JP2015093793A - Single crystal production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a single crystal capable of preventing easily a graphite component used in a furnace of a single crystal production apparatus from being cracked owing to an attachment such as a Si vapor-deposit.SOLUTION: In a single crystal production method, a single crystal is raised from a raw material melt stored in a crucible arranged in a furnace of a single crystal production apparatus by CZ method. In the single crystal production method, when raising a single crystal, a graphite component to be used in the furnace of the single crystal production apparatus is used after applying thereto a coating containing silicon nitride to form a silicon nitride film on the surface.

Description

  The present invention relates to a method for producing a single crystal, and more particularly to a method for producing a single crystal using a single crystal production apparatus based on the Czochralski method (CZ method).

  Many graphite parts are used in the furnace of a single crystal manufacturing apparatus for growing silicon single crystals and the like by the CZ method. Further, during operation of the silicon single crystal manufacturing apparatus, Si vapor and SiO gas are generated from the raw material melt (silicon melt) accommodated in the crucible disposed in the furnace. The generated Si vapor and SiO gas move in accordance with the flow of a gas such as an inert gas that flows into the furnace and is led out of the furnace.

  In this gas flow in the furnace, deposits due to the Si vapor or SiO gas are deposited particularly on the surface of the graphite component located downstream of the crucible. The deposit formed in a layered manner in this way is very firmly fixed to the surface of the graphite part. When the temperature of the furnace is raised or lowered, the graphite part is cracked due to the difference in thermal expansion coefficient between the deposit and the graphite part, and as a result, the life of the graphite part is shortened.

JP 2007-261832 A Japanese Patent Application Laid-Open No. 06-122587 Japanese Patent Laid-Open No. 09-183686

Here, the following literature is mentioned as a technique regarding a graphite component.
For example, Patent Document 1 discloses a technique for easily removing the obtained polycrystalline silicon from the crucible by coating the surface of the crucible for producing polycrystalline silicon with silicon nitride.
Patent Documents 2 and 3 disclose a technique for coating the surface of a graphite component with silicon nitride in a single crystal manufacturing apparatus. However, these coatings are produced by chemical vapor deposition (CVD), and there are problems that it is difficult to process large members, and that local coating is difficult and costly.

  On the other hand, as a method of forming silicon nitride relatively easily, there is a slip casting method in which it is put in a mold and sintered. Further, as disclosed in Patent Document 1, a polyvinyl alcohol aqueous solution is used as a binder and used as a release material. However, single crystal silicon has a problem of purity and has not been used.

  The present invention has been made in view of the above problems, and it is easy to prevent a graphite component used in a furnace of a single crystal manufacturing apparatus from being cracked due to deposits such as Si deposits. An object of the present invention is to provide a method for producing a single crystal.

  In order to achieve the above object, the present invention provides a single crystal production method for growing a single crystal from a raw material melt contained in a crucible placed in a furnace of a single crystal production apparatus by a CZ method, wherein the single crystal A single crystal manufacturing method using a graphite component used in the furnace of the single crystal manufacturing apparatus, wherein a silicon nitride-containing paint is applied to form a silicon nitride film on the surface thereof I will provide a.

In this way, the silicon nitride film can be formed very easily for application as compared with, for example, the CVD method. Local film formation is easy, and film formation can be performed at low cost.
Then, by using such a silicon nitride film formed, even if deposits such as Si deposits are formed, the place to be formed is not the surface of the graphite part itself but the surface of the silicon nitride film Therefore, for example, by removing a part of the silicon nitride film, the deposit can be easily removed. In the past, the deposits were firmly fixed directly on the surface of the graphite part itself, causing cracks in the graphite part. However, in the case of the present invention, it is possible to prevent and prevent the deposits from directly fixing on the graphite part as described above, and thus it is possible to easily prevent the graphite part from cracking. Therefore, the life of the graphite component can be greatly extended. For this reason, the exchange frequency of graphite parts can also be suppressed and the increase in the cost accompanying replacement | exchange can also be suppressed.

  And after growing the single crystal, when deposits are confirmed on the surface of the silicon nitride film of the graphite component, after removing the deposits by peeling at least a part of the silicon nitride film, When the next single crystal is grown and no deposit is observed on the surface of the silicon nitride film of the graphite part, the next single crystal can be grown as it is without peeling the silicon nitride film.

In this way, for example, the deposits can be easily removed by peeling off the extreme surface layer of the silicon nitride film.
Moreover, if there is no deposit, it can be used in the growth of the next single crystal as it is, which is efficient and simple.

  Further, when growing a silicon single crystal using the raw material melt as a silicon melt, graphite at a location where a silicon deposit or a silicon oxide deposit is formed by contact with Si vapor or SiO gas from the silicon melt. A component having the silicon nitride film formed thereon can be used.

  As described above, Si vapor or the like is generated from the silicon melt. Therefore, for example, it is particularly effective to form a silicon nitride film on a graphite component placed at a location in contact with Si vapor or the like, such as a position downstream from the crucible in the gas flow in the furnace. is there.

  In addition, the paint containing silicon nitride may be obtained by dispersing silicon nitride powder in the polyvinyl alcohol aqueous solution using a polyvinyl alcohol aqueous solution as a binder.

  If such a paint is used, a silicon nitride film can be easily formed on the surface of the graphite component.

  Moreover, when apply | coating the coating material containing the said silicon nitride, it can carry out using a brush or spray.

  If these methods are used, a paint can be easily applied to a graphite part without labor and cost. In addition, it is easy to deal with the case of applying locally.

  As described above, according to the present invention, it is possible to easily and inexpensively prevent Si deposits or the like from directly fixing to a graphite component in a furnace of a single crystal manufacturing apparatus and cracking the graphite component. The life of graphite parts can be improved.

It is the schematic which shows an example of the single crystal manufacturing apparatus which can be used for the single crystal manufacturing method of this invention. It is a graph which shows the relationship of the mass increase rate with respect to the use time of the sample graphite component of a comparative example and an Example. It is a graph which shows the life parameter | index comparison of the gas discharge sleeve of a comparative example and an Example.

Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
An example of a CZ single crystal manufacturing apparatus that can be used in the single crystal manufacturing method of the present invention is shown in FIG. Here, a case where a silicon melt obtained by melting polycrystalline silicon is prepared as a raw material melt and a silicon single crystal is grown from the silicon melt will be described as an example, but the present invention is not limited thereto. For example, when a compound semiconductor single crystal such as GaP or an oxide single crystal such as GGG is grown by the CZ method, a graphite component is used in the furnace, and the same can be applied.

  In the furnace (main chamber 2) of the silicon single crystal manufacturing apparatus 1, a crucible 4 (quartz crucible 5 and quartz crucible 5 for containing a raw material melt (silicon melt 3) in which polycrystalline silicon is melted is stored. Is provided with a graphite crucible 6). A pulling mechanism (not shown) for pulling up the grown silicon single crystal is provided above the pulling chamber 7 connected to the main chamber 2.

  A pulling wire 8 is unwound from a pulling mechanism attached to the upper part of the pulling chamber 7, and a seed crystal 9 supported by a seed holder is attached to the tip of the pulling wire 8. A silicon single crystal 10 is grown below the seed crystal 9 by dipping in the liquid 3 and winding the pulling wire 8 by a pulling mechanism.

  The crucible 4 is supported by a support shaft 11 that can be rotated up and down by a rotation drive mechanism (not shown) attached to the lower part of the silicon single crystal manufacturing apparatus 1.

  In addition, a peripheral heat insulating member 13 is provided outside and above the graphite heater 12 disposed around the crucible 4. Here, the peripheral heat insulating member 13 includes an inner shield 15 and a heat shield 14 on the outer side thereof, an upper shield heat insulating material 16 and an upper shield 17 on the lower side thereof.

The chambers 2 and 7 are provided with a gas inlet 18 and a gas outlet 19 so that an inert gas (for example, argon gas) or the like can be introduced into the chambers 2 and 7 and discharged. .
A gas discharge sleeve 20 is disposed in the vicinity of the gas discharge port 19.

A cylindrical gas rectifying cylinder 21 is disposed above the surface of the silicon melt 3 (silicon melt surface 3 ′) so as to surround the silicon single crystal 10 being pulled up. The gas rectifying cylinder 21 is provided so as to extend from the ceiling portion of the main chamber 2 toward the silicon melt surface 3 ′.
Further, a ring-shaped heat shield member 22 is provided on the silicon melt surface side of the gas flow straightening cylinder 21.

The structure is such that the distance from the lower end (heat shielding member 22) of the gas flow straightening cylinder 21 to the silicon melt surface 3 ′ can be adjusted, or the heating center can be moved by driving the heater 12 in the vertical direction. It has become.
Optimal conditions such as the optimum structure of the hot zone in the main chamber 2 and the positional relationship between the silicon melt surface 3 ′ and the heat generation center of the heater 12 can be calculated and set by calculation of the thermal numerical analysis simulation software FEMAG. .

  Further, the gas guiding path can be formed by arranging the gas rectifying cylinder 21, the heat shield member 22, the peripheral heat insulating member 13, the gas discharge sleeve 20, and the like. The inert gas introduced from the gas inlet 18 passes through the gas induction path (that is, in the example shown in FIG. 1, inside the gas rectifying cylinder 21, between the heat shield member 22 and the silicon melt surface 3 ′). And between the heat shield member 22 and the crucible 4, between the peripheral heat insulating member 13 and the crucible 4, and through the inside of the gas discharge sleeve 20).

The materials of the gas flow straightening cylinder 21, the peripheral heat insulating member 13 (the inner shield 15, the heat shield 14, the upper shield heat insulating material 16, the upper shield 17), the gas discharge sleeve 20, and the like are not particularly limited, but are made of graphite. be able to. Furthermore, the heater 12, the graphite crucible 6, and the support shaft 11 can also be made of graphite.
And in these graphite parts, the silicon vapor generated from the silicon melt 3 in the crucible 4 and contacting the Si vapor or SiO gas flowing through the gas guiding path, where the silicon deposit or silicon oxide deposit is formed, for example, Here, a silicon nitride film is applied and formed on the surface of the gas discharge sleeve 20.
Needless to say, a silicon nitride film can be appropriately coated and formed on portions other than the gas discharge sleeve 20 (such as the inner shield 15 and the upper shield 17 of the peripheral heat insulating member 13).

  Next, a method for producing a single crystal by the CZ method of the present invention will be described. Here, a case where a silicon single crystal is manufactured using the silicon single crystal manufacturing apparatus 1 shown in FIG. 1 will be described. However, as described above, the present invention is not limited to a silicon single crystal. In the present invention, a compound semiconductor single crystal is used. Other single crystals can also be manufactured by the CZ method.

(Application of silicon nitride film to graphite parts)
First, before the silicon single crystal manufacturing apparatus 1 is operated, a paint containing silicon nitride is applied to an arbitrary portion of the graphite part used in the furnace, and a silicon nitride film is formed on the surface of the graphite part.
During operation of the silicon single crystal manufacturing apparatus 1, Si vapor and SiO gas are generated from the silicon melt 3, and these deposits (adhesives) are formed on the surface of the graphite part in the low temperature part in the furnace. However, by forming a silicon nitride film in advance, it is possible to prevent the formation of a direct deposit on the surface of the graphite component. And, as will be described later, since the deposited material can be easily removed by peeling off the silicon nitride film, the deposited material remains unremoved from the surface of the graphite component as in the past, and the graphite component and the deposited material are deposited. Cracks due to differences in the coefficient of thermal expansion of objects do not occur. As a result, it contributes to a dramatic improvement in the life of graphite parts. Moreover, since the lifetime is extended, the replacement frequency of the graphite parts can be suppressed, and the cost of the apparatus and the single crystal to be grown can be reduced.

  Also, the location where the silicon nitride film is applied and formed is not particularly limited, but it forms a graphite part where silicon deposits or silicon oxide deposits are easily formed by contact with Si vapor or SiO gas from the silicon melt. It is effective to target. For example, as described above, a relatively low temperature portion such as the gas discharge sleeve 20 in the gas guiding path through which SiO vapor or the like flows can be cited. Of course, the present invention is not limited to this, and a silicon nitride film can be applied and formed at other locations, for example, the inner shield 15 and the upper shield 17 of the peripheral heat insulating member 13 as necessary.

  In addition, in the silicon single crystal manufacturing apparatus 1 by the CZ method, the graphite parts as described above are located downstream of the crucible 4 in the process of flowing Si vapor and SiO gas discharged from the surface of the silicon melt 3. By applying and forming the silicon nitride film, it is possible to prevent a decrease in the purity of the silicon melt 3. This is because if it is downstream of the crucible 4, it can be prevented that the silicon nitride film to which impurities are attached is mixed with the silicon melt 3 even when the silicon nitride film is peeled off.

  Moreover, the silicon nitride film on the surface of the graphite part formed by coating using a paint containing silicon nitride is not strong, although it is fixed on the graphite part. After the operation of the silicon single crystal manufacturing apparatus 1 is completed, it can be easily peeled off from the surface of the graphite part. Therefore, even when deposits such as deposits of Si vapor or SiO gas are formed on the silicon nitride film. They can be removed together with the silicon nitride film.

Moreover, the coating material containing silicon nitride to be used can be, for example, a polyvinyl alcohol aqueous solution in which polyvinyl alcohol is dissolved in water as a binder, and silicon nitride powder dispersed in the aqueous solution. With such a paint, a silicon nitride film can be easily formed by coating.
The ratio of each component in the paint is not particularly limited. For example, polyvinyl alcohol can be dissolved in water so as to be 1 to 10 wt%, and can be changed depending on the desired viscosity of the paint. The silicon nitride powder to be used is a particle having an average particle diameter of 0.65 μm, and 5 to 55 wt% of the powder is used with respect to the binder, and can be changed depending on a desired paint viscosity and film density.

  The silicon nitride film thickness is not particularly limited, and can be, for example, 10 μm or more. In the step of removing the deposit, which will be described later, the deposit can be removed together with the film by peeling off the extreme surface layer of the silicon nitride film, that is, part of the film. May be formed relatively thick in advance. In this way, the silicon nitride film can still remain even after many removal steps, and the labor for coating and forming the silicon nitride film can be saved.

  When the silicon single crystal manufacturing apparatus 1 is in operation, the temperature of the low temperature part in the apparatus is sufficiently high as the thermal decomposition temperature of polyvinyl alcohol. On the surface of the graphite part to which the paint containing silicon nitride is applied, it is considered that polyvinyl alcohol hardly remains after the operation of the silicon single crystal manufacturing apparatus 1 is completed. In the state where the polyvinyl alcohol has been removed, the remaining silicon nitride is very weakly fixed to the surface of the graphite part. Therefore, it can be easily peeled off by rubbing and sucking with a vacuum cleaner with a brush, for example. For this reason, silicon deposits or silicon oxide deposits by Si vapor or SiO gas generated on the silicon nitride film can be easily separated from the surface of the graphite component at the end of the operation of the silicon single crystal manufacturing apparatus 1. .

  The means for applying is not particularly limited, but can be easily formed by using a brush or a spray. A large-scale apparatus is not necessary, and it is preferable because it does not require labor and cost.

(Single crystal growth)
Polycrystalline silicon is charged into the crucible 4 of the silicon single crystal manufacturing apparatus 1 and filled. At this time, a desired resistivity controlling dopant such as phosphorus, boron, arsenic, antimony, gallium, germanium, and aluminum, which determines the resistivity of the silicon single crystal, is also added. In addition to the dopant for controlling the resistivity, nitrogen or carbon may be doped depending on the application.
While a vacuum pump (not shown) is operated and exhausted from the gas exhaust port 19, argon gas is introduced from the gas introduction port 18 to replace the inside of the apparatus with an argon atmosphere. Then, the silicon melt 3 is obtained by heating and melting the polycrystalline silicon with the heater 12.
Next, the seed crystal 9 is immersed in the silicon melt 3 and then pulled, and a rod-shaped silicon single crystal 10 is grown by the CZ method.

(Confirmation and removal of deposits)
After growing the single crystal, the surface state of the silicon nitride film is confirmed.
At this time, when deposits such as silicon deposits are confirmed on the surface, at least a part of the silicon nitride film is peeled off, thereby removing deposits on the film surface. As described above, since the surface layer of the silicon nitride film can be easily peeled off, the deposits can be easily removed. Then, after removing the deposits so that no extraneous matter is deposited on the silicon nitride film, the next silicon single crystal is grown.
If the surface of the graphite part itself is exposed by peeling off the silicon nitride film in this removing step, a silicon nitride film is applied again and then the next silicon single crystal is grown.

  On the other hand, when no deposit is confirmed on the surface of the silicon nitride film, the next single crystal can be grown as it is without performing the removal of the silicon nitride film as described above.

As described above, in the present invention, since the single crystal is grown in a state where the silicon nitride film is applied and formed on the graphite component in the furnace, deposits such as silicon deposits are directly formed on the surface of the graphite component. Can be easily prevented without cost. Furthermore, even if deposits are formed on the surface of the silicon nitride film, the deposits can be easily removed.
Therefore, it is possible to easily and inexpensively prevent the graphite component from being cracked due to the deposits formed on the surface as in the prior art, and thus the life of the graphite component can be greatly extended.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
A silicon single crystal is grown by the manufacturing method of the present invention using a silicon single crystal manufacturing apparatus 1 by the CZ method as shown in FIG.
At this time, Ar gas is allowed to flow as an inert gas from the gas inlet 18 at the top of the main chamber 2. This inert gas flows along the gas guiding path. That is, the inert gas is first guided to the silicon melt surface 3 ′ through the gas rectifying cylinder 21 and the silicon single crystal 10 to be grown. The inert gas flows through a guide path formed by the heat shield member 22 disposed immediately above the silicon melt 3 and the silicon melt surface 3 ′ under reduced pressure, and further, the inner wall of the crucible 4 and the outside of the heat shield member 22. And is discharged out of the crucible 4 through a guide path formed by.
Further, an upper shield 17 and an upper shield heat insulating material 16 protruding from the heat shield 14 and the inner shield 15 are disposed above the graphite heater 12. The inert gas is forcibly exhausted from the gas discharge port 19 by a vacuum pump (not shown).

  Accordingly, the Si vapor and SiO gas discharged from the silicon melt surface 3 ′ flow toward the gas discharge port 19 through a guide path formed by the outer wall of the graphite crucible 6, the lower portion of the upper shield 17, and the inner shield 15. . Formation of a deposit by contact with Si vapor or SiO gas occurs on a graphite part installed in the process of flowing the gas.

Therefore, in this example, with respect to the graphite gas discharge sleeve 20 in which the formation of the above-mentioned deposit is particularly seen, a silicon nitride film is formed by spraying a paint containing silicon nitride on the entire outer surface and inner surface by spraying. A silicon single crystal was grown.
A paint in which 7 wt% of polyvinyl alcohol was dissolved in 170 ml of water as a binder and 55 wt% of silicon nitride powder was dispersed in the binder was used.

  In addition, every time a silicon single crystal is grown, the surface of the silicon nitride film is observed, and when the deposit is confirmed, the deposit is removed together with the extreme surface layer of the silicon nitride film with a brush, and then the next silicon single crystal Nurtured. When the deposited material was not confirmed, the next silicon single crystal was grown without performing any treatment as it was and without peeling. And the mass of the gas discharge sleeve before and behind operation was measured. This was repeated for each operation.

(Comparative example)
Unlike the example, a silicon nitride film was not formed, and a graphite gas-exposed gas discharge sleeve was provided. Otherwise, the silicon single crystal was grown in the same manner as in the example, and the gas exhaust sleeve before and after the operation was grown. The mass was measured. This was repeated for each operation.

FIG. 2 shows the relationship of the rate of increase in mass with respect to the use time of the sample graphite parts (gas discharge sleeve) of the comparative example and the example.
In the comparative example, although removal of the deposit was attempted after the operation, it could not be completely removed, and the deposit was stacked for each operation, and the mass of the gas discharge sleeve was increased.
On the other hand, in the Example which implemented this invention, since the deposit was removed with the silicon nitride film after the operation, the mass of the gas discharge sleeve has not increased.

In both the comparative example and the example, the silicon single crystal was repeatedly grown under the same conditions as described above until the gas discharge sleeve was cracked.
FIG. 3 shows a comparison of life indices of the gas discharge sleeves of the comparative example and the example. As shown in FIG. 3, the result was 3.8 times that of the comparative example.
As can be seen from the above results, conventionally, it was difficult to remove the deposit on the graphite part. However, according to the present invention, the deposit can be removed. It is possible to suppress the occurrence of cracks in the graphite part due to the difference in thermal expansion coefficient between the graphite part and the deposit, and the life of the graphite part 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 substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  In the embodiment, the case where a silicon nitride film coated and formed on a graphite part used in a silicon single crystal manufacturing apparatus by the CZ method is used is not limited to this, but a paint containing silicon nitride is used. Any technique for extending the life of a graphite part by coating the surface of the graphite part is within the scope of the present invention. For example, there is a case where a silicon nitride film is applied and formed on a graphite part of an apparatus for manufacturing a compound semiconductor single crystal such as GaP by the CZ method.

DESCRIPTION OF SYMBOLS 1 ... Silicon single crystal manufacturing apparatus, 2 ... Main chamber, 3 ... Silicon melt,
3 '... Silicon melt surface, 4 ... Crucible, 5 ... Quartz crucible, 6 ... Graphite crucible,
7 ... Pulling chamber, 8 ... Pulling wire, 9 ... Seed crystal,
10 ... Silicon single crystal, 11 ... Support shaft, 12 ... Heating heater,
13 ... Peripheral heat insulating member, 14 ... Heat shield, 15 ... Inner shield,
16 ... Upper shield insulation material, 17 ... Upper shield,
18 ... gas inlet, 19 ... gas outlet, 20 ... gas outlet sleeve,
21 ... Gas flow straightening cylinder, 22 ... Heat insulation member.

Claims (5)

A single crystal production method for growing a single crystal from a raw material melt contained in a crucible disposed in a furnace of a single crystal production apparatus by a CZ method,
When growing the single crystal, a graphite component used in the furnace of the single crystal manufacturing apparatus is applied with a silicon nitride-containing coating formed on a surface thereof by applying a coating containing silicon nitride. Crystal manufacturing method. After growing the single crystal,
When deposits are confirmed on the surface of the silicon nitride film of the graphite component, after removing the deposits by peeling off at least part of the silicon nitride film, the next single crystal is grown,
2. The single crystal according to claim 1, wherein when a deposit is not confirmed on the surface of the silicon nitride film of the graphite component, the next single crystal is grown as it is without peeling off the silicon nitride film. Production method.   When a silicon single crystal is grown using the raw material melt as a silicon melt, the graphite component at a location where a silicon deposit or a silicon oxide deposit is formed by contact with Si vapor or SiO gas from the silicon melt. 3. The method for producing a single crystal according to claim 1, wherein the silicon nitride film is used.   The paint containing silicon nitride is obtained by dispersing silicon nitride powder in the aqueous polyvinyl alcohol solution using an aqueous polyvinyl alcohol solution as a binder. Single crystal manufacturing method.   The method for producing a single crystal according to any one of claims 1 to 4, wherein the coating containing silicon nitride is applied by using a brush or a spray.

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