JPH10139585A - Single crystal pulling-up device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the device capable of safely pulling up the single crystal without causing falling of the crystal at the time of producing a single crystal having a great weight. SOLUTION: (1) This device is provided with: a pulling-up means 6 for forming a neck part 3e in a single crystal 3 to be pulled up while being rotated; a holding jig 10 for engaging the neck part 3e of the single crystal 3 with clamping members 11 and clamping the neck part 3e through the clamping members 11; and a holding jig pulling-up means 8 for elevating the holding jig 10 in conformity with the pulling-up rate of the single crystal pulling-up means 6, after engaging and clamping the neck part 3e of the single crystal 3. (2) In the device, the plural platelike clamping members 11 with which the neck part 3e of the single crystal 3 is engaged and which are used for clamping the neck part 3e in such a way that the clamping members 11 are upwardly opened when a diameter-increasing part of the single crystal neck part 3e passes through the insides of the clamping members 11 and then, downwardly closed when a diameter-decreasing part of the single crystal neck part 3e passes through the insides of the clamping members 11, is desirably placed and also, more desirably, at the time of engaging the neck part 3e with the clamping members 11, a conical engagement surface is formed in the central part of the clamping members 11 as a whole, where the neck part 3e is engaged with the plural clamping members 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulling apparatus for producing a single crystal by the Czochralski method (hereinafter, referred to as "CZ method"). The present invention relates to a single crystal pulling device that can be pulled safely without falling.

[0002]

2. Description of the Related Art There are various methods for producing a single crystal. Among them, the CZ method is widely applied in a method capable of industrial mass production for growing a silicon single crystal.
In the production of a single crystal by this method, the seed crystal is brought into contact with the surface of the melt of the crystal raw material contained in the crucible, and the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. Thereby, a single crystal in which the melt is solidified grows at the lower end of the seed crystal.

When a single crystal is produced by the CZ method,
When the seed crystal is brought into contact with the melt, it is necessary to completely remove dislocations generated by the thermal shock so that the dislocation does not reach the main body of the grown single crystal. Usually, as this measure, in order to eliminate dislocations from the crystal surface and make the single crystal dislocation-free,
A so-called "neck process" is employed in which the diameter is narrowed and elongated. At this time, the diameter of the neck portion necessary for eliminating dislocations is 3 to 4 mm, and its mechanical strength is about 200 kg.

Conventionally, the weight of a single crystal produced by the CZ method has been limited to about 120 to 130 kg, but in recent years there has been a strong demand for more efficient semiconductor production. And the weight of the single crystal becomes 2
Cases exceeding 00 kg have come to be assumed. As described above, the load that can be borne by the neck portion of the single crystal is limited, and if the single crystal becomes too heavy and torsion or bending stress is applied during pulling, the neck portion of the single crystal is broken and the single crystal is crucible. It may fall into the melt inside, causing damage to the lifting device, outflow of the melt, and even a steam explosion, which may lead to personal injury.

Therefore, in order to prevent accidents such as dropping during pulling, which are expected to occur frequently due to the increase in the weight of the single crystal,
A method of eliminating dislocations at a large-diameter neck portion or a method of mechanically holding a single crystal during pulling has been attempted, but proposals regarding the latter method have been made. For example, Japanese Patent Application Laid-Open No. 62-288191 discloses a basic concept of mechanically holding a single crystal by providing an engaging portion on the single crystal. Japanese Patent Application Laid-Open No. 295893 proposes a pulling apparatus in which the means for holding a single crystal is improved. That is, by adopting a structure in which an engaging step is formed on the upper part of the single crystal and this engaging step is engaged and gripped by a plurality of claws or a plurality of gripping means having the claws, The single crystal is prevented from falling. For this reason, the use of the proposed pulling apparatus makes it possible to pull up a single crystal reliably and safely even when pulling a heavy single crystal.

[0006]

In the pulling technique based on the CZ method, it is difficult to form a narrow portion having a uniform symmetry with respect to the pulling axis of the single crystal. However, when growing a single crystal while holding the single crystal in a state in which the constricted portion of the single crystal is displaced from the pulling axis, the circularity of the single crystal is impaired, and the accuracy of diameter control is reduced. . In addition, not only the quality problem described above, but also the engagement / grip is not uniformly performed by the gripping means, and the weight load of the single crystal is added only to the engaged gripping means, resulting in extremely poor stability. , May be disengaged. For this reason, in the lifting device disclosed in Japanese Patent Application Laid-Open No. 3-285893, a holding means for holding the engagement so as not to be disengaged is provided as a countermeasure for these, and the engagement and gripping of the gripping means is ensured. I have.

FIG. 6 is a view for explaining a means for holding a single crystal used in a pulling apparatus proposed in Japanese Patent Application Laid-Open No. 3-285893. That is, a constricted portion 3e is formed on the upper part of the single crystal 3 grown at the tip of the seed chuck 4 to form an engagement step, and this engagement step is formed into an L-shaped gripping lever having a plurality of claws 38. The structure supported by 39 is adopted. Then, the grip lever 39 is held by a ring 40 so that the support is not released when the grip lever is supported by the grip lever. By adopting such a gripping method, even when an uneven load is applied to the gripping lever 39, the single crystal 3 is prevented from dropping during the pulling by the gripping lever pulling wire 7.

[0008] Certainly, the proposed gripping means can prevent the single crystal from falling during pulling. However, since the engagement and gripping is performed by a plurality of claws, the single crystal is held by the point contact at the engagement step portion, so that significant stress concentration occurs. For this reason, unexpected breakage may occur at the engaging step portion of the single crystal, or the single crystal may be twisted during pulling and the single crystal may be greatly inclined, and the claws or grip holders may be disengaged and drop the single crystal. Is worried.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional pulling apparatus, ensures the engagement and holding of the constricted portion of the single crystal by the holding member, and further avoids stress concentration due to point contact. Therefore, an object of the present invention is to provide a single crystal pulling apparatus which can appropriately manufacture a single crystal without causing a fall accident even when pulling a heavy single crystal, and is excellent in safety. And

[0010]

In the single crystal pulling apparatus of the present invention, after the seed crystal is brought into contact with the melt surface by the single crystal pulling means, the seed crystal is pulled up while rotating to perform a neck process.
Next, the constricted portion is formed by increasing and decreasing the diameter of the single crystal, and the shoulder of the single crystal and the single crystal main body are grown. On the other hand, the weight increases with the progress of pulling the single crystal, but before reaching the limit of the load that can be borne by the neck portion of the single crystal, the constriction of the single crystal is removed by the gripping member provided on the holding jig. A structure is employed in which engagement and grip are performed, and thereafter, the process shifts to holding of a single crystal by holding jig lifting means. Further, when the single crystal is engaged and gripped by the gripping member, it is characterized in that stress concentration is prevented from being generated in the constricted portion of the single crystal due to engagement by point contact. Therefore, the gist of the present invention resides in the following single crystal pulling apparatus as shown in FIG.

That is, the diameter of the single crystal 3, which is pulled while being rotated, is increased and then reduced to form a constricted portion 3e.
And a holding jig 10 for engaging and gripping a constricted portion of the single crystal via a gripping member 11.
After engaging and gripping the constricted portion 3e of the single crystal with the gripping member 11, the holding jig lifting means 8 for raising the holding jig in synchronization with the pulling speed of the single crystal pulling means 6 is provided. A single crystal pulling apparatus characterized in that:

In the above single crystal pulling apparatus, when the holding jig is a plate-like gripping member and a portion for increasing the diameter of the single crystal passes through the inside of the plurality of gripping members from below to above, A gripping member is provided for opening the gripping member upward and then closing the gripping member downward when the portion for reducing the diameter of the single crystal passes upward from below to engage and grip the narrow portion of the single crystal. It is desirable.

Further, a conical engagement surface is formed at a central portion where the plurality of gripping members engage so that the outer periphery of the constricted portion of the single crystal can be uniformly engaged and gripped when the plurality of gripping members engage. It is more desirable to provide.

The term "plate-shaped gripping member" as used herein means a plate-shaped cross-section, as shown in FIGS. 2 and 4, which will be described later. It is composed of a contact portion having a shape of a circle.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a single crystal pulling apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view for explaining an example of the overall configuration of the apparatus of the present invention. As shown in FIG. 1, a crucible 1 is provided at a central position in a vacuum chamber (not shown), and a melt 2 in which polycrystalline silicon as a raw material is melted is held therein. A seed chuck 4 and a holding jig 10 are arranged above the crucible 1, and a single crystal pulling unit 6 for rotating and pulling up the silicon single crystal 3 and a unit for raising and lowering the holding jig 10 are further above the crucible 1. And a holding jig pulling means 8 which constitutes a pulling mechanism 9.

In the apparatus of the present invention, the single crystal pulling means 6
The single jig wire 5 wound by the holding jig and the two holding jig wires 7 wound by the holding jig pulling means 8 are vertically suspended, and they are independently raised and lowered. The pulling mechanism 9 composed of the single crystal pulling means 6 and the holding jig pulling means 8 is rotated in a certain direction by a structure (not shown) in order to rotate the single crystal at a predetermined speed in the pulling process. . For this reason, the single crystal pulling means 6 and the holding jig pulling means 8 are arranged in the same rotating system.

In the apparatus of the present invention, when the single crystal and the holding jig are pulled, the single crystal pulling means 6 is moved by the holding jig pulling means 8.
Because it is a separate system, even if the constriction of the single crystal deviates from the pulling axis, the axis deviation can be easily adjusted, the roundness of the single crystal is impaired, and the accuracy of diameter control Can be avoided. Further, as described above, since the single crystal pulling means 6 and the holding jig pulling means 8 are arranged in the same rotating system constituted by the pulling mechanism 9, the single crystal pulling means caused by the unstable crystal rotation. Troubles in growing the crystal can be prevented.

At the lower end of the single crystal wire 5, a seed chuck 4 for holding a single crystal seed 3a is attached, and by a pulling operation of a single crystal pulling means 6, a neck 3b and a portion 3c for increasing the diameter of the single crystal. (Hereinafter referred to as "diameter increasing part")
A constricted portion 3e composed of a portion 3d for reducing the diameter of the single crystal (hereinafter, referred to as a "reduced diameter portion") and a shoulder portion 3f are formed. On the other hand, a holding jig 10 is attached to the ends of the two holding jig wires 7, and the constricted portion 3 e of the single crystal is engaged and held by a holding member 11 provided on the inner peripheral surface of the holding jig 10. Is done.

FIG. 2 is a view for explaining a structural example of a gripping member provided on a holding jig in the apparatus of the present invention. Further, FIG. 4 of an embodiment described later shows a specific example of the dimensions of the gripping member. As is clear from these drawings, the holding member 11 is formed of a plate-like member, and is rotatably supported on the inner peripheral surface of the lower end of the holding jig 10. For this reason, around the pivot point
From the state where the gripping member 11 is opened so as to be vertical, the gripping member 11 can be turned 90 ° until it is held horizontal by the bottom plate of the holding jig 10 and becomes a closed state.

By adopting the plate-shaped gripping member having the above-described structure, the gripping member 11 is pushed up by the single-crystal diameter-increased portion 3c as the single crystal is pulled up, and the single-crystal diameter-increased portion is opened. Pass through 3c. Next, when the gripping member 11 passes through the reduced diameter portion 3d, the gripping member 11 is closed by its own weight, and engages with the narrow portion 3e of the single crystal as the diameter of the single crystal decreases. Thereafter, when the weight of the single crystal is applied to the gripping member 11, the self-clamping function of the gripping member 11 is exerted, and the gripping of the gripping member 11 at the constricted portion 3e is ensured.

FIG. 3 is a view for explaining the engagement / grasping state of the constricted portion of the single crystal by the holding jig and the gripping member shown by arrows AA in FIG. In the figure, two gripping members 11 are provided, and a conical engagement surface is arranged at the center in a state where these two gripping members 11 are engaged and gripped. Regarding the number of the gripping members 11 provided, in particular, the gripping members 11
It is not necessary to limit the number of
Any number of 3e may be used so that they can be sufficiently engaged and gripped.
As shown in FIG. 3, when engaging the plurality of holding members 11, a conical engagement is formed at the center of the plurality of holding members so that the outer periphery of the constricted portion of the single crystal can be uniformly engaged and held. It is desirable to provide a mating surface. By configuring the gripping member 11 such that the portion where the gripping member 11 engages with the single crystal 3 is in linear or planar contact with the single crystal, no stress concentration occurs in the constricted portion 3e of the single crystal, and the single crystal 3 has a large weight. Even if the crystal is pulled, it can be safely grown.

Next, a specific operation procedure will be described. At the start of pulling the single crystal, the holding jig lifting means 8 waits while holding the holding jig 10 upward. At least, holding jig
The lower end of 10 is held above single crystal seed 3a. On the other hand, the seed chuck 4 is attached to the tip of the single crystal pulling means 6.
The single crystal seed 3a attached via the contact is brought into contact with the center of the liquid surface of the silicon melt 2 to stabilize the melt. Thereafter, the single crystal pulling means 6 is operated to slowly raise the single crystal seed 3a while rotating, thereby forming the neck portion 3b. Next, the pulling speed of the single crystal is reduced to form the diameter-increased portion 3c of the single crystal, and then the pulling speed is increased to form the diameter-reduced portion 3d of the single crystal to form the single-crystal constricted portion 3e. .

After forming the constricted portion 3e of the single crystal, the diameter of the single crystal is increased again to form the shoulder 3f, and then the pulling speed and the rotating speed are adjusted to the steady condition to adjust the single crystal 3 having a predetermined diameter.
Move to the main body pulling.

When the weight of the single crystal to be pulled reaches a certain weight after the transition to steady single crystal pulling, or
At the time when a certain pulling length is reached, the holding jig 10 which has been waiting above is lowered until its lower end coincides with the reduced diameter portion 3d of the single crystal. In the descending stage, as described above, the gripping member 11 is pushed up by the single crystal diameter-increased portion 3c and opened to pass through the diameter-increased portion 3c. After that, the diameter reduction part 3d of the single crystal
The gripping member 11 is closed with the passage of, and the single crystal constricted portion 3e is engaged and gripped. After that, the holding jig lifting means 8
The holding jig 10 is synchronized with the pulling speed of the single crystal pulling means 6.
To rise.

Here, the holding mechanism 11 is lifted by holding the single crystal with the holding member 11 after the weight of the single crystal reaches a certain weight, that is, at least in the latter half of the pulling process. Good.

[0027]

EXAMPLES Hereinafter, the effects of the single crystal pulling apparatus of the present invention will be described based on specific examples (Examples of the present invention, Comparative Examples 1 to 3).

(Example of the Present Invention) Using the pulling apparatus shown in FIG. 1, a silicon single crystal having a diameter of 12 inches (305 mm) and a pulling length of 1000 mm was grown. At this time, 300 kg of polycrystalline silicon as a crystal raw material was charged.

FIG. 4 is a view showing the shape and specific dimensions of the holding jig used in the embodiment. At the start of pulling of the single crystal, the holding jig is held in an upper state and held. Was. On the other hand, the single crystal seed attached to the tip of the single crystal pulling means is brought into contact with the silicon melt 2, and thereafter the single crystal pulling means 6 is operated to slowly raise the single crystal seed while rotating it. A single crystal neck portion, a constricted portion and a shoulder portion having the shape and dimensions shown in FIG.

After shifting to pulling the main body of the single crystal, the pulling weight becomes
When the weight reached 100 kg, the holding jig was lowered, and the constricted portion of the single crystal was engaged and gripped by the gripping member to grow a total of 30 pieces, and this was used as a primary pull. Normally, when dislocations occur during the primary pulling, the dislocations are re-melted, that is, remelted and pulled again to make the final pulling. However, in the example of the present invention, since remelting cannot be performed, only the first pulling is performed and the final pulling is not performed.

Table 1 shows the results of the number of dislocations, the number of drops, and the total dislocation-free length of the grown single crystal when a total of 30 crystals were pulled.

(Comparative Example 1) As a comparative example of a mechanical holding method of a single crystal, a gripping means shown in FIG.
Using a holding jig proposed in Japanese Patent No. 5893, a silicon single crystal similar to that of the present invention was grown.

A single crystal neck portion having the shape and dimensions shown in FIG.
After forming the constricted part and shoulder, and moving to pulling the main body of the single crystal, when the pulling weight reaches 100 kg, the gripping lever with two claws is operated and the constriction of the single crystal is made with two claws. The parts were engaged and gripped, and a total of 30 plants were grown. Again, since remelting was not possible, final lifting was not performed, but only primary lifting was performed. Table 1 shows the pulling results at this time.

Comparative Example 2 As in the case of the present invention, a total of 30 silicon single crystals having a diameter of 12 inches (305 mm) and a pull length of 1000 mm were grown using the pulling apparatus shown in FIG. However, the single crystal neck shown in Fig. 5 (diameter 3mm, length 30mm)
Was formed, the shoulder was formed, and the main body of the single crystal was pulled without forming a constricted portion. Therefore, the holding jig used in the example of the present invention was not used at all. At this time, the primary lifting and the final lifting were performed, and the results were as shown in Table 1.
Shown in

Comparative Example 3 As in the case of the present invention, a total of 30 silicon single crystals having a diameter of 12 inches (305 mm) and a pull length of 1000 mm were grown using the pulling apparatus shown in FIG. However, after forming a large-diameter single crystal neck portion (diameter 8 mm, length 200 mm), a shoulder portion was formed and a main body of the single crystal was pulled without forming a constricted portion. Therefore, the holding jig used in the example of the present invention was not used at all. At this time, the primary lifting and the final lifting were performed, and the results were as shown in Table 1.
Shown in

[0036]

[Table 1]

As is clear from Table 1, in Comparative Example 1, three single crystals were dropped, and in Comparative Example 2, no holding jig was used. Further, in Comparative Example 3, although no drop occurred, all single crystals were dislocated due to the large diameter neck portion. On the other hand, in the example of the present invention, about five dislocations were formed, but no single crystal was dropped, and the total dislocation-free length of the grown single crystal was a good result.

[0038]

According to the single crystal pulling apparatus of the present invention, the engagement and grip of the constricted portion of the single crystal by the gripping member is ensured, and further, the stress concentration at the single crystal engaging portion is avoided. Even when pulling a heavy single crystal, the single crystal can be manufactured safely without causing a fall accident.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating an example of the overall configuration of a device of the present invention.

FIG. 2 is a diagram illustrating a structural example of a gripping member provided on a holding jig in the apparatus of the present invention.

FIG. 3 is a diagram illustrating a state in which a holding portion of the single crystal is engaged and gripped by a holding jig and a gripping member as viewed from arrows AA in FIG.

FIG. 4 is a view showing the shape and specific dimensions of a holding jig used in the embodiment.

FIG. 5 is a view showing shapes and dimensions of a single crystal neck, a constricted portion, and a shoulder formed in an example.

FIG. 6 is a view for explaining a means for holding a single crystal used in a pulling up device proposed in the prior application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crucible, 2 ... Melt, 3 ... Single crystal 3a ... Single crystal seed, 3b ... Neck part 3c ... Increased diameter part, 3d ... Reduced diameter part 3e ... Constriction part, 3f ... Shoulder part 4 ... Seed chuck, 5 ... Single crystal wire 6 ... Single crystal pulling means 7 ... Holding jig wire 8 ... Holding jig pulling means 9 ... Holding mechanism 10 ... Holding jig 11 ... Grip member 38 ... Claw 39 ... Grip lever 40 ... ring

Claims (3)

[Claims] 1. A single crystal pulling means for forming a constricted portion by increasing the diameter of a single crystal pulled while being rotated and forming a constricted portion, and engaging the constricted portion of the single crystal via a gripping member. A holding jig to be gripped, and a holding jig pulling means for raising the holding jig in synchronization with the pulling speed of the single crystal pulling means after engaging and gripping the constricted portion of the single crystal with the gripping member A single crystal pulling apparatus comprising: 2. The holding jig is a plate-like holding member, and when the portion for increasing the diameter of the single crystal passes through the inside of the plurality of holding members from below to above, the holding member opens upward. And a gripping member for engaging and gripping the constricted portion of the single crystal when the portion for reducing the diameter of the single crystal passes upward from below. Item 1. The single crystal pulling apparatus according to Item 1. 3. A conical engagement surface at the center where the plurality of gripping members engage so that the outer periphery of the constricted portion of the single crystal can be uniformly engaged and gripped when the plurality of gripping members engage. The single crystal pulling apparatus according to claim 1 or 2, further comprising: