JPH10324596A - Production of silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process capable of growing a single crystal rod without executing necking again even if a first dislocation generation occurs once in the process for producing the silicon single crystal by a Czochralski method without executing the necking. SOLUTION: This process consists in producing the silicon single crystal by the Czochralski method without executing the necking by using a seed crystal having the shape of its front end consisting of a pointed shape or the shape formed by cutting of its pointed end. In such a case, the silicon seed crystal is replaced with a fresh silicon seed crystal having the desired front end shape and the fresh silicon seed crystal is again brought into contact with a silicon melt and is melted in case the seed crystal or the single crystal causes the first dislocation generation in a stage for bringing the seed crystal into contact with the silicon melt, then melting the seed crystal until a desired diameter is obtd. on a stage for gradually lifting the seed crystal then growing the silicon single crystal rod of a desired diameter without executing the necking. The silicon single crystal is thus produced by the Czochralski method without executing the necking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon single crystal by the Czochralski method (CZ method), which is a so-called seed drawing (necking).
The present invention relates to a method for producing a silicon single crystal without performing the method described above, and relates to a method for exchanging a seed crystal when a dislocation occurs in the seed crystal or the single crystal in the middle, and again producing a single crystal.

[0002]

2. Description of the Related Art Conventionally, in the production of a silicon single crystal by the Czochralski method, a single crystal silicon is used as a seed crystal, which is brought into contact with a silicon melt and then slowly pulled up while being rotated. Growing sticks. At this time, when the seed crystal is brought into contact with the silicon melt, seed drawing (necking) is performed in order to eliminate dislocations generated in the seed crystal at high density due to thermal shock, and then the crystal is thickened until a desired diameter is obtained. The silicon single crystal is pulled up. Such a seed aperture is DashNec
It is widely known as the king method, and is a common sense when pulling a silicon single crystal rod by the Czochralski method.

That is, as shown in FIGS. 4 (A) and 4 (B), the shape of a conventionally used seed crystal is, for example, cylindrical or prismatic having a diameter or a side of about 8 to 20 mm as a seed holder. A notch portion for setting is provided, and the shape of the lower end that comes into contact with the silicon melt first is a flat surface. Then, in order to withstand the weight of the heavy single crystal rod and safely raise it, it is difficult to make the thickness of the seed crystal smaller than the above.

[0004] In the seed crystal having such a shape, since the heat capacity of the tip in contact with the melt is large, a sudden temperature difference occurs in the crystal at the moment when the seed crystal comes into contact with the melt, and slip dislocations are generated at a high density. To be generated. Therefore, necking is necessary to eliminate the dislocation and grow a single crystal.

In the Dash Necking method, after a seed crystal is brought into contact with a silicon melt, the diameter of the seed crystal is once reduced to about 3 mm to form a narrowed portion, and dislocations propagating from slip dislocations introduced into the seed crystal are eliminated. To obtain a dislocation-free single crystal.

However, in such a method, even if various necking conditions are selected, it is necessary to narrow down to a minimum diameter of 5 to 6 mm in order to eliminate dislocations. The strength is not enough to suspend the weighted single crystal rod and support it, and during the pulling of the crystal rod, there is a risk of causing a serious accident such as the thin narrowed part breaking and the single crystal rod falling. .

In recent years, a method using a crystal holding mechanism has been developed for pulling a large-diameter, high-weight single crystal rod (see, for example, Japanese Patent Publication No. 5-65477). In this method, since necking is indispensable for dislocation-free as described above, the strength of the seed drawing part cannot be strengthened, and instead, the growing crystal rod is directly mechanically held. is there.

However, since such a method directly holds a single crystal rod which grows slowly while rotating at a high temperature, the apparatus becomes complicated and expensive, and a problem of heat resistance also arises. . In addition, it is very difficult to actually grasp the grown crystal without giving any vibration, etc., which may cause the grown crystal to be polycrystallized, or may have a complicated mechanism such as rotation and sliding directly above the high-temperature silicon melt. Therefore, there are various problems such as contamination of the crystal with heavy metal impurities.

In order to solve such a problem, the present applicant has previously described Japanese Patent Application Laid-Open No. 5-139880 and Japanese Patent Application No. 8-871.
No. 87 was proposed. In the present invention, the tip of the seed crystal has a wedge shape or a shape having a hollow portion,
By reducing as much as possible the slip dislocation that enters when the seed crystal comes into contact with the silicon melt, it is possible to eliminate dislocation even if the diameter of the constricted portion is relatively large, thereby improving the strength of the constricted portion. .

According to this method, the thickness of the narrowed portion can be increased, so that the strength of the narrowed portion can be improved to some extent. However, necking is performed to form a narrowed portion having slip dislocation. Increasingly large diameter,
For pulling a single crystal rod that is longer, for example, 150 kg or more, the strength may be insufficient, and a fundamental solution has not been reached.

In order to solve such a problem, the present applicant has made it possible to form a single crystal of a crystal without forming a constricted portion due to necking, which is the most problematic in strength, and has a large diameter. A method for producing a silicon single crystal and a silicon seed crystal used for the method, which can pull up a long and heavy silicon single crystal extremely easily without using a complicated device such as a crystal holding mechanism, Succeeded in development and proposed earlier (Japanese Patent Application No. 9-17 / 1997)
687).

In this method, as shown in FIGS. 3 (A) to 3 (D), the tip portion to be brought into contact with the silicon melt as a seed crystal has a sharp shape or a shape obtained by cutting off a sharp tip. First, after the tip of the seed crystal is brought into contact with the silicon melt, the seed crystal is lowered at a low speed to melt the tip of the seed crystal until a desired thickness is obtained. Is slowly raised, and a silicon single crystal rod having a desired diameter is grown without necking.

In this method, since necking is not performed, it is an extremely excellent method that can fundamentally solve the above-mentioned various problems caused by forming the narrowed portion.

[0014]

However, in the Czochralski method, there is a problem that dislocations occur in the grown single crystal rod due to various factors. In particular, in the method without necking, not only the step of growing a silicon single crystal rod of a desired diameter, after contacting the seed crystal with the silicon melt, there is a step of melting until the desired thickness, The seed crystal itself may be dislocated.

In such a case, in the usual Czochralski method, the already grown single crystal or the drawn portion is melted again, a drawn portion is formed again, and the crystal is pulled up.
You only have to train.

However, in the Czochralski method in which necking is not performed, not only when the seed crystal is dislocated during the contacting and melting process of the seed crystal, but also when the grown single crystal is dislocated, the recrystallization is not repeated. Since dislocations reach the seed crystal during the melting process, it is impossible to grow a single crystal from the same seed crystal again without necking. That is, in the Czochralski method without necking, once dislocations are generated in a seed crystal or a single crystal, it cannot be redone from the same seed crystal.

In this case, when the seed crystal or the single crystal is once dislocated, after melting the already grown crystal part, a constricted part is formed by a usual Czochralski method to form a single crystal rod. Although it is possible to grow, it is not possible to solve various problems, such as strength, associated with forming the above-described constricted portion.

In view of the above, the present invention has been made in view of the above-described problems. In a method of manufacturing a silicon single crystal by the Czochralski method without necking, even if a seed crystal or a single crystal is once dislocated. It is an object of the present invention to provide a method capable of growing a single crystal rod without performing necking again even in the case where the Czochralski method is performed without necking.

[0019]

According to a first aspect of the present invention, there is provided a seed crystal having a pointed tip or a pointed tip. In a method of manufacturing a silicon single crystal by Czochralski method without necking,
A step of bringing the seed crystal into contact with the silicon melt and melting it to a desired thickness, or thereafter, slowly raising the seed crystal to grow a silicon single crystal rod having a desired diameter without necking. In the step, when the seed crystal or the single crystal is dislocated, the seed crystal is replaced with a new seed crystal having a desired tip shape, and the new seed crystal is brought into contact with the silicon melt again and melted. A method for producing a silicon single crystal, which comprises producing a silicon single crystal by the Czochralski method without necking.

As described above, even when the seed crystal or the single crystal is dislocated in the step of contacting and melting the seed crystal with the silicon melt, or thereafter, the step of growing a silicon single crystal rod having a desired diameter. Even so, by exchanging a new seed crystal having a desired tip shape, that is, a tip shape having a sharp shape or a shape with a sharp tip cut off, the new seed crystal is again converted into a silicon melt. A silicon single crystal can be manufactured by the Czochralski method without contacting, melting and necking.

In this case, the replacement with a new seed crystal can be performed after the seed crystal is moved into the pull chamber, the gate valve is closed, and the pull chamber is opened.

As described above, if the replacement with a new seed crystal is performed using the pull chamber for taking out the crystal, there is no need to install a special device, and the seed crystal can be replaced very simply and reliably. .

Further, as described in claim 3, the replacement with a new seed crystal is performed by moving the seed crystal into the seed crystal exchange chamber, closing the gate valve, and opening the seed crystal exchange chamber. It may be performed.

As described above, if a new seed crystal is exchanged using the seed crystal exchange chamber, the seed crystal can be exchanged quickly, so that the seed crystal can be exchanged very simply and efficiently. Can be done.

Further, as described in claim 4, the replacement with a new seed crystal may use a spare seed crystal set in the chamber in advance.

As described above, if replacement with a new seed crystal is performed by using a spare seed crystal set in the chamber in advance, the operation of opening and closing the chamber is not required, so that it is even easier. The seed crystal can be exchanged efficiently.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. First, a method of manufacturing a silicon single crystal by the Czochralski method without necking will be briefly described.This method involves bringing a seed crystal into contact with a silicon melt and slowly pulling it while rotating it. According to the method for producing a silicon single crystal by the Czochralski method of growing a silicon single crystal rod, the shape of the tip portion of the seed crystal that is brought into contact with the silicon melt has a sharp shape or a shape obtained by cutting the sharp tip. Using a seed crystal, the tip of the seed crystal is first brought into contact with a silicon melt, and then the seed crystal is lowered at a low speed to melt the tip of the seed crystal until a desired thickness is obtained. Thereafter, the seed crystal is slowly raised to grow a silicon single crystal rod having a desired diameter without necking.
This is a method for producing a silicon single crystal.

In this method, although the seed crystal contacts and melts from the silicon melt without being in contact with the silicon melt, the area of the first contact portion is small and the heat capacity is small. However, thermal shock due to contact with the silicon melt is not applied to the seed crystal, and then the seed crystal is slowly lowered, so that the contact area gradually increases. No gradient is formed. Therefore, the seed crystal can be brought into contact with and melted on silicon without dislocation.

That is, in the production of a silicon single crystal rod by the Czochralski method, the shape of the tip to be brought into contact with the silicon melt of the seed crystal is a sharp shape having a small contact area or a shape obtained by cutting the sharp tip. Using a seed crystal, the tip of the seed crystal is brought into direct contact with the silicon melt, and then slowly lowered at a low speed, so that the tip of the seed crystal is Melting until the desired thickness that can withstand the weight, then slowly raising the seed crystal and thickening the single crystal to the desired diameter as it is, can grow a silicon single crystal rod without necking.

In the Czochralski method which does not perform necking, it is necessary that the tip of the seed crystal used has a sharp shape or a shape obtained by cutting off a sharp tip, for example, as shown in FIG. There is. With such a shape, when the tip of the seed crystal first contacts the silicon melt, the contact area with the melt is small, and the heat capacity of the tip is small. Because no gradient is formed, no slip dislocation is introduced.

Then, if the seed crystal is slowly lowered and the tip of the seed crystal is melted to a desired thickness, the contact area between the seed crystal and the melt in the melt gradually increases. The seed crystal can be melted without forming a sharp temperature gradient in the seed crystal, and no slip dislocation is introduced into the seed crystal even during melting.

In the Czochralski method without such necking, it is essential that no slip dislocation is introduced into the seed crystal. Therefore, if a seed crystal with a sharp tip is brought into contact with the silicon melt and slip dislocations are introduced into the seed crystal during melting, it is no longer possible to perform the Czochralski method, which does not neck again with the seed crystal. It is.

Further, even when slip dislocation does not occur during contact and melting of the seed crystal, in the Czochralski method, the dislocation of the crystal rod occurs for various reasons during the subsequent growth of the single crystal rod. There are cases. In that case, in the usual Czochralski method, the dislocation-converted single crystal rod is melted and the crystal rod is pulled up and grown again. It propagates along the gradient to the portion that has already grown as a single crystal, and eventually reaches the seed crystal. Therefore,
Even when dislocations are formed during the growth of such a single crystal rod, once the dislocations occur in the crystal, the Czochralski method that does not perform necking using the seed crystal cannot be performed again. .

Therefore, in the present invention, in the step of contacting and melting a seed crystal with a silicon melt, or thereafter, in the step of growing a silicon single crystal rod having a desired diameter, when the seed crystal or the single crystal is dislocated. By replacing the seed crystal with a new seed crystal having a desired tip shape, the new seed crystal is brought into contact with the silicon melt again, melted, and a silicon single crystal is formed by the Czochralski method without necking. Decided to manufacture.

If the seed crystal is replaced with a new one as described above, the new seed crystal has no slip dislocation and has a desired shape. Therefore, it is necessary to perform the Czochralski method without necking again. Can be done.

Therefore, the new seed crystal to be exchanged is
The seed crystal must have a shape capable of performing the Czochralski method without necking, that is, a seed crystal having a pointed tip or a pointed tip as shown in FIG.

When the seed crystal is exchanged, of course, it is preferable to exchange the seed crystal after melting the dislocated crystal. This is because if the seed crystal is exchanged with the dislocated crystal, the amount of the silicon melt is reduced, which is wasteful.

The replacement of a seed crystal with a new seed crystal can be performed by moving the seed crystal into a pull chamber for taking out a crystal, closing the gate valve, and opening the pull chamber.

FIG. 1A is a schematic view of an apparatus for producing a silicon single crystal by the generally used Czochralski method. The procedure for exchanging the seed crystal according to the present invention will be described with reference to FIG. Then, the grown single crystal is immersed in the silicon melt 3 to melt the crystal rod to the seed crystal tip. When the melting is completed, the seed holder 1 is raised by the wire rotating up and down mechanism, and the seed crystal 5 is moved into the pull chamber 4. In this case, when the dislocation position is at the time of contact / melting of the seed crystal,
The seed holder 1 is immediately moved to the pull chamber 4 without melting the crystal rod.

When the seed crystal 5 together with the seed holder 1 is located in the pull chamber 4, the gate valve 6 is closed and the pull chamber 4 and the base chamber 7 are shut off. After the inside of the pull chamber 4 is brought to normal pressure, a crystal take-out door (not shown) of the pull chamber 4 is opened. The dislocated seed crystal is removed and replaced with a new seed crystal (having a sharp tip or a sharp tip).

After exchanging the seed crystal, the door for taking out the crystal of the pull chamber 4 is closed, and the inside of the pull chamber is evacuated and then replaced with an inert gas atmosphere. The gas atmosphere and pressure are made the same as those of the base chamber 7, and the gate valve 6 is opened. Then, the seed crystal 1 is lowered by lowering the seed holder 1 by the wire rotating and lowering mechanism, and the Czochralski method without necking is performed again.

As described above, if replacement with a new seed crystal is performed using the pull chamber 4 for taking out a crystal, there is no need to install a special device such as a chamber for seed crystal exchange.
The seed crystal can be exchanged very easily and reliably.

In the second embodiment, a method for replacing a seed crystal with a new seed crystal is performed after the seed crystal is moved into the seed crystal exchange chamber, the gate valve is closed, and the seed crystal exchange chamber is opened. You may do it.

This method can be performed by, for example, an apparatus as shown in FIG. That is, in this apparatus, a smaller bellows chamber 8 for exchanging a seed crystal is further provided on a pull chamber 4 for taking out a crystal of a usual Czochralski method apparatus, and is shut off from a lower chamber by a gate valve 9. You can do it.

With such an apparatus, the replacement of the seed crystal may be performed in substantially the same procedure as described above, but the chamber for moving and replacing the seed crystal is referred to as a seed crystal replacement chamber 8 and this chamber is located below. A gate valve 9 is used to shut off the chamber. The seed crystal exchange chamber 8 needs only to have a space for accommodating the seed crystal 5 and the seed holder 1 and can be made small.

That is, the procedure of exchanging the seed crystal when using the apparatus having such a seed crystal exchange chamber 8 will be described. When the growing single crystal rod is dislocated, the seed holder 1 is placed in the upper box 2. The crystal rod is melted down to the tip of the seed crystal by dipping the grown single crystal in the silicon melt 3 by lowering the wire rotating up / down mechanism (not shown) stored therein. When the melting is completed, the seed holder 1 is lifted by the wire rotating up and down mechanism, and the seed crystal 5 is moved into the seed crystal exchange chamber 8. In this case, if the dislocation is at the time of contact / melting of the seed crystal, the seed holder 1 is immediately moved to the seed crystal exchange chamber 8 without melting the crystal.

When the seed crystal 5 together with the seed holder 1 is located in the seed crystal exchange chamber 8, the gate valve 9 is closed to shut off the seed crystal exchange chamber 8 and the pull chamber 4. After the inside of the seed crystal exchange chamber 8 is brought to normal pressure, the bellows chamber is contracted to open the seed crystal exchange chamber 8. The dislocated seed crystal is removed and replaced with a new seed crystal (having a sharp tip or a sharp tip).

After the replacement of the seed crystal, the bellows is extended to shut off the seed crystal exchange chamber 8 from the outside air, and the inside of the seed crystal exchange chamber is evacuated and then replaced with an inert gas atmosphere. The gas atmosphere and pressure are made the same as those of the pull chamber 4 and the base chamber 7, and the gate valve 9 is opened. Then, the seed crystal is lowered by lowering the seed holder 1 by the wire rotating and lowering mechanism, and the Czochralski method without necking is performed again.

As described above, if the replacement with a new seed crystal is performed using the seed crystal exchange chamber, the capacity of the seed crystal exchange chamber is small. Since the active gas and the like can be saved, and the seed crystal can be replaced quickly, the seed crystal can be replaced very simply and efficiently.

In a third embodiment of the present invention, a spare seed crystal set in a chamber may be used as a method for replacing the seed crystal with a new seed crystal. This means that a plurality of seed crystals are set in the chamber at one time.

This method can be carried out, for example, by devising the form of the seed holder 1 as shown in FIG. That is, the seed holder 1 is rotatably supported by a bifurcated holder holding jig 11 provided at the tip of the wire 10 and can hold two upper and lower seed crystals 5, 5 '. . Fig. 1 shows other components
It may be the same as the conventional one shown in FIG.

Referring to FIG. 2 and FIG. 1A, a procedure for exchanging the seed crystal when using such a spare seed crystal will be described. When the growing single crystal rod is dislocated, the seed holder 1 is moved upward. Is lowered by a wire rotating and vertically moving mechanism (not shown) stored in the box 2, and the grown single crystal is immersed in a silicon melt to melt the crystal rod to the seed crystal tip. When the melting is completed, the seed holder 1 is lifted by the wire rotating and raising / lowering mechanism so that the tip of the seed crystal 5 is
Move to a position where it does not touch. In this case, if the dislocation position is at the time of contact / melting of the seed crystal, the seed crystal 5 and 5 ′ can be obtained by immediately raising the seed holder 1 and rotating the seed holder without melting the crystal. Is moved to a position where it does not contact the silicon melt 3.

At this position, the seed holder 1 is rotated so that the new seed crystal 5 'located at the upper part is disposed at the lower part in the vertical direction, thereby exchanging the seed crystal with a new seed crystal 5'. In this case, it is needless to say that the spare seed crystal 5 'set in advance has a shape with a sharp tip or a shape with a sharp tip cut off. When the replacement of the seed crystal is completed, the seed holder 1 is lowered by the wire rotating up / down mechanism, and the Czochralski method without necking is performed again.

As described above, if the replacement with a new seed crystal is performed by using a spare seed crystal set in the chamber in advance, the operation of opening and closing the chamber is not required, so that it is extremely short. The exchange can be performed in time, and the exchange of the seed crystal can be performed more easily and efficiently.

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

For example, the present invention is applicable not only to the ordinary Czochralski method but also to the MCZ method (Magnetic field applied Czochralski method) for applying a magnetic field when pulling a silicon single crystal.
It goes without saying that the term Czochralski method as used in the present description includes the MCZ method as well as the usual Czochralski method, as a matter of course applies to the crystal growth method.

Further, the method of exchanging a seed crystal for a new seed crystal has been described with reference to a specific apparatus form. However, the method of the present invention is not limited to being carried out only by an apparatus having these forms. The configuration mechanism is not limited as long as a similar method can be performed.

For example, the terms such as the pull chamber, the gate valve, and the seed crystal exchange chamber described in the embodiments of the present invention are not necessarily those in the form shown in the drawings, but may be any as long as they have the same function. , It is not bound by its name.

In the third embodiment of exchanging a new seed crystal, the case where two seed crystals are set in advance has been described by way of example. However, three or more seed crystals are set in advance. It goes without saying that you may be there.

[0060]

As described in detail above, the present invention relates to a method of manufacturing a silicon single crystal by the Czochralski method without necking, even when a seed crystal or a single crystal is once dislocated. However, since the seed crystal is replaced with a new seed crystal having a desired tip shape, a single crystal rod can be grown using this new seed crystal without necking again. Therefore, the success rate of the Czochralski method without necking can be improved by the present invention.

As a result, when pulling up a silicon single crystal rod by the conventional Czochralski method, the crystal can be monocrystallized without forming a seed drawing portion due to necking, which is the most problematic in strength. A large and long silicon single crystal having a large diameter and a long length can be pulled up very easily without using a complicated device such as a crystal holding mechanism.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a procedure for exchanging a seed crystal in the present invention. (A) In the case of performing with a conventional apparatus (first embodiment),
(B) A case of using an apparatus having a seed crystal exchange chamber (second embodiment).

FIG. 2 is an explanatory diagram for explaining a procedure of a third embodiment for exchanging a seed crystal in the present invention.

FIG. 3 is a perspective view showing a shape of a seed crystal used in the present invention. (A) a cylindrical seed crystal having a conical tip, (B) a quadrangular seed crystal having a pyramid tip, and (C) a conical tip having a tip cut horizontally. (D) A diagonally cut end with a conical tip.

FIG. 4 is a perspective view showing the shape of a conventional seed crystal. (A) Columnar, (B) Square prism.

[Explanation of symbols]

1 ... seed holder, 2 ... box, 3 ... silicon melt, 4 ... pull chamber, 5, 5 '... seed crystal,
6 gate valve, 7 base chamber,
8: chamber for seed crystal exchange, 9: gate valve, 10: wire, 11: holder holding jig.

Claims (4)

[Claims] 1. A method for producing a silicon single crystal by a Czochralski method without using necking, using a seed crystal having a pointed tip or a pointed tip, wherein the seed crystal is After contacting with the silicon melt, in the step of melting until the desired thickness, or thereafter, slowly raise the seed crystal, without necking, in the step of growing a silicon single crystal rod of a desired diameter, When the seed crystal or the single crystal is dislocated, the seed crystal is replaced with a new seed crystal having a desired tip shape, and the new seed crystal is brought into contact with the silicon melt again, melted, and necking is performed. A method for producing a silicon single crystal, which comprises producing a silicon single crystal by the Czochralski method without any problems. 2. The silicon single crystal according to claim 1, wherein the replacement with the new seed crystal is performed after moving the seed crystal into the pull chamber, closing the gate valve, and opening the pull chamber. Method for producing crystals. 3. The method according to claim 1, wherein the replacement with the new seed crystal is performed after moving the seed crystal into the seed crystal exchange chamber, closing the gate valve, and opening the seed crystal exchange chamber. A method for producing a silicon single crystal according to claim 1. 4. The method for producing a silicon single crystal according to claim 1, wherein the replacement with the new seed crystal uses a spare seed crystal set in a chamber in advance.