the sealant is filled in the gaps between the parts. Moreover, you may form the groove | channel for sealing agent filling by notching a part of one or both end surfaces of the parts 1 joined by a junction part.

  Moreover, as long as the sealing effect with respect to source gas and a silicon melt can be expressed, it is not limited to joining of carbon members. Therefore, the sealing agent according to the present invention may be used when joining a reaction vessel composed of a carbon member and another member.

  Examples of the other members include members made of silicon nitride, aluminum nitride, silicon carbide, alumina, and the like.

According to this invention, it consists of parts divided | segmented into plurality, and the junction part between these parts is joined by the specific sealing agent. For this reason, when it uses for manufacture of a polycrystalline silicon, a silicon melt is repelled by a junction part and does not enter. For this reason, the reaction efficiency does not decrease, and the leaked molten silicon does not come into contact with the outer wall of the reaction apparatus, the heating means, the source gas supply pipe, its cooling means, the heat insulating material, or the like. Further, since the silicon does not solidify in the joint portion, the joint portion is not damaged. For this reason, high purity silicon can be deposited stably for a long period of time.
[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

Examples 1-6, Comparative Examples 1-3
A sealing agent made of the following material was filled into a screw-like joint portion of a carbon tubular reaction vessel that was divided into a cylindrical shape in the length direction and could be joined in a screw shape. The sealing agent was filled by (powder spraying). After filling the sealant, the reaction vessel was joined. (In Comparative Example 3, the reaction vessel was fitted as it was without using a sealant.

The bonded reaction vessel is attached to the polycrystalline silicon manufacturing apparatus, a mixed gas (raw material gas) of trichlorosilane and hydrogen is circulated inside the reaction vessel, and the reaction vessel is heated to 1450 ° C. or higher by external heating means. Polycrystalline silicon was deposited for 100 hours. After the reaction, the reaction vessel was taken out from the reaction apparatus, and the presence or absence of silicon leakage at the joint was confirmed.

  The results are shown in Table 1.

Example 7
The reaction vessel was joined in the same manner as in Examples 1 to 6 except that the mixed powder shown in Table 2 was used as the sealant, and the presence or absence of silicon leakage was confirmed.

  The results are shown in Table 2.

Schematic which shows the principal part of the seal part of this invention. Schematic which shows the principal part of the seal part of this invention. Schematic which shows the principal part of the seal part of this invention. Schematic which shows the principal part of the seal part of this invention. The perspective view which shows the typical aspect of the reaction container of this invention. The perspective view which shows the typical aspect of the reaction container of this invention. The perspective view which shows the typical aspect of the reaction container of this invention. The perspective view which shows the typical aspect of the reaction container of this invention.

Explanation of symbols

1 Parts 2 Gap 3 Joint (sealant)

Claims (6)

In a heated reaction vessel, a method of joining a carbon reaction vessel junction for obtaining silicon as a melt from a silicon source gas containing chlorosilanes and hydrogen,
A method for joining reaction vessels, wherein a sealing agent containing a ceramic material powder having a contact angle with a silicon melt of 45 ° or more is used for joining a joint portion of a reaction vessel that comes into contact with a silicon melt.   The bonding method according to claim 1, wherein the ceramic material is at least one selected from boron nitride, silicon nitride, aluminum nitride, and silica.   The joining method according to claim 1 or 2, wherein the joining portion of the reaction vessel has a screw shape.   Filling the gap between the joints composed of multiple parts with a sealant containing a ceramic material powder having a contact angle with the silicon melt of 45 ° or more, the parts are joined to each other. Characteristic carbon reaction vessel.   5. The carbon reaction vessel according to claim 4, wherein the ceramic material is at least one selected from boron nitride, silicon nitride, aluminum nitride, and silica. The carbon reaction container according to claim 4 or 5 , wherein each part has a cylindrical shape, and a joint portion thereof has a screw shape.

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