JP2000319090A - Heat insulation cylinder for single crystal pulling-up device and single crystal pulling-up device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulation cylinder for use in a single crystal pulling-up device, which can be produced at a reduced cost and has a long service life and also can easily be replaced. SOLUTION: This heat insulation cylinder 30 is placed in the space between a heater 20 for heating a crucible 10 in a single crystal pulling-up device 100 and a heat insulation material 40 for inhibiting heat from the heater 20 from being transferred to the outside, and used for performing heat insulation within the single crystal pulling-up device 100, wherein the inner constituent material of the cylindrical wall of the heat insulation cylinder 30 is a carbon material having a 2.0-0.1 mm thickness in the radial direction and a coating film consisting of pyrolytic carbon is formed on a part or the whole of the surface of the inner carbon material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal pulling apparatus and a member for forming the single crystal pulling apparatus, and more particularly, to a single crystal pulling apparatus which is disposed between a heater and a heat insulating material. And a single crystal pulling apparatus provided with the heat retaining cylinder.

[0002]

2. Description of the Related Art There are various types of single crystal pulling apparatuses, but each of them has a common problem in apparatuses for pulling single crystals of electronic materials such as silicon and compound semiconductors such as gallium-arsenic and gallium-phosphorus. Therefore, a silicon single crystal pulling apparatus will be particularly described below as an example.

A silicon single crystal pulling apparatus pulls a silicon single crystal from a silicon melt in a crucible in the presence of an atmospheric gas by a so-called Czochralski method, for example, Japanese Patent Publication No. 57-15079. Is known as a "single crystal pulling apparatus" as disclosed in Japanese Patent Application Publication No. As shown in FIG. 3, the apparatus disclosed in this publication is configured such that “a rotary shaft 2 is introduced into a furnace body container 1 from below, and a crucible 4 is disposed on an end surface of the rotary shaft 2 via a tray 3. A heating element 5 and a heat retaining cylinder 6 are arranged around the crucible 4, and silicon is melted in the crucible 4 to obtain a melt 7. On the other hand, a rotating shaft which slides up and down is placed above the furnace vessel 1. A silicon seed crystal 8 is attached to the free end of the rotating shaft 9, and the rotating shaft 9 is moved upward from a state where the seed crystal 8 is in contact with the melt 7 in the crucible 4, Seed crystal 8
To obtain a silicon single crystal 10 continuing below. When growing a single crystal, an unnecessary reaction product gas contains the single crystal 10 and the melt 7.
It is necessary to eliminate this so as not to react at the liquid level. For this purpose, an inert gas such as argon is supplied as an atmospheric gas to the single crystal and the liquid level from above the furnace vessel 1,
It is discharged from the lower part of the furnace body container "(the second column of the above publication). The members denoted by reference numeral 5 in FIG.
As a heater, a heat insulating material is disposed between the heat retaining cylinder 6 and the furnace body container 1 as shown in FIG.

[0004] By the way, as a material for forming the above-mentioned heat retaining cylinder, there are graphite and a carbon-bonded carbon fiber composite material (hereinafter, simply referred to as C / C composite). The heat retaining cylinder made of graphite is manufactured by lathe processing of a columnar or square block material. Further, the heat retaining cylinder made of the C / C composite is manufactured by repeatedly winding a carbon fiber in a multilayer shape in a cylindrical shape around a mold prepared in advance, curing with resin or pitch, and repeatedly carbonizing and impregnating. As described above, the production of the heat retaining cylinder requires a great deal of time and cost, and the proportion of the production cost of the silicon single crystal is increasing.

[0005] In addition, the following new problems have arisen. That is, the heat retaining cylinder is used at a high temperature, and it is considered that the following reaction occurs during the silicon single crystal pulling operation. (1) SiO + 2C → SiC + CO In other words, in the heat retaining cylinder heated to a high temperature, carbon in the surface layer is silicified. The silicide layer thus formed is
Since the material of the heat retaining cylinder is different from the physical properties, it causes cracks when the silicon single crystal pulling apparatus is stopped and cooled, and if cracks occur, the silicide layer etc. peels off as small pieces. May fall into the silicon melt,
This causes crystal defects in the pulled Si single crystal.

Further, when the plate material is curved into a cylindrical shape, it is necessary to reduce the thickness as much as possible in order to obtain a desired curvature. If the thickness is reduced, cracks due to silicidation increase and the life is shortened. Did not connect.

On the other hand, if the thickness of the base material of the heat insulating cylinder becomes unnecessarily thick, the heat capacity becomes large and it takes time to cool down, and the weight of the heat insulating cylinder hinders accurate setting. A problem occurs in the replacement work.

The inventor of the present invention has conducted various studies on how to solve the above-mentioned problems with respect to this type of heat retaining cylinder for a single crystal pulling apparatus, and as a result, completed the present invention. is there.

[0009]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above circumstances, and the problem to be solved is to reduce the cost of a heat retaining cylinder in this type of single crystal pulling apparatus. The purpose is to make the replacement work easier and have a longer life.

That is, the object of the present invention is to provide S
An object of the present invention is to provide a heat insulating cylinder which can prevent silicification due to reaction with iO gas or the like so as not to cause cracks, has high durability, is inexpensive, and has excellent workability.

[0011]

Means for Solving the Problems To solve the above problems, first, means according to the first aspect of the present invention will be described with reference numerals used in the following description of the embodiments. "It is disposed between a heater 20 for heating the crucible 10 in the single crystal pulling apparatus 100 and a heat insulating material 40 for preventing heat from the heater 20 from moving outside. Is a heat insulation cylinder 30 for keeping the heat inside, and the inside of the cylinder wall has a thickness of 2.0 m in the radial direction.
A heat insulating cylinder 30 for a single crystal pulling apparatus, comprising a carbon material of m to 0.1 mm, and a coating 32 made of pyrolytic carbon formed on a part or all of the surface thereof.

That is, as shown in FIG. 1, the heat retaining cylinder 30 according to the present invention controls the heater 20 for heating the crucible 10 in the sealed main body 50 and restricts the outward movement of heat from the sealed main body 50. It is interposed between the heat insulating material 40 to be used.

In the heat insulation cylinder 30 according to the first aspect of the present invention, it is necessary to form a coating 32 made of pyrolytic carbon on a part or all of the surface of the carbon material as the base material 31. The reason is that it is necessary to prevent the contact between the base material 31 and the SiO gas by the pyrolytic carbon film 32 so that the reaction shown in the above-mentioned formula (1) does not occur.

The thickness of the pyrolytic carbon coating 32 is 10 μm.
It is preferably from m to 200 μm. The reason is 1
When the thickness is less than 0 μm, the ratio of continuous pores in the coating 32 increases, and the sealing property rapidly deteriorates.
Is exceeded, the effect of the mismatch of the thermal expansion coefficient with the underlying carbon material sharply increases. Since the entire surface of the carbon material or the surface facing the heater is activated, the surface is coated only on that surface.

The thickness of the heat retaining cylinder 30 according to the first aspect must be 2.0 mm to 0.1 mm. The reason for this is that if the thickness is 2.0 mm or more, the heat capacity increases, so that it takes time to cool down, and the weight is large, which hinders accurate setting. on the other hand,
The reason why the thickness must be 0.1 mm or more is that the ratio of the porous portion is reduced and the heat insulating effect as designed is not exhibited.

Next, in the invention according to claim 2, the heat retaining cylinder 30 is formed by curving a plate material 31 made of a carbon material. In view of the need to bend, its thickness is 1.
More preferably, it is 0 mm to 0.5 mm.

According to the heat retaining cylinder 30 of the present invention configured as described above, the following effects are exhibited.
That is, in the heat retaining cylinder 30 according to the present invention, since the dense pyrolytic carbon film 32 as shown in FIG. 2 is formed,
The SiO gas and the Si gas scattered here do not come into contact with the plate 31 made of the carbon material by the pyrolytic carbon coating 32, and therefore do not react with the carbon in the plate 31.

The heat insulation cylinder 30 has a thickness of 2.0 m.
m, and has a low heat capacity and a light weight, so that the work of replacing the heat retaining cylinder 30 is easy. Further, the plate member 31 can be configured by being curved, so that the cost is very low and the durability is very high.

Next, in order to solve the above-mentioned problem, a means adopted by the invention according to claim 4 is that the carbon material is a C / C composite in the heat retaining cylinder 30 according to claims 1 to 3. It was that.

That is, the heat insulation cylinder 30 is set to a thickness of 2.0 m.
It must be composed of a m / 0.1 mm C / C composite. The reason is that the C / C composite has high strength and more reliably prevents cracking.

[0021] In order to solve the above-mentioned problem, a means adopted by the invention according to claim 5 is that the heat retaining cylinder 30 according to claims 1 to 4 is described as “from room temperature of carbon material to 100 ° C.
The average coefficient of thermal expansion at 0 ° C. is 2.5 to 5.0 × 10 ^−6.
/ ° C ”.

As described above, the average thermal expansion coefficient of the carbon material as the base of the heat retaining cylinder 30 from room temperature to 1000 ° C. needs to be 2.5 to 5.0 × 10 ⁻⁶ / ° C. The reason is that this kind of heat retaining cylinder 30 receives thermal stress due to heating by the heater 20 and cooling when stopping the silicon single crystal pulling apparatus 100 itself.
If the average thermal expansion coefficient of the carbon material is out of the above range, the pyrolytic carbon coating 32 will frequently peel off from the surface of the carbon material due to repeated heating and cooling. is there.

In order to solve the above-mentioned problem, the means adopted by the invention according to claim 6 is that the heat insulation cylinder 30 according to claims 1 to 5 is described as follows: "The Young's modulus of the carbon material is 1400 kg / mm at room temperature. ² or less ".

The reason why the Young's modulus of the carbon material as the base of the heat retaining cylinder 30 is 1400 kg / mm ² or less at room temperature is that if the material is outside the above range, the plate material 31 made of the carbon material is bent. This is because cracks are generated or excessive force is required at the stage of forming the heat retaining cylinder 30.

Further, vibration or the like may be applied to the heat retaining cylinder 30 and mechanically affected by the vibration for a long period of time. In order to withstand the effect without any trouble, the value of the Young's modulus must be: 300 kg / mm ^{2 to} 1200 kg /
mm ² is preferred.

[0026] In order to solve the above-mentioned problem, a seventh aspect is provided.
The means adopted by the invention according to (1) is that the number of fibers of the carbon fiber bundle of the C / C composite is 6000 to 100 in the heat retaining cylinder 30 according to claim 4.

As described above, the C / C,
The carbon fiber bundle constituting the composite has 600 fibers.
The reason why the number is not more than 0 is that if the number is more than 6000, the unevenness of the surface becomes large, and the effect of the pyrolytic carbon coating 32 as a reaction element with SiO gas and Si gas cannot be sufficiently exhibited. On the other hand, the reason for setting the number to 100 or more is that the strength of the carbon fiber bundle cannot sufficiently withstand the speed for securing a constant production amount in the loom.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the embodiment shown in the drawings. FIG. 1 shows a silicon single crystal pulling apparatus 10 to which a heat retaining cylinder 30 according to the present invention is applied.
0 is shown in the longitudinal section. In the silicon single crystal pulling apparatus 100, a crucible 10 for melting silicon is rotatably housed in a sealed main body 50 around a rotation shaft 55. The crucible 10 is heated around the crucible 10. Heater 20 is arranged. Outside the heater 20, a heat retaining cylinder 30 according to the present invention is arranged, and a heat insulating material 40 is housed between the heat retaining cylinder 30 and the sealed main body 50.

The crucible 10 has a double structure in which the portion directly in contact with the molten silicon is a quartz crucible 11, and the heater 20 is generally a so-called graphite heater. The melting in the crucible 10 must be complete and sufficient. Since the liquid level of the molten silicon is lowered by the lifting, the crucible 10 is moved upward and the heat generated by the heater 20 is generated. The center and the liquid level of the molten silicon in the crucible 10 have a fixed relationship.

The heat retaining cylinder 30 is made of graphite with developed crystal among carbon materials, and a pyrolytic carbon film 32 is formed on the graphite substrate 31 as shown in FIG. These pyrolytic carbon coating 32 and graphite substrate 31
It is manufactured or formed as shown in the following examples.
The average coefficient of thermal expansion at 0 ° C. is 2.5 to 5.0 × 10 ^−6.
/ ° C and a Young's modulus of 1200 kg / mm ² or less.

Further, in the heat retaining cylinder 30 according to the present invention, the graphite substrate 31 is a C / C composite, and the carbon fiber bundles constituting the substrate are those having 6,000 or less fibers.

Now, the insulated cylinder 30 according to the present invention will be described in more detail with reference to an embodiment including a method of manufacturing the same.

[0033]

EXAMPLE After heating and kneading 70 parts by weight of aggregate coke pulverized to an average particle diameter of 20 μm and 30 parts by weight of coal tar pitch as a binder, the kneaded product was mixed with 30 to 200 μm.
m to form a carbon material raw material.

Using the carbon material, a desired compact was formed by a rubber press method, and the compact was fired and graphitized to form a graphite material. The average thermal expansion coefficient of the obtained graphite material was 4.8 × 10 ⁻⁶ / ° C. The Young's modulus of the graphite material was 1120 kg / mm ² .

The graphite material was processed to obtain a graphite substrate 31 having a width of 550 mm, a length of 1300 mm and a thickness of 1 mm.

The obtained base material was placed in a CVD furnace,
C., and methane gas was continuously supplied into the furnace using hydrogen gas as a carrier. Thus, a pyrolytic film 32 having a thickness of about 50 μm was formed on the entire surface of the substrate.

[0037]

Example: A carbon fiber bundle (strand) has 600 fibers.
This is laminated using a cloth knitted with 0 carbon fibers,
It was impregnated with a phenol resin and fired at 900 ° C. after curing. Further, phenol resin impregnation, curing and firing were repeated twice, and this was graphitized to a thickness of 550 mm and a length of 1300 m.
Graphite substrate 3 made of C / C composite having a thickness of 1 mm
1 was obtained. A pyrolytic carbon film 32 was formed on the substrate 31 by the same method as in Example 1.

[0038]

Comparative Example 1 The graphite material of Example 1 was processed, and
A graphite base material 31 having the same shape as that of the above was obtained.

[0039]

Comparative Example 2 After heating and kneading 70 parts by weight of aggregate coke pulverized to an average particle size of 10 μm and 30 parts by weight of coal tar pitch serving as a binder, the kneaded product was heated to 30 to 150 μm.
To form a carbon material.

Using the carbon material, a desired compact was formed by a rubber press method, and the compact was fired and graphitized to form a graphite material. The average thermal expansion coefficient of the obtained graphite material is 5.5 × 10 ⁻⁶ / ° C., and the Young's modulus is 1250 k.
g / mm ² .

This graphite material was processed to obtain a graphite substrate 31 having the same shape as in Example 1, and a pyrolytic carbon film 32 was formed on the substrate 31 in the same manner as in Example 1.

[0042]

Comparative Example 3 The graphite material of Example 1 was processed to have a width of 550.
A graphite substrate 31 having a length of 1300 mm and a thickness of 2.5 mm was obtained. A pyrolytic carbon film 32 was formed on the substrate 31 in the same manner as in the example.

[0043]

Comparative Example 4 A cloth woven from carbon fibers bundled with carbon fibers of 12,000 fibers was laminated, impregnated with a phenol resin, cured and baked at 900 ° C. Further, phenol resin impregnation, curing, and firing were repeated twice, and this was graphitized to obtain a graphite substrate made of a C / C composite having a width of 550 mm, a length of 1300 mm, and a thickness of 1 mm. The pyrolytic carbon coating 3 is applied to the substrate 31 in the same manner as in the first embodiment.
2 was formed.

The graphite substrate 31 obtained in this manner was bent into a heat insulating material 40 to obtain a heat retaining cylinder 30. Table 1 shows the situation at this time.

[0045]

[Table 1] In addition, when the life of each of the heat retaining cylinders was compared, the results shown in the following Table 2 were obtained.

[0046]

[Table 2]

[0047]

As described in detail above, in the present invention,
As exemplified in the above embodiment, “the single crystal pulling apparatus 100 is disposed between the heater 20 for heating the crucible 10 inside and the heat insulating material 40 for preventing heat from the heater 20 from moving to the outside. In addition, it is a heat retaining cylinder 30 for keeping the temperature in the single crystal pulling apparatus 100, and the inside of the cylindrical wall is made of a carbon material having a thickness of 2.0 mm to 0.1 mm in a radial direction, and a part or all of the surface thereof is provided. The formation of the coating 32 made of pyrolytic carbon "has a structural feature, and it is possible to provide a heat insulating cylinder having high durability and easy replacement operation.

Further, in the invention according to claim 2, the heat retaining cylinder 30 according to claim 1 is formed by curving a plate material made of a carbon material. It can be provided.

According to the third aspect of the present invention, in the heat retaining cylinder 30 according to the first or second aspect, the thickness of the pyrolytic carbon film is set to 10 μm to 200 μm, and the durability is greatly improved. It is possible to provide a heat retaining cylinder capable of performing the above.

In the invention according to claim 4, in the heat retaining cylinder 30 according to any one of claims 1 to 3, the carbon material is C / C.
It is possible to provide a heat insulating cylinder which is a C composite and can surely prevent cracking.

According to the fifth aspect of the present invention, in the heat retaining cylinder 30 according to any one of the first to third aspects, the average thermal expansion coefficient of the carbon material from room temperature to 1000 ° C. is 2.5 to 1,000.
It is characterized in that it is 5.0 × 10 ⁻⁶ / ° C., and it is possible to provide a heat insulation cylinder in which the pyrolytic carbon film does not peel off from the graphite substrate surface by repeating heating and cooling. .

Further, according to the invention of claim 6, in the heat retaining cylinder 30 according to any of claims 2 to 6, the Young's modulus of the carbon material is 1400 kg / mm ² or less at room temperature. Therefore, it is possible to provide a heat retaining cylinder in which cracks are not generated or a force is not exerted at the stage of configuring the heat retaining cylinder 30.

According to the seventh aspect of the present invention, in the heat retaining cylinder 30 according to the fourth aspect, the number of carbon fiber bundles constituting the C / C composite is 6000 to 10
There is a structural feature in that the number is zero, and it is possible to provide a heat retaining cylinder capable of sufficiently exhibiting an action of preventing the pyrolytic carbon coating 32 from reacting with SiO gas and Si gas.

Finally, according to the invention of claim 8, it is possible to provide a single crystal pulling apparatus provided with a heat retaining cylinder which is durable and inexpensive and which can be easily replaced.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a silicon single crystal pulling apparatus employing a heat retaining cylinder according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the thermal insulation cylinder, with a focus on a pyrolytic carbon coating.

FIG. 3 is a cross-sectional view showing a conventional silicon single crystal pulling apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 silicon single crystal pulling apparatus 10 crucible 11 quartz crucible 20 heater 30 heat retaining cylinder 31 graphite base material 32 pyrolytic carbon 40 heat insulating material 50 closed body

Claims (8)

[Claims] 1. A heater for heating a crucible in a single crystal pulling apparatus and a heat insulating material for preventing heat from the heater from moving to the outside, and keeping heat in the single crystal pulling apparatus. The inside of the cylinder wall is made of a carbon material having a thickness of 2.0 mm to 0.1 mm in a radial direction, and a coating made of pyrolytic carbon is formed on part or all of the surface thereof. Heating cylinder for single crystal pulling device. 2. A heat retaining cylinder for a single crystal pulling apparatus according to claim 1, wherein a plate material made of a carbon material is curved. 3. The thickness of a coating made of pyrolytic carbon is 10 μm.
3. The method according to claim 1, wherein the diameter is from m to 200 μm.
A heat retaining cylinder for a single crystal pulling apparatus as described in the above. 4. The heat retaining cylinder for a single crystal pulling apparatus according to claim 1, wherein the carbon material is a C / C composite. 5. The single crystal pulling apparatus according to claim 1, wherein the average thermal expansion coefficient of the carbon material from room temperature to 1000 ° C. is 2.5 to 5.0 × 10 ⁻⁶ / ° C. Heat insulation tube. 6. The carbon material has a Young's modulus of 1400 at room temperature.
6. The heat retaining cylinder for a single crystal pulling apparatus according to claim 1, wherein the temperature is not more than kg / mm ² . 7. The heat retaining cylinder for a single crystal pulling apparatus according to claim 4, wherein the carbon fiber bundle of the C / C composite has 6,000 to 100 fibers. 8. A single crystal pulling apparatus comprising a heat retaining cylinder disposed between a heater for heating a crucible and a heat insulating material for preventing heat from the heater from moving to the outside. A single crystal pulling apparatus, wherein the cylinder is the heat retaining cylinder according to any one of claims 1 to 7.