JP6119586B2 - Method for manufacturing silicon carbide-coated graphite member, silicon carbide-coated graphite member, and method for manufacturing silicon crystal - Google Patents

Description

  The present invention relates to a method for producing a silicon carbide-coated graphite member used in a silicon crystal production apparatus or the like, a silicon carbide-coated graphite member produced thereby, and a method for producing a silicon crystal using the same.

Many graphite parts are used in the silicon crystal manufacturing apparatus. During the operation of silicon crystal production, SiO gas and Si vapor are generated from the Si (silicon) melt held in the quartz crucible. The generated SiO gas and Si vapor move according to the gas flow in the silicon crystal production apparatus, and the graphite parts are reacted by the following reaction formulas (1) and (2) on the surface of the graphite part at the high temperature part in the silicon crystal production apparatus. The surface is converted into a rough SiC (silicon carbide) layer. In the formula, (g) represents gas and (s) represents solid.
SiO (g) + 2C (s) → SiC (s) + CO (g) (1)
Si (g) + C (s) → SiC (s) (2)

The SiC layer formed by converting the surface of the graphite part as described above is rough, and SiO gas and Si vapor pass through the rough SiC layer, and the same reaction as above occurs in the unconverted part of the graphite part. The graphite parts are continuously subject to conversion erosion.
Since the coarse SiC layer formed in this way has almost no mechanical strength, the strength decreases when the graphite portion remaining after conversion is thinned, an increase in deformation due to its own weight, etc., generation of cracks, In the worst case, it leads to destruction. As described above, the graphite component is converted into a rough SiC layer by the SiO gas and the Si vapor, thereby causing a crack or breakage of the graphite component, resulting in a problem that the life of the graphite component is shortened.

On the other hand, SiC itself exists stably in the silicon crystal production environment. In Patent Documents 1 and 2, a SiC film is formed on the graphite component surface by the CVD method to suppress the conversion of the graphite component surface to a rough SiC layer. However, in addition to the tremendous equipment cost and member size restrictions imposed by the CVD apparatus, there is a problem that cracking occurs due to the difference in thermal expansion between the base graphite part and the SiC film.
Patent Document 3 discloses a SiC film forming method in which a glassy carbon layer is formed on the surface of a graphite part and a SiC layer is laminated thereon to suppress cracking due to a difference in thermal expansion between the base graphite part and the SiC layer. However, the SiC layer formed by this method is rough, and it is impossible to prevent the SiO gas and Si vapor from reaching the base graphite part. Therefore, the base graphite part is converted into a rough SiC layer. The effect of suppressing the above cannot be sufficiently obtained.

  Further, Patent Document 4 discloses that the base material is a high-strength carbon fiber reinforced carbon material in order to suppress cracking due to the difference in thermal expansion between the base graphite part and the SiC film, and the CVI method (chemical vapor infiltration method) is used for the pores. ) Has been disclosed to suppress the reaction between the pore inner surface of the carbon fiber-reinforced carbon material and the SiO gas, but the carbon material is exposed and the base material is converted into a rough SiC layer. In addition, the effect of suppressing the temperature cannot be sufficiently obtained, and the great equipment cost and member size restriction by the CVI apparatus are problems.

  As described above, the conventional technology sufficiently suppresses the cracking of the graphite component due to the difference in thermal expansion between the SiC and the graphite component during the SiC coating, and sufficiently suppresses the conversion of the graphite component to the SiC layer by SiO gas and Si vapor. I couldn't.

Japanese Patent Laid-Open No. 10-291896 JP-A-11-273835 JP-A-7-315967 JP 2000-247779 A

  The present invention has been made to solve the above-described problems, and is a silicon carbide-coated graphite member that dramatically improves the life of graphite parts by effectively suppressing the conversion of graphite parts into SiC layers. An object is to provide a manufacturing method.

  In order to solve the above problems, in the present invention, a graphite part having a SiC layer formed on its surface is coated and impregnated with silicone oil and fired to produce a silicon carbide-coated graphite member that densifies the SiC layer. Provide a method.

  With the method for producing a silicon carbide-coated graphite member of the present invention, the SiC layer on the surface of the graphite part is densified to effectively suppress the conversion of the surface of the graphite part to a rough SiC layer, thereby It is possible to manufacture a silicon carbide-coated graphite member that dramatically improves the life of the component.

At this time, the SiC layer formed on the surface of the graphite component is preferably formed by contact of the graphite component with SiO gas or Si vapor.
Further, at this time, as a means for contacting the graphite component with SiO gas or Si vapor, in the silicon crystal manufacturing apparatus, the SiO gas or Si vapor generated by holding Si melt with a quartz crucible is brought into contact with the graphite component. It is preferable.

  With such means, an SiC layer can be easily formed on the surface of the graphite part.

At this time, it is preferable that the silicone oil is applied and impregnated on a part of the surface of the graphite component.
In particular, it is preferable that the graphite component is a resistance heater having a slit, the silicone oil is applied and impregnated only around the slit of the resistance heater, and the current is fired.

  As a result, it is possible to effectively suppress the conversion of the graphite part into a coarse SiC layer by SiO gas and Si vapor while suppressing cracking of the graphite part due to the thermal expansion difference between the SiC layer and the graphite part. Further, the life can be improved. Moreover, it can bak efficiently by setting it as electric current baking.

  After the silicone oil is coated and impregnated, it is air-dried or heat-dried at a temperature of 100 ° C. or less, and then the calcination is performed in an inert gas atmosphere through one or more heating steps, and the maximum calcination temperature is 1500 ° C. or more. It is preferable to carry out at.

  By drying, the solvent in the silicone oil can be completely removed, and by setting it to such a firing temperature, the silicone oil can be completely thermally decomposed to form a dense SiC. In addition, by providing a heating step during firing, the effect of eliminating metal impurities can be obtained before the dense SiC layer is formed, so when high purity is required especially for semiconductor crystal production equipment for semiconductors. A suitably used silicon carbide-coated graphite member is obtained.

At this time, the silicone oil is preferably impregnated with a brush or spray.
If it is such a means, selective application of silicone oil can be easily given to arbitrary places.

  Moreover, in this invention, the silicon carbide covering graphite member manufactured by the manufacturing method of said silicon carbide covering graphite member is provided.

  With such a silicon carbide-coated graphite member, the SiC layer on the surface of the graphite component can be densified to effectively suppress the conversion of the graphite component surface to a rough SiC layer, so the life of the graphite component has jumped. Thus, the silicon carbide-coated graphite member is improved.

  Furthermore, in this invention, the manufacturing method of the silicon crystal which uses said silicon carbide covering graphite member is provided.

  With such a silicon crystal manufacturing method, since the silicon carbide-coated graphite member whose life of the graphite part has been dramatically improved is used, the time and cost required for replacing the conventional graphite part can be reduced.

As described above, according to the method for producing a silicon carbide-coated graphite member of the present invention, a coarse SiC layer of a graphite part can be obtained by densifying the SiC layer while suppressing cracking due to a difference in thermal expansion between the SiC layer and the graphite part. Therefore, it is possible to drastically improve the life of graphite parts, and to obtain a silicon carbide-coated graphite member that is suitably used when high purity such as a silicon crystal manufacturing apparatus for semiconductors is required. it can.
In addition, if the silicon crystal production method of the present invention using such a silicon carbide-coated graphite member is used, since the silicon carbide-coated graphite member having a dramatically improved life of the graphite component is used, the conventional graphite component can be replaced. The time and cost required can be reduced.

It is a flowchart which shows an example of the manufacturing method of the silicon carbide covering graphite member of this invention. It is a schematic sectional drawing which shows an example of the silicon crystal manufacturing apparatus used for the manufacturing method of the silicon crystal of this invention. It is a graph which shows the total ash content of each sample of an experiment example. It is a graph which shows the life until it leads to destruction of the graphite heater of Example 1 and Comparative Example 1.

  As described above, in order to extend the life of graphite parts, development of a method for effectively suppressing the conversion of graphite parts into a coarse SiC layer has been demanded.

  As a result of intensive studies on the above problems, the inventors of the present invention densified the coarse SiC layer by applying and impregnating a coarse SiC layer formed on the surface of the graphite part with a silicone oil, followed by firing. The present inventors have found that the densified SiC layer can suppress the conversion of the graphite part into a SiC layer beyond that, that is, can prolong the life of the graphite part.

  That is, the present invention is a method for producing a silicon carbide-coated graphite member in which the SiC layer is densified by applying and impregnating a silicone oil onto a graphite part having a SiC layer formed on the surface and firing.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
The silicon carbide-coated graphite member of the present invention and the graphite component used as the material thereof will be described by taking a graphite heater used for the production of silicon crystals as an example. Of course, the silicon carbide-coated graphite member of the present invention and its material The resulting graphite component may be other than a graphite heater.

Hereinafter, the manufacturing method of the silicon carbide covering graphite member of the present invention is explained, referring to drawings. FIG. 1 is a flowchart showing an example of a method for producing a silicon carbide-coated graphite member of the present invention.
In the present invention, the graphite layer 2 having the SiC layer 1 formed on the surface is coated and impregnated with (i) silicone oil, whereby the SiC layer 1 is made into the SiC layer 3 impregnated with silicone oil. Next, this is (ii) baked to turn the SiC layer 3 impregnated with silicone oil into a densified SiC layer 4 to produce the silicon carbide-coated graphite member 5 of the present invention.

In this invention, the silicon carbide covering graphite member manufactured with such a manufacturing method is provided.
The silicon carbide-coated graphite member of the present invention thus produced can effectively suppress the conversion of the graphite component to a further SiC layer in subsequent use by densifying the SiC layer on the surface of the graphite component. It becomes a silicon carbide-coated graphite member in which the life of the graphite component is dramatically improved.

Hereinafter, each process in the manufacturing method of the silicon carbide covering graphite member of this invention is demonstrated in detail.
First, a graphite component having a SiC layer formed on the surface is prepared. The formation of the SiC layer on the surface of the graphite component is preferably formed, for example, by contact between the graphite component and SiO gas or Si vapor, and the contact means between the graphite component and SiO gas or Si vapor is, for example, a silicon crystal production apparatus In this case, it is preferable that SiO gas or Si vapor generated by holding the Si melt with a quartz crucible is brought into contact with the graphite component.

More specifically, for example, when the graphite part is a graphite heater, the graphite heater is installed in a silicon crystal manufacturing apparatus to actually manufacture silicon crystals, and at that time, SiO generated from Si melt in the quartz crucible The SiC layer can be formed by growing the SiC layer to the target thickness on the surface of the graphite heater with gas or Si vapor.
With such a means, the SiC layer can be easily formed on the surface of the graphite part, but of course, another method in which the SiC layer is formed on the surface of the graphite part may be used.

Next, silicone oil is applied and impregnated on the graphite component having a rough SiC layer formed on the surface as described above (step (i) in FIG. 1).
Silicone oil impregnated in the SiC layer is thermally decomposed by firing to produce SiC, which fills the gaps in the coarse SiC layer, thereby forming a dense SiC layer. The dense SiC layer formed in this way is less permeable to SiO gas and Si vapor than the coarse SiC layer, so that even if a subsequent graphite member is used, the graphite component can be further applied to the SiC layer. Conversion can be effectively suppressed.

  The silicone oil used at this time is not particularly limited, but for example, dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil and the like are preferable.

The silicone oil is preferably applied by brushing or spraying at room temperature.
Silicone oil has a high affinity for the graphite component and the SiC layer, and can be impregnated and impregnated immediately after application. Therefore, it can be easily selectively applied to any location using a brush or a spray.

After the impregnation with silicone oil, baking is performed (step (ii) in FIG. 1).
At this time, in order to completely remove the solvent in the silicone oil, one or more heating steps are carried out in an inert gas atmosphere such as Ar and N ₂ by air drying or drying at a temperature of 100 ° C. or lower before firing. It is preferable to perform baking at a maximum baking temperature of 1,500 ° C. or higher via
More preferably, the maximum firing temperature is 1,500 ° C. or more and 2,000 ° C. or less, and the maximum firing temperature holding time is 1 hour or more and 5 hours or less.

  By setting the maximum firing temperature to 1,500 ° C. or higher, the silicone oil can be completely pyrolyzed to form SiC, and by providing a heating step, a relatively rough before the dense SiC layer is formed. Since the metal impurities are released and removed in the state, a high purification effect can be obtained, and silicon carbide-coated graphite that can be used even when high purity is required, such as a silicon crystal manufacturing apparatus for semiconductors, is obtained.

  Further, since the conversion reaction to the rough SiC layer on the surface of the graphite part represented by the above reaction formulas (1) and (2) proceeds more significantly in the high temperature part, the above-described silicone oil coating impregnation is performed on the entire graphite part. Instead, it is preferable to carry out locally on a part of the surface of the graphite part, particularly in a high temperature part where the reaction becomes remarkable. Thereby, since generation | occurrence | production of damage, such as a crack and a crack resulting from a thermal expansion difference of a SiC layer and a graphite component, can be suppressed, the lifetime of a graphite component can further be improved as a result.

  In particular, the resistance heating type graphite heater (resistance heating heater) used in the silicon crystal manufacturing apparatus has a maximum use temperature of about 1,800 ° C., and thus the conversion reaction to a rough SiC layer is remarkable. Since the high temperature portion concentrates around the slit of the heater, only the rough SiC layer formed in this region is subjected to the densification treatment of the SiC layer by applying and impregnating the silicone oil of the present invention and then firing. While effectively suppressing breakage due to the difference in thermal expansion between the SiC layer and the graphite component, a remarkable life extension effect can be obtained.

  At this time, the firing is preferably performed by electric firing. In the case of current firing, it is efficient because the resistance heater is energized after being impregnated with silicone oil and fired by the heat of the resistance heater itself.

  With the above method, cracking due to the difference in thermal expansion between the SiC layer and the graphite component can be suppressed, and the conversion to the SiC layer during use of the graphite component can be suppressed by densifying the SiC layer. A silicon carbide-coated graphite member that can be dramatically improved and that is suitably used when high purity is required, such as a silicon crystal manufacturing apparatus for semiconductors, can be obtained.

Furthermore, in this invention, the manufacturing method of the silicon crystal which uses the above-mentioned silicon carbide covering graphite member is provided.
Hereinafter, the method for producing a silicon crystal of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic cross-sectional view showing an example of a silicon crystal manufacturing apparatus used in the silicon crystal manufacturing method of the present invention.
In the silicon crystal manufacturing apparatus 10, the inside of a quartz crucible 14 in a cooling crucible 11 and a graphite crucible 13 disposed on a support shaft 12 is filled with Si melt 15. It is manufactured by landing on the Si melt 15 and pulling it into the pull chamber 19 along the pulling shaft 18. A graphite heater 20 for heating the Si melt 15 is installed on the outer periphery of the graphite crucible 13, and an inner shield 21 and a heat retaining cylinder 22 are installed on the outer periphery of the graphite heater 20 to insulate the heat from the graphite heater 20. ing.

  Ar gas supply part 23 is provided in the upper part of pull chamber 19, and Ar gas is made to flow as an inert gas. The Ar gas is guided to the surface of the Si melt 15 through the gas rectifying cylinder 24 and the silicon crystal 16. The Ar gas flows under a reduced pressure through a guide path formed by the heat shield member 25 disposed immediately above the Si melt 15 and the surface of the Si melt 15, and further by the inner wall portion of the quartz crucible 14 and the outside of the heat shield member 25. It is discharged out of the quartz crucible 14 through the formed guiding path. The graphite heater 20 is disposed between the graphite crucible 13 and the inner shield 21, and Ar gas is forcibly exhausted by a vacuum pump from the Ar exhaust part 26 at the lower part of the cooling chamber 11.

  Accordingly, the Si vapor and SiO gas discharged from the surface of the Si melt 15 flow toward the Ar exhaust part 26 through a guide path formed by the outer wall of the graphite crucible 13 and the inner wall part of the inner shield 21. On the surface of the graphite heater 20 disposed in the center of the induction path, the conversion reaction to the SiC layer by SiO gas and Si vapor is particularly likely to proceed.

Therefore, the present invention provides a method for producing silicon crystals using, for example, the above-described silicon carbide-coated graphite member of the present invention as the graphite heater 20 in FIG.
As described above, since the silicon carbide-coated graphite member of the present invention has a dense SiC layer on its surface, it can be used as a graphite heater because the surface of the graphite component can be further suppressed from being converted into the SiC layer during crystal production. In this case, the life of the graphite heater can be extended. That is, the time and cost required for replacing the conventional graphite heater can be reduced.

As described above, according to the method for producing a silicon carbide-coated graphite member of the present invention, a coarse SiC layer of a graphite part can be obtained by densifying the SiC layer while suppressing cracking due to a difference in thermal expansion between the SiC layer and the graphite part. Therefore, it is possible to drastically improve the life of graphite parts, and to obtain a silicon carbide-coated graphite member that is suitably used when high purity such as a silicon crystal manufacturing apparatus for semiconductors is required. it can.
In addition, if the silicon crystal production method of the present invention using such a silicon carbide-coated graphite member is used, since the silicon carbide-coated graphite member having a significantly improved life is used, the time required for replacing the conventional graphite parts And cost can be reduced.

  Hereinafter, the present invention will be specifically described using experimental examples, examples, and comparative examples, but the present invention is not limited to these examples.

(Experimental example)
Prepare a graphite part with a 10 mm square and a thickness of 5 mm with a SiC layer formed on the surface, and prepare two samples: (a) a silicone oil not coated and impregnated with this graphite part, and (b) a silicone oil coated and impregnated. Produced. The silicone oil was dimethyl silicone oil and applied with a Teflon (registered trademark) brush. (B) After the sample coated with silicone oil was air-dried for 1 day, both the samples (a) and (b) were each subjected to 1,000 ° C./5 hr, 1,350 ° C./5 hr, 1,550 in an Ar atmosphere. A three-step heating step baking at 5 ° C./5 hr was performed, and the purity level was evaluated based on the total ash content of each sample after baking. As for the total ash content, each sample after firing was placed in a quartz container and subjected to an ashing treatment in an oxygen-containing atmosphere at 900 ° C., and then the weight of the remaining ash content was measured. FIG. 3 shows the result of measuring the total ash content of each sample.

As shown in FIG. 3, when calcination was performed by three-step heating step calcination, the total ash content of both samples (a) and (b) was the same.
From this, when silicone oil is applied and impregnated, by providing a heating step during firing, an effect of eliminating metal impurities can be obtained before a dense SiC layer is formed. It was suggested that a silicon carbide-coated graphite member that can be suitably used when high purity such as the above is required can be obtained.

(Comparative Example 1)
The growth of silicon crystals was repeated using a silicon crystal production apparatus by the Czochralski method shown in FIG. 2, and the life until destruction of the graphite heater was evaluated. The result is shown in FIG. In the graph of FIG. 4, the life index 1 was defined as the life until the graphite heater of Comparative Example 1 was destroyed.

(Comparative Example 2)
In Comparative Example 1, when a silicon crystal was grown under the same conditions except that the graphite heater was a graphite heater (CVD-SiC coated graphite heater) coated with a SiC film by a CVD method, the CVD-SiC coated graphite heater was Breaked in one batch.

Example 1
First, the growth of silicon crystals was repeated under the conditions of Comparative Example 1 to form a 1 mm thick SiC layer on the surface of the graphite heater. The formation of the SiC layer having a thickness of 1 mm required 0.04 in the above life index.
Next, silicone oil was applied and impregnated into the formed SiC layer. The silicone oil was dimethyl silicone oil and applied with a Teflon (registered trademark) brush. The application range was the entire circumference from 20 mm above the heater slit intersection to 20 mm below.
After impregnating with silicone oil, air-drying for one day, and then performing three-step heating step firing at 1,000 ° C / 5hr, 1,350 ° C / 5hr, 1,550 ° C / 5hr in an Ar atmosphere, and SiC layer densified graphite A heater was used. Thereafter, silicon crystal growth was repeated again, and the life until the SiC layer densified graphite heater was destroyed was evaluated. The result is shown in FIG.

  As shown in FIG. 4, the life index of the SiC layer densified graphite heater of Example 1 was 2.3 times that of the graphite heater of Comparative Example 1. Further, the degree of thinning of the graphite heater in the same life index of Example 1 was less than half that of Comparative Example 1.

  From the above, in the case of the silicon carbide-coated graphite member manufactured by the manufacturing method of the present invention, the cracking of the SiC layer and the graphite component due to the thermal expansion difference is suppressed, and the roughening of the graphite component by the densification of the SiC layer It has been clarified that since the conversion to the SiC layer can be suppressed, the life of the graphite component can be dramatically improved.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... SiC layer, 2 ... Graphite component, 3 ... SiC layer impregnated with silicone oil,
4 ... Densified SiC layer, 5 ... Silicon carbide coated graphite member,
DESCRIPTION OF SYMBOLS 10 ... Silicon crystal manufacturing apparatus, 11 ... Cooling chamber, 12 ... Support shaft,
13 ... graphite crucible, 14 ... quartz crucible, 15 ... Si melt,
16 ... silicon crystal, 17 ... seed crystal, 18 ... pulling shaft, 19 ... pull chamber,
20 ... Graphite heater, 21 ... Inner shield, 22 ... Insulation tube,
23 ... Ar air supply unit, 24 ... Gas rectifier, 25 ... Heat shield member, 26 ... Ar exhaust unit.

Claims (7)

It is a method of densifying the SiC layer by applying and impregnating silicone oil to a graphite component having a SiC layer formed on the surface and firing it .
The SiC layer formed on the surface of the graphite part is formed by contact of the graphite part with SiO gas or Si vapor,
A method for producing a silicon carbide-coated graphite member, wherein the graphite component is a resistance heater having a slit, the silicone oil is applied and impregnated only around the slit of the resistance heater, and the current is fired . As a contact means between the graphite component and SiO gas or Si vapor, in a silicon crystal production apparatus, the SiO gas or Si vapor generated by holding Si melt with a quartz crucible is brought into contact with the graphite component. The method for producing a silicon carbide-coated graphite member according to claim 1 . The method for producing a silicon carbide-coated graphite member according to claim 1 or 2 , wherein the silicone oil is coated and impregnated on a part of the surface of the graphite part. After the silicone oil is coated and impregnated, it is air-dried or heat-dried at a temperature of 100 ° C. or less, and then the calcination is performed in an inert gas atmosphere through one or more heating steps, and the maximum calcination temperature is 1500 ° C. The method for producing a silicon carbide-coated graphite member according to any one of claims 1 to 3 , wherein The method for producing a silicon carbide-coated graphite member according to any one of claims 1 to 4 , wherein the silicone oil is applied and impregnated by brush or spray. A silicon carbide-coated graphite member,
The surface of the graphite part has a dense SiC layer filled with voids,
The graphite part is a resistance heater having a slit, and the silicon carbide-coated graphite member has the densified SiC layer only around the slit of the resistance heater . A method for producing a silicon crystal, comprising using the silicon carbide-coated graphite member according to claim 6 .

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