JP2010132489A - Method for producing silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silicon single crystal in which the productivity in producing a single crystal is improved by melting a seed crystal with good accuracy before moving to a crystal growing step, improving the accuracy of the diameter of the single crystal at the start of the crystal growing, and reusing the seed crystal to reduce the labor and time for replacing the seed crystal. <P>SOLUTION: In the method for producing the silicon single crystal by the CZ process, the seed crystal is melted while detecting the diameter of the tip part of the seed crystal with a CCD camera; when the detected seed crystal has a diameter that is large enough to move to the crystal growing step, the step moves to the crystal growing step; then, the single crystal is grown while detecting the diameter of the single crystal with the CCD camera; when the diameter of the detected single crystal is less than the diameter required for pulling up a single crystal rod, the step moves to a separation step; the tip of the single crystal is formed into a sharpened shape before the single crystal is separated from the silicon melt; the temperature of the silicon melt is adjusted; and then the single crystal rod is again pulled up by using the separated single crystal as a new seed crystal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a silicon single crystal by growing a silicon single crystal rod by a Czochralski method (hereinafter referred to as “CZ method”) without performing necking using a silicon seed crystal.

  Conventionally, in the production of a silicon single crystal by the CZ method, single crystal silicon is used as a seed crystal, which is brought into contact with a silicon melt and then pulled at a low speed while rotating to grow a single crystal. At this time, when the seed crystal is brought into contact with the silicon melt, seeding (necking) is performed in order to eliminate dislocations generated in the seed crystal at a high density due to thermal shock, and then the crystal is formed until a desired diameter is obtained. Thickening and pulling up the silicon single crystal. Such seed drawing is widely known as the Dash Necking method, and is common knowledge when pulling up a silicon single crystal rod by the CZ method.

  That is, the shape of a seed crystal that has been conventionally used is, for example, as shown in FIGS. 6A and 6B, a cylindrical or prismatic single crystal having a diameter or a side of about 8 to 20 mm is set in a seed holder. The tip of the lower part that first contacts the silicon melt is a flat surface. In order to withstand the weight of a heavy single crystal rod and safely pull it up, it is difficult to reduce the thickness of the seed crystal below the above in view of the strength of the material.

  In the seed crystal having such a shape, since the heat capacity of the tip contacting the melt is large, a sudden temperature difference is generated in the crystal at the moment when the seed crystal contacts the melt, and slip dislocations are generated at a high density. . Therefore, the necking is necessary for erasing the dislocation and growing the single crystal, and the Dash Necking method for performing the necking is to narrow the diameter to about 3 mm after contacting the seed crystal with the silicon melt. This is a method in which a narrowed portion is formed, dislocations propagating from slip dislocations introduced into the seed crystal are eliminated, and a dislocation-free single crystal is obtained.

  However, even if various necking conditions are selected in such a method, it is necessary to narrow the minimum diameter to 5 to 6 mm in order to eliminate dislocation, and this minimum diameter is a large diameter of a recent silicon single crystal diameter. As a result, the strength of the single crystal rod, which has been increased in weight, is not sufficient to suspend and support the single crystal rod. There was a fear.

  Therefore, in order to solve such a problem, the crystal is made into a single crystal without forming the narrowed portion due to necking, which is the biggest problem in terms of strength. There has been disclosed a method capable of pulling up a crystal without using a complicated apparatus such as a crystal holding mechanism (see, for example, Patent Document 1).

  In this method, as shown in FIGS. 4 (a), (b), and (c), the shape of the tip that is brought into contact with the silicon melt as a seed crystal is a sharp shape or a shape in which the sharp tip is cut off. First, after gently bringing the tip of the seed crystal into contact with the silicon melt, the seed crystal is lowered at a low speed, or the silicon melt surface is raised at a low speed so that the tip of the seed crystal is Melt until the desired diameter is reached, then grow the silicon single crystal rod of the desired diameter without necking by raising the seed crystal at a low speed or lowering the silicon melt surface at a low speed This is a method for producing a silicon single crystal, and the minimum diameter near the seed crystal can be made larger than that of the Dash Necking method.

  However, as the silicon single crystal diameter has increased further in recent years, it is necessary to further increase the minimum diameter near the seed crystal in order to suspend and support a heavy single crystal rod. It was necessary to melt to a thicker part without dislocation.

  On the other hand, in general, the tip shape of the seed crystal having a sharp tip as described above varies. For example, depending on the finish of processing and etching, there are thin tip shapes (FIG. 4D) and some irregular shapes (FIG. 4E). In addition, the apex angle of the tip also varies. Therefore, even if the melting time and the melting rate are defined and the seed crystal is melted for the same time or the same length, the diameter of the seed crystal after melting varies. When the tip shape is thin, the diameter of the melted part may be smaller than the target, and this makes it impossible to pull up the heavy crystal after that, so it is necessary to replace the seeds and start over. Conversely, when the tip shape of the seed crystal is thick, the diameter of the melted part becomes thicker than the target, and in this case, the melting condition for melting without dislocation becomes difficult, and slip dislocation becomes difficult. It is not a good idea to melt to an extra diameter relative to the required minimum diameter.

  Further, it is known that the temperature condition of the silicon melt is important for melting the seed crystal (see, for example, Patent Document 2). However, it is difficult to set the optimum melt surface temperature correctly, and when it is set to a lower temperature, it takes time for the seed crystal to melt, and the possibility that slip dislocation occurs in the seed crystal increases. Accordingly, it is desirable that the temperature at the time of melting the tip of the seed crystal is sufficiently high, but a minimum diameter portion is formed during crystal growth after melting the seed crystal (see, for example, Patent Document 3). For this reason, when the temperature condition of the melt is too high, the minimum diameter may be smaller than the desired minimum diameter, and the strength to suspend and support the single crystal rod is insufficient.

Furthermore, in the CZ method in which necking is not performed, when the seed crystal is dislocated in the contact and melting process, it is impossible to grow the single crystal again from the same seed crystal. Therefore, it is necessary to exchange seed crystals.
Further, when the diameter is expanded while the minimum diameter is smaller than the desired diameter, it is necessary to melt the grown crystal again, and slip dislocations always occur at this time. Further, since slip dislocation occurs even when the crystal is cut off during the growth, it is necessary to exchange the seed crystal in such a case.

Therefore, when slip dislocation occurs in the seed crystal, it is necessary to replace the seed crystal. Therefore, a plurality of seed crystals are prepared in the seed exchange chamber where the seed crystal can be easily exchanged, and the seed crystal is replaced. Simplification is disclosed (for example, see Patent Document 4).
By this method, it is possible to reduce the labor of exchanging the seed crystal, but even in that case, the seed crystal cannot be reused and is discarded. In order to replace the seed crystal, the seed crystal and the seed chuck are gradually wound up from a high temperature state immediately above the melt, the chamber is opened, and further, the seed crystal is replaced, and the seed crystal is replaced again. Since the operation of contacting the melt surface is repeated, it takes time and effort, and the productivity of the single crystal is reduced.

Japanese Patent Laid-Open No. 10-203898 JP 2001-106593 A International Publication No. WO01 / 063026 Pamphlet Japanese Patent No. 3770287

  The present invention provides a method for producing a silicon single crystal without performing necking by the CZ method. In this method, the seed crystal is accurately melted to a desired diameter, transferred to a crystal growth step with good reproducibility, and the crystal growth is started. Improves the accuracy of the single crystal diameter to prevent the single crystal diameter from becoming smaller than the diameter required for pulling the single crystal rod, and the single crystal diameter is necessary for pulling the single crystal rod Even when the diameter is smaller than the desired diameter, the seed crystal can be reused to prevent the discarding of the seed crystal, reducing the labor and time for the replacement of the seed crystal, and the productivity of manufacturing the single crystal. It aims at providing the manufacturing method of the silicon single crystal which improves this.

  In order to solve the above problems, the present invention provides a method for producing a silicon single crystal by pulling up a single crystal rod by the Czochralski method, and at least a silicon seed crystal having a sharp tip or a shape having a sharp tip cut off. Using a silicon seed crystal, lowering the seed crystal or raising the silicon melt surface to bring the tip of the seed crystal into contact with the silicon melt and then melting the seed crystal And after the seed crystal melting step, the seed crystal is raised or the silicon melt surface is lowered to grow a silicon single crystal without performing necking, In the seed crystal melting step, the diameter of the tip of the seed crystal is detected by a CCD camera, the seed crystal is melted, and the diameter of the detected tip of the seed crystal is the crystal growth process. When the diameter reaches a diameter that can be transferred to, the seed crystal melting step is terminated and the crystal growth step is performed, and then, in the crystal growth step, the portion of the portion where the single crystal and the silicon melt are in contact with each other The single crystal is grown while detecting the diameter of the single crystal with the CCD camera. If the diameter of the detected single crystal is larger than the diameter necessary for pulling up the single crystal rod, the crystal growth process is continued. When the single crystal rod is pulled up and the diameter of the detected single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth process is terminated and the single crystal is separated from the silicon melt. The separation step is performed, and in the separation step, the single crystal is pulled up so that the tip of the single crystal has a pointed shape, and the single crystal is separated from the silicon melt, and the separation is performed. The single crystal is held on the surface of the silicon melt to complete the separation step, and then the temperature of the silicon melt is adjusted, and then the separated single crystal is used as a new seed crystal to again melt the seed crystal. A method for producing a silicon single crystal is provided, wherein the single crystal rod is pulled up by performing a step and a crystal growth step.

  Thus, in the seed crystal melting step, the diameter of the tip of the seed crystal is detected by the CCD camera, the seed crystal is melted, and the detected diameter of the tip of the seed crystal becomes a diameter that can be transferred to the crystal growth step. At this point, the seed crystal melting process is terminated and the process proceeds to the crystal growth process, so that the seed crystal can be accurately melted to the desired diameter even if the tip shape varies for each seed crystal used. Can do. Therefore, it is possible to move to the crystal growth process with good reproducibility. In the crystal growth process, the accuracy of the diameter of the single crystal at the start of crystal growth is improved, and the diameter of the single crystal is necessary for pulling up the single crystal rod. It is possible to manufacture a silicon single crystal while preventing it from becoming thinner than the diameter.

  Also, in the crystal growth process, the single crystal is grown while detecting the diameter of the single crystal where the single crystal is in contact with the silicon melt with a CCD camera, and the diameter of the detected single crystal is necessary for pulling up the single crystal rod. If the diameter is less than the required diameter, the crystal growth process is terminated and the process proceeds to the separation process. In the separation process, the single crystal is pulled up so that the tip of the single crystal has a pointed shape, and the single crystal is made into silicon. By separating from the melt, the single crystal can be separated without dislocation. Further, the separated single crystal can be reused by using the separated single crystal as a new seed crystal and performing the seed crystal melting step and the crystal growing step again and pulling up the single crystal rod. Further, in the separation step, by holding the separated single crystal on the silicon melt surface, the step conventionally performed for exchanging the seed crystal can be omitted. For this reason, even if the diameter of the single crystal becomes thinner and needs to be redone, it is possible to prevent the seed crystal from being discarded and reduce the labor and time for the replacement of the seed crystal, thereby increasing the productivity of single crystal production. Can be improved.

  Further, in the production method of the present invention, in the seed crystal melting step, the seed crystal melting step is terminated when the diameter of the detected tip of the seed crystal becomes a diameter that can be transferred to the crystal growth step. Transition to the crystal growth step, and in the crystal growth step, if the diameter of the detected single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth step is terminated and the separation is performed. It is preferable to automatically shift to the process (claim 2).

  Thus, in the seed crystal melting step, when the detected diameter of the tip of the seed crystal becomes a diameter that can be transferred to the crystal growth step, the seed crystal melting step is terminated and the crystal growth step is started. By carrying out automatically, even if the shape of the tip varies for each seed crystal to be used, it is possible to accurately determine that the diameter of the molten seed crystal has become a diameter that can be transferred to the crystal growth process. Further, the seed crystal is not melted to a thickness more than necessary. Therefore, it can transfer to a crystal growth process efficiently with good reproducibility.

  Also, in the crystal growth process, if the detected diameter of the single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth process is terminated and the process proceeds to the separation process. It is possible to quickly determine that the diameter of the crystal has become smaller than the diameter necessary for pulling up the single crystal rod, and to proceed to the separation step before the diameter of the single crystal starts to increase. Therefore, it is possible to prevent the crystal growth process from being unnecessarily continued and to improve the productivity of single crystal production.

In the production method of the present invention, in the seed crystal melting step, the seed crystal is melted by automatically controlling the melting rate of the seed crystal based on the detected diameter of the tip of the seed crystal. (Claim 3).
In this way, the melting of the seed crystal is performed by automatically controlling the melting rate of the seed crystal based on the detected diameter of the tip of the seed crystal, so that the shape of the tip varies for each seed crystal to be used. However, the seed crystal can be melted to a desired diameter while continuing the condition that slip dislocation is difficult to enter.

Furthermore, in the manufacturing method of the present invention, in the detaching step, it is preferable that the single crystal is separated from the silicon melt such that the tip of the separated single crystal has a conical shape. ).
Thus, in the separation step, the single crystal can be separated from the silicon melt by separating the single crystal without dislocation by making the tip of the separated single crystal have a conical shape. Moreover, when the separated single crystal has a conical tip, the separated single crystal can be melted in contact with the silicon melt without dislocation when the separated single crystal is reused as a new seed crystal.

In this case, in the separation step, the separation of the single crystal from the silicon melt is preferably performed when the pulling speed of the single crystal is gradually increased and the pulling speed is 1 mm / min or more. (Claim 5).
Thus, in the separation step, the separation of the single crystal from the silicon melt is performed when the pulling speed of the single crystal is gradually increased and the pulling speed is 1 mm / min or more, thereby ensuring the single crystal. It is possible to make the tip of the cone shape dislocation-free. Therefore, the separated single crystal can be reliably reused as a new seed crystal, and the seed crystal can be prevented from being discarded.

Further, in the separation step, the single crystal is pulled up by detecting the diameter of the single crystal at a portion where the single crystal and the silicon melt are in contact with the CCD camera, and detecting the diameter of the single crystal desired. Preferably, the pulling speed of the single crystal is automatically controlled in accordance with the pulled length of the single crystal so as to have a diameter of (Claim 6).
As described above, in the separation step, the single crystal is pulled up so that the diameter of the single crystal at the contact portion between the single crystal and the silicon melt is detected by the CCD camera, and the detected single crystal has a desired diameter. In addition, by automatically controlling the pulling speed of the single crystal according to the pulled length of the single crystal, the tip of the single crystal can be easily pointed, especially conical. Can do. Therefore, the easily separated single crystal can be used as a reusable seed crystal, and the labor and time for exchanging the seed crystal can be reduced, thereby improving the productivity of manufacturing the single crystal.

  As described above, according to the present invention, in a method for producing a silicon single crystal without necking, using a seed crystal with a sharp tip or a seed crystal with a sharp tip cut off by the CZ method, The seed crystal is melted while detecting the tip diameter of the seed crystal with a CCD camera, and the seed crystal melting process is terminated when the detected diameter of the tip of the seed crystal becomes a diameter that can be transferred to the crystal growth process. By moving to the crystal growth step, the seed crystal is accurately melted to the desired diameter, transferred to the crystal growth step with good reproducibility, and the accuracy of the diameter of the single crystal at the start of crystal growth is improved, It is possible to prevent the diameter of the single crystal from becoming smaller than the diameter necessary for pulling up the single crystal rod. In the crystal growth step, the single crystal is grown while detecting the diameter of the single crystal with a CCD camera. If the detected single crystal has a diameter smaller than that required for pulling up the single crystal rod, the crystal growth step And the process proceeds to the separation process.In the separation process, the single crystal is lifted so that the tip of the single crystal has a pointed shape, and the single crystal is separated from the silicon melt. The separated single crystal can be separated as a new seed crystal, and the separated single crystal is reused by pulling up the single crystal rod by performing the seed crystal melting process and the crystal growing process again. be able to. Further, in the separation step, by holding the separated single crystal on the silicon melt surface, the step conventionally performed for exchanging the seed crystal can be omitted. For this reason, it is possible to prevent the seed crystal from being discarded, reduce the labor and time for the replacement work of the seed crystal, and improve the productivity of manufacturing the single crystal.

Hereinafter, the present invention will be described more specifically.
As described above, a method of manufacturing a silicon single crystal without necking using a silicon seed crystal having a sharp tip has been disclosed in order to cope with the pulling of a single crystal rod having a large diameter and a high weight. . However, the shape of the tip varies depending on the seed crystal used in general, and when the melting time of the seed crystal is specified and melted for the same time, if the tip shape is thin, the diameter of the melted part is When the tip of the seed crystal is thick, the diameter of the melted part becomes thicker than the target and slip dislocation occurs. There was something to do. For this reason, it may not be possible to produce a silicon single crystal under desired conditions. The seed crystal was again replaced, the temperature of the silicon melt was adjusted, and the silicon single crystal was produced again from the beginning. There has been a problem of cost and a decrease in productivity of silicon single crystals.

  Therefore, the present inventors use a silicon seed crystal having a sharp tip to manufacture a silicon single crystal without necking, and even if there is a variation in the shape of the seed crystal tip, To melt the seed crystal well to the desired diameter and to reuse the seed crystal without exchanging the seed crystal when the diameter of the grown single crystal is less than the diameter required for pulling up the single crystal rod The inventors tried to manufacture a silicon single crystal by performing the following steps.

  Specifically, as shown in the flowchart of FIG. 1, the manufacturing process is a seed crystal melting process, a crystal growth process, and a separation process. Then, in the seed crystal melting step, the diameter of the tip of the seed crystal is detected by a CCD camera while the seed crystal is melted. As shown in FIG. Judging when it became the diameter which can transfer to a growth process, the seed crystal melting process was complete | finished and it shifted to the crystal growth process. Here, the “diameter that can be transferred to the crystal growth process” is the diameter of the melted seed crystal set by the total weight of the silicon single crystal rod to be grown thereafter, and can withstand the total weight of the grown single crystal rod. In addition, the diameter is set to a diameter that can ensure the load resistance of the grown single crystal even if the crystal becomes thin in the first half of the crystal growth process. For example, when the weight of the grown single crystal is 400 kg, the diameter of the molten seed crystal is required to be 5.6 mm or more from the viewpoint of load resistance. .5mm or more is set. On the other hand, the “diameter necessary for pulling up the single crystal rod” is a diameter obtained by adding a safety factor to a diameter that can withstand the total weight of the grown silicon single crystal rod. Therefore, the diameter that can be transferred to the crystal growth process> the diameter necessary for pulling up the single crystal rod.

  As a result, even if the shape of the tip of the seed crystal varies for each used seed crystal, the seed crystal can be accurately melted to a desired diameter and can be transferred to the crystal growth process with good reproducibility. I understood.

  Further, in the crystal growth step shown in FIG. 1, the single crystal is grown while detecting the diameter of the single crystal with a CCD camera. As shown in FIG. 1D, the detected single crystal has a diameter of the single crystal rod. When the diameter was larger than the diameter necessary for pulling, the crystal growth was continued as it was to grow a single crystal rod. When the detected diameter of the single crystal was less than the diameter necessary for pulling up the single crystal rod, the crystal growth process was terminated and the process shifted to the separation process. In this separation step, as shown in FIG. 1 (f), the single crystal was pulled up and separated from the silicon melt while increasing the pulling speed of the single crystal, and separated as shown in FIG. 1 (g). The single crystal was held on the silicon melt surface to complete the separation step. Thereafter, as shown in FIG. 1 (h), after adjusting the temperature of the silicon melt, the separated single crystal is used as a new seed crystal, and a seed crystal melting step and a crystal growth step are performed again to obtain a single crystal rod. The silicon single crystal was manufactured by pulling up.

  As a result, in the separation step, as shown in FIG. 1 (f), the single crystal is pulled up while increasing the pulling speed of the single crystal so that the tip of the single crystal has a pointed shape. The crystal can be separated from the silicon melt without dislocation, and the single crystal can be reused as a new seed crystal.

  At this time, when the pulling speed of the single crystal is gradually increased and the pulling speed is 1 mm / min or more, the single crystal is separated from the silicon melt, so that the tip of the single crystal is surely dislocation-free. It turned out that it can be made into a cone shape.

  Also, in the separation step, as shown in FIG. 1 (g), by holding the separated single crystal on the surface of the silicon melt, it is possible to omit the step conventionally performed for exchanging the seed crystal. It has been found that the productivity and the productivity of single crystal production can be improved by reducing the labor and time of the exchange work of the seed crystal.

The present invention has been completed based on the above findings and discoveries. Hereinafter, the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a flow diagram of a method for producing a silicon single crystal according to the present invention. FIG. 2 is a schematic view of a single crystal pulling apparatus used in the method for producing a silicon single crystal of the present invention.

  As shown in FIG. 2A or 2B, the seed crystal 5 attached to the seed holder 1 or the separated single crystal 10 is suspended by a wire 8 in the pull chamber 4. Then, the seed crystal 5 and the separated single crystal 10 can be lowered or raised while being rotated by a wire rotation up / down mechanism (not shown). In the base chamber 7, a crucible 6 containing a silicon melt 3 obtained by melting a silicon raw material with a heater 2 is disposed. Further, a CCD camera 9 for detecting the diameter of the seed crystal being melted and the diameter of the single crystal being grown is installed outside the base chamber 7.

In the method for producing a silicon single crystal of the present invention, a single crystal pulling apparatus 20 as shown in FIG.
Below, the manufacturing method of the silicon single crystal in this invention is demonstrated, referring FIG.1, FIG.2 (a), FIG.2 (b).

  First, a silicon raw material is put into a crucible 6 as shown in FIG. 2A and melted to form a silicon melt 3. Then, the seed crystal 5 having a sharp tip is gently brought into contact with the silicon melt 3 (FIG. 1A), and the seed crystal melting step is started. Thereafter, the seed crystal 5 is lowered or the silicon melt surface is raised (the crucible 6 is raised) to melt the seed crystal (FIG. 1B). At this time, the seed crystal is melted while the diameter of the tip of the seed crystal is detected by the CCD camera 9. Then, it is determined when the detected diameter of the tip of the seed crystal has reached a diameter that can be transferred to the crystal growth process, and the seed crystal melting process is terminated and the process proceeds to the crystal growth process (FIG. 1 (c)). .

  Subsequently, in the crystal growth step, the single crystal is grown while the diameter of the single crystal is detected by the CCD camera 9, and the detected single crystal diameter is used to pull up the single crystal rod as shown in FIG. 1 (d). Determine whether the diameter is greater than or less than the required diameter. If the result indicates that the diameter of the single crystal is greater than the diameter required for pulling up the single crystal rod, continue the crystal growth process and replace the single crystal rod. Pull up to complete the crystal growth process (FIG. 1E).

On the other hand, in the determination of FIG. 1D, when the detected diameter of the single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth process is terminated and the process proceeds to the separation process.
Subsequently, in the separation step, the single crystal is pulled up while increasing the pulling speed of the single crystal to separate the single crystal from the silicon melt (FIG. 1 (f)), and the separated single crystal is removed from the silicon melt surface. The separation process is finished while holding the top (FIG. 1 (g)). At this time, as shown in FIG. 2B, the separated single crystal 10 is held above the melt surface of the silicon melt 3 as a new seed crystal.

  Then, after adjusting the temperature of the silicon melt 3 with the heater 2 (FIG. 1 (h)), the seed crystal melting step and the crystal growth step are performed again using the separated single crystal 10 as a new seed crystal. Then, in the judgment of FIG. 1D of the crystal growth process, when the diameter of the single crystal is equal to or larger than the diameter necessary for pulling up the single crystal rod, the crystal growth process is continued and the single crystal rod is pulled up. When the crystal growth process is completed (FIG. 1 (e)) and the diameter of the single crystal is less than the diameter necessary for pulling up the single crystal rod, the process proceeds to the separation process again, and the temperature of the silicon melt is increased. After the adjustment, a seed crystal melting step and a crystal growth step are performed to manufacture a silicon single crystal.

  Thus, in the seed crystal melting step, the diameter of the tip of the seed crystal is detected by the CCD camera while the seed crystal is melted, and as shown in FIG. By determining when the diameter has reached a diameter that can be transferred to the crystal growth process, the seed crystal melting process is completed and the process proceeds to the crystal growth process. Well, the seed crystal can be melted to the desired diameter. Therefore, it is possible to move to the crystal growth process with good reproducibility. In the crystal growth process, the accuracy of the diameter of the single crystal at the start of crystal growth is improved, and the diameter of the single crystal is necessary for pulling up the single crystal rod. It is possible to manufacture a silicon single crystal while preventing it from becoming thinner than the diameter.

  Further, in the crystal growth step, the single crystal is grown while detecting the diameter of the single crystal with a CCD camera, and the detected single crystal diameter is necessary for pulling up the single crystal rod as shown in FIG. If the diameter of the detected single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth process is terminated and the process proceeds to the separation process. Then, in the separation step, as shown in FIG. 1 (f), the single crystal is pulled up while increasing the pulling speed of the single crystal, and the single crystal is separated from the silicon melt. As a result, the single crystal can be separated from the silicon melt without dislocation. Therefore, the separated single crystal can be reused as a new seed crystal, and the seed crystal can be prevented from being discarded.

  Further, as shown in FIG. 1 (g), by holding the separated single crystal on the silicon melt surface, a process conventionally performed for exchanging the seed crystal, such as a seed crystal or a seed chuck, is performed. From the high-temperature state immediately above the melt, the process of gradually winding up, opening the pull chamber, allowing to further cool, replacing the seed crystal, and omitting the step of gradually lowering the seed crystal on the melt surface from there is omitted. it can. Therefore, it is possible to reduce the labor and time for the replacement work of the seed crystal, and improve the productivity of manufacturing the single crystal.

Moreover, in the manufacturing method of this invention, it is preferable to perform automatically to transfer to a crystal growth process from FIG.1 (c), and a cutting | disconnection process from FIG.1 (d).
In this way, by automatically shifting from FIG. 1C to the crystal growth process, the diameter of the molten seed crystal shifts to the crystal growth process even if the shape of the tip varies for each seed crystal used. It is possible to accurately determine that the diameter has become possible and shift to the next crystal growth step with good reproducibility. Further, by automatically shifting from FIG. 1 (d) to the separation step, it is quickly determined that the diameter of the single crystal is smaller than the diameter necessary for pulling up the single crystal rod, and in the crystal growth step, It is possible to proceed to the separation step before the diameter expansion of the single crystal starts to increase. Therefore, it is possible to prevent the crystal growth process from being unnecessarily continued and to improve the productivity of single crystal production.

Further, in the seed crystal melting step, the seed crystal is preferably melted by automatically controlling the melting rate of the seed crystal based on the detected diameter of the tip of the seed crystal.
As a result, even if the shape of the tip varies for each seed crystal to be used, the seed crystal can be melted to a desired diameter while continuing the condition in which slip dislocation does not easily occur in each seed crystal.

In the separation step, it is preferable that the single crystal is separated from the silicon melt such that the tip of the separated single crystal has a conical shape.
Thus, the single crystal can be separated without dislocation, and when reused as a new seed crystal, it can be melted in contact with the silicon melt without dislocation.

Further, in FIG. 1 (f) of the separation step, it is preferable that the separation of the single crystal from the silicon melt is performed when the pulling speed of the single crystal is gradually increased and the pulling speed is 1 mm / min or more. .
This ensures that the tip of the single crystal has a conical shape. Therefore, the separated single crystal can be reliably reused as a new seed crystal, and the seed crystal can be prevented from being discarded.

Further, in the separation step, the single crystal is pulled up by detecting the diameter of the single crystal at the portion where the single crystal and the silicon melt are in contact with each other so that the detected diameter of the single crystal becomes a desired diameter. It is preferable that the pulling speed of the single crystal is automatically controlled according to the length of the single crystal pulled.
By this, the front-end | tip part of a single crystal can be easily made into a cone shape. Therefore, the easily separated single crystal can be used as a reusable seed crystal, and the labor and time for exchanging the seed crystal can be reduced, thereby improving the productivity of manufacturing the single crystal.

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these.
(Example)
In order to produce a silicon single crystal having a diameter of 300 mm by the CZ method, a seed crystal having a tip portion with a sharp tip with a 20 mm side prism shape as shown in FIG. 4B was prepared. And the manufacture of the single crystal was repeated in the following procedures as shown in the flowchart of FIG. 1 using the pulling apparatus as shown in FIG.

  First, in the seed crystal melting step, 500 kg of silicon raw material is charged into a crucible 6 as shown in FIG. 2A and melted to form a silicon melt 3. A seed crystal as shown in FIG. 5 was gently brought into contact with the silicon melt 3 (FIG. 1 (a)). Thereafter, the seed crystal 5 was lowered to melt the seed crystal 5 (FIG. 1B). At this time, while detecting the diameter of the tip of the seed crystal 5 with the CCD camera 9, the seed crystal 5 is melted, and the detected diameter of the tip of the seed crystal 5 can be transferred to the crystal growth step. After confirming that the seed crystal melting process was completed, the seed crystal melting process was terminated, and the process proceeds to the next crystal growth process (FIG. 1C).

  Next, in the crystal growth step, the single crystal was grown while detecting the diameter of the single crystal with the CCD camera 9. Then, as shown in FIG. 1 (d), as a result of determining whether the detected single crystal diameter is 6.5 mm or more necessary for pulling up the single crystal rod, it is determined that out of 40 pulls. The single crystal rod could be grown as it was 39 times, but in one pulling up, the diameter of the detected single crystal became smaller than 6.5 mm, so the crystal growth process was completed and the separation process was completed. It moved to.

  In this separation step, the single crystal pulling rate is gradually increased, the single crystal is pulled up, and the single crystal is separated from the silicon melt when the pulling rate reaches 1.0 mm / min (FIG. 1). (F)). At this time, the separated single crystal had a conical tip as shown in FIG. Thereafter, the separated single crystal was held on the surface of the silicon melt to complete the separation process (FIG. 1 (g)). At this time, as shown in FIG. 2B, the separated single crystal 10 was held at about 1 cm on the silicon melt surface.

  Then, after adjusting the temperature of the silicon melt (FIG. 1 (h)), the separated single crystal is used as a new seed crystal, and the seed crystal melting step and the crystal growth step are performed again. In the determination of d), since the diameter of the single crystal was 6.6 mm or more, the crystal growth process was continued and the single crystal rod was pulled up to complete the crystal growth process (FIG. 1 (e)). A crystal rod was produced.

At this time, the time required for the production of the silicon single crystal was an additional 3 hours compared to the case where the separation step was not performed. Moreover, it was confirmed that the produced silicon single crystal was dislocation free.
Further, when a silicon single crystal was manufactured in the same process as shown in FIG. 1 using a seed crystal having a shape as shown in FIGS. However, as shown in FIG. 3 (a) or FIG. 3 (b), the separated single crystal had a conical tip. When the presence or absence of slip dislocations in the separated single crystal was observed, no slip dislocations were observed.

(Comparative example)
In order to manufacture a silicon single crystal having a diameter of 300 mm by the CZ method, a single crystal was manufactured by the following procedure using a general pulling apparatus as shown in FIG.

  First, as a seed crystal melting step, 500 kg of silicon raw material is put into a crucible as shown in FIG. 7A and melted to form a silicon melt, and the seed crystal is gently brought into contact with the silicon melt. The seed crystal was melted. Then, after the seed crystal was melted for a specified time, the seed crystal melting step was terminated and the next crystal growth step was started.

  Next, in the crystal growth step, the single crystal was grown while detecting the diameter of the single crystal with a CCD camera. The target minimum diameter at this time was 6.5 mm, but the seed crystal was cut off because the diameter began to gradually increase with 6.3 mm as the minimum value.

  Subsequently, as shown in FIG. 7B, the seed crystal was slowly rolled up, the gate valve was closed, the pull chamber was returned to atmospheric pressure, and the seed holder and the seed crystal were allowed to cool. Thereafter, the seed crystal was exchanged, the pull chamber was replaced, and after pressure equalization, the gate valve was opened. And it prepared for performing a seed crystal melting process again.

At this time, 8 hours or more had already passed since the first seed crystal melting step was started. Thereafter, a seed crystal melting step and a crystal growth step were performed to manufacture a silicon single crystal.
Thereafter, the production of the silicon single crystal was repeated in the same process, and the minimum diameter of the single crystal was measured.

  Here, FIG. 5 shows the measurement results of the diameter of the seed crystal and the minimum diameter of the grown single crystal at the time of transition to the crystal growth process of the example and the comparative example. From FIG. 5, the example shows a small variation in the diameter of the seed crystal at the time of transition to the crystal growth process, and the minimum diameter of the single crystal is necessary for pulling up the single crystal rod except for one time when the separation process is performed. It can be seen that the diameter is 6.5 mm or more. On the other hand, in the comparative example, it can be seen that there is a large variation in the diameter of the seed crystal during the transition to the crystal growth process, and there are about half of the cases where the minimum diameter of the single crystal is less than 6.5 mm.

  From the above, according to the method for producing a silicon single crystal of the present invention, the seed crystal can be accurately melted to a desired diameter and transferred to the crystal growth process with good reproducibility. By improving the accuracy of the diameter of the crystal, it is possible to manufacture a silicon single crystal by preventing the diameter of the single crystal from becoming smaller than that required for pulling up the single crystal rod.

  In addition, even if the diameter of the single crystal is smaller than the diameter necessary for pulling up the single crystal rod, the single crystal can be separated without dislocation in the separation step, so the separated single crystal Can be reused as a new seed crystal to prevent the discard of the seed crystal, reduce the labor and time of the replacement work of the seed crystal, and improve the productivity of the production of the single crystal.

  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.

It is a flowchart of the manufacturing method of the silicon single crystal of this invention. It is the schematic which shows an example of the pulling apparatus of the single crystal used in the manufacturing method of the silicon single crystal of this invention. It is the figure which showed the shape of the single crystal cut | disconnected in the manufacturing method of the silicon single crystal of this invention. It is the figure which showed the shape of the seed crystal used in the manufacturing method of the silicon single crystal which does not perform necking. It is a figure which shows the measurement result of the diameter of the seed crystal at the time of the crystal growth process transfer of an Example and a comparative example, and the minimum diameter of the grown single crystal. It is the figure which showed the shape of the seed crystal used in the manufacturing method of the conventional silicon single crystal. It is the schematic of the pulling apparatus of the single crystal used in the manufacturing method of the conventional silicon single crystal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Seed holder, 2 ... Heater, 3 ... Silicon melt, 4 ... Pull chamber, 5 ... Seed crystal, 6 ... Crucible, 7 ... Base chamber, 8 ... Wire, 9 ... CCD camera, 10 ... Separated single crystal, 20: Single crystal pulling device.

Claims (6)

In a method for producing a silicon single crystal by pulling up a single crystal rod by the Czochralski method, at least the silicon seed crystal having a sharp tip or a silicon seed crystal having a sharp tip is used to form the seed crystal. Or lowering the silicon melt surface to bring the tip of the seed crystal into contact with the silicon melt and then melting the seed crystal, and after the seed crystal melting step, A crystal growth step of raising the seed crystal or lowering the silicon melt surface to grow a silicon single crystal without performing necking,
In the seed crystal melting step, the diameter of the tip of the seed crystal is detected by a CCD camera, the seed crystal is melted, and the diameter of the detected tip of the seed crystal can be transferred to the crystal growth step. The seed crystal melting step is finished and the crystal growth step is started,
Then, in the crystal growth step, the single crystal is grown while detecting the diameter of the single crystal at a portion where the single crystal and the silicon melt are in contact with the CCD camera, and the diameter of the detected single crystal is If the diameter is larger than the diameter necessary for pulling up the single crystal rod, the crystal growth process is continued and the single crystal rod is pulled up.
When the detected diameter of the single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth process is terminated, and the process proceeds to a separation process for separating the single crystal from the silicon melt. ,
In the separation step, the single crystal is pulled up so that the tip of the single crystal has a pointed shape, the single crystal is separated from the silicon melt, and the separated single crystal is separated from the silicon melt surface. To complete the separation step,
Then, after adjusting the temperature of the silicon melt, the separated single crystal is used as a new seed crystal, and a seed crystal melting step and a crystal growth step are performed again to pull up the single crystal rod. A method for producing a single crystal.   In the seed crystal melting step, when the diameter of the tip of the detected seed crystal reaches a diameter that can be transferred to the crystal growth step, the seed crystal melting step is terminated and the crystal growth step is started. In the crystal growth step, when the diameter of the detected single crystal is less than the diameter necessary for pulling up the single crystal rod, the crystal growth step is terminated and the process proceeds to the separation step. The method for producing a silicon single crystal according to claim 1.   In the seed crystal melting step, the melting of the seed crystal is performed by automatically controlling the melting rate of the seed crystal based on the detected diameter of the tip of the seed crystal. The method for producing a silicon single crystal according to claim 2.   4. The separation process according to claim 1, wherein, in the separation step, the single crystal is separated from the silicon melt such that a tip of the separated single crystal has a conical shape. A method for producing a silicon single crystal according to Item.   In the separation step, the separation of the single crystal from the silicon melt is performed when the pulling speed of the single crystal is gradually increased and the pulling speed is 1 mm / min or more. The method for producing a silicon single crystal according to any one of claims 1 to 4.   In the detaching step, the single crystal is pulled up by detecting the diameter of the single crystal at a portion where the single crystal and the silicon melt are in contact with each other while the CCD camera detects the diameter of the single crystal. 6. The method according to claim 1, wherein the pulling speed of the single crystal is automatically controlled in accordance with the pulled length of the single crystal. A method for producing a silicon single crystal.

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